Are connections needed in frame structures? Layout of frame connections. Metal bracing structures of steel frame

CONNECTIONS in structures- lightweight structural elements in the form of individual rods or systems (trusses); designed to ensure spatial stability of the main load-bearing systems (trusses, beams, frames, etc.) and individual rods; spatial work of the structure by distributing the load applied to one or more elements over the entire structure; giving the structure the rigidity necessary for normal operating conditions; for the perception in some cases of wind and inertial (for example, from cranes, trains, etc.) loads acting on structures. Communication systems are arranged so that each of them performs several of the listed functions.

To create spatial rigidity and stability of structures consisting of flat elements (trusses, beams), which easily lose stability from their plane, they are connected along the upper and lower chords by horizontal connections. In addition, vertical connections - diaphragms - are installed at the ends, and for large spans and in intermediate sections. As a result, a spatial system is formed that has high rigidity during torsion and bending in the transverse direction. This principle of ensuring spatial rigidity is used in the design of many structures.

In the spans of beam or arch bridges, two main trusses are connected by horizontal bracing systems along the lower and upper chords of the trusses. These connection systems form horizontal trusses, which, in addition to providing rigidity, take part in the transfer of wind loads to the supports. To obtain the required torsional rigidity, transverse links are installed to ensure stability cross section bridge beam. In towers of square or polygonal cross-section, horizontal diaphragms are installed for the same purpose. In industrial and public buildings With the help of horizontal and vertical connections, two rafter trusses are connected into a rigid spatial block, to which the remaining roof trusses are connected by purlins or ties (ties). Such a block ensures the rigidity and stability of the entire coating system. The most developed system of connections has steel frames of single-story industrial buildings.

Systems of horizontal and vertical connections of lattice crossbars of frames (trusses) and lanterns provide the overall rigidity of the tent, secure compressed structural elements (for example, the upper chords of trusses) from loss of stability, and ensure the stability of flat elements during installation and operation. Taking into account the spatial work provided by the connection of the main load-bearing structures with bracing systems, when calculating structures, results in a reduction in the weight of structures. For example, taking into account the spatial work of the transverse frames of the frames of one-story industrial buildings results in a reduction in the calculated values ​​of moments in columns by 25-30%. A methodology for calculating spatial systems of span structures has been developed beam bridges. In ordinary cases, connections are not calculated, and their sections are assigned according to the maximum flexibility established by the standards.

Lateral stability of the frame wooden buildings is achieved by pinching the main pillars in the foundations while pivoting the covering structure with these pillars; application of frame or arched structures with hinged support; creation hard drive coating, which is used in small buildings. The longitudinal stability of the building is ensured by placing (after about 20 m) a special connection in the plane of the frame walls and the middle row of racks. Wall panels (panels), suitably fastened to frame elements, can also be used as connections.

To ensure the spatial stability of planar load-bearing wooden structures, appropriate connections are installed, which are fundamentally similar to the connections in metal or reinforced concrete structures. In arched and frame structures, in addition to the usual (as in beam trusses) bracing of the compressed upper chord, provision is made for bracing the lower chord, which, as a rule, has under one-sided loads, compressed areas. This bracing is carried out by vertical ties connecting the structures in pairs. In the same way, stability is ensured from the plane of the lower chords in trussed structures. Strips of oblique flooring and roof panels can be used as horizontal connections. Spatial wooden structures do not require special connections.

Frame connections provide geometric immutability and stability of elements in the longitudinal direction, joint spatial work of frame structures, building rigidity and ease of installation and consist of two main systems: connections between columns and coating connections.

Connections between columns. The connections between the columns (Fig. 6.4) ensure the geometric immutability of the frame and its structure during operation and installation. bearing capacity in the longitudinal direction, they perceive and transmit to the foundation wind loads acting on the end of the building and the effects of longitudinal braking of overhead cranes, and also ensure the stability of columns from the plane of the transverse frames.

The column bracing system consists of over-crane single-plane V-shaped ties, located in the plane of the longitudinal axes of the building, and sub-crane two-plane cross-shaped ties, located in the planes of the column branches.

Crane connections in each row of columns are located closer to the middle of the building block to ensure freedom of temperature deformations in both directions and reduce thermal stresses in the frame elements. The number of ties (one or two along the length of the block) is determined by their load-bearing capacity, the length of the temperature compartment and the greatest distance L with from the end of the building (expansion joint) to the axis of the nearest vertical connection (see Table 6.1). If there are two vertical connections, the distance between them in the axes should not exceed 40 - 50 m.

Over-crane connections are installed at the outermost column spacings at the end of the building or temperature block, as well as in places where vertical connections are provided in the plane of the support posts roof trusses.

Intermediate columns (outside the bracing blocks) at the level of the trusses are braced with spacers.

