Structural diagrams of buildings using long-span structures. History and prospects for the development of long-span structures. Specialists in engineering and construction monitoring

By functional purpose Long-span buildings can be divided into:

1) public buildings (theatres, exhibition pavilions, cinemas, concert and sports halls, indoor stadiums, markets, train stations);

2) special purpose buildings (hangars, garages);

3) industrial buildings (aviation, shipbuilding and machine-building plants, laboratory buildings of various industries).

Load-bearing structures according to the design diagram are divided into:

Block,

Arched,

Structural,

Dome,

Hanging,

Mesh shells.

The choice of one or another scheme of load-bearing structures of a building depends on a number of factors: the span of the building, the architectural and planning solution and the shape of the building, the presence and type of suspended transport, requirements for the rigidity of the coating, type of roof, aeration and lighting, base for foundations, etc. .

Structures with large spans are objects individual construction, their architectural and design solutions are very individual, which limits the possibilities of typing and unifying their designs.

The structures of such buildings operate mainly under loads from the structure’s own weight and atmospheric influences.

1.1 Beam structures

Beam long-span roofing structures consist of main load-bearing transverse structures in the form of flat or spatial trusses (truss span from 40 to 100 m) and intermediate structures in the form of ties, purlins and roofing.

According to the outline of the farm there are: with parallel belts, trapezoidal, polygonal, triangular, segmental (see diagrams in Fig. 1).

Truss height hf=1/8 ÷ 1/14L; slope i=1/ 2 ÷ 1/15.

Triangular trusses hf= 1/12 ÷ 1/20L; slope of belts i=1/5 ÷ 1/7.

Fig. 1 - Schemes of construction trusses

Truss cross sections:

When L > 36m, one of the supports of the beam truss is installed movable.

Coverage layout- vertical and horizontal connections along the coating are solved similarly to industrial buildings with roof trusses.

A) normal layout

wall

b) complicated layout - with rafter trusses:

PF

Beam coating schemes are used:

For any type of supporting structures- brick or concrete walls, columns (metal or reinforced concrete);

When supporting structures cannot absorb thrust forces;

When constructing buildings on subsidence or karst soils and undermined areas.

It should be noted that beam roofing schemes are heavier than frame and arched ones, but are easy to manufacture and install.

The calculation of trusses is carried out using the methods of structural mechanics (similar to the calculation of trusses industrial buildings).

1.2 Frame structures

Frame structures for building roofs are used for spans

L=40 - 150m, with a span L > 150m they become uneconomical.

Advantages of frame structures Compared to beams, this means less weight, greater rigidity and lower height of the crossbars.

Flaws- large width of columns, sensitivity to uneven settlements of supports and changes in T o.

Frame structures are effective when the linear stiffness of the columns is close to the linear stiffness of the crossbars, which makes it possible to redistribute the forces from vertical loads and significantly lighten the crossbars.

When covering large spans, as a rule, double-hinged and hingeless frames of a wide variety of shapes are used (see Fig. 2).

Rice. 2 - Schemes of through frames

Hingeless frames are more rigid and economical in terms of material consumption, however, they require the construction of powerful foundations and are sensitive to changes in temperature.

For large spans and loads, the frame crossbars are designed as heavy trusses; for relatively small spans (40-50m) they have the same sections and components as light trusses.

The cross sections of the frames are similar to beam trusses.

Frame and cover layout from frame structures is similar to the solution of frames of industrial buildings and beam coverings.

Static calculations of frame structures are performed using structural mechanics methods and specially developed computer programs.

Heavy through frames are designed as lattice systems, taking into account the deformation of all lattice rods.

1.3 Arched structures

Arched roofing structures long-span buildings turn out to be more economical in terms of material consumption than beam and frame systems. However, a significant thrust arises in them, which is transmitted through the foundations to the ground or a tightening is arranged to absorb it (i.e., extinguishing the thrust within the system).

The patterns and outlines of arches are very diverse: double-hinged, three-hinged, hingeless (see Fig. 3).

The most favorable height of the arches: f=1/4 ÷ 1/6 span L.

Arch section height:

Solid wall 1/50 ÷ 1/80 L,

Lattice 1/30 ÷ 1/60 L.

Fig.4- Schemes of supporting hinges of arches and frames (a - tiled,

b - fifth wheel, c - balancer:

1 - plate, 2 - axle, 3 - balancer).

Rice. 5- Key hinges and arches

(a - tile; b - balanced; c - sheet; d - bolted)

After determining M, N, Q, the sections of the arch rods are selected in the same way as the sections of the stubble trusses:

1.4 Spatial structures of coverings of long-span buildings

In beam, frame and arched roofing systems consisting of individual load-bearing elements, the load is transmitted only in one direction - along the load-bearing element. In these coating systems, the load-bearing elements are connected to each other by light connections, which are not intended to redistribute loads between the load-bearing elements, but only ensure their spatial stability, i.e. with their help, hard disk coverage is provided.

In spatial systems, connections are strengthened and involved in the distribution of loads and their transfer to supports. The load applied to the spatial structure is transmitted in two directions. This design is usually lighter than a flat one.

Spatial structures can be flat (slabs) and curved (shells).

To ensure the necessary rigidity, flat spatial systems (excluding hanging ones) must be double-belted - forming a mesh system along the surface. Double-belt structures have two parallel mesh surfaces connected to each other by rigid connections.

Single-layer structures with a curved surface system are called single-mesh.

In such designs, the principle of material concentration is replaced by the principle of multiply connected systems. The manufacture and installation of such structures is very labor-intensive and requires special manufacturing and installation techniques, which is one of the reasons for their limited use.

1.5 Spatial grid systems of flat coverings

In construction, mesh systems of regular structure, the so-called structural designs or simply structures, which are used in the form of flat coverings of long-span public and industrial buildings.

Flat structures are structures formed from various systems of cross trusses (see Fig. 6):

1) Structures formed from cross trusses running in three directions. Therefore, they are the most rigid, but more difficult to manufacture. These are structures with belt meshes of scalene triangles.

