考虑震源和场地特征的近断层地区竖向地震动合成研究

STUDY ON SYNTHESIS METHOD OF VERTICAL GROUND MOTIONS FOR NEAR-FAULT REGIONS CONSIDERING THE CHARACTERISTICS OF SOURCE AND SITE CONDITION

近断层高风险条件下的结构安全性日渐受到重视,该文建立了一种考虑震源特性的近断层竖向地震动人工合成方法。建立了以断层类型、震级、断层破裂顶部埋深、断层距、场地剪切波速为参量的地震动预测模型,考虑模型参数相关性并保留其变异性,使模拟的地震动可反映实际近断层地震动的最不利效应(强度与频率非平稳、模型参数的变异性);绘制残差图分析了统计效果,验证了回归所得参数的显著性;对比分析了所提模型与前人成果的模型参数差异,以及人工合成地震动与实际地震动时程、反应谱的吻合程度,验证了所建立的方法的准确性、合理性。该文所提方法参数少(仅7个参数,可考虑强度和频率非平稳性);与乘系数法相比,该文方法模拟的地震动特性更符合竖向记录统计规律;可与目前已有的水平分量地震动模拟方法联合构成三维近断层地震动模拟方法,用于地震风险等级高的结构抗震设防分析与设计,也可在匮乏实际地震动记录的地震风险相近地段替代使用。

The safety of structures under high risk conditions in near-faults regions has been paid more and more attention. A synthetic method of near-faults vertical ground motions considering source characteristics has been established. A mathematical model is established, which takes fault type, magnitude, depth of rupture top, fault distance and shear wave velocity as variables, and the correlation matrix of model parameters is given. The simulated ground motion reflects the most adverse effect characteristics of actual near-fault ground motions(nonstationary intensity and frequency, variability of source parameters). The significance of regression parameters is verified by statistical parameters and residual plots. The accuracy and rationality of the proposed method are verified by comparing the difference between the model parameters proposed in this study and previous results, as well as the consistence degree of the time history and response spectrum between the simulated ground motion and the actual ground motion. Compared with the trigonometric series method, the proposed synthesis method has fewer parameters, and the intensity and frequency nonstationary can be considered with only 7 parameters. Compared with the multiplicative coefficient method, the frequency characteristics of ground motion simulated by the proposed method match the vertical component records. It can be combined with the horizontal component ground motion simulation method proposed previously to form a three-dimensional ground motion simulation method, which can be used for structural analysis and design of structures with important fortification requirements, and can also be used for areas lacking actual ground motion records.