At high altitude in the crane part of the column, it is advisable to install additional horizontal struts between the columns, reducing their estimated length from the plane of the frame (shown with a dotted line in Fig. 6.4).

Vertical connections along columns are calculated for crane and wind loads W, based on the assumption of tensile work on one of the braces of the crane cross braces. At long length elements that perceive small forces, connections are taken to the utmost flexibility λ u = 200.

The tie elements are made from hot-rolled angles, the spacers are made from bent rectangular profiles.

Coverage connections. The coating bracing system consists of horizontal and vertical bracings that form rigid blocks at the ends of the building or temperature block and, if necessary, intermediate blocks along the length of the compartment (Fig. 6.5).

Horizontal connections in the plane of the lower chords of trusses are designed of two types. Ties of the first type consist of transverse and longitudinal braced trusses and braces (see Fig. 6.5, V G– at a step of 12 m). Ties of the second type consist of transverse braced trusses and braces (see Fig. 6.5, d– with a truss pitch of 6 m; see fig. 6.5, e– with a truss pitch of 12 m).

Rice. 6.4. Column connection diagram

6.5. Coverage connections

Rice. 6.5(continuation)

Transverse braced trusses along the lower chords of trusses are provided at the ends of the building or temperature (seismic) compartment (see Fig. 6.5, d, e). An additional horizontal braced truss is also provided in the middle of a building or compartment with a length of more than 144 m in buildings erected in areas with an estimated outside air temperature of –40 o C and above, and with a building length of more than 120 m in buildings erected in areas with design temperature below –40 o C (see Fig. 6.5, V, G). This reduces the transverse movements of the truss chord, which arise due to the compliance of the connections. Transverse horizontal connections at the level of the lower chords of the trusses are perceived wind load to the end of the building, transmitted by the upper parts of the half-timbered posts, and together with the transverse horizontal connections along the upper chords of the trusses and the vertical connections between the trusses, they provide the spatial rigidity of the coating.

Longitudinal horizontal connections in the plane of the lower chords of trusses are provided along the outer rows of columns in buildings:

– with overhead support cranes of groups of operating modes 7K and 8K, requiring the installation of galleries for passage along the crane tracks;

– with rafter trusses;

– with calculated seismicity 7, 8 and 9 points;

– with an elevation of the bottom of the trusses over 18 m, regardless of the lifting capacity of the cranes;

– in buildings with roofs on reinforced concrete slabs, equipped with overhead support cranes general purpose with a load capacity of over 50 tons with a truss spacing of 6 m and over 20 tons with a truss spacing of 12 m;

– in single-span buildings with a roof on a steel profiled deck, equipped with cranes with a lifting capacity of over 16 tons;

– with a truss pitch of 12 m using longitudinal half-timbering posts.

Transverse horizontal connections at the level of the upper chords of trusses are provided to ensure the stability of the chords from the plane of the trusses. Due to the lattice of cross braces along the upper chords of the trusses, the use of lattice girders is difficult and therefore transverse braces, as a rule, are not used. In this case, the decoupling of the trusses is ensured by a system of vertical connections between the trusses.

In buildings with roofs on reinforced concrete slabs, spacers are provided at the level of the upper chords of the trusses (see Fig. 6.5, A). In buildings with a roof on a steel profiled flooring, the spacers are located only in the space under the lanterns; the trusses are fastened to each other by purlins (see Fig. 6.5, b); with a calculated seismicity of 7, 8 and 9 points, transverse braced trusses or stiffening diaphragms are also provided, installed at the ends of the seismic compartment (see Fig. 6.5, and– with a truss pitch of 6 m; see fig. 6.5, To– with a truss pitch of 12 m), and additionally at least one for a compartment length of more than 96 m in buildings with a calculated seismicity of 7 points and with a compartment length of more than 60 m in buildings with a calculated seismicity of 8 and 9 points.

In stiffening diaphragms, the profiled flooring, in addition to the main functions of enclosing structures, performs the function of horizontal connections along the upper chords of the trusses. Transverse stiffening diaphragms and horizontal braced trusses absorb longitudinal design horizontal loads from the coating.

In buildings with a lantern, if an intermediate stiffening diaphragm is installed, the lantern above the diaphragm must be interrupted. Rigidity diaphragms are made from profiled flooring grades H60-845-0.9 or H75-750-0.9 in accordance with GOST 24045-94 with reinforced fastening to the purlins.

Rafter trusses that are not directly adjacent to the transverse braces are secured in the plane of location of these braces with spacers and braces. Spacers provide the necessary lateral rigidity of the trusses during installation (ultimate flexibility of the upper chord of the truss from its plane during installation λ u= 220). Stretches are provided to reduce the flexibility of the lower belt in order to prevent vibration and accidental bending during transportation. The maximum flexibility of the lower chord from the plane of the truss is assumed to be: λ u= 400 – with static load and λ u= 250 – with cranes operating in 7K and 8K operating modes or when exposed to dynamic loads applied directly to the truss.

