CONNECTIONS IN CONSTRUCTIONS- light structural elements in the form of separate rods or systems (trusses); designed to ensure the spatial stability of the main bearing systems (trusses, beams, frames, etc.) and individual rods; spatial work of the structure by distributing the load applied to one or more elements to the entire structure; giving the structure the rigidity required 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 ties. In addition, at the ends, and for large spans and in intermediate sections, vertical links- diaphragms. As a result, a spatial system is formed, which has high rigidity in torsion and bending in the transverse direction. This principle of providing spatial rigidity is used in the design of many structures.
In span structures of beam or arch bridges, two main trusses are connected horizontal systems connections along the lower and upper belts of farms. These communication systems form horizontal trusses, which, in addition to providing rigidity, take part in the transfer of wind loads to the supports. To obtain the necessary torsional rigidity, cross-links are placed to ensure the invariability of the cross-section of the bridge beam. In towers of square or polygonal section, horizontal diaphragms are arranged for the same purpose. In coatings of industrial and public buildings with the help of horizontal and vertical ties, two truss trusses are connected into a rigid spatial block, with which the rest of the roof trusses are connected by girders or strands (ties). Such a block ensures the rigidity and stability of the entire coating system. The most developed system of connections has steel frames of one-story industrial buildings.
The 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 from loss of stability (for example, the upper chords of trusses), ensure the stability of flat elements during installation and operation. Accounting for the spatial work provided by the connection of the main load-bearing structures connection systems, when calculating structures, it gives a reduction in the weight of structures. So, for example, taking into account the spatial work of the transverse frames of the frames of one-story industrial buildings reduces the calculated values of the moments in the columns by 25-30%. A method for calculating the spatial systems of span structures of girder bridges has been developed. In normal cases, bonds are not calculated, and their sections are assigned according to the maximum flexibility established by the norms.
Lateral frame stability wooden buildings is achieved by pinching the main posts in the foundations when the roof structure is hinged to these posts; use of frame or arched structures with articulated support; creation hard drive coating, which is used in small buildings. The longitudinal stability of the building is ensured by setting (after about 20 m) a special connection in the plane frame walls and the middle row of racks. Wall panels (panels) can also be used as connections, properly fastened to the frame elements.
To ensure the spatial stability of planar load-bearing wooden structures, appropriate connections are placed, which are fundamentally similar to connections in metal or reinforced concrete structures. In arched and frame structures, in addition to the usual (as in beam trusses) unfastening of the compressed upper chord, it is provided for unfastening the lower chord, which, as a rule, with unilateral loads, compressed areas. This fastening 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. As horizontal ties, strips of slanting flooring and roof shields can be used. Spatial wooden structures in special connections dont need.
Frame ties provide geometric stability 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: ties between columns and cladding ties.
Links between columns. The connections between the columns (Fig. 6.4) ensure the geometric invariability of the frame and its bearing capacity in the longitudinal direction, 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 the columns from the plane of the transverse frames.
The column bracing system consists of over-crane single-plane braces V-pattern located in the plane of the longitudinal axes of the building, and crane two-plane cross scheme, located in the planes of the branches of the column.
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 links (one or two along the length of the block) is determined by their bearing capacity, the length of the temperature compartment and the largest 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 extreme steps of the columns 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 bracing blocks) at the level of truss trusses are braced with spacers.
With a high height of the crane part of the column, it is advisable to install additional horizontal spacers between the columns, which reduce their estimated length from the plane of the frame (shown in dotted lines in Fig. 6.4).
Vertical connections on columns are calculated for crane and wind loads W, based on the assumption of tensile work of one of the braces of cross crane ties. With a large length of elements that perceive small forces, connections are accepted according to the ultimate flexibility λu = 200.
Tie elements are made of hot-rolled angles, spacers are made of bent rectangular profiles.
Cover links. The coating tie system consists of horizontal and vertical ties 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 roof trusses are designed in two types. The bonds of the first type consist of transverse and longitudinal truss trusses and stretch marks (see Fig. 6.5, in G- at a step of 12 m). The connections of the second type consist of transverse truss trusses and stretch marks (see Fig. 6.5, d- with a truss step of 6 m; see fig. 6.5, e- with a truss step of 12 m).
