Question 59. Design solutions for long-span systems. Loads acting on long-span structures. Layout of frames for long-span coverings

The frames of long-span roofs with beam and frame load-bearing systems have a layout scheme close to the frames of industrial buildings. For large spans and the absence of crane beams, it is advisable to increase the distances between the main load-bearing structures to 12-18 m. The systems of vertical and horizontal connections have the same purposes as in industrial buildings and are arranged in a similar way.

The layout of frame coverings can be transverse when load-bearing frames are placed across the building, and longitudinal, typical for hangars. With a longitudinal layout, the main supporting frame is placed in the direction of the larger dimension of the building plan and the transverse trusses rest on it.

The upper and lower chords of the supporting frames and transverse trusses are untied with cross braces, ensuring their stability.

In arched systems, the pitch of the arches is 12 m or more; The main purlins are laid along the arches, on which the transverse ribs supporting the roof deck rest.

For large spans and heights of the main load-bearing systems (frames, arches), spatially stable block structures are used by pairing adjacent flat frames or arches (Fig. 8), as well as by using triangular sections of arches. The arches are connected in the key by longitudinal connections, the importance of which for the rigidity of the structure is especially great when the lifting boom of the arches is large, when their overall deformability increases.

The transverse braces located between the outer pair of arches are calculated on the wind pressure transmitted from the end wall of the arched covering.

QUESTION 60. Long-span beam structures. Their advantages and disadvantages. Constructive decisions. Loads acting on beam structures. Fundamentals of calculation and design of beam structures.

Beam structures

Long-span beam structures are used in cases where supports cannot withstand thrust forces.

Beam systems for large spans are heavier than frame or arch systems, but are easier to manufacture and install.

Beam systems are used mainly in public buildings - theaters, concert halls, sports facilities.

The main load-bearing elements of beam systems used for spans of 50-70 m or more are trusses; Solid beams with large spans are unprofitable in terms of metal consumption.

Main advantages beam structures are clear in operation, lack of thrust forces and insensitivity to support settlements. Main disadvantage– relatively high consumption of steel and high height, caused by large flying moments and rigidity requirements.

Rice. 1, 2, 3

The cross-sections of the rods of long-span trusses with forces in the rods exceeding 4000-5000 kN are usually taken to be composite of welded I-beams or rolled sections.

The high height of the trusses does not allow them to be transported by rail in the form of assembled shipping elements, so they are supplied for installation in bulk and consolidated on site.

The elements are connected by welding or high-strength bolts. High-precision bolts and rivets should not be used because they are labor intensive.

Long-span trusses are calculated and their sections are selected in the same way as light trusses of industrial buildings.

Due to large support reactions, it becomes necessary to transmit them strictly along the axis of the truss unit, otherwise significant additional stresses may arise.

For spans of 60-90m, the mutual displacement of the supports becomes significant due to the deflection of the truss and its temperature deformations. In this case, one of the supports can be a roller (Fig. 6), allowing free horizontal movements.

If the trusses are installed on high flexible columns, then even with spans of up to 90 m, both supports can be stationary due to the flexibility of the upper parts of the columns.

Long-span beam systems can consist of triangular trusses with prestressing, which are convenient to manufacture, transport and install (Fig. 7).

The inclusion of a reinforced concrete slab laid along the upper chords of the truss in joint compression work, the use of tubular rods and prestressing make such trusses economical in terms of metal consumption.

Steel sheets are included in the design sections of the upper and lower chords of the trusses.

In order for a thin sheet to work under compression, a preliminary tensile stress is created in it that is greater than the compressive stress from the load.

QUESTION 61. Frame long-span structures. Their advantages and disadvantages. Constructive decisions. Loads acting on frame structures. Fundamentals of calculation and design of frame structures.

Frame structures

Frames spanning large spans can be double-hinged or hingeless.

Hingeless frames are more rigid, more economical in metal consumption and more convenient to install; however, they require more massive foundations with dense bases for them and are more sensitive to temperature influences and uneven settlements of the supports.

Frame structures, compared to beam structures, are more economical in terms of metal consumption and are more rigid, due to which the height of the frame crossbar is lower than the height of beam trusses.

In long-span coverings, both continuous and through frames are used.

Solid frames are rarely used for small spans (50-60 m), their advantages: less labor intensity, transportability and the ability to reduce the height of the room.

The most commonly used frames are hinged frames. It is recommended to take the height of the frame crossbar equal to: with through trusses 1/12-1/18 of the span, with solid crossbars 1/20 - 1/30 of the span.

Frames are calculated using structural mechanics methods. To simplify the calculations, lightweight through frames can be reduced to their equivalent solid frames.

Heavy through frames (such as heavy trusses) must be designed as lattice systems, taking into account the deformation of all lattice rods.

For large spans (more than 50 m) and low rigid posts, it is necessary to calculate the frames for temperature effects.

Crossbars and racks of solid frames have solid I-sections; their load-bearing capacity is checked using formulas for eccentrically compressed rods.

In order to simplify the calculation of lattice frames, their expansion can be determined as for a solid frame.

Using an approximate calculation, preliminary sections of the frame chords are established;

determine the moments of inertia of cross-sections of crossbars and racks using approximate formulas;

calculate the frame using structural mechanics methods; the design diagram of the frame should be taken along the geometric axes;

Having determined the support reactions, the calculated forces in all the rods are found, according to which their sections are finally selected.

The types of sections, design of nodes and connections of frame trusses are the same as for heavy trusses of beam structures.

Another artificial method of unloading the crossbar is the displacement of the supporting hinges in the double-hinged frame from the axis of the rack inward. In this case, vertical support reactions create additional moments that unload the crossbar.

Long-span roofing structures for civil and industrial buildings

Saint Petersburg

building covering beam dome

Introduction

Historical reference

Classification

Planar long-span coating structures

Spatial long-span coating structures

1 Folds

3 Shells

Hanging (cable-stayed) structures

1 Hanging covers

4 Combined systems

Transformable and pneumatic coverings

1 Transformable coverings

Used Books

Introduction

When designing and constructing buildings with indoor spaces, a complex of complex architectural and engineering problems arise. For creating comfortable conditions in the hall, meeting the requirements of technology, acoustics, isolating it from other rooms and the environment, the design of the hall covering becomes of decisive importance. Knowledge of the mathematical laws of shape formation made it possible to make complex geometric constructions (parabolas, hyperbolas, etc.), using the principle of an arbitrary plan.

In modern architecture, the formation of a plan is the result of the development of two trends: a free plan, leading to a structural frame system, and a free plan, requiring a structural system that allows organizing the entire volume of the building, and not just the planning structure.

The hall is the main compositional core of most public buildings. The most common plan configurations are rectangle, circle, square, ellipsoidal and horseshoe-shaped plans, less often trapezoidal. When choosing hall covering designs, the need to connect the hall with the outside world through open glazed surfaces or, conversely, to completely isolate it is crucial.

The space, freed from supports and covered with a long-span structure, gives the building emotional and plastic expressiveness.

1. Historical background

Long-span roofing structures appeared in ancient times. These were stone domes and vaults, wooden rafters. For example, the stone dome of the Pantheon in Rome (1125) had a diameter of about 44 m, the dome of the Hagia Sophia Mosque in Istanbul (537) - 32 m, the dome of the Florence Cathedral (1436) - 42 m, the dome Upper Council in the Kremlin (1787) - 22.5 m.

The construction technology of that time did not allow the construction of light structures in stone. Therefore, long-span stone structures were very massive, and the structures themselves were erected over many decades.

Wooden building structures were cheaper and easier to construct than stone ones, and also made it possible to cover large spans. An example is the wooden roof structures of the former Manege building in Moscow (1812), with a span of 30 m.

Development of ferrous metallurgy in the XVIII - XIX centuries. gave builders materials stronger than stone, wood - cast iron and steel.

In the second half of the 19th century. Long-span metal structures are widely used.

IN late XVIII V. A new material has appeared for long-span buildings - reinforced concrete. Improvement of reinforced concrete structures in the 20th century. led to the emergence of thin-walled spatial structures: shells, folds, domes. A theory of calculation and design of thin-walled coatings has emerged, in which domestic scientists also took part.

In the second half of the 20th century. Suspended coverings, as well as pneumatic and rod systems, are widely used.

The use of long-span structures makes it possible to make maximum use of the load-bearing qualities of the material and thereby obtain lightweight and economical coatings. Reducing the weight of structures and structures is one of the main trends in construction. Reducing mass means reducing the volume of material, its extraction, processing, transportation and installation. Therefore, it is quite natural that builders and architects are interested in new forms of structures, which have a particularly great effect in coatings.

2. Classification

Long-span pavement structures can be divided according to their static operation into two main groups of long-span pavement systems:

· planar (beams, trusses, frames, arches);

· spatial (shells, folds, hanging systems, cross-rod systems, etc.).

Beam, frame and arched, flat systems of long-span coverings are usually designed without taking into account the joint work of all load-bearing elements, since individual flat disks are connected to each other by relatively weak connections that are not capable of significantly distributing the loads. This circumstance naturally leads to an increase in the mass of structures.

To redistribute loads and reduce the mass of spatial structures, connections are required.

According to the material used for the manufacture of long-span structures, they are divided into:

wooden

metal

·reinforced concrete

Ø The wood has good load-bearing properties (the calculated resistance of pine to compression and bending is 130-150 kg/m 2) and low volumetric mass (for air-dried pine 500 kg/m3 ).

There is an opinion that wooden structures are short-lived. Indeed, if poorly cared for, wooden structures can very quickly fail due to damage to the wood by various fungi and insects. The basic rule for preserving wooden structures is to create conditions for their ventilation or airing. It is also important to ensure that the wood is dried before using it in construction. Currently, the woodworking industry can provide effective drying using modern methods, including high-frequency currents, etc.

Improving the biological resistance of wood is easily achieved using long-developed and mastered methods of impregnating it with various effective antiseptics.

Even more often, objections to the use of wood arise for reasons fire safety.

However, compliance with basic fire safety rules and supervision of structures, as well as the use of fire retardants that increase the fire resistance of wood, can significantly increase the fire-fighting properties of wood.

As an example of the durability of wooden structures, one can cite the already mentioned Manezh in Moscow, which is more than 180 years old, the spire in the Admiralty in Leningrad with a height of about 72 m, built in 1738, the watchtower in Yakutsk, built about 300 years ago, many wooden churches in Vladimir, Suzdal, Kizhi and other cities and villages of Northern Russia, dating back several centuries.

Ø Metal structures, mainly steel, are widely used.

Their advantages: high strength, relatively low weight. The disadvantage of steel structures is susceptibility to corrosion and low fire resistance (loss of load-bearing capacity at high temperatures). There are many means to combat corrosion of steel structures: painting, coating with polymer films, etc. For fire safety purposes, critical steel structures can be concreted or heat-resistant concrete mixtures (vermiculite, etc.) can be sprayed onto the surface of steel structures.

Ø Reinforced concrete structures are not subject to rotting, rusting, and have high fire resistance, but they are heavy.

Therefore, when choosing a material for long-span structures, it is necessary to give preference to the material that, under specific construction conditions the best way meets the task.

3. Planar long-span coating structures

In public buildings of mass construction, predominantly traditional flat structures are used to cover indoor spaces: decks, beams, trusses, frames, arches. The operation of these structures is based on the use of internal physical and mechanical properties material and transfer of forces in the body of the structure directly to the supports. In construction, the planar type of coatings has been well studied and mastered in production. Many of them with a span of up to 36 m are designed as prefabricated standard structures. There is constant work to improve them, reduce weight and material consumption.

The flat structure of the hall covering in the interiors of public buildings is almost always, due to its low aesthetic qualities, covered with an expensive suspended ceiling. This creates excess spaces and volumes in the building in the area of ​​the roof structure, which in rare cases are used for technological equipment. In the exterior of a building, such structures, due to their inexpressiveness, are usually hidden behind high parapet walls.

Beams are made of steel profiles, reinforced concrete (prefabricated and monolithic), wooden (glued or nailed).

Steel beams of T-section or box section (Fig. 1, a, b) require a large consumption of metal, have a large deflection, which is usually compensated by the construction lift (1/40-1/50 of the span).

An example is the indoor artificial skating rink in Geneva, built in 1958 (Fig. 1, c). Hall covering dimensions 80.4 × 93.6 m is made of ten integrally welded solid steel beams of variable cross-section, installed every 10.4 m. By installing a console with a guy at one end of the beam, a pre-tension is created, which helps reduce the cross-section of the beam.

Reinforced concrete beams have a large bending moment and a large dead weight, but are easy to manufacture. They can be made monolithic, prefabricated monolithic and prefabricated (from separate blocks and solid). They are made of reinforced concrete with prestressing reinforcement. The ratio of beam height to span ranges from 1/8 to 1/20. In construction practice, there are beams with a span of up to 60 m, and with consoles - up to 100 m. The cross-section of the beams is in the form of a T-beam, I-beam or box-shaped (Fig. 2, a, b, c, d, e, g).

a - steel beam of I-section (composite);

b - box-section steel beam (composite);

c - artificial indoor skating rink in Geneva (1958). The covering measures 80.4 × 93.6 m.

The main beams of I-section are located every 10.4 m.

Aluminum purlins are laid along the main beams.

Rice. 1 (continued)

d - diagrams of unified horizontal trusses

with parallel belts. Developed by TsNIIEP spectacular and

sports facilities;

d - diagrams of gable steel trusses: polygonal and triangular

g - congress hall in Essen (Germany). Coverage dimensions 80.4 × 72.0.

The covering rests on 4 lattice posts. The main trusses have a span of 72.01 m, the secondary ones - 80.4 m with a pitch of 12 m

Rice. 2. Reinforced concrete beams and trusses

a - reinforced concrete single-pitch beam with parallel chords

T-section;

b - reinforced concrete gable beam of I-section;

c - horizontal reinforced concrete beam with parallel chords

I-section;

g - composite reinforced concrete horizontal beam with parallel and

T-section belts;

d - reinforced concrete horizontal beam of box section

Rice. 2 (continued)

e - composite gable reinforced concrete truss, consisting of

two half-trusses with a pre-stressed bottom chord;

g - the building of the British Overseas Aviation Company (BOAC) in London 1955. The reinforced concrete beam has a height of 5.45 m, the cross-section of the beam is rectangular;

z - gymnasium of a high school in Springfield (USA)

In the practice of mass construction in our country, the beams shown in Fig. are widely used. 2, a, b, c.

Wooden beams are used in areas rich in forests. They are typically used in Class III buildings due to their low fire resistance and durability.

Wooden beams are divided into nailed and glued beams up to 30-20 m long. Nail beams (Fig. 3, a) have a wall sewn on nails from two layers of boards, inclined in different directions at an angle of 45°. The upper and lower chords are formed by longitudinal and transverse beams sewn on both sides of the vertical walls. The height of the nail beams is 1/6-1/8 of the beam span. Instead of a plank wall, you can use a wall made of multilayer plywood.

Glued beams, unlike nail beams, have high strength and increased fire resistance even without special impregnation. The cross-section of laminated wooden beams can be rectangular, I-beam, or box-shaped. They are made from slats or boards with glue, laid flat or on edge.

The height of such beams is 1/10-1/12 of the span. According to the outline of the upper and lower chords, laminated beams can be with horizontal chords, single- or double-slope, curved (Fig. 3, b).

Rice. 3 (continued)

Trusses, like beams, can be made of metal, reinforced concrete and wood. Steel trusses, unlike metal beams, require less metal due to their lattice structure. With a suspended ceiling, a walk-through attic is created, allowing passage of utilities or free passage through the attic. Trusses are usually made from steel profiles, and spatial triangular trusses are made from steel pipes.

The Congress and Sports Hall in Essen has a covering size of 80.4 × 72 m (Fig. 1, g). The covering rests on four lattice pillars consisting of four branches. One of the racks is rigidly fixed to the foundation, two racks have roller bearings, the fourth rack is made swinging and can move in two directions. The two main polygonal riveted trusses rest on support posts and have a span of 72 m and a height of 5.94 and 6.63 m in the middle of the span and, respectively, 2.40 and 2.54 m at the supports. The chords of the main trusses have a box section with a width of more than 600 mm, the braces are composite, I-section. Double-cantilever, welded secondary trusses with a span of 80.4 m rest on the main trusses with a pitch of 12 m. The upper chord of these trusses has a cross-section in the form of a T-beam, the lower - in the form of an I-beam with wide flanges. To ensure free vertical deformations at a distance of 11 m from the edges of the roof, through hinges are installed both in the enclosing structure of the covering, and in the trusses and in the suspended ceiling. The ends of the 11 m long trusses rest on light swinging posts located in the stands. Cross wind horizontal ties are located between the main and between the outermost secondary trusses, as well as along the longitudinal walls at a distance of 3.5 m from the edge of the covering. The purlins and sheathing are made of I-beams. The building is covered with 48 mm thick compressed straw slabs, on which a waterproofing carpet of four layers of hot bitumen on fiberglass is laid.

Trusses can have different outlines of both the upper and lower chords. The most common trusses are triangular and polygonal, as well as horizontal ones with parallel belts (Fig. 1, d, e, g).

Reinforced concrete trusses are manufactured: solid - up to 30 m long; composite - with prestressing reinforcement, with a length of more than 30 m. The ratio of the height of the truss to the span is 1/6-1/9.

The lower belt is usually horizontal, the upper belt can have a horizontal, triangular, segment or polygonal outline. The most widespread are reinforced concrete polygonal (gable) trusses, shown in Fig. 2, f. Maximum length designed reinforced concrete trusses is about 100 m at a step of 12 m.