For horizontal bracing, a triangular lattice braced truss is usually adopted. With a truss pitch of 12 m, the truss struts are designed with sufficiently high vertical rigidity (as a rule, from bent rectangular profiles) to support long diagonal braces made from angles with insignificant vertical rigidity.

Vertical connections between trusses are provided along the length of the building or temperature compartment in the locations of transverse braced trusses along the lower chords of the trusses. In buildings with a calculated seismicity of 7, 8 and 9 points and a roof on a steel profiled flooring along rows of columns, vertical braces are installed in the locations of braced trusses or stiffening diaphragms along the upper chords of the trusses.

The main purpose of vertical braces is to ensure the design position of the trusses during installation and to increase their lateral rigidity. Usually one or two vertical connections are installed along the width of the span (every 12 - 15 m).

When the lower assembly of the trusses is supported on the head of the column from above, the vertical connections are also located in the plane of the truss support posts. When the trusses are adjacent to the side of the column, these connections are located in a plane aligned with the plane of the vertical connections of the crane part of the column.

In the coatings of buildings operated in climatic regions with a design temperature below –40 o C, it is necessary, as a rule, to provide (in addition to the usually used braces) vertical braces located in the middle of each span along the entire building.

If there is a hard disk of the roof at the level of the upper chords of the trusses, inventory removable connections should be provided to align the design position of the structures and ensure their stability during the installation process.

Connections between columns.

The system of connections between the columns ensures during operation and installation the geometric immutability of the frame and its load-bearing capacity in the longitudinal direction, as well as the stability of the columns from the plane of the transverse frames.

The connections that form the hard disk are located in the middle of the building or temperature compartment, taking into account the possibility of columns moving due to thermal deformations of the longitudinal elements.

If you install connections (hard drives) at the ends of the building, then large thermal forces F t arise in all longitudinal elements (crane structures, rafter trusses, brace struts)

When the length of a building or temperature block is more than 120 m, two systems of tie blocks are usually installed between the columns.

Limit dimensions between vertical connections in meters

Dimensions in brackets are given for buildings operated at design outdoor temperatures t= –40° ¸ –65 °С.

The simplest bracing scheme is a cross one; it is used for column spacing up to 12 m. The rational angle of inclination of the bracings is therefore big step, but at high column heights, two cross connections are installed along the height of the lower part of the column.

In the same cases, sometimes additional decoupling of columns from the plane of the frame with spacers is designed.

Vertical connections are installed along all rows of the building. With a large pitch of columns in the middle rows, and also in order not to interfere with the transfer of products from bay to bay, connections of portal and semi-portal schemes are designed.

The vertical connections between the columns receive forces from the wind W 1 and W 2 acting on the end of the building and the longitudinal braking of the cranes T pr.

Elements of cross and portal connections work in tension. Due to their high flexibility, compressed rods are excluded from work and are not taken into account in the calculation. The flexibility of tensile tie elements located below the level of crane beams should not exceed 300 for ordinary buildings and 200 for buildings with “special” crane operating modes; for connections above crane beams - 400 and 300, respectively.

Coverage connections.

Connections along the roof (tent) structures or connections between the trusses create the overall spatial rigidity of the frame and provide: stability of the compressed chords of the trusses from their plane, redistribution of local crane loads applied to one of the frames to adjacent frames; ease of installation; specified frame geometry; perception and transmission of some loads to the columns.

Coverage connections are located:

1) in the plane of the upper chords of the trusses - longitudinal elements between them;

2) in the plane of the lower chords of trusses - transverse and longitudinal braced trusses, as well as sometimes longitudinal braces between transverse braced trusses;

3) vertical connections between trusses;

4) communications via lanterns.

Connections in the plane of the upper chords of the trusses.

The elements of the upper chord of the trusses are compressed, so it is necessary to ensure their stability from the plane of the trusses.

Reinforced concrete roofing slabs and purlins can be considered as supports that prevent the upper nodes from moving out of the plane of the truss, provided that they are secured against longitudinal movements by connections located in the plane of the roof. It is advisable to place such ties (transverse trusses) at the ends of the workshop so that they, together with transverse trusses along the lower chords and vertical ties between the trusses, create a spatial block that ensures the rigidity of the coating.

If the building or temperature block is longer, intermediate transverse braced trusses are installed, the distance between which should not exceed 60 m.

