Modeling of Crack Propagation in Weld Beam-to-Column Connection Submitted to Cyclic Loading with Cohesive Zone Model

During the earthquakes in Japan and California in the 1990s, cracks appeared in
some weld beam-to-column connections of heavy rigid frame steel buildings. This prompted the necessary assessment of the performance of weld connections in terms of rotation capacity and crack propagation. In the present study, experimental tests were performed where weld connections were submitted to cyclic loadings with increasing amplitude until a macro crack event was reached. However the crack phenomenon depends on many parameters: the geometry,
the material, the welding process…. For this reason, it was interesting to develop a finite element modeling of these connections in order to complete these experiments and perform a parametric study. This paper describes the finite element model development, its material parameter identification and its comparison with experimental results. The weld connections were modeled
by using three-dimensional mixed solid elements. The constitutive laws applied were elastoplastic with isotropic hardening identified for the base metal and the weld metal. Crack propagation was modeled by a cohesive zone model. The parameters of this cohesive zone model were identified by an inverse method with the modeling of three point bending tests of precracked samples performed on the base and weld metals. The fatigue damage generated by the cyclic loading was computed by the fatigue continuum damage model of Lemaitre and
Chaboche, which was coupled with the cohesive zone model.