Reinforced concrete columns. Types of steel columns for one-story industrial buildings Selection of columns for an industrial building

Monolithic columns are part of a building, vertical load-bearing elements. They lean on the columns balconies, terraces, ceilings. In addition to their main functions, columns are decorative element, decorate entrance group buildings and facade.

Columns receive and transmit the load from the elements above to the foundation of the building. Reinforced concrete pillars connect the structure and serve as support for the floors.

The architectural term "column" refers directly to the middle part, support pillar . The protrusions at the top of the post for supporting floors or crossbars are called capitals or consoles. Sometimes there is a column support, a glass for attaching to a columnar foundation.

Species and types

Concrete columns are divided by type of section, production method.

According to the type of section they are divided square, round or rectangular form.

Classified according to production method factory-ready elements, supplied to the site with ready-made structures or erected on construction site, monolithic columns.

Features of the construction of monolithic columns

Before carrying out work, prepare the site, necessary materials, tools, structures. The site is marked.

Then they move directly to construction:

• assemble formwork;
• install the reinforcement frame;
• pour the concrete mixture;
• carry out concrete maintenance procedures;
• allow time for the mixture to gain strength;
• demoulding structures.

Monolithic reinforced concrete columns calculated at the design stage. The cross-section and shape of the column, the diameter of the reinforcement, and the brand used will depend on the amount of the planned load, including the element’s own weight.

Important! Installation deficiencies and miscalculations lead to the destruction of the structure. If there is a lack of cross-section, deformation occurs longitudinal bending, the column bends under load.

Preparation of tools and materials

The need for materials and tools is clarified at the stage of preparation for work. Tools you will need:

• metal square, level for checking the verticality and horizontality of surfaces;
• steel rod, will help release air;
• screwdriver for fastening formwork;
• vibrator compacts the mixture;
• prefabricated formwork from shields, supports.

The concrete mixture is delivered to the construction site ready-made or mixed immediately before laying using a concrete mixer. To prepare, take one part of cement, add two parts of sand, mix with two parts of crushed stone and two parts of gravel. By mixing the dry mixture with water, plastic concrete of a uniform consistency is achieved.

In addition to the concrete mixture, the following materials are required:

• nails, self-tapping screws for fastening formwork;
• reinforcing bars of design cross-section and length;
• steel wire;

Installation of formwork

The formwork is installed in the design position. The shields are aligned vertically and strengthened with the help of struts, wooden struts. The struts are anchored using support blocks in two directions to prevent shifting.

When concreting a high column, the formwork installation process is somewhat different from the usual one. Three sides of the form are mounted, and the fourth side is closed as the formwork is filled with concrete.

Reinforcement

By tying the rods together, you get rigid volumetric frame to strengthen concrete. The number of longitudinal rods in the frame is 4-6 pcs. For a square section, four rods at the corners of the element are sufficient, for rectangular shape the long side is further reinforced. Cross-linking of reinforcement is used when constructing columns up to 2 meters long.

A frame exceeding a length of 2 m is tied with short rods across, in increments of 20-50 cm, taken in the calculation according to the planned load.

The capitals are reinforced with reinforcing mesh.

The thickness of the mesh rod is 15 mm, the cell size is 10 x 10 cm.

Reinforcement of the column is carried out by laying a mesh in each step; the dimensions and number of meshes are taken from the project.

Concreting

After installing the formwork and reinforcement cage, concreting begins, which produced in layers, in layers 0.3-0.5 m thick, preventing the previous layer from setting. Do not add 50-70 mm of mortar to the top of the formwork.

To shrink concrete in columns above 5 meters, arrange technological breaks from 40 minutes to 2 hours.

When feeding ready-mixed concrete by mechanization, the feed speed is reduced to avoid segregation. Air is released from the mixture with steel rods, concrete compacted with manual vibrators. In places inaccessible to the vibrator, concrete is compacted manually by careful bayoneting.

Upon completion of work, they produce seasonal care behind the concrete.

Dismantling of formwork

Time required for concrete to reach 100% working strength is 28 calendar days . The indicator may vary depending on environmental conditions - temperature, humidity, care package. Middle period standing time for monolithic columns before stripping is 7-10 days summer period. This period allows the corners and side edges to form.

note

Until the concrete reaches 100% strength of monolithic columns, work is suspended or related work is carried out. The load on the uncured mortar will lead to the destruction of structures.

Removal of the formwork begins with the struts, gradually removing the fastenings and side panels.

Monolithic columns as a frame element provide spatial rigidity and strength of the building.

Useful videos

Formwork for columns and their filling:

See how the reinforcement frames of the columns are knitted:

Rules for installing small-panel formwork for pouring monolithic formwork concrete column for a private home, look:

We look at the process of concreting a monolithic frame of house columns:

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In modern industrial construction, prefabricated reinforced concrete frames are mainly used, structural elements which are typed.

Foundations

Foundations are placed under individual supports (columns of frame buildings, pillars), as well as under the walls of light buildings without basements. This is the cheapest and least labor-intensive type of foundation - it is 1.5-4 times cheaper than strip foundations.

Under the columns of one-story industrial buildings They mainly use monolithic foundations, consisting of a popliteal joint and a one-, two- or three-stage slab part (Fig. 9.18).

The height of the foundations is assumed to be 1.5 m and within the range of 1.8-4.2 m with an interval of 0.6 m. The dimensions of the ledges in plan and height are 0.3 or 0.45 m. All dimensions in plan are unified and are multiples of the module 0.3 m. The dimensions of a specific foundation are selected depending on the load transmitted by the column (columns), soil characteristics and solutions for the part of the building below the zero level.

