Analysis and treatment of the deformation of the steel structure of an industrial plant
The analysis and treatment of the deformation of the steel structure of an industrial plant. Ma 1 Co., Ltd. Design Institute 243000. The reliability of Liren can ensure the construction of the crane's plant by supporting the upright rigidity of the reasonable setting of the roof frame rods. Through the investigation and analysis of the deformation quality of the steel roof truss of the industrial plant, the reinforcement of the roof truss and the roof system Yankang mechanical warehouse were established in the early 1970s. The single-layer brick porch structure porch spans the Fenke-type light-handle asbestos 7. Surface, he is due to production; it is necessary to dismantle the original warehouse 716 line and rebuild the original warehouse 17 line. The newly built warehouse is also a brick-concrete structure with column spacing. The span is unchanged and the original truss is used. Asbestos tile roof, set 6, = 50 continents. 5 = 105, 1 electric single hanging beam platform. Column corbel elevation 5.1. Column top elevation 681 masonry 1 composite column. Steel lax concrete, soil independent column foundation, and foundation beams under the enclosing brick wall 1. To the beginning of 1996, it was found that the middle joints of all the lower chords of the roof truss were burned down with a deflection of 10 or more. This phenomenon was slight in the old 17-line old warehouse.
The chord is 2505, the lower chord is 2 to 5 parent 5, the compression member is selected to have a cross section of 21454, and the rest of the tension members, including the main tension rod, are all called. The sail analyzes the tension and compression rod of the roof truss according to the force of the rod The selection of materials is correct, and the distinction between tension and compression rods is also clear. 2 The deformation of the roof truss was not found when the project was completed and put into production. The deformation of the roof truss was discovered after the plant was put into use for many years. It can be considered that the deformation of the roof truss and the construction process of the secondary use of the roof truss It has nothing to do with removing it from the original mechanical storehouse and then hoisting it again; the original roof truss was designed and manufactured by the factory itself, due to the analysis of the old mechanical storehouse 17 line 1. Roof frame rod made by Bao Guyu male born in April 13th Engineer No. 4 1 New mechanical library; 2 original library knowledge; 36! = 50, 5 = 10.5 1 electric hard lifting beam; 4-ring beam to check the roof support. No shear damage and missing welding of the weld at the support are found, and the embedded parts of the column head are intact. It can be judged that the deformation of the roof truss is not caused by the deformation of the support.
Check the setting of the roof support, it can be said that the entire roof is not provided with support, and the instrument is provided with scissors supports in the 2 compartments of the roof truss. For such scissor braces, when the angle of the cross bar is small and there is no pavilion, the 2 layer cover support is provided with 1 scissor brace; 2Bian pull the diagonal bar up and down the horizontal bar, the force characteristics and mechanism and the regular roof cause Scissors support is a variable system, while the vertical support of a regular roof is a non-variable system. Based on the above analysis, it can be said that the support setting of the roof is unreasonable. The reasonable setting of the support system is an important measure to ensure the normal operation of the roof truss. The support system connects each roof truss to form a geometrically unchanged spatial structure, so that the roof truss can be stabilized, and can ensure that all the rods of the roof truss have sufficient rigidity in and out of the plane.
The standard setting form of the vertical support of Pavilion 3 In addition, as far as the roof truss itself is concerned, there is no vertical zero bar in the middle of the roof truss, and the slenderness ratio of the middle joint of the lower chord = 408 is too large, far exceeding the specification stipulated = 250300. Relatively speaking, its rigidity It's very small.
The most important point is that the new warehouse has frequent use of cranes. The same roof truss does not appear to be used during the use of the old warehouse, but the deformation occurs during the use of the new warehouse. Therefore, the change of the crane's dynamic load is caused by the roof truss. The real reason for the deformation. Since the roof truss is a light-cut steel roof truss, except for the lower chord, 2145 and 5 are used, all the other tension rods are made of 18mm round steel. The slenderness of the round steel is large, the rigidity is small, and the joints of the roof truss are eccentric, which makes it easier to buckle out of plane. The lower chord of the roof truss and the length ratio of all the tension rods are large, resulting in a small overall rigidity of the entire roof truss, and because the support of the entire roof is not provided or unreasonable, the spatial stability is poor, and it is easy to vibrate under the disturbance of dynamic load; the entire roof truss and roof The rigidity of the cover system is small, so the natural vibration period is long. It is close to the power cycle of crane operation, and it is easy to generate resonance with crane driving vibration, which causes secondary stress and buckling of the rod.
The long-term effect of the dynamic load of the crane causes the vibration force of the roof system, and the configuration and layout are also the same. The old mechanical warehouse roof truss is slightly deformed. Judging from the service life of the new and old mechanical warehouse roof truss, the strength of the roof truss meets the requirements, and there is no problem of insufficient strength of the rod. The difference between the new and old mechanical warehouses is the addition of cranes in the new warehouses.
