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计划征求“乔治E。小布朗地震工程模拟网络（NEES）研究（NEESR）”竞赛，包括约翰霍普金斯大学（JHU）（牵头机构）和巴克内尔大学（子奖项）。本项目将利用纽约州立大学布法罗大学（UB）的NEES设备场地。 这项研究的目标是产生所需的知识，以提高使用轻型冷弯型钢（CFS）的主要梁和柱的建筑物的地震安全性，并使工程师能够在预测这些建筑物对地震的反应时考虑完整的建筑性能。通过与麦吉尔大学加拿大研究人员的合作，以及美国钢铁协会（AISI）和Bentley软件公司的参与和支持，美国学术研究团队得到了加强。轻型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，但是，对于该系统实现其全部效率和完全启用基于性能的现代抗震设计方法，仍有许多需要理解的地方。该项目建立在单层剪力墙的研究，以解决多层，CFS抗侧力系统。在JHU的实验室级实验，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实验工作的高保真度模型，以及适用于CFS建筑物非线性时程分析和增量动力分析的高效降阶模型。（横隔板）和墙将不会理想化为剪力墙的简单收集器，而是作为有助于建筑物抗震的系统本身。特别是，UB NEES振动台设施将用于测试多层CFS框架建筑，其中（a）仅横向系统就位，（B）横向和重力系统完全就位，以及（c）结构和非结构系统就位。这一系列测试将能够识别这些独立的系统及其相互作用，并为仿真工具提供验证建模。 CFS建筑物的非弹性时程分析的一个关键进步，现代性能为基础的抗震设计CFS成员，是一个高效的梁单元，结合了薄壁CFS截面的局部和畸变屈曲固有的强度和刚度降低的发展。该项目将开发一种新的框架单元，结合有限条横截面分析，以便在OpenSees中实施。这种新单元为其他薄壁结构在抗震设计中的应用奠定了基础，结构塑料，铝，超高强度钢，所有这些都必须包括横截面变形，由于其固有的薄壁性质。智力优点：研究计划解决CFS结构抗震设计的最紧迫的缺点：多层剪力墙不能有效地建模，其与完整的结构系统的相互作用的知识是不完整的。更广泛的影响：研究活动将用于扩大正在进行的推广与研究实习计划在巴尔的摩理工高中，并将涉及学生从JHU和巴克内尔。这项研究将用于改善本科教育，包括在JHU和巴克内尔课程，并开发适合于重复框架结构的教学振动台模型。 PI将积极向研究和实践工程界传播研究结果。具体而言，PI与AISI及其委员会以及冷弯型钢工程师协会（Cold-Formed Steel Engineers Institute）进行了广泛的合作，该协会对实践有着重要的影响。该项目的数据将通过NEES数据库存档并向公众提供。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).