Rice. 6.4. Scheme of connections by columns
6.5. Coverage links
Rice. 6.5(continuation)
Transverse braced trusses along the lower chords of truss trusses are provided at the ends of the building or temperature (seismic) compartment (see Fig. 6.5, d, e). One additional horizontal truss is also provided in the middle of the building or compartment with a length of more than 144 m in buildings erected in areas with an estimated outdoor temperature of -40 ° C and above, and with a building length of more than 120 m in buildings erected in areas with design temperature below -40 ° C (see Fig. 6.5, in, G). This reduces the transverse movement of the truss belt, which occurs due to the compliance of the bonds. Transverse horizontal connections at the level of the lower truss chords perceive wind load at the end of the building, transmitted upper parts half-timbered racks, and together with transverse horizontal ties along the upper chords of trusses and vertical ties between trusses provide spatial rigidity of the coating.
Longitudinal horizontal connections in the plane of the lower chords of roof trusses are provided along the extreme rows of columns in buildings:
– with overhead cranes of operating modes groups 7K and 8K, requiring the installation of galleries for passage along the crane tracks;
– with truss trusses;
– with estimated seismicity of 7, 8 and 9 points;
– with a mark of the bottom of the trusses over 18 m, regardless of the lifting capacity of the cranes;
– in buildings with roofs reinforced concrete slabs equipped with overhead cranes general purpose with a load capacity of over 50 tons with a truss pitch of 6 m and over 20 tons with a truss pitch of 12 m;
– in single-span buildings with roofing on profiled steel flooring, equipped with cranes with a lifting capacity of more than 16 tons;
– with a truss spacing of 12 m using longitudinal half-timbered racks.
Transverse horizontal connections at the level of the upper chords of truss trusses are provided to ensure the stability of the chords from the plane of the trusses. Due to the lattice of cross ties along the upper chords of trusses, the use of lattice runs is difficult and therefore, as a rule, cross ties are not used. In this case, the decoupling of farms is provided by a system of vertical connections between farms.
In buildings with a roof on reinforced concrete slabs, spacers are provided at the level of the upper chords of truss trusses (see Fig. 6.5, a). In buildings with a roof on a steel profiled flooring, the spacers are located only in the under-lantern space, the trusses are fastened together by girders (see Fig. 6.5, b); with a design 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, well- with a truss step of 6 m; see fig. 6.5, to- with a truss spacing of 12 m), and additionally at least one with a compartment length of more than 96 m in buildings with a design seismicity of 7 points and with a compartment length of more than 60 m in buildings with a design seismicity of 8 and 9 points.
In stiffening diaphragms, profiled flooring, in addition to the main functions of enclosing structures, performs the function of horizontal ties along the upper chords of truss trusses. Transverse stiffening diaphragms and horizontal braced trusses perceive longitudinal calculated horizontal loads from the coating.
In buildings with a lantern, in the case of an intermediate stiffening diaphragm, the lantern above the diaphragm must be interrupted. Rigidity diaphragms are made of profiled flooring grades H60-845-0.9 or H75-750-0.9 according to GOST 24045-94 with reinforced fastening to the girders.
Roof trusses that are not directly adjacent to the cross braces are braced in the plane of the location of these braces with braces and stretch marks. The spacers provide the necessary lateral rigidity of the trusses during installation (the ultimate flexibility of the upper chord of the truss from its plane during installation λu= 220). The braces are provided to reduce the flexibility of the lower belt in order to prevent vibration and accidental bending during transport. The limiting flexibility of the lower chord from the truss plane is taken: λu= 400 - at static load and λu= 250 - with cranes operating modes 7K and 8K or under the influence of dynamic loads applied directly to the truss.
For horizontal ties, a truss with a triangular lattice is usually adopted. With a truss spacing of 12 m, the rack-struts of the braced trusses are designed with sufficiently high vertical rigidity (as a rule, from bent rectangular profiles) to support long diagonal braces on them, made of corners with low vertical rigidity.
Vertical links between the trusses are provided along the length of the building or the temperature compartment at the locations of the transverse truss trusses along the lower chords of the trusses. In buildings with a design seismic activity of 7, 8 and 9 points and roofing on profiled steel flooring along rows of columns, vertical ties are installed at the locations of truss trusses or stiffening diaphragms along the upper chords of truss trusses.
