Collaborative Research: Behavior of Braced Steel Frames With Innovative Bracing Schemes - A NEES Collaboratory Project

PI:莱昂。1994年的北岭地震和1995年的神户地震表明，需要新的技术和结构形式来限制钢结构在中等和较大的地面运动下的破坏。在这种情况下，需要提供额外的刚度，以现代框架配置是明确的，导致在支撑框架配置的新兴趣。然而，支撑框架被认为不是很有延展性，因为单个支撑的屈曲很快导致层机制的形成。现代结构对刚度和延性的额外需求是由更轻的结构、更紧凑的抗横向载荷系统和基于性能的设计的出现的趋势所加剧的。为了解决与传统支撑框架相关的传统问题，一种新型的支撑系统，被称为拉链框架，将被开发和测试，作为这项工作的一部分。该建议代表了解决该问题的两阶段协作方法的第一阶段。在第一阶段的实验部分，四个实验室（佐治亚理工学院（GT）、布法罗大学（UB）、加州大学伯克利分校（UCB）和科罗拉多大学博尔德分校（CU））将对整个系统、子组合和单个元素的行为进行研究。这些将在各种荷载制度下进行测试，从振动台测试到准静态测试，以便提供全面的数据，作为设计建议的基础。在第一阶段的分析部分，上面列出的四所大学，加上佛罗里达a&m （FAMU）和伦敦帝国理工学院（IC），将进行广泛的分析研究，以提供(1)实验工作的基础和补充，(2)NEES联盟NEESgrid部分的测试平台，以及(3)用于设计的新的，简化的和全面的模型。作为第一阶段的最后一项任务，GT和FAMU的研究人员将为第二阶段制定方案，这将涉及在支撑钢结构中使用先进材料和主动控制。在提出的研究的智力优点是，它将提供一个独特的数据库信息的行为的拉链框架，并将提供从概念验证研究的结果对一类新的支撑系统。此外，该研究将导致分析模型的发展，可以实施到现有的地震分析程序。该研究将开发分析工具和方法，以允许实践工程师确定各种拉链框架应用的潜在好处。该项目还打算为NEES财团提供初步试运行研究，特别是测试NEESgrid系统的灵活性和稳健性。此外，它将从后勤和技术的角度为未来的NEES合作提供宝贵的经验。该项目将连接三个NEES站点、一个成熟的项目（GT）、一个发展中的项目（FAMU）和国际合作伙伴（IC），作为未来重大挑战合作的测试案例。该项目分为两个阶段，以便两位年轻的远程研究人员（GT的DesRoches博士和FAMU的Abdullah博士）将从第一阶段的工作中受益，从而发展他们在第二阶段所需的伪动力和振动台测试方面的技术专长。这将成为未来NEES项目的一个模式，在这些项目中，来自偏远地点的研究人员将能够从已建立的研究人员/地点获得宝贵的经验和指导。拟议的研究在很大程度上取决于五个地点的研究人员之间的合作。为了最大限度地发挥这个项目的潜在影响，我们提出了一个强有力的教育组成部分。为了补充合作研究计划，其中包括一个非常大的研究生交流，将开发一个NEES本科研究计划。该计划将由三个部分组成；本科生在研究基地的研究经历，夏季本科生研究交流计划，以及为期两天的学生研讨会。来自传统上代表性不足的群体的学生将特别针对本科研究项目。所提出的研究的更广泛的影响是，它将为设计界提供关于支撑框架结构性能的重要信息。此外，拟议的研究将作为未来使用NEES进行合作研究的模型。

PI: Leon. Georgia TechThe 1994 Northridge and 1995 Kobe earthquakes showed that new technologies and structural configurations are needed to limit damage to steel structures subjected to moderate and large ground motions. In this context, the need to provide additional stiffness to modern frame configurations is clear, leading to a renewed interest in braced frame configurations. Braced frames, however, are regarded as not being very ductile because buckling of individual braces quickly leads to formation of story mechanisms. The additional need for stiffness and ductility for modern structures is compounded by the trends towards lighter structures, more compact lateral-load resisting systems and the advent of performance-based design. To solve the traditional problems associated with conventional braced frames, a new class of bracing systems, known as a zipper frames, will be developed and tested as part of this proposed work. This proposal represents the first phase of a two-phase collaborative approach to the problem. In the experimental portion of the first phase, four laboratories (Georgia Tech (GT), U. at Buffalo (UB), U. of California at Berkeley (UCB), and the U. of Colorado at Boulder (CU)) will conduct studies on the behavior of whole systems, subassemblages, and individual elements. These will be tested under a variety of load regimes, ranging from shake table tests to quasi-static ones, in order to provide comprehensive data on which to base design recommendations. In the analytical part of the first phase, the four universities listed above, plus Florida A&M (FAMU) and Imperial College-London (IC), will conduct extensive analytical studies to provide (1) a basis and a complement to the experimental work, (2) a testbed for the NEESgrid portion of the NEES Consortium, and (3) new, simplified and comprehensive models for use in design. As the final task for the first phase, GT and FAMU researchers will develop the proposal for the second phase, which will deal with the use of advanced materials and active controls in braced steel structures. The intellectual merit in the proposed research is that it will provide a unique database of information on the behavior of zipper frames, and will provide results from proof-of-concept studies on a new class of bracing systems. In addition, the research will lead to the development of analytical models that can be implemented into existing seismic analysis programs. The research will develop analytical tools and methodologies to allow practicing engineers to determine potential benefits of a variety of applications of zipper frames. The project also intends provide initial shakedown studies for the NEES Consortium and in particular to test the flexibility and robustness of the NEESgrid system. In addition, it will provide valuable lessons from both the logistical and technical standpoints for future NEES collaborations. The project will link three NEES sites, one well-established program (GT), one developing program (FAMU) and international partner (IC) as a test case for future grand challenge collaborations. The project has been divided into two phases so that two younger remote researchers (Dr. DesRoches from GT and Dr. Abdullah from FAMU) will benefit from the work on the first phase in order to develop the technical expertise in pseudo-dynamic and shake table testing that they will need for the second phase. This intends to be a model for future NEES projects in which researchers from remote sites will be able to gain valuable experience and mentoring from established researchers/sites. The research proposed depends strongly on the collaboration between researchers at five sites. To fully maximize the potential impact of this project, a strong education component of the program is proposed. To complement the collaborative research program, that includes a very large exchange of graduate students, a NEES undergraduate research program will be developed. The program will consist of three components; an undergraduate research experience at the sites, a summer undergraduate research exchange program, and a 2-day student symposium. Students from traditionally underrepresented groups will be specifically targeted for the undergraduate research program. The broader impact of the proposed research is that is will provide important information for the design community on the performance of braced frame construction. In addition, the proposed study will serve as a model for future collaborative research using NEES.