基于曲率延性的弯曲型结构地震作用折减系数

Curvature ductility-based seismic force reduction factor of flexure-type structure

采用基于曲率延性的非线性动力分析方法,研究弯曲型结构的地震作用折减系数.引入地震作用名义作用高度,在多自由度体系的基底剪力和基底弯矩间建立起有效联系.为了保留谱线峰值特征,采用双特征周期对地震作用折减系数谱进行标准化处理.通过300 000余组非线性动力分析,研究结构自振周期、曲率延性、刚度沿结构高度分布和上层结构延性开展等因素对弯曲型结构地震作用折减系数的影响.采用3种不同工况,分析二阶振型对地震作用折减系数的影响,提出弯曲型地震作用折减系数及二阶振型影响系数的简化计算公式,建立曲率延性与位移延性的定量相关关系.

A curvature ductility-based nonlinear dynamic analysis procedure was developed to analyze the seismic force reduction factor of flexure-type building.A nominal height of base shear was defined to provide an effective link between base shear and base moment for multi-story flexure-type building.Two site-specific characteristic periods were utilized to normalize the abscissa of the reduction factor spectra to retain their peak features.The influence of structural fundamental period,curvature ductility,stiffness distribution over structural height and upper-story inelasticity etc.on the reduction factor was analyzed via over 300,000 nonlinear analyses.The effect of the second vibration mode on the reduction factor was analyzed by three cases.Simplified formulas for the seismic force reduction factor of flexure-type building and the corresponding modification factor due to the second vibration mode were proposed respectively for practical application. The quantitative relation between curvature ductility and drift ductility was discussed.