What problems should be paid attention to in the design of steel structure workshop

Problems needing attention in the design of steel structure workshop Common design quality problems and preventive measures of portal light steel frame

18.9 common design quality problems and preventive measures of portal light steel rigid frame

18.9. 1 The splicing joints of beams and columns are generally calculated as rigid joints. However, due to the thin end sealing plate, the calculation is quite different from the actual situation, so the thickness of the sealing plate should be strictly controlled to ensure that the end plate has sufficient rigidity.

18.9.2 some design inclined beams and columns are calculated according to the connection, but the actual project omits the steel column, and the inclined beams are supported on reinforced concrete columns or brick columns, causing engineering accidents. Attention should be paid to clearly express the joint structure when designing, and the joint structure must be consistent with the calculation.

18.9.3 The middle column of multi-span portal frame is designed as a rocking column, but the column and inclined beam are welded in the actual project, which makes the calculation diagram inconsistent with the actual structure and causes engineering accidents.

The design of 18.9.4 purlin often ignores the stability under the action of wind suction, which leads to instability and failure under the action of wind suction. Attention should be paid to check whether the purlin section meets the requirements under the action of air suction during design.

18.9.5 in some projects, when splicing inclined beams of portal frames, the splicing joints of flanges and webs are placed on the same section, which causes hidden dangers. When designing spliced joints, flange joints and web joints must be staggered.

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18.9.7 The position of corner brace and the setting of purlin (or wall beam) and brace are important measures to ensure the overall stability. Some engineering designs cancel them, which may cause hidden dangers. If angle braces cannot be set for special reasons, effective and reliable measures should be taken to ensure that the flange of beams and columns does not buckle.

18.9.8 If the shear key is used under the bottom plate of the column, or there is a gap, it must be filled with grouting material when the installation is completed. Pay attention to grouting holes when designing the bottom plate.

18.9.9 purlins and roof metal plates shall be selected according to supporting conditions and load conditions, and the thickness of purlins and roof plates shall not be arbitrarily reduced.

Use 18.9. 10 continuous members to save purlins and wall beams. However, many units of the tower connection length have not been determined by experiments, and the tower connection length and connection are difficult to meet the conditions of continuous beams. In the design, it should be emphasized that if continuous purlins and wall beams are used, the length of tower connection should be determined by experiments, and the possible hidden dangers under temperature change and uneven settlement of bearings should also be paid attention to.

18.9. 1 1 In order to save steel and labor, many units cancel the side ribs of purlins and wall beams supported by steel plates, which will affect the torsional rigidity of purlins and the reliability of wall beams. When designing, the specific bearing method should be indicated in the drawings, and the general description should emphasize that the construction unit should not change it at will.

18.9. 12 The flange plates or webs of portal frame inclined beams and steel columns can be changed in thickness, but the flange plates of some units suddenly change from 20mm to 8mm, and the sudden change of adjacent plates is unfavorable to the stress, so it should be gradually thinned in design, and the thickness difference should generally be changed from 2mm to 4mm.

18.9. 13 Some projects were built in the 8-degree earthquake zone, but round steel with smaller diameter was still used as the support between columns. It is suggested that the calculation should be based on the bracing between columns in the earthquake area of 8 degrees, and the angle steel section is generally suitable.

18.9. 14 in some projects, no matter how big the span of portal frame is, the minimum diameter M20 is used to select the column foot bolts, which leads to engineering accidents. The anchor bolts should be calculated according to the most unfavorable working conditions, and should be commensurate with the stiffness of the column foot, and the influence of related unfavorable factors should be considered. This measure is recommended: Article 65438 +08.7. 10.

18.7. 10 Generally, when the span of rigid frame is less than or equal to 18m, two M24s are adopted;

Less than or equal to 27m, four M24； are used;

More than or equal to 30m adopts four M30；;

18.9. 15 part of the portal frame did not take temporary measures to ensure the lateral stability of the portal frame, which caused the portal frame to fall to the ground during installation. It is suggested that the installation requirements of portal frame should be explained in the overall design description.