3 According to the on-site investigation, no cracks were found in the wall and the ground. The re-check of the elevations of the tops of the two columns is only different from each other. 3. The span ratio with the roof truss is much smaller than the allowable value of 120, 1 and 571000. The horizontal deformation of the two columns of columns is reviewed by the method of the horizontal column hanging vertical line of the same column column truss support. In addition, the wall body has a cast-in-place ring beam in the column and the top of the column. Except for cracked cracks on the inside and outside of the wall body, there are no cracks that are consistent and regular. This also reflects that the building foundation is stable, there is no local settlement and the difference between the two rows of settlement; in addition, the self-weight of the wall, the wall load is eccentric to the column, even if there is a relative settlement difference, the lateral deformation of the column will not be oriented Inwardly flexes the lower string of the roof truss. In short, it can be considered that the roof truss deformation is not the result of foundation settlement and lateral deformation of the column.
Force the roof load system's self-weight load and dynamic load to continuously do work on the roof truss system. According to the external force work of the elastic body equal to the deformation energy of the system, it can be seen that the external force work continues to increase, and the tensile stiffness of the rod is 4 and the torsional stiffness is 671; And the bending stiffness 7 itself is small and in a constant state, reflecting the increase in the additional axial torque and bending moment of the rod, and its corresponding deformation is also continuously increasing. It can be judged that the deformation of its roof truss is caused by long-term accumulation. From the external force work = what is the external force work, the household is the generalized force, and what is the position in the direction of the force corresponding to the generalized force, we can see that the displacement deformation is vertical in the direction of the force, so the roof truss is deformed in the vertical direction. So far, it also proves that it is not appropriate to use round steel for the roof frame members of a factory with a crane similar to a bridge crane with greater power, and the members should have a fixed rigidity. Of course, due to the low rigidity of the roof truss, the lateral effect of the crane is also the reason for the deformation.
Since the gables at both ends of the warehouse are brick walls, and the top is cast-in-place top beams, there are two cast-in-situ ring beams in the whole enclosure wall, so the whole wall body is well connected. Have a fixed support role. The length ratio of the upper chord in the check calculation is in-plane = 103; out-of-plane entry = 137, both meet the requirement of human entry = 150 200, and the crane's lifting capacity is relatively small, and the roof load is light, so the entire roof system does not collapse and collapse . According to statistics, accidents caused by collapse of roof truss due to imperfect roof support system are not uncommon. Therefore, the setting of the support must meet the requirements of the specification.
In order to emphasize the importance of reasonable setting of support, we will explain from the design calculation of the bent frame design calculation is to assume that the rigidity of the roof beam is infinite. If the bracing setting is unreasonable, the space stiffness of the roof is poor, and the stability is left. It assumes that the rigidity of the bent beam is infinitely large and cannot be established, which directly affects the accuracy of the calculation.
2 Analysis results From the above analysis, it can be concluded that the cross-section of the roof truss meets the strength requirements, and the strength of the roof truss itself can be satisfied; there is no settlement of the foundation, and there is no lateral deformation of the column; the support node is intact and no displacement.
The reason for the deformation of the roof truss is that the roof of the roof truss is made of round steel. All the tension members of the roof truss have a slenderness ratio that is too large and the rigidity is small; the roof support is not provided or is unreasonable; the dynamic load of the crane is The main cause of deformation of the roof truss. The design of the roof structure and the stiffness and support settings of the structural members shall meet the requirements of the specifications.
3 After comprehensive analysis of the above factors, Likougu decided to strengthen the deformed roof truss. First remove part of the roof load, adjust the deformation of the lower chord with a jack in the middle of the lower chord of the roof truss, and then set the middle cross zero bar 245, 5. At the same time, add the same to the lower chord of the roof truss and the main tension rod 4.
According to the specification requirements, a horizontal tie bar is set in the middle of the lower chord between the roof truss, at the same time, a vertical tie bar is provided at the scissors support, and a horizontal support is set between the two ends of the upper chord. 5. Check the length ratio of the rod after the same, the main pull is inclined In-plane = 7; out-of-plane = 152; the lower chord is flat and curved, and the outer legs of the claw face are satisfied! = 1 Dong 4 dropped off the string and the main pull diagonal bar to reinforce the small tip 1 main pull inclined rod; 2 rhythmic frame lower string winter 5 plus rear roof support settings 〃.
8.18, Winding water, supporting 0 upper and lower stringing rods; the original scaffold was put into production after being treated with the same truss for more than 3 years. The factory was commissioned to monitor the site, and the truss almost did not deform again, reaching the strength and solid treatment Purpose, to prove that the same design meets the specifications.
The analysis and treatment of the steel structure deformation of an industrial plant Baogu Yu. , U.1
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