The disadvantage of reinforced concrete trusses is their large structural height. To reduce the dead weight of trusses, it is necessary to use high-strength concrete and introduce lightweight covering slabs made of efficient materials.

Wooden trusses - can be presented in the form of log or timber hanging rafters. Wooden trusses are used for spans of more than 18 m and subject to preventive fire safety measures. The upper (compressed) chord and braces of wooden trusses are made from square or rectangular beams with a side equal to 1/50-1/80 of the span, the lower (stretched) chord and suspensions are made from both beams and steel strands with screw threads at the ends to tension them using nuts with washers.

The stability of wooden trusses is ensured by wooden braces and ties installed along the edges and in the middle of the truss perpendicular to their plane, as well as roofing decks that form a hard disk of the covering. In domestic construction practice, trusses with a span of 15, 18, 21 and 24 m are used, the upper chord of which is made from a continuous package of boards 170 mm wide using FR-12 glue. The braces are made of bars of the same width, the lower belt is made of rolled angles, and the suspension is made of round steel (Figure 3, c).

Metal-wood trusses - were developed by TsNIIEP educational buildings, TsNIIEP entertainment buildings and sports facilities and TsNIISK Gosstroy of the USSR in 1973. These trusses are installed at intervals of 3 and 6 m and can be used for roofing in two versions:

a) with a warm exploitable suspended ceiling and cold roofing panels;

b) without suspended ceiling and warm roofing panels.

Frames are planar spacer structures. Unlike a non-thrust beam-post structure, the crossbar and the post in the frame structure have a rigid connection, which causes bending moments to appear in the post due to the impact of loads on the frame crossbar.

Frame structures are made with rigid embedding of supports into the foundation, if there is no danger of uneven settlement of the foundation. The special sensitivity of frame and arched structures to uneven settlements leads to the need for hinged frames (two-hinged and three-hinged). Schemes of arches in Fig. 4, a, b, c, d.

Considering that the frames do not have sufficient rigidity in their plane, when constructing the covering it is necessary to ensure the longitudinal rigidity of the entire covering by embedding the covering elements or installing diaphragm frames normal to the plane, or stiffening links.

Frames can be made of metal, reinforced concrete or wood.

Metal frames can be made of either solid or lattice sections. The lattice section is typical for frames with large spans, as it is more economical due to its low dead weight and the ability to withstand both compressive and tensile forces equally well. The cross-sectional height of the cross-sections of lattice frames is taken to be within 1/20-1/25 of the span, and of solid-section frames 1/25-/30 of the span. To reduce the height of the cross-section of the cross-section of both solid and lattice metal frames, unloading consoles are used, sometimes equipped with special guys (Fig. 4, d).

Frames: a - hingeless; b - double-hinged; c - three-hinged; g - double-hinged;

d - hingeless; e - two hinged; g - three-hinged; and - double-hinged with unloading consoles; k - double-hinged with a tightening that absorbs thrust; h - frame height; I - arch lifting boom; l - span; r1 and r2 - radii of curvature of the lower and upper edges of the arch; 0.01 and 02 centers of curvature; - hinges; s - tightening; d - vertical loads on the console.

Metal frames are actively used in construction (Fig. 5, 1, a, b, c, d, e; Fig. 6, a, c).

Steel, reinforced concrete and wooden frames

Reinforced concrete frames can be hingeless, double-hinged, or less often triple-hinged.

For frame spans of up to 30-40 m, they are made of a solid, I-section with stiffeners; for large spans, they are made of lattice. The height of a solid section crossbar is about 1/20-1/25 of the frame span, of a lattice section 1/12-1/15 of the span. Frames can be single-span or multi-span, monolithic or prefabricated. In a prefabricated solution, it is advisable to connect individual frame elements in places with minimal bending moments. In Fig. 5, 2, i, j, and Fig. e 6, c provide examples from the practice of constructing buildings using reinforced concrete frames.

Wooden frames, like wooden beams, are made of nailed or glued elements for spans of up to 24 m. It is advantageous to make them three-hinged to facilitate installation. The height of the crossbar from nail frames is taken to be about 1/12 of the frame span, for glued frames - 1/15 of the span. Examples of building construction using wooden frames are shown in Fig. 5, l, m, fig. 7.

Rice. 7 Frame of a warehouse building with wooden glued plywood frames

Arches, like frames, are planar spacer structures. They are even more sensitive to uneven precipitation than frames and are made as hingeless, double-hinged or three-hinged (Fig. 4, e, f, g, i, j). The stability of the coating is ensured by the rigid elements of the enclosing part of the coating. For spans of 24-36 m it is possible to use three-hinged arches consisting of two segment trusses(Fig. 8, a). To avoid sagging, hangers are installed.

a - three-hinged wooden arch made of polygonal trusses;

b - lattice wooden arch

Metal arches are made of solid and lattice sections. The height of the crossbar of a solid section of arches is used within 1/50-1/80, of a lattice span 1/30-1/60. The ratio of the lifting boom to the span for all arches is in the range of 1/2-1/4 for a parabolic curve and 1/4-1/8 for a circular curve. In Fig. 8, a, fig. 9, fig. 1, fig. 10, a, b, c, examples from construction practice are presented.

Reinforced concrete arches, like metal arches, can have a solid or lattice cross-section of the crossbar.

The structural height of the cross-section of the crossbar of solid arches is 1/30-1/40 of the span, of lattice arches 1/25-1/30 of the span.

Prefabricated arches of large spans are made in composite form, from two semi-arches, concreted in Fig. e in a horizontal position, and then raised to the design position (example in Fig. 9, 2, a, b, c).

Wooden arches are made from nailed and glued elements. The ratio of the lifting boom to the span for nailed arches is 1/15-1/20, for glued ones - 1/20-1/25 (Fig. 8, a, b, Fig. 10, c, d).

a - arch with tightening on columns; b - supporting the arch on the frames; or buttresses; c - supporting the arch on the foundations

4. Spatial long-span coating structures

Long-span structural systems from different eras share a number of significant features, which makes it possible to consider them as technical progress in construction. The dream of builders and architects is connected with them, to conquer space, to cover the largest possible area. What unites historical and modern curvilinear structures is the search for appropriate shapes, the desire to minimize their weight, the search for optimal load distribution conditions, which leads to the discovery of new materials and potential possibilities.

Spatial long-span covering structures include flat folded coverings, vaults, shells, domes, cross-ribbed coverings, rod structures, pneumatic and awning structures.

Flat folded coverings, shells, cross-ribbed coverings and rod structures are made of rigid materials (reinforced concrete, metal profiles, wood, etc.) Due to the joint work of structures, spatial rigid coverings have a small mass, which reduces the cost of both covering construction and for the installation of supports and foundations.

Hanging (cable-stayed), pneumatic and awning coverings are made of non-rigid materials (metal cables, metal rice membranes, membranes made of synthetic films and fabrics). They, to a much greater extent than spatial rigid structures, ensure a reduction in the volumetric mass of structures and allow for the rapid construction of structures.

Spatial structures make it possible to create a wide variety of forms of buildings and structures. However, the construction of spatial structures requires a more complex organization of construction production and High Quality all construction work.

Of course, recommendations on the use of certain coating designs for each specific case can't be given. The coating as a complex subsystem formation is located in the structure of the structure in close connection with all its other elements, with external and internal environmental influences, with the economic, technical, artistic and aesthetic-style conditions of its formation. But some experience in the use of spatial structures and the results that it gave can help in understanding the place of a particular constructive and technological organization of public buildings. Spatial type structural systems already known in world construction practice make it possible to cover buildings and structures with almost any plan configuration.

1 Folds

A fold is a spatial covering formed by flat mutually intersecting elements. Folds consist of a number of elements repeated in a certain order, supported along the edges and in the span by stiffening diaphragms.

The folds are sawtooth, trapezoidal, made of the same type of triangular planes, tent-shaped (quadrangular and polyhedral) and others (Fig. 11, a, b, c, d).

Folded structures used in cylindrical shells and domes are discussed in the appropriate sections.

The folds can be extended beyond the outer supports, forming cantilever overhangs. The thickness of the flat fold element is taken to be about 1/200 of the span, the height of the element is at least 1/10, and the width of the edge is at least 1/5 of the span. Folds usually cover spans up to 50-60 m, and tents up to 24 m.

Folded structures have a number of positive qualities:

simplicity of form and, accordingly, ease of their manufacture;

Great possibilities for factory prefabrication;

saving room height, etc.

An interesting example of the use of a flat folded structure of a sawtooth profile is the covering of the laboratory of the Concrete Institute in Detroit (USA) of size 29.1 × 11.4 ( Fig. 11, e) project by architects Yamasaki and Leinweber, engineers Amman and Whitney. The covering rests on two longitudinal rows of supports, forming a middle corridor and has cantilever extensions on both sides of the supports, 5.8 m long. The covering is a combination of folds directed in opposite directions. The thickness of the folds is 9.5 cm.

In 1972, during the reconstruction of the Kursky railway station in Moscow, a trapezoidal folded structure was used, which made it possible to cover a waiting room measuring 33 × 200 m (Fig. 11, f).

The most ancient and widespread system of curvilinear covering is the vaulted covering. The vault is a structural system on the basis of which a number of architectural forms of the past (up to the twentieth century) were created, which made it possible to solve the problem of covering various halls with different functional purpose.

Cylindrical and closed vaults are the simplest forms of vault, but the space formed by these coverings is closed, and the form is devoid of plasticity. By introducing formwork into the designs of the trays of these vaults, a visual feeling of lightness is achieved. The inner surface of the vaults, as a rule, was decorated with rich decoration or imitated by a false structure of a wooden suspended ceiling.

A cross vault is formed by cutting from the intersection of two barrel vaults. They were blocked by huge halls of baths and basilicas. The cross vault was widely used in Gothic architecture.

Cross vault is one of the common forms of covering in Russian stone architecture.

Varieties of vaults such as sail vaults, domed vaults, and canopies were widely used.

3 Shells

Thin-walled shells are one of the types of spatial structures and are used in the construction of buildings and structures with large areas (hangars, stadiums, markets, etc.). A thin-walled shell is a curved surface, which, with minimal thickness and, accordingly, minimal mass and material consumption, has a very high load-bearing capacity, because thanks to its curved shape it acts as a spatial load-bearing structure.

A simple experiment with rice paper shows that a very thin curved plate, due to its curvilinear shape, acquires greater resistance to external forces than the same plate of a flat shape.

Rigid shells can be erected over buildings of any configuration in plan: rectangular, square, round, oval, etc.

Even very complex structures can be divided into a number of similar elements. At construction parts factories, separate technological lines are created for the manufacture of individual structural elements. The developed installation methods make it possible to erect shells and domes using inventory support towers or without auxiliary scaffolding at all, which significantly reduces the construction time of coverings and reduces the cost of installation work.

According to their design schemes, rigid shells are divided into: shells of positive and negative curvature, umbrella shells, vaults and domes.

Shells are made of reinforced concrete, reinforced cement, metal, wood, plastics and other materials that can withstand compressive forces well.

In conventional load-bearing systems, which we discussed earlier, the resistance to emerging forces is concentrated continuously along their entire curved surface, i.e. since this is characteristic of spatial load-bearing systems.

The first reinforced concrete shell dome was built in 1925 in Jena. Its diameter was 40m, this is equal to the diameter of the dome of St. Peter's in Rome. The mass of this shell turned out to be 30 times less than the dome of St. Petra. This is the first example that showed the promising capabilities of the new constructive principle.

The advent of stress-reinforced concrete, the creation of new calculation methods, the measurement and testing of structures using models, along with the static and economic benefits of their use, all contributed to the rapid spread of shells throughout the world.

Shells have a number of other advantages:

in the coating they simultaneously perform two functions: load-bearing structure and roof;

they are fire resistant, which in many cases puts them in a more advantageous position even with equal economic conditions;

they have no equal in the variety and originality of forms in the history of architecture;

finally, in comparison with previous vaulted and dome structures, they surpassed them many times in terms of the spans covered.

If the construction of shells in reinforced concrete has become quite widely developed, then in metal and wood these structures still have limited use, since sufficiently simple structural forms of shells characteristic of metal and wood have not yet been found.

Shells in metal can be made of all-metal, where the shell simultaneously performs the functions of a load-bearing and enclosing structure in one, two or more layers. With appropriate development, the construction of shells can be reduced to the industrial assembly of large panels.

Single-layer metal shells are made of steel or aluminum rice.a. To increase the rigidity of the shells, transverse ribs are introduced. With a frequent arrangement of transverse ribs connected to each other along the upper and lower belts, a two-layer shell can be obtained.

Shells come in single and double curvature.

Shells of single curvature include shells with cylindrical or conical surface(Fig. 12, a, b).

Rice. 12. The most common forms of shells

a - cylinder: 1 - circle, parabola, sinusoid, ellipse (guides); 2 - straight line (generative); b - cone: 1 - any curve; 2 - straight line (generative); d - transfer surface: 1 - parabola (guide); 2 - ellipse, circle (generative); c - surface of rotation (dome): 1-rotation; 2 - circle, ellipse, parabola (generative); Surface of rotation or transfer (spherical shell): 1, 2 - circle, parabola (generators or guides); 3 - circle, parabola (generative); 4 - axis of rotation d - formation of shells of double curvature in one direction: hyperbolic paraboloid: AB-SD, AC-VD - straight lines (guides); 1 - parabola (guide).

Cylindrical shells have a circular, elliptical or parabolic shape and are supported by end stiffening diaphragms, which can be made in the form of walls, trusses, arches or frames. Depending on the length of the shells, they are divided into short ones, in which the span along the longitudinal axis is no more than one and a half wavelengths (span in the transverse direction), and long ones, in which the span along the longitudinal axis is more than one and a half wavelengths (Fig. 13, a , c, d).

Along the longitudinal edges of long cylindrical shells, side elements (stiffening ribs) are provided, in which longitudinal reinforcement is placed, allowing the shell to operate along the longitudinal span like a beam. In addition, the side elements absorb the thrust from the work of the shells in the transverse direction and therefore must have sufficient rigidity in the horizontal direction (Fig. 13, a, e).

The wavelength of a long cylindrical shell usually does not exceed 12 m. The ratio of the lifting boom to the wavelength is taken to be at least 1/7 of the span, and the ratio of the lifting boom to the span length is not less than 1/10.

Prefabricated long cylindrical shells are usually divided into cylindrical sections, side elements and a stiffening diaphragm, the reinforcement of which is welded together and monolied during installation (Fig. 13, e).

It is advisable to use long cylindrical shells for covering large rooms with a rectangular plan. Long shells are usually placed parallel to the short side of the overlapped rectangular space to reduce the span of the shells along the longitudinal axis (Fig. 13, e). The development of long cylindrical shells follows the line of searching for the flattest possible arc with a small lifting boom, which leads to easier conditions for construction work, a reduction in the volume of the building and improved operating conditions.

Particularly advantageous, in terms of structural work, is the arrangement of a sequential row of flat cylindrical shells, since in this case the bending forces acting in the horizontal direction are absorbed by adjacent shells (except for the outer ones).

Let us give examples of the use of long cylindrical shells in construction.

The multi-wavelength long cylindrical shell was made in a garage in Bournemouth (England).

Shell sizes 4 5×90 m, thickness 6.3 cm, the project was carried out by engineer Morgan (Fig. 14, a).

c - hangar of the airfield in Karachi (Pakistan, 1944). The coating is formed by long cylindrical shells 39.6 m long, 10.67 m wide and 62.5 mm thick. The shells rest on a 58 m long purlin, which is a lintel over the hangar gate; g - hangar of the Ministry of Aviation in the Academy of Sciences! lip (1959). To cover the hangar, three cylindrical shells were used, located parallel to the hangar door opening. The length of the shells is 55 m. The depth of the hangar is 32.5 m. The beams that absorb the thrust have a box-shaped section

The covering of the sports hall in Madrid (1935) was designed by the architect Zuazo and the engineer Torroja. The covering is a combination of two long cylindrical shells resting on the end walls and does not require support on the longitudinal walls, which for this reason are made of lightweight materials. Shell length 35 m, span 32.6 m, thickness 8.5 cm (Fig. 14, b).

The airfield hangar in Karachi, built in 1944, is represented by shells whose length is 29.6 m, width 10.67 m and thickness 6.25 cm. The shells rest on a girder with a span of 58 m, which is a lintel over the hangar gate (Fig. 14 , V).

The use of long cylindrical shells is practically limited to spans up to 50 m, since beyond this limit the height of the side elements (rand beams) turns out to be excessively large.

Such shells are often used in industrial construction, but are also used in public buildings. Kaliningradgrazhdanproekt has developed long cylindrical shells with spans of 18 × 24 m, 3 m wide. They are manufactured immediately for the span together with insulation - fibreboard. A layer of waterproofing is applied on top of the finished element at the factory.

Long cylindrical shells are made of reinforced concrete, reinforced cement, steel and aluminum alloys.

Thus, to cover the Moscow railway station in St. Petersburg, a cylindrical shell made of rice aluminum was used. The length of the temperature block is 48 m, width 9 m. The coating is suspended from reinforced concrete supports installed at the inter-track.

Short cylindrical shells, compared to long shells, have a larger wave size and lifting boom. The curvature of short cylindrical shells corresponds to the direction of the largest span of the covered room. These shells act as vaults.

The shape of the curve can be represented by a circular arc or a parabola. Due to the danger of buckling in short shells, transverse stiffeners are introduced in most cases. In addition to the side elements, such shells must have tightening to absorb horizontal transverse forces (Fig. 13, c, e).

Short cylindrical shells for buildings with a grid of columns 24 are widely known × 12 m and 18 × 12 m. They consist of diaphragm trusses, ribbed panels 3 × 12 m and side elements (Fig. 15, a-d).

