Geometric and material nonlinear analysis of structures comprising rectangular hollow sections

This paper presents a nonlinear finite element analysis of structures comprising thin-walled rectangular hollow sections. Nonlinearities due to both the change of geometry and material yielding are included, incorporating also the effects of strain-unloading. The geometry and the stiffness of the elements are modified and used to update the structure tangent stiffness matrix. An iterative numerical procedure combining the arc-length and the work methods is employed for the solution of the incremental equation of equilibrium. The method has been applied successfully to predict the nonlinear load-deflection behaviour of isolated cold-formed SHS columns, fabricated RHS parabolic fixed end arches, and double chord SHS trusses having different joint configurations.