循环荷载作用下结构钢材本构关系试验研究

Experimental Study of Structural Steel Constitutive Relationship under Cyclic Loading

为准确模拟结构的地震响应,寻找在循环荷载下钢材的本构关系,采用工程常用Q235B及Q345B钢材共50个试件,施加多种加载制度,分析其单调性能、滞回性能、宏观微观破坏形态、延性特征以及损伤退化特性,并采用Ramberg-Osgood模型对循环加载骨架曲线进行拟合,进而得到Q235B及Q345B钢材在循环荷载下的一维应力应变关系骨架曲线;在Chaboche钢材塑性本构模型的基础上,通过试验标定,确定了两种等级钢材本构模型的关键材料参数,并结合通用有限元程序ABAQUS对试验结果进行有效模拟,为今后准确计算结构在地震荷载下的反应提供重要依据.结果表明:钢材在循环荷载下的反应与在单调荷载下的本构关系有很大差别,循环荷载下的骨架曲线对于准确的数值模拟起到重要作用;循环的圈数以及幅值会严重影响构件的断裂延性,钢材在循环荷载下的破坏应变不能按照单调荷载来确定.

In order to study the seismic performance of steel structure in China and look for the constitutive relationship of steel under cyclic loading, a variety of loading was imposed on total 50 specimens of Q235B and Q345B steel and their monotonic behavior, hysteretic behavior, macro-and micro-failure modes, duc-tility characteristics and cumulative damage degradation were investigated; Ramberg-Osgood model was used to fit the curve of cyclic loading and then the one-dimensional stress-strain skeleton curves of Q235B and Q345B under cyclic loading were obtained; based on the Chaboche plastic constitutive model for steel, two material parameters of constitutive models were obtained from experimental data calibrated with ABAQUS which provided an important basis to accurately calculate the response of future structures under earthquake. The results show that the response of steel under cyclic loading and the monotonic loading are quite different, therefore, the skeleton curve under cyclic loading plays an important role for accurate nu-merical simulation; cyclic loops and amplitudes seriously affect the fracture ductility of specimens and the failure strain under cyclic loading cannot be determined in accordance with the monotonic loading.