Modern long-span buildings and structures. Problems of long-span buildings. "Long-span buildings" in books

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, for arranging the floors of large spans, they began to use wooden structures. 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, there appeared laminated wood. 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 the modern construction reduction in the mass of structures and structures has been promoted.

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 measures safety at each stage - architectural design, construction, operation.

An important point is the choice of building material - wood, reinforced concrete 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.

Planar structures

A

LECTURE 7. STRUCTURAL SYSTEMS AND STRUCTURAL ELEMENTS OF INDUSTRIAL BUILDINGS

Frames industrial buildings

Steel frame of one-story buildings

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

Rice. Steel frame building

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

Rice. 73. Steel columns.

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

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

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

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

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

Rice. 74. Steel trusses:

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

d – polygonal truss design.

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

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

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

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

Expansion joints

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

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

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

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

Walls of industrial buildings

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

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

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

Walls made of large panels

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

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

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

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

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

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

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

Windows, doors, gates, lanterns

Lanterns

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

Lanterns come in light, aeration and mixed types:

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

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

Aeration without glazing, used only for aeration purposes.

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

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

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

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

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

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

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

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

Aeration is called natural, controlled and regulated air exchange.

The action of aeration is based on:

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

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

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

Rice. 84. Building aeration schemes:

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

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

Doors and gates

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

Gates are intended for entry into the building Vehicle and the passage of large masses of people.

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

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

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

Rice. 81. Swing gates:

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

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

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

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

Coatings

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

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

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

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

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

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

Floorings

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

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

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

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

Roll roofs are made of roofing material. The top layer of roll roofing is installed protective layer gravel embedded in bitumen mastic.

Flooring made from leafy materials.

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

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

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

Drainage from coatings

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

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

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

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

Rice. 82. Internal drainage:

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

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

Internal drainage is arranged:

In multi-span buildings with multi-pitched roofs;

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

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

Floors

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

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

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

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

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

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

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

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

Rice. 85. Stone floors:

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

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

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

Rice. 86. Concrete and cement floors:

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

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

Rice. 87. Asphalt and asphalt concrete floors:

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

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

Rice. 88. Ceramic tile floors:

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

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

Rice. 89. Metal floors:

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

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

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

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

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

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

Stairs

Staircases of industrial buildings are divided into the following types:

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

- official, leading to work sites and mezzanines;

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

Rice. 90. Fire escape

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

Rice. 91. Emergency ladder

Fire barriers

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

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

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

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

Rice. 92. Firewalls:

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

Control questions

1. Name the design diagrams of industrial buildings.

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

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

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

Greenhouses and greenhouses

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

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

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

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

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

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

7 – glazed wooden frame.

LIST OF REFERENCES USED

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

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

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

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

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

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

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

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

Planar structures

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

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

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

Rice. 48. Long-span structures:

A- monolithic reinforced concrete frame, double-hinged.

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

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

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

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) buildings special purpose(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 structures coverings 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 types of supporting structures - brick or concrete walls, columns (metal or reinforced concrete);

When under support 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.

Truss calculations are performed using methods structural mechanics(similar to calculation roof 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 roof structures for long-span buildings turn out to be more cost-effective 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. Attached to spatial design the load 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:

High spatial rigidity: can be overlapped large spans with different support contours or column grids; get 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 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 dome designs four types(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.

At 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 connected 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 cables are laid during installation. reinforced concrete slabs. 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 coverings of a round (oval) plan, the thrust is transmitted to the outer compressed ring lying on the columns and the inner (stretched) 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 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 those consisting mainly of metal sheets and intended for storage and transportation of 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 stressed state, and in places where they are coupled with the bottom and stiffening ribs, in places where shells of different curvatures are coupled (i.e. at the boundary of a change in the radius of curvature), local high stresses arise, which quickly decay with distance from these areas - this is so called the 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 buildings include theaters, concert and sports halls, exhibition pavilions, garages, hangars, aircraft and shipyards and other buildings with spans of main load-bearing structures of 50 m or more. As a rule, such buildings are designed as single-span. They are covered with beam systems (mainly trusses), frames, arches, cable-stayed (hanging), combined and other structures.

Significant forces arise in the truss rods of large spans; therefore, instead of the traditional sections of two angles, double-walled composite sections are used. The height of the trusses is assigned within the l/s-Vis span, and it turns out to be more than 3.8 m. Transport trusses of this height by railway You can’t, they are assembled at the construction site.-

The frames are used in building coverings with spans of 60-120 m. Due to the rigid connection of the crossbar with the racks, the bending moments in the span will be less than in a beam structure: This allows not only to reduce the cross-sectional area of ​​the chords, but also the height of the crossbar, and therefore the height of the building . Both hingeless and double-hinged frames are used. Hinged ones are lighter than double-hinged ones, but they require larger foundations and are more sensitive to temperature changes and support settlements. It is not recommended to use them in subsidence soils. Double-wall sections of truss chords

Arches are used in coverings of long-span buildings with spans up to: 200 m. They are more profitable than beam and frame systems. Arches are: solid and through; non-hinged, double-hinged and three-hinged. Hinged arches with the same load are lighter than double-hinged ones, but for them, like for hingeless frames, massive foundations are required and they are so. they are more sensitive to changes in temperature and settlement of supports.

