Verification of Site Response Analysis Techniques for Soft Clay Sites Using Data from the Loma Prieta Earthquake

该项目是美国国家科学基金会/美国地质勘探局国家减少地震灾害计划(NEHRP)倡议的一部分，目的是调查1989年10月17日洛马普里塔地震的影响。局部软土条件对地震运动的影响往往是非常重要的。初步信息显示，洛马普里塔地震尤其如此。自信地预测这些影响的能力是结构有效设计的重要组成部分，在确定抗震规范规定的准确性时，以及估计地震造成的损失。该项目的目标是(1)确定使用等效线性方法预测软的非线性粘土剖面的加速度水平和反应谱形状的能力，以及(2)根据记录和计算的响应，使用损伤潜力指数法评估现有软土场地设计规范的充分性。该程序的具体目标是：(1)获取软土场地上现有的强地震动记录，以确定具有代表性的谱形状；(2)将该谱与Seed和Sun(1989)、加利福尼亚结构工程师协会(1988)和Borcherdt(1976)提出的谱形状进行了比较；(3)利用记录的岩层运动作为输入值，对三个已预测频谱形状的软粘土场地进行分析；(4)将使用计算机程序SHAKE计算的地震动与记录值进行比较，以评估该程序的准确性；(5)分析另外三个地震破坏严重或有记录运动的粘土场地，以提供额外的验证；以及(6)利用测量和计算的响应运动计算损伤势能指数。

This project is part of the NSF/USGS initiative within the National Earthquake Hazard Reduction Program (NEHRP) to investigate the effects of the Loma Prieta earthquake of 17 October 1989. The influence of local soft soil conditions on earthquake motions is often very dominant. Preliminary information suggests that this is particularly true for the Loma Prieta earthquake. The ability to confidently predict these effects is an important component in the effective design of structures, in determining the accuracy of seismic code provisions, and in estimating damage due to an earthquake. The goals of the project are (1) to determine the ability to predict the acceleration levels and response spectrum shapes of soft non-linear clay profiles using equivalent linear methods, and (2) to assess the adequacy of existing design codes for soft clay sites, using the damage potential index approach, based on the recorded and computed response. The specific objectives of this program are: (1) To acquire the available strong ground motion records on soft clay sites so as to determine a representative spectrum shape; (2) Compare this spectrum with spectrum shapes proposed by Seed and Sun (1989), the Structural Engineers Association of California (1988) and Borcherdt (1976); (3) Analyze three soft clay sites for which spectrum shapes have been predicted, using recorded rock motions as input values; (4) Compare ground motions computed using the computer program SHAKE with recorded values, in order to assess the accuracy of this program; (5) Analyze three additional clay sites for which the earthquake damage was heavy or where recorded motions are available, in order to provide additional verification; and (6) Calculate the damage potential index using the measured and computed response motions.