The foundation for paired columns in places of expansion joints and junctions of spans is arranged in common (Fig. 9.20), except in cases where a settlement joint is required.

The edge of the foundations is most often located under reinforced concrete columns at minus 0.150, and under steel columns - minus 0.300 and below.

To install reinforced concrete columns in the body of the foundation sub-column, a recess is provided - a glass. The gap between the edges of the column and the wall of the glass is assumed to be 75 mm at the top, and 50 mm at the bottom (Fig. 9.18 d). At steel columns ah, anchor bolts are placed in the column support to secure the columns to the foundation.

Rice. 9.18. Monolithic columnar foundations for prefabricated reinforced concrete columns of industrial buildings: a - single-stage; b - two-stage; c - three-stage; g - column support; d - top view

Prefabricated columnar foundations, depending on the size, can be solid from one block, from a block and slab, or from several different blocks and slabs (Fig. 9.26). Solid foundations are relatively small in size and weight. The use of ribbed and hollow elements makes it possible to reduce the material consumption of prefabricated columnar foundations.

Slabs (blocks) are laid on a preparation with a thickness of about 100 mm - crushed stone or sand for dry soils and concrete for wet soils. The elements are laid on top of each other using mortar and connected by welding embedded parts, outlets, anchors, etc.

Rice. 9.26. Prefabricated columnar foundations for columns: a-c - single-block pillars; g - column support on the slab; d - three-slab; e - column support on slabs in two rows; g - column support on perforated plates in two rows; h - column support on two ribbed slabs; and - ribbed column support on three slabs; k - high (hemp type) column support on a block and three slabs; l - pillar with recess into two slabs; m - ribbed; n - hollow column support on the slab; o - made of three hollow elements with a high column

To support external and internal self-supporting walls, foundation beams are used (Fig. 9.19), which transfer the load from the weight of the walls to the foundations. When supporting foundation beams on foundation ledges, it is recommended to install tides (concrete columns), the width of which is taken to be no less than the maximum width of the beam, and the top at minus 0.360 or 0.660 - respectively, for beam heights of 300 and 600 mm.

When heaving soils freeze, deformations may occur in foundation beams. To avoid this and to protect the floor from freezing, slag is poured along the walls from the sides and bottom of the beams (Fig. 9.20 c).

Rice. 9.20. Location of foundation beams:

a - side view; b - plan; c - section; 1 - foundation beam; 2 - tide or concrete column; 3 - row column; 4 - column at the expansion joint; 5 - column of the adjacent span; 6 - wall; 7 - filling with slag; 8 - blind area

Rice. 9.19. Foundation beams: a - sections of beams for buildings with a column spacing of 6 m; b - the same, 12 m; c - supporting beams on the foundation

Frame columns. The design of prefabricated reinforced concrete columns depends on the space-planning solution of the industrial building and the presence in it of one or another type of lifting and transport equipment with a certain load-carrying capacity. In this regard, precast reinforced concrete columns are divided into two groups. Columns belonging to the first group are intended for buildings without overhead cranes, in craneless workshops and in workshops equipped with overhead lifting and transport equipment. Columns belonging to the second group are used in workshops equipped with overhead cranes.

According to the design solution, the columns are divided into single-branch and double-branch, according to location in the building - at the extreme, middle and located at the end walls.

Typical columns are designed for loads: from the coating and overhead lifting and transport equipment in the form of monorails or overhead cranes with a lifting capacity of up to 5 tons, and from the coating and overhead cranes with a lifting capacity of up to 50 tons. Solutions for prefabricated reinforced concrete two-leg columns for cranes with a lifting capacity of 75/20, 100/ have been developed. 20 and 125/20 t for spans of 24, 30 and 36 m with column spacing of 6 and 12 m. The height gradation of columns is set to a multiple of 600 mm module.

For buildings without overhead cranes, having a height from floor to bottom load-bearing structures coverings up to 9.6 m, use columns with a cross section of 400x400, 500x500 and 600x500 mm (Fig. 24.1, a). The middle columns with a cross-section of 400x400 mm in the place of support of the load-bearing structures have coverings on two side faces of the console. The choice of column section depends on the size of the span and their number, the pitch of the columns, the presence of rafter structures, suspended transport and the design of the coating.

Rice. 24.1. Prefabricated reinforced concrete columns: a – single-branch for craneless buildings; b – single-branch for crane buildings; c – two-branch for crane buildings; d – location of embedded steel parts in the column: 1 – steel sheet with anchors for fastening prefabricated reinforced concrete beams or farms; 2 – the same, for fastening crane beams; 3 – steel sheet for fastening crane beams to the columns on top, 4 – embedded parts for fastening vertical connections; 5 – embedded part for fastening wall panels. 6 – hole for slinging; 7 – support table

In cases where a craneless building must be greater than 9.6 m in height, columns for overhead crane buildings can be used. This solution allows you to expand the scope of application of standard columns without increasing the number of their standard sizes. For buildings equipped with overhead cranes with a lifting capacity of up to 20 tons, single-branch columns are used rectangular section(Fig. 24.1, b).

A column for a building equipped with overhead cranes consists of an over-crane and under-crane part. The over-crane part serves to support the supporting structure of the covering and is called the over-column. The crane part receives loads from the above-column, as well as from the crane beams, which are supported on the consoles of the columns, and transfers them to the foundation. The outer columns have a one-sided console, the middle ones have double-sided consoles.

