Cross vertical ties on steel covering trusses. Types of connections of frame buildings. Loads on the crane beam

Connections - important elements steel frame, which are necessary to meet the following requirements:

– ensuring the immutability of the spatial system of the frame and the stability of its compressed elements;

– perception and transmission of some loads to the foundations (wind, horizontal from cranes);

– provision collaboration transverse frames under local loads (for example, crane loads);

– creating the frame rigidity necessary to ensure normal conditions operation;

– providing conditions for high-quality and convenient installation.

Connections are divided into connections between columns and connections between trusses (cover connections).

Connections between columns.

The system of connections between columns (9.8) provides during operation and installation:

– geometric immutability of the frame;

– load-bearing capacity of the frame and its rigidity in the longitudinal direction;

– perception of longitudinal loads from the wind at the end of the building and braking of the crane bridge;

– stability of columns from the plane of transverse frames.

The lattice is designed as a cross (Fig. 9.13, a), the elements of which are assumed to be flexible [] = 220 and work in tension in any direction of forces transmitted to the disk (the compressed brace loses stability) and triangular (Fig. 9.13, b), the elements of which work in tension and compression. The lattice design is selected so that its elements can be conveniently attached to the columns (the angles between the vertical and the lattice elements are close to 45°). For large column spacing, it is advisable to install a disk in the form of a double-hinged lattice frame in the lower part of the column, and to use a rafter truss in the upper part (Fig. 9.13, c). The spacers and lattice at low heights of the column section (for example, in the upper part) are located in one plane, and at high heights (the lower part of the column) - in two planes.

Rice. 9.13. Structural diagrams hard drives connections between columns:

a - when ensuring stability of the lower part of the columns from the plane of the frame; b - if necessary, install intermediate spacers; c - if it is necessary to use a crane gauge.

Rice. 9.14. Schemes of temperature movements and forces:

a - when vertical connections are located

in the middle of the frame; b - the same, at the ends of the frame

When placing hard drives (connection blocks) along the building, it is necessary to take into account the possibility of columns moving due to thermal deformations of the longitudinal elements (Fig. 9.14, a). If you place disks at the ends of the building (Fig. 9.14, b), then significant thermal forces arise in all longitudinal elements (crane structures, rafter trusses, brace struts) and in the connections.

Therefore, when the length of the building (temperature block) is short, a vertical connection is installed in one panel (Fig. 9.15, a). If the building is long, vertical connections are installed in two panels (Fig. 9.15, b), and the distance between their axes should be such that the forces F t are small. The maximum distances between disks depend on possible temperature changes and are established by standards (Table 9.3).

At the ends of the building, the outer columns are connected to each other by flexible top connections(see Fig. 9.15, a). Due to the relatively low rigidity of the crane part of the column, the location of the upper ties in the end panels has little effect on temperature stresses.

Vertical connections between columns are installed along all rows of columns of the building; they should be located between the same axes.

Rice. 9.15. Location of connections between columns in buildings:

a - short (or temperature compartments); b - long; 1 - columns; 2 - spacers; 3 - expansion joint axis; 4- crane beams; 5 - communication block; 6- temperature block; 7 - bottom of trusses; 8 - bottom of the shoe

Table9.3. Limit dimensions between vertical connections, m

When designing connections along the middle rows of columns in the crane section, it should be borne in mind that quite often, according to technology conditions, it is necessary to have free space between the columns. In these cases, portal connections are constructed (see Fig. 11.5, c).

The connections installed within the height of the crossbars in the connection and end blocks are designed in the form of independent trusses (mounting element); spacers are installed in other places.

Longitudinal tie elements at the points of attachment to the columns ensure that these points are not displaced from the plane of the transverse frame. These points in the design diagram of the column can be taken by hinged supports. If the lower part of the column is high, it may be advisable to install an additional spacer, which secures the lower part of the column in the middle of its height and reduces the estimated length of the column.

Rice. 9.16. Work of connections between columns under the influence of: a - wind load on the end of the building; b - overhead cranes.

Load Transfer. At point A (Fig. 9.16, a), the flexible link element 1 cannot perceive compressive force, therefore F w is transmitted by a shorter and fairly rigid spacer 2 to point B. Here the force along element 3 is transmitted to point B. At this point the force is perceived by the crane beams 4, transmitting force F w to the connection block to point G. Connections work similarly on the forces of longitudinal impacts of cranes F (Fig. 9.16, b).

Tie elements are made from angles, channels, rectangular and round pipes. With a large length of tie elements that perceive small forces, they are calculated according to the maximum flexibility, which for compressed tie elements below the crane beam is equal to 210 - 60 ( is the ratio of the actual force in the tie element to its load-bearing capacity), above - 200; for stretched ones, these values are 200 and 300, respectively.

Coverage links (9.9).

Horizontal connections are located in the planes of the lower and upper chords of the trusses and the upper chord of the lantern. Horizontal connections consist of transverse and longitudinal ones (Fig. 9.17 and 9.18).

Rice. 9.17. Connections between farms: a - along the upper belts of farms; b - along the lower chords of trusses; c - vertical; / - spacer in the ridge; 2 - transverse braced trusses

Rice. 9.18. Connections between lanterns

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. The ribs of 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 ties.

It is necessary to pay special attention to the tying of truss knots within the lantern, where there is no roofing. Here, to secure the nodes of the upper chord of the trusses from their plane, spacers are provided, and such spacers in the ridge node of the truss are required (Fig. 9.19, b). Spacers are attached to the end braces in the plane of the upper chords of the trusses.

During the installation process (before installing the covering slabs or purlins), the flexibility of the upper chord from the plane of the truss should not be more than 220. If the ridge spacer does not provide this condition, an additional spacer is placed between it and the spacer in the plane of the columns.

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 when moving, and their normal operation is 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 high height ( N 0 > 18 m), in buildings with overhead cranes with a lifting capacity ( Q≥ 10 t, with cranes of heavy and very heavy operating modes for any lifting capacity, a system of longitudinal connections along the lower chords of the trusses is required.

