Common problems in steel structure design:

　　1.The middle column of multi span portal frame is designed as swing column, but in the actual project, the middle column and inclined beam are welded dead, resulting in the calculation diagram inconsistent with the actual structure, resulting in engineering accidents. 

　　2.The design of purling often ignores the stability under the action of wind suction, which makes it easy to lose stability and damage under the action of wind suction. In the design, attention should be paid to check whether the purling section meets the requirements under the action of wind suction. 

　　3.If the shear key is used under the column base slab, or there is a gap, it must be filled with grouting material when the installation is completed, and attention must be paid to the grouting hole when the slab is designed.

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

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