剪切型结构高模态效应对延性折减系数的影响

Study on the influence of multi-degree-of-freedom effect on ductility reduction factors for shear-type structure

结构延性折减系数是结构抗震设计理论中的关键参数之一。本文通过调整等效单自由度体系位移延性折减系数,研究多自由度体系(MDOF)高模态效应对延性折减系数的影响。以剪切型集中质量MDOF体系模型为分析对象,通过地震非线性动力时程分析,研究了MDOF体系因高模态延性需求集中而影响延性折减系数的规律,通过多元非线性回归分析,拟合MDOF修正系数估算模型。分析结果表明:MODF体系由于高模态效应的影响,其抗震延性折减系数比其相应的等效单自由度体系的抗震延性折减系数小,系统位移延性系数和结构基本振动周期是影响MDOF修正系数的主要因素。

Structure ductility reduction factor is one of the key parameters of structure seismic design. The influences of high mode effect on ductility reduction factors for multi-degree-of-freedom （MDOF） systems are studied by modifying ductility reduction factors for equivalent single-degree-of-freedom systems. Based on MDOF lumped-mass shear-type models, nonlinear dynamic time history analysis are performed to investigate the influence of ductility demand increase owing to high mode effect on ductility reduction factors. Based on a multiple nonlinear regression analysis, an empirical estimating model of MDOF modification factor is proposed. The results demonstrate that ductility reduction factors for MDOF systems are clearly smaller than those for SDOF systems due to the effects of high mode effects. The modification factor is mainly affected by the fundamental vibration period and displacement ductility.