Rice. 9.19. Coverage link operation:

a - diagram of the operation of horizontal connections during action external loads; b and c" - the same, with conditional forces from loss of stability of the truss chords; / - connections along the lower chords of the trusses; 2 - the same, along the upper ones; 3 - spacer of the connections; 4 - stretching of the connections; 5 - form of loss of stability or vibrations in the absence of a spacer (stretch); 6 - the same, in the presence of a spacer.

Horizontal forces from overhead cranes act transversely on one flat frame and two or three adjacent ones. Longitudinal connections ensure the joint operation of the system of flat frames, as a result of which the transverse deformations of the frame from the action of concentrated force are significantly reduced (Fig. 9.19, a).

The rigidity of these connections must be sufficient to involve adjacent frames in the work, and their width is assigned equal to the length of the first panel of the lower chord of the truss. Connections are usually installed with bolts. Welding connections increases their rigidity several times.

The panels of the lower chord of the trusses adjacent to the supports, especially when the girder is rigidly connected to the column, can be compressed; in this case, the longitudinal connections ensure the stability of the lower chord from the plane of the trusses. Transverse braces secure the longitudinal ones, and at the ends of the building they are also necessary to absorb the wind load directed at the end of the building.

The half-timbered posts transmit the wind load F w to the nodes of the transverse horizontal end truss, the chords of which are the lower chords of the end and adjacent trusses (see Fig. 9.19, a). The support reactions of the end truss are perceived by vertical connections between the columns and are transmitted to the foundation (see Fig. 9.19). In the plane of the lower chords, intermediate transverse braces are also installed, located in the same panels as the transverse braces along the upper chords of the trusses.

To avoid vibration of the lower chord of the trusses due to the dynamic impact of overhead cranes, it is necessary to limit the flexibility of the stretched part of the lower chord from the plane of the frame. To reduce the free length of the stretched part of the lower belt, in some cases it is necessary to provide stretchers that secure the lower belt in the lateral direction. These braces perceive the conditional lateral force Q fic (Fig. 9.19, c).

In long buildings consisting of several temperature blocks, transverse braced trusses along the upper and lower chords are placed at each expansion joint (as at the ends), keeping in mind that each temperature block represents a complete spatial complex.

Vertical connections between the trusses they are installed in the same axes in which the horizontal transverse links are placed (see Fig. 9.20, c). Vertical connections are placed in the plane of the truss trusses in the span and on supports (when supporting the trusses at the level of the lower chord). In the span, one or two vertical connections are installed along the width of the span (every 12-15 m). Vertical braces impart immutability to a spatial block consisting of two trusses and horizontal cross braces along the upper and lower chords of the trusses. Rafter trusses have insignificant lateral rigidity, so during installation they are secured to a rigid spatial block with spacers.

In the absence of horizontal cross braces along the upper chords, to ensure the rigidity of the spatial block and secure the upper chords out of the plane, vertical braces are installed every 6 m (Fig. 9.20, e).

Rice. 9.20. Schemes of communication systems for coverage:

a - cross braces with a 6-meter frame spacing; b - connections with a triangular lattice; c and d - the same, with a 12-meter frame pitch; d - combination of horizontal braces along the lower chords of trusses with vertical braces; I, II - connections along the upper and lower chords of the trusses, respectively

The cross-sections of the bracing elements depend on their structural design and the pitch of the trusses. For horizontal connections with a truss pitch of 6 m, a cross or triangular lattice is used (Fig. 9.20, a, b). The braces of the cross lattice work only in tension, and the racks work in compression. Therefore, racks are usually designed from two corners of a cross section, and braces - from single corners. Elements of a triangular lattice can be either compressed or stretched, so they are usually designed from bent profiles. Triangular ties are somewhat heavier than cross ties, but their installation is simpler.

With a truss pitch of 12 m, the diagonal bracing elements, even in a cross lattice, turn out to be very heavy. Therefore, the bracing system is designed so that the longest element is no more than 12 m; these elements support the diagonals (Fig. 9.20, c). In Fig. 9.20, d shows a diagram of connections, where the diagonal elements fit into a square measuring 6 m and rest on longitudinal elements 12 m long, serving as belts of braced trusses. These elements have to be made of a composite section or from bent profiles.

Vertical connections between trusses and lanterns are best done in the form of separate transportable trusses, which is possible if their height is less than 3900 mm. Various schemes of vertical connections are shown in Fig. 9.20, e.

In Fig. Figure 9.19 shows the signs of the forces that arise in the elements of the pavement connections at a certain direction of the wind load, local horizontal forces and conditional shear forces. Many link elements can be compressed or stretched. In this case, their cross-section is selected according to the worst case - flexibility for compressed bracing elements.

Spacers in the ridge of the upper chord of the trusses (element 3 in Fig. 9.19, b) ensure the stability of the upper chord from the plane of the trusses both during operation and during installation. In the latter case, they are attached to only one cross-section; their cross-section is selected based on compression.

