NEESR-II: Behavior and Design of Cast-in-Place Anchors under Simulated Seismic Loading

该奖项是NSF 07-506项目征集的结果。小布朗地震工程模拟网络（NEES）研究（NEESR）竞赛，包括威斯康星大学密尔沃基分校（牵头机构）和辛辛那提大学（子奖项）。 该项目将利用伊利诺伊大学厄巴纳-香槟分校的NEES设备场地。 有头锚/螺柱通常用于结构中以连接钢构件（例如，柱、大梁或支撑）和混凝土元件（例如，分别为地基、墙或柱）。 混凝土元件可能遭受实质性的损坏（例如，大地震时， 了解裂缝混凝土中锚杆的性能是确保结构抗震性能和安全性的前提。 美国混凝土协会318-05文件附录D所代表的现行抗震设计指南不适用于严重开裂混凝土中的有头锚栓/螺柱的设计。设计规定默认地依赖于锚的保留能力和钢断裂引起的可感知延性失效模式。 由于地震荷载下锚性能的数据有限，这两种理论依据都是有问题的。 此外，锚杆在拉剪复合循环荷载作用下的相互作用方程尚未得到实验验证。因此，许多锚连接，包括那些利用锚周围的额外钢筋，往往是在实践中实现没有支持的实验数据。 知识差距的部分原因是，在NEES设施于2004年投入使用之前，可用于此类测试的实验设备有限。 本项目将研究模拟地震荷载下有头锚栓/螺柱的基本性能，并验证和改进实践中常见的锚连接细节。该项目将开发连接接口模型，以改进基于模型的模拟，并协助开发基于性能的工程方法。 特别是，本研究澄清了目前的能力设计理念，重新定义了延性破坏模式的定义，并评估了在循环拉剪下的锚的相互作用方程。研究还探讨了将现有的设计方程扩展到嵌入混凝土构件中的锚，这些锚可能会遭受重大损坏。根据地震荷载作用下单根锚性能的基本知识，将对两种典型的锚连接进行实验评估，并开发和验证具有改进性能特征的连接细节。 为提高锚连接的承载力和延展性，将提出有效使用补充钢筋的建议，并为工程师提供设计指南沿着实例。本研究将影响桥梁、供水和供电线路等使用锚连接的各种结构的设计和安全性。 教育活动将与NEES Consortium，Inc.协调。 实验结束后，所有数据将通过NEES数据储存库（http：//www.example.com）提供。www.nees.org

This award is an outcome of the NSF 07-506 program solicitation ''George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)'' competition and includes the University of Wisconsin-Milwaukee (lead institution) and the University of Cincinnati (subaward). This project will utilize the NEES equipment site at the University of Illinois at Urbana-Champaign. Headed anchors/studs are commonly used in structures to connect steel members (e.g., columns, girders, or braces) and concrete elements (e.g., foundations, walls, or columns, respectively). The concrete elements may experience substantial damage (e.g., large cracking) during an earthquake. Understanding the behavior of anchors in cracked concrete is a prerequisite to ensuring satisfactory seismic performance and safety of structures. Current seismic design guidelines, represented by Appendix D of the American Concrete Institute 318-05 document, are not adequate for the design of headed anchors/studs in significantly cracked concrete. The design provisions tacitly rely on reserved capacity of anchors and perceived ductile failure modes due to steel fracture. Both of these rationales are questionable because of the limited data for anchor behavior under seismic loading. In addition, the interaction equations for anchors under combined cyclic tension-shear have not been verified experimentally. As a result, many anchor connections, including those taking advantage of additional reinforcement around the anchors, are often implemented in practice without supporting experimental data. The knowledge gap is due partly to the limited experimental equipment available for such testing before the NEES facilities became operational in 2004. This project will investigate the fundamental behavior of headed anchors/studs under simulated seismic loading and verify and improve the anchor connection details commonly seen in practice. The project will develop connection interface models to improve model-based simulations and to assist in the development of performance-based engineering methodologies. Particularly, this research clarifies the current capacity design philosophy, redefines the definition of ductile failure modes, and evaluates the interaction equation for anchors under cyclic tension-shear. The research also explores extending the existing design equations to anchors embedded in concrete members that may experience significant damage. With the fundamental knowledge on single anchor behavior under seismic load, two typical anchor connections, which have been used in practice without justification, will be evaluated experimentally, and connection details with improved performance characteristics will be developed and verified. Recommendations for effective use of supplemental reinforcement for improving the capacity and ductility of anchor connections will be made, and design guidelines, along with examples, will be generated for engineers.This research will impact the design and safety of a wide range of structures that utilize anchor connections, such as bridges and water and power supply lines. Education activities will be coordinated with NEES Consortium, Inc. Following the experiments, all data will be made available through the NEES data repository (http://www.nees.org).