地震动输入界面的选取对深软场地地震效应的影响
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摘要
以天津和上海两个典型的深厚软弱场地为研究背景,探讨了地震动输入界面对场地地表地震动参数的影响。对于场地1(天津)和场地2(上海),分别选择7个和8个剪切波速(vs)大小不同的土层位置作为地震动输入界面,并选用Taft、Northridge地震加速度记录和南京人工波作为输入地震动,将Taft波、Northridge波和南京人工波的加速度峰值水平调整为0.35m/s2、0.70m/s2和0.98m/s2,用SHAKE91程序对这两个场地进行了不同的地震动输入界面、输入地震波和峰值加速度水平的128种组合的场地地震反应分析。与从假想基岩面(vs500m/s)输入地震动的结果(假想的实际值)相比,可得到如下结论(1)随着地震动输入界面深度(剪切波速)的增加,场地地表加速度反应谱逐渐地向实际值接近;(2)地震动输入界面的深度相同时,地震动加速度峰值水平越高,两者的加速度反应谱谱值的相对差异也越大;(3)对于一般建筑物,可以把剪切波速为400m/s左右的土层作为地震动输入界面;对于中长周期的建筑物,则应慎重选择地震动输入界面,最好选取vs500m/s2的土层或基岩面作为地震动输入界面。
Earthquake effects of two typical deep soft sites selected from Tianjing (site NO.1) and Shanghai (site NO.2) cities are studied when the vertical inputing earthquake waves are located in different depth of sites. As far as the shear wave velocity of soil layers is concerned, 7 kinds of soil layers in site NO.1 and 8 soil layers in site NO.2 are selected as the vertical inputing interfaces of earthquake waves. Two acceleration waves recorded during Taft earthquake and Northbridge earthquake are selected, and the peak values of two waves are adjusted to be ~0.35 m/s2、 0.70m/s2 and 0.98 m/s2, respectively. According to different earthquake wave and its peak value, inputing interfaces of waves, 128 Kinds of artificial sites are constituted, the earthquake response of sites are calculated by SHAKE91 program. The results are compared to those of sites when the vertical inputing interfaces of earthquake waves are located in bedrock in which shear wave velocity is larger than 500 m/s. It is observed that: (1) The earthquake acceleration spectra of the sites in ground surface approach to its actual spectra more and more with the inputing interfaces of earthquake waves becoming deeper. (2) When the depths of inputing interface of earthquake waves are same, the acceleration spectra of the sites in ground surface depart from its actual spectra more and more with the peak acceleration values of inputing waves becoming larger. (3) For general buildings, the soil layers in which shear wave velocity is more than 400m/s can be assumed to be the interfaces of bedrock. For the buildings of modesate and long natural periods, the soil layers in which shear velocity is more than 500m/s can be assumed to be the interfaces of bedrock.
Earthquake effects of two typical deep soft sites selected from Tianjing (site NO.1) and Shanghai (site NO.2) cities are studied when the vertical inputing earthquake waves are located in different depth of sites. As far as the shear wave velocity of soil layers is concerned, 7 kinds of soil layers in site NO.1 and 8 soil layers in site NO.2 are selected as the vertical inputing interfaces of earthquake waves. Two acceleration waves recorded during Taft earthquake and Northbridge earthquake are selected, and the peak values of two waves are adjusted to be ~0.35 m/s2、 0.70m/s2 and 0.98 m/s2, respectively. According to different earthquake wave and its peak value, inputing interfaces of waves, 128 Kinds of artificial sites are constituted, the earthquake response of sites are calculated by SHAKE91 program. The results are compared to those of sites when the vertical inputing interfaces of earthquake waves are located in bedrock in which shear wave velocity is larger than 500 m/s. It is observed that: (1) The earthquake acceleration spectra of the sites in ground surface approach to its actual spectra more and more with the inputing interfaces of earthquake waves becoming deeper. (2) When the depths of inputing interface of earthquake waves are same, the acceleration spectra of the sites in ground surface depart from its actual spectra more and more with the peak acceleration values of inputing waves becoming larger. (3) For general buildings, the soil layers in which shear wave velocity is more than 400m/s can be assumed to be the interfaces of bedrock. For the buildings of modesate and long natural periods, the soil layers in which shear velocity is more than 500m/s can be assumed to be the interfaces of bedrock.
引文
[1]陈国兴,谢君斐,张克绪.土的动模量和阻尼比的经验估计[J].地震工程与工程振动,1995,15(1):15-25.
[2]陈国兴,朱定华,何启智.GZZ—1型自振柱试验机研制与性能试验[J].地震工程与工程振动,2003,23(1):110-114.
[3]黄玉龙,郭迅,袁一凡,等.软泥夹层对香港软土场地地震反应的影响[J].自然灾害学报,2000,9(1):109-116.
[4]杨国强.秦皇岛市区场地抗震性能评价[A].第五届全国地震工程学术会议论文[C].北京,1998,327-335.
[5]周健,胡晓燕,陆洪.地震作用下上海软土隧道的动力反应分析[A].第五届全国土动力学学术会议论文集[C].大连,1998,278-283.
[6]陈国兴,杨伟林,严新育.南京河西地区软土场地地震动参数研究[J].南京工业大学学报,2002,(1):35-40.
[7]韦晓,袁一凡.土层地震反应分析中输入界面的选取[A].第四届全国地震工程会议论文集[C].哈尔滨,1994.
[2]陈国兴,朱定华,何启智.GZZ—1型自振柱试验机研制与性能试验[J].地震工程与工程振动,2003,23(1):110-114.
[3]黄玉龙,郭迅,袁一凡,等.软泥夹层对香港软土场地地震反应的影响[J].自然灾害学报,2000,9(1):109-116.
[4]杨国强.秦皇岛市区场地抗震性能评价[A].第五届全国地震工程学术会议论文[C].北京,1998,327-335.
[5]周健,胡晓燕,陆洪.地震作用下上海软土隧道的动力反应分析[A].第五届全国土动力学学术会议论文集[C].大连,1998,278-283.
[6]陈国兴,杨伟林,严新育.南京河西地区软土场地地震动参数研究[J].南京工业大学学报,2002,(1):35-40.
[7]韦晓,袁一凡.土层地震反应分析中输入界面的选取[A].第四届全国地震工程会议论文集[C].哈尔滨,1994.
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