2) Structures formed from trusses running in two directions. These are structures with belt meshes made of square cells.

3) Structures formed from trusses, also running in two directions, but reinforced with diagonals in the corner areas. That's why they are tougher.

Advantages of structures:

Greater spatial rigidity: large spans can be covered with different support contours or column grids; obtain expressive architectural solutions at the height of the structure.

Hstructures=1/12 - 1/20 L

Repeatability of rods - from standard and same type of rods it is possible to mount coverings of different spans and plan configurations (rectangular, square, triangular and curved).

Allows you to attach suspended transport and change the direction of its movement if necessary.

Structural roofing systems can be either single-span or multi-span, supported by both walls and columns.

The installation of cantilever overhangs behind the line of supports reduces the calculated span bending moment and significantly facilitates the construction of the coating.

Rice. 6- Diagrams of structural covering grids (a - with belt meshes made of equilateral triangular cells; b - with belt meshes made of square cells; c - the same, reinforced with diagonals in conditional zones: 1 - upper chords,

2 - lower chords, 3 - inclined braces, 4 - upper diagonals, 5 - lower diagonals, 6 - support contour).

Disadvantages of structures- increased complexity of manufacturing and installation. Spatial joints of rods (see Fig. 7) are the most complex elements in structures:

Ball insert (a);

On screws (b);

A cylindrical core with slots, tightened with one bolt and washers (c, d);

Welded assembly of flattened ends of rods (e).

Rice. 7 - Interface nodes for structure rods

Structural structures are repeatedly statically indeterminate systems. Exact calculation they are complex and executed on a computer.

In a simplified approach, structures are calculated using structural mechanics methods - as isotropic slabs or as systems of cross trusses without taking into account torques.

The magnitudes of moments and shear forces are determined using tables for calculating slabs: M slabs; Qplates - then proceed to the calculation of rods.

1.6 Shell coatings

For building coverings, single-mesh, double-mesh cylindrical shells and double-curvature shells are used.

Cylindrical shells (see Fig. 8) are made in the form of arches with support:

a) rectilinear generatrix of the contour

b) on the end diaphragms

c) on end diaphragms with intermediate supports

Fig.8- Schemes for supporting cylindrical shells (1 - shell;

2 - end diaphragm; 3 - connections; 4 - columns).

Single-mesh shells are used for spans B of no more than 30 m.

Double mesh - for large spans B>30m.

On the cylindrical surface there are rods that form meshes of various systems (see Fig. 9):

Diamond mesh (a);

Rhombic mesh with longitudinal ribs (b);

Rhombic mesh with transverse ribs (c);

Rhombic mesh with transverse and longitudinal ribs (d).

The simplest mesh of a rhombic pattern, which is obtained from light standard rods (∟, ○, □) of rolled profiles. However, this scheme does not provide the necessary rigidity in the longitudinal direction when transferring the load to the longitudinal walls.

Rice. 9 - Mesh system of single mesh shells

The rigidity of the structure increases significantly in the presence of longitudinal rods (diagram “b”) - the structure can work as a shell with span L. In this case, the support can be end walls or four columns with end diaphragms.

The most rigid and advantageous are the meshes (pattern “c”), which have both longitudinal and transverse ribs (rods), and the mesh lattice is directed at an angle of 45.

Calculation of shells is performed using methods of elasticity theory and methods of shell theory. Shells without transverse ribs calculated as momentless folds (Ellers method). If there are transverse ribs, ensuring the rigidity of the contour - according to Vlasov’s moment theory (it comes down to solving eight-term equations).

When calculating through mesh shells, through faces of structures are replaced by solid plates of equivalent thickness when working in shear, axial tension and compression.

More accurate calculations of mesh shells are performed on a computer using specially developed programs.

Double mesh shells used when covering spans with a width of more than B>30m.

Their structural diagrams are similar to those of two-mesh flat slabs - structures. As in structures, they are formed by systems of cross trusses connected along the upper and lower chords by special connections - a lattice. But at the same time, in shells, the main role in the perception of forces belongs to curved mesh planes; the lattice connecting them is less involved in the transmission of forces, but gives the structure greater rigidity.

Compared to single-mesh shells, double-mesh shells have greater rigidity and load-bearing capacity. They can cover spans of buildings from 30 to 700 m.

They are designed in the form of a cylindrical surface, supported by longitudinal walls or metal columns. At the ends of the shell they rest on rigid diaphragms (walls, trusses, arches with a tie, etc.).

The best distribution of forces in the shell is at B=L.

The distance between the mesh surfaces is h=1/20÷1/100R at f/B=1/6÷1/10.

As in structures, the most complex is the joint of the rods.

Calculation of two-mesh shells is carried out on a computer using specially designed programs.

For an approximate calculation of the shell, it is necessary to reduce the rod system to an equivalent solid shell and establish the shear modulus of the middle layer, which is equivalent in rigidity to the connecting lattice.

1.7 Dome coverings

There are four types of dome structures (see Fig. 6): ribbed (a), ribbed-ring (b), mesh (c), radial-beam (d).

Rice. 10- Dome schemes

Ribbed domes

The structures of ribbed domes consist of individual flat or spatial ribs in the form of beams, trusses or semi-arches, located in the radial direction and interconnected by girders.

The upper belts of the ribs form the surface of the dome (usually spherical). The roof is laid along the purlins.

At the apex, to reconnect the ribs, a rigid ring is installed that works for compression. The ribs can be hinged or rigidly attached to the central ring. A pair of dome ribs located in the same diametrical plane and interrupted by a central ring is considered as a single, for example arched, structure (two-hinged, three-hinged or hingeless).

Ribbed domes are spacer systems. The expansion is perceived by walls or a special spacer ring in the shape of a circle or polyhedron with rigid or hinged joints in the corners.

Between the ribs, ring purlins are laid at a certain pitch, on which the roofing deck rests. Shoulder straps, in addition to their main purpose, provide general stability of the upper belt of the ribs out of the plane, reducing their design length.