To ensure the stability of the upper chord of the truss from its plane within the lantern, where there is no roofing, special spacers are provided, and trusses are required in the ridge assembly. During the installation process (before installing the covering slabs or purlins), the flexibility of the upper chord from the plane of the truss should be no more than 220. Therefore, if the ridge spacer does not provide this condition, an additional spacer is placed between it and the spacer on the truss support (in the plane of the columns).

Connections in the plane of the lower chords of trusses

In buildings with overhead cranes, it is necessary to ensure horizontal rigidity of the frame both across and along the building.

When operating overhead cranes, forces arise that cause transverse and longitudinal deformations of the workshop frame.

If the lateral rigidity of the frame is insufficient, the cranes may jam during movement and normal operation will be disrupted. Excessive vibrations of the frame create unfavorable conditions for the operation of cranes and the safety of enclosing structures. Therefore, in single-span buildings of great height (H>18 m), in buildings with overhead cranes Q>100 kN, with cranes of heavy and very heavy operating modes with any load capacity, a system of connections along the lower chords of the trusses is required.

Horizontal forces F from overhead cranes act transversely on one flat frame or two or three adjacent ones.

Longitudinal braced trusses provide working together systems of flat frames, as a result of which the transverse deformations of the frame from the action of concentrated force are significantly reduced.

The end frame posts transmit the wind load F W to the nodes of the transverse braced truss.

To avoid vibration of the lower chord of the truss due to the dynamic impact of overhead cranes, the flexibility of the stretched part of the lower chord from the plane of the frame is limited: for cranes with a number of loading cycles of 2 × 10 6 or more - by a value of 250, for other buildings - by a value of 400. To reduce the length of the stretched part of the lower In some cases, belts are equipped with stretchers that secure the lower belt in the lateral direction.

Vertical connections between farms.

These ties connect the trusses together and prevent them from tipping over. They are installed, as a rule, in axes where connections are established along the lower and upper chords of the trusses, forming together with them a rigid block.

In buildings with suspended transport, vertical connections contribute to the redistribution between the trusses of the crane load applied directly to the covering structures. In these cases, as well as to the rafter trusses, an electric crane is attached - beams of significant lifting capacity; vertical connections between the trusses are located in the suspension planes continuously along the entire length of the building.

The structural diagram of the connections depends mainly on the pitch of the trusses.

Ties along the upper chords of trusses

Ties along the lower chords of trusses

For horizontal connections with a truss pitch of 6 m, a cross lattice can be used, the braces of which work only in tension (Fig. a).

Recently, braced trusses with a triangular lattice have been mainly used (Fig. b). Here the braces work in both tension and compression, so it is advisable to design them from pipes or bent profiles, allowing to reduce metal consumption by 30-40%.

With a truss pitch of 12 m, the diagonal bracing elements, even those working only in tension, turn out to be too heavy. Therefore, the bracing system is designed so that the longest element is no more than 12 m, and the diagonals are supported by this element (Fig. c, d).

It is possible to ensure fastening of longitudinal braces without a grid of braces along the upper chord of the trusses, which does not make it possible to use through purlins. In this case, the rigid block includes covering elements (purlins, panels), trusses and often located vertical braces (Fig. e). This solution is currently standard. The connection elements of the tent (covering) are calculated, as a rule, based on flexibility. The maximum flexibility for compressed elements of these connections is 200, for stretched elements - 400, (for cranes with a number of cycles of 2 × 10 6 or more - 300).

System structural elements, serving to support the wall fence and absorb wind loads called half-timbered.

Half-timbered structures are installed for loaded walls, as well as for interior walls and partitions.

With self-supporting walls, as well as with panel walls with panel lengths equal to the column spacing, there is no need for half-timbered structures.

With a pitch of external columns of 12 m and wall panels 6 m long intermediate half-timbered posts are installed.

Half-timbering installed in the plane of the longitudinal walls of a building is called longitudinal half-timbering. A half-timbering installed in the plane of the walls at the end of a building is called an end half-timbering.

The end timber frame consists of vertical posts, which are installed every 6 or 12 m. The upper ends of the posts in the horizontal direction rest on a transverse braced truss at the level of the lower chords of the trusses.

In order not to prevent the deflection of trusses from temporary loads, the support of the half-timbered posts is carried out using sheet hinges, which are a thin sheet t = (8 10 mm) with a width of 150-200 mm, which easily bends in the vertical direction without interfering with the deflection of the truss; in the horizontal direction it transmits force. Crossbars are attached to the half-timbered posts for window openings; when the height of the racks is high, spacers are placed in the plane of the end wall to reduce their free length.

Walls made of bricks or concrete blocks are designed to be self-supporting, i.e. taking up their entire weight, and only the lateral load from the wind is transferred by the wall to the column or half-timbered post.