The main purpose of vertical ties is to ensure the design position of the trusses during installation and increase their lateral rigidity. Usually one or two vertical connections are arranged along the width of the span (in 12 - 15 m).
When supported bottom node roof trusses on the head of the column from above, vertical ties are also located in the plane of the truss support posts. When the roof trusses adjoin the column on the side, these connections are located in a plane aligned with the plane of the device for vertical connections of the over-crane part of the column.
In the coatings of buildings operated in climatic regions with an estimated temperature below -40 ° C, it should, as a rule, provide (in addition to the commonly used ties) vertical ties located in the middle of each span along the entire building.
In the presence of 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 installation.
2.3.2. Links between columns
The purpose of the connections: 1) the creation of the longitudinal rigidity of the frame, necessary for its normal operation; 2) ensuring the stability of the columns from the plane of the transverse frames; 3) the perception of the wind load acting on the end walls of the building, and the longitudinal inertial effects of overhead cranes.
Connections are established along all longitudinal rows of building columns. Schemes of vertical connections between columns are given in Fig. 2.34. Schemes (Fig. 2.34, c, d, f) refer to buildings without cranes or with overhead crane equipment, all the rest - to buildings equipped with overhead cranes.
In buildings equipped with overhead cranes, the main ones are the lower vertical connections. They, together with two columns, crane beams and foundations (Fig. 2.34 d, f...l) form geometrically invariable discs fixed in the longitudinal direction. The freedom or constraint of deformation of other frame elements attached to such disks depends significantly on the number of rigid blocks and their location along the frame. If you place the communication blocks at the ends of the temperature compartment (Fig. 2.35, a), then with an increase in temperature and the absence of freedom of deformation ( t 0) loss of stability of the compressed elements is possible. That is why it is better to place vertical connections in the middle of the temperature block (Fig. 2.34, a...in, rice. 2.35 b), providing freedom of temperature movements on both sides of the connection block (Δ t 0) and eliminating the appearance of additional stresses in the longitudinal elements of the frame. At the same time, the distance from the end of the building (compartment) to the axis of the nearest vertical connection and the distance between the connections in one compartment should not exceed the values \u200b\u200bgiven in Table. 1.2.
In the overhead part of the columns, vertical connections should be provided at the ends of the temperature blocks and at the locations of the lower vertical connections (see Fig. 2.34 a, in). The expediency of installing top connections at the ends of the building is due, first of all, to the need to create the shortest path for transferring the wind load Rw on the end of the building along the longitudinal tie elements or crane beams on the foundations (Fig. 2.36). This load is equal to the support reaction of a horizontal truss truss (see Fig. 2.30) or two trusses in multi-span
Rice. 2.35. Influence of layouts of connection blocks on the development of temperature deformations:
a- when the connection blocks are located at the ends; b- the same, in the middle of the building
buildings. Similarly, forces from longitudinal braking of cranes are transferred to the foundations F cr(Fig. 2.36). The calculated longitudinal braking force is taken from two cranes of one or adjacent spans. In long buildings, these force effects are distributed equally to all vertical braced trusses between columns within the temperature block.
The constructive scheme of connections depends on the pitch of the columns and the height of the building. Various options the solutions of the connections are shown in fig. 2.34. The most common is the cross scheme (Fig. 2.34, Mrs.), as it provides the simplest and most rigid tying of building columns. The number of panels in height is assigned in accordance with the recommended angle of inclination of the braces to the horizontal (α = 35°...55°). If it is necessary to use the space between columns, which is often due to technological process, the connections of the lower tier are designed portal (Fig. 2.34 to) or semi-portal (see Fig. 2.34, l).
Vertical connections between columns are also used for fixing spacers in nodes (Fig. 2.34 e...and), if they are provided to reduce the effective lengths of the columns from the planes of the frames.
In columns with a constant section height h≤ 600 mm, connections are placed in the plane of the axes of the columns; in stepped communication columns above
Rice. 2.36. Schemes of transmission of wind (from the end of the building) and longitudinal crane loads:
a, b- buildings with overhead cranes; c, g- buildings with overhead cranes
brake structure (upper vertical connections) with h≤ 600 mm are installed along the axes of the columns, below the crane beam (lower vertical ties) when h> 600 mm - in the plane of each shelf or column branch. Connection nodes between columns are shown in fig. 2.37.