The metal frame, as many people know, is the main structure of frame-panel buildings. It includes a wide variety of structural elements: beams, trusses, half-timbers, spacers and others. In this review we will look at such structural elements as connections.
Metal connections are intended for overall sustainability metal frame in the longitudinal and transverse directions, so their value is quite large. They counteract the main horizontal load on the frame coming from the wind. The greatest effect here is noticeable when using anti-corrosion materials. What factors and materials need to be taken into account? Siding series "Mitten" and all types of siding from the manufacturer. Fiberglass septic tanks are also important for sewerage in the residential sector or country house, where repairs and improvement are provided. Thanks to them, positive results can be achieved. And, of course, foundation work preceded by groundwork is important. Which ones should I highlight? Drilling water wells, water treatment and water supply all year round - all this is relevant for an industrial building. However, any real estate objects are interesting. The fashion for real estate allows you to buy an apartment in a new building under convenient conditions. What is the reason for this? Huge selection. New buildings in Moscow from developers. No commission.
There are three types of connections in a metal frame: cross, corner and portal. Today, such products are easy to purchase not only from industrial manufacturing enterprises; equipment of the Eurostandard brand stands out especially. These products are also available on the Internet. According to experts, the cost of creating a construction online store is low, so hardware It's very profitable to buy there. An energy audit will help to estimate the cost, regardless of the calculations.
Cross ties represent the classic and simplest option, when the elements of the ties intersect and are attached to each other in the middle of the length. Such technologies, as professionals note, are often used when installing utility rooms and structures. What can be noted? Cabins and containers with dry closets. Toilet cabins, according to experts, have a wide range. Currently they are very popular. As practice shows, it is only necessary here. Durable installation metal doors with the existing modernization in 4 hours it will be an excellent technological solution for these structures. This is also relevant for the facade. Hurry up to buy façade thermal panels with clinker and lightweight tiles at a special price using a rational approach! Order a car for this. Forward! A car loan is almost like buying a car. Legal advice is also appropriate here.
Corner braces are usually used for small spans and are arranged in a row of several parts. They are smaller in height than cross-links. Of course, it is recommended to use here insulating materials. Today this is not a problem. Just look at the advertising applications of some companies that require you to buy “technological” insulation at favorable conditions- only with best filling! And this, according to experts, the right approach to construction.
Portal connections are the largest in terms of working area. They have a U-shaped appearance and find their application in those spans metal frame where window or door openings or furniture elements are provided. Find out all the secrets of furniture makers: custom-made kitchens with furniture according to individual orders. There is also excellent renovation of one-room and complex apartments to order.
If we talk about the ones that are used to make ties, then most often it is a corner or bent square or rectangular profile, less often - a channel or an I-beam.
Of the existing frames for connections, the most applicable bolted connections, as technologically and structurally the most efficient and convenient for installation.
In accordance with the rules of the metal frame, the connections are located both in the longitudinal direction of the structure being designed, and in the transverse direction - along its ends. In this case we're talking about about vertical metal bonds. They are used in many systems, even in everyday life. What can you take as an example? Electrical system steam generators and air conditioners - this is a unique combination. This is a very popular modern technological device.
Sometimes the structural design of a metal frame requires the use of horizontal connections. For the most part, this occurs on a large scale, with long spans and significant heights for typical columns. Horizontal connections here are usually of the cross type and are located in several modules in a row in longitudinal spans between trusses, which are always designed for large-sized metal frames.
As for the designations of metal connections in a metal frame, a thick dash-dotted line is usually used for them.

The metal frame of an industrial building consists of a number of “flat” elements that are rigid and well-bearing loads in their plane, but flexible in the perpendicular direction (frames, sub-rafters and intermediate trusses, etc.). The main purpose of the connections is to combine flat elements into a spatial system capable of absorbing loads acting on the building in any direction.

Secondly, the connections serve to ensure the stability of the compressed and compressed-bent rods of the upper chords of trusses, columns, etc. The danger of loss of stability of such elements is explained by the fact that the metal frame rods have long lengths and relatively small compact transverse dimensions. Ties relax compressed elements at intermediate points, reducing the design lengths of elements in the direction of these restraints.

There are the following main types of connections used in the metal frame of an industrial building:

1) transverse connections between the upper chords of the trusses (through crossbars of the frames will be called “trusses” in the future) (Fig. 1) 2) vertical connections between the trusses (Fig. 9); 3) longitudinal and transverse connections located in the plane of the lower chords of the trusses (Fig. II); 4) vertical connections between columns (Fig. 22). Let's consider the layout, purpose and design solutions of communication nodes using examples of buildings with different coatings.

I. CROSS CONNECTIONS BETWEEN THE UPPER CHORDS OF TRUSSES

1.1. The upper chord of the truss, like any compressed rod, can lose stability if the force in it reaches a critical value. In this case, loss of stability will occur in one of two planes:

Fig.1. Transverse connections between the upper chords of the trusses, 2-2 - vertical connections a) in the plane of the truss - a rod that has lost stability will remain in the plane of the truss. This means that when looking at the truss from above, the loss of stability will not be noticeable. As can be seen from Fig. 2, the calculated length when checking the stability of the upper chord “and plane” of the truss corresponds to the distance between the nodes, that is, the length of one panel;

Fig.2. Estimated length of the upper chord in the plane of the truss, (dotted line)

b) the loss of stability of the upper chord with its exit from the plane of the truss is shown only in plan. Let's assume that no connections have been made. Then loss of stability will occur according to the diagram shown in Fig. 3. The purlins, which are usually hingedly attached to the upper chord of the truss (with the help of bolts), by themselves, without connections, will not prevent the loss of stability of the trusses, since after loss of stability the upper chords of the trusses will bulge, and the purlins will freely move to a new position. At the same time, the distance between the trusses (the span of the purlins) will remain the same.

A different picture of stability will be observed if connections are made. The connections can be cross-shaped - with two diagonals (Fig. 3.6) and lightweight, triangular (Fig. 3, c), i.e. with one diagonal. Compressed diagonals, obviously, are turned off from work, having lost stability, and stretched ones will prevent the distortion of rectangles and will prevent them from turning into parallelograms. Consequently, at the points of attachment of the diagonals, the truss belt will retain its original position and its calculated length “from the plane” will be equal to the section “L-B” (Fig. 3, c), i.e. two panels. The upper chords of all trusses connected to these points using purlins (or struts along the lanterns) will have the same design lengths as the chords of two trusses directly secured with ties, i.e. sections A"-B", A"-B"" have estimated lengths equal to two panels.

Fig.3. Loss of stability of the upper chords of the trusses; a) in a coating without connections; b) diagram of tension and release of bracing braces; c) ensuring the stability of the belts using rod connections

Let us pay attention to the error that can be made when determining the estimated length of the upper chord from the plane of the truss. In Fig. 3c, the run intersects the diagonal of the bonds at point “f”. It seems that the purlin is attached to the diagonal of the braces, and it would seem that the calculated length of the upper chord from the plane of the truss can be taken equal to the panel. However, this is not true: the purlins and connections are located in different levels, there is a gap between them “f” (Fig. 7)

1.2. In buildings with a lantern (Fig. 4), the upper chord is not secured from the plane of the truss to large plot, because There are no purlins under the lantern. If we assume that the lantern wall enclosure structures together with the purlin fix point “B”, then the estimated length of the upper chord is from the “B~B” plane. The introduction of a spacer in the middle of the lantern span reduces the estimated length from the plane of the truss (Fig. 4b) to three panels.