Walls made of large-panel reinforced concrete slabs are installed (hung) on ​​tables of columns or half-timbered posts (one table every 3 - 5 slabs in height). In this case, the half-timbered post works in eccentric compression.

Steel structures of one-story industrial buildings

Steel frame an industrial building consists of the same elements as reinforced concrete, only the frame material is steel.

Application steel structures appropriate for:

1. for columns: with a pitch of 12 m or more, a building height of more than 14.4 m, a two-tier arrangement of overhead cranes, with a lifting capacity of the cranes of 50 tons or more, under heavy operating conditions;

2. for truss structures: in heated buildings with a span of 30 m or more; in unheated buildings 24 m or more; above hot shops, in buildings with high dynamic loads; in the presence of steel columns.

3. for crane beams, lanterns, crossbars and half-timbered posts

Columns

Columns are designed:

· single-branch solid-walled of constant cross-section with a building height of 6 - 9.6 m, span 18, 24 m (series 1.524-4, issue 2),

· two-branch with a building height of 10.8-18 m, a span of 18.24,30.36 m (series 1,424-4, issues 1 and 4),

· separate type, used in buildings with a large load capacity and a height of more than 15 m.

Hanging equipment

For building heights up to 7.2, overhead cranes are not provided, only suspended equipment with a lifting capacity of up to 3.2 tons; in buildings 8.4-9.6, overhead cranes with a lifting capacity of up to 20 tons can be used.

Columns are designed in two versions: with passages and without passages. For columns without passages, the distance from the centering axis to the axis of the crane rail is 750 mm, for columns with passages - 1000 mm. The upper part of the column is I-beam, the lower of two branches connected by a lattice of rolled angles, which are welded to the flanges of the branches.

Column design

The column spacing is recommended for craneless buildings and with suspended equipment in the outer rows - 6 m, in the middle - 6, 12 m; with overhead cranes in the outer and middle rows - 12 m. In order to unify the columns, their lower ends should be located at a level of 0.6 m. To protect against corrosion, the underground part of the columns together with the base is covered with a layer of concrete.

Main column height parameters:

H in - the height of the upper part,

· H n - height of the lower part, mark of the head of the crane rail, height of the branch section h.

In the middle rows with a difference in height, one row of columns can be installed in the frames, but along the line of the difference it is necessary to provide two alignment axes with an insert between them. The upper part of such columns is assumed to be the same as the upper part of the outermost columns, i.e. has a reference of 250 mm. The second alignment axis is aligned with the outer edge of the top of the columns.

Farms

Cover trusses are used in single and multi-span buildings with reinforced concrete or steel columns with a length of 18, 24, 30, 36 m, the column spacing is 6.12 m. They consist of the truss itself and support posts. The support of the truss on columns or rafter trusses is assumed to be hinged.

They are manufactured in three types: with parallel belts, polygonal, triangular.

Truss structures:

· Trusses with parallel chords with a span of 18 m, the slopes are 1.5% only in the upper zone, the rest of both the upper and lower zones. The height of the truss on the support is 3150 mm - along the edges, and 3300 mm - the full height with the stand, the nominal length is 400 mm less than the span. (200 mm of outer compartments). Reinforced concrete slabs are directly supported on the upper chord of the truss, reinforced with overlays at the points of support and are welded. Covered with Prof. The flooring uses purlins 6 m long, which are installed on the upper chord and fastened with bolts; lattice purlins 12 m long are welded.

· Farms from round pipes (20% more economical, less susceptible to corrosion due to the absence of cracks and sinuses) series 1,460-5. are intended only for professional use. flooring, the lower belt is horizontal, the upper one with a slope of 1.5%, the height on the support is 2900 mm, the full height is 3300, 3380 mm, the nominal length is also 400 mm. Briefly speaking.

· Farms with an upper chord slope of 1:3.5 ( triangular), designed for single-span, lanternless, unheated storage facilities with external drainage, series PK-01-130/66 for covering with purlins.

· Rafter trusses designed with parallel belts, the height of the butts is 3130 mm, the total height is 3250 mm. Support stand The truss truss is made of a welded I-beam with a table in the lower part for supporting the trusses. Rafter structures with a span of 12 m are installed on reinforced concrete or steel trusses. Span 18.24 m only on steel.

· Half-timbered in a steel frame they are arranged: with walls made of sheet material or panels, in buildings with a height of more than 30 m, regardless of the wall structure, in buildings with heavy duty crane operation brick walls, in prefabricated buildings, for temporary portable end walls during the construction of a building in several stages. A half-timbered structure consists of posts and crossbars. Their number and location are determined by the pitch of the columns, the height of the building, the design of the wall filling, the nature and magnitude of the load, and the location of the openings. The upper ends of the half-timber posts are attached to the covering trusses or bracings using curved plates.

