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“小乔治·E·布朗地震工程模拟(NEES)研究网络(NEESR)”竞赛的结果，包括威斯康星大学密尔沃基分校(牵头机构)和辛辛那提大学(分奖机构)。该项目将利用伊利诺伊大学香槟分校的NEES设备。带头锚杆/立柱通常用于连接钢构件(例如，柱、大梁或支撑)和混凝土构件(例如，分别是基础、墙或柱)。混凝土构件在地震期间可能会遭受重大破坏(例如，大裂缝)。了解裂缝混凝土中锚杆的行为是确保结构具有良好的抗震性能和安全性的前提。以美国混凝土学会318-05文件附录D为代表的现行抗震设计准则不足以用于严重开裂混凝土中的带头锚/柱的设计。设计条款默示地依赖于锚杆的预留能力和由于钢材断裂而感知到的延性破坏模式。由于地震荷载作用下锚固性能的数据有限，这两种理论都值得商榷。此外，锚杆在循环拉剪联合作用下的相互作用方程尚未得到试验验证。因此，许多锚杆连接，包括那些利用锚杆周围的额外配筋的连接，在实践中往往没有支持试验数据。知识差距的部分原因是，在2004年NEES设施投入使用之前，可用于这类测试的实验设备有限。该项目将研究在模拟地震荷载作用下带头锚杆/螺柱的基本行为，并验证和改进实践中常见的锚杆连接细节。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，本研究澄清了现有的承载力设计思想，重新定义了延性破坏模式的定义，并对循环拉剪作用下锚杆的相互作用方程进行了评估。这项研究还探讨了将现有的设计公式扩展到可能遭受重大破坏的混凝土构件中的锚杆。在掌握了单一锚杆在地震荷载作用下的基本行为的基础上，对两种典型的锚杆节点进行了试验评估，开发并验证了性能得到改善的节点细节。这项研究将对广泛使用锚固连接的结构的设计和安全性产生影响，例如桥梁和供水、供电线路。教育活动将与NEES Consortium，Inc.协调。实验结束后，所有数据将通过NEES数据库(http://www.nees.org).)提供

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).