Fig.4. Estimated lengths of the upper chord under the lantern:
a) without spacers - 6 panels;
b) with one spacer - 3 panels;
c) with a truss pitch of 12 m, an intermediate PP tie belt is introduced

The upper belt of vertical braces is used as a spacer (section 2), but paired corners or other profiles specially designed for this purpose can be used,

1.3. Recently, in order to save metal, it has been customary to assign the functions of connections along the upper chords to the roofing deck, which, when securely attached to the trusses, can ensure the stability of the upper chords from the plane of the trusses.

Thus, in non-girder coatings with reinforced concrete flooring, the stability of the upper chords from the plane of the trusses is ensured by welding the embedded parts of the flooring to the upper chords. In this case, the estimated length of the upper chord is from. the plane of the truss can be taken equal to the length of one truss panel. When welding the decking to the truss chords, instructions must be given in a note on the drawing.

During the construction of the building, these attachments of slabs to chords must be controlled. In this case, it is necessary to draw up an act for hidden work. Profiled flooring can also serve as ties along the upper chords if it is attached using dowels to the purlins.

The best constructive solution when using profiled flooring as ties, it will be in such a way that the purlins are attached to the truss so that the top flange of the purlin is at the same level as the top flange of the truss chord. In this case, the flooring is targeted with dowels on its four sides - to the purlins and upper chords of the trusses. For the convenience of attaching the purlins to the trusses, in this case, you can use covering trusses not with a triangular lattice, but with downward braces (Fig. 5).

Fig.5. Using profiled flooring as ties along the top chord:
a) roof truss with downward braces;
b) an option for solving the girder support unit at the same level with the upper chord of the truss

With the economic advantages of replacing the ties with flooring attached to the belts, the coverings are deprived of one important function performed by the ties. The connections along the upper chords, in addition to ensuring the stability of the trusses, also secure the correct relative position of the trusses during installation. Therefore, when installing a coating without ties, it is recommended to provide for the use of temporary (removable) inventory ties, i.e. installation conductors.

If there are lanterns in coverings where the flooring serves as ties along the upper chord, under the lantern to ensure the stability of the belt, ties are arranged in the form of diagonals with a truss pitch of 6 m or in the form of incomplete diagonals with a truss pitch of 12 m (Fig. 6). In this case, the calculated length of the upper chord of the trusses when checking out-of-plane stability is assumed to be equal to two panels.

Fig.6. Ensuring the stability of the upper chords of trusses under lanterns in coverings where the function of ties is performed; flooring t a) truss pitch b m, b) truss pitch 12 m

1.4. In coverings with a truss pitch of 12 m and with purlins with a span of 12 m, the braced truss is assumed to be 6 m wide. In this case, an additional intermediate belt is introduced from the corresponding profiles (Fig. 4, c) and the ties are constructed in the same way as if the truss spacing were 6 m.

1.5. The distance along the length of the building between the rod ties along the upper chord of the trusses should not exceed 144 m. Therefore, in long buildings, ties are placed not only in the outer panels of the frame block but also in the middle or thirds of the length of the block (Fig. I).

These requirements are explained by the fact that the sustainability of farms located far away o,t connections, cannot always be reliably ensured, because the purlins or struts that attach the trusses to the tie blocks allow a certain displacement in the nodes due to the difference in the diameters of the bolts and holes. With an increase in the number of nodes, i.e. With the distance of connections, this mixability is summed up and increases, which reduces the reliability of ensuring the stability of farms located far from the connections.

The designs of some tie nodes, made of angle and bent-welded profiles, and their attachment to the trusses are shown in Fig. 7, 8.

So, the connections located in the plane of the upper chords of the trusses have the following main purpose: when loading the coating, they prevent the loss of stability of these chords from the plane of the trusses, that is, they reduce the design length of the upper chords when checking their stability from the plane of the trusses.

2. VERTICAL CONNECTIONS BETWEEN FARMS

These connections are also called installation connections, since their main purpose is to hold the trusses placed on supports in the design position, to prevent single trusses from overturning during installation from wind and random influences, because the center of gravity of the truss is above the level of the supports (Fig. 9, a).

Vertical connections in the form of a chain of struts and trusses are placed along the length of the building between the racks of the trusses. To save metal, braced trusses are connected to each other by upper and lower struts (Fig. 10). Thus, the vertical brace trusses are disks, and the spacer rods attached to them provide intermediate trusses or frame crossbars against tipping over (Fig. 9b). The lattice of braced trusses, as a rule, can be arbitrary (Fig. 9c) and is made from single corners or from rectangular bent-welded pipes. In coverings with a truss pitch of 12 m, with trussed purlins or with a deck reinforced with trusses, the upper chord of the vertical brace truss can have the form shown in Fig. 9d.

Vertical connections along the width of the span are located on supports (between the columns) and in the span between the truss posts at least every 15 m, i.e. with a building span of 36 m, they will be located in the planes of two racks.

Fig.7. Attaching ties to the upper chords of trusses

Fig.8. Covering and bracing units with a truss pitch of 12 m (see Fig. 6);
a) Attaching connections made from closed profiles to trusses with belts made of wide-flange I-beams
b) Node B

Fig.9. Vertical connections between farms:
a) position center of gravity,
b) trusses-discs and spacers,
c) diagrams of truss lattice,
d) connections in coverings with a truss pitch of 12 m and with trussed girders

Trusses - disks of vertical connections are placed in increments of 30-36 m along the length of the building. The uprights of the corner trusses, to which the ties are attached in the upper and lower nodes, are assumed to have a cross section (Fig. 10).

The connections can also be attached to vertical gussets specially designed for this purpose. As part of the block during large-block installation, vertical connections are necessary elements, ensuring the immutability of the block.

