钢筋混凝土框架结构非线性全过程分析的一种新方法

在极限承载力附近的计算发散问题一直是困扰混凝土结构非线性全过程分析的关键问题,现有的迭代方法中只有弧长法被认为是最为有效的迭代方法,但由于混凝土结构具有高度的材料非线性,弧长法的稳定性难以保证。为此本文提出了一种新的方法———虚拟单元法,该方法在原结构上添加虚拟单元,虚拟单元的刚度系数在每个加载步中均保持为常数,该法在保证结构比例加载的前提下,可以有效改善结构刚度矩阵的性能,为得到结构非线性全过程分析曲线,特别是下降段部分提供了可能。本文采用虚拟单元法,通过自编的程序进行了实例分析,计算中,选取一榀混凝土框架进行模拟计算,杆件采用纤维模型,分析结果与ANSYS计算结果进行了对比,表明了该法的有效性,并对建立在纤维模型基础上的结构极限荷载进行了一定的探讨。

A new method in full-range nonlinear analysis of RC frame

Numerical divergence near ultimate bearing capacity is the key problem in the full-range nonlinear analysis of RC structure.In the current theory,the arc-length method is considered to be the most effective method in present,but poor in stability especially for the RC structure,which is a kind of highly nonlinear material.A new method(using) virtual element is presented in this paper.The new method adds a new element which keeps elastic in each load step to the present structure for better performance of the new stiffness matrix,which ensures a proportional load and give a possible channel to get the soft stage in full-range nonlinear analysis.The new method is used in a program with the fiber model to make the full-range nonlinear analysis of RC frames.The result is verified by that of the program ANSYS.And some discussions are made about the limit load of the structure on the basis of the fiber model.