The sections of the outer and middle columns at a step of 6 m are 400x600 and 400x800 mm, and at a step of 12 m – 500x800 mm. For cranes with a lifting capacity of up to 30 tons and a building height of more than 10.8 m, two-branch columns are used, which are more economical in material consumption than single-branch columns. They are stepped And stepped-cantilever(Fig. 24.1, c): the first ones are intended for the outer rows, the second ones for the middle ones.

The height of typical two-branch columns is 10.8-18 m. Columns with a height of 16.2 and 18 m are used in cases where it is appropriate for operational conditions and justified by economic considerations. The gaps between the branches are used to pass sanitary and technological communications. In some cases, reinforced concrete columns can be used for cranes with a lifting capacity of over 50 tons. In such two-branch columns, passages are arranged for workers, which are located at the level of the crane runways.

The depth of the columns below the zero level depends on the type and height of the columns, the lifting capacity of the crane equipment and the presence of rooms or pits located below the floor level. The depth of columns in buildings with and without overhead transport is 0.9 m; rectangular columns used in buildings with overhead cranes - 1 m; two-branch columns with a height of 10.8 m - 1.05 m and the same columns with a height of 12.6-18 m - 1.35 m; two-branch columns for cranes with a lifting capacity of more than 50 tons - 1.6 m, and in the presence of technical undergrounds, channels or basements - 3.6-5.6 m. These dimensions are due to the unification of the dimensions of prefabricated reinforced concrete structures. The columns are connected to the frame elements with bolts and welding of welded embedded parts (Fig. 24.1, d).

On the side surfaces of single-branch and double-branch columns in places where they are embedded in the foundation to absorb shear forces, dowels are provided in the form of triangular grooves 25 mm deep with a pitch of 200 mm.

Brands of columns for a certain type of building are selected from a catalog of prefabricated reinforced concrete products, depending on the lifting capacity of cranes, their operating mode, column spacing, span and height of the building, load from the coating and wind pressure.

Modern progressive structural solutions for columns include cylindrical columns made of centrifuged reinforced concrete, which are currently used on an experimental basis both for buildings without support cranes and with support cranes with a lifting capacity of up to 30 tons and in industrial buildings for various purposes. This solution makes it possible to reduce the consumption of concrete by 30-50% and steel by 20-30% (Fig. 24.2).

Rice. 24.2. Types of Cylindrical Columns

Foundations for columns. The volume of concrete going into the foundations for columns in an industrial building is 20-35% of the total volume of concrete consumed, and the cost of their construction is 5-20% of the total cost of the building. This suggests that right choice foundation design is essential and significantly affects the cost of the entire building.

The foundations are made monolithic and prefabricated. Precast concrete foundations can be made of a single block, a block and slab, or multiple blocks and slabs. Blocks and slabs are laid on a preparation 100 mm thick - crushed stone for dry soils and concrete (grade 50) for wet soils.

For one foundation block You can support from one to four columns (in places where expansion joints are installed). The area of ​​the base and other dimensions of the foundation are determined by calculation depending on the load transferred to it and the bearing capacity of the foundation.

Foundations in the form of individual blocks (Fig. 24.3) have a square or rectangular outline in plan. They are used for prefabricated reinforced concrete columns with a section of 400x400 and 500x500 mm. Single-block foundations weighing up to 12 tons are manufactured at factories of prefabricated reinforced concrete structures, and those weighing up to 22 tons are manufactured at landfills or they are made monolithic directly at the construction site. Single-block foundations - shoes are arranged in steps with the dimensions of the cups corresponding to the dimensions of the cross sections of the columns.

Rice. 24.3. Prefabricated foundations for columns: a – from one block; b – from block and slab: 1 – foundation slab; 2 – glass, 3 – lifting loops; 4 – risks; 5 – welds; 6 – leveling layer of solution; 7 – embedded parts and anchors; 8 – gas tubes

When large loads are transferred to the foundations, which causes their significant dimensions, and the mass of the block exceeds the lifting capacity of the cranes, and the use of a monolithic structure is not economically feasible, the need arises to use prefabricated foundations. Prefabricated foundations can be made of two elements - a block and a slab (Fig. 24.3, b) or several blocks and slabs (Fig. 24.4, a). The latter are used if the mass of blocks in a two-block foundation turns out to be greater than the carrying capacity of available transport and installation equipment. Prefabricated foundation elements are laid on mortar and fastened together by welding embedded parts steel parts.

Rice. 24.4. Prefabricated reinforced concrete foundations and supporting frame columns on them: a – from several blocks and slabs; b – the same, from blocks with voids; c – rigid embedding of the column into the glass: 1 – column; 2– shoe with glass (column support); 3 – intermediate block; 4 – slabs; 5 – base panel; 6 – column; 7 – foundation beam; 8 – assembly concrete: 9 – cement mortar; 10 – connection of embedded steel parts by welding

Precast foundations use large amounts of concrete and steel. To eliminate this drawback, the elements of a multi-block foundation can be made with vertical voids, resulting in a foundation in the form of a beam cage (Fig. 24.4 b). The blocks and slabs that form the foundation are packages of reinforced concrete elements connected by structural diaphragms.

The number, size and location of voids in the plan are chosen so that when foundation elements are laid on top of each other, wells are formed that pass through the entire foundation. Vertical voids can be of various shapes: round, square, rectangular, oval. If an eccentric load is transferred to the foundation, part of the vertical wells within the contour of the column can be reinforced and cemented.