To ensure the overall rigidity of the dome in the plane of the purlins, pitched connections between the ribs are arranged at a certain pitch, as well as vertical connections to decouple the internal belt of the arch - spacers are arranged between the vertical connections.

Design loads- own weight of the structure, weight of equipment and atmospheric influences.

The design elements of the dome cover are: ribs, support and central rings, purlins, pitched and vertical connections.

If the expansion of the dome is perceived by a spacer ring, then when calculating the arch, the ring can be replaced by a conditional tightening located in the plane of each pair of semi-arches (forming a flat arch).

When calculating the support ring - with a frequent arrangement of arches (ribs) of the dome, the action of their thrusts can be replaced by an equivalent uniformly distributed load:

Ribbed-ring domes

In them, shoulder straps with ribs form one rigid spatial system. In this case, the annular girders work not only in bending from the load on the coating, but also from the reactions of the intermediate ribs and perceive tensile or compressive annular forces arising from thrusts at the point of support of the multi-span semi-arches.

The weight of the ribs (arches) in such a dome is reduced due to the inclusion of ring girders as intermediate support rings. The annular ribs in such a dome work in the same way as the support ring in a ribbed dome, and when calculating arches they can be replaced by conditional tightening.

With a symmetrical load, the calculation of the dome can be carried out by dividing it into flat arches with ties at the level of the annular ribs (purlins).

Mesh domes

If you increase the connectivity of the system in a ribbed or ribbed-ring dome, you can get mesh domes with hinged connections of the rods at the nodes.

In mesh domes, between the ribs (arches) and rings (ring purlins) there are braces, thanks to which the forces are distributed over the surface of the dome. In this case, the rods work mainly only on axial forces, which reduces the weight of the ribs (arches) and rings.

The rods of mesh domes are made of closed profiles (round, square or rectangular cross-section). Joints of rods as in structures or mesh shells.

Mesh domes are calculated on a computer using specially developed programs.

They are approximately calculated according to the momentless theory of shells - as a continuous axisymmetric shell using formulas from the corresponding theoretical reference books.

Radial beam domes

They are ribbed domes made up of segmented semi-trusses arranged radially. In the center, segmental semi-trusses are attached to a rigid ring (lattice or solid-wall with stiffening diaphragms).

1.8 Hanging coverings

Hanging coatings are those in which the main load-bearing elements work in tension.

These elements make full use of high-strength steels, since their load-bearing capacity is determined by strength rather than stability.

Load-bearing stretched rods - cables - can be made flexible or rigid.

Hard- made from curved I-beams.

Flexible- made of steel ropes (cables) twisted from high-strength wire with R = 120 kN/cm2 ÷ 240 kN/cm2.

Hanging roof structures are one of the most promising structural forms for the use of high-strength materials. The structural elements of hanging roofs are easy to transport and relatively easy to install. However, the construction of suspended coverings has a number of difficulties, the successful engineering solution of which determines the effectiveness of the covering as a whole:

First drawback- hanging coverings are expansion systems and to absorb the thrust, a supporting structure is required, the cost of which can be a significant part of the cost of the entire covering. Reducing the cost of supporting structures can be achieved by increasing the efficiency of their work - creating coverings of round, oval and other non-rectilinear plan shapes;

second drawback- increased deformability of hanging systems. This is due to the fact that the modulus of elasticity of twisted cables is less than that of rolled steel (Etrosa = 1.5 ÷ 1.8 × 10 5 MPa; E of rolled rods = 2.06 × 10 5 MPa), and the elastic work area of ​​high-strength steel is much larger than that of ordinary steel. Thus, the relative deformation of the cable in the elastic stage of work, ε = G/E, is several times greater than for elements made of ordinary steel.

Most suspended covering systems are instant stiffening systems, i.e. systems that work elastically only under equilibrium loads, and under the action of uneven loads in them, in addition to elastic deformations, kinematic displacements of the system also appear, leading to a change in the integrity of the geometric coating system.

To reduce kinematic movements, suspended coating systems are often equipped with special stabilizing devices and pre-stressed.

Types of Hanging Schemes

1. Single-belt systems with flexible cables

Such coating systems are designed rectangular or curved in plan, for example, round (see Fig. 11).

They are prestressed reinforced concrete shells that work in tension. The stressed reinforcement in them is a system of flexible cables, on which prefabricated reinforced concrete slabs are laid during installation. At this time, an additional weight is placed on the cables, which is removed after laying all the reinforced concrete slabs and sealing the seams. The cables compress the reinforced concrete slabs and the resulting reinforced concrete shell receives a preliminary compressive stress, allowing it to absorb tensile stress from external loads and ensure the overall stability of the structure. The load-bearing capacity of the coating is ensured by the tension of the cables.

In rectangular roofs, the thrust of the cables is absorbed by a supporting structure of guys and anchors fixed in the ground.

Rice. eleven- Single-belt coverings with flexible cables

(a - rectangular in plan; b - round in plan)

In round (oval) plan coverings, the thrust is transmitted to the outer compressed ring lying on the columns and the inner (stretched) ring. metal ring.

The sag of the cables of such coverings is usually f=1/10÷1/20 L. Such shells are flat.

The cross-section of the roof cables is determined by the installation load. In this case, the cables work as separate threads, and the expansion in them can be determined without taking into account their deformations H=M/f, where M is the beam moment from the design load, f is the sag of the thread.

where V is the beam reaction.

2. Single-belt systems with rigid cables

Rice. 12- 1 - longitudinal flexural-rigid ribs; 2 - transverse ribs;

3 - aluminum membrane, t = 1.5 mm

In such coverings, bent rigid cables attached to the support belt operate under the action of a tensile load with bending. Moreover, under the action of a uniform load, the proportion of bending in stresses is small. Under the action of an uneven load, rigid cables begin to strongly resist local bending, which significantly reduces the deformability of the entire coating.