Most often, through double-hinged arches with a lifting boom equal to Vs-Ve are used. span. As the lifting boom increases, the longitudinal force in the arch decreases and the bending moment increases;

The cross-sections of the arch rods can be single-walled or double-walled

The stability of the main load-bearing structures (trusses, frames, arches) is ensured by horizontal and vertical connections. First of all, connections must be installed that secure the compressed belts of through structures

Frames and arches are statically indeterminate systems. Hinged frames and arches are three times statically indeterminate, double-hinged frames are once statically indeterminate. Usually, a thrust is taken as an extra unknown - a force, the approximate value of which for through frames and arches can be found using the formulas given in the designer's handbook.

Knowing the thrust, they determine the bending moments M, longitudinal N and transverse forces Q in the frame or arch as in a statically determinate structure, and from them the forces in the rods.

The forces in the rods of through frames and arches can also be determined by constructing force diagrams. Based on the forces obtained, the sections of the rods are selected, the nodes and connections are calculated in the same way as is done for trusses.

The dead weight of the load-bearing structures and the weight of the roof in< большепролетных сооружениях является основной нагрузкой, существенно влияющей на расход металла на покрытие, поэтому при выборе их конструктивной фор-» мы следует отдавать предпочтение более легким конструкциям. Особенно следует стремиться к снижению соб-» ственного веса кровли, применяя алюминиевые и другие панели покрытий с легким эффективным утеплителем.

Hanging and cable-stayed coatings are those in which flexible threads, mainly cables, are used as a supporting structure.

The main supporting structures of the hanging system - the cables - work only in tension, so they fully utilize the load-bearing capacity of the material

and it becomes possible to use steel of the highest strength.

Their transportation and installation are significantly simplified, which reduces the cost of construction. The above is a very important advantage of hanging systems compared to trusses, frames and arches. However, hanging structures also have serious disadvantages: they have increased deformability and require special supports to absorb thrust.

To reduce the deformability of cable stays, various methods of stabilizing them are used. For example, in double-belt cable-stayed systems, the rigidity of the cables is increased due to the construction of so-called stabilizing cables, connected to the load-bearing cables with hangers and spacers or a lattice of flexible prestressed elements.

The thrust depends on the ratio ///. At ///>Y, the increase in thread sag with increasing load is insignificant and can be neglected. In this case, the thrust can be determined by the formula. The cross-section of the cable is selected based on the force T.

For cable stays, steel ropes, bundles and strands of high-strength wire, round hot-rolled steel are used increased strength And thin sheets.

In combined systems, concentrated forces are transferred to a flexible thread through a rigid element, which makes it possible to significantly reduce their deformability.

For long-span buildings, in particular for hangars, a cantilever combined system is used, consisting of a rigid element and suspensions. The truss serves as a rigid element, which redistributes the concentrated forces between the suspensions. The latter serve as intermediate supports for the truss, and it operates as a continuous beam on elastically subsiding supports. .

The advantage of the cantilever combined system is that the rigid element (truss) does not require a rigid support at the second end. Thanks to this, large-sized gate structures can be easily created for hangars.

Long-span buildings can also be covered with spatial systems in the form of vaults, folds and domes.

General provisions

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

Such buildings include:

− workshops of heavy engineering factories;

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

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

1. Features of long-span buildings:

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

b) special methods for installing coating elements;

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

2. Methods for constructing long-span buildings

The following methods are used:

a) open;

b) closed;

c) combined.

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

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

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

− foundations for equipment;

− sometimes cumbersome technological equipment.

Then the covering is arranged.

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

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

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

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

Rice. 19. Fragment of the construction plan:

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

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

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

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

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

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

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

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

3.1.3.1. TVZ in the form of shells

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

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

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

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

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

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

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

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

Rice. 20. Geometric schemes of shells:

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

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

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

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

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

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

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

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

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

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

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

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

3.1.3.2. Technology for constructing buildings with domed roofs

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

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

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

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

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

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

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

Rice. 23. Construction of buildings with domed coverings:

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

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

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

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

3.1.3.3. Technology for constructing buildings with cable-stayed roofs

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

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

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

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

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

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

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

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

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

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

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

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

3.1.3.4. Technology of construction of buildings with membrane coatings

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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