The mark of the top edge of the foundation, regardless of ground conditions, should be 150 mm below the mark of the finished floor (Fig. 24.4, a). This solution makes it possible to install structures on the ground part of the building after the pits have been backfilled, preparation has been made for the floors and all communications have been laid, which is especially important in conditions of subsiding macroporous soils, when the ingress of water into the pits must be completely excluded.

To lay foundations to the depth required by geological conditions, one of the following methods is used, depending on economic feasibility: an additional cushion is arranged under the base of the foundation, the upper stage of the foundation is increased, the columns are installed at the same height (at the lowest foundation elevation), and in places where foundation elevations change foundations, inserts are used - column supports.

The connection of frame columns with foundations is usually carried out in the form of a rigid connection. With this connection, the columns are installed in glasses specially arranged in the foundations (Fig. 24.4, c). In this case, the gaps in the glasses between the columns and shoes are filled with concrete.

Foundation beams. The external and internal self-supporting walls of the building are installed on foundation beams, through which the load is transferred to the foundations of the frame columns. Foundation beams are laid on specially prepared concrete columns, installed on the edges of the foundations (Fig. 24.5, a).

Rice. 24.5. Supporting the foundation beams on the foundations: a – under the longitudinal wall; b – under end wall: 1 – foundation beam; 2 – concrete column; 3 – column; 4 – self-supporting longitudinal wall; 5 – end wall; 6 – half-timbered column; 7 – foundation for the main column; 8 – foundation for a half-timbered column; 9 – slag filling; 10 – fatty clay; 11 – sand bedding; 12 – blind area; 13 – waterproofing

The main foundation beams are made with a height of 450 mm (for a column spacing of 6 m) and 600 mm (for a column spacing of 12 m) and a width of 260, 300, 400 and 520 mm. These dimensions correspond to the most common thickness of external walls in industrial buildings. In Fig. 24.5, b shows the location of the foundation beams for the end wall. The cross-section of foundation beams can be T-shaped, trapezoidal and rectangular. T-section beams are most widely used as they are more economical in terms of consumption of steel and concrete.

When freezing under the influence of heaving soils increasing in volume, deformations may occur in the foundation beams. To avoid this and to protect the floor from freezing along the walls, the beam is covered with slag from the sides and bottom. The upper edge of the foundation beam is placed 30-50 mm below the floor level of the room, which in turn is placed approximately 150 mm above the level of the ground surface planned around the building.

Waterproofing made of cement-sand mortar or two layers of rolled material on mastic is laid on top of the foundation beams. A blind area or sidewalk is installed on the surface of the ground along the foundation beams. Once the precast foundation beams are in place, the gaps between them and the columns are filled with concrete.

Strapping beams serve to support external walls in places where the heights of buildings differ, and when these beams are located above window openings, they act as lintels. The strapping beams are made as split beams. Their sizes and shape cross section taken depending on the thickness of the walls installed on them and the magnitude of the transmitted load.

Strapping beams are used when the walls of a building are made of brick or small blocks. The dimensions of the strapping beams are unified; for brick walls the width is 250 and 380 mm with a “spout”; for walls made of small blocks 190 mm thick, the strapping beams are 200 mm wide. The strapping beams are made 600 mm high and 6 m long (Fig. 24.6) and attached to the frame columns using mounting parts welded to the embedded parts in the beams and columns. In typical reinforced concrete columns, for these purposes, embedded parts are used, provided for fastening wall panels.

Rice. 24.6. Fastening the strapping beams to the reinforced concrete column: 1 – steel support console; 2 – embedded parts in the column; 3 – embedded part in the strapping beam; 4 – concrete on fine gravel

Reinforced concrete crane beams serve as supports for the rails on which overhead cranes move. In addition, they provide longitudinal spatial rigidity of the building frame.

Reinforced concrete crane beams have limited use and can be split or continuous. The former are more widespread than the latter, as they are easier to install. When constructing continuous beams, the consumption of reinforcement is lower, but the labor intensity of their manufacture is higher.

Depending on the position of the beams along the crane runway, middle and outer beams are distinguished, located at the transverse expansion joints and at the ends of the buildings. The latter have the same dimensions as the middle ones, however, the embedded parts in them, intended for fastening to columns, are located at a distance of 500 mm from the end of the beams.

Reinforced concrete crane beams can be of T-trapezoidal or I-section (Fig. 24.7), they are used for light and medium-duty cranes with column spacing of 6 and 12 m and a lifting capacity of overhead cranes up to 30 tons.

Rice. 24.7. Reinforced concrete crane beams: a – T-beams for cranes with a lifting capacity of 10–30 tons with a column spacing of 6 m; b – I-beam pop cranes with a lifting capacity of 10–30 tons with a column spacing of 12 m; 1 – holes for fastening trolley wires, 2 – holes for fastening crane tracks

After installation and alignment of the crane beams, they are fastened (Fig. 24.8) to the columns: at the bottom - with bolts and welding, at the top - by welding a vertically placed sheet to the embedded parts in the column and beam. When manufacturing reinforced concrete crane beams, gas tubes are placed in their body, which are necessary for passing the bolts for fastening the crane track and hangers for trolley wires.

Rice. 24.8. Fastening crane beams to frame columns: 1 – column; 2 – crane beam; 3 – embedded steel part of the column; 4 – supporting steel sheet of the column console; 5 – steel gasket with holes for bolts; 6 – lower embedded steel part of the crane beam; 7 – anchor bolts; 8 – upper embedded steel part of the crane beam; 9 – fastening vertically placed steel sheet; 10 – welding

The crane runway is installed in a certain sequence. A thin elastic lining made of rubberized fabric 8–10 mm thick with a double-sided rubber lining is placed on the top of the crane beam. Before laying it, the surfaces of the crane beam, rail and elastic lining are thoroughly cleaned of dirt and grease. The crane rail is installed and straightened on the elastic lining and then secured with clamping feet.