The connections are fastened on bolts of coarse or normal accuracy, and after the alignment of the columns, they can be welded to the packings. In buildings with overhead cranes of the 6K ... 8K operating mode groups, the gussets of the connections should be scalded or connections made on high-strength bolts.
When calculating links, you can use the recommendations of clause 6.5.1.
Coverage ties include vertical ties between trusses, horizontal ties along the upper and lower chords of trusses. We arrange connections along the upper chords in order to perceive part of the wind load and prevent the compressed rods of the upper chords from buckling. We arrange transverse truss trusses at the ends and in the middle of the building. We install connections along the lower belts for the perception of wind and crane loads of the longitudinal and transverse directions. A truss connection is a spatial block with adjacent truss trusses attached to it. Adjacent trusses along the upper and lower chords are connected by horizontal truss ties, and along the lattice posts - by vertical truss ties.
The lower truss belts are connected by transverse and longitudinal horizontal ties: the first ones fix vertical ties and stretch marks, thereby reducing the vibration level of the truss belts; the latter serve as supports for the upper ends of the racks of the longitudinal fachwerk and evenly distribute the load on adjacent frames. The upper chords of the trusses are connected by horizontal cross braces in the form of spacers or girders to maintain the designed position of the trusses.
Connections between columns of industrial buildings
Column ties provide lateral stability metal structure building and its spatial immutability. The connections of columns and racks are vertical metal structures and structurally represent struts or disks that form a system of longitudinal frames. Struts connect the columns in horizontal plane. Spacers are longitudinal beam elements. Inside the connections of the columns, the connections of the upper tier and the connections of the lower tier of the columns are distinguished. The connections of the upper tier are located above the crane beams, the connections of the lower tier, respectively, below the beams. Main functional purposes loads of two tiers are the ability to transfer the wind load to the end of the building from the upper tier through the transverse links of the lower tier to the crane beams. Upper and bottom ties also help to keep the structure from tipping over during installation. The connections of the lower tier also transfer loads from the longitudinal braking of cranes to the crane beams, which ensures the stability of the crane part of the columns. Basically, in the process of erecting the metal structures of the building, the connections of the lower tiers are used.
Communication systems for frames of industrial buildings
For connection structural elements the frame is metal ties. They perceive the main longitudinal and transverse loads and transfer them to the foundation. metal ties also evenly distribute loads between trusses and frame frames to maintain overall stability. Their important purpose is to counteract horizontal loads, i.e. wind loads. Column connections provide transverse stability of the metal structure of the building and its spatial immutability. Inside the connections of the columns, the connections of the upper tier and the connections of the lower tier of the columns are distinguished. The connections of the upper tier are located above the crane beams, the connections of the lower tier, respectively, below the beams. The main functional purposes of the loads of two tiers are the ability to transfer the wind load to the end of the building from the upper tier through the cross braces of the lower tier to the crane beams. Top and bottom ties also help keep the structure from tipping over during installation. The connections of the lower tier also transfer loads from the longitudinal braking of cranes to the crane beams, which ensures the stability of the crane part of the columns. Basically, in the process of erecting the metal structures of the building, the connections of the lower tiers are used. To give spatial rigidity to the structure of a building or structure, metal trusses are also connected by ties. Adjacent trusses along the upper and lower chords are connected by horizontal truss ties, and along the lattice posts - by vertical truss ties. The lower truss belts are connected by transverse and longitudinal horizontal ties: the first ones fix vertical ties and stretch marks, thereby reducing the vibration level of the truss belts; the latter serve as supports for the upper ends of the racks of the longitudinal fachwerk and evenly distribute the load on adjacent frames. Cross ties unite the upper chords of the truss into a single system and become the “closing edge”. The struts just prevent the trusses from moving, and the transverse horizontal trusses of the connection prevent the struts from moving.
