Multi-scale analyses on seismic damage and progressive failure of steel structures

This paper is aimed to develop a numerical procedure for multi-scale analyses on seismic damage and progressive failure process in steel structures by considering meso-scale damage evolution based on CDM constitutive model at vulnerable locations. The mechanism of seismic damage or local progressive failure and their effect on nonlinear dynamic behavior of structures are then explored with the developed procedure. The multi-scale modeling of structural damage is developed to describe the phenomena that some joint parts at vulnerable locations with meso-defects in a structure show nonlinear damage evolution or local failure due to stress concentration while mostly parts of the structure remain elastic and show linear response. A ductile damage constitutive model is chosen as the description of meso-scale damage evolution in the numerical analysis on damage and progressive failure of steel structures under seismic loading, and the developed numerical procedure is implemented with the UMAT subroutine to introduce the damage constitutive equations and incorporate into multi-scale computations of seismic response performed with the software ABAQUS. Effects of meso-scale damage evolution on seismic response and progressive failure are analyzed, respectively, for a dog-bone joint component and a truss structure under ECCS cyclic loading with the developed numerical procedure. The results show that, the developed numerical procedure is available for analyses on seismic damage and progressive failure, and is useful for exploring mechanism of seismic damage and their effect on nonlinear dynamic behavior of structures under seismic excitations with micro-seismic scale intensities or several earthquake actions. The effect of evolving damage on the material degradation gives reasonable explanations for the phenomenon of large structural deformation and progressive failure under seismic loading. The global carrying capacity of the structure decreases with the increase in damaged area and progressive failure at the welded joint or other vulnerable areas, which at last leads to the occurrence of structure failure.