Fig. 10. The attachment point for the upper chord of the vertical brace truss to the truss truss post. The bottom node is performed similarly

LONGITUDINAL HORIZONTAL CONNECTIONS ALONG THE LOWER BEDS OF THE GIRLS

The contour of the connections located in the plane of the lower through crossbars can be divided into longitudinal and transverse connections (Fig. 11). The purpose of longitudinal connections is as follows:

3.1. Longitudinal connections perceive transverse horizontal crane impacts, i.e. they perceive the eccentric application of the crane’s vertical pressure on the column, causing horizontal displacement of the frame, as well as the transverse braking of the crane applied to one frame (Fig. 12a) and transmits these impacts to adjacent frames that are less loaded (Fig. 12b). This ensures the spatiality of the frame when operating under local loads that cause horizontal displacements of the frame crossbar.

Fig. 11. Connections along the lower chords of frame crossbars

Fig. 12. Scheme taken up by transverse horizontal loads by longitudinal connections along the lower chords:
a) displacement of frames from the vertical eccentric application of the crane load and from braking;
b) transfer of lateral loads on connections

3.2. Note that the lateral load from the wind is transmitted equally to all frames, causing them to mix equally. In this case, there are no transverse forces between the frames, and therefore, in frames with a frame pitch of 6 m, the longitudinal connections do not absorb wind loads,

When the column spacing is 12 m or more in frames with half-timbered (wall frame) posts, the longitudinal braces work against this load; They are the upper horizontal supports of the half-timbered posts. Thus, in this case, the longitudinal connections transmit forces from wind loads from the half-timbered posts to adjacent frames (Fig. 13) and the connections are loaded with forces from the wind load along the length of the frame step.

Fig. 13. Transfer of wind load from half-timbered posts to longitudinal braces

3.3. In the outermost panels of the crossbar, due to the fact that the rigidly clamped crossbar on the support experiences bending moments of the opposite sign with respect to the sign of the moment in the span, the lower chord is compressed (Fig. 14).

Fig. 14. Compression in the lower chord of the crossbar near the supports

It is possible to secure the lower chord against loss of stability from the plane of the crossbar here only with the help of longitudinal connections (point “f” in Fig. 14). The stability of the lower chord in the plane of the crossbar is ensured either by the development of the moment of inertia of the section of the belt (in this panel it can be taken from two unequal angles made up of large flanges), or by the introduction of an additional suspension.

3.4. In multi-span buildings with heavy-duty cranes (7K, 8K), longitudinal connections in the form of horizontal trusses are placed from each other at a distance of no more than two spans (Fig. 15)

Fig. 15. Connections along the lower chords of crossbars in a multi-span frame with heavy-duty cranes (7K, 8K)

In multi-span buildings with medium-duty cranes with a lifting capacity of up to 50 tons, with spans of no more than 36 m and with a height of up to 25 m, as well as with a frame pitch of 6 m, it is allowed not to make longitudinal connections along the lower chord. However, spacers and ties that ensure the stability of the lower chords from the plane of the trusses must be placed in each span (Fig. 16).

Fig. 16. Connections along the lower chords of the B frame with medium-duty cranes (4K - 6K)

4. CROSS BRACES IN THE PLANE OF THE LOWER JOINTS OF THE GIRLS

4.1. These connections serve to transfer forces from wind loads directed to the end of the building, from the end frame racks to the vertical connections between the columns (Fig. 17) (pressure transfer is shown by arrows).

Fig. 17. Scheme of transmission of wind loads from the end of the building in connection

4.2. Together with longitudinal connections, they form a closed loop, increasing the overall rigidity of the building frame.

Transverse braces, as a rule, are placed under the braces along the upper chords, creating with them spatial transverse blocks, to which intermediate trusses (crossbars) are attached using purlins, vertical braces and longitudinal braces.

Figures 18, 19 show the attachment points of horizontal ties made from angles and rectangular bent-welded pipes to the truss chords. It should be noted that in frames with heavy duty operation of 7K, 8K cranes and with large crane loads, the connections are attached to the trusses by welding (i.e. the bolt assemblies must be welded) or using high-strength bolts.

Fig. 18. Designs of corner ties along the lower chords

5. VERTICAL CONNECTIONS BETWEEN COLUMNS

Distinguish upper tier vertical connections between columns (ties located above the crane beams) and the lower one below the beams (Fig. 20).

Fig. 19. Tie unit along the lower chord made of rectangular bent-welded profiles

Fig.20. Scheme of vertical connections between columns

5.1. The upper tier connections have the following purpose:
a) the forces from the wind directed at the end of the building are transmitted to the connections of the upper tier from the end transverse connections located in the plane of the lower chords, and then, along the stretched struts, these forces are transmitted to the crane beams,"
b) the connections of the upper tier ensure the stability of the columns “out of the plane” of the frames. Thus, the estimated length of the over-crane part of the column (Fig. 20, dotted line) from the plane of the frame is equal to the height of this part of the column;
c) together with the lower tier of ties during installation, they keep the columns secured with anchors from tipping over.

5.2. Vertical connections of the lower tier
The lower tier connections are assigned the following functions:
a) transmit wind forces from the connections of the upper tier and from the longitudinal braking of the cranes (Fig. 20);
b) ensure the stability of the crane part of the colony from the plane of the frame;

c) serve as mounting connections when installing columns. In buildings of great height, the connections of the lower tier have an additional spacer between the columns - (Fig. 21,

a). Its purpose is to reduce the estimated length of the crane part of the column from the plane of the frame. This layout technique is resorted to in the case when, when calculating the stability of a column “from the plane,” it does not give satisfactory results due to the high flexibility of the column (from the plane of the frame.).

Schemes of vertical connections can be different depending on the pitch of the columns, the need to use an opening between the columns, etc. (Fig. 21b).

Fig.21. Schemes of vertical connections of the lower tier:
a) additional spacer to reduce the estimated length of the column from the plane of the frame;
b) options for connections between columns

You should not attach the ties of the lower tier to the crane beams in the span, since when the crane moves, compression of the braces of the ties may occur, and, consequently, their shutdown. The upper tier braces can be attached to the brake beams with bolts with oval holes in the vertical direction.