Solid purlins
Solid runs are used with a truss step of not more than 6 m n, depending on the purpose, they have a different design section. Solid runs are made according to split and continuous schemes. Most often, split circuits are used because of their ability to simplify installation, however, a continuous circuit also has positive distinctive features, for example, with a continuous scheme, less steel is consumed for the runs themselves.
Runs located on a slope, taking into account the roof with a large slope, always work on bending in two planes. The stability of the purlins is achieved by fixing the roof slabs or by attaching the decking to the purlins, taking into account all the friction forces between them. It is customary to fasten the girders to the truss belts using short corners and bent elements made of sheet steel.
Lattice purlins
Rolled or cold-formed channels are used as runs, with a truss step of more than 6 m - lattice runs. Simple and most lightweight construction The lattice purlin is a bar-trussed purlin with a lattice and a lower belt made of round steel. The disadvantage of such a run is the complexity of the control of welds in the junctions of the lattice rods with the lower chord, as well as the need for careful transportation and installation.
The upper chord of lattice purlins, in case of its high rigidity from the plane of the purlin, should be calculated for the combined action of axial force and bending only in the plane of the purlin, and in the case of low rigidity of the upper chord from the plane of the purlin, it is necessary to calculate the upper chord for the combined action of axial force and bending as in the plane run, and in a plane perpendicular to it. The flexibility of the upper belt of lattice, runs should not exceed 120, and lattice elements - 150. The upper chord of this run consists of two channels, and the lattice elements - from a single bent channel. Usually, the braces are fixed to the upper chord using arc or resistance welding.
Lattice purlins are calculated as trusses with a continuous upper chord, which always works in compression with bending in one or two planes, while other elements experience longitudinal forces.
Links between columns.
The system of connections between the columns ensures during operation and installation the geometric invariability of the frame and its bearing capacity in the longitudinal direction, as well as the stability of the columns from the plane of the transverse frames.
The bonds that form HDD, are located in the middle of the building or the temperature compartment, taking into account the possibility of moving columns during thermal deformations of the longitudinal elements.
If you put connections ( hard disks) along the ends of the building, then in all longitudinal elements (crane structures, truss trusses, braces) there are large temperature forces F t
When the length of a building or a temperature block is more than 120 m, two systems of connection blocks are usually placed between the columns.
Limit dimensions between vertical links in meters
Dimensions in parentheses are given for buildings operated at design outdoor temperatures t= -40° ¸ -65 °С.
Most simple circuit cross connections, it is used with a column spacing of up to 12 m. The rational angle of inclination of the connections, therefore, when big step, but at a high height of the columns, two cross connections are installed along the height of the lower part of the column.
In the same cases, sometimes an additional decoupling of columns from the plane of the frame with spacers is designed.
Vertical connections are placed in all rows of the building. With a large step of the columns of the middle rows, and also in order not to interfere with the transfer of products from span to span, links of portal and semi-portal schemes are designed.
The vertical connections between the columns perceive the forces from the wind W 1 and W 2 acting on the end of the building and the longitudinal braking of cranes T etc.
Elements of cross and portal connections work in tension. Compressed rods, due to their high flexibility, are excluded from work and are not taken into account in the calculation. The flexibility of tensioned elements of connections located below the level of crane beams should not exceed 300 for ordinary buildings and 200 for buildings with a "special" mode of operation of cranes; for connections above crane beams - 400 and 300, respectively.
Coverage links.
Connections by roof structures (tent) or connections between trusses create a general spatial rigidity of the frame and provide: stability of compressed truss belts 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 to the columns of some loads.
Coverage connections are located:
1) in the plane of the upper chords of roof trusses - longitudinal elements between them;
2) in the plane of the lower chords of truss trusses - transverse and longitudinal truss trusses, as well as sometimes longitudinal extensions between transverse truss trusses;
3) vertical connections between roof trusses;
4) communications on lanterns.
Ties in the plane of the upper chords of trusses.
The elements of the upper chord of the truss trusses are compressed, so it is necessary to ensure their stability from the plane of the trusses.
Reinforced concrete roof slabs and girders can be considered as supports that prevent the displacement of the upper nodes from the plane of the truss, provided that they are secured from longitudinal movements with braces located in the plane of the roof. It is advisable to place such ties (transverse braced trusses) at the ends of the workshop so that they, together with transverse braced trusses along the lower chords and vertical braces between trusses, create a spatial block that ensures the rigidity of the coating.