Communication system:

The system of connections in the covering consists of horizontal in the plane of the upper and lower chords of the trusses and vertical ones between the trusses.

The system is designed to ensure spatial operation and impart spatial rigidity to the frame, absorb horizontal loads, and ensure stability during installation; if the building consists of several blocks, each block has an independent system.

If the roof of the building is made of reinforced concrete slabs, then the connections along the upper chord consist of struts and braces; horizontal connections are provided only in lantern buildings and are located in the space under the lanterns. The connections are secured with bolts.

Horizontal connections along the lower chords

Horizontal connections along the lower chords are of two types:

The first type of transverse braced trusses is used when the pitch of the outer columns is 6 m and is located at the ends of the temperature compartment; when the length of the compartment is more than 96 m, additional trusses are installed with a pitch of 42-60 m. In addition, longitudinal horizontal trusses are used, which are located along the outer columns, as needed and on average.

These connections are used in buildings: one- and two-span with cargo cranes. 10 tons or more; in buildings of three or more spans with a general cargo load. 30 tons or more.

In other cases, connections of type 2 are used - the second type is used when the pitch of the outer columns is 12 m and are located similarly to the first type.

The connections are fastened with bolts for heavy-duty welding work.

Vertical connections

Vertical braces are located along the spans, at the locations of transverse horizontal trusses every 6 m, and are fastened with bolts or welding, depending on the effort.

When used in coating prof. for flooring, purlins are used, which are located in increments of 3 m; in the presence of height differences, 1.5 m is allowed. Prof. the flooring is attached to the purlins using self-tapping screws.

Vertical connections between steel columns, provided in each longitudinal row of columns, are divided into main and upper.

The main ones ensure the invariability of the frame in the longitudinal direction and are located along the height of the crane part of the column in the middle of the building or temperature compartment. Cross, portal or semi-portal are designed.

The upper ties, which ensure the correct installation of the column heads during installation and the transfer of longitudinal forces from the upper sections of the end walls to the main ties, are placed within the crane part of the column along the edges of the temperature compartment. In addition, these connections are arranged in those panels where vertical and transverse horizontal connections between the covering trusses are located. They are designed in the form of struts, crosses, struts and trusses.

Ties are made from channels and angles, fastened to columns with black bolts, in buildings with a large load-bearing capacity for heavy duty use - by installation welding, clean bolts or rivets.

Crane structures

Suspended tracks They are usually made from rolled I-beams of type M with joints arranged outside the supports. These tracks are suspended from the lower chords of the supporting structures using bolts, followed by welding.

Crane structures for overhead cranes consist of crane beams, receiving vertical and local forces from crane rollers; brake beams or trusses, cranes that perceive horizontal impacts; vertical and horizontal connections, ensuring rigidity and immutability of structures.

Crane steel Depending on the static design, beams are divided into split and continuous. Predominantly split ones are used. They are simple in design, less sensitive to support settlements, and easy to manufacture and install, but compared to continuous ones they have a greater height and complicate the operating conditions of crane runways and require greater steel consumption.

According to the type of section, crane beams can be of solid or through (lattice) section

Crane beams series 1.426-1 in the form of a welded I-beam with symmetrical belts or not, span 6, 12, 24 m, heights: with a length of 6 m - 800, 1300 mm; with a length of 12 m - 1100,1600 mm. The section height of solid beams is 650-2050 mm with a gradation of 200 mm. The beams are equipped ribs rigidity to ensure the stability of the walls, located every 1.5 m. The beams are middle and outer (located at the ends and at the expansion joint, one of the supports is moved back by 500 mm). The support of beams on the column consoles is hinged: for ordinary beams - on bolts, for braced beams - on bolts and installation welding.

Brake structures They are connections along the upper chords of crane beams, which are selected depending on the availability of passages and the span of the beam.

At the level of crane runways, spans with heavy-duty overhead cranes are provided with platforms for through passages. Platforms must be at least 0.5 m wide with railings and stairs. Where columns are located, passages are arranged on the side or through openings in them.

Depending on the lifting capacity of the cranes and the type of running wheels for crane tracks Railway rails, KR profile rails or block profile rails are used. The fastening of rails to beams can be fixed or movable.

Fixed fastening, allowed for light operation of cranes with a lifting capacity of up to 30 tons and medium-duty operation with a lifting capacity of up to 15 tons, is ensured by welding the rail to the beam. In most cases, the rails are attached to the beams in a movable manner, which allows straightening of the rails. At the ends of the crane tracks, shock absorbers are installed to prevent impacts on the end walls of the building.

Used in industrial buildings mixed frames(reinforced concrete columns and metal trusses) under the conditions:

· the need to create large spans;

· to reduce weight from coating elements.

