Steel beam arching problem
The method of arching has a parabolic arching and a fold-shaped arching of the steel beam. For the portal frame, the fold-shaped arching is often adopted, that is, at the joint node of the steel beam, the angle of the connecting end plate is controlled to achieve the purpose of arching.
The purpose of the steel beam arching is that after the roof steel beam is deformed by the load, the amount of arching can offset a part of the deformation, and the roof can still maintain a certain slope. If the steel girder is too large, it will make the slope of the roof near the ridge smaller, and the excessive deformation of the steel beam will make the slope of the roof near the cornice too small.
Excessive slope changes are not appropriate. Whether arching or not, how many arches should be a design problem. When the design does not require arching, the allowable deviation of the crown is set to -5~10mm, which means that the construction party does not claim a set amount of arching.
Improper installation of roofing rafters leads to excessive deformation
In some projects, the connection positions of the rigid tie rods and the wind pull rods are different, so that the horizontal support system is not on the same plane, thus affecting the overall stability of the rigid frame. The rigid tie rod and the wind pull rod form a horizontal support system, and the set height should be consistent in the same slope direction.
In the installation of roof or wall purlins, some construction units increase and lengthen the bolt holes of the purlins or rafters for the convenience of installation. The purlin is not only the supporting member of the roof panel or the hanging wall panel, but also the supporting body of the rigid frame beam and column support. The provision of a certain number of braces can reduce the calculated length outside the plane of the rigid frame, and effectively ensure the out-of-plane integral of the rigid frame. stability. If the aperture of the purlin or the pallet is too long and too long, the truss will lose its proper function.
In addition, some units have increased the roof load without authorization. The original design did not consider the suspension load such as the ceiling or equipment pipeline, but the suspension load such as the ceiling was arbitrarily increased during the construction, which caused the steel beam to be too large or collapsed. No unit may increase the load outside the design range without authorization. During the construction or supervision process, if such problems are found, the increased load must be sent to the original design unit for structural bearing capacity review, etc., and the roof lifting can be carried out only when the structural safety and use requirements are met.
In some industrial plants, cranes are designed. Crane beams and crane trusses should not be scratched. In actual construction, the construction and supervision supervision units rarely check the indicator, so special attention should be paid!