Advancing Knowledge on the Performance of Seismic Collectors in Steel Building Structures

为了安全地在地震中幸存下来，从而保护其居住者、内容物、邻近财产和路人，建筑结构必须将地震期间产生的巨大力从建筑物内部向下传递到地基。地震(横向)力是由建筑物的重量水平加速产生的，因此，大多数地震力来自建筑物最重的部分，即楼板。基础的力传递路径中的一个关键结构元素是收集器，它是楼板中的特殊钢筋或楼板下方的特殊梁，它将楼板中的力收集起来，并将它们传递到主要的抗震垂直元素(框架、支撑或墙)。收藏家或收藏家联系的丧失可能是灾难性的，2011年新西兰克赖斯特彻奇地震中闭路电视大楼倒塌就是明证，那次地震造成115人死亡，这是这一事件中生命损失最大的一次，在某种程度上，1994年加利福尼亚州北岭地震中九个停车库倒塌就是明证。尽管地震采集器的性质至关重要，但没有任何研究工作，包括物理测试，专门针对采集器，而且缺乏对其地震性能的了解。理解地震收集器性能的一个挑战是地板系统本身的复杂性，即不同材料(例如，钢、金属和混凝土)的许多组件在不同高度的复杂组合，具有多种用途和不确定的受力路径。过去的建筑物抗震设计方法可能严重低估了收集器力。这种知识的缺乏不仅影响了新的建设，也影响了对高地震区现有设施的评估和翻新，特别是危重护理设施。这种情况也适用于全国范围内较老的不符合抗震要求的钢结构，在这些结构中，地震收集器不足或不存在往往是一个主要问题。为了既安全又经济的结构，无论是在现有的建筑库存中还是在新的建筑中，都需要更好地了解钢结构吸震器的性能。此外，收集器作为楼层和垂直构件之间的关键纽带的独特作用，为收集器提供了一个机会，使其不再试图“超过”地震力，而是作为一种创新的力量限制元件，保护结构免受破坏。这项研究的目标是：(1)增进对钢组合楼板系统中集热器的抗震性能、分析和设计的了解，以及(2)发展关于可靠的抗震性能和创新集热器概念的潜在好处的新知识，这些概念可以导致低损害结构设计。该项目将支持来自亚利桑那大学、加州大学圣地亚哥分校和利哈伊大学的研究人员和研究生。该项目将受益于与单独得到支持的合作者的密切合作，即新西兰的一名研究人员和实践者以及美国的一个抗震设计工程师行业小组。亚利桑那大学将开展一项外展计划，在人口统计学上确定当地的K-8学校拥有以代表性不足为主的群体的学生团体。该推广计划将针对三、四和八年级的学生，包括：(1)关于地震工程的幻灯片放映和问答环节，(2)研究生和本科生的职业指导，以及(3)实践科学和数学活动。在这个项目中，一个综合研究计划将利用NSF支持的自然灾害工程研究基础设施(NHERI)提供的实验和计算模拟能力来调查钢组合甲板结构的地震收集器的性能。这项研究将涉及：(1)在利哈伊大学的NHERI实验设施中对钢结构组合楼板系统中的集热器构件进行大规模测试；(2)在加州大学圣地亚哥分校的NHERI振动台设施中对一个0.4比例的单层钢组合楼板系统进行振动台试验；(3)钢结构集热器构件、细节和周围区域在地震作用下的非线性分析，以及钢建筑在强震作用下的地震模拟。计划中的钢铁收集器实验，具有现实的边界条件和惯性力，将是此类实验的第一次。将从大规模物理试验中产生新的数据产品和校准的数值模型。将建立集热器和集热器惯性力路径的解析模型。将研究成果转化为实践将包括：(1)低损害结构设计的新概念，(2)基于研究的设计建议，以及(3)评估和改造指南。

To safely survive an earthquake, and thereby protect its occupants, contents, adjacent property, and passersby, a building structure must transfer the large forces that develop during the earthquake from within the building down to the foundation. Earthquake (lateral) forces are generated by the building weight being accelerated horizontally, and thus most earthquake forces originate in the building's heaviest element, i.e., its floors. A key structural element in the force transfer path to the foundation are collectors, which are either special reinforcement in the floor slab or special beams below the slab, that "collect" the forces in the floor, and transfer them to the primary seismic force-resisting vertical elements (frames, braces, or walls). The loss of collectors or collector connections can be catastrophic, as evidenced by the collapse of the CTV building in the 2011 Christchurch, New Zealand earthquake, which killed 115 people, the largest loss of life in this event, and to some extent the collapse of nine parking garages in the 1994 Northridge, California earthquake. Despite the critical nature of seismic collectors, no research effort, including physical testing, has focused specifically on collectors, and knowledge of their seismic performance is lacking. A challenge in understanding the performance of seismic collectors is the complex nature of the floor system itself, a complicated assemblage of many components of different materials (e.g., steel, metal, and concrete) at different elevations, with multiple purposes and uncertain force paths. Past seismic design methodologies for buildings may have significantly underestimated the collector forces. This lack of knowledge impacts not only new construction but also the assessment and retrofit of existing, especially critical care, facilities in high seismic regions. This condition also applies to older non-seismic compliant steel structures nationwide, where inadequate or non-existent seismic collectors are often a major concern. A better understanding of the performance of steel seismic collectors is needed for safe and economical structures, both in the existing building stock and for new construction. Further, the collector's unique role as the critical link between the floor and the vertical elements provides an opportunity for collectors from trying to "out-strength" the earthquake force to instead serve as an innovative force-limiting element that protects the structure from damage. The goals of this research are to: (1) advance knowledge on the seismic performance, analysis, and design of collectors in steel composite floor systems, and (2) develop new knowledge on the reliable seismic performance and potential benefits of innovative collector concepts that can lead to low-damage structural design. This project will support researchers and graduate students from the University of Arizona, University of California, San Diego, and Lehigh University. The project will benefit from working closely with collaborators who are separately supported, i.e., a researcher and a practitioner in New Zealand and an industry panel of seismic design engineers in the United States. An outreach program will be conducted by the University of Arizona with local K-8 schools identified demographically as possessing student bodies of predominately underrepresented groups. The outreach program will target third, fourth, and eighth grade students to include: (1) slides shows and question and answer sessions on earthquake engineering, (2) career mentoring from graduate and undergraduate students, and (3) hands-on science and math activities.In this project, an integrated research program will investigate the performance of seismic collectors for steel composite deck structures using the experimental and computational simulation capabilities afforded by the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI). The research will involve: (1) large-scale testing of collector elements in a steel composite floor system at the NHERI experimental facility at Lehigh University, (2) shake table testing of a 0.4-scale, single-story, steel composite floor system at the NHERI shake table facility at the University of California, San Diego, and (3) nonlinear analysis of steel structure collector elements, details and surrounding regions under seismic effects, and earthquake simulations of steel buildings under strong earthquakes. The planned experiments on steel collectors, with realistic boundary conditions and inertial forces, will be the first of its kind. New data products and calibrated numerical models will be produced from large-scale physical testing. Analytical models will be developed for the collectors and the collector inertial force paths. Transfer of research results into practice will include: (1) new concepts for low-damage structural design, (2) research-based design recommendations, and (3) assessment and retrofit guidelines.