The fastening of steel trusses to reinforced concrete columns is carried out using bolted connections followed by welding. For this purpose, anchor bolts are provided at the column head.

The main elements of the frame are frames. They consist of columns and supporting structures of coverings - beams or trusses, long floorings, etc. These elements are hingedly connected at the nodes using metal embedded parts, anchor bolts and welding. Frames are assembled from standard factory-made elements. Other frame elements are foundation, strapping and crane beams and rafter structures. They ensure the stability of the frames and absorb loads from the wind acting on the walls of the building and lanterns, as well as loads from cranes.

Components of the frame of one-story industrial buildings

As an example, a single-span building equipped with an overhead crane (Fig. 1).

The frame consists of the following main elements:

1. Columns located at W steps along the building; The main purpose of the columns is to support the crane beams and roofing.
2. Load-bearing structures of the covering (rafters* beams or trusses), which rest directly on the columns (if their pitch coincides with the pitch of the columns) and together with them form the transverse frames of the frame.
3. If the pitch of the load-bearing structures of the coating does not coincide with the pitch of the columns (for example, 6 and 12 m), sub-rafter structures located in longitudinal planes (also in the form of beams or trusses) are introduced into the frame, supporting intermediate load-bearing structures of the coating located between the columns (Fig. 1,b).
4. In some (rare) cases, purlins are included in the frame, resting on the load-bearing structures of the coating and located at distances of 1.5 or 3 m.
5. Crane beams supported on columns and load-bearing tracks of overhead cranes. In buildings with overhead or floor cranes, crane beams are not needed.
6. Foundation beams that rest on column foundations and support the exterior walls of a building.
7. Strapping beams resting on columns and supporting individual tiers outer wall(if it does not rest on foundation beams throughout its entire height).
8. When the distance between the main columns of the frame, in the planes of the external walls is 12 m or more, as well as at the ends of the building, auxiliary columns (half-timbered structures) are installed to facilitate the construction of the walls.

Rice. 1. Frame of a one-story, single-span building (diagram):

a - with the same spacing of columns and load-bearing structures of the coating; b - with unequal spacing of columns and load-bearing structures of the coating; 1 - columns; 2 - load-bearing structures of the coating; 3 - rafter structures; 4 -- runs; 5 - crane beams; 6 - foundation beams; 7 - strapping beams; c - longitudinal connections of columns; 9 - longitudinal vertical connections of the coating; 10 - transverse horizontal connections of the coating; 11 - longitudinal horizontal connections of the coating.

In steel frames, strapping beams are also classified as half-timbering (Fig. 2, a). The frame as a whole must operate reliably and stably under the influence of crane, wind and other loads.

Rice. 2 Schemes of half-timbering

a - longitudinal wall half-timbering, b - end half-timbering, 1 - main columns, 2 - half-timbering columns, 3 - half-timbering crossbar, 4 - roof truss

Vertical loads P from a bridge crane (Fig. 3), transmitted through crane beams to columns with a large eccentricity, cause eccentric compression of those columns against which it is located this moment crane bridge.

Rice. 3. Overhead crane diagram

1 - crane dimensions, 2 - trolley, 3 - crane bridge, 4 - hook, 5 - crane wheel; 6 - crane rail; 7 - crane beam; 8 - column

The braking of the overhead crane trolley as it moves along the crane bridge (across the span) creates horizontal transverse braking forces T1 acting on the same columns.

The braking of the overhead crane as a whole as it moves along the span creates longitudinal braking forces T2 acting along the rows of columns. With the lifting capacity of overhead cranes reaching 650 tons and above, the loads they transmit to the frame are very large. Suspended cranes They move along paths suspended from the load-bearing structures of the coating, and through them they transfer their loads to the columns.

Wind loads in different wind directions can act on the frame in both transverse and longitudinal directions.

To ensure the stability of individual elements of the frame during its installation and their joint spatial operation when various loads are applied to the frame, connections are introduced into the frame.

Main types of frame connections for one-story buildings

1. Longitudinal connections columns, ensuring their stability and joint work in the longitudinal direction during the longitudinal braking of the crane and the longitudinal action of the wind, are installed at the end or in the middle of the length of the frame.

The stability of the remaining columns in the longitudinal plane is achieved by fastening them to the bracing columns with horizontal longitudinal frame elements (crane beams, strapping beams or special spacers).

Connections of this type may have different scheme depending on the requirements for the designed building. The simplest are cross connections (Fig. 4, a). In cases where they interfere with the installation of equipment or cut into the clearance of the passage (Fig. 4, b), they are replaced with portal connections.

In craneless buildings of small height such connections are not needed. The operation of columns in the transverse direction in all cases is ensured by their large cross-sectional dimensions in this direction and their rigid fastening to the foundations.