18.9. 16 roof waterproofing and thermal insulation is one of the key issues, and the design should be coordinated with the architectural profession and effective measures should be taken seriously.

When the span is more than 30 meters, it is more reasonable to use fixed column feet.

As for joists, our practice is to design according to ordinary steel. In particular, the deflection of joists should be controlled. If the deflection of joist is too large, the internal force of rigid frame will change, causing additional bending moment.

The connection between steel beams and columns adopts rigid joints. Sts adopts: the flange and the web distribute the required bending moment in proportion to the bending stiffness, and the shear force is borne by the web. In this way, the flange is welded and the web is connected by friction high-strength bolts, which is inconvenient for construction. In fact, personally, wxfdawn said that it is more practical, that is, the joint bending moment is borne by the flange connection weld, the web connection bolts are only sheared, and the high-strength bolts are only arranged in one row, which is beneficial to construction and simple in calculation.

The shear capacity of the joint area does not meet the requirements: adjust the web width or thickness of the joint area!

Discussion on the design of portal frame connection node-according to the algorithm of ordinary bolt connection

1: it is assumed that the neutralization shaft is in the center of the compression flange; When connecting with high-strength bolts, according to algorithm 2: Assume that the neutralization axis is in the center of the bolt lowering group.

High-strength bolts have pre-tightening force, and the neutral axis is close to the center of mass axis of bolt group under the action of bending moment, which is safe according to the center of bolt group. Ordinary bolts have no pretension, so the supporting point of bending moment is close to the compressed flange. If it is a high-strength bolt, it is unsafe to calculate the bearing capacity of the bolt by using the compressed flange as the supporting point of bending moment.

For portal frame members with variable cross-section, when the change rate of cross-section height is 60mm/m, the height-thickness ratio of cross-section should be controlled according to Article 6. 1. 1 2002, regardless of the shear buckling strength of cross-section. If the height-thickness ratio does not meet the requirements due to this situation, it can be adjusted in any of the following ways:

1) Adjust the change of section height (such as adjusting the node position of beam members, adding and changing sections) to make the change rate of section height meet the requirement of ≤60mm/m as far as possible;

2) Increase the thickness of the web to meet the requirement that the limit value of the ratio of height to thickness of the web is not considered in the post-buckling program;

3) Set transverse stiffening ribs, and when the requirements of height-thickness ratio are met, use the basic component calculation in the toolbox to determine the spacing of stiffening ribs;

If the span is 42 meters, the shear force at the foot of the column will be great, and the shear key of the column bottom plate can not meet the shear requirements. At this time, it can be considered to set a pull rod between the two column feet to reduce the thrust at the bottom of the column.

I made two, one 60m without a central column and the other 102m with a central column. No problem. Generally, the stigma of Ningbo should be 1m~ 1.5m, and all the cushion beams are1.3m ~1.5m. Generally, the roof of this structure is very small. It is important that the structural measures are good, the joints are conservative, the beam-column ratio is guaranteed and the deflection is strictly controlled. It is important that the support system must be adequate, preferably conservative and safety first. The stress ratio is actually good, but it must be noted that the height-width ratio of the beam should not exceed 5. In fact, the portal frame with the largest span in China has reached 74M, and there is nothing too complicated in calculation. It should be noted that the out-of-plane support of the steel beam section is too large, and the deflection of the steel beam should be strictly controlled. According to the calculation of 70M, the deflection is 1/400, and the mid-span deformation is already 175mm, which is horrible. In addition, the suction condition should also be calculated. If used as a hangar, you should pay attention to two rigid frames near the gable door. Excessive deformation of rigid frame will affect the installation of gate.

The variable cross-section beam can determine the cross-section size and variable cross-section position according to the moment inclusion diagram of the beam.

It is best to set the variable cross-section position near the anti-bending point of the beam.