The sag of the cables of such coverings is usually 1/20 ÷ 1/30 L. However, the use of rigid threads is possible only for small spans, because As the span increases, installation becomes significantly more complicated and their weight increases. Such rigid cables can be used to lay a lightweight roof; there is no need for prestressing (its role is played by the flexural rigidity of the cable).

With a uniform load, the thrust in the cable stay is determined by the formula

H = 8/3 ×[(EA)/(l 2 mо)] × (f+fо) × ∆f +Ho;

where ∆f=f–fо,

f - deflection under load,

fo – initial sag;

m1=1+(16/3)/(fo/l) 2

The bending moment in the middle of the cable is found by the formula

M= q I 2 /8–Hf.

3. Single-belt hanging coverings, tensioned using cross beams or farms

Rice. 13

Stabilization of such cable-beam systems is achieved either by an increased mass of transverse and flexurally rigid elements, or by prestressing guy wires that connect transverse beams or trusses to foundations or supports. Light roof coverings are tensioned in this way.

Thanks to the bending rigidity of the transverse beams or trusses, the coating acquires spatial rigidity, which is especially evident when the span structure is loaded with local load.

4. Two-belt systems

Rice. 14

Coatings of this type have two cable systems:

- Bearers- having a downward bend;

- Stabilizing- having an upward bend.

This makes such a system instantly rigid - capable of absorbing loads acting in two different directions. The vertical load causes the supporting thread stretching, and for the stabilizing one - compression. The wind suction causes forces of the opposite sign in the cables.

Light roofs can be used in this type of coating.

5. Saddle-shaped strained meshes

Rice. 15

Coatings of this type are used for permanent buildings and temporary structures.

Covering mesh: The supporting (longitudinal) cables are curved downwards, the stabilizing (transverse) cables are curved upwards.

This form of coating allows the mesh to be pre-stressed. The coating surface is light and made from various materials: from steel sheet to film and awning.

The grid spacing is approximately one meter. Accurate calculation of the meshes of such coatings is possible only on a computer.

6. Metal shell membranes

Rice. 16

The shape in plan is an ellipse or a circle, and the shape of the shells is quite diverse: cylindrical, conical, bowl-shaped, saddle-shaped and tent-shaped. Most of them work according to a spatial scheme, making it very profitable and allowing the use of sheets with a thickness of 2 - 5mm.

The calculation of such systems is carried out on a computer.

Main advantage Such coating systems are a combination of load-bearing and enclosing functions.

Insulation and waterproofing are laid on the supporting shell without using roofing slabs.

Shell panels are produced at the manufacturing plant and delivered for installation in the form of rolls, from which the entire shell is assembled at the construction site without the use of scaffolding.

Section 2. Sheet structures

Sheet structures are structures consisting mainly of metal sheets and intended for storing and transporting liquids, gases and bulk materials.

These designs include:

Tanks for storing petroleum products, water and other liquids.

Gas tanks for storage and distribution of gases.

Bunkers and silos for storage and handling of bulk materials.

Large diameter pipelines for transporting liquids, gases and crushed or liquefied solids.

Special designs for metallurgical, chemical and other industries:

Blast furnace casings

Air heaters

Dust collectors - scrubbers, housings for electrostatic precipitators and bag filters

Smoke pipes

Solid wall towers

Cooling towers, etc.

Such sheet structures occupy 30% of all metal structures.

Operating conditions for sheet structures quite varied:

They can be above-ground, above-ground, semi-buried, underground, underwater;

Can withstand static and dynamic loads;

Work under low, medium and high pressure;

Under the influence of low and high temperatures, neutral and aggressive environments.

They are characterized by a two-basic stress state, and in places where they are coupled with the bottom and stiffeners, in places where shells of different curvature are coupled (i.e., at the boundary of changes in the radius of curvature), local high voltage, quickly attenuating as they move away from these areas - this is the so-called edge effect phenomenon.

Sheet structures always combine load-bearing and enclosing functions.

Welded joints of elements of sheet structures are made end-to-end, overlapping and end-to-end. Connections are made using automatic and semi-automatic arc welding.

Most sheet structures are thin-walled rotation shells.

Shells are calculated using the methods of elasticity theory and shell theory.

Sheet structures are designed for strength, stability and endurance.

1.1 Reservoirs

Depending on their position in space and geometric shape, they are divided into cylindrical (vertical and horizontal), spherical and teardrop-shaped.

Based on their location relative to the planning level of the earth, they are distinguished: above-ground (on supports), above-ground, semi-buried, underground and underwater.

They can be of constant and variable volumes.

The type of tank is selected depending on the properties of the stored liquid, operating mode, and climatic characteristics of the construction area.

Most widespread received vertical and horizontal cylindrical tanks as the easiest to manufacture and install.

Vertical tanks with fixed roof are low-pressure vessels in which petroleum products are stored with low turnover (10 - 12 times a year). They generate excess pressure in the steam-air zone of up to 2 kPa, and when emptying, a vacuum (up to 0.25 kPa).

Vertical tanks with floating roof and pontoon used for storing petroleum products with high turnover. There is practically no excess pressure and vacuum in them.

High-pressure tanks (up to 30 kPa) are used for long-term storage of petroleum products with their turnover no more than 10 - 12 times a year.

Spherical tanks- for storing large volumes of liquefied gases.

Drop-shaped tanks- for storing gasoline with high vapor pressure.

Vertical tanks

Rice. 17

Essential elements:

Wall (body);

Roof (coverings).

All structural elements are made of sheet steel. They are easy to manufacture and install, and are quite economical in terms of steel consumption.

Installed optimal sizes vertical cylindrical tank of constant volume, at which the metal consumption will be the least. Thus, a tank with a wall of constant thickness has a minimum mass if

[(mdn + mpok) / mst] = 2, and the value of the optimal tank height is determined by the formula

where V is the volume of the tank,

∆= t day+t add. cover - the sum of the reduced thickness of the bottom and coating,

tst. - thickness of the housing wall.

