NEESR-CR: Multi-Scale, Mechanistic Fracture Prediction and Optimal Panel Zone Participation in Steel Moment Frame Buildings

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该奖项是NSF 09-524项目招标“小乔治·e·布朗地震工程模拟（NEES）研究网络（NEESR）”竞赛的结果，包括位于德克萨斯州大学城的德克萨斯农工大学（牵头机构）、位于德克萨斯州奥斯汀的德克萨斯大学（次级奖项）、位于宾夕法尼亚州伊斯顿的拉斐特学院（次级奖项）和位于德克萨斯州加尔维斯顿的德克萨斯农工大学（次级奖项）。该项目将利用明尼苏达大学的NEES设备站点。在美国和世界上许多其他地方，钢弯矩框架广泛用于抗震建筑。尽管在1994年加州北岭地震之后，人们对钢弯矩框架进行了广泛的研究，但一个关键的技术问题仍未得到解决：钢弯矩框架节点（梁与柱连接）中的面板区域的作用。最近的美国建筑规范大大增加了钢框架面板区域的强度要求。为了满足这些要求，必须增加色谱柱的尺寸或在色谱柱上焊接倍板，从而导致成本的增加，有时甚至是大幅度的增加。然而，有重要的实验证据表明，弱板区弯矩框架节点具有很高的延性，并且在循环荷载下始终保持较大的层间漂移角而不会出现强度退化。也有分析证据表明，具有弱板带的弯矩框架可以实现出色的整体抗震性能。这强烈表明，目前的建筑规范在面板区域设计上采用了不正确的方法，不必要地增加了建筑成本，同时潜在地降低了抗震性能。本研究的总体目标是解决这样一个问题：在评估钢弯矩框架的非弹性地震反应时，应该允许多少面板区域参与？尽管过去有许多关于这个问题的研究，但在研究团体和建筑监管团体内部，关于面板区域在设计中应该如何处理的观点存在激烈的冲突。分歧的关键是对面板区屈服引起的断裂的关注。人们似乎普遍认为面板区域屈服是一个高度延展性的过程。然而，对于面板区屈服在关节断裂中的作用，目前存在广泛的分歧。为了解决这些问题，需要具备预测受地震载荷影响的薄弱板带节点断裂的基本能力。因此，本研究的知识价值和关键目标是在预测钢建筑结构的关键延性构件的循环破裂方面推进技术的发展，并将这些知识应用于钢弯矩框架的面板区域问题。为了实现这些目标，本研究项目将整合(1)结合梁柱节点高分辨率有限元模拟的钢构件循环断裂基础研究，(2)先进的框架模拟研究，(3)在明尼苏达大学NEES设备上进行的大规模实验研究，以及(4)节点性能的参数计算研究。就更广泛的影响而言，从这项研究中获得的知识有望影响抗震钢矩框架的设计实践和建筑规范。项目团队将为高中科学和数学教师开展一项专业发展计划，以创建和提供基于网络的教学材料，将地震工程相关问题的概念带入课堂。该项目的数据将存档，并通过NEES数据储存库向公众提供。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This award is an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes Texas A&M University in College Station, Texas (lead institution), The University of Texas in Austin, Texas (subaward), Lafayette College in Easton, Pennsylvania (subaward), and Texas A&M University in Galveston, Texas (subaward). This project will utilize the NEES equipment site at the University of Minnesota.Steel moment frames are widely used for seismic-resistant building construction throughout the United States and in many other parts of the world. Although steel moment frames were studied extensively following the 1994 Northridge, California, earthquake, one critical technical issue remains unsolved: the role of the panel zone in steel moment frame joints (beam to column connections). Recent U.S. building codes have significantly increased the required strength of panel zones in steel moment frames. To satisfy these requirements, column sizes must be increased or doubler plates must be welded to the column, resulting in increased cost, sometimes substantially so. However, there is significant experimental evidence that moment frame joints with weak panel zones show highly ductile performance, and consistently achieve large interstory drift angles under cyclic loading without strength degradation. There is also analytical evidence suggesting excellent overall seismic performance can be achieved by moment frames with weak panel zones. This strongly suggests that current building codes have adopted an incorrect approach to panel zone design, needlessly increasing the cost of construction while potentially degrading seismic performance. The overall goal of this research is to resolve the question: how much panel zone participation should be permitted in evaluating the inelastic seismic response of a steel moment frame? Despite a number of past studies on this issue, there are sharply conflicting views of how panel zones should be treated in design, both within the research community as well as within the building regulatory community. At the crux of the disagreements are concerns regarding fracture induced by panel zone yielding. There appears to be broad agreement that panel zone yielding is a highly ductile process. However, there is broad disagreement on the role that panel zone yielding plays in joint fracture. To address these concerns will require the fundamental capability to predict fracture at joints with weak panel zones subject to seismic loading. Thus, the intellectual merit and a key objective of this research is to advance the state of the art in predicting cyclic rupture within critical ductile components of steel building structures, and to apply this knowledge to the problem of the panel zone in steel moment frames. To meet these goals, this research project will integrate (1) fundamental studies on cyclic rupture of steel components combined with high resolution finite element simulations of beam-column joints,(2) advanced frame simulation studies, (3) large-scale experimental studies conducted at the NEES equipment at the University of Minnesota, and (4) parametric computational studies on joint performance. With respect to broader impacts, the knowledge gained from this research is expected to impact design practice and building codes for seismic-resistant steel moment frames. The project team will conduct a professional development program for high school science and mathematics teachers to create and deliver web-based instructional materials to bring concepts of earthquake engineering-related problems into the classroom. Data from this project will be archived and made available to the public through the NEES data repository.