Fig.22. Designs of vertical connections between columns with a column spacing of 6 m

Rice. 23. Vertical connections between columns with a column spacing of 12 m: C - oval holes in node B, allowing deflections of the crane beam without loading the connections of the upper tier; t - brake beam

In the vertical plane, the upper tier of ties is usually located along the axis of the crane part of the column, and the lower ties should be double and should be located in the planes of both the outer and internal branches of the crane part of the column (Fig. 22). If there is half-timbering, then the connections are installed in the plane of the half-timbering and are connected to the half-timbering post in the middle node. Along the length of the building, the connections of the lower tier are placed in the middle of the temperature block (Fig. 22), but in no case at the ends. Placing the connections in the middle of the building ensures free deformation of the longitudinal elements during temperature fluctuations (lengthening or shortening of crane beams, longitudinal connections, etc. .).

Fig.24. Middle node of vertical connections (see Fig. 23):
G - fastening of the connections and the half-timbered post f on installation welding, D - on high-strength bolts, Q - stiffeners, 4-4 - design cross-section of the gusset. Bolts are calculated for axial force in the diagonal of the connections and moment from eccentricity “a”

6. CALCULATION OF CONNECTIONS

In most types of connections, it is difficult to accurately determine the amount of effort that will be perceived by them. Therefore, cross-sections of tie elements are, as a rule, selected according to maximum flexibility. For elements that are known in advance to be subject to compression, it is recommended to take extreme flexibility 200.

Using known forces, vertical connections between columns are calculated, as well as transverse connections along the lower chord of the crossbar and longitudinal horizontal connections (if the spatial work of the frame is taken into account).

SNiP II-23-81*. Steel structures, - M., Stroyizdat, 1988, - 96 p.
Belenya E.I. and others. Metal structures. - M., Stroyizdat, 1989. - P.272-279.
SNiP 2.01.07.-85. Loads and impacts. - M., Stroyizdat, 1989.
Central Research Institute Steelconstruction project named after. Melnikova, Typical building construction, products and components. Series 2.440-2, Structural units of industrial buildings of industrial enterprises: Issue 4. Units of brake structures and vertical connections. KM drawings. Moscow, 1989. 49 p.
Benefit on the design of steel structures (to SNiP 23-81*) - M., Central Institute standard design, 1989 -148p.

Ties are important elements of a steel frame that are necessary for:

1. ensuring the immutability of the spatial system of the frame and the stability of its compressed elements.

2.perception and transmission of some loads to the foundations (wind, horizontal from cranes).

3. ensuring the joint operation of transverse frames under local loads (for example, crane loads).

4. creating the rigidity of the frame necessary to ensure normal operating conditions.

The connections are divided into connections between columns and connections between trusses (tent connections).

To perform these functions, you need at least one vertical hard drive along the length of the temperature block and a system of longitudinal elements attaching columns that are not part of the hard drive to the latter. The hard disks include two columns, a crane beam, horizontal struts and a lattice, which ensures geometric immutability when all elements of the disk are hinged. The lattice is most often designed as a cross lattice, the elements of which work in tension in any direction of forces transmitted to the disk, and triangular, the elements of which work in tension and compression. The lattice design is chosen so that its elements can be conveniently attached to the columns (the angles between the vertical and the lattice elements are close to 45°). For large column spacing, it is advisable to construct a disk in the form of a double-hinged lattice frame in the lower part of the column, and to use a rafter truss in the upper part. The spacers and lattice at low heights of the column sections are located in one plane, and at high heights - in two planes. Torques are transmitted to the tie disks, and therefore, when vertical bonds are located in two planes, they are connected by horizontal lattice connections.

When placing hard drives along the building, it is necessary to take into account the possibility of columns moving due to thermal deformations of the longitudinal elements (Fig. 11.6, a). If you place disks at the ends of the building (Fig. 11.6, b), then excessive thermal forces arise in all longitudinal elements (crane structures, rafter trusses, brace braces).

Therefore, when the length of the building (temperature block) is short, a vertical connection is installed in one panel (Figure 11.7, a). With a large building (or block) length, inelastic displacements at the ends of the columns increase due to the compliance of the fastenings of the longitudinal elements to the columns. The distance from the end to the disk is limited in order to secure the columns located close to the end from loss of stability. Under these conditions, vertical connections are placed in two panels (Figure 11.7, b), and the distance between the axes should be such that the force is not very large.

At the ends of the building, the outer columns are sometimes connected to each other by flexible upper connections (Fig. 11.7, a). The upper end connections are also made in the form of crosses (Figure 11.7, b).

Upper vertical braces should be placed not only in the end panels of the building, but also in the panels adjacent to the expansion joints, as this increases the longitudinal rigidity of the upper part of the frame; In addition, during the construction of a workshop, each temperature block can for some time constitute an independent structural complex.

Vertical connections between columns are installed along all rows of columns of the building; they should be located between the same axes.

The connections installed within the height of the crossbars in the connection block and end steps are designed in the form of independent trusses; spacers are installed in other places.

Longitudinal tie elements at the points of attachment to the columns ensure that these points are not displaced from the plane of the transverse frame (Figure 11.8, a). These points in the design diagram of the column (Figure 11.8, b) can be accepted by hinged supports. If the height of the lower part of the column is large, it may be advisable to install an additional spacer (Fig. 11.8, c), which secures the lower part of the column in the middle of its height and reduces the estimated length of the column (Fig. 11.8, d).

For large lengths of connection elements, which absorb small forces, are calculated according to their maximum flexibility.

Coverage connections.

The connections between the trusses, creating the overall spatial rigidity of the frame, ensure: the stability of the compressed elements of the crossbar from the plane of the trusses; redistribution of local loads applied to one of the frames; ease of installation: specified frame geometry; perception and transmission of some loads to the columns.

The coating connection system consists of horizontal and vertical connections. Horizontal connections are located in the planes of the lower and upper chords of the trusses and the upper chord of the lantern. Horizontal connections consist of transverse and longitudinal (Fig. 11.10, 11.11)

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.

To secure the slabs and girders against longitudinal displacements, transverse connections are arranged along the upper chords of the trusses, which are advisable to be located at the ends of the workshop so that they ensure spatial rigidity of the coating. If the building or temperature block is long (more than 144 m), additional transverse braced trusses are installed. This reduces the lateral movements of the truss chords resulting from the compliance of the ties.