You'd better look at the shape of the bending moment diagram of the beam first.

In addition, the segment length of the beam should be considered according to the transportation conditions. Generally, it cannot exceed 20 meters.

Material utilization ratio, for ordinary beams, the control of material utilization ratio is mainly to control the size selection of flange width and web height to meet the specific modulus, so that the cut plates will not be wasted. You don't need to think too much about subdividing positions.

The modulus of steel plate should be considered when dividing. Generally, the steel plate is 8 meters long, so the beam length is 8 meters or 12 meters is the best.

When STS is used to calculate live load, when snow load plays a controlling role, where is the distribution coefficient considered in STS?

Only snow load can be manually multiplied by its distribution coefficient and then input as live load.

4.5. 1 in the Code for Load of Building Structures (GB50009-200 1) stipulates: "When designing roof slabs, purlins, reinforced concrete overhangs, awnings and precast beams, the concentrated load (self-weight of people and gadgets) used for construction or maintenance shall be1. (Note: 1. For light or wide members, when the construction load exceeds the above load, it should be checked according to the actual situation, or temporary facilities such as padding and support should be used to bear it; 2. When calculating the bearing capacity of overhangs and awnings, the concentrated load should be taken along the board width 1.0m; When checking the overturning of overhangs and awnings, a concentrated load should be taken every 2.5~3.0m along the board width. " It can be understood from the above that the concentrated load of construction or maintenance need not be considered when designing rigid frame members, but only when designing roof panels, purlins, reinforced concrete overhangs, awnings and precast beams. Therefore, the concentrated load of construction or maintenance is not considered at the same time as the load other than the self-weight of roofing materials or purlins. It is also stipulated in CECS 102: 2002.

Therefore, when modeling and calculating the main steel frame in PKPM, it is not necessary to input the maintenance load at all, but when calculating the purlin in the toolbox, it is necessary to calculate the concentrated load of construction or maintenance. The default value of the program is 1.0KN, which is very reasonable and completely meets the checking calculation of the most unfavorable position. As for the statement that the construction or maintenance load is greater than the live load and snow load, it seems reasonable, but there is no complete basis.

-Virtual beam is a specific term in PKPM. Because the definition of PKPM's opposite load is an area, and an area should be surrounded by beams, PKPM can't be an area and can't distribute loads when modeling bent in three dimensions due to the lack of the definition of out-of-plane beams. Therefore, a virtual beam is built here just to arrange the load. Generally, the imaginary beam I use is round steel D 12. It turns out.

1, which is convenient to input herringbone column support in the wall design of three-dimensional modeling;

2. Three-dimensional modeling is only used for wall and roof design, and then pk files are formed and calculated in two-dimensional modeling. Three-dimensional modeling itself does not calculate beam-column structure, so there is no error problem of calculation results;

3. It is most convenient to form the roof slope through the height of the upper node;

4. Hinges cannot be set during 3D modeling.

Firstly, the rigid frame size is obtained by two-dimensional modeling, and then three-dimensional modeling is carried out, which is convenient for the design of walls and roofs and the drawing of various floor plans.

3D modeling itself does not calculate beam-column structure. Compared with two-dimensional modeling, the advantage of three-dimensional modeling is that top purlin, wall purlin, wind-resistant column, water strut, column brace and wind-resistant column can be calculated in the whole structure (just click the component with the mouse and then input some simple design conditions according to its prompt).

In the design process, it is a feasible method to solve the instability of the lower flange of purlin if the support is set near the upper and lower flanges of purlin or the support is replaced by angle steel. This can not only greatly enhance the stability of the lower flange of purlin, but also improve the overall stiffness of the roof, which has a good effect on the installation and normal use of roof panels. I have used it in practical projects, and the effect is very good.

Purlins in door steel are regarded as supports. Consider cold bending according to the support below.

So designers should compare dead load and wind load. Then determine the position of the bracket. If the wind load is too heavy, it is best to stack it up and down.