For cranes with a lifting capacity of 10-30 tons, special profile rails R-43, KR-70 and KR-89 are used. For cranes with a lifting capacity of 5-10 tons, wide gauge railway rails R-38 are also used. Within the temperature block, the rails are welded into one strand.

In highland buildings, stops for overhead cranes are installed on crane beams.

Load-bearing structures of coatings industrial buildings are divided into rafters, sub-rafters and load-bearing elements of the enclosing part of the covering.

In industrial buildings, the following types of truss load-bearing structures are usually used: flat - beams, trusses, arches and frames; spatial – shells, folds, domes, vaults and hanging systems.

Rafter structures are made in the form beams And farms, and the supporting structures of the enclosing part of the coating are in the form large slabs. According to the unified dimensions of the space-planning elements of industrial buildings, the size of the transverse spans and longitudinal pitch of load-bearing structures is assigned as a multiple of the enlarged module of 6 m; in some cases, the use of a module of 3 m is allowed.

Reinforced concrete beams used for the installation of coverings in industrial buildings with spans of 6, 9, 12 and 18 m. The need for beam coverings with spans of 6, 9 and 12 m (spans of this size can also be covered with slabs) arises in the case of suspension of monorails or cranes to load-bearing structures.

Reinforced concrete beams can be single-pitched, double-pitched and with parallel chords (Fig. 24.9). Single-pitch beams are used in buildings with a column spacing of 6 m and external water drainage. Gable beams are installed both in buildings with external and internal water drainage. Beams with spans of 6, 9 and 12 m are installed only in increments of 6 m, and beams with a span of 18 m are installed in increments of 6 and 12 m. If there is overhead transport, regardless of the span, beams are installed in increments of 6 m.

Rice. 24.9. Reinforced concrete beams: a – single-pitched; b – gable; c – with parallel belts

In order to reduce the mass of beams and to allow communications through, holes of various shapes can be installed in their walls. Single-pitch beams are supported by standard reinforced concrete columns of different heights, which are a multiple of a module of 600 mm. In this regard, the slope of single-pitch beams with a span of 6 m will be 1:10, with a span of 9 m – 1:15, and with a span of 12 m – 1:20. The slope of the upper chord of the gable beams is 1:12.

The covering beams are connected to the columns with anchor bolts released from the columns and passing through the support sheet welded to the beam (Fig. 24.10, a, b). In longitudinal expansion joints, one of the beams is installed on a roller support; the beam located nearby is installed on a steel table located above the column (Fig. 24. 10, c).

Rice. 24.10. Installation of reinforced concrete beams: a – on the outer columns; b – on the middle columns, c – c expansion joint for one column: 1 – anchor bolt; 2 – supporting steel sheet of the beam; 3 – supporting steel sheet of the column; 4 – column; 5 – reinforced concrete beam; 6 – semi-thin; 7 – skating rink; 8 – temperature seam

Reinforced concrete trusses They are usually used to cover spans of 18, 24 and 30 m; they are installed in increments of 6 or 12 m. Trusses with a span of 18 m are lighter than reinforced concrete beams of the same span, but are more labor-intensive to manufacture.

The use of 18-meter trusses is advisable in the case when it is necessary to place communication pipelines and ventilation ducts within the coverage or use the inter-truss space for the device technical floors. For spans of 24 and 30 m, the use of trusses is more advantageous compared to beam structures, since the mass (weight) of long-span trusses is 30-40% less than the mass (weight) of beams.

In modern industrial construction practice, trusses with a segmental outline and with parallel chords are most widespread (Fig. 24.11), both of which are included in the range of standard prefabricated reinforced concrete structures of factory production. Reinforced concrete trusses can be solid or composite; the latter are assembled from two half-trusses (shipping grades), or from blocks, or from casting elements.

Rice. 24.11. Unified prefabricated reinforced concrete trusses: a – segmental; b – with parallel chords (truss elements shown in dotted lines are installed if there is a suspended ceiling)

Segmental trusses with spans of 18, 24, 30 m included in the range of prefabricated reinforced concrete structures are assembled from prefabricated linear elements of the upper and lower chords and lattice. Linear elements have a length equal to the truss panel, and for the lower chord they sometimes take a length equal to the span of the truss.

The connection of linear elements to each other is carried out by welding the ends of the reinforcement with the installation of grease linings and subsequent concreting with quick-hardening concrete. The reinforcement in the lower chord is subjected to pre-tensioning, after which the channels in the nodes are filled with cement mortar, and the trays of the lower chord are filled with concrete. Reinforced concrete trusses make it possible to equip building spans with suspended transport with a load capacity of up to 5 tons (with a truss pitch of 6 m). It is possible to install light and aeration lantern structures along the upper chord of segmental trusses.

For buildings where it is necessary to use the inter-truss space for auxiliary rooms or communications, non-braced trusses with racks every 3 m are used (Fig. 24.12). With a flat covering, the truss posts are passed beyond the upper chord; they serve as supports for the covering slabs (Fig. 24. 12, b). Separate racks are installed on the truss supports, which are secured by welding steel plates to the embedded parts located in the trusses and racks.