Special attention pay attention to tying the knots of the trusses within the lantern, where there is no roofing. Here, to unfasten the nodes of the upper chord of the trusses from their plane, spacers are provided, and such spacers are required in the ridge node of the truss. Spacers are attached to the end braces in the plane of the upper chords of the trusses.

To reduce the free length of the stretched part of the lower chord, in some cases it is necessary to provide braces that secure the lower chord in the lateral direction. These braces absorb a conditional lateral force Q.

In long buildings consisting of several temperature blocks, transverse braced trusses along the upper and lower chords are placed at each expansion joint, keeping in mind that each temperature block is a complete spatial frame. Rafter trusses have insignificant lateral rigidity, so it is necessary to arrange vertical connections between the trusses located in the plane vertical racks trusses (Fig. 11.10, c).

When resting the supporting lower assembly of the rafters on the head of the column from above, the vertical connections must also be placed along the supporting posts of the trusses.

In multi-span workshops, connections along the upper chords of trusses and vertical ones are installed in all spans, and horizontal ones along the lower chords - along the contour of the building and some middle rows of columns through 60-90 m along the width of the building (Fig. 11.13). In buildings with differences in height, longitudinal braced trusses are placed along these differences.

The structural diagram of the connections depends mainly on the pitch of the trusses. For horizontal connections at a truss pitch of 6 m, a cross lattice is usually used, the braces of which work only in tension (Fig. 11.14, a), and trusses with a triangular lattice can also be used (Fig. 11.14, b) - here the braces work in both compression and stretching With a pitch of 12 m, the diagonal elements of the ties, even those working only in tension, are too heavy, so the system of ties is designed so that the longest element is no more than 12 m, and these elements support the diagonals.

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. To perform these functions, at least one vertical hard drive is required along the length of the temperature block and a system of longitudinal elements attaching columns that are not part of the hard drive to the latter. The hard disks include two columns, a crane beam, horizontal struts and a lattice, which ensures geometric immutability when all elements of the disk are hinged. The lattice is often designed as cross (its elements work in tension in any direction of forces) and triangular (elements work in tension, compression). For large column spacing, it is advisable to construct a disk in the form of a double-hinged lattice frame in the lower part of the column, and a rafter truss in the upper part. At low heights, the cross-sections of the columns are located in one plane, and at high heights - in two planes. Torques are transmitted to the tie disks, and therefore, when vertical bonds are located in two planes, they are connected by horizontal lattice connections. When placing hard drives (connection blocks) along the building, it is necessary to take into account the possibility of columns moving due to thermal deformations of the longitudinal elements. If you place disks at the ends of the building, significant temperature forces arise in all longitudinal elements (crane structures, truss trusses and bracing struts). Therefore, with a short building length, a vertical connection is installed in one panel. With a large building length, inelastic movements for columns at the ends increase due to the compliance of the attachments of longitudinal elements to the columns. The distance from the end to the disk is limited in order to secure the columns located close to the end from loss of stability. In these cases, the connections are placed in two panels, and the distance between their axes should be such that the forces are not very great. The maximum distances for using disks are based on possible differences in t and are established by standards. At the ends of the building, the outer columns are sometimes connected to each other by flexible upper connections. They are made in the form of crosses, which is advisable from the point of view installation conditions and uniformity of solutions. Upper vertical braces should be placed not only in the end panels of the building, but also in the panels adjacent to the expansion joints, because this increases the longitudinal rigidity of the upper part of the frame. Vertical connections are installed along all rows of columns of the building, located along the same axes. When designing connections along the middle rows of columns in the crane section, you should keep in mind that sometimes you need to have free space between the columns, then portal connections are designed. In hot shops with continuous crane beams or heavy crane-sub-rafter trusses, it is advisable to provide special design measures: reducing the length of temperature blocks. The connections, in addition to conditional transverse forces, perceive wind loads directed at the end of the building and from the longitudinal effects of overhead cranes. The wind load on the end of the building is perceived by the uprights of the end timber frame and is partially transmitted to the connections along the lower chord of the trusses. The tent's ties transmit this force into the rows of columns.

March 1, 2012

To give the workshop spatial rigidity, as well as to ensure the stability of the frame elements, connections are arranged between the frames.

There are connections: horizontal - in the plane of the upper and lower chords of the trusses - and vertical - both between and between the columns.

The purpose of horizontal connections along the upper chords of trusses was discussed in section. These connections ensure the stability of the upper chord of the trusses from their plane. The figure shows an example of the arrangement of ties along the upper chords of trusses in a covering with purlins.

In non-girder roofs, in which large-panel reinforced concrete slabs are welded to the upper chords of the trusses, the rigidity of the roof is so great that it would seem that there is no need to install ties.

Taking into account, however, the need to ensure proper structural rigidity during the installation of the slabs, as well as the fact that the load from the slabs is not applied strictly vertically along the axis of the trusses and therefore can cause torsion, it is considered necessary to install ties along the upper chords of the trusses at the edges of the temperature compartments. Equally necessary are spacers at the ridge of the trusses, at the supports and under the lantern posts.

These spacers serve to tie the top chords of all intermediate trusses. The flexibility of the upper chord between the points secured during installation of the slabs should not exceed 200 - 220. The connections along the upper chords of the trusses are attached to the chords with black bolts.

When making ties, it is important to accurately weld the gusset to the corner, ensuring the appropriate angle of inclination, since with the help of ties the correctness of the geometric scheme of the mounted structure is partially controlled.

Therefore, it is recommended to weld the gussets to the tie elements in jigs. The figure shows simplest type conductor in the form of a channel, on which holes are precisely punched at the required angle.

Horizontal braces along the lower chords of the trusses are located both across the workshop (transverse bracing) and along the workshop (longitudinal bracing). Cross braces located at the ends of the workshop are used as wind farms.

They support the frame racks of the workshop's end wall, which absorbs wind pressure. The belts of the wind farm are the lower chords of the trusses. The same transverse connections along the lower chords of the trusses are arranged at expansion joints(for the purpose of forming a hard disk).