The structures for the specified spans are recognized as standard.

The use of short cylindrical shells does not require the use of a suspended ceiling.

Conical shells are usually used for roofing trapezoidal buildings or premises. Design features these shells are the same as long cylindrical shells (Fig. 12, a). An example of an interesting use of this form is the covering of a restaurant on the shore of a lake in Georgia (USA), made in the form of a series of reinforced concrete mushroom-shaped cones with a diameter of 9.14 m. The hollow stems of the mushrooms are used to drain rainwater from the surface of the covering. The triangles formed by the edges of three touching mushrooms were covered with reinforced concrete slabs with round holes for skylights in the form of plastic domes.

Rice. 15 Examples of the use of short cylindrical shells made in reinforced concrete

In undulating and folded shells with long spans, significant bending moments occur due to temporary loads from wind, snow, temperature changes, etc.

The necessary reinforcement of such shells was achieved by constructing ribs. A reduction in effort was achieved by switching to wavy and folded profiles of the shell itself. This made it possible to increase the rigidity of the shells and reduce material consumption.

Such designs make it possible to emphasize the contrast between the plane of the enclosing wall, which can be independent of the load-bearing supports, and the covering resting on it. This makes it possible to make large cantilever overhangs in these structures for installing supports, etc. (Kursky railway station in Moscow).

Folds and waves are an interesting plate shape for ceilings and sometimes for walls in interiors.

A wavy shell, when the scale, curvature, and shape are found for it, based on the requirements of architectural aesthetics, can be quite expressive. This type of structure is designed for spans of more than 100 m, which have been applied to cover a wide variety of objects.

Polyhedral folded shell vaults are an example of increasing the rigidity of a cylindrical shell by imparting a polyhedral shape.

The transition from single-curvature shells to double-curvature shells marks a new stage in the development of shells, since the effect of bending forces in them is reduced to a minimum.

Such shells are used in buildings with various plans: square, triangular, rectangular, etc.

A variety of such shells on a round or oval plan is a dome.

Shells of double curvature can be made with both ruffled and flat contours.

Their disadvantages include: an inflated volume of the building being covered, a large roof surface, and not always favorable acoustic characteristics. In the coating it is possible to use light lanterns mainly in the center.

Such shells can be made in monolithic and prefabricated monolithic reinforced concrete.

The spans of these buildings vary between 24-30 m. The stability of the shell is ensured by a system of pre-stressed stiffening beams with a mesh of 12 × 12 m. The shell contour rests on a prestressed belt.

In some cases, it is advisable to cover the halls with tent shells in the shape of a truncated pyramid, made of reinforced concrete. They can rest along the contour, on two sides or corners.

The most common types of double-curvature shells in construction practice are shown in Fig. 12, f, g, h.

The dome is a surface of rotation. The forces in it act in the meridional and latitudinal directions. Compressive stresses arise along the meridian. Along the latitudes, starting from the top, compressive forces also arise, gradually turning into tensile forces, which reach their maximum at the lower edge of the dome. Dome shells can rest on a tensile support ring, on columns - through a system of diaphragms or stiffeners, if the shell has a square or polyhedral shape in plan.

The dome originated in the countries of the East and had, first of all, a utilitarian purpose. In the absence of wood, clay and brick domes served as coverings for dwellings. But gradually, thanks to its exceptional aesthetic and tectonic qualities, the dome acquired independent semantic content as an architectural form. The development of the dome's shape is associated with a constant change in the nature of its geometry. From spherical and spherical shapes, builders move on to pointed ones with complex parabolic shapes.

Domes are spherical and multifaceted, ribbed, smooth, corrugated, wavy (Fig. 16, a). Let's look at the most typical examples of dome shells.

Covering the Sports Palace in Rome (1960), built according to the design of Professor P.L. Nervi for Olympic Games, is a spherical dome made of prefabricated reinforced cement elements with a width of 1.67 to 0.34 m, having a complex spatial shape (Fig. 17, a). The 114 segments of the dome rest on 38 inclined supports (3 segments per 1 support). After completing the monolithic structures and embedding the prefabricated segments, the dome structure began to work as a single whole. The building was built in 2.5 months.

The dome roof of the concert hall in Matsuyama (Japan), designed in 1954 by architect Kenzo Tange and engineer Zibon, is a segment of a ball with a diameter of 50 m, a lifting boom of 6.7 m (Fig. 17, b). There are 123 round holes with a diameter of 60 cm in the covering for overhead lighting of the hall.

The thickness of the shell in the middle is 12 cm, at the supports it is 72 cm. The thickened part of the shell replaces the support ring.

The dome over the auditorium of the theater in Novosibirsk (1932) has a diameter of 55.5 m, a lifting boom of 13.6 m. The thickness of the shell is 8 cm (1/685 of the span). It rests on a ring with a cross-section of 50 × 80 cm (Figure 17, c).

The dome of the exhibition pavilion in Belgrade (Yugoslavia) was built in 1957. The diameter of the dome is 97.5 m with a lifting boom of 12-84 m. The dome is a structure consisting of a monolithic central part with a diameter of 27 m, and an annular, hollow, trapezoidal section of a reinforced concrete beam , on which 80 prefabricated reinforced concrete semi-arches of an I-section rest, supported by three rows of annular shells (Figure 17, d).

The dome of the stadium in Oporto (Portugal), built in 1981, has a diameter of 92 m.

The covering is made of 32 meridianally located ribs resting on triangular frames and 8 reinforced concrete rings. The diameter of the dome in the area of ​​its support on the triangular frames is 72 m, the height of the dome is 15 m. The dome shell is made of concrete with cork filler on a reinforced concrete frame.

At the top of the dome there is a light lantern (Fig. 17, e).

In Fig. 18 shows examples of dome-shells made of metal. The experience of constructing such buildings has shown that they are not without drawbacks. So, the main one is the large construction volume of buildings and the excessively large mass of building structures.

IN last years The first domed buildings with retractable roofs appeared.

For example, for the stadium in Pittsburgh (Fig. 18), sector shell elements made of aluminum alloys sliding radially along the surface of the dome were used.

In wooden domes (Fig. 19, a, b, c), the load-bearing structures are sawn or glued wooden elements. In modern flat domes, the main frame elements work in compression, which is why the use of wood is especially advisable.

Since the Middle Ages, wood has been used as a structural material in dome construction. Many wooden domes dating back to the Middle Ages have survived to this day in Western Europe. They often represent an attic covering above the main dome, made of brick. These domes had a powerful system of rigidity connections. Among such domes is, for example, the main dome of the Trinity Church in Leningrad. The dome, with a diameter of 25 m and a lift of 21.31 m, was erected in 1834 and exists to this day. Of the wooden domes of that time, this dome was the largest in the world. It has a typical timber structure consisting of 32 meridional ribs connected by several beams of ring ties.

Rice. 18 Examples of dome-shells made in metal

In 1920-30 In our country, several wooden domes of significant size were erected. Wooden thin-walled domes covered gas tanks with a diameter of 32 m at the Bereznikovsky and Bobrikovsky chemical plants. In Saratov, Ivanovo and Baku, circuses with diameters of 46, 50 and 67 m, respectively, were covered with wooden domes. These domes had a ribbed design, where the ribs were lattice arches (Fig. 19, b).

Modern technology for gluing wood with durable waterproof synthetic adhesives and extensive experience in the production of laminated wood, and its use in construction, have made it possible to introduce wood as a new high-quality material into long-span structures. Wood structures are strong, durable, fire-resistant and economical.

Figure 19. Examples of the use of wooden dome shells

Domes made of laminated wood are used to cover exhibition and concert halls, circuses, stadiums, planetariums and other public buildings. Architectural and structural types of laminated wood domes are very diverse. The most commonly used domes are ribbed domes, domes with a triangular mesh and mesh domes with a crystalline lattice, developed by Professor M.S. Tupolev.

A number of laminated wood domes have been built in the USA and England.

In the state of Montana (USA), a wooden dome with a diameter of 91.5 m with a lifting boom of 15.29 m was erected over the building of a sports center for 15 thousand spectators in 1956 (Fig. 19, c). The supporting frame of the dome consists of 36 meridional ribs with a cross section of 17.5 × 50 cm. The ribs rest on a lower support ring made of rolled profiles and on a compressed upper metal ring. The dome is installed on reinforced concrete columns 12 m high. In each cell, formed by ribs and girders, steel ties are stretched diagonally crosswise. The dome was installed using paired semi-arches along with purlins and ties. Each semi-arch, 45 m long, was assembled on the ground from three parts.

Folded domes are mounted from reinforced cement spatial shells arranged in one or two tiers, or they are made monolithic (Fig. 19, a).

Wave-shaped domes are used for spans of more than 50 m. The surface of the dome is given a wave-like shape to ensure greater rigidity and stability (Fig. 20, a, b).

The covering of the covered market in Royen (France), built according to the design of architects Simon and Moriseo, engineer Sarget in 1955, is a wavy spherical shell of 13 radially arranged sinus-shaped paraboloids (Fig. 20, a). The diameter of the dome is 50 m, height 10.15 m, wave width 6 m, thickness 10.5 cm. The lower edges of the waves rest directly on the foundation.

The covering of the circus in Bucharest (1960), designed by the Project Bucharest Institute, is a wave-shaped dome with a diameter of 60.6 m, consisting of 16 parabolic wave segments (Fig. 20, b). The thickness of the shell is 7 cm at the top, 12 cm at the supports. The dome rests on 16 pillars connected to each other by a polygonal prestressed reinforced concrete belt that absorbs thrust forces in the dome.

Shells with a transfer surface are used to cover rectangular or polygonal premises. Such shells rest on diaphragms on all sides of the polygon. The surface of the transfer shell is formed by the translational movement of one curve along another, provided that both curves are curved upward and are in two mutually perpendicular planes (Fig. 12, f).

Transfer shells (Fig. 12, d) work in the transverse and longitudinal direction like arches.

Powerful ties suspended under the longitudinal ribs absorb thrust in the direction of the flight. In the transverse direction, the thrust from the shell in the outer spans is absorbed by stiffening diaphragms and side elements, and in the middle spans the thrust is absorbed by neighboring shells. The cross sections of the transfer shells along the entire length of the arch, except for the support zones, are often assumed to be circular (Fig. 16, b).

An example of a shell with a transfer surface is the cover of a rubber factory in Brynmawr (South Wales, England), built in 1947 (Fig. 21, b). The coating consists of 9 rectangular elliptical shells measuring 19 ×26 m. The thickness of the shells is 7.5 cm. The rigidity of the shells is ensured by side diaphragms.

In the support zones, the shell can end with conoidal elements that provide a transition from the circular cross-section of the middle zone to a rectangular one along the line of support.

Using this system, a covering over a car garage with a span of 96 m was built in Leningrad, consisting of 12 vaults, each 12 m wide.

Spherical sail shells are formed when the spherical surface is limited by vertical planes built on the sides of a square. The stiffness diaphragms in this case are the same for all four sides (Fig. 12, c, e, Fig. 16).

Prefabricated ribbed spherical shells size 36 × 36 m are used in the construction of many industrial facilities (Fig. 21, e). This solution uses slabs of four standard sizes: in the middle part, square 3 × 3 m, and to the periphery - rhombic shells, close to the size of a square. These slabs have diagonal working ribs and small thickenings along the contour.

The ends of the reinforcement of the diagonal ribs are exposed. During installation, they are welded using overhead rods. Rods with spiral reinforcement placed on them are placed in the seams between the slabs in the area of ​​corner joints. After this, the seams are sealed.

The spherical covering of the building of the Novosibirsk shopping center has dimensions in plan of 102 × 102 m, the rise of the contour arches is equal to 1/10 of the span. The generatrix curve of the shell has the same rise.

The total rise of the shell is 20.4 m. The surface of the shell is cut taking into account the transfer pattern. In corner areas, the covering slabs are located diagonally in order to place stressed reinforcement in longitudinal (diagonal) joints.

The supporting parts of the corner sections of the coating, which experience the greatest stress, are made of monolithic reinforced concrete.

The coverings of the 1200-seat meeting hall at the Massachusetts Institute of Technology in Boston (USA) were designed by architect Ero Saariner. It is a spherical shell with a diameter of 52 m and has a triangle shape in plan.

The spherical shell of the coating is 1/8 of the spherical surface. Along the contour, the shell rests on three curved load-bearing belts, which transmit forces to supports located at three points (Fig. 21, d). Shell thickness from 9 to 61 cm.

Such a large thickness of the shell at the supports is explained by significant bending moments arising in the shell due to large cutouts, which indicates an unsuccessful design solution.

The covering of the shopping center in Canoe (Hawaii Islands, USA) is made in the form of a spherical shell with a smooth surface measuring 39.01 × 39.01 m. The shell does not have a rigidity diaphragm and is supported by its corners on 4 abutments. Shell thickness 76-254 mm. (Fig. 21, a).

The cover (Spain) of the covered market in Algeciros, built in 1935 according to the design of the engineer Torroja and the architect Arcas, is an octagonal spherical shell with a diameter of 47.6 m.

The eight supports on which the shell rests are connected to each other by a polygonal belt that absorbs thrust from the shell (Fig. 21, c).

5 Shells with opposite direction of curvature

Shells with opposite directions of one and the other curvature are formed by moving a straight line (generator) along two guide curves. These include conoids, unisexual hyperboloids of revolution and hyperbolic paraboloids (Fig. 12, f, g, h).

When a conoid is formed, the generatrix rests on a curve and a straight line (Fig. 12, g). The result is a surface with the opposite direction of one curvature. The conoid is used mainly for shed roofs and makes it possible to obtain many different shapes. The direction of the conoid curve can be a parabola or a circular curve. The conoidal shell in the shade coating allows for natural lighting and ventilation of the premises (Fig. 16, d, e).

The supporting elements of conoid shells can be arches, rand beams and other structures.

The span of such shells ranges from 18 to 60 m. Tensile stresses arising in the conoid shell are transferred to rigid diaphragms. The load of the conoid shell is carried by four supports, usually located at the four corner points of the shell.

An example is the reception and storage building of the covered market in Toulouse (France), built according to the design of engineer Prat. The market is covered with a structure consisting of parabolic reinforced concrete arched trusses with a span of 20 m, with a lifting boom of 10 m and conoid shells 70 mm thick, the distance between the arches is 7 m. Loading platforms located along the longitudinal sides of the building are covered with cylindrical shells in the form of consoles 7 m long, held by cables resting on the arches (Fig. 22, a).

The generatrix of a single-sex hyperboloid of revolution wraps around the axis with which it intersects in an inclined position (Fig. 12, h). When this line moves, two systems of generatrices appear, intersecting on the surface of the shell.

An example of the use of this shell is the stands of the Zarzuela racetrack in Madrid (Fig. 22, b) and the market in Co (France) (Fig. 22, c).

The formation of the surface of a hyperbolic paraboloid (hypara) is determined by systems of non-parallel and non-intersecting straight lines (Fig. 12, h), which are called guide lines. Each point of a hyperbolic paraboloid is the intersection point of two generatrices that make up the surface.

Rice. 22 Examples of the use of conoidal shells and hyperboloids of revolution

With a uniformly distributed load, the stresses at all points on the hypar surface have a constant value. This is explained by the fact that the tensile and compressive forces are the same for each point. This is why hyparas have greater resistance to bulging. When the shell tends to bend under load, the tensile stress in the direction normal to this pressure automatically increases. This makes it possible to produce shells of low thickness, often without edges.

The first static studies of hypars were published in 1935 by the Frenchman Lafaille, but they found practical application only after the Second World War. Boroni in Italy, Ruban in Czechoslovakia, Candela in Mexico, Salvadori in the USA, Sarge in France. The operational and economic advantages of hypars and unlimited aesthetic possibilities create enormous scope for their use.

In Fig. 16, f, g, h, and shows possible combinations of the surfaces of flat hypars.

Rice. 23 Examples of the use of hypars in construction

Covering of the city theater hall in Shizuska (Japan) architect Kenzo Tange, engineer Shoshikatsu Pauobi (Fig. 23, a). The hall has 2,500 seats for spectators. The building is square in plan, with a side equal to 54 m. The shell has the shape of a hyparum, the surface of which is reinforced with stiffeners located parallel to the sides of the square at intervals of 2.4 m. The entire load from the covering is transferred to two reinforced concrete supports, connected to each other under the floor of the hall by reinforced concrete purlins. Additional supports for the shell rand beams are thin swinging posts along the building facades. The width of the rand beam is 2.4 m, thickness 60 cm, shell thickness 7.5 cm.

The chapel and park restaurant in Mexico City were designed by engineer Felix Candela. In these structures, combinations of several hyperbolic paraboloids were used (Fig. 23, b, c)

A nightclub in Acapulco (Mexico) was also designed by F. Candela. In this work, 6 hypars were used.

World construction practice is rich in examples of various forms of hypars in construction.

6 Cross-rib and cross-bar coverings

Cross-ribbed roofing is a system of beams or trusses with parallel chords crossing in two and sometimes three directions. These coatings are similar in their performance to the performance of a solid slab. By creating a cross system, it becomes possible to reduce the height of trusses or beams to 1/6-1/24 spans. It should be noted that cross systems are only effective for rectangular rooms with an aspect ratio ranging from 1:1 to 1.25:1. With a further increase in this ratio, the structure loses its advantages, turning into a conventional beam system. In cross systems, it is very advantageous to use consoles with a reach of up to 1/5-1/4 span. Rational support of cross coverings, using the spatial nature of their work, allows you to optimize their use and build coverings of various sizes and supports from the same type of prefabricated elements of factory production.

