组合构件纤维模型的建模策略——单元划分和截面离散

MODELING STRATEGIES OF FIBER MODELS FOR COMPOSITE STRUCTURAL MEMBERS: ELEMENT MESH AND SECTION DISCRETIZATION

为兼顾纤维模型的精度、效率和数值稳定性,对纤维模型用于组合构件非线性分析时的建模策略进行参数分析,重点研究了合理单元划分方式和高效截面离散模式。当采用一点积分的基于位移的标准有限单元纤维模型时,合理的单元网格尺寸建议选为跨中集中加载简支构件等效塑性铰长度的一半,从而可准确模拟塑性铰区的曲率突变特征,并有效克服应变软化导致的病态网格依赖问题。当采用纤维中点积分准则以及纤维均匀分布模式时,分别采用8根、24根、32根纤维离散组合梁、圆形钢管混凝土及矩形钢管混凝土截面,就能足够准确地模拟组合构件在复杂往复荷载作用下的滞回特性。

This paper presented parametric studies on modeling strategies of a fiber beam-column model for nonlinear analysis of composite structural members to balance the accuracy, efficiency and numerical stability of the fiber model. The rational element mesh and the efficient section discretization scheme were two main focuses. It was recommended the rational element mesh size be selected to be about half of the mid-span equivalent plastic hinge length of a simply supported member when the standard displacement-based fiber element with one-point integration scheme was adopted. Such mesh schemes can accurately capture the sharp jump of the curvature at the plastic hinge region, and can also effectively overcome the pathological mesh-sensitivity problem caused by strain softening. In addition, the midpoint integration rule with 8, 24 and 32 uniformly distributed fibers for composite beam, circular concrete filled steel tubular（CFST） and rectangular CFST sections, respectively, offered sufficient accuracy for the hysteretic behavior of composite members under complex cyclic load histories.