In large-volume tanks, the wall thickness varies in height. The mass of such a tank will be minimal if the total mass of the bottom and cover is equal to the mass of the wall, i.e. mday + mcover = mst.

In this case

where ∆= tday. + tpriv. cover,

n - overload factor,

γ f. - specific gravity of the liquid.

Tank bottom

Since the bottom of the tank rests over its entire area on a sandy base, it experiences minor stresses from liquid pressure. Therefore, the thickness of the bottom sheet is not calculated, but is taken structurally, taking into account ease of installation and corrosion resistance.

At V≤1000m and D<15м → tдн = 4мм; при V>1000m and D=18-25m → tdn = 5mm; at D > 25m → tdn = 6mm. Rice. 18

The sheets of the bottom panels are connected to each other along the longitudinal edges with an overlap with an overlap of 30 - 60 mm at tday. = 4 - 5mm, and when tday = 6mm - they are performed end-to-end. The outer sheets - “edges” - are 1-2mm thicker than the sheets in the middle part of the bottom. Everything is supplied from the manufacturer in rolls (Q ≤ 60t).

Wall construction:

Rice. 19

The tank wall consists of a number of belts with a height equal to the width of the sheet. The belts are connected to each other end-to-end or overlapped in a telescopic or stepwise manner. Butt mating is performed mainly at the manufacturer's factory (less often during installation), while lap jointing is performed both at the factory and during installation.

A common method for constructing tanks is by rolling.

Strength calculation- the housing wall is a load-bearing element and is calculated using the limit state method in accordance with the requirements of SNiP 11-23-81

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 the majority 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.

At the end of the 18th century. appeared new material 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 Wood has good load-bearing properties ( design resistance pine for compression and bending 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 of 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, best 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 the internal physical and mechanical properties of the material and the 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 made, as a rule, 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. The maximum length of the designed reinforced concrete trusses is about 100 m at a pitch 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 HDD coverings. 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 a 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 made of nailed or glued elements for spans 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 the construction of buildings 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 from 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 an appropriate shape, the desire to minimize their weight, the search optimal conditions distribution of loads, 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 construction production and high quality of all construction work.

Of course, it is impossible to give recommendations on the use of certain coating structures for each specific case. 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 relevant 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 The application of a flat folded structure of a sawtooth profile is the coating of the laboratory of the Concrete Institute in Detroit (USA) with a size of 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 a variety of halls with different functional purposes.

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 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 design 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 under 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 industrial assembly 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, d).

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 beneficial, in the sense constructive work, the construction 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 outermost 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. The design features of 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 lakeside restaurant 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 mushroom stems 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 shells of single curvature to shells of double curvature marks new stage in the development of shells, since the effect of bending forces in them is minimized.

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 the 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, d).

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 recent years, the first domed buildings with retractable roofs have 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 countries 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 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 practical use They found them in the works 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 stiffening ribs located parallel to the sides of the square every 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 runs. 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 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 braces (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 due 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. the optimal sag value 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 a supporting and stabilizing cable with curvature different sign. 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);

Transmitting thrust through guy ropes is the most economical way to absorb 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 of 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 designs, it became possible to simplify the design diagram and thereby obtain 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). The main structural material of cable-stayed coverings is 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. The following methods of anti-corrosion protection of cables are possible: galvanizing, paint coatings or lubricants, covering with a plastic shell, covering with a shell of rice steel with injection of bitumen or cement mortar into the shell, 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.

IN different countries, including in our country, dozens of pneumatic structures for various purposes have been erected. 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 capital structures, continuous concrete base, on which the shell is fixed. 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. fresh for this concrete mixture laid on a reinforcement frame 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 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 stationary structures structures. 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. 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 wide opportunities for various functional organization of buildings, at improving 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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LECTURE NOTES

Makeevka 2011

MINISTRY OF EDUCATION AND SCIENCE, YOUTH AND SPORTS OF UKRAINE

DONBASS NATIONAL ACADEMY OF CONSTRUCTION AND ARCHITECTURE

Department of “Enterprise Economics”

Developed by: Ph.D., Associate Professor. Zakharchenko D.A.

LECTURE NOTES

in the course "Fundamentals of the construction industry"

for students of specialty 6.030504 “Enterprise Economics”

Code No. _______

Approved at a department meeting

"Enterprise Economics"

PROTOCOL No. __ dated _______2011

Makeevka 2011

TOPIC 4. LONG-SPAN BUILDINGS AND STRUCTURES

Long-span structures include those that have spans of more than 40-80 m. Relatively recently, such structures were considered unique and were built extremely rarely; currently, the rapid development of science and technology, as well as the great need for such structures in industry and the sphere of leisure and entertainment, have predetermined intensive construction of such structures in many countries.

Of particular interest are spatial structures that do not consist of separate, independent load-bearing elements that transfer each other’s load, but represent a single complex system working parts of the structure.

This spatial nature of structures, widely introduced into construction throughout the world, is a symbol of 20th century construction technology. And although some types of spatial structures - domes, crosses and vaults - have been known since ancient times, they do not meet modern construction requirements either in terms of the use of materials or design solutions, since although they covered significant spans, they were also extremely heavy and massive.

What is attractive about spatial designs is their ability to optimally satisfy the functional and aesthetic requirements of architecture. The scale of overlapped spans, the ability to implement flexible planning, a variety of geometric shapes, materials, architectural expressiveness - this is not a complete list of the features of these structures.

The combination of functional, technical and artistic-aesthetic provides spatial structures with a broad perspective, not to mention the fact that their use allows for huge savings in building materials - reducing the material consumption of buildings and structures by 20-30%.

Planar long-span structures include beams, frames, trusses, and arches. Planar structures operate autonomously under load, each in its own plane. Load-bearing element planar structures covering some area of ​​the building (slab, beam, truss) work independently and do not participate in the work of the elements to which it is adjacent. This causes lower spatial rigidity and load-bearing capacity of planar elements compared to spatial ones, as well as their higher resource consumption, primarily increased consumption of materials.

