剪力墙非线性分析单元MFBFE的理论及开发

THEORY AND PROGRAM IMPLEMENTATION OF MFBFE ELEMENT FOR NONLINEAR ANALYSIS OF R/C SHEAR WALL

纤维单元以其单元自身的优点被广泛使用于梁柱构件的非线性分析中,对于剪力墙构件,由于纤维单元采用平截面假定,忽略单元的截面剪切变形,会造成很大的误差。该文对基于力插值的纤维单元进行修正,将其引入到剪力墙构件的分析中,介绍了考虑截面剪切变形的修正基于力插值纤维单元(MFBFE)和材料单轴本构的形成,给出单元在OpenSees平台上的开发过程,特别是迭代过程中的非线性分析算法和OpenSees框架下单元和材料本构的实现方式。通过实例分析对MFBFE的应用效果进行检验,得到了两组6片剪力墙的水平低周往复模拟数据,与试验结果对比,可以认为试件模拟结果中各项抗震性能指标均与试验值相接近,单元分析精度较高。

A modified force-based fibre element(MFBFE) is popular for the nonlinear analysis of beams and columns in a reinforced concrete structure. However, for a shear wall, a fibre element can take inaccuracy for the reason that one of its basic plane-section assumption. In order to use a fibre element to analyze a shear wall, a force-based fibre element is modified. The key technique of the implement process is discussed, especially the formulation of a modified force-based fibre element and the uniaxial constitution of the material. The whole implement process in OpenSees contains nonlinear solution algorithm in the interactive process and the realizing way of elements and material constitution relations is presented. The numerical analysis for a low-cyclic loading test of two groups of six shear wall specimens based on an MFBFE element is done to test the new process. The analysis results show that the MFBFE element can perform well with kinds of aseismic behavior indexes, including the initial stiffness, yield strength, ultimate strength, unloading stiffness, residual displacement, ductility and energy dissipation. It is concluded that the analysis precision of MFBFE can be accurate enough for shear wall analysis.