Cyclic fracture simulation through element deletion in structural steel systems

Abstract

This paper presents a finite element-based model for direct simulation of cyclic fracture in steel components and connections with application to predicting failure and collapse of steel structures. The formulation couples a plasticity model for large deformations that captures plastic work stagnation and the Bauschinger effect with a two-stage damage model to simulate fracture initiation, propagation, and failure through an element deletion strategy. The model includes the non-proportional loading and load-history effects in the fracture initiation and propagation process. Fracture initiation and propagation is controlled using new fracture initiation strain and fracture energy surfaces with stress triaxiality and Lode angle dependance that can represent different fracture behaviors. Model calibration is discussed for common grades of structural steel, weldments and bolts using typical material tests. The model capabilities are validated against experiments including ancillary material tests, components, and subassemblies of steel structures that experienced fracture subjected to monotonic and cyclic loading. A culminating validation is conducted on a four-story steel frame structure tested to collapse. The proposed model provides a robust and valuable tool for stability analysis and simulations of damage and collapse triggered by fracture in components and connections of three-dimensional steel structures subjected to extreme loads.