With a large length of the temperature block, cross braces are also placed in the middle part of the block so that the distance between the transverse braces does not exceed 50 - 60 m. This has to be done because the connections of the braces are often made on black bolts, which allow large shifts, as a result of which the influence of the braces re spreads over long distances.

Transverse deformation of the frame from local (crane) load: a - when
lack of longitudinal connections; b - in the presence of longitudinal connections.

Horizontal longitudinal connections along the lower chords of trusses have their main purpose of involving neighboring frames in the spatial work under the action of local, for example crane, loads; thereby reducing frame deformations and increasing the lateral rigidity of the workshop.

Longitudinal connections are especially important for heavy cranes and workshops with heavy duty work, as well as for light and non-rigid roofs (made of corrugated steel, asbestos-cement sheets, etc.). In heavy duty buildings, connections should be welded to the bottom chord.

For braced trusses, as a rule, a cross lattice is adopted, considering that when loads are applied on any one side, only the system of elongated braces works, and the other part of the braces (compressed) is switched off from operation. This assumption is valid if the braces are flexible (λ > 200).

Therefore, elements of cross braces, as a rule, are designed from single corners. When checking the flexibility of cross-tensile braces made from single angles, the radius of inertia of the angle is taken relative to an axis parallel to the flange.

With a triangular lattice of braced trusses, compressive forces may occur in all braces, and therefore they must be designed with flexibility λ< 200, что менее экономично.

In spans of more than 18 m, due to the limited lateral flexibility of the lower chords of the trusses, in many cases it is necessary to install additional spacers in the middle of the span. This eliminates the trembling of the trusses when the cranes are operating.

Vertical connections between trusses are usually installed at the truss supports (between the columns) and in the middle of the span (or under the lantern posts), placing them along the length of the workshop in rigid panels, i.e., where the transverse connections along the chords of the trusses are located.

The main purpose of vertical connections is to bring them into a rigid, unchangeable state. spatial design, consisting of two trusses and cross braces along the upper and lower chords of the trusses.

In workshops with light and sometimes medium-duty cranes in the presence of a rigid roof made of large panels reinforced concrete slabs, welded to trusses, a system of vertical bracing can replace a system of transverse bracing along the chords of the trusses (except for end wind trusses).

In this case, the intermediate trusses must be connected by spacers.

The design of vertical connections is taken in the form of a cross of single corners with a mandatory horizontal closing element or in the form of a truss with a triangular lattice. Attaching the vertical connection to roof truss carried out on black bolts.

Due to the insignificance of the forces acting in the elements of the coating connections, when designing their fastenings, a slight deviation from centering can be allowed.

Vertical connections between columns are installed along the workshop to ensure stability of the workshop in the longitudinal direction, as well as to absorb longitudinal braking forces and wind pressure on the end of the building.

If in the transverse direction the frames clamped in the foundations are an immutable structure, then in the longitudinal direction a series of installed frames, hingedly connected by crane beams, is a variable system that, in the absence of vertical connections between the columns, can fold (the supports of the columns in the longitudinal direction should be considered hinged ).

Therefore, the compressed elements of the connections between columns (below the crane beams), and in buildings with heavy duty operation, the tensile elements of these connections, which are essential for the stability of the entire structure as a whole, are made sufficiently rigid to avoid their shaking. For this purpose, the maximum flexibility of such elements is limited to λ = 150.

For other stretched elements of connections between columns, the flexibility should not exceed λ = 300, and for compressed elements λ = 200. Elements of cross connections between columns are usually made from corners. Particularly powerful cross braces are made from paired channels connected by a lattice or slats.

When determining the flexibility of intersecting rods (in a cross lattice), their calculated length in the lattice plane is taken from the center of the node to the point of their intersection. The calculated length of the rods from the plane of the truss is taken according to the table.

Calculated length from the plane of the truss of the cross lattice bars

Characteristics of the intersection of lattice rods	When stretched in the support rod	When the support rod is not working	When compressed in the support rod
Both rods are not interrupted	0.5 l	0.7 l	l
The supporting rod is interrupted and covered with a gusset	0.7 l	l	l

Calculation of cross braces is usually carried out under the assumption that only tensile elements are working (at full load). If the work of the elements of the cross lattice is also taken into account in compression, the load is distributed equally between the braces.

To ensure freedom of temperature longitudinal deformations frame, vertical connections between columns are best located in the middle of the temperature block or close to it.

But since the installation of a structure usually begins from the edges, it is advisable to tie the first two columns into a frame so that they are stable. This forces us to construct connections as shown in the figure Connections along the lower chords of the trusses and between columns b, i.e., in the outer panels, establish connections only within the upper part of the columns.

Such connections allow bending deformation lower parts columns with temperature changes. At the same time, one of the braces, working under the tensile load of the wind, transfers these forces to the crane beam.

The further path of wind forces is shown in the figure. Connections along the lower chords of the trusses and between the columns b; they are transmitted along rigid crane beams to the middle connections and are lowered into the ground along them. It is advisable to choose a connection scheme such that they adjoin the columns at an angle close to 4 - 5°. Otherwise, the resulting heavy gussets will be too elongated.

Frame vertical connections: a - with a column spacing of 6 m;
b - with a column spacing of at least 12 m.

In case according to technological conditions it is impossible to completely occupy a single span for bracing, and also with large column spacing, frame bracing is installed; in this case, it is believed that from a one-sided load they work to stretch the connections of one corner, and the elements of the other corner, due to their great flexibility (λ = 200 / 250), are switched off from work. With this design of the structure, we get a “three-hinged arch.”

Vertical connections are installed below the crane beam in the plane of the crane branch of the column, and above the crane beam - along the cross-sectional axis of the column. In heavy-duty workshops, the connections below the crane beams are attached to the columns using rivets (mainly) or welding.

"Design of steel structures"
K.K. Mukhanov

The choice of the transverse profile of multi-bay workshops depends not only on the given useful dimensions of the workshop and the dimensions of the overhead cranes, but also on a number of general construction requirements, primarily on the organization of water drainage from the roof and on the lighting arrangement for the middle spans. Water drainage can be either external or internal. External drains are installed in narrow workshops, as well as…