In cross-ribbed coverings, the distance between the ribs is from 1.5 m to 6 m. Cross-ribbed coverings can be steel, reinforced concrete, or wood.

Cross-ribbed coverings made of reinforced concrete in the form of caissons can be rationally used with spans up to 36 m. For large spans, one should switch to the use of steel or reinforced concrete trusses.

Wooden cross coverings up to 24 sizes × 24 m are made of plywood and bars with glue and nails.

An example of the use of cross trusses can be the project of the Congress Hall in Chicago completed in 1954 by the architect Van Der Rohe (USA). Hall covering dimensions 219.5 × 219.5 m (Fig. 24, a).

Rice. 24 Cross-ribbed coverings made in metal

The height of the hall to the top of the structures is 34 m. The cross structures are made of steel trusses with parallel chords with a diagonal lattice height of 9.1 m. The entire structure rests on 24 supports (6 supports on each side of the square).

In the exhibition pavilion in Sokolniki (Moscow), built in 1960 according to the Mosproekt project, a cross-coating system measuring 46 × 46 m of aluminum trusses supported by 8 columns. The pitch of the trusses is 6 m, height is 2.4 m. The roof is made of aluminum panels 6 m long (Fig. 24, b)

The Institute VNIIZhelezobeton together with TsNIIEPzhilishchi developed an original design of a cross-diagonal covering measuring 64 ×64 m, made of prefabricated reinforced concrete elements. The covering rests on 24 columns located on the sides of a 48 square × 48 m, and consists of a span and a cantilever part with a projection of 8 m. The column spacing is 8 m.

This design found its application in the construction of the House of Furniture on Lomonosovsky Prospekt in Moscow (authors A. Obraztsov, M. Kontridze, V. Antonov, etc.) The entire covering is made of 112 prefabricated solid reinforced concrete elements of an I-section with a length of 11.32 m and 32 similar elements 5.66 m long (Fig. 25). The enclosing element of the coating is a lightweight prefabricated insulated shield, on which a multi-layer waterproofing carpet is laid.

Rod spatial structures made of metal are a further development of planar lattice structures. The principle of a core spatial structure has been known to mankind since ancient times; it was used in Mongolian yurts and in the huts of the inhabitants tropical Africa, and in frame buildings of the Middle Ages, and in our time - in the structures of a bicycle, an airplane, a crane, etc.

Rod spatial structures have become widespread in many countries around the world. this is explained by the simplicity of their manufacture, ease of installation, and most importantly, the possibility of industrial production. Whatever the shape of the core spatial structure, three types of elements can always be distinguished in it: nodes, connecting rods and zones. connected to each other in a certain order, these elements form flat spatial systems.

Spatial systems of rod structures include:

Core structural slabs (Fig. 26);

Mesh shells (cylindrical and conical shells, transfer shells and domes) (Fig. 27).

Core spatial structures can be single-zone, double-zone or multi-zone. for example, structural slabs are made with two chords, and mesh domes and cylindrical shells for normal spans are made with single chords.

The nodes and connecting rods form the space enclosed between them (zone). zones can be in the form of a tetrahedron, hexahedron (cube), octahedron, dodecahedron, etc. the shape of the zone may or may not provide rigidity to the rod system, for example, the tetrahedron, octahedron and icosahedron are rigid zones. The problem of stability for single-layer mesh shells is associated with the possibility of so-called “snapping” of them like thin-walled shells (Fig. 26).

Rice. 26 Metal rod structures

Corner ? may be significantly less than one hundred degrees. The clicking itself does not lead to the collapse of the entire mesh structure; in this case, the structure acquires a different stable equilibrium structure.

The node connections used in rod structures depend on the design of the rod system. Thus, in single-layer mesh shells, nodal connections with rigid pinching of the rods in the direction normal to the surface should be used to avoid “snapping” of the nodes, and in structural slabs, as in general in multi-belt systems, rigid connection of the rods in the nodes is not required. the design of the nodal connection depends on the spatial arrangement of the rods and the capabilities of the manufacturer.

The most common rod connection systems used in world practice are the following:

The "meko" system (threaded connection using a shaped element - a ball) has become widespread due to its ease of manufacture and installation (Fig. 28, c);

A “space deck” system of pyramidal, prefabricated elements, which in the plane of the upper chord are connected to each other with bolts, and in the plane of the lower chord are connected by guy wires (Fig. 28, a);

Connecting rods by welding using ring or spherical shaped parts (Fig. 28, b);

Connecting rods using bent gussets on bolts, etc. (Fig. 28, d); core (structural) slabs have the following basic geometric patterns:

Double belt structure with two families of belt rods;

Double belt structure with three families of belt rods;

Double belt structure with four families of belt rods.

The first structure is the simplest and most commonly used structure today. It is characterized by simplicity of nodal connections (no more than nine rods meet in one node) and is convenient for covering rooms with a rectangular plan. The structural height of the structural slab is assumed to be 1/20 ... 1/25 of the span. with normal spans up to 24 m, the height of the slab is 0.96 ... 1.2 m. If the structure is made of rods of the same length, this length is 1.35 ... 1.7 m. The cells of the structural slab with such dimensions can be covered with conventional roofing elements(cold or insulated) without additional purlins or sheathing. with significant spans of the slab, it is necessary to install purlins under the roof, since with a span of 48 m the height of the slab will be about 1.9 m, and the length of the rods will be about 2.7 m. Examples of the use of structural slabs in the construction are shown in Fig. 29. Mesh cylindrical shells are made in the form of rod meshes with identical cells (Fig. 27). The simplest mesh cylindrical shell is formed by bending a flat triangular mesh. but a cylindrical mesh shell can easily be obtained with a rhombic mesh shape. In these shells, the nodes are located on the surface of different radii, which, like double curvature, increases the load-bearing capacity of the shell. This effect can also be achieved in a triangular bar mesh.

Rice. 28 Some types of nodal connections in rod structures

Mesh domes, having a double curvature surface, are usually made of rods of various lengths. their shape is very diverse (Fig. 27, a). Geodesic domes, the creator of which is engineer Futtler (USA), are a structure in which the surface of the dome is divided into equilateral spherical triangles, formed either by rods of various lengths or panels of various sizes. Mesh conical shells are similar in design to mesh domes, however, they are inferior in rigidity. Their advantages are a retractable surface, which makes it easier to cut roofing elements. The geometric structure of mesh conical shells can be built on the shapes of regular polygons, with three, four or five equilateral triangles meeting at the apex of the cone. All rods of the system have the same length, but the angles in adjacent horizontal chords of the shell change. Other forms of mesh shells are shown in Fig. f 27, b, c, e. Roofing coverings in spatial rod structures, such as structural slabs, differ little from those usually used for steel structures. The coatings of mesh shells of single and double curvature are solved differently. When using lightweight thermal insulation materials, these coatings, as a rule, do not meet thermal requirements (cold in winter, hot in summer). As thermal insulation, we can recommend the optimal material - polystyrene foam.

It can be monolithic (pouring roofing method) or prefabricated; it can be placed directly into molds in which reinforced concrete prefabricated roofing elements are made, etc. this material is lightweight (density 200 kg/m 3), fire-resistant and does not require a cement screed. Other semi-rigid and soft synthetic insulation materials are also used.

The most promising at present should be considered the use of mastic colored roofs, since at the same time they solve the problem of waterproofing and the appearance of structures, which is especially important for coatings of double curvature. In our country, mastic “roofing” is used, which makes it possible to obtain different color shades of the roof (developed research project polymer roofing). In structures where the roof surface is not visible, roofing felt carpet or synthetic films and fabrics can be used. good results are obtained by using roofing packages made of corrugated aluminum sheets with rigid synthetic insulation stamped into them.

Covering the roof with metallic rice materials is not economically feasible. Drainage from the roof surface is decided in each case individually.

5. Hanging (cable-stayed) structures

In 1834, the wire rope was invented - a new structural element that has found very wide application in construction, thanks to its remarkable properties- high strength, low weight, flexibility, durability. In construction, wire ropes were first used as load-bearing structures of suspension bridges, and then became widespread in long-span suspended coverings.

The development of modern cable-stayed structures began at the end of the 19th century. During the construction of the Nizhny Novgorod exhibition in 1896, Russian engineer V.G. Shukhov was the first to use a spatially working metal structure, where the work of rigid elements in bending was replaced by the work of flexible cables in tension.

1 Hanging covers

Hanging coverings are used on buildings of almost any configuration. The architectural appearance of structures with hanging roofs is varied. For hanging coverings, wires, fibers, rods made of steel, glass, plastics and wood are used. Since the beginning of the century, more than 120 buildings with hanging roofs have been built in our country. Domestic science has created a theory for calculating suspended systems and structures using computers.

Currently, there are coverings with a span of about 500 m. In suspended coverings, approximately 5-6 kg of steel per 1 m is consumed on load-bearing elements (cables). 2covered area. Cable-stayed structures have a high degree of readiness, and their installation is simple.

The stability of suspended coverings is ensured by stabilization (pre-tensioning) of flexible cables (cables). Stabilization of cables can be achieved by loading in single-belt systems, creating double-belt systems (cable trusses) and self-tensioning of cables in cross systems (cable mesh). Depending on the method of stabilization of individual cables, various slabs of suspended structures can be created (Fig. 30, 1).

Suspended coverings of single curvature are systems of single cables and double-belt cable-stayed systems. The system of single cables (Fig. 30, 1, a) is a load-bearing coating structure consisting of parallel elements (cables) forming a concave surface.

Prefabricated reinforced concrete slabs are used to stabilize the cables of this system. In the case of embedding cables in the coating structure, a hanging shell is obtained. The magnitude of tensile forces in the cables depends on their sag in the middle of the span. optimal value the sag of the boom is 1/15-1/20 of the span. Cable-stayed coverings with parallel single cables are used for rectangular buildings. By placing the suspension points of the cables to the support contour at different levels or giving them different sag, it is possible to create a coating with curvature in the longitudinal direction, which will allow external drainage from the coating. A two-belt cable-stayed system, or cable truss, consists of supporting and stabilizing cables with different curvatures. Coatings on them can have a small mass (40-60 kg/m 2). The supporting and stabilizing cables are connected to each other by round rods or cable braces. The advantage of two-belt cable-stayed systems with diagonal ties is that they are very reliable under dynamic influences and have low deformation. The optimal amount of sag (lift) of cable truss chords for the upper chord is 1/17-1/20, for the lower belt 1/20-1/25 span (Fig. 30, Fig. 1, c). In Fig. Figure 31 shows examples of single-curvature cable-stayed roofings. Cable-stayed coverings of double curvature can be represented by a system of single cables and double-belt systems, as well as cross systems (cable mesh). Coverings using systems of single cables are most often performed in rooms with a circular plan and radial placement of cables. The cables are attached at one end to the compressed support ring, and at the other to the stretched central ring (Fig. 30, Fig. 1, b). The option of installation in the center of the support is possible. Double-belt systems are accepted similarly to single-curvature floors.

Rice. 31 Examples of cable-stayed coverings of single curvature

In coverings with a circular plan, the following options for the relative position of the supporting and stabilizing cables are possible: the cables diverge or converge from the central ring to the supporting one, the cables intersect each other, diverging in the center and at the perimeter of the covering (Fig. 30). A cross system (cable meshes) is formed by two intersecting families of parallel cables (bearing and stabilizing). The surface of the coating in this case has a saddle shape (Fig. 30, Fig. 1, d). The prestressing force in the stabilizing cables is transmitted to the supporting cables in the form of concentrated forces applied at the intersection nodes. the use of cross systems makes it possible to obtain various forms of cable-stayed coverings. for cross cable-stayed systems, the optimal value for the lifting boom of the stabilizing cables is 1/12-1/15 of the span, and the sag of the supporting cables is 1/25-1/75 of the span. The construction of such coverings is labor-intensive. It was first used by Matthew Nowitzky in 1950 (North Carolina). The cross system allows the use of lightweight roofing coverings in the form of prefabricated slabs of lightweight concrete or reinforced cement.

In Fig. Figures 31 and 32 show examples of cable-stayed roofings with single and double curvature. The shape of the cable-stayed covering and the outline of the plan of the structure being covered determine the geometry of the supporting contour of the covering and, consequently, the shape of the supporting (supporting) structures. These structures are flat or spatial frames (steel or reinforced concrete) with racks of constant or variable height. elements of the supporting structure are crossbars, racks, struts, cable stays and foundations. supporting structures must ensure the placement of anchor fastenings of cables (cables), the transfer of reactions from forces in the cables to the base of the structure and the creation of a rigid supporting contour of the coating to limit deformations of the cable system.

In coverings with a rectangular or square plan, the cables (cable trusses) are usually located parallel to each other. Transfer of thrust can be carried out in several ways:

Through rigid beams located in a flat covering on the end diaphragms (solid walls or buttresses); the intermediate posts perceive only part of the vertical components of the forces in the cables (Fig. 33, c);

Transfer of thrust to frames located in the plane of the cables, with transmission of thrust forces directly to rigid frames or buttresses consisting of stretched or compressed rods (racks, struts). Large tensile forces arising in the braces of frame buttresses are perceived using special anchor devices in the ground in the form of massive foundations or conical (hollow or solid) reinforced concrete anchors (Fig. 33, b);

Transmission of thrust through cable stays is most economical way perception of thrust; Guys can be attached to independent posts and anchor foundations or combined with several guys per post or one anchor device (Fig. 33, a).

In circular coverings, cables or cable trusses are arranged radially. When a uniformly distributed load acts on the coating, the forces in all cables are equal, and the outer support ring is evenly compressed. In this case, there is no need to install anchor foundations. When the load is uneven, bending moments may occur in the support ring, which must be taken into account and excessive moments must be avoided.

For circular coverings, three main options for supporting structures are used:

With the transfer of thrust to the horizontal outer support ring (Fig. 33, d);

With the transmission of forces in the cables to the inclined outer ring (Fig. 33, d);

With the transfer of thrust to inclined contour arches resting

onto a number of racks that absorb vertical forces from the coating (Fig. 33, f, g).

To absorb the forces in the arches, their heels rest on massive foundations or are tied with ties. The theory of calculating cable trusses has now been developed quite fully; there are working formulas and computer programs.

2 Suspended cable-stayed structures

Unlike other types of suspended coverings, in suspended coverings the load-bearing cables are located above the roof surface.

The load-bearing system of suspended coverings consists of cables with vertical or inclined suspensions, which carry either light beams or directly the covering slabs.

The cables are fixed to racks braced in the longitudinal and transverse directions.

Suspended ceilings can have any geometric shape and are made of any materials.

In suspended cable-stayed structures, load-bearing posts can be located in one, two or several rows in the longitudinal or transverse directions (Fig. 34).

When installing suspended cable-stayed structures, instead of guys, you can use cantilever extensions of coverings that balance the tension in the cables.

Several examples from practical construction.

A suspended roof with a transparent plastic roof was first built in 1949 over a bus station in Milan (Italy). The inclined covering is suspended by a system of cables from inclined supporting posts. Balance is achieved by special guys attached to the edges of the covering.

Suspended covering over the Olympic stadium in Squawley (USA). The stadium seats 8,000 spectators. Its dimensions in plan 94.82 × 70.80 m. suspended covering consists of eight pairs of inclined box beams of variable cross-section, supported by cables. The cables are supported by 2 rows of racks installed at intervals of 10.11 m. Purlins are laid along the beams, and along them there are box-section slabs 3.8 m long. The supporting cables - cables have a diameter of 57 mm. When designing suspended structures, significant issues are protecting the suspensions from corrosion in the open air and solving the nodes for the passage of the suspensions through the roof. To do this, it is advisable to use galvanized ropes of a closed profile or profile steel, available for periodic inspection and painting to avoid corrosion.

3 Coverings with rigid cables and membranes

A rigid cable is a series of rod elements made of profile metal, hingedly connected to each other and forming a freely sagging thread when the extreme points are secured to the supports. Connecting rigid cables to each other and to supporting structures does not require the use of complex anchor devices and highly qualified labor.

The main advantage of this coating was its high resistance to wind suction and flutter (flexural-torsional vibrations) without installing special wind connections and prestressing. This was achieved through the use of rigid cables and increasing the constant load on the coating.

Hanging shells made of various rice materials (steel, aluminum alloys, synthetic fabrics etc.) are usually called membranes. Membranes can be manufactured at the factory and delivered to the construction site rolled into rolls. One structural element combines load-bearing and enclosing functions.

The effectiveness of membrane coverings increases if pre-tensioning is used to increase their rigidity instead of heavy roofs and special weights. The sag of membrane coverings is assumed to be 1/15-1/25 of the span.

Along the contour, the membrane is suspended from a steel or reinforced concrete support ring.

The membrane is used for any geometric plan shape. For membranes on a rectangular plan, a cylindrical coating surface is used, on a round plan - spherical or conical (the span is limited to 60 m).

4 Combined systems

When designing long-span structures, there are buildings in which it is advisable to use a combination of a simple structural element (for example, beams, arches, slabs) with a tensioned cable. Some slabs combined designs have been known for a long time. These are truss structures in which the belt-beam works in compression, and the metal rod or cable perceives tensile forces. In more complex structures, it became possible to simplify the structural design and thereby obtain an economic effect compared to traditional long-span structures. An arched cable truss was used in the construction of the Zenit Sports Games Palace in Leningrad. The building is rectangular in plan, dimensions 72 × 126 m. The supporting frame of this hall is designed in the form of ten transverse frames with a pitch of 12 m and two half-timbered end walls. each of the frames was made in the form of a block of two inclined v-shaped columns-struts, four column braces and two arched-cable trusses. The width of each block is 6 m. The reinforced concrete columns-struts are clamped in the base and are hingedly adjacent to the arched-cable truss. The guy columns at the top and bottom are hinged. balancing of thrust forces occurs mainly in the coating itself. This system compares favorably with purely cable-stayed structures, which on a rectangular plan require the installation of guys, buttresses or other special devices. Prestressing the cables will provide a significant reduction in the moments in the arch that arise under certain types of loads.

