A Comprehensive Approach for Incorporating the Effects of Near-Fault Directivity into Design Criteria

由方向性效应引起的脉冲状近断层地震动是一类特殊的地面运动，其特征在地震性能评估中尤其具有挑战性。这些运动在运动的速度时间历史中包含一个“脉冲”，通常在垂直于断层破裂的方向上，并且通常发生在地震破裂已经向场地传播的断层附近的位置。了解这些地面运动的影响是很重要的，因为已经观察到它们会对结构造成严重破坏。通过在地面运动处理、地震危险性分析和结构响应研究方面的一系列创新，这项研究将产生一个新的全面框架，以理解和解释方向性效应。将开发一种用于识别方向性脉冲的自动信号处理方案，并将其作为开放源代码软件程序来实施；该程序的初步结果显示，在将用户判断从地震动分类中去掉方面具有很大的前景。当与脉冲式地震动对结构响应的参数研究相结合时，这种分析将形成一套新的近断层设计规范系数和可能经历地震动方向性效应的结构的地震动选择指南。智力上的优点：近断层地震动的潜在风险早已为人所知，而考虑这种风险的方法也已经讨论了很多年。该项目将产生识别速度脉冲的新方法，在地震危险性分析中考虑方向性，并预测这些脉冲对结构响应的影响。将这些量化工具结合在一起将有助于工程师和地震学家从根本上了解这种现象的影响，并将使业主更有信心地相信，他们的结构是使用Rational工具设计的，可以考虑到地面震动的所有影响。虽然这种近断层问题的重要性得到了广泛的认识，但迄今为止还没有人尝试对地震动分类、危险分析和结构响应问题进行全面的处理。更广泛的影响：了解这些地面运动的影响，并以设计指南的形式实施这些发现，最终将导致更安全、更高效和更经济的设计。因此，这项工作的发现将解决一个主要的安全问题，该问题影响到在地震活动断层附近生活和工作的所有人使用的结构的安全性。该项目将促进正在进行的涉及本科生和代表人数不足的少数群体的外联活动。还将通过开放源码软件工具、发表期刊文章、会议报告和一个包含教育资源的项目网站，将发展出的知识和方法纳入教育。

Pulse-like near-fault ground motions resulting from directivity effects are a special class of ground motions that are particularly challenging to characterize for seismic performance assessment. These motions contain a "pulse" in the velocity time history of the motion, typically in the direction perpendicular to the fault rupture, and generally occur at locations near the fault where the earthquake rupture has propagated towards the site. It is important to understand the effects of these ground motions, because they have been observed to cause severe damage to structures. Through a series of innovations in ground motion processing, seismic hazard analysis, and structural response studies, the research will produce a new comprehensive framework to understand and account for directivity effects. An automated signal processing scheme for identifying directivity pulses will be developed and implemented as an open-source software program; preliminary results from the procedure show great promise in removing user judgment from ground motion classification. When coupled with parametric studies of structural response from pulse-like ground motions, this analysis will form the basis for a new set of near-fault design code factors and ground motion selection guidelines for structures that might experience ground motion directivity effects.Intellectual Merit: The potential risk from near-fault ground motions has long been known, and methods to account for this risk have been discussed for many years. The project will result in new ways of identifying velocity pulses, accounting for directivity in seismic hazard analysis, and predicting the effects of these pulses on structural response. Bringing these quantitative tools together will help engineers and seismologists more fundamentally understand the effect of this phenomenon, and will give owners greater confidence that their structure has been designed using rational tools to account for all effects of ground shaking. While the importance of this near-fault problem is widely recognized, no holistic treatment of the ground motion classification, hazard analysis, and structural response problems has been attempted to date. Broader Impact: Understanding the effects of these ground motions, and implementing these findings in the form of design guidelines, will ultimately lead to safer, more efficient and more economical designs. Thus the findings from this work will address a major safety concern that affects the safety of structures used by all people living and working near active seismic faults. The project will foster ongoing outreach activities involving undergraduates and underrepresented minorities. Developed knowledge and approaches will also be integrated into education through open-source software tools and publication of journal articles, conference presentations, and a project website containing educational resources.