Physical interpretation of SP 294.1325800.2017 design checks based on finite element modeling of truss joints made of rectangular bent-welded profiles

Abstract

The paper investigates the physical interpretation of the chord wall punching verification for joints of trusses made of cold-formed welded hollow sections according to SP 294.1325800.2017. The study compares code-based design checks with finite element analysis results obtained using linear and materially nonlinear models in LIRA-SAPR and the Component-Based Finite Element Method (CBFEM) implemented in IDEA StatiCa. Equivalent stresses and plastic strains were analyzed to assess the actual stress-strain behavior of the joints. The results show that linear analysis overestimates stresses, whereas materially nonlinear analysis adequately describes plastic redistribution and the development of local plastic zones. It is demonstrated that failure of the punching verification corresponds to the formation of a localized plastic zone in the chord wall rather than to the attainment of ultimate stresses. In addition, the effect of joint flexibility on the overall stiffness of the truss was evaluated by replacing idealized joint connections with detailed finite element blocks; it is established that taking the actual deformability of the joints into account leads to a noticeable increase in the calculated deflection of the structure. The proposed interpretation improves the understanding of the physical meaning of the current design provisions and may be useful for the development of more accurate design approaches for steel truss joints.