Advancing Earthquake Engineering of Cast-in-Place Concrete Diaphragms with Openings

在钢筋混凝土建筑物中，现浇楼板或“隔板”必须承受结构和建筑物重量的重力荷载以及地震期间由风或楼板惯性引起的水平荷载。为了使建筑物发挥作用，这些楼板横隔还必须包含楼梯、电梯和机械系统的开口。虽然在设计重力荷载结构时考虑了这些开口的存在，但很少有研究或了解它们在地震荷载作用下如何影响建筑物的行为。这种缺乏了解的潜在后果最近在一座五层钢筋混凝土建筑的地震模拟器测试中得到了证明。在测试过程中意外的隔膜损坏表明，邻近墙壁和柱子的开口会导致倒塌风险，并可能妨碍或延迟地震事件后建筑物功能的恢复。这个灾难恢复力研究赠款（DRRG）项目将开发一个基本的理解的行为，现浇混凝土隔膜与开口，并开发工具，其设计和概率量化其预期性能在地震期间。这项研究将通过一个在线课程来补充，该课程侧重于为学生和从业人员提供准确的模拟方法及其验证，作为最近建立的地震工程证书计划和推广活动的一部分，以吸引代表性不足的少数民族和第一代大学生参与研究。通过模拟驱动的试验测试和原型建筑物在多个烈度下的非线性有限元分析，对现浇混凝土开洞横隔板抗震恢复型地震工程进行了研究。本研究将调查（1）准确的载荷路径，包括从低应力区域到支柱的扇形收集模式，形成主要载荷路径;（2）开口和建立保护区的影响，以减轻可能导致部分倒塌的损坏;以及（3）损坏状态和脆性曲线，量化隔膜性能，以纳入功能恢复方法。几个基本的研究问题将得到回答，包括（1）什么是惯性荷载路径通过膜片，以及这些荷载路径是如何影响的开口;（2）板的厚度，钢筋，以及开口的存在如何影响膜片元件的能力受到复杂的面内应力;（3）开孔的存在如何改变横隔梁的有效刚度，以及对工程需求参数的影响;（4）工程需求参数、地震动强度措施与横隔板损伤之间的关系;以及（5）开口周围的隔膜损坏如何影响安全、楼层访问和宗旨功能。同样重要的是，该项目将成为进一步研究的基础，以充分研究抗侧力系统，包括板墙和板柱连接，使用伪动力和地震模拟器测试。该奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

In reinforced concrete buildings, cast-in-place floor slabs, or “diaphragms”, must resist both gravity loads, the weight of the structure and building contents, and horizontal loads, caused by wind or the inertia of the floors during earthquakes. For the building to function, these floor diaphragms also must contain openings for stairs, elevators, and mechanical systems. Although the presence of these openings is accounted for when designing the structure for gravity loads, there is little research or understanding of how they affect the building’s behavior during earthquake loading. The potential consequences of this lack of understanding were recently demonstrated during earthquake simulator tests on a five-story reinforced concrete building. Unexpected diaphragm damage during testing indicates that openings adjacent to walls and columns contribute to collapse risk and could preclude or delay the return of a building’s functionality after a seismic event. This Disaster Resilience Research Grants (DRRG) project will develop a fundamental understanding of the behavior of cast-in-place concrete diaphragms with openings and develop tools for their design and for probabilistically quantifying their expected performance during an earthquake. The research will be complemented by an online class curriculum focusing on accurate simulation approaches and their validation, for both students and practitioners, as part of the recently established earthquake engineering certificate program and outreach to engage underrepresented minority and first-generation college students in research.This award will focus on advancing science-based tools and technologies, through simulation-driven experimental testing and nonlinear finite element analysis of prototype buildings under multiple hazard intensities, for the collapse-resistant and recovery-based earthquake engineering of cast-in-place concrete diaphragms with openings. This research will investigate (1) accurate load paths, including fanned collection patterns from regions of low stress to struts, which form the primary load path; (2) the impact of openings and establishing protected zones to mitigate damage that could lead to partial collapse; and (3) damage states and fragility curves that quantify diaphragm performance for inclusion in functional recovery methodologies. Several fundamental research questions will be answered, including (1) what is the inertial load path through the diaphragm, and how are these load paths affected by openings; (2) how does the slab thickness, reinforcement, and the presence of openings affect the capacity of diaphragm elements subjected to complex in-plane stresses; (3) how does the presence of openings modify the effective stiffness of diaphragms, and what is the effect on engineering demand parameters; (4) what is the relationship between engineering demand parameters, ground motion intensity measures, and diaphragm damage; and (5) how does diaphragm damage around openings affect safety, story access, and tenet functionality. Equally important, this project will form the foundation for additional research to fully investigate the lateral force resisting system, including slab-wall and slab-column connections, using pseudo-dynamic and earthquake simulator testing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.