Effects of Ground Motions on Seismic Response of Structures

最近发生的一些重大地震的教训表明，需要对尚未详细研究的设计领域进行进一步研究。2004年发生在印度尼西亚苏门答腊（Mw9.1）、2010年发生在智利马乌莱（Mw8.8）和2011年发生在日本东北（Mw9.0）的俯冲地震是有记录以来最大的地震之一。加拿大西部和美国太平洋西北部的卡斯卡迪亚俯冲带也有可能产生非常大的地震。加拿大保险局最近委托进行的一项研究（Air Worldwide，2013年）估计，该地区9级地震的经济损失可能高达750亿美元，其中约490亿美元是由于地面震动，其余是由于海啸，火灾，液化和山体滑坡影响。因此，现在有强烈的动机来减少由于地面震动造成的经济损失。几年来，申请人及其研究团队一直在研究不同类型地震的地面运动如何影响结构的地震反应。这些研究包括分析研究、振动台和循环试验以及现场测试和监测仪器结构。拟议的研究将解决三个主题的重大相关的理解在地震中的结构反应。这反过来又将有助于减少加拿大的地震风险：1）地震时建筑物中的土壤-基础-结构相互作用（SFSI）具有几个方面的特征，包括自由场和基础运动之间的变化。到目前为止进行的分析研究表明，放大发生时，系统的周期是接近的输入运动的主导周期。当这两个周期相距很远时，板的运动相对于场减小。规范建议的依据似乎与现场数据和分析结果相矛盾，因此应重新审查。2)脉冲状的近断层地面运动可以发生在非常接近于一个成因断层的场地上。在这种情况下，考虑基础系统的灵活性非常重要。本研究旨在探讨结构在脉冲状近地断层作用下之非线性反应。3)俯冲地面运动是加拿大西部的重要，其对结构响应的影响需要详细研究。这项研究的目的是提供一个深刻的洞察俯冲地震进行了全面的分析，记录在这种类型的事件的地面运动。将研究地震动的持续时间和长周期分量对结构的线性和非线性响应的影响。迄今为止，大多数量化建筑物和桥梁响应和安全性的研究都集中在地壳，加利福尼亚型地面运动。俯冲地震震源和衰减的独特地质特征，使俯冲地震的地面运动与地壳地面运动相比具有不同的持续时间和频率成分。本研究的目标是量化这些地面运动对建筑物和桥梁响应的影响，并开发可供执业工程师设计或改造可能受到这种类型地面震动的结构的信息。将提出建议，将俯冲地面运动的影响纳入加拿大国家建筑规范和加拿大公路和桥梁设计规范。

Some of the lessons from recent significant earthquakes have shown the need for further research on design areas that have not been studied in detail. The subduction earthquakes in Sumatra, Indonesia (Mw 9.1) in 2004, Maule, Chile (Mw 8.8) in 2010, and Tohoku, Japan (Mw 9.0) in 2011 are some of the largest earthquakes ever recorded. The Cascadia subduction zone in Western Canada and the Pacific Northwest of the U.S. has the potential of generating very large earthquakes, as well. A recent study commissioned by the Insurance Bureau of Canada (Air Worldwide, 2013) estimate that the economic losses from a magnitude 9 in the region could be as high at 75 billion dollars, of which about 49 billion dollars would be due to ground shaking and the rest due to tsunami, fire-following, and liquefaction and landslides effects. So there is now strong motivation to reduce economic losses due to ground shaking. For several years, the applicant and his research team have been studying how the ground motions from different types of earthquakes affect the seismic response of structures. These studies included analytical studies, shake table and cyclic tests, and field testing and monitoring of instrumented structures. The proposed research will address three topics of significant relevance to the understanding of structural response during earthquakes. This, in turn, will contribute to the reduction of seismic risk in Canada: 1) Soil-foundation-structure interaction (SFSI) in buildings during earthquakes is characterized by several aspects including the variation between the free-field and foundation motions. The analytical studies conducted so far show that amplification occurs when the system period is close to the dominant period of the input motion. When these two periods are far apart, the motions at the slab are reduced with respect to the field. The basis of code recommendation should be re-examined in light of the fact that it appears in contradiction to the findings from field data and analytical results. 2) Pulse-like near fault ground motions can occur on sites in close proximity to a causative fault. In such cases consideration of flexibility of the foundation system is very important. The purpose of this research is to study the nonlinear response of structures to pulse-like near ground fault. 3) Subduction ground motions are important for Western Canada and their effects on the response of structures needs to be investigated in detail. This study is intended to provide a deep insight into subduction earthquakes by carrying out a comprehensive analysis of ground motions recorded during this type of event. The effects of duration and long period components of the ground motions on the linear and nonlinear response of structures will be investigated. To date, most of the research quantifying building and bridge response and safety has focused on crustal, California-type ground motions. The distinct geologic characteristics of subduction earthquake sources and attenuation, cause ground motions from subduction earthquakes to have different duration and frequency content when compared to crustal ground motions. The goal of this research is to quantify the impact of these ground motions on the response of buildings and bridges and to develop information that can be used by practicing engineers to design, or retrofit, structures that may be subjected to this type of ground shaking. Recommendations for incorporation of subduction ground motion effects on the National Building Code of Canada, and the Canadian Highway and Bridge Design Code will be developed.