Applicability of Finite Element Method to Collapse Analysis of Steel Connection under Compression

It is often necessary to study the collapse behavior of steel connections. In this study, the limit load of the steel pyramid-to-tube socket connection subjected to uniform compression was investigated by means of FEM and experiment. The steel connection was modeled using 4-node shell element. Three kinds of analysis were conducted: linear buckling, nonlinear buckling and modified Riks method analysis. For linear buckling analysis the linear eigenvalue analysis was done. For nonlinear buckling analysis, eigenvalue analysis was performed for buckling load in a nonlinear manner based on the incremental stiffness matrices, and nonlinear material properties and large displacement were considered. For modified Riks method analysis compressive load was loaded by using the modified Riks method, and nonlinear material properties and large displacement were considered. The results of FEM analyses were compared with the experimental results. It shows that nonlinear buckling and modified Riks method analyses are more accurate than linear buckling analysis because they employ nonlinear, large-deflection analysis to estimate buckling loads. Moreover, the calculated limit loads from nonlinear buckling and modified Riks method analysis are close. It can be concluded that modified Riks method analysis is most effective for collapse analysis of steel connection under compression. At last, modified Riks method analysis is used to do the parametric studies of the thickness of the pyramid.