Problems needing attention in the design of steel structure workshop (2)

According to the stability calculation formula of steel beam, the lateral support point of steel beam should have both lateral stiffness and torsional stiffness, so support should be set at the compression flange to prevent the beam from lateral torsion. If there are reliable anti-torsion measures to ensure that the purlin is not twisted, only one support can be set, and the upper flange can also be set at the lower flange.

I have seen many projects set up supports in the middle of purlins for the convenience of factory processing. I don't know if it can prevent the upper flange or lower flange of purlin from becoming unstable. Of course, as long as the roof panel does not use hidden color plates. Under the fastening of self-tapping screws, the upper flange of purlin will certainly not be unstable.

The lap length of Z-shaped purlins should be no less than 10% of single span and no less than 600mm, and the lap length of end span purlins can be 20% of that of single span purlins.

All the columns and beams of the factory building are deviated, and some are deviated by one or two centimeters. -After the high-strength bolt is installed, it is not allowed to weld the end plate again, because under the influence of high welding temperature, the high-strength bolt rod will be stretched by heat, and the pre-tensile stress originally applied by the high-strength bolt will be lost, which will directly affect the safety of the connection node!

The end plates of columns and beams are not suitable. You can add a steel plate between the two end plates, then make a calf leg under the end plates, and then change the high-strength bolt into a pressure-bearing type.

Because there is no problem with the foundation, the reasons may be as follows:

65438+ material design reasons should be remedied in time; The causes can be remedied by adding gaskets. -If it doesn't work, it can only be shipped back to the processing plant.

Articulation of pendulum column refers to the release of rotation in the plane of rigid frame, and the setting of bearing is to transfer the horizontal force between rigid frames, regardless of whether it is pendulum column or not. In order to ensure the overall stability of the factory building, whether it is a rocking column or not, the support between columns should not be omitted.

Adding or not adding support between columns depends on the situation. Usually, if the out-of-plane connection of rocking columns is hinged (the top and bottom of columns are hinged), in order to prevent rocking columns from forming out-of-plane unstable systems, adding supports between columns can form a stable system and reduce the out-of-plane calculation length, which is more economical. Of course, if the support is not allowed in the middle of the factory building due to technical limitations, it can be made into a rigid frame out of the plane of the swing column (similar to the principle of giant structure, and the effect of transferring horizontal force can also be achieved by making two horizontal supports connected by column spacing and the support between side columns, which can replace the support between columns), and the calculated length of the rigid frame can be used as the calculated length out of the plane of the swing column. There is also a typical case, that is, when the skin effect is considered in the calculation (the stiffness of the skin should be very large), there is no need to increase the support between columns, and the out-of-plane calculation length of the rocking column can be calculated according to the finite element analysis, which belongs to the spatial category and cannot be considered by the general program. At the same time, the requirements for the support system are also great, which need to be determined according to calculation.

The first two items "vertical distance between horizontal load of crane and nodes" need to be calculated according to product samples, and how to calculate them can be found in textbooks. Item 3 is related to the type and tonnage of the hook, which is a percentage figure and is determined according to the specifications. Four items were detected in the sample. If the factory manufacturing module is implemented, items 5 and 6 are constants. Item 7 is related to the height of crane beam and track type.

—— 1, 2 and 4 are exactly the maximum wheel pressure, minimum wheel pressure and the maximum reaction force generated by the bridge weight at the bearing, which need to be calculated according to the crane parameters, crane beam span, etc. and the reaction influence line. ——sts crane data refers to the maximum wheel pressure generated by the pointer on the rigid crane. The crane manufacturer gives a single wheel pressure, which needs to be calculated manually in sts.

-calculate the beam first, and then calculate the structure.

