海域地震动长周期特性及其强度指标研究

Long-period characteristics of offshore ground motion and its and intensity index

为了分析海域地震动的长周期特性。选取893条三分量海域地震动记录,识别出其中长周期特性明显的水平和竖向海域地震动,比较了海域长周期地震动的动力放大系数谱和抗震设计规范谱的差异,研究了海域地震动强度指标PGA(Peak Ground Acceleration),PGV(Peak Ground Velocity),PGD(Peak Ground Displacement)与不同强度折减系数下的弹塑性单自由度体系的最大变形需求间的相关性。分析结果表明:由浅源远场强震(震源深度小于45 km,震中距大于120 km,且矩震级大于6.2)产生的海域地震动的长周期特性十分突出,其动力放大系数谱在长周期段(2~10 s)明显超过了抗震设计规范谱的取值,且竖向地震动的长周期特性比水平向地震动更显著;PGD和单自由度体系的最大变形需求的相关性在长周期段最好,因此建议选用PGD作为海域远场长周期地震动的抗震分析强度指标。

In order to analyze long-period characteristics of offshore ground motion,8933-component offshore ground motion records were selected,and horizontal and vertical offshore ground motions with obvious long-period characteristics were identified.The dynamic amplification factor spectrum of long-period offshore ground motion was compared with the aseismic design code spectrum,and correlations among offshore ground motion intensity indexes PGA,PGV,PGD and the maximum deformation demands of elastoplastic single-DOF systems with various strength reduction factors were studied.The analysis results showed that long-period characteristics of offshore ground motion caused by shallow source far-field strong earthquakes with focal depth less than 45 km,epicentral distance larger than 120 km and moment magnitude larger than 6.2 is very prominent,their dynamic amplification factor spectra in the long period range of 2-10 s are obviously exceed values of the aseismic design code spectrum,and long-period characteristics of vertical ground motion are more significant than those of horizontal one;the correlation between PGD and the maximum deformation demands of single-DOF systems is best in the long period range,so PGD is suggested to be the aseismic analysis intensity index for offshore far-filed long-period ground motion.