基于位移的高桩码头抗震设计等效阻尼比计算公式

摘要

现行高桩码头抗震设计规范中采用的等效阻尼比计算公式并非专门针对码头,无法反映其结构特点,也未考虑土体对体系阻尼的贡献,故通过对码头进行低周往复Pushover分析,研究了考虑桩土相互作用的码头滞回特性,确定了码头等效阻尼比的计算公式.为验证所提出的计算公式的准确性和适用性,采用60条地震波对2个高桩码头进行了非线性时程分析,并将采用替代结构法得到的位移需求与时程分析得到的位移需求进行了对比.研究表明,Pivot滞回模型可很好地反映混凝土桩码头的滞回和承载力退化特性,而Masing准则可较好地模拟钢管桩码头的滞回特性;以非线性时程分析结果为判定准则,采用所提出的等效阻尼比计算公式得到的位移需求精度高于采用规范中计算公式得到的位移需求精度.%In current seismic design codes for pile-supported wharves,the equivalent damping ratio equations are not aimed at wharf structures,which can not represent their structural characteristics and the contribution of soil to the damping of system.Consequently,the hysteresis characteristics of wharves with pile-soil interaction are investigated by low-period cyclic Pushover analyses,resulting in the appearance of new equivalent damping ratio equations for wharves.In order to validate the applicability and accuracy of the proposed equations,two cases' studies are conducted by comparing the demand displacements obtained from time history analyses under 60 ground motion records to those obtained by using substitute structure method with various equivalent damping ratio equations. The results indicate that Pivot hysteretic model can represent hysteresis characteristics and strength degradation of concrete pile-supported wharves,and the Masing rule can be used to simulate the hysteresis response for steel pipe pile-supported wharves. It is also shown that the accuracy determined by using the proposed equations is better than that determined by using the equations in current codes according to nonlinear time history analyses.