基于位移目标的性态谱

达到位移目标时确定结构的地震需求, 是性能抗震设计的一个重要课题。研究了结构位移目标, 确定了位移性能目标参数, 推导了单自由度结构体系的位移性能目标与周期的关系。将1085 条地震波, 输入到不同周期的单自由度弹塑性动力微分方程, 调整地震动, 反复迭代, 达到位移目标, 获得地震需求与周期、位移目标之间的函数关系, 建立了具有统计意义的三维坐标下的性态谱, 并拟合了性态谱的计算公式。研究表明:性态谱是反映不同位移目标下结构地震需求的一种有效方法。性态谱曲线随着结构周期的增大明显减小, 并随着位移目标的增大, 逐渐增大。性态谱曲线已无平台段, 与场地的共振效应消失, 场地对性态谱的影响总体不明显。性态谱可快速地、简便易行地预测达到不同性能目标时结构的地震需求, 拟合的性态谱计算公式可进行结构抗震性能评估。

DISPLACEMENT-OBJECTIVE-BASED SEISMIC PERFORMANCE SPECTRA

How to determine the structural seismic demands up to the displacement-objective is one of the key tasks for performance-based seismic design. The displacement objectives are studied, the displacement objective parameters are determined and the relations between displacement-objectives and periods of single-degree-of-freedom systems are derived. The displacements of different periods are obtained by dynamic elastic-plastic differential equations of single-degree-of-freedom systems under 1085 ground motions. The displacements are adjusted up to the displacement-objectives by zooming ground motions. This paper acquires the functional relations among seismic demands, structural period and performance objectives, establishes the statistical performance spectra under a three-dimensional coordinate system and fits the empirical formulas of performance spectra. The results show that the performance spectra function is an effective method, which determine the seismic demands under different performance objectives. The performance spectra curves decrease with the increasing periods obviously and increase with the increasing performance objectives gradually. The performance spectra have no horizontal section, the resonance effect of the sites disappears and the sites do not obviously affect the performance spectra. The seismic demand inferences up to the performance objectives and the seismic performance assessments can use the fitting formulas.