Determine the crane manufacturer and calculate the walking beam according to the manufacturer's data; If there is no fixed manufacturer, data calculation can be directly imported into the new STS. After outputting the file, there are: vertical load of crane caused by maximum wheel pressure, vertical load of crane caused by minimum wheel pressure, horizontal load of crane and weight of crane bridge. These four data will be imported when calculating the structure input crane load. "Eccentricity between vertical load of crane and left node" and "Eccentricity between vertical load of crane and right node" are the distances from the center line of beam to the center line of column. The vertical distance between the transverse horizontal load of the crane and the node is the distance from the support surface to the top of the track. In addition, it is necessary to add a dead load value caused by the equal weight of the moving beam track at the bracket.

The crane data in STS database seems to be all bridge cranes without beam cranes. If it is a manual or electric beam crane, it may be too big to use this data for calculation.

Just took over an industrial workshop, with side columns 38 meters high, 56 meters across and 6 meters apart. There are two 35-ton cranes with a lifting height of 28 meters, light roofs and light walls. I think the preliminary design scheme is as follows: the roof adopts lattice column and grid structure. How does STS simulate such a structure?

With the "bent frame" module, it can be assumed that the roof grid is infinitely rigid, the columns can be solid web columns, and 35T is not too big. Pay attention to the specification (GB 50017; For columns; The grid structure uses 3D3S software, and the code uses grid structure code) and the selection of wind load shape coefficient. The grille bracket is hinged. It is best to calculate the bearing capacity with 3D3S first, and then with the "bent frame" in STS.

About the structural layout of the workshop in Pugang-we are now using a 50-ton crane with a single span of 36 meters. I don't know what are the requirements for the structural layout and the type of steel column section, whether it is a cross column or an H-shaped column, whether it is necessary to use H-shaped steel for cross support, and what are the requirements for the support?

A 50-ton crane is a dividing line, and columns can be made of solid webs or grids. Generally speaking, if it is a single span, lattice columns can be considered, so that the displacement can be easily satisfied. If it is multi-span, solid web can be considered, because the processing of solid web is relatively simple and the displacement is easier to control than that of single span. The amount of steel used is similar.

The design of the intermediate working system of 50t crane should focus on the following aspects:

1. Strength, overall stability and local stability of beams and columns (flange width-thickness ratio, web height-thickness ratio, slenderness ratio, etc. ).

2. Fatigue calculation should be considered when calculating crane beam.

3. The horizontal support of the roof should be arranged reasonably, and the longitudinal support system should be arranged at the same time to ensure the overall stability in the longitudinal direction.

4. The deflection of the roof beam should be slightly stricter (generally controlled by 1/250).

5. The arrangement of support between columns and expansion joints shall comply with the regulations.

6, should consider the role of the earthquake.

7. Walkways and crane access ladders should be considered.

Brick wall fence of structural workshop-I built a separate factory and maintained it with bricks. In order to maintain the overall stability, it is necessary to set up tie bars between brick walls with steel columns. I didn't find any drawings or specifications, only concrete columns, which said the spacing was 500. But at that time, I thought that the steel column was welded casually and the distance was too small, which might reduce the strength of the column. I reluctantly adopted 1000, but the drawing company disagreed. They say 500 is necessary. I guess they also used the specifications of concrete columns. Please tell me what to do and what measures to take. Does it have to be 500? Will it reduce the strength of steel columns?

-It should be 500. Did you control the pressure to 105%? You are worried that welding will weaken the strength of the column. Under normal use, the wall is beneficial to the column (in terms of observation results and use effect).

-Brick maintenance is a self-supporting wall, so it is enough to check the height-thickness ratio. The spacing between brace and column is generally 500, which mainly strengthens the out-of-plane stiffness of the wall and is beneficial to the stability of the wall under earthquake.

Concrete column+steel roof truss, how to consider the steel roof truss-the structure of steel roof truss on concrete column, and how to consider the steel roof truss in the spatial modeling of concrete column below?