Rice. 4.1. Design solutions for long-span structures

A - flat designs; b - spatial structures; c - hanging structures; g - pneumatic structures; 1- farms; 2 - frames; 3-4 articulated arches; 5- cylindrical shells; 6- shells of double curvature; 7- domes; 8- structures; 9- cable-stayed structures; 10-membrane structures; 11- awning structures; 12- pneumatic support structures; 13- pneumatic frame structures;

The frames of a solid structure are installed using two self-propelled jib cranes. First, frame racks with a part of the crossbar are installed on the foundation, resting on a temporary support, and then the middle section of the crossbar is mounted. The parts of the crossbar are connected on temporary supports by welding or strong welding. After installing the first frame, the structure is braced using guy wires.

In some cases, it is advisable to install frame structures using the sliding method. This method is used if frame structures cannot be immediately installed in the design position (work is underway inside or structures have already been erected that do not allow the placement of cranes).

The block is assembled at the end of the building in a special conductor of 2-3 or 4 trusses. The assembled and secured block is lifted along the rail tracks to the design position. Install using jacks or light cranes.

Arched structures are of 2 types: in the form of a 2-hinged arch with a tightening and a 3-hinged arch. When installing arched structures with a load-bearing part in the form of a double-hinged arch, it is carried out similarly to the installation of frame structures using self-propelled jib cranes. The main requirement is high installation accuracy, guaranteeing alignment of the fifth (support) hinge with the support.

The installation of three-hinged arches differs in some features related to the presence of an upper hinge. The latter is assembled using a temporary mounting support installed in the middle of the span. Installation is carried out using the vertical lifting method, sliding or turning methods.

Rice. 4.3. Frame installation

a - installation entirely by two cranes; b - installation of frames in parts using temporary supports; c - installation of frames using the rotation method; 1-installation crane; 2-frame assembly; 3-piece frame; 4-temporary supports; 5 winches; 6-mount booms.

Each semi-arch is slung at the center of gravity and installed so that the heel hinge is placed on a support, and the second end is placed on a temporary support. The same with the other half-arch. Rotation in the heel hinge is achieved by aligning the axes of the locking holes of the upper hinge.

In spatial structures, all elements are interconnected and participate in the work. This leads to a significant reduction in metal consumption per unit area. However, until recently, such spatial systems (dome, cable-stayed, structural, shells) were not developed due to the high complexity of manufacturing and installation.

Rice. 4.4. Mounting the Dome Using a Temporary Center Support

A - dome cutting system; B - installation of the dome; 1-temporary support with guy wires; 2-radial panels; 3-support ring;

Dome systems are mounted from individual rods or individual plates. Depending on the design solution, installation of dome structures can be carried out using a temporary stationary support, in a hinged way or in its entirety.

Spherical domes are erected in ring tiers using a hanging method. Each such tier, after complete assembly, has statistical stability and load-bearing capacity and serves as the basis for the overlying tier. Prefabricated domes can be mounted using conductor devices and temporary fastenings - a circus dome in Kyiv, or the dome is assembled entirely on the ground and then lifted to the design horizon by crane, pneumatic transport or lift. The method of growing from below is used.

Hanging structures began to be used from the 2nd half of the 19th century. And one of the first examples is the covering of the pavilion of the All-Russian Nizhny Novgorod Fair, completed in 1896. the outstanding Soviet engineer Shukhov.

The experience of using such systems has proven their progressiveness, since they make it possible to make maximum use of high-strength steels and lightweight enclosing structures made of plastics and aluminum alloys, which makes it possible to create coverings of significant spans.

Rice. 4.5. Installation of hanging structures

1-tower crane; 2-traverse; 3-cable half-truss; 4-central drum; 5-temporal support; 6-mounted semi-truss; 7 - support ring.

Recently, hanging frame structures have become widespread. The peculiarity of the construction of suspended structures is that first, load-bearing supports are erected, on which a support contour is laid, which absorbs the tension from the cable strands. After they are completely laid out, the coating is loaded with a temporary load taking into account the full design load. This method of prestressing prevents the appearance of cracks in the shell after its full load during operation.

A type of suspended cable-stayed structures are membrane coverings. The membrane covering is a hanging system in the form of a thin metal sheet structure stretched over a reinforced concrete support contour. One end of the roll is fixed to the support contour, and the roll is unwound to its entire length using a special traverse by a crane, pulled by winches and secured to the opposite section of the support contour.

The disadvantage of membrane coatings is the need to weld thin sheets along the length and mounting elements together with an overlap of 50 mm. At the same time, it is almost impossible to obtain a seam of equal strength with the base metal by welding, so the thickness of the sheet is artificially increased. This problem is solved to some extent by a system of interlocking tapes made of aluminum alloys.

The first long cylindrical shells were first used in 1928. in Kharkov during the construction of a post office.

Long cylindrical shells are supplied fully finished or enlarged on site. The weight of 3x12 mounting elements is about 4 tons. Before lifting, two plates are enlarged in a mobile jig together with tightening into one element. When enlarging, the embedded parts are welded at the joint, the tightening is tightened and the seams are sealed.

Having installed 8 enlarged sections forming a span of 24 m, they are aligned so that the holes coincide, then all the embedded parts and outlets of the longitudinal reinforcement are welded, the reinforcement is tensioned and the joints are concreted. After the concrete has cured, the shell is turned around and the scaffolding is rearranged.

In construction practice, spatial, cross, ribbed and bar structures are usually combined under the name structural structures.

Cross systems of structural coatings of various shapes with rectangular and diagonal gratings have become widespread relatively recently since the second half of the 20th century in countries such as the USA, Germany, Canada, England, and the former USSR.

For some time, structural structures were not widely developed due to the high labor intensity of manufacturing and the peculiarities of installation of the structure. Improvement of the design, especially with the use of computers, made it possible to ensure the transition to their in-line production, reduce the complexity of their calculations, increase its accuracy and, therefore, reliability.

Fig.4.6. Covering a building from large-size slabs

1-slab measuring 3x24m; 2-anti-aircraft lamp; 3-rafter truss; 4- column.