With a longer length of the building or temperature block, intermediate cross-braced trusses are installed, the distance between which should not exceed 60 m.
To ensure the stability of the upper belt of the truss from its plane within the lantern, where there is no roof deck, special spacers are provided, in the ridge knot of the farm are required. During the installation process (before the installation of roof slabs or girders), the flexibility of the upper chord from the truss plane should be no more than 220. Therefore, if the ridge strut does not provide this condition, an additional strut is placed between it and the strut on the truss support (in the plane of the columns).
Ties in the plane of the lower truss chords
In buildings with overhead cranes, it is necessary to ensure the horizontal rigidity of the frame both across and along the building.
During the operation of overhead cranes, forces arise that cause transverse and longitudinal deformations of the shop frame.
If the transverse rigidity of the frame is insufficient, the cranes may jam during movement and normal operation is disrupted. Excessive frame oscillations create unfavourable 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 heavy and very heavy duty cranes, at any load capacity, a system of connections along the lower chords of trusses is required.
Horizontal forces F from overhead cranes act in the transverse direction on one flat frame or two or three adjacent ones.
Longitudinal braced trusses ensure the joint operation of a system of flat frames, as a result of which the transverse deformations of the frame from the action of a concentrated force are significantly reduced.
Racks of the end fachwerk transmit the wind load F W to the nodes of the transverse truss 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 - 250, for other buildings - 400. To reduce the length of the stretched part of the lower belts in some cases put stretch marks that secure the lower belt in the lateral direction.
Vertical links between farms.
These connections connect the roof 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 belts of trusses, forming together with them a rigid block.
In buildings with overhead transport, vertical connections contribute to the redistribution between trusses of the crane load applied directly to the roof structures. In these cases, as well as to the roof trusses, an electric crane is attached - beams of significant carrying capacity, vertical connections between the trusses are located in the suspension planes continuously along the entire length of the building.
The constructive scheme of connections depends mainly on the pitch of the roof trusses.
Connections on the upper belts of truss trusses
Connections on the lower belts of roof 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).
AT recent times mainly braced trusses with a triangular lattice are used (Fig. b). Here, the braces work both in 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 system of connections is designed so that the longest element is no more than 12 m, and diagonals support this element (Fig. c, d).
It is possible to ensure the fastening of longitudinal ties without a lattice of ties along the upper belt of trusses, which does not make it possible to use through runs. In this case, the rigid block includes covering elements (girders, panels), roof trusses and often located vertical ties (Fig. e). This solution is currently standard. The connection elements of the tent (covering) are calculated, as a rule, in terms of flexibility. The ultimate flexibility for the compressed elements of these links is 200, for the stretched ones - 400, (for cranes with a number of cycles of 2 × 10 6 and more - 300).
A system of structural elements that serve to support the wall fence and perceive the wind load called fachwerk.
Fachwerk is arranged for loaded walls, as well as for internal walls and partitions.
At self-supporting walls, as well as at panel walls with panel lengths equal to the column spacing, there is no need for half-timbered structures.
With a step of external columns of 12 m and wall panels 6 m long, intermediate half-timbered racks are installed.
Fachwerk, installed in the plane of the longitudinal walls of the building, is called a longitudinal fachwerk. Fachwerk, installed in the plane of the walls of the end of the building, is called end fachwerk.
The end fachwerk 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 truss truss at the level of the lower chords of the truss trusses.
In order not to prevent the deflection of roof trusses from temporary loads, the fachwerk racks are supported using leaf hinges, which are thin sheet t=(8 10 mm) 150 200 mm wide, which is easily bent in the vertical direction without preventing the truss deflection; in the horizontal direction, it transmits force. Crossbars are attached to the half-timbered racks for window openings; with a high height of the racks in the plane end wall put spacers that reduce their free length.
Walls made of bricks or concrete blocks are self-supporting, i.e. perceiving all their weight, and only the lateral load from the wind is transferred by the wall to the column or half-timbered rack.
Walls of large-panel reinforced concrete slabs are installed (hung) on the tables of columns or half-timbered racks (one table after 3-5 slabs in height). In this case, the half-timbered rack works on eccentric compression.
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