The cross-section of the steel arch is I-beam, 900 mm high. The shrouds are made of ropes closed type with filler anchors.

A reinforced concrete slab reinforced with trusses was used to cover nine sections with plan dimensions of 12 × 12 m department store in Kyiv. The upper chord of each cell of the system is made up of nine slabs of size 4×4 m. The lower chord is made of crossed reinforcing bars. These rods are hinged to the diagonal ribs of the corner slabs, which allows the forces of the system to be locked inside it, transferring only the vertical load to the column.

5 Structural elements and details of cable-stayed coverings

Wire ropes (ropes). basic construction material cable-stayed coverings - made of cold-drawn steel wire with a diameter of 0.5-6 mm, with a tensile strength of up to 220 kg/mm 2. There are several types of cables:

Spiral cables (Fig. 35, 1, a), consisting of a central wire on which several rows of round wires are spirally wound sequentially in the left and right directions;

Multi-strand cables (Fig. 35, Fig. 1, b), consisting of a core (hemp rope or wire strand), on which wire strands are wound in a one-way or cross twist (the strands can have a spiral twist) in this case the cable will be called a spiral-stranded one ;

Closed or semi-closed cables (Fig. 35, Fig. 1, c, d), consisting of a core (for example, in the form of a spiral cable), around which rows of shaped wires are wound, ensuring their tight fit (with a semi-closed solution, the cable has one row windings made of round and shaped wires);

Cables (bundles) of parallel wires (Fig. 35, Fig. 1, e), having a rectangular or polygonal cross-section and interconnected through certain distances or enclosed in a common sheath;

Flat ribbon cables (Fig. 35, Fig. 1, e), consisting of a series of twisted cables (usually four-strand) with alternating right or left twist, interconnected by single or double stitching with wire or thin wire strands, require reliable protection against corrosion. possible following methods anti-corrosion protection of cables: galvanizing, paint coatings or lubricants, coating with a plastic sheath, coating with a sheath of rice steel with injection of bitumen or cement mortar into the sheath, concrete coating.

The ends of the cables must be made in such a way as to ensure the strength of the end is not less than the strength of the cable and the transfer of forces from the cable to other structural elements. The traditional type of end fastening of cables is a loop with a braid (Fig. 35, Fig. 2, a), when the end of the cable unravels into strands that are woven into the cable. To ensure uniform transmission of force in the connection, a thimble is inserted into the loop. Along the length, the cables are also spliced ​​with braiding, except for closed joints. Instead of braiding, clamp connections are often used to fasten and splice cables:

Pressing both branches of the cable with loop fastening into an oval coupling made of light metal, the internal dimensions of which correspond to the diameter of the cable (Fig. 35, Fig. 2, b);

Screw connections, when the end of the cable is unraveled into strands, which are laid around a rod with a screw thread, and then pressed into a light metal coupling (Fig. 35, Fig. 2, c);

Fastening by means of clamps (Fig. 35, Fig. 2, e, j), which are not recommended for tensioned cable cables, as they weaken over time;

Fastening of cables with metal filling (Fig. 35, Fig. 2, f, g), when the end of the cable is unraveled, cleaned, degreased and placed in the conical internal cavity of a special coupling-tip, and then the coupling is filled with molten lead or a lead-zinc alloy ( concrete filling is possible);

Wedge fastenings of cables, rarely used in construction;

Turnbuckles (Fig. 35, Fig. 2, d), used to adjust the length of cables during installation and pre-tension them. Anchor units serve to absorb forces in the cables and transfer them to supporting structures. in prestressed cable-stayed coverings they are also used for pre-tensioning of cables. In Fig.e 35, Fig. 2, and shows the anchoring of a radial cable of a circular cable-stayed covering in a compressed support ring. To ensure free movement of the cable when its angle of inclination changes, conical sleeves filled with bitumen are installed in the support ring and the adjacent coating shell. the rigid support ring and the flexible shell are separated by an expansion joint.

Coatings and roofs, depending on the type of cable-stayed system, use a heavy or light coating structure.

Heavy coverings are made of reinforced concrete. their weight reaches 170-200 kg/m 2, for prefabricated coverings, flat or ribbed slabs of rectangular or trapezoidal shape are used. precast slabs are usually suspended between cables, and the seams between the slabs are grouted.

Light coatings weighing 40-60 kg/m 2usually made of large-sized steel or aluminum profiled sheets, which simultaneously serve as load-bearing elements of the fence and roof if thermal insulation is missing or is attached from below. When placing thermal insulation on top of the panels, it is necessary to install an additional roofing covering. It is advisable to make lightweight coatings from light metal panels with insulation placed inside the panels.

6. Transformable and pneumatic coverings

1 Transformable coverings

Transformable coatings are coatings that can be easily assembled, transported to a new location, and even completely replaced with a new design solution.

The reasons for the development of such structures in the architecture of modern public buildings are manifold. These include: the rapid obsolescence of the functions of structures, the emergence of new lightweight and durable building materials, the tendency for people to become closer to the environment, the tactful incorporation of structures into the landscape, and finally, the growing number of buildings for temporary purposes or for the irregular stay of people in them.

In order to create lightweight prefabricated structures, it was necessary, first of all, to abandon enclosing structures made of reinforced concrete, reinforced cement, steel, wood and switch to lightweight fabric and film coverings that protect the premises from weather factors (rain, snow, sun and wind) , but almost do not comfortably solve psychological problems: reliability of protection from bad weather, durability, thermal insulation function, etc. the load-bearing functions of transformable structures are performed using various techniques. Accordingly, they can be divided into three main groups: thermal coverings, pneumatic structures and transformable rigid systems.

2 Tent and pneumatic structures

Tent pneumatic structures are essentially membrane coverings, but the enclosing functions are performed by fabric and film materials, the load-bearing functions are supplemented by systems of cables and masts, or rigid frame structures. In pneumatic structures, the load-bearing function is performed by air or other light gas. pneumatic and awning structures belong to the class of soft shells and can be given any shape. Their peculiarity is the ability to perceive only tensile forces. To strengthen soft shells, steel cables are used, which are made from corrosion-resistant steel or ordinary steel with a polymer coating. Cables made from synthetic and natural fibers are very promising.

Depending on the materials used, soft shells can be divided into two main types:

Isotropic shells (from metal rice and foil, from film and rice plastics or rubber, from non-oriented fibrous materials);

Anisotropic shells (from fabrics and reinforced films, from wire and cable mesh with cells filled with films or fabrics).

According to their design, soft shells have the following varieties:

Pneumatic structures are soft closed shells stabilized by excess air pressure (they, in turn, are divided into pneumatic frame, pneumatic panel and air-supported structures);

Awning coverings in which stability of shape is ensured by an appropriate choice of surface curvature (there are no supporting cables);

Cable-stayed tents are presented in the form of soft shells of single and double curvature, reinforced over the entire surface and along the edges by a system of cables (cable cables) working in conjunction with the tent shell;

Cable-stayed coverings have a main supporting structure in the form of a system of cables (cables) with rice, fabric or film filler for the cable mesh cells, which absorbs only local forces and primarily performs the functions of a fence.

Pneumatic structures appeared in 1946. Pneumatic structures are soft shells, the pre-tension of which is achieved due to air pumped into them. The materials from which they are made are airtight fabrics and reinforced films. They have high tensile strength, but are not able to resist any kind of stress. The fullest use of the structural properties of the material leads to the formation of various forms, but any of the forms must be subject to certain laws. Incorrectly designed pneumatic structures will reveal the architect's mistake by the formation of cracks and folds that distort the shape, or loss of stability.

Therefore, when creating forms of pneumatic structures, it is very important to remain within certain boundaries, beyond which the very nature of soft shells, stressed by internal air pressure, does not allow.

Dozens of pneumatic structures have been erected in different countries, including our country. for various purposes. In industry, they are used for various types of warehouse structures, in agriculture, livestock farms are built, in civil engineering, they are used for temporary premises: exhibition halls, shopping and entertainment facilities, and sports facilities.

Pneumatic structures are classified into air-supported, air-carrying and combined. Air-supported pneumatic structures are systems in which excess air pressure is created in thousandths of an atmosphere. This pressure is practically not felt by humans and is maintained using low-pressure fans or blowers. An air-supported building consists of the following structural elements: a flexible fabric or plastic shell, anchor devices for supplying air and maintaining a constant pressure difference. The tightness of the structure is ensured by the airtightness of the shell material and tight connection with the base. The entrance airlock has two alternately opening doors, which reduces air consumption during operation of the shell. The base of the air support structure is a contour pipe made of soft material, filled with water or sand, which is located directly on the leveled area. In more permanent structures, a solid concrete base is made, on which the shell is strengthened. The options for attaching the shell to the base are varied.

The simplest form of air-supported structures is a spherical dome, the stress in which from the internal air pressure is the same at all points. Cylindrical shells with spherical ends and toroidal shells have become widespread. The shapes of air-supporting shells are determined by their plan. The dimensions of air-supporting structures are limited by the strength of the materials.

To strengthen them, a system of unloading ropes or nets, as well as internal guy wires, is used. Air-carrying structures include those pneumatic structures in which excess air pressure is created in the sealed cavities of the load-bearing elements of pneumatic frames. pneumatic frames can be presented in the form of arches or frames consisting of curved or straight elements.

Structures, the frame of which are arches or frames, are covered with an awning or connected by awning inserts. if necessary, the structure is stabilized using cables or ropes. the low load-bearing capacity of the pneumatic frame sometimes leads to the need to place the pneumatic arches close to each other. at the same time, the structure acquires a new quality, which can be considered as a special type of air-carrying structures - pneumatic panel structures. Their advantage is the combination of load-bearing and enclosing functions, high thermal performance, increased stability. Another type is a pneumatic lens coating formed by two shells, and air under pressure is supplied into the space between them. It is impossible not to say about reinforced concrete shells erected using pneumatic shells. To do this, fresh concrete mixture is placed on a reinforcement cage located on the ground along the pneumatic shell film. The concrete is covered with a layer of film, and air is supplied to the pneumatic shell laid out on the ground and it, together with the concrete, rises to the design position, where the concrete gains strength. In this way, domed buildings, shallow shells with flat contours and other forms of coverings can be formed.

Transformable rigid systems. When designing public buildings, sometimes it becomes necessary to provide for the extension of the covering and its closure in case of bad weather. The first such structure was the roof dome over the stadium in Pittsburgh (USA). The dome flaps, sliding along the guides, were moved using electric motors by two flaps, rigidly fixed in a reinforced concrete ring and cantilevered over the stadium using a special triangular shape. The Moscow Architectural Institute has developed several options for transformable coverings, in particular a folding cross covering with a plan size of 12 × 12 m and a height of 0.6 m made of rectangular steel pipes. The folding cross structure consists of mutually perpendicular flat lattice trusses. The trusses of one direction are end-to-end rigid type, the trusses of the other direction consist of links located in the space between the rigid trusses.

Sliding lattice spatial covering structures are also being developed at the institute. Cover size 15 × 15 m high 2 m designed in the form of two slabs resting on the corners. The sliding lattice is made in the form of a brace system, consisting of pairs of intersecting corner profile rods, hingedly connected at the intersection points of the node parts, hingedly connecting the ends of the braces. When folded for transportation, the structure measures 1.4 × 1.4 × 2.9 m and a mass of 2.0 tons. Moreover, its volume is 80 times less than the design one.

Elements of pneumatic structures. Air-supported structures include as necessary structural elements: the shell itself, anchor devices for fastening the structure to the ground, fastening the shell itself to the base, entrance exit gateways, systems for maintaining excess air pressure, ventilation systems, lighting, etc.

Shells can have a variety of shapes. The individual shell strips are stitched or glued. if it is necessary to have detachable connections, use zippers, lacing, etc. Anchor devices used to ensure the balance of the system can be in the form of ballast weights (prefabricated and monolithic concrete elements, ballast bags and containers, water hoses, etc.), anchors (screw anchors with a diameter of 100-350 mm, expansion and clamshell anchors , anchor piles and slabs) or permanent structures of the structure. The shell is secured to the base of the structure either using clamping parts or anchor loops, or ballast bags and cables. rigid mount is more reliable, but less economical.

Practice of using air-supported pneumatic structures. The idea of ​​using “air cylinders” to cover rooms was put forward back in 1917 by W. Lanchester. Pneumatic structures were first used in 1945 by the Bearder company (USA) for covering a wide variety of structures (exhibition halls, workshops, granaries, warehouses, swimming pools, greenhouses, etc.). The largest hemispherical shells of this company had a diameter of 50-60 m. The first pneumatic structures were distinguished by shapes dictated not by the requirements of architectural expressiveness, but by considerations of ease of cutting panels. In the time since the installation of the first pneumatic dome, pneumatic structures have quickly and widely spread throughout all countries of the world with a developed polymer chemistry industry.

However, the creative imagination of architects who turned to pneumatic structures sought new forms. in 1960, a traveling exhibition housed under a pneumatic shell toured a number of South American capitals. It was designed by the architect Victor Landi, who should still be considered the pioneer of pneumatic architecture, since he tried to bring the form into line not only with the function of the structure, but also with the general architectural concept. And, indeed, the building had an interesting, spectacular shape and attracted the attention of visitors (Fig. 36). Building length 92 m, maximum width 38 m, height 16.3 m. total covered area 2500 m2 .

This structure is also interesting because the covering is formed by two fabric shells. To keep them at a constant distance from each other, a gradation of internal pressure was used. each of the shells has independent injection sources. The space between the outer and inner shell is divided into eight compartments in order to ensure the load-bearing capacity of the shell in the event of a local rupture of the shell. the air gap between the shells is good insulation from solar overheating, which made it possible to abandon cooling units. Rigid frames are installed at the ends of the shell, into which revolving doors are installed for visitors to enter. Adjacent to the diaphragms are entrance canopies in the form of strong air-carrying vaults. These vaults serve to install two temporary flexible diaphragms that form an airlock when bulky exhibits and equipment are brought into the pavilion.

The shape of the structure and the use of fabric shells provide good acoustic conditions. The total weight of the structure, including all metal parts (doors, blowers, fastenings, etc.) is 28 tons. during transportation the building occupies a volume of 875 m 3and fits in one railway carriage. The construction of the structure requires 3-4 working days with 12 workers. All installation is carried out on the ground without the use of crane equipment. The shell fills with air in 30 minutes and is designed to withstand wind loads of up to 113 km/h. The author of the pavilion project is architect V. Landi.

The space radio communication station in Raisting (Germany), built according to the design of engineer W. Baird (USA) in 1964, has a soft shell with a diameter of 48 m, made of two-layer Dacron fabric coated with Hypalon. The panels of fabric in layers are located at an angle of 45 degrees to each other,

This gives the shell some shear rigidity. The internal pressure in the shell can be in the range of 37-150 mm water column (Fig. 36). The Fuji exhibition pavilion at the Osaka World Exhibition (1970) was designed by the architect Murata and is an example of a building solution using progressive technical solutions. The pavilion's covering consists of 16 air hoses-arches with a diameter of 4 m and a length of 72 m each, connected to each other through 5.0 m. Their outer surface is covered with neoprene rubber. Excessive pressure in arched sleeves is 0.08-0.25 atm. Between every two arches two tensioned steel cables are laid to stabilize the entire structure (Fig. 37).

Architect V. Lundy and engineer Baird designed several pneumatic domes for the 1964 New York World's Fair to house restaurants. the domes were arranged in the form of a pyramid or spheres. shells made of bright colored films had a fantastically elegant appearance.

The covering of the summer theater in Boston (USA), made by engineer W. Brand in 1959, is a circular disk-shaped shell with a diameter of 43.5 m and a height in the center of 6 m. A cable is embedded in the edge of the shell, which is attached at certain points to the supporting ring made of steel profiles. the excess internal air pressure in the shell is maintained by two continuously operating blowers and is 25 mm of water column. shell structure weight 1.22 kg/m 2. The covering is removed for the winter.

Pavilion at the agricultural exhibition in Lausanne (Switzerland). The author of the project is F. Otto (Stuttgart), the company "Stromeyer" (Germany). The covering in the form of “sails” of a hyperbolic parabolic shape is a shell made of reinforced polyvinyl chloride film, reinforced by a system of intersecting prestressed cables, which are attached to anchors and steel masts 16.5 m high. The span is 25 m (Fig. 38, a). Open audience at the agricultural exhibition in Markkleeberg (GDR). Authors: association "Devag", Bauer (Leipzig), Rühle (Dresden). Folded covering in the form of a system of prestressed wire ropes with a diameter of 8, 10 and 15 mm with a sheath stretched between them. The covering is suspended from 16 flexible steel posts and secured with guy wires to 16 anchor bolts. The covering is designed as a cable-stayed structure for wind pressure and slope equal to 60 kg/m 2(Fig. 38) The history of the centuries-old development of world construction art testifies to the great role played by spatial structures in public buildings. In many outstanding works of architecture, spatial structures are an integral part, organically fitting into a single whole. The efforts of scientists, designers and builders should be aimed at creating structures that would open up ample opportunities for various functional organization of buildings, to improve design solutions not only from the engineering side, but also from the point of view of improving their architectural and artistic qualities. The whole problem must be solved comprehensively, starting with the study of the physical and mechanical properties of new materials and ending with issues of interior composition. This will allow architects and engineers to approach the solution of the main task - the mass construction of functionally and structurally justified, economical and architecturally expressive public buildings and structures for various purposes, worthy of the modern era.

