以性能指标为控制变量的强度折减因子

发展以性能指标为控制变量的强度折减因子是基于性能抗震设计方法的有效途径。本文以刚度退化(SD)滞回模型的SDOF体系为对象,利用改进的Park-Ang双参数破坏准则,根据所收集到的三类场地的214条近断层地震动记录为基础,首先从数值分析的角度检验以延性为指标的强度折减因子的可靠性,表明以单调变形延性系数为基础的强度折减方法难以有效考虑累积效应,导致过高的结构总体损伤而偏于不安全。在定义基于确定性能指标的强度折减因子的基础上,通过自编程序以近震记录分组下结构响应的统计结果进行回归分析,建立确定性能指标下的强度折减因子表达式,按三种场地类别用回归方法确定5%阻尼条件下的参数取值并进行验证,可作为桥梁结构基于性能的抗震设计方法的必要工具。

Strength Reduction Factor Model with Performance Index as Control Parameter

Application of the strength reduction factor with the performance index as the control variable is an effective way to conduct performance-based aseismic design.A world-wide ensemble of 214 records within 15 km of fault projection distance was selected as the data base.An improved dual-parameter Park-Ang damage assessment model was introduced to assess the actual damage state of the stiffness degradation(SD) SDOF system designed on the basis of the constant-ductile strength reduction factor.It is concluded that such a traditional method with displacement ductility as the single index can not effectively cover the effect of cumulative damages from stiffness degradation of RC structure,thus being unsafe as the result of excessive overall damages.Therefore the concept of the strength reduction factor with the constant-performance-target was defined in this paper.A large number of working cases for the stiffness degradation SDOF system were calculated by the self-writing computation program.A regression model under the 5% damping ratio was extracted,which is adapted to three soil types.The proposed strength reduction method constitutes the essential means for performance-based aseismic design of bridge structures.