Numerical Simulation of Fracture in Bolted Gusset-Plate Connections and Welded Hollow Sections

Ductile fracture is a common failure mode of components under various loadings, which has recently been identified to be dependent on the first, second, and third deviatoric stress invariants. The fracture can typically be described in terms of the stress triaxiality and lode angle parameter. A newly developed ductile fracture criteria with the above two parameters is introduced, and based on which the fracture modes of the bolted gusset plate connections and hollow sections in gusset plate welded connections under quasi-static loading are simulated. The findings of numerical analysis are compared to experimental results, and acceptable correlations are achieved. The fracture modes, the block shear, and the fracture sequence are well-predicted by the proposed fracture criterion and simulated through finite-element analysis. The bolted gusset plate connections are discussed in detail since they include shear fracture, which is typically challenging to simulate. The influence of lode angle parameter (deviatoric stress portion) on the fracture phenomena is found to be significant and varies with stress states, as well as the stress triaxiality (hydrostatic stress portion). Suggestions on an optimization tool for this type of structure details are put forward based on simulation and experimental results. It is also shown that the newly developed ductile fracture model can be used by design engineers for predicting failure in steel structures under multi-axial stress states.