Rice. 24.12. Prefabricated reinforced concrete trusses: a – non-braced for buildings with a pitched roof; b – unbraced for buildings with flat covering; V - general form coverings with rafter structures; d – arched of two half-trusses: 1 – additional rack; 2 – covering slab; 3 – roof truss; 4 – rafter truss

Non-braced trusses make it possible to reduce the number of types of trusses; in addition, they are less labor-intensive to manufacture compared to trusses with a braced lattice.

In Fig. 24.12, c shows an example of a coating solution using 24-meter segmental unbraced trusses resting on 18-meter reinforced concrete segmental unbraced trusses rafter trusses. In some cases, composite trusses are used to span large spans. In Fig. 24.12, d shows a reinforced concrete truss with a span of 45 m, designed for constructing a covering over the main building of the state district power station. The truss is designed as a composite of two half-trusses, three tie-down elements, a lower chord and two hangers.

The trusses are attached to the frame columns with anchor bolts released from the column, and to increase the rigidity of the connections, the truss support sheets are welded to the embedded parts of the columns.

Reinforced concrete arches It is advisable to use for large spans (40 m or more). Arches are divided into three-hinged with hinges on supports and in the middle of the span, double-hinged with hinges on supports and hingeless. The outline of the centering axis of the arches should coincide as much as possible with the pressure line, so that the arches mainly work for compression. The supports of the arches can be building columns or special foundations. For large spans, arches, as a rule, rest directly on the foundations.

In three-hinged arches, the middle key hinge complicates the design of the arch itself and the design of the enclosing structures of the roof covering. For these reasons, reinforced concrete three-hinged arches practical application currently do not have.

The most common are double-hinged arches, which are the easiest to manufacture and install. When exposed to temperature, they have the ability to bend, turning freely in hinges without a significant increase in stress in the arch sections. In double-hinged arches, the thrust is absorbed by the tension and transferred to the supports.

Hinged arches have the lightest structural solution, but to support them they require the construction of powerful foundations, and they are also sensitive to uneven settlements of the foundation soil. Hinged arches, when supported directly on foundations, are usually performed without tightening.

In construction practice, arches made of prefabricated elements are mainly used. Monolithic arches have not become widespread due to the high labor intensity of their construction. Prefabricated elements, in turn, are assembled from blocks. The cross-section of the arch can be rectangular, T-shaped, box-shaped and other shapes.

An example of a double-hinged arch resting on pile foundations is shown in Fig. 24.13, a. An example of a hingeless arch with a span of about 60 m, a height (in the middle part) of 40 m, resting directly on the foundations, is shown in Fig. 24.13 b. In this example, the arch is designed open, with a lightweight spatial type covering suspended from it using steel rods.

Rice. 24.13. Reinforced concrete arches: a – double-hinged; b – hingeless, supported on foundations; c – hingeless, supported on columns: 1 – arch link; 2 – supporting side beam; 3 – suspension; 4 – tightening; 5 – covering slab; 6 – frame colony, 7 – suspended covering of spatial type

A reinforced concrete arch made of prestressed elements with a span of 96 m, supported by columns with a pitch of 12 m, is shown in Fig. 24.13, at. The length of individual prefabricated links with an I-beam cross section does not exceed 17 m with a mass of up to 25 tons. The links are connected to each other by welding embedded steel parts. The hangers supporting the reinforced concrete tie of the tray section are made of metal corners. The arch takes the load from suspended transport - four suspended cranes with a lifting capacity of 5 tons.

Reinforced concrete frames they are arranged as single-span and multi-span, monolithic and prefabricated (Fig. 24.14). Frames are a rod structure, the geometric immutability of which is ensured by rigid connections of frame elements at nodes. The outline of the crossbars in the frame can be straight, broken or curved. Rigid connection of frame elements at nodes makes it possible to increase the size of the overlapped span.

Rice. 24.14. Reinforced concrete frames: a, c – single-span monolithic; b – multi-span team

The design solution of a single-span, double-hinged frame made of prestressed reinforced concrete with racks of variable cross-section and a box-section crossbar is shown in Fig. 24.14, a, a single-span reinforced concrete frame with racks rigidly embedded in the foundations, and with consoles for supporting crane beams under an overhead crane - in Fig. 24.14, at. In these examples, the frame posts protrude from the plane of the walls to the outside, which gives the buildings a unique architectural design.

Prefabricated multi-span frame mounted from the outer L-shaped racks, medium T-shaped racks and pitched liners - crossbars, is shown in Fig. 24.14, b. The joints in the frame are located in places where they bend. moments occur only with wind and asymmetrical loads from snow.

Types of columns of one-story industrial buildings. Purpose of embedded parts.

Reinforced concrete and steel columns are used to construct the frames of one-story industrial buildings.

Reinforced concrete columns of one-story industrial buildings (Fig. 26) are available with or without consoles (if there are no overhead cranes). Based on their location in plan, they are divided into columns of middle and outer rows.

Taking into account the dependence on the cross section of the column, there are rectangular, T-profile and two-branch columns. Cross-sectional dimensions depend on effective loads. The following standardized dimensions of column sections are used: 400x400,

Rice. 25. Foundations of one-story industrial buildings a) types of foundation beams; b), c) details of the foundations of the outermost row of columns; 1-sand; 2 - crushed stone preparation; 3 - Asphalt or concrete covering(blind area); 4-waterproofing; 5-column; 6-slag or coarse sand; 7-reinforced concrete columns; 8-Foundation Beam.