Used Books

1.Buildings with long-span structures - A.V. Demina

.Long-span roofing structures for public and industrial buildings - Zverev A.N.

Internet resources:

.#"justify">. #"justify">. #"justify">. http://www.bibliotekar.ru/spravochnik-129-tehnologia/96.htm - electronic library.

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General provisions

Long-span buildings are those in which the distance between the supports (load-bearing structures) of the coverings is more than 40 m.

Such buildings include:

− workshops of heavy engineering factories;

− assembly shops of shipbuilding, machine-building plants, hangars, etc.;

− theaters, exhibition halls, indoor stadiums, train stations, covered parking lots and garages.

1. Features of long-span buildings:

a) large dimensions of buildings in plan, exceeding the radius of action of erection cranes;

b) special methods installation of coating elements;

c) the presence, in some cases, of large parts and structures of the building, whatnots, stands of indoor stadiums, foundations for equipment, bulky equipment, etc. under the covering.

2. Methods for constructing long-span buildings

The following methods are used:

a) open;

b) closed;

c) combined.

2.1. The open method is that first, all the building structures located under the roof are erected, i.e.:

− shelves (single or multi-tiered structure under the covering of industrial buildings for technological equipment, offices, etc.);

− structures for accommodating spectators (in theaters, circuses, indoor stadiums, etc.);

− foundations for equipment;

− sometimes cumbersome technological equipment.

Then the covering is arranged.

2.2. The closed method consists of first removing the covering, and then erecting all the structures underneath it (Fig. 18).

Rice. 18. Scheme of construction of the gym (cross section):

1 – vertical load-bearing elements; 2 – membrane coating; 3 – built-in premises with stands; 4 – mobile jib crane

2.3. The combined method consists of first performing all the structures located below the covering in separate sections (grips), and then constructing the covering (Fig. 19).

Rice. 19. Fragment of the construction plan:

1 – installed building covering; 2 – shelf; 3 – foundations for equipment; 4 – crane tracks; 5 – tower crane

The use of methods for constructing large-span buildings depends on the following main factors:

− on the possibility of locating load-lifting cranes in plan in relation to the building under construction (outside the building or in plan);

− on the availability and possibility of using crane beams (overhead cranes) for the construction of internal parts of building structures;

− on the possibility of installing coatings in the presence of completed parts of the building and structures located under the coating.

When constructing long-span buildings, a particular difficulty is the installation of coverings (shells, arched, domed, cable-stayed, membrane).

The technology for constructing the remaining structural elements is usually not difficult. The work on their installation is discussed in the course “Technology of Construction Processes”.

It is considered in the course of TSP and will not be considered in the course of TVZ and C and the technology of beam coverings.

3.1.3.1. TVZ in the form of shells

In recent years, a large number of thin-walled spatial reinforced concrete covering structures in the form of shells, folds, tents, etc. have been developed and implemented. The effectiveness of such structures is due to more economical consumption of materials, lighter weight and new architectural qualities. Already the first experience in operating such structures made it possible to discover two main advantages of spatial thin-walled reinforced concrete pavements:

− cost-effectiveness resulting from a more complete use of the properties of concrete and steel compared to planar systems;

− the possibility of rational use of reinforced concrete to cover large areas without intermediate supports.

Reinforced concrete shells, according to the method of construction, are divided into monolithic, assembly-monolithic and prefabricated. Monolithic shells entirely concreted at the construction site on stationary or mobile formwork. Prefabricated monolithic shells can consist of prefabricated contour elements and a monolithic shell, concreted on movable formwork, most often suspended from mounted diaphragms or side elements. Prefabricated shells assembled from separate, pre-fabricated elements, which, after installing them in place, are joined together; Moreover, the connections must ensure reliable transfer of forces from one element to another and the operation of the prefabricated structure as a single spatial system.

Prefabricated shells can be divided into the following elements: flat and curved slabs (smooth or ribbed); diaphragms and side elements.

Diaphragms and side elements can be either reinforced concrete or steel. It should be noted that the choice of design solutions for shells is closely related to construction methods.

Double shell(positive Gaussian) curvature, square in plan, formed from prefabricated reinforced concrete ribbed shells And contour trusses. The geometric shape of double-curvature shells creates favorable conditions for static work, since 80% of the shell area works only in compression and only in the corner zones are there tensile forces. The shell of the shell has the shape of a polyhedron with diamond-shaped edges. Since the slabs are flat and square, the diamond-shaped edges are achieved by sealing the seams between them. Average standard slabs are molded with dimensions of 2970×2970 mm, thicknesses of 25, 30 and 40 mm, with diagonal ribs 200 mm high, and side ribs 80 mm high. The contour and corner slabs have diagonal and side ribs of the same height as the middle ones, and the side ribs adjacent to the edge of the shell have thickenings and grooves for the outlets of the contour truss reinforcement. The connection of the slabs to each other is carried out by welding the frame releases of the diagonal ribs and cementing the seams between the slabs. A triangular cutout is left in the corner slabs, which is sealed with concrete.

The contour elements of the shell are made in the form of solid trusses or prestressed diagonal half-trusses, the joint of which in the upper chord is made by welding overlays, and in the lower - by welding the outlets of the rod reinforcement with their subsequent concrete coating. It is advisable to use shells to cover large areas without intermediate supports. Reinforced concrete shells, which can be given virtually any shape, can enrich the architectural design of both public and industrial buildings.

Rice. 20. Geometric schemes of shells:

A– cutting with planes parallel to the contour; b– radial-circular cutting; V– cutting into diamond-shaped flat slabs

In Fig. Figure 21 shows geometric schemes for covering buildings with a rectangular grid of columns with shells made of cylindrical panels.

Depending on the type of shell, the size of its elements, as well as the dimensions of the shell in plan, installation is carried out using various methods, differing mainly in the presence or absence of mounting scaffolding.

Rice. 21. Options for the formation of prefabricated cylindrical shells:

A– from curved ribbed panels with side elements; b– the same with one side element; V– from flat ribbed or smooth slabs, side beams and diaphragms; G– from large curved panels, side beams and diaphragms; d– of arches or trusses and vaulted or flat ribbed panels (short shell)

Let's consider an example of the construction of a two-span building with a covering of eight square-plan shells of doubly positive Gaussian curvature. The dimensions of the coating structural elements are shown in Fig. 22, A. The building has two spans, each of which contains four cells measuring 36 × 36 m (Fig. 22, b).

The significant consumption of metal for supporting scaffolding during the installation of double-curvature shells reduces the efficiency of using these progressive structures. Therefore, for the construction of such shells up to 36 × 36 m in size, rolling telescopic conductors with mesh circles are used (Fig. 22, V).

The building in question is a homogeneous object. Installation of coating shells includes the following processes: 1) installation (rearrangement) of the conductor; 2) installation of contour trusses and panels (installation, laying, alignment, welding of embedded parts); 3) monolithization of the shell (filling of seams).

Rice. 22. Construction of a building covered with prefabricated shells:

A– design of the coating shell; b– diagram of the division of the building into sections; V– diagram of the conductor’s operation; G– the sequence of installation of covering elements for one area; d– the sequence of construction of the covering in sections of the building; I–II – numbers of spans; 1 – contour shell trusses, consisting of two half-trusses; 2 – covering slab measuring 3×3 m; 3 – building columns; 4 – telescopic conductor towers; 5 – mesh conductor circles; 6 – hinged supports of the conductor for temporary fastening of elements of contour trusses; 7 – 17 – sequence of installation of contour trusses and covering slabs.

Since when installing the coating, a rolling conductor is used, which is moved only after curing the mortar and concrete, one span cell is taken as the installation section (Fig. 22, b).

Installation of the shell panels begins with the outer ones, based on the conductor and the contour truss, then the remaining shell panels are mounted (Fig. 22, G, d).

3.1.3.2. Technology for constructing buildings with domed roofs

Depending on the design solution, the installation of domes is carried out using a temporary support, a hinged method or in its entirety.

Spherical domes are erected in ring tiers from prefabricated reinforced concrete panels using a hinged method. Each of the ring tiers, after complete assembly, has static stability and load-bearing capacity and serves as the basis for the overlying tier. Prefabricated reinforced concrete domes of indoor markets are installed in this way.

The panels are lifted by a tower crane located in the center of the building. Temporary fastening of the panels of each tier is carried out using an inventory device (Fig. 23, b) in the form of a stand with guys and a turnbuckle. The number of such devices depends on the number of panels in the ring of each tier.

Work is carried out from inventory scaffolding (Fig. 23, V), arranged outside the dome and moved during installation. Adjacent panels are connected to each other with bolts. The seams between the panels are sealed with cement mortar, which is first laid along the edges of the seam and then pumped into its internal cavity using a mortar pump. A reinforced concrete belt is placed along the upper edge of the panels of the assembled ring. After the mortar of the seams and the concrete of the belt acquire the required strength, the racks with guys are removed, and the installation cycle is repeated on the next tier.

Prefabricated domes are also mounted in a hinged manner by sequential assembly of ring belts using a movable metal truss template and racks with hangers for holding prefabricated slabs (Fig. 23, G). This method is used when installing prefabricated reinforced concrete circus domes.

To install the dome, a tower crane is installed in the center of the building. A mobile template truss is installed on the crane tower and the ring track located along the reinforced concrete cornice of the building. To ensure greater rigidity, the crane tower is braced with four braces. If the boom reach and lifting capacity of one crane are insufficient, a second crane is installed on the ring track near the building.

Prefabricated dome panels are installed in the following order. Each panel, in an inclined position corresponding to its design position in the coating, is lifted by a tower crane and installed with its lower corners on the inclined welded linings of the assembly, and with its upper corners on the installation screws of the template truss.

Rice. 23. Construction of buildings with domed coverings:

A– dome design; b– diagram of temporary fastening of dome panels; V– diagram of fastening the scaffolding for the construction of the dome; G– diagram of the dome installation using a mobile template truss; 1 – lower support ring; 2 – panels; 3 – upper support ring; 4 – rack of inventory device; 5 – guy; 6 – turnbuckle; 7 – mounted panel; 8 – mounted panels; 9 – strut with holes to change the slope of the scaffold bracket; 10 – rack for railings; 11 – bracket crossbar; 12 – eye for attaching the bracket to the panel; 13 – mounting racks; 14 – strut braces; 15 – hangers for holding slabs; 16 – template truss; 17 – crane braces; 18 – panel truck

Next, the upper edges of the embedded parts of the upper corners of the panel are aligned, after which the slings are removed, the panel is secured with hangers to the mounting posts, and the hangers are tensioned using turnbuckles. The template truss set screws are then lowered by 100 - 150 mm and the template truss is moved to a new position for installation of the adjacent panel. After installing all the belt panels and welding the joints, the joints are sealed with concrete.

The next dome belt is installed after the concrete joints of the underlying belt have acquired the required strength. Upon completion of installation of the upper belt, remove the pendants from the panels of the underlying belt.

In construction, they also use the method of lifting concrete floors with a diameter of 62 m in their entirety using a system of jacks mounted on columns.

3.1.3.3. Technology for constructing buildings with cable-stayed roofs

The most critical process in the construction of such buildings is the installation of coverings. The composition and sequence of installation of cable-stayed coverings depends on their design diagram. The leading and most complex process in this case is the installation of the cable-stayed network.

The structure of the suspended roof with a cable system consists of a monolithic reinforced concrete support contour; fixed on the supporting contour of the cable-stayed network; prefabricated reinforced concrete slabs laid on a cable-stayed network.

After the design tension of the cable-stayed network and grouting of the seams between the slabs and cables, the shell works as a single monolithic structure.

The cable network consists of a system of longitudinal and transverse cables located along the main directions of the shell surface at right angles to each other. In the support contour, the cables are secured using anchors consisting of sleeves and wedges, with the help of which the ends of each cable are crimped.

The cable-stayed shell network is installed in the following sequence. Each cable is installed in place using a crane in two steps. First, with the help of a crane, one end of it, removed from the drum by a traverse, is fed to the installation site. The cable anchor is pulled through the embedded part in the support contour, then the remaining part of the cable on the drum is secured and rolled out. After this, two cranes are used to lift the cable to the level of the support contour, while simultaneously pulling the second anchor to the support contour with a winch (Fig. 24, A). The anchor is pulled through the embedded part in the support contour and secured with a nut and washer. The cables are lifted together with special hangers and control weights for subsequent geodetic alignment.

Rice. 24. Construction of a building with cable-stayed roofing:

A– diagram of lifting the working cable; b– diagram of mutually perpendicular symmetrical tension of cables; V– alignment diagram of longitudinal cables; G– details of the final fastening of the cables; 1 – electric winch; 2 – guy; 3 – monolithic reinforced concrete support contour; 4 – lifted cable; 5 – traverse; 6 – level

Upon completion of the installation of the longitudinal cables and their pre-tensioning to a force of 29.420 - 49.033 kN (3 - 5 tf), a geodetic verification of their position is performed by determining the coordinates of the points of the cable network. Tables are drawn up in advance in which, for each cable, the distance of the control weight attachment points on the anchor sleeve from the reference point is indicated. At these points, test weights weighing 500 kg are suspended from a wire. The lengths of the pendants are different and calculated in advance.

When the working cables sag correctly, the control weights (risks on them) should be at the same mark.

After adjusting the position of the longitudinal cables, the transverse cables are installed. The places where they intersect with the working cables are secured with constant compression. At the same time, temporary guy wires are installed to secure the position of the cable-stay intersection points. Then the cable network surface is re-checked for compliance with the design. The cable-stayed network is then tensioned in three stages using 100-ton hydraulic jacks and traverses attached to sleeve anchors.

The tension sequence is determined from the conditions of tension of the cables in groups, simultaneous tension of the groups in the perpendicular direction, and symmetry of the tension of the groups relative to the axis of the building.

At the end of the second stage of tension, i.e. When the forces determined by the project are achieved, prefabricated reinforced concrete slabs are laid on the cable-stayed network in the direction from the lower mark to the upper one. In this case, formwork is installed on the slabs before they are lifted to seal the seams.

3.1.3.4. Technology of construction of buildings with membrane coatings

TO metal hanging coatings include thin-sheet membranes that combine load-bearing and enclosing functions.

The advantages of membrane coatings are their high manufacturability and installation, as well as the nature of the coating’s operation in biaxial tension, which makes it possible to cover 200-meter spans with a steel membrane only 2 mm thick.

Hanging tensile elements are usually secured to rigid supporting structures, which can be in the form of a closed contour (ring, oval, rectangle) resting on columns.

Let's consider the technology of installing a membrane coating using the example of the coating of the Olimpiysky sports complex in Moscow.

The Olympic sports complex is designed as a spatial structure of an elliptical shape 183×224 m. Along the outer contour of the ellipse, with a pitch of 20 m, there are 32 steel lattice columns, rigidly connected to the outer support ring (section 5×1.75 m). A membrane covering is suspended from the outer ring - a shell with a sag of 12 m. The covering has 64 stabilizing trusses, 2.5 m high, radially located with a step along the outer contour of 10 m, connected by ring elements - girders. The membrane petals were fastened to each other and to the radial elements of the “bed” with high-strength bolts. In the center, the membrane is closed by an internal metal ring of an elliptical shape measuring 24x30 m. The membrane covering was attached to the outer and inner rings with high-strength bolts and welding.

The installation of the membrane covering elements was carried out in large spatial blocks using a BK-1000 tower crane and two installation beams (with a lifting capacity of 50 tons), moving along the outer support ring. Along the long axis, two blocks were assembled simultaneously on two stands.

All 64 stabilizing coating trusses were united in pairs into 32 blocks of nine standard sizes. One such block consisted of two radial stabilizing trusses, girders along the upper and lower chords, vertical and horizontal connections. Pipelines for ventilation and air conditioning systems were installed in the unit. The mass of assembled stabilizing truss blocks reached 43 tons.

The covering blocks were lifted using a spreader beam, which absorbed the thrust force from the stabilizing trusses (Fig. 25).

Before lifting the truss blocks, they pre-stressed the upper chord of each truss with a force of about 1300 kN (210 MPa) and secured them with this force to the support rings of the coating.

The installation of prestressed blocks was carried out in stages by symmetrically installing several blocks along radii of the same diameter. After the installation of eight symmetrically installed blocks along with traverse spacers, they were simultaneously untwisted with the transmission of thrust forces evenly to the outer and inner rings.

The block of stabilizing trusses was lifted using a BK-1000 crane and an installer approximately 1 m above the outer ring. Then the chevre was moved to the installation site of this block. The block was unslinged only after it had been fully secured to the inner and outer rings as designed.

The membrane shell weighing 1569 tons consisted of 64 sector petals. The membrane petals were installed after the installation of the stabilization system was completed and secured with high-strength bolts with a diameter of 24 mm.

The membrane panels arrived at the installation site in the form of rolls. Rolling racks were located at the site where the stabilizing trusses were assembled.

Rice. 25. Scheme of installation of coating with enlarged blocks:

A– plan; b- incision; 1 – chevre-installer; 2 – stand for larger assembly of blocks; 3 – traverse-spacer for lifting the block and prestressing the upper chords of the trusses using a lever device (5); 4 – enlarged block; 6 – installation crane BK – 1000; 7 – central support ring; 8 – central temporary support; I – V – sequence of installation of blocks and dismantling of traverse struts

The installation of the petals was carried out in the sequence of installation of the stabilizing trusses. The tension of the membrane petals was carried out by two hydraulic jacks with a force of 250 kN each.

In parallel with laying and tensioning the membrane petals, holes were drilled and high-strength bolts were installed (97 thousand holes with a diameter of 27 mm). After assembly and design fastening of all elements of the coating, it was untwisted, i.e. release of the central support and smooth inclusion of the entire spatial structure into operation.