Fig.4. Scheme of vertical connections along columns. 1 - columns, 2 - covering, 3 - connections, 4 - passage

2. Longitudinal vertical connections of the coating, ensuring the stability of the vertical position of the load-bearing structures (trusses) of the covering on the columns, since their attachment to the columns is considered hinged, are located at the ends of the frame. The stability of the remaining trusses is achieved by attaching them to the braced trusses with horizontal struts.

3. Transverse horizontal connections, ensuring the stability of the upper compressed chord of the trusses against longitudinal bending, are located at the ends of the frame and are formed by combining the upper chords of two adjacent trusses into a single structure, rigid in the horizontal plane. The stability of the upper chords of the remaining trusses is achieved by attaching them to the braced trusses in the plane of the upper chord using spacers (or enclosing covering elements).

4. Longitudinal horizontal connections of the coating, located along the external walls at the level of the lower chord of the trusses.

All three types of coating connections are intended to combine individual flat load-bearing elements coverings that are rigid only in the vertical plane into a single unchangeable spatial structure that absorbs local horizontal loads from cranes and wind loads and distributes them between frame columns.

The frames of one-story industrial buildings are most often erected from precast reinforced concrete; steel structures are allowed only in the presence of particularly large loads, spans or other conditions that make the use of reinforced concrete inappropriate. The consumption of steel in reinforced concrete structures is less than in steel ones: in columns - 2.5-3 times; in coating farms - 2-2.5 times. Types of industrial buildings on one floor.

However, the cost of steel and reinforced concrete structures of the same purpose differs slightly and currently frames are made mainly of steel.

The complex of connections described above in the most complete and clear form is found in steel frames, individual elements which have particularly low rigidity. More massive elements of reinforced concrete frames also have greater rigidity. Therefore, in reinforced concrete frames individual species connections may be missing. For example, in a building without lanterns, with load-bearing structures, coverings in the form of beams and a flooring made of large-panel slabs, no connections are made in the covering.

In monolithic reinforced concrete frames (which are very rare in domestic practice), the rigid connection of frame elements at nodes and the large mass of elements make all types of connections unnecessary.

The connections are most often made of metal - from rolled profiles. In reinforced concrete frames there are also reinforced concrete connections, mainly in the form of spacers.

The frame of a multi-span building differs from the frame of a single-span building primarily by the presence of internal middle columns that support the covering and crane beams. Foundation beams along the internal rows of columns are installed only to support the internal walls, and strapping beams - when their height is large. Connections are designed according to the same principles as in single-span buildings.

With seasonal temperature fluctuations, frame structures experience thermal deformations, which can be quite significant if the frame is long and there is a significant temperature difference. For example, with a frame length of 100 m, a linear expansion coefficient α = 0.00001 and a temperature difference of 50° (from +20° in summer to -30° in winter), i.e. for structures located at outdoors, the deformation is 100 0.00001 50 = 0.05 m - 5 cm.

Free deformations of the horizontal frame elements are prevented by columns rigidly attached to the foundations.

In order to avoid the appearance of significant stresses in structures from this reason, the frame is divided in the above-ground part by expansion joints into separate independent blocks.

The distances between the expansion joints of the frame along the length and width of the building are chosen so that the forces arising in the frame elements from climatic temperature fluctuations can be ignored.
Limit distances between expansion joints for frames made of various materials installed by SNiP within the range of 30 m (open monolithic reinforced concrete structures) up to 150 m (steel frame of heated buildings).

An expansion joint, the plane of which is perpendicular to the spans of the building, is called transverse, a joint separating two adjacent spans is called longitudinal.

The design of expansion joints varies. Transverse seams are always carried out by installing paired columns, longitudinal seams are made both by installing paired columns (Fig. 5, a) and by installing movable supports (Fig. 5, b), ensuring independent deformation of the coating structures of adjacent temperature blocks. In frames divided by expansion joints into separate blocks, connections are installed in each block, as in an independent frame.

Fig.5. Options for longitudinal expansion joint

a - with two columns, b - with a movable support, 1 - beams, 2 - table, 3 - column, 4 - roller

The frame also includes the load-bearing structures of work platforms, which are sometimes necessary inside the main volume of the building (if they are connected to the main structures of the building).

Work platform structures consist of columns and floors resting on them. Depending on the technological requirements, working platforms can be located on one or several levels (Fig. 6).

Rice. 6. Multi-tiered work platform.

Thus, in the construction of single-story and multi-story industrial buildings, as a rule, the load-bearing material is taken frame system. The frame allows the best way organize a rational layout industrial building(to obtain large-span spaces free from supports) and is most suitable for absorbing significant dynamic and static loads to which an industrial building is exposed during operation.

Video - step-by-step assembly of metal structures