Cross-bar systems are based on a supporting geometric shape. A distinctive feature of different types of structural structures is the spatial joint of the rods, which largely determines the complexity of manufacturing and assembling these structures.

Structural structures have a number of advantages compared to traditional planar solutions in the form of frames and beam structures:

• are collapsible and can be used repeatedly;
• can be manufactured on automated production lines, which is facilitated by high typification and unification of structural elements (often one type of rods and one type of assembly are required);
• assembly does not require high qualifications;
• They have compact packaging and are convenient for transportation.

Along with the noted advantages, structural structures also have a number of disadvantages:

• large-scale assembly requires the use of a significant amount of manual labor;
• limited load-bearing capacity of certain types of structures;
• low factory readiness of structures received for installation.

Pneumatic structures are used for temporary shelter or for use for some auxiliary purposes, for example, as support structures for the construction of shells and other spatial structures.

Pneumatic coverings can be of 2 types - air-supporting and air-carrying. In the first case, a slight excess pressure of the soft shell of the structure ensures that the required shape is obtained. And this shape will be maintained as long as the air supply and the necessary excess pressure are maintained.

In the second case, the load-bearing structure is made of air-filled pipes made of elastic material, forming a kind of frame of the structure. They are sometimes called high-pressure pneumatic structures because the air pressure in the pipes is much higher than that under the air support film.

The construction of air-supporting structures begins with preparing the site on which concrete or asphalt is laid. A foundation with anchoring and compacting devices is installed along the contour of the structure. Under the influence of air pressure, the shell straightens and takes on the designed shape.

Air-carrying or pneumatic frame structures are constructed similarly to air-supported ones, with the only difference being that the air is supplied from the compressor through rubber pipes and through special valves is pumped into the closed channels of the so-called structure frame. Due to the high pressure in the chambers, the frame takes the designed position (most often in the form of arches) and lifts the enclosing fabric behind it.

Architectural appearance long-span buildings is largely determined by their role in the composition of a fragment of the surrounding urban development, the functional features of buildings and the applied coating structures.

The public functions of hall-type buildings require the allocation of significant free spaces in front of them for various purposes for: moving large flows of spectators before or after the start of shows (in front of entertainment or demonstration sports facilities); placement of the open part of the exhibition (in front of exhibition pavilions): seasonal trade (in front of covered markets), etc. In front of any of these buildings, areas are also allocated for parking individual cars. Thus, regardless of the purpose of the building, its placement in the building makes it possible to holistically perceive the volume of the structure from distant points of view. This circumstance determines the general compositional requirements for the architecture of buildings: the integrity and monumentality of their appearance and the predominantly large scale of the main divisions of the volume.

This feature of the urban planning role of hall-type public buildings is often taken into account in the composition of their appearance. Auxiliary and service premises, which can be located in separate volumes attached to the main one (as, for example, in the Yubileiny Sports Palace in St. Petersburg), for the most part are not blocked, but fit into the main volume of the building. For this purpose, auxiliary and service premises of sports buildings are located in the lower floors or in the space under the stands, in buildings of covered markets and exhibition pavilions - in the ground and basement floors, etc.

Typical examples of the implementation of such a space-planning principle of building layout are such apparently different objects as the universal Olympic Hall “Friendship” in Luzhniki in Moscow and the building of the Takamatsu Prefecture Sports Center in Niigata (Japan).

The Druzhba Hall has a main showroom with a capacity of 1.5-4 thousand spectators (if transformed) with an arena of 42X42 m, designed for 12 sports with optimal visibility of all competitions (maximum distance 68 m). The hall is covered with a flat spherical shell supported on 28 inclined supports made of prefabricated monolithic folded shells of double curvature. The inclined arrangement of the supports made it possible to increase the dimensions of the first floor and thereby accommodate four training halls and four sports grounds, inscribed in a single centrally symmetrical volume with a pronounced tectonic architectural form ( ).

Both examples show the influence of the structural form of the pavement on the architectural form. And this is no coincidence, since the coating structure makes up from 60 to 100% of the external fencing of buildings.

Among the functional parameters, the choice of the form of the coating is most influenced by the adopted plan, capacity, the nature of the placement of spectator seats (in sports and entertainment buildings) and the size of the spans of the coatings ( ). In world practice, a limited number of plan shapes are used for exhibition, multifunctional auditoriums and sports halls: rectangle, trapezoid, oval, circle, polygon.

However, the shape of the hall plan and the size of its spans do not uniquely determine the shape of the covering. Its choice is greatly influenced not only by the plan, but also by the shape of the building determined by the functional features. As is known, in demonstration sports halls the capacity and location of the stands determine the asymmetrical or centrally symmetrical composition of the building, with which the choice of the shape of the covering must be coordinated. Hanging roofs harmonize well with the asymmetrical shape of the building, and both vaulted and hanging roofs harmonize well with the axisymmetric shape. For buildings centric in plan, centric roofing structures are applicable ( , ).

The final choice of coating form, in addition to functional ones, is determined by structural, technological, technical, economic, architectural and artistic requirements. According to the latter, the design of the unique long-span building should contribute to the creation of an expressive tectonic, individual, large-scale architectural form. The introduction of spatial suspended structures and rigid shell structures has provided unprecedented and multi-variant architectural possibilities. Combining Various types, number, dimensions of elementary shells, the architect, with the help of the designer, can achieve the required large-scale division of the form and individualize its appearance, and place the overhead light openings in the covering in an original way.

So, for example, just to cover a room that is triangular in plan, a flat shell on a convex contour, a combined covering of four triangular in plan shells of positive curvature, three of negative and one of positive curvature, etc. can be used. design and expressive in architectural form is the covering of a triangular exhibition building in Paris with a combined shell in the form of a vault connected from three trays with a span of 206 m. The trays consist of two wavy shells, braced every three waves with rigidity diaphragms. The use of a wavy form made it possible to solve not only a purely constructive problem (to achieve the stability of a thin shell), but also ensured the scale of the composition of this unique building, and the closed vault system, traditional for stone architecture, received an individual and sharply modern tectonic interpretation. Equally individual and modern was the compositional interpretation of the reinforced concrete cross vault covering above the square plan of the building of the indoor Olympic skating rink in Grenoble.

