NEESR-CR: Enabling Performance-Based Seismic Design of Multi-Story Cold-Formed Steel Structures

该奖项是美国国家科学基金会(NSF)09-524项目征集“小乔治·E·布朗地震工程模拟(NEES)研究网络(NEESR)”竞赛的结果，包括约翰·霍普金斯大学(JHU)(牵头机构)和巴克内尔大学(次级奖项)。该项目将利用纽约州立大学布法罗大学(UB)的NEES设备场地。这项研究的目标是提供所需的知识，以提高使用轻质冷弯薄壁型钢(CFS)作为主梁和主柱的建筑的地震安全性，并使工程师能够在预测这些建筑对地震的反应时考虑到完整的建筑性能。美国的学术研究团队通过与加拿大麦吉尔大学支持的研究人员的合作，以及由美国钢铁学会(AISI)和宾利系统公司推动的业界参与和支持而得到加强。轻量级CFS框架是一种独特而有效的低层和中层结构建筑解决方案，但要使该系统实现其充分的效率，以及充分启用现代基于性能的抗震设计方法，仍有许多需要了解的地方。该项目建立在单层剪力墙研究的基础上，以解决多层CFS横向抗力体系。JHU的组件级实验，结合UB NEES设施的全尺寸建筑实验，将导致更好的理解，并为将要开发的计算模型提供验证和验证。计算模型将包括用于探索和扩展试验工作的高保真模型，以及适用于CFS建筑的非线性时程分析和增量动力分析的高效降阶模型。通过本研究，结构将被视为一个完整的体系，楼板(横隔板)和墙将不被理想化为简单的剪力墙收集器，而是体系本身对建筑抗震的贡献。特别是，UB NEES振动台设施将被用于测试一座多层的CFS框架建筑，其中包括(A)仅横向系统到位，(B)横向和重力系统完全到位，以及(C)结构和非结构系统到位。这一系列测试将能够识别这些独立的系统及其交互作用，并为模拟工具提供验证建模。CFS建筑弹塑性时程分析的一个关键进展是发展了一种高效梁单元，该单元结合了CFS薄壁截面局部屈曲和变形屈曲所固有的强度和刚度降低。这个项目将开发一种新的框架单元，并结合有限条横截面分析在OpenSees中实现。这种新的单元为其他薄壁结构在抗震设计中的应用奠定了基础，例如结构塑料、铝、超高强度钢，所有这些结构都必须考虑由于其固有的薄壁性质而产生的横截面变形。智力优势：该研究计划解决了CFS结构抗震设计最紧迫的缺点：多层剪力墙不能有效地模拟，并且对其与完整结构体系的相互作用的了解不完整。更广泛的影响：研究活动将被用来扩大巴尔的摩理工高中研究实践计划的正在进行的外展，并将涉及来自JHU和巴克内尔的学生。这项研究将被用来改进本科教育，包括JHU和巴克内尔的课程，并开发适用于重复框架结构的教学振动台模型。督导计划将积极向研究和实践工程界传播研究结果。具体地说，PI与AISI及其委员会以及冷弯钢工程师学会进行了广泛的合作，该学会对实践进行了大量的推广。该项目的数据将被存档，并通过NEES数据库向公众提供。该奖项是国家减少地震灾害计划(NEHRP)的一部分。

This award is an outcome of the National Science Foundation (NSF) 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes Johns Hopkins University (JHU) (lead institution) and Bucknell University (subaward). This project will utilize the NEES equipment site at the University at Buffalo (UB), State University of New York. The goal of this research is to generate the knowledge needed to increase the seismic safety of buildings that use lightweight cold-formed steel (CFS) for the primary beams and columns, and enable engineers to account for complete building performance in predicting the response of these buildings to earthquakes. The U.S. academic research team is strengthened by collaboration with Canadian supported researchers at McGill University, and by the engagement and support of industry facilitated by the American Iron and Steel Institute (AISI) and Bentley Systems.Lightweight CFS framing is a unique and effective building solution for low and mid-rise structures, but one in which much remains to be understood for the system to achieve its full efficiency and for modern performance-based seismic design methods to be fully enabled. This project builds on single-story shear wall research to address multi-story, CFS lateral force resisting systems. Component-level experimentation at JHU, combined with full scale building experiments at the UB NEES facility, will lead to improved understanding and provide validation and verification for computational models that will be developed. The computational models will include high fidelity models for exploring and expanding on the experimental efforts, and high efficiency reduced order models appropriate for utilization in nonlinear time history analysis and incremental dynamic analysis of CFS buildings.Throughout this research, the structure will be treated as a complete system, and the floor (diaphragm) and wall will not be idealized as simple collectors for the shear wall, but as systems themselves contributing to the seismic resistance of the building. In particular, the UB NEES shake table facility will be utilized to test a multi-story, CFS framed building with (a) only the lateral system in-place, (b) the lateral and gravity system fully in place, and (c) structural and nonstructural systems in place. This series of tests will enable identification of these separate systems and their interactions, and provide validation modeling for the simulation tools. A key advancement for inelastic time history analysis of CFS buildings, necessary for modern performance-based seismic design of CFS members, is the development of a high efficiency beam element that incorporates the strength and stiffness reductions inherent in local and distortional buckling of thin-walled CFS cross-sections. This project will develop a new frame element coupled with finite strip cross-section analysis for implementation in OpenSees. This new element lays the foundation for other thin-walled structures to be utilized in seismic design, e.g., structural plastics, aluminum, ultra-high strength steel, all of which must include cross-section deformation due to their inherently thin-walled nature.Intellectual Merit: The research plan addresses the most pressing shortcomings of seismic design of CFS structures: multi-story shear walls cannot be effectively modeled, and knowledge of their interactions with the complete structural system is incomplete. Broader Impacts: Research activities will be used to expand ongoing outreach with the research practicum program at Baltimore Polytechnical High School and will involve students from JHU and Bucknell. The research will be utilized to improve undergraduate education, including courses at JHU and Bucknell, and to develop instructional shake table models appropriate for repetitively framed structures. The PIs will actively disseminate findings to the research and practicing engineering community. Specifically, the PI works extensively with AISI and its committees, as well as the Cold-Formed Steel Engineers Institute, which has significant outreach to the practice.Data from this project will be archived and made available to the public through the NEES data repository. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).