Rice. 26. Main types of reinforced concrete columns of one-story industrial buildings. a) rectangular section for a building without overhead cranes at a pitch of 6 m; b) the same, with a step of 12 m; c) two-leg for buildings without overhead cranes; d) rectangular cross-section for cranes with overhead cranes; e) the same, I-section; f) two-leg for buildings with overhead cranes; g) general view of the column; 1 - embedded part for fastening the supporting structure of the coating; 2,3 - the same, crane beam; 4 - the same, wall panels.

Rice. 27. Main types of steel columns

a) constant cross-section, b), d) variable cross-section, e) separate

600x600, 400x800, 500x500, 500x600, 500x800 mm - for rectangular; 400x600 and 800x800 mm - for T-bars and 400x1000, 500x1000, 500x1300, 500x1400, 500x500, 600x1400, 600x1900 and 600x2400 mm - for two-branch ones. Columns come in several parts that are assembled at the construction site.

Columns with consoles consist of over-crane and sub-crane branches. The cross-section of crane branches is most often square or rectangular: 400x400 or 500x500mm. For the manufacture of columns, concrete of classes B15, B40 and reinforcement of various classes are used.

The length of the columns is taken taking into account the height of the workshop and the depth of their embedding in the foundation, which should be: for rectangular columns without overhead cranes - 750 mm , for rectangular and I-section columns with overhead cranes - 850mm; for two-branch columns - 900-1200 mm.

The columns are provided with embedded parts (Fig. 2b,g):

1 - for fastening load-bearing structures of the coating (steel sheet welded to special reinforcement); 2 - for securing crane beams from tipping over under the influence of braking forces; 3 - for fastening crane beams against displacement (steel sheet with four M16 bolts); 4 - for fastening wall panels (63x5, welded to the frame reinforcement before concreting the columns).

In addition to the base columns, half-timbered columns are used to install half-timbered structures. They are installed along the building with a pitch of outer columns of 12 m and a wall panel size of 6 m, as well as at the ends of buildings.

Steel columns one-story buildings can have a cross-section that is constant in height or variable. In turn, columns with variable cross-sections come with a crane part of a solid and through section (Fig. 27). Through columns are divided into columns with branches connected by ties, and separate columns, which consist of independently operating tent and crane branches. Columns of constant cross-section are used when using cranes with a lifting capacity of up to 20 tons and a building height of up to 9.6 m.

In cases where the columns mainly work on central compression, columns of solid section are used. For the manufacture of solid columns, wide-flange rolled or welded I-beams are used, and for through columns, I-beams, channels and bushings are also used.

Separate columns are installed in buildings with heavy overhead cranes (125 tons or more). At the bottom of the columns, steel bases (shoes) are provided for connection with the foundations. The bases are secured to the foundations with anchor bolts, which are placed into the foundation during their manufacture. The lower supporting part of the column together with the base is covered with a layer of concrete

Types of columns of one-story industrial buildings. Purpose of embedded parts. - concept and types. Classification and features of the category "Types of columns of one-story industrial buildings. Purpose of embedded parts." 2017, 2018.

To spend construction process private or multi-storey building, one cannot do without the use of reinforced concrete. What is reinforced concrete? Concrete is construction material, which has a low strength index. This indicator may vary depending on the method of concrete production, as well as the brand that was used for production. But, one way or another, it is still unsafe to use concrete due to its high level of fragility. That is why it is additionally reinforced. Steel or another type of metal is most often used for this purpose. It is desirable that it does not succumb to the formation of corrosion on the surface. Reinforced concrete can be used to produce floor slabs, as well as reinforced concrete columns, which are indispensable in private or multi-storey housing construction. Please note that you only need to contact professional companies on production. Only in this case will construction be safe. Let's consider the main features and advantages of using reinforced concrete columns and what technical characteristics they have.

Main advantages of application

The use of reinforced concrete is extensive due to the large number positive aspects operation. The main advantage is high level rigidity and resistance to various loads. Modern reinforced concrete columns can withstand heavy weight floor slabs. The advantages of such columns also include the following factors:

• High level of rigidity and durability of use. Please note that such reinforced concrete columns can be used for more than 100 years. It is worth noting that the level of strength does not decrease with service life. This is why the building can be operated safely for a long time;
• Fire resistance. The two main materials used are concrete and steel. These materials are not subject to combustion, which also has a positive effect on the operation of the house and the safety of living in it;
• Static and dynamic loads do not in any way affect the use of reinforced concrete columns. Even strong vibration of the earth will not contribute to the destruction or deformation of modern columns of this type.

But it is also worth noting some negative sides Applications: large weight of columns (it is very difficult to transport them, and also to install columns), thermal conductivity is quite high. But, as a rule, a high number of columns does not greatly affect living in the house.

A large number of ordinary consumers, hearing the definition of “column,” imagine antique and architectural compositions or houses with majestic large columns. However, in addition to such structures performing decorative solution, there are also columns made of reinforced concrete, created to strengthen the frame of the building.

Purpose

A reinforced concrete column is designed to perform supporting functions for various building structures. With its help, beams, crossbars, trays, arches, etc. are strengthened. Precast concrete columns are made from heavy concrete, grades 200 and 300. To create a reinforcement frame, special reinforcement is used.

Reinforced concrete columns are used to strengthen single-story, industrial, domestic, multi-storey buildings. A reinforced concrete column is used to distribute the load from floor structures and other building elements.

Design Features

Reinforced concrete two-leg columns are made from reinforced concrete mixture. What the data looks like standard designs as vertical elements characterized by a small cross-sectional index. These building compositions are mainly used to form a cohesive or frame frame.

