固定阻尼系数对结构弹塑性时程分析的误差影响

Effect of Fixed Damping Coefficients on Structural Elastoplastic Dynamic Analysis

结构在强震作用下的弹塑性响应分析广泛采用瑞利比例阻尼,其阻尼系数是根据系统的质量和初始刚度确定的,这种固定的阻尼系数设置会因结构弹塑性响应时的刚度软化而导致模态阻尼比的增大,造成分析结果的偏差。通过对单自由度双线性模型的塑性响应分析,考察固定阻尼比和固定阻尼系数两种情况对延性需求的影响,以及粘滞阻尼和塑性变形的耗能差异。研究表明,对于内阻尼产生的模态阻尼比因其数值较小,即使结构出现严重的弹塑性响应,放大的计算阻尼比也不致耗散过多的能量而降低结构延性需求,弹塑性时程分析时采用固定阻尼系数能满足工程计算的精度要求。

In analysis of structural responses to strong ground motion, Rayleigh damping model is widely employed and its coefficients are defined by mass and initial structural stiffness, in consequence, which unconsciously induces an increment of modal damping ratio because of structural stiffness degradation with elastoplastic deformation. Deducting the elastoplastic responses of one single degree of freedom system with bilinear model, this paper investigates the ductility demand and energy dissipation for viscous damping and plastic deformation in the condition of fixed damping coefficients compared with fixed damping ratio. The results show that the increased artificial damping ratio does not dissipate a large number of energy and reduce greatly ductility demand even if structural system experiences severe plastic deformation because of little damping ratio due to interior damping sources, and the elastoplastic dynamic analysis using fixed damping coefficients could hold required accuracy in the view of engineering.