Planar structures

A

LECTURE 7. STRUCTURAL SYSTEMS AND STRUCTURAL ELEMENTS OF INDUSTRIAL BUILDINGS

Frames of industrial buildings

Steel frame of one-story buildings

The steel frame of one-story buildings consists of the same elements as reinforced concrete (Fig.)

Rice. Steel frame building

There are two main parts in steel columns: the rod (branch) and the base (shoe) (Fig. 73).

Rice. 73. Steel columns.

A– constant cross-section with console; b– separate type.

1 – crane part of the column; 2 – supracolumn, 3 – additional height of the supracolumn; 4 – tent branch; 5 – crane branch; 6 – shoe; 7 – crane beam; 8 – crane rail; 9 – covering truss.

Shoes serve to transfer the load from the column to the foundation. Shoes and lower parts of columns in contact with the ground are concreted to prevent corrosion. To support the walls, prefabricated reinforced concrete foundation beams are installed between the foundations of the outer columns.

Steel crane beams can be solid or lattice. The most widely used are solid crane beams having an I-section: asymmetrical, used with a column spacing of 6 meters, or symmetrical with a column spacing of 12 meters.

The main load-bearing structures of coatings in buildings with steel frame are roof trusses (Fig. 74).

Rice. 74. Steel trusses:

A– with parallel belts; b- Same; V– triangular; G– polygonal;

d – polygonal truss design.

In outline they can be with parallel belts, triangular, polygonal.

Trusses with parallel belts are used in buildings with flat roofs, and also as rafters.

Triangular trusses are used in buildings with roofs that require large slopes, for example, made of asbestos-cement sheets.

The rigidity of the steel frame and its perception of wind loads and inertial influences from cranes is ensured by the arrangement of connections. Between the columns in longitudinal rows, vertical connections are placed - cross or portal. Horizontal transverse ties are placed in the planes of the upper and lower chords, and vertical ones - along the axes of the support posts and in one or more planes in the middle of the span.

Expansion joints

In frame buildings, expansion joints divide the building frame and all structures resting on it into separate sections. There are transverse and longitudinal seams.

Transverse expansion joints are installed on paired columns that support the structures of adjacent sections of the building cut by the joint. If the seam is also sedimentary, then it is also installed in the foundations of paired columns.

In one-story buildings, the axis of the transverse expansion joint is combined with the transverse alignment axis of the row. Expansion joints in the floors of multi-story buildings are also solved.

Longitudinal expansion joints in buildings with a reinforced concrete frame are made on two longitudinal rows of columns, and in buildings with a steel frame - on one row of columns.

Walls of industrial buildings

In buildings without frames or with an incomplete frame, the outer walls are load-bearing and are made of brick, large blocks or other stones. In buildings with a full frame, the walls are made of the same materials, self-supporting on foundation beams or panel - self-supporting or hinged. External walls are located on the outside of the columns, interior walls buildings are supported on foundation beams or strip foundations.

In frame buildings with a significant length and height of the walls, to ensure stability between the elements of the main frame, additional racks are introduced, sometimes crossbars, forming an auxiliary frame called half-timbered.

For external drainage from coatings, the longitudinal walls of industrial buildings are made with cornices, and the end walls are made with parapet walls. With internal drainage, parapets are erected along the entire perimeter of the building.

Walls made of large panels

Reinforced concrete ribbed panels are intended for unheated buildings and buildings with large industrial heat releases. Wall thickness 30 millimeters.

Panels for heated buildings are made from insulated reinforced concrete or lightweight cellular concrete. Reinforced concrete insulated panels have a thickness of 280 and 300 millimeters.

The panels are divided into ordinary (for blank walls), lintel panels (for installation above and below window openings) and parapet panels.

In Fig. 79 shows a fragment of a wall of a frame panel building with strip glazing.

Rice. 79. Fragment of a wall made of large panels

The filling of window openings in panel buildings is carried out mainly in the form of strip glazing. The height of the openings is taken to be a multiple of 1.2 meters, the width is equal to the pitch of the wall columns.

For individual window openings of smaller width, wall panels with dimensions of 0.75, 1.5, 3.0 meters are used in accordance with the dimensions of standard frames.

Windows, doors, gates, lanterns

Lanterns

To provide lighting for workplaces located far from windows and for aeration (ventilation) of premises, lanterns are installed in industrial buildings.

Lanterns come in light, aeration and mixed types:

Lights with solid glazed frames, serving only to illuminate rooms;

Light-aeration with opening glazed doors, used for lighting and ventilation of rooms;

Aeration without glazing, used only for aeration purposes.

Lanterns can be of various profiles with vertical, inclined or horizontal glazing.

The profile of the lanterns is rectangular with vertical glazing, trapezoidal and triangular with inclined glazing, jagged with one-sided vertical glazing. In industrial construction, rectangular lanterns are usually used. (Fig. 83).

Rice. 83. Basic schemes of light and light-aeration lanterns:

A– rectangular; b– trapezoidal; V– toothed; G– triangular.

Based on their location relative to the axis of the building, lanterns are distinguished between longitudinal and transverse. Longitudinal lights are the most widespread.

Water drainage from lanterns can be external or internal. External is used for lanterns 6 meters wide or when there is no internal drainage system in the building.

The design of the lanterns is framed and consists of a number of transverse frames resting on the upper chords of trusses or roof beams, and a system of longitudinal bracings. The design diagrams of the lamps and their parameters are unified. For spans of 12, 15, and 18 meters, lanterns with a width of 6 meters are used, for spans of 24, 30 and 36 meters - 12 meters wide. The lantern fence consists of a covering, side and end walls.

Lantern covers are made of steel with a length of 6000 millimeters and a height of 1250, 1500 and 1750 millimeters. The bindings are glazed with reinforced or window glass.

Aeration is called natural, controlled and regulated air exchange.

The action of aeration is based on:

On thermal pressure arising due to the difference in temperature between indoor and outdoor air;

At the height difference (difference between the centers of the exhaust and supply openings);

Due to the action of the wind, which blows around the building, it creates a rarefaction of air on the leeward side (Fig. 84).

Rice. 84. Building aeration schemes:

A– the effect of aeration in the absence of wind; b- the same with the action of wind.

The disadvantage of light-aeration lanterns is the need to close the covers on the windward side, since the wind can blow polluted air back into the work area.

Doors and gates

Doors of industrial buildings do not differ in design from panel doors of civil buildings.

The gates are intended to allow vehicles to enter the building and large masses of people to pass through.

The dimensions of the gate are determined in accordance with the dimensions of the equipment being transported. They must exceed the dimensions of the loaded rolling stock in width by 0.5-1.0 meters, and in height by 0.2-0.5 meters.

According to the method of opening, gates can be swing, sliding, lifting, curtain, etc.

Swing gates consist of two panels, hung by means of hinges in the gate frame (Fig. 81). The frame can be wooden, steel or reinforced concrete.

Rice. 81. Swing gates:

1 – pillars of the reinforced concrete frame framing the opening; 2 – crossbar.

If there is no space for opening the doors, the gates are made sliding. Sliding gates come in single-leaf and double-leaf types. Their door leaves have a design similar to swing doors, but in the upper part they are equipped with steel rollers, which, when opening and closing the gate, move along a rail attached to the crossbar of the reinforced concrete frame.

The lifting gate leaves are all-metal, suspended on cables and move along vertical guides.

The panel of curtain doors consists of horizontal elements that form a steel curtain, which, when lifted, is screwed onto a rotating drum located horizontally above the top of the opening.

Coatings

In one-story industrial buildings, the coverings are made without an attic, consisting of the main load-bearing elements of the covering and fencing.

In unheated buildings and buildings with excessive industrial heat generation, the enclosing structures of the coatings are made uninsulated, in heated buildings - insulated.

The cold roof structure consists of a base (flooring) and a roof. The insulated coating includes a vapor barrier and insulation.

Flooring elements are divided into small-sized (1.5 - 3.0 meters long) and large-sized (6 and 12 meters long).

In fencing made of small-sized elements, it becomes necessary to use purlins, which are placed along the building along beams or covering trusses.

Large-sized floorings are laid along the main load-bearing elements and the coatings in this case are called non-run.

Floorings

Non-running reinforced concrete the decks are made of reinforced concrete prestressed ribbed slabs with a width of 1.5 and 3.0 meters and a length equal to the pitch of the beams or trusses.

In non-insulated coverings, a cement strainer, on which the roll roofing is glued.

In insulated coatings, low-thermal conductivity materials are used as insulation and additional vapor barrier is installed. Vapor barrier is especially necessary in coverings above rooms with high humidity air.

Small-size slabs can be reinforced concrete, reinforced cement or reinforced lightweight and cellular concrete.

Roll roofs are made of roofing material. A protective layer of gravel embedded in bitumen mastic is placed on the top layer of roll roofing.

Flooring made from leafy materials.

One of these floorings is galvanized steel profiled flooring, laid on purlins (with a truss spacing of 6 meters) or along lattice purlins (with a spacing of 12 meters).

Pitched cold coverings are often made from corrugated asbestos-cement sheets with a reinforced profile 8 millimeters thick.

In addition, sheets of corrugated fiberglass and other synthetic materials are used.

Drainage from coatings

Drainage extends the life of a building, protecting it from premature aging and destruction.

Drainage from the coatings of industrial buildings can be external and internal.

In one-story buildings, external drainage is arranged unorganized, and in multi-story buildings - with the use of drainpipes.

The internal drainage system consists of water intake funnels and a network of pipes located inside the building that drain water into the storm drain (Fig. 82).

Rice. 82. Internal drainage:

A– water intake funnel; b– cast iron pan;

1 – funnel body; 2 – cover; 3 – pipe; 4 – pipe collar; 5 – cast iron pan; 6 – hole for the pipe; 7 – burlap impregnated with bitumen; 8 – roll roofing; 9 – filling with molten bitumen; 10 – reinforced concrete covering slab.

Internal drainage is arranged:

In multi-span buildings with multi-pitched roofs;

In buildings with large heights or significant differences in height of individual spans;

in buildings with large industrial heat releases, causing snow to melt on the surface.

Floors

Floors in industrial buildings are selected taking into account the nature of production impacts on them and the operational requirements placed on them.

Such requirements may be: heat resistance, chemical resistance, water and gas impermeability, dielectricity, non-sparking upon impact, increased mechanical strength and others.

It is sometimes impossible to select floors that meet all the necessary requirements. In such cases, it is necessary to use different types of floors within the same room.

The floor structure consists of a covering (clothing) and an underlying layer (preparation). In addition, the floor structure may include layers for various purposes. The underlying layer absorbs the load transmitted to the floors through the coating and distributes it to the base.

The underlying layers are rigid (concrete, reinforced concrete, asphalt concrete) and non-rigid (sand, gravel, crushed stone).

When installing floors on interfloor floors, floor slabs serve as the base, and the underlying layer is either absent altogether, or its role is played by heat and sound insulating layers.

Ground floors used in warehouses and hot shops, where they may be subject to shock from falling heavy objects or come into contact with hot parts.

Stone floors used in warehouses where significant shock loads are possible, or in areas covered by tracked vehicles. These floors are durable, but cold and hard. Such floors are usually covered with paving stones (Fig. 85).

Rice. 85. Stone floors:

A– cobblestones; b– from large paving stones; V– from small paving stones;

1 – cobblestone; 2 – sand; 3 – paving stones; 4 - bitumen mastic; 5 – concrete.

Concrete and cement floors used in rooms where the floor may be subject to constant moisture or mineral oils (Fig. 86).

Rice. 86. Concrete and cement floors:

1 – concrete or cement clothing; 2 – concrete underlying layer.

Asphalt and asphalt concrete floors have sufficient strength, water resistance, water resistance, elasticity, and are easy to repair (Fig. 87). The disadvantages of asphalt floors include their ability to soften when the temperature rises, as a result of which they are not suitable for hot workshops. Under the influence of prolonged concentrated loads, dents form in them.

Rice. 87. Asphalt and asphalt concrete floors:

1 – asphalt or asphalt concrete clothing; 2 – concrete underlying layer.

TO ceramic floors include clinker, brick and tile floors (Fig. 88). Such floors are highly resistant to high temperatures and are resistant to acids, alkalis and mineral oils. They are used in rooms that require great cleanliness, in the absence of shock loads.

Rice. 88. Ceramic tile floors:

1 – ceramic tiles; 2 – cement mortar; 3 – concrete.

Metal floors used only in certain areas where hot objects touch the floors and at the same time a flat, hard surface is needed and in workshops with strong shock loads (Fig. 89).

Rice. 89. Metal floors:

1 – cast iron tiles; 2 – sand; 3 – soil base.

Floors can also be used in industrial buildings planks and from synthetic materials. Such floors are used in laboratories, engineering buildings, and administrative premises.

In floors with a rigid underlying layer, expansion joints are installed to avoid cracks. They are placed along the lines of expansion joints of the building and in places where different types of floors meet.

To lay utility lines, channels are installed in the floors.

The junction of floors to walls, columns and machine foundations is made with gaps for free settlement.

In wet rooms, to drain liquids, the floors are given a relief with slopes towards cast iron or concrete water intakes, which are called ladders. The drains are connected to the sewerage system. Along the walls and columns it is necessary to install skirting boards and fillets.

Stairs

Stairs of industrial buildings are divided into the following types:

- basic, used in multi-storey buildings for permanent communication between floors and for evacuation;

- official, leading to work sites and mezzanines;

- fire extinguishers, mandatory for building heights of more than 10 meters and intended for fire brigade members to climb onto the roof (Fig. 90).

Rice. 90. Fire escape

- emergency external, arranged for the evacuation of people when there is an insufficient number of main stairs (Fig. 91);

Rice. 91. Emergency ladder

Fire barriers

Classification of buildings and premises by explosion and fire hazard is used to establish fire safety requirements aimed at preventing the possibility of a fire and ensuring fire protection of people and property in the event of a fire. According to explosion and fire hazard, premises are divided into categories A, B, B1-B4, D and D, and buildings into categories A, B, C, D and D.

Categories of premises and buildings are determined based on the type of flammable substances and materials located in the premises, their quantity and fire hazardous properties, as well as based on the space-planning solutions of the premises and the characteristics of the technological processes carried out in them.

Fire barriers are installed to prevent fire from spreading throughout the building in the event of a fire. Fireproof floors serve as horizontal barriers in multi-storey buildings. Vertical barriers are fire walls (firewalls).

Firewall is intended to prevent the spread of fire from one room or building to an adjacent room or building. Firewalls are made of fireproof materials - stone, concrete or reinforced concrete, and must have a fire resistance rating of at least four hours. Firewalls must rest on foundations. Firewalls are made to cover the entire height of the building, separating combustible and non-combustible coverings, ceilings, lanterns and other structures and must rise above combustible roofs by at least 60 centimeters, and above non-combustible roofs by 30 centimeters. Doors, gates, windows, manhole covers and other fillings of openings in firewalls must be fireproof with a fire resistance rating of at least 1.5 hours. Firewalls are designed for stability in the event of a one-sided collapse of floors, coverings and other structures during a fire (Fig. 92).

Rice. 92. Firewalls:

A– in a building with fireproof external walls; b– in a building with combustible or non-combustible external walls; 1 – firewall ridge; 2 – end firewall.

Control questions

1. Name the design diagrams of industrial buildings.

2. Name the main types of frames for industrial buildings.

3. What types of walls are there in industrial buildings?

LECTURE 8. STRUCTURAL SYSTEMS AND STRUCTURAL ELEMENTS OF AGRICULTURAL BUILDINGS AND STRUCTURES

Greenhouses and greenhouses

Greenhouses and hotbeds are glazed structures in which the necessary climatic and soil conditions are artificially created to allow the cultivation of early vegetables, seedlings and flowers.

Greenhouse buildings are constructed primarily from prefabricated reinforced concrete glazed panels, fastened together by welding embedded parts.

The greenhouse structure consists of prefabricated reinforced concrete frames installed in the ground along the length of the greenhouse and prefabricated reinforced concrete frames (longitudinal bed of the greenhouse) laid on the frame consoles. Removable glazed greenhouse frames are made of wood (Fig. 94).

Rice. 94. Greenhouse made of prefabricated reinforced concrete elements:

1 – reinforced concrete frames; 2 – reinforced concrete northern log; 3 – the same, southern;

4 – sand; 5 – nutrient layer of soil; 6 – heating pipes in a layer of sand;

7 – glazed wooden frame.

LIST OF REFERENCES USED

1. Maklakova T. G., Nanasova S. M. Constructions of civil buildings: Textbook. – M.: ASV Publishing House, 2010. – 296 p.

2. Budasov B.V., Georgievsky O. V., Kaminsky V. P. Construction drawing. Textbook for universities / Under general. ed. O. V. Georgievsky. – M.: Stroyizdat, 2002. – 456 p.

3. Lomakin V. A. Fundamentals of construction. – M.: Higher School, 1976. – 285 p.

4. Krasensky V.E., Fedorovsky L.E. Civil, industrial and agricultural buildings. – M.: Stroyizdat, 1972, – 367 p.

5. Koroev Yu. I Drawing for builders: Textbook. for prof. Textbook establishments. – 6th ed., erased. – M.: Higher. school, ed. Center "Academy", 2000 – 256 p.

6. Chicherin I. I. Civil works: a textbook for beginners. prof. Education. – 6th ed., erased. – M.: Publishing Center “Academy”, 2008. – 416 p.

LECTURE 6. STRUCTURES OF LONG-SPAN BUILDINGS WITH SPATIAL COVERINGS

Depending on the structural design and static operation, load-bearing structures of coatings can be divided into planar (working in the same plane) and spatial.