-If PKPM is used, it can be simulated by virtual beam. The function of virtual beam;

1. Divide rooms to transfer the surface load borne by steel roof truss.

2. Concentrated load can be added to the virtual beam.

3. Simulate the axial horizontal stiffness of steel roof truss.

Problems needing attention in the design of steel structure workshop (3)

Stability calculation of brick partition wall in steel structure workshop-This project is designed at hand. The workshop is 73. 1m long, 47.3 wide, 7.2m column spacing, 5.2m cornice, double slope roof, 23.65m mid-column half span, on-site composite roof, brick external wall and internal partition wall. There are doubts about checking the height-thickness ratio, which remains to be pointed out by experts. 556。 6666666666 takes the column spacing of 7.2m as the transverse wall spacing (obviously rigid scheme), but whether the rigid frame can be used as the transverse wall of the external wall is different from the masonry code. The column foot of the steel column in this design is hinged, and the lateral displacement of the column top is controlled according to the door steel code (1/240), but the masonry code 4.2.2 requires the maximum lateral displacement as the transverse wall condition.

2. The most troublesome thing is that there is an inner partition wall, which is built to the bottom of the inner roof panel at the third place between the two rigid frames, and S = 47.3 m. It can only be an elastic scheme, and the theoretical calculation is difficult to meet. I was told that it is reasonable to add structural columns according to the spacing of wind-resistant columns. A ring beam is added at 3.6m, and a ring beam is added at the top of the brick wall. The top of the structural column is connected with the roof lacing with a spring plate. I wonder if the ring beam added in the middle of 3.6m can halve the calculated height of brick wall? I don't think adding pilasters and constructional columns to a brick wall can change the calculated height of the whole brick wall. It is not economical to add pilasters and constructional columns to the brick wall to ensure the stability of the wall. The most important way to ensure stability is to control the spacing between transverse walls.

1. See Code for Design of Masonry Structures 6. 1.2. 1. When b/s≥ 1/30, ring beam can be regarded as the fixed hinge fulcrum of pilaster or structural partition (b is the width of ring beam). Ring Liang Kuan is 240,240x30 =.

2. The lateral displacement of column top is controlled according to the code for door steel (1/240), which is inconsistent with the stiffness of masonry structure. The outer wall can be designed as a fast rigid body attached to the steel column by rigid body rotation. The weight of the external wall is borne by the foundation beam, which sits on the bracket of the steel column, thus releasing the corner between the wall and the ground.

3. Constructional columns should be made along the steel column to enhance the integrity of the wall and the steel column (lacing connection), which is beneficial to earthquake resistance.

1. When making reinforced concrete pilaster, the pilaster feet should be just connected and an independent foundation should be made. After pilaster construction, the wall should be built.

2. The reinforced concrete pilaster and the roof steel structure are connected by spring plates to transfer horizontal force and release vertical displacement.

3. The top of the wall should be a pressure beam. There should be a proper gap between the pressure beam and the roof steel structure. It is reasonable that the door only recommends light (flexible) wallboard for maintenance, which avoids the rigid contradiction between the main structure and the maintenance structure.

Concrete column and steel roof truss beam to solve thrust?

If the steel roof truss beam refers to H-beam, there are the following treatment methods;

1. Tension braces are added at both ends of the steel beam, and vertical braces are connected with cross braces. 2. The bolt hole at the joint between the steel beam bracket and the concrete column is made into a long round hole.

Concrete columns are brittle materials, while steel beams are flexible materials. How to make them rigid? It is more suitable to connect with hinges.

Span 30 meters, height 15 meters. The original design of steel roof truss and steel concrete column has been completed, and Party A needs to change the steel beam. We must make a 2-meter-high portal frame with hinged column feet. After calculation, under the action of horizontal force, the displacement of the stigma is too large, so we have to add a horizontal pull rod. After calculation, 36 round bars are needed, so the construction is too difficult. Later, it was changed to 24.5 oil-immersed steel wire rope, and 7 tons of prestress was pulled after dead load.

In principle, the horizontal force of steel beam cannot exist, otherwise, the thrust concrete cantilever column will be unbearable.

