A 3D frame element for large rotations based on the rigid-body–spring concept for analysing the failure of structures

Efficient modelling of the failure process of frame structures is a challenging research topic because of the complex interaction of geometrical and material nonlinearities. Here, a 3D rigid-body-spring based frame element which has previously been shown to be energy equivalent to a continuum based reduced integration element is extended to the case of large rotations. The new model is applied successfully to classical benchmarks for buckling, bending and torsion under large rotations reported in the literature. For the new model, plastic curvature jumps localise within one element, which makes the approach suitable to model plastic hinges with a coarse mesh. The performance of the approach for failure analysis of structures involving the interplay of geometrical and material nonlinearities is further demonstrated by modelling a three-dimensional steel frame.