Naturally, however, the most modern character of the architecture of long-span coverings with reinforced concrete rigid shells is given by their inherent combinations of geometric shapes in the form of wavy domes and vaults, elementary or combined fragments of shells with surfaces of negative curvature, or combinations of shells of arbitrary geometric shape.

The architectural and compositional capabilities of hanging roofing systems are directly related to their structural form, the possibilities of its individualization and tectonic identification in the volumetric form of the building. In this regard, the greatest potential is provided by hanging tent-type coverings, coverings on a spatial contour, as well as various options combined hanging systems. The extreme diversity of the external appearance of buildings, which is ensured by the use of hanging coverings on a closed spatial contour, can be seen by comparing such Olympic venues in Moscow as an indoor cycling track and a sports hall in Izmailovo. Unfortunately, the use of a number of technically most efficient suspended structures, for example, single- or double-belt systems with a horizontal annular support contour over round or elliptical buildings, contributes little to the individuality of the external appearance of the building. A load-bearing structure with a small sag is not visible in the external form of the building, and in the interior it is usually hidden by suspended ceilings or lighting installations. Buildings with coatings of this type usually have a composition in the form of a round peripter, the entablature of which is a ring of the supporting contour, and the columns are the pillars supporting it (Yubileiny Sports Palace and the Olympic Hall in St. Petersburg, the Olympic Sports Palace on Mira Avenue in Moscow, etc. .).

Along with the load-bearing structures of the coverings, external, usually non-load-bearing walls, play a significant role in the composition of indoor public buildings. A figurative expression of their non-load-bearing function can be their implementation with a slight deviation from the vertical, giving the building a characteristic silhouette (tapering or widening downward).

A significant part of the surface of the external walls of the hall buildings is occupied by translucent stained glass structures. Their compositional properties and divisions are enriched when two or three translucent materials are combined in the design, for example profile and sheet glass.

Long-span structures play a significant role in world architecture. And this was laid down in ancient times, when this special direction of architectural design actually appeared.

The idea and implementation of long-span projects is inextricably linked with the main desire of not only the builder and architect, but of all humanity as a whole - the desire to conquer space. That is why, starting from 125 AD. e., when the first long-span structure known in history, the Pantheon of Rome (base diameter - 43 m), appeared, and ending with the creations of modern architects, long-span structures are especially popular.

History of long-span structures

As mentioned above, the first was the Pantheon in Rome, built in 125 AD. e. Later, other majestic buildings with large-span domed elements appeared. A striking example is the Church of Hagia Sophia, built in Constantinople in 537 AD. e. The diameter of the dome is 32 meters, and it itself gives the entire structure not only majesty, but also amazing beauty, which is admired by both tourists and architects to this day.

In those and later times it was impossible to build light structures from stone. Therefore, domed structures were characterized by great massiveness and their construction required serious time expenditure - up to a hundred years or more.

Later, wooden structures began to be used to construct the floors of large spans. A striking example here is the achievement of domestic architecture - the former Manege in Moscow was built in 1812 and had wooden spans 30 m long in its design.

The 18th-19th centuries were characterized by the development of ferrous metallurgy, which gave new and more durable materials for construction - steel and cast iron. This marked the emergence in the second half of the 19th century of long-span steel structures, which were widely used in Russian and world architecture.

The next building material that significantly expanded the capabilities of architects was reinforced concrete structures. Thanks to the emergence and improvement of reinforced concrete structures, the world architecture of the 20th century was replenished with thin-walled spatial structures. At the same time, in the second half of the twentieth century, suspended coverings, rod and pneumatic systems began to be widely used.

In the second half of the twentieth century, laminated wood also appeared. The development of this technology has made it possible to “bring back to life” wooden long-span structures, to achieve special indicators of lightness and weightlessness, to conquer space, without compromising on strength and reliability.

Long-span structures in the modern world

As history shows, the logic of the development of long-span structural systems was aimed at improving the quality and reliability of construction, as well as the architectural value of the structure. The use of this type of structure made it possible to make the most of the full potential of the load-bearing properties of the material, thereby creating lightweight, reliable and economical floors. All this is especially important for a modern architect, when reducing the weight of structures and structures has come to the fore in modern construction.

But what are long-span structures? Here expert opinions differ. Single definition No. According to one version, this is any structure with a span length of more than 36 m. According to another, structures with an unsupported covering more than 60 m long, although they are already classified as unique. The latter also include buildings with a span of more than one hundred meters.

But in any case, regardless of the definition, modern architecture is clear that long-span buildings are complex objects. And this means a high level of responsibility for the architect, the need to take additional safety measures at each stage - architectural design, construction, operation.

The important point is the choice building material- wood, reinforced concrete or steel. In addition to these traditional materials, special fabrics, cables and carbon fiber are also used. The choice of material depends on the tasks facing the architect and the specifics of construction. Let's consider the main materials used in modern long-span construction.

Prospects for long-span construction

Taking into account the history of world architecture and the inevitable desire of man to conquer space and create perfect architectural forms, we can safely predict a steady increase in attention to long-span structures. As for materials, in addition to modern high-tech solutions, increasing attention will be paid to FCC, which is a unique synthesis of traditional material and modern high technology.

As for Russia, given the pace of economic development and the unmet need for facilities for various purposes, including trade and sports infrastructure, the volume of construction of long-span buildings and structures will constantly increase. And here unique design solutions, quality of materials and the use of innovative technologies will play an increasingly important role.

But let's not forget about the economic component. It is this that stands and will stand at the forefront, and it is through it that the effectiveness of a particular material, technology and design solution will be considered. And in this regard, I would again like to remember about laminated wood structures. According to many experts, they hold the future of long-span construction.