Properties and characteristics

Reinforced concrete columns have a certain set of characteristics and properties:

• high level of resistance to external influence;
• guaranteed compliance with the promised load-bearing characteristics;
• stability with respect to seismic effects;
• water tightness;
• stability with respect to negative temperatures.

The selection guide for any product assumes compliance with these parameters:

• information obtained during genealogical analysis;
• weather conditions and climatological environment in which the column will be located;
• number of floors of the building being constructed;
• the purpose of the building in which the installation of columns is provided;

The property of reinforced concrete columns is considered load-bearing characteristic.

The main and most necessary technical property reinforced concrete columns are considered to be load-bearing characteristics. The better this value, the lower the installation of supports in the building is expected. Designs with the highest load-bearing parameter are indicated for use in lower floors or basements.

If the building is not one-story, it is customary to use supports whose structure has a pair of cantilever convexities. These convexities are located at a level of 3 meters. Thus, the end of the floor is marked, for this reason, floors are installed on them for the installation of the next level.

If it is necessary to install supports in one-story or industrial buildings, then such columns should be taller and without bulges.

Normative documents

This is important to take seriously. After all, exacting claims are made against them. These columns must meet all manufacturing norms and standards. These products are subject to a large number of inspections and tests for compliance technical specifications. All requirements and standards for this type of structure are specified in special GOSTs and Series.

What are they made of?

It is important to approach the selection of components for the production of such load-bearing products consciously, as this has a great influence on the final characteristics. Today, concrete grades M300, M400 and M600 are used in columns. Steel reinforcement is also carefully selected; unstressed and stressed reinforcement can be used. There is also a frame made of rigid wire inside. Thanks to this steel rod, the columns can be given special strength, stability and reliability.

Types of products

Reinforced concrete columns: a) solid, constant section in height; b) lattice, of variable cross-section in height.

There is some standard classification of these products according to individual features and subtleties finished design. By type, these products are divided into two main groups:

• using consoles (in turn, they are divided into rectangular and two-branch products);
• without using consoles.

There is a classification according to the section in the column:

• round section;
• rectangular section;
• square section.

Types of column sections: square, rectangular and round.

Classification by manufacturing technology:

• Monolithic technology. Possible production directly at construction site, using the technology of pouring concrete mixture into formwork with a previously installed frame.
• Prefabricated technology. Production takes place only in factory conditions.

Classification according to position

• supports located in the middle row;
• supports located in the outer row;
• supports located on the facade of the building.

Calculation features

Many technical specifications before working with the column, they are subject to careful calculations during the design process. Experts recommend using concrete mixtures marked from B15 to B25 for production. But for products that are used in the construction of low-rise buildings, grade B30 concrete is used.

Initially, using calculations, you need to find out the cross-sectional area of ​​the concrete product. This indicator will help maintain compression uniformity. The formula for calculating this indicator is F/Rb=A:

• compression force F;
• strength of concrete in compression Rb.

When the area indicator has been found, it is necessary to find out, taking into account the parameters responsible for the operating conditions, correct installation and other indicators that can increase the size of the section. Necessary calculations differ increased complexity, so unexpected errors occur quite often. Therefore, it is recommended to perform them not manually, but using special equipment. Although, if really necessary, it can be done without special equipment.

However, it is worth remembering that the calculation takes into account not only the strength of the support, but also the likelihood of its connection with the base and floor slabs of the structure.

For this reason, it is desirable to increase the design cross-section in order to strengthen reinforced concrete beams.

Installation of columns In low-rise buildings, the supports are installed entirely. If the support is too long, then it is transported to the site in parts and then assembled. Installation may occur different ways

, for example, in the foundation glass or on the column. Often the supports are mounted on a glass-type base. Filling concrete mixture

happens in advance. The width of the concrete layer depends not only on the project, but it is also necessary to take into account the length of the support that will be mounted on a given base, so that the deviation from the length of the support can be compensated for by the width of the layer. As preparatory work Before installing the supports, markings are made in necessary places base If the supports will be mounted under the beams, then mark the axes of the beams on the sides of the traverses.

Special clamps are installed on supports that are too long. Installation takes place using the “on weight” technology. The supports are captured using frame fasteners. Using a crane, the support is installed in the base glass, taking into account all the markings made. After this, using theodolites, the accuracy of the vertical immersion of the column is controlled. Before filling cavities concrete mortar

, the supports are secured using special metal or reinforced concrete wedges.

Throughout the entire installation process, it is important to strictly follow the standards prescribed in SNiPs or the project. Until the concrete in the cavities has completely hardened, other building elements cannot be lowered onto supports. Fastening the supports to the columns occurs in much the same way as in the case of glasses. The only difference is in the method of securing the connection - it is welded.

Frame for reinforced concrete columns. While the support is suspended, one of its faces is welded. occurs with the help of special braces. When the column is installed and everything is carefully checked, the junction of the support and the column is welded. And after that, everything on the outside is covered with concrete.

Reinforced concrete supports with a square cross-section are installed separately. However, sometimes, if the support has crossbars, they can be enlarged and installed using a crane. Typically, the lower supports are mounted in column sills or on a glass-type base. Next they are checked and secured. Next, the supports are mounted on the ends of the lower columns or on their crossbars.

There are a large number of methods for mounting, checking and fastening supports, each of them has its own disadvantages and advantages:

• mounting in accordance with the marks, checking the position with a plumb line and securing the joints by welding (usually performed when installing in column supports);
• mounting on the ends of the supports on which the conductors were previously attached, checking takes place along the alignment axes;
• mounting on the ends of the lower supports with temporary fastening, checking is carried out by a group conductor.