多龄期钢框架时变损伤模型研究

对3种不同厚度的钢材标准试件进行酸性大气环境气雾加速腐蚀试验,并对锈蚀后的试件进行单向拉伸试验,得到钢材力学性能随失重率的衰变规律。同时考虑构件截面削弱与材料力学性能降低,建立不同锈蚀程度下的钢框架有限元分析模型,利用非线性静力推覆分析得到锈蚀钢框架结构的整体初始刚度随锈蚀程度增大的退化规律,以表征结构因锈蚀造成的损伤。提出同时反映最大变形效应和累积耗能效应的双参数结构整体地震损伤模型,并在此损伤模型的基础上集合钢材材性试验结果及有限元分析结果,提出适用于锈蚀钢结构的"时变"损伤模型。对比分析以层间位移角及时变损伤模型为性能指标建立的不同龄期钢框架结构的地震易损性曲线,结果表明:随着锈蚀程度的增加,在相同地震动强度下结构超越某一极限状态的失效概率均增大。

Study on Time-varying Damage Model of Multi-age Steel Frame Structures

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.