Abstract:In recent years, with the improvements in steel production and processing technologies, steel structures are being widely used in large public buildings. Generally, corrosion is a major problem in the lifetime of steel structures, which leads to the thinning of the structural material, changes in its mechanical properties, and eventually decreasing its strength and ductility capacity. In addition, earthquakes represent one of humanity's most threatening natural disasters. The seismic performance of structures subjected to corrosion and located in highly seismic regions is of great concern. A reasonable damage model that could accurately estimate and predict the degree of damage in steel structures subjected to earthquake action would be of great significance for the theoretical development of performance-based seismic design. In this paper, we conducted accelerated corrosion experiments in an acid atmospheric environment on three standard steel specimens of different thicknesses and then conducted tensile tests on corroded steel specimens to obtain the degradation laws of steel's mechanical properties for increasing rates of weight loss. By considering both the component-section loss and the degradation of the material mechanics, we built finite element analysis models of steel frame structures with different degrees of corrosion. Then, to characterize the structural damage caused by corrosion, we conducted a nonlinear static pushover analysis to obtain the degradation law of the initial stiffness of entire structures with increasing degrees of corrosion. By establishing a two-parameter seismic damage model that considers both the greatest deformation and the accumulated energy dissipation effect at the whole-structure level, combined with our steel specimen tests and finite analysis results, we developed and propose a time-varying seismic damage model that is applicable to corroded steel structures. We also compared the seismic vulnerability curves of steel frame structures of varying ages and analyzed their inter-story drift angles and time-varying damage models as a seismic demand index. The results indicate that with increases in the degree of corrosion, the structural failure probability of exceedance increases with seismic intensity.
