中文摘要：

概率地震需求分析的目标是估计结构在不同地面运动强度水平下的响应，结构响应的不确定性对采用的地面运动强度度量参数有着很强的依赖．因而，需要比较所采用的地面运动强度度量参数的有效性．这里推荐了一个新的采用向量地面运动强度度量参数来估计结构需求的方法，并把这个地面运动强度度量参数应用于一些不同周期和不同强度折减系数的单自由度结构系统．统计结果表明，推荐的地面运动强度度量参数可以有效地减小估计单自由度结构系统最大变形延性需求时的离散性，而且减少了计算分析工作量．

英文摘要：

The aim of probability seismic demand analysis is estimation of the demand on a structure by earthquakes of different intensities. The uncertainties associated with these estimates are highly dependent on the variable adopted as intensity measure（IM）. It is required to compare the efficiency of adopted IM. In this paper a new vector IM for predicting the demand of structures is proposed. The proposed IM has been tested by application to several SDOF systems with different periods and different strength reduction factors. It is shown by statistical results that the proposed IM has decreased the dispersion of the peak SDOF displacement ductility demand conditioned on IM, and reduced computational effort.