Effective Length of Columns in Multi-Storey Steel Building Structures(II):Numerical Examples

Firstly,four steel frames with geometric imperfections are configurated and the ultimate load of these frames, Pcr and Hcr, under horizontal and vertical load are obtained through finite element analysis. Then, the ultimate load Pcr and Hcr is used to calculate the internal force of the same four frames without geometric imperfections through the way of first-order analysis and second order analysis. The nominal stress of the column using the formula of the ultimate load capacity of bending-compression members employed in steel structure design code of China (GB 50017) is obtained and compared with the real stress.It is demonstrated that when using the formula of the ultimate load capacity of bending-compression members to check the stability of columns,using the second order elastic analysis to calculate the internal force of the frame and choosing the real length to be the effective length of the column may lead to better results than that through the way of using the first order elastic analysis to calculate the internal force of the frame and choosing the elastic buckling length to be the effective length of the column.