1. If the horizontal thrust is 2 tons, the column height is 7 meters and the bending moment is 140kn.m, please try to find out how many steel bars you want. 400X400 concrete column, one side should be equipped with 3@25 (not easy to calculate and estimate);

2. Generally, steel beams are connected with column tops by bolts; It is important to consider promotion.

3. The horizontal force can be released through the elliptical space, although it will be a little bit, but it is much better.

4. Strictly speaking, bearings made of round steel should be set at nodes.

5. If you want to just connect, it is ok, but there may be more bolts; The beam section must also be designed according to the rigid connection.

A 38-meter-span steel beam and concrete column structure, I use a roof truss with the lower chord folded down, but it is not a roof truss. I suggest you read an article about the steel roof truss with the lower chord folded downwards in industrial buildings-one end is supported by a flat support, and the other end is supported by rubber.

For this kind of light steel roof with small span, it can be made into a simply supported beam, and the lower flange of the simply supported beam is leveled, and the upper flange is adjusted according to the slope of the roof (generally, the slope of the roof is smaller), which can also facilitate the suspended ceiling under the beam.

When I make a 36M steel roof, I use sliding at both ends (oblong hole 25X60), and the length of oblong hole must be considered as 1/2 greater than the total displacement, otherwise the anchor bolts will be easily cut off (only two). Horizontal rigid tie rods between roof trusses are very important.

Add a short steel column under the steel beam, which is hinged with the concrete column, and the steel beam is just connected-I have dealt with this problem, with a span of 27 meters and a crane. If it is simply supported or hinged, it is difficult to meet the needs of deformation. We use rigid connection, and the engineering practice is ok, but the construction is a bit difficult, so we can't make the problem absolute. When dealing with joints, we refer to the relevant regulations of rigid (reinforced) concrete. After completion, the use effect is also good. What needs to be improved is how to make the joint design convenient for construction.

This topic is very interesting. There are several arguments:

1, just received;

2. Hinged type;

3. One end is hinged and the other end is hinged in a sliding way;

The following is an engineering example of this connection that I personally experienced. For your reference in design.

1974 I directed the installation of steel roof truss at the construction site of a long-distance bus station in Beijing. The process is as follows:

1, steel roof truss is hoisted in place. Preliminary connecting bolts (bolts are not tightened at this time);

2. Adjust the position of steel roof truss (for crosshairs);

3. Temporarily fix the upper chord of steel roof truss with two groups of Chinese fir (the hook is not loose at this time. );

4. Check the verticality of the steel roof truss with a wire pendant. Adjust the verticality of steel roof truss with two groups of Chinese fir.

5. Tighten the anchor bolts of the steel roof truss;

6, welding;

7, crawler crane luffing, hook loose (at this time can only luffing, such as hook loose, crawler crane boom due to elastic effect, steel roof truss will be offset);

8. Install various supports;

9. Hoisting large roof slabs.

In this way, the installation of two steel roof trusses (one section) is completed. At this time, the comrades of the design institute came. Say it won't work. One end of the design is hinged and the other end is supported by a sliding hinge. But we couldn't design at that time. Design the homework accordingly. The steel roof truss is very unstable and dangerous during installation! Finally, it will be discussed according to the original installation process.

When I design steel roof trusses and columns in the future. Consider the installation process factors. The theoretical stress state of steel roof truss is close to reality.

1. It's not beautiful to add a tie rod at two foot supports, but many owners still accept it.

2. Add a small steel column and connect it with the beam steel, so that the horizontal thrust can be converted into bending moment, and most of it will be eaten by the rigid joint.

3. The best method is similar to the first point. I have seen it in the manuals of ABC and Zamir-just pull the lower flange of the simply supported beam horizontally, so there is a horizontal thrust in theory, but think about it, this lower flange can play the same role as the round steel tie rod at point 1! There is actually no thrust. The effect is the same if the lower flange changes its cross-section downward and is lower than the hinge support on both sides.