Planar structures

This group of load-bearing structures includes beams, trusses, frames and arches. They can be made of prefabricated and monolithic reinforced concrete, as well as metal or wood.

Beams and trusses together with columns form a system of transverse frames, the longitudinal connection between which is carried out by covering slabs and wind braces.

Along with prefabricated frames, in a number of buildings of a unique nature, with increased loads and large spans, monolithic reinforced concrete or metal frames are used (Fig. 48).

Rice. 48. Long-span structures:

A- monolithic reinforced concrete frame, double-hinged.

To cover spans over 40 meters, it is advisable to use arched structures. Arches can be structurally divided into two-hinged (with hinges on the supports), three-hinged (with hinges on the supports and in the middle of the span) and hingeless.

The arch works mainly in compression and transfers not only vertical load, but also horizontal pressure (thrust) to the supports.

Compared to beams, trusses and frames, arches have less weight and are more economical in terms of material consumption. Arches are used in structures in combination with vaults and shells.

Long-span coverings of modern industrial buildings, as well as such large public buildings as gyms, sports palaces, buildings of modern supermarkets and hypermarkets, can be designed as long-span planar or spatial structures. They differ in the nature of their static work. In planar structures, all elements work autonomously under load, as a rule, in one direction and do not participate in the operation of structures connected to them. In spatial structures, all or most elements work together in two directions. Thanks to such joint work, the rigidity and load-bearing capacity of the structure are increased, and the consumption of materials for its construction is reduced.

Long-span planar structures are beams and roof trusses. Beams can be rectangular or gable. The lower chord of the beam works in tension, and the upper chord works in compression. Therefore, the main working reinforcement should be placed in the lower chord, and the section of the upper chord should have a large area of ​​concrete that works well in compression. At the supports, the beams must be thickened to absorb the maximum lateral force from the support reactions. This will be covered in the relevant courses in structural mechanics and structures. Beam spans do not exceed 18 m.

Spans of 15, 18, 24 m and more are covered with rod-based planar structures - trusses. In Fig. Figure 13.48 shows types of trusses that differ in shape and, to some extent, in static operation. Trusses can be reinforced concrete, steel or wood. An example of wooden trusses are the trusses designed and built by engineer A. A. Betancourt to cover the 24-meter span of the Central Exhibition Hall in the former Manege on Manezhnaya Square in Moscow, which, after restoration from the fire, have good interior views.

Rice. 13.48.

A – main types of farms; b – a node supporting a truss with parallel chords on a column at “zero” binding (along the outer edge of the column); V – the same, polygonal with a reference of 250 and 500 mm; d – the same, triangular with “zero” reference; 1 – support stand; 2 - Column; 3 – half-timbered crossbar

Along with the oldest rod-post-beam systems of frame buildings from the middle of the 20th century. implemented spatial cross rod systems.

Cross bar systems are formed from linear elements (trusses or beams) intersecting each other at an angle of 90 or 60°, which form a rectangular, triangular or diagonal mesh (Fig. 13.49). The joint spatial work of intersecting linear elements significantly increases the rigidity of the structure. Compared to conventional coverings made from individual planar elements, the structural height of the covering can be reduced by more than half. The use of cross rod systems is most appropriate for covering square, round and polygonal rooms with proportions from 1: 1 to 1: 1.25. To unload the main spans, it is advisable to install cantilever overhangs of cross-covering 0.20–0.25 times the size of the main span.

Rice. 13.49.

a–f – diagrams of cross systems; h – j – position of supports under the cross system; l – cross-rod coating; m – support options and types of supports; L – span of the structure; L K – console crash; 1 – supports; 2 – bordering load-bearing element (beam or truss); 3 – kernel; 4 – connector; 5 – support of the cross-rod system

There are cross-rib and cross-rod systems. Cross ribbed made from metal or reinforced concrete tanks or from board elements. Cross-rod the structures are made mainly of metal in the form of systems of two or four flat lattice disks, fastened in two directions by inclined rods, which form a number of identical pyramids with the tops at the bottom, fastened by the rods of the lower lattice disk.

Arch is a flat-space structure in the form of a beam of curvilinear (circular, parabolic, etc.) outline (Fig. 13.50, A). The ego is like an intermediate type of construction between planar and spatial. In arches, mainly compressive and only under certain conditions bending forces occur. Therefore, arches can cover much larger spans than beams. However, unlike beams, arches transmit not only vertical, but also horizontal forces to the supports - raster Therefore, the supports must be powerful, strengthened buttresses. The thrust can also be extinguished by tightening the heels of the arch and working in tension.

Cylindrical vault(Fig. 13.50, 6) - a spatial structure made up of many arches, having curvature in one direction. The generatrix in a cylindrical vault is a straight line, which forms a curved surface along a guide (along the arc of the arch). Such a surface is convenient in construction, since for its production you can use simple formwork from straight boards laid in curved “circles”.

The intersection of two barrel vaults with the same lifting boom ( f ) forms cross vault, consisting of four equal parts of a cylindrical vault - strippings and having four supports (Fig. 13.50, V).

Rice. 13.50.

A - arch; b – barrel vault; V – cross vault; G - closed vault: d – dome; e – sail vault; and – flat shell; h – barrel vault; And – tray vault; To – surface in the form of a hyperbolic paraboloid; l – a covering of four shells in the shape of a hyperbolic paraboloid; 1 – tightening; 2 – stripping; 3 – cheek

Closed vault also formed from four identical parts of the surface of a cylindrical vault, called trays or cheeks, but resting along the entire perimeter of the covered area (Fig. 13.50, G).

Various types of vaulted structures were used in the architecture of Ancient Persia. They reached great prosperity during the era Ancient Rome and Byzantium (1st century BC – 4th century AD). These structures were built from brick, cut stone and concrete. They received further development in the era of Romanesque and Gothic (XI-XV centuries). Pointed Gothic arches and vaults were brought to Europe during the Crusades. They were characteristic of the architecture of the Arab Caliphate (VII–IX centuries). In modern construction practice, vaulted structures are made of reinforced concrete, reinforced cement, and arched structures are made of reinforced concrete, steel and wood. IN structural mechanics such structural elements are called shells.

If half of the arch is rotated as a generatrix around a vertical axis, we get dome(Fig. 13.50, d). The surface of the dome has curvature in two directions. Shells that have curvature in two directions are called shells of double Gaussian curvature(Carl Friedrich Gauss is a great mathematician). The derivative of the dome is sail vault(sail shell), which, unlike the dome, rests on only four supports and covers a space that is square in plan (Fig. 13.50, e).

Flat shells of double positive Gaussian curvature (Fig. 13.50, and) are widely used in the construction of modern public and industrial buildings. These shells also include transfer shells: barrel and tray vaults. Their surfaces are formed by moving (transferring) a curve along another curve located in a plane perpendicular to the plane of the first curve (Fig. 13.50, h, And).

A special group of curvilinear structures is represented by shells of double negative Gaussian curvature in the form hyperbolic paraboloid, or hypara(Fig. 13.50, To). Its surface is formed by the movement of a parabola with its branches up along the parabola with its branches down, i.e. parabolas have different signs. The tray vault can also have the shape of a hyperbolic paraboloid. A hyperbolic paraboloid is one of the ruled surfaces and can be formed by using rectilinear structural elements. From the part of the paraboloid highlighted in Fig. 13.50, To , can be obtained through various combinations original views shells (Fig. 13.50, l ).

Full (or Gaussian) curvature surfaces TO is called the reciprocal of the product of the radii of the curves of the guide and generatrix of the surface, i.e. .

In the case when both radii have the same signs, i.e. their centers are on one side of the surface, the value TO will be positive (Fig. 13.51, A). In the second case (Fig. 13.51, b) meaning TO – negative, since the radii have different signs. The surface is called a surface of negative Gaussian curvature.

Rice. 13.51. Surface positive(A) and negative(b) curvature

Shells of double curvature are spacer structures. In most types of shell vaults, the thrust is directed outward. In ginars and tray vaults it is directed inward. This means that in order to perceive expansion in shells of positive curvature and cylindrical ones, it is necessary to arrange tightening, as in arches. Instead, diaphragms can be used at the ends and inside long cylindrical shells, or these shells can be supported on powerful supports, sometimes reinforced with buttresses.

The technical possibilities for using stone in dome structures were exhausted in the 1st millennium AD. when covering the Pantheon building in Rome with a dome with a diameter of 43.2 m. The dome rests on a ring wall, the thickness of which is 8 m to absorb the thrust (Fig. 13.52). Another unsurpassed domed structure of antiquity is the dome of the Church of St. Sophia in Constantinople with a diameter of 31.5 m. This dome rests through a system of four spherical sails on only four supports (Fig. 13.53). Unlike the massive wall in the Pantheon, in the Church of St. Sophia, the thrust of the dome is transmitted through arches and semi-domes to adjacent spans (nave), the spatial rigidity of which allows them to withstand the horizontal component of the thrust.

Rice. 13.52.

A - general form: b – incision

Rice. 13.53.

A - general form; b – plan; V – axonometry of load-bearing structures; 1 – arched abutments that absorb the thrust of the coating in the transverse direction; 2 – sail; 3 – dome; 4 – semi-domes that perceive thrust in the longitudinal direction

In the 20th century the geometric parameters of the domes and shells have changed. The stability of the dome's stone structure required that its lifting arm be about half its diameter. Reinforced concrete made it possible to reduce the lifting boom to 1/5–1/6 of the diameter and at the same time achieve a thin-walled dome that exceeds the thin-walledness of biological structures. Thus, the ratio of thickness to diameter of the shell of the large Olympic Sports Palace in Rome, built in 1959 by the outstanding engineer-architect Pietro Luigi Nervi, is 1/1525. In a chicken egg it is 1/100.

The use of reinforced concrete and metal for shell vaults of positive and negative Gaussian curvature makes it possible to make them very light and create new architectural forms. In Fig. 13.54 shows a water park building in Voronezh, covered with a shell in the shape of a hyperbolic paraboloid. The reinforced concrete shell on a rectangular plan stands on two “legs” - the main supports located in its two opposite corners. The supports perceive normal forces from the sides and transmit the vertical reaction to the ground, and the horizontal component through the strut to the tie located in the basement of the structure. The perception of asymmetrical loads is provided by metal structures of stained glass windows. Glazed walls give the building an impression of lightness and originality.

Rice. 13.54.

Combined shells since the last third of the 20th century. are widely used for covering long-span buildings. They are combined from fragments of shells with the same or different signs of curvature. Such combinations make it possible to achieve favorable technical parameters (for example, reducing the lifting boom) and obtain individual expressiveness architectural structures with different plan shapes. Along with hall coverings, such shells are effective for use in engineering structures - towers, tanks, etc.

A special group of spatial structures are folded structures (folds). Folds consist of flat or curved thin-walled elements of a triangular, trapezoidal or other cross-sectional shape (Fig. 13.55). They make it possible to cover large spans (up to 100 m), use materials sparingly and often determine the architectural and artistic expressiveness of the structure. Folds, as well as cylindrical shells and shells of double curvature, are spacer structures. Therefore, along the ends of all fold waves, or in one or several waves, it is necessary to install stiffening diaphragms or horizontal rod connections that work in tension.

Rice. 13.55.

a, b – prismatic sawtooth and trapezoidal; V – sawtooth of triangular planes; G – a tent with a flat top; d – capital fold; e – tent fold with lowered edges; and – multifaceted tent; h – j – multifaceted folded vaults; l – multifaceted folded dome; m – prefabricated folded prismatic covering; n – prefabricated fold from flat elements

Hanging structures have been known since the mid-19th century. But they became widely used 100 years later. The main load-bearing elements in them are flexible ropes, chains, cables (cables), which perceive only tensile forces. Hanging systems (Fig. 13.56) can be flat and spatial. IN flat designs the support reactions of the parallel working cables are transmitted to the support pylons, which are capable of receiving vertical support reactions and thrust, which in this case acts in the direction opposite to the thrust in the convex shells. Therefore, in some cases, guy ropes are used to perceive it (see Fig. 13.56, A), securely embedded in the ground using anchors - special elements that can withstand pulling forces. Sometimes negative thrust is perceived by the very shape of the supporting structures, as, for example, in a sports hall in Bremen (Germany) (Fig. 13.57). Here the supporting structures are made in the form of stands that balance this thrust.

Rice. 13.56. :

A – flat: b – spatial double curvature: V – spatial horizontal

Rice. 13.57.

The enclosing structure of the covering is suspended from the main structure using stretched cables. The enclosing structure can also be made of monolithic reinforced concrete or prefabricated reinforced concrete slabs, which also play the role of loading elements that prevent the reverse bending of such coatings during wind “suction”, i.e. wind load directed from bottom to top. To ensure the geometric immutability of such structures, various methods of stabilization are used. In the above-described flat systems, prestressing is often used by placing an additional weight on top of the slabs. After removing the weight, the cables, trying to shorten to their original length, compress the monolithic reinforced concrete covering, turning it into a hanging concave rigid shell. Drainage from the roof in such structures is carried out by regulating the tension of the roof cables (stronger in the center of the building, weaker at the ends).

Spatial hanging structure(Fig. 13.58) consists of a support contour and a system of cables that form a surface on which the enclosing structure can be laid. The support contour (reinforced concrete or steel) absorbs the thrust from the cable system. Vertical loads are transferred to the posts supporting the support contour or to other structures. To stabilize spatial hanging structures, two systems of cables are often used - working and stabilizing (two-belt design). The cables of both systems are arranged in pairs in planes perpendicular to the surface of the coating and are connected to each other by rigid spacers that create pre-tension of the cables. The enclosing structure of the coating does not participate in the static operation of such a system and can be arranged along load-bearing (sagging) or stabilizing (convex) cables (Fig. 13.59).

Rice. 13.58.

A – arena coverage in the USA; b – covering the singing stage in Tallinn; V – cable-stayed pre-stressing mesh with pick-up cables; G - mesh multi-mast covering of the German exhibition pavilion at the 1967 World Exhibition in Montreal; d – its plan with horizontal lines; 1 – load-bearing cables; 2 – prestressed stabilizing cables; 3 – two intersecting inclined arches - the supporting contour; 4 – guys used as a fencing frame; 5 – front inclined arch; 6 – rear support arch supported on the wall; 7 – supports; 8 – stands; 9 – foundations; 10 – foundation for the wall; 11 – pick-up cables; 12 – guy lines; 13 – anchors; 14 – masts for the upper support of pick-up cables; 15 – horizontal coverage

Rice. 13.59.

A - two-band on a round plan above the audience (USA); b – the same, above the Yubileiny Sports Palace in St. Petersburg; 1 – load-bearing cables; 2 – stabilizing shrouds; 3 – spacers; 4 – central drum with a lantern; 5 – support contour; 6 – racks; 7 – stands; 8 – guy lines; 9, 10 – ring stiffening connections; 11 – suspended platform for equipment

Membrane shells are the most effective among hanging structures, as they combine load-bearing and enclosing functions. They consist of thin metal sheets attached to a contour. Using steel with a thickness of only 2–5 mm as a material, they can cover spans of over 300 m. The membrane works mainly in tension in two directions. Thus, the danger of loss of stability is eliminated. The forces from the span structure are perceived by a closed support loop, working together with the membrane, which in most cases ensures its stability. The maximum span (224 x 183 m) is covered with a metal membrane covering over the Olympic Sports Palace in Moscow. In Fig. 13.60 shows a general view and the installation process of the membrane shell over the skating center in Kolomna.

Rice. 13.60.

A - architectural layout of the complex; b – supply of rolled membrane panels, their rolling onto temporary bed elements

Awning coverings are used as temporary structures of large spans - circus tents, warehouses, sports and exhibition pavilions. Depending on the type of soft material, such structures can also be used for critical structures. An example is the Olympic facilities in Munich (Germany), which were built for the 1972 Olympics, but have been in excellent use for 40 years. The coating material is a special translucent flexible organic glass - plexiglass-215. This is a pre-stressed material, in appearance no different from ordinary organic glass.

Pneumatic structures starting from the second half of the 20th century. widely used for temporary structures that require quick installation and dismantling (temporary warehouses, exhibition pavilions). In recent years, such structures have begun to be used for the mass construction of gyms. Such structures are also used for formwork in the construction of monolithic reinforced concrete shells. The structures are made of airtight rubberized fabric, synthetic films or other soft, airtight materials. The structure occupies its design position due to the excess pressure of the air filling it. Distinguish air-supported And pneumatic frame structures (Fig. 13.61).

Rice. 13.61.

a, b – air-supported; V – pneumatic lens; G – a fragment of a quilted design; d, f – frame pneumatic vaulted coverings; and – pneumatic arched dome; 1 – airtight shell; 2 – window-porthole made of organic glass; 3 – corkscrew anchors for fastening to the ground; 4 - Gateway; 5 – heavy stitching; 6 – steel lens support belt; 7 – stretching to provide longitudinal stability and support for the covering awning

The design position of the air-supporting structure is ensured by a very slight excess pressure (0.002–0.01 atm), which is not felt by people in the room. To maintain excess pressure, entrances to the premises are made through special airlocks with hermetic doors. The engineering equipment system includes fans that, if necessary, pump air into the room. Typical spans are 18–24 m. But there are projects in Canada to cover entire cities in the Arctic with air-supported shells with a span of up to 5 km or more. Pneumatic frames (air-carrying systems) are made of long narrow cylinders in which excess pressure is created (0.3–1.0 atm). The structural form of such a frame is arched. The arches are installed close to each other, forming a continuous arch, or at a distance. The pitch of the arches is 3–4 m, the span is 12–18 m.