Effects of Ground Motions on Seismic Response of Structures

从最近的重大地震中得到的一些教训表明，需要对尚未详细研究的设计领域进行进一步研究。2004年印度尼西亚苏门答腊（里氏9.1级）、2010年智利Maule（里氏8.8级）和2011年日本东北（里氏9.0级）的俯冲地震都是有记录以来最大的地震。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）估计，该地区9级地震造成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造成的，其余则是由于海啸、火灾、液化和山体滑坡造成的。因此，现在有强烈的动机减少由于地面震动造成的经济损失。几年来，申请人和他的研究小组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，以及现场试验和监测仪器结构。拟议的研究将涉及三个与地震期间结构反应的理解具有重要相关性的主题。这反过来将有助于降低加拿大的地震风险：1)地震期间建筑物的土-基础-结构相互作用（SFSI）具有几个方面的特征，包括自由场运动和基础运动之间的变化。目前进行的分析研究表明，当系统周期接近输入运动的主导周期时，会发生放大。当这两个周期相距甚远时，平板上的运动相对于磁场就减小了。应重新审查守则建议的基础，因为它似乎与实地数据和分析结果的结论相矛盾。2)脉冲状近断层地震动可以发生在离致病断层很近的地方。在这种情况下，考虑基础体系的灵活性是非常重要的。本研究的目的是研究脉冲型近地断层对结构的非线性响应。俯冲地震动对加拿大西部很重要，其对构造响应的影响需要详细研究。本研究旨在通过对这类地震中记录的地面运动进行全面分析，从而深入了解俯冲地震。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将被研究。迄今为止，大多数量化建筑物和桥梁反应和安全的研究都集中在地壳，加利福尼亚型地震动上。俯冲地震震源和衰减的鲜明地质特征，使得俯冲地震的地震动与地壳地震动相比，具有不同的持续时间和频率内容。这项研究的目标是量化这些地面运动对建筑物和桥梁反应的影响，并开发可被执业工程师用于设计或改造可能遭受这种地面震动的结构的信息。将拟订将俯冲地震动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的建议。

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.