NEESR-CR: Assessment of Punching Shear Vulnerability of Slab-Column Connections with Shear Stud Reinforcement

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，包括密歇根大学（牵头机构）、明尼苏达大学双城分校（次级奖项）和明尼苏达大学德卢斯分校（次级奖项）。该项目将利用明尼苏达大学（双城）的NEES设备站点。由柱直接支撑的板或平板框架系统组成的结构体系因其建筑外观、功能性和经济性而广泛应用于混凝土建筑中。在地震危险性高的地区，它们已用于高达60层的结构中，与结构墙或抗矩框架相结合。由于它们在地震中有可能发生冲剪破坏，所以剪切加固通常以头部剪切螺柱的形式提供。然而，作为先前NEESR项目（NSF award 0421180）的一部分进行的测试结果引起了人们对这种增强材料抗冲剪有效性的严重担忧。考虑到在过去十年中建造了大量带有头部加固的平板结构，这些测试结果可能表明，一个潜在的重大问题可能会在西海岸的下一次大地震中浮出水面。如果这确实像之前的NEESR测试结果所表明的那样严重，那么地震工程界应该谨慎行事，防止类似1994年加州北岭地震期间焊接钢连接所观察到的情况发生。该项目涉及来自三所美国大学和墨西哥国立大学Autónoma （UNAM）的一组研究人员。主要研究目的是通过评估实际应用的典型头加固设计的效率来估计现有板-柱连接的脆弱性。大型板柱组件将在明尼苏达大学NEES-MAST实验室进行组合重力载荷和双轴侧向位移的测试。这些测试将允许评估带有头钉加固的板柱连接在强地面运动中的脆弱性。还将在UNAM进行平板结构的振动台试验，以评估带有头部加固的连接在动力激励下的响应。智力优势：这项研究将产生所需的信息，使执业工程师和建筑官员能够识别带有头部加固的脆弱平板建筑。这是为数不多的几个例子之一，在这些担忧被大地震证实之前，实验研究已经引发了对现代结构安全性的重大担忧。因此，在这个项目中开发的知识可能会对保护生命和减少地震中平板结构潜在失效或倒塌所带来的经济损失产生重大影响。更广泛的影响：教育和推广计划针对本科生和大学预科学生。通过使用明尼苏达大学NEES设备现场的远程参与功能，这些学生将有机会见证实验计划的各个步骤，并远程参加有关地震基础知识和地面运动混凝土结构设计的讲座。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 an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes the University of Michigan (lead institution), the University of Minnesota, Twin Cities (subaward), and the University of Minnesota, Duluth (subaward). This project will utilize the NEES equipment site at the University of Minnesota (Twin Cities). Structural systems that consist of slabs directly supported by columns or flat plate frame systems are widely used in concrete construction because of their architectural appearance, functionality, and economy. In regions of high seismic hazard, they have been used in structures of up to 60 stories, in combination with structural walls or moment resisting frames. Because of their potential for punching shear failures during earthquakes, shear reinforcement is often provided in the form of headed shear studs. Results from a test conducted as part of a prior NEESR project (NSF award 0421180), however, have raised serious concerns about the effectiveness of this reinforcement for punching shear resistance. Given the large number of flat-plate structures with headed reinforcement built in the last decade, these test results could be an indication of a latent major problem that could surface in the next large earthquake on the west coast. If this is indeed as serious of a problem as the prior NEESR test results seem to indicate, the earthquake engineering community should act with diligence and prevent a situation similar to that observed with welded steel connections during the 1994 Northridge, CA earthquake.This project involves a group of researchers from three U.S. universities and the Universidad Nacional Autónoma de México (UNAM). The main research objective is to estimate the vulnerability of existing slab-column connections by evaluating the efficiency of typical headed reinforcement designs used in practice. Large-scale slab-column subassemblies will be tested under combined gravity load and biaxial lateral displacements at the University of Minnesota NEES-MAST Laboratory. These tests will allow the evaluation of the vulnerability of slab-column connections with headed stud reinforcement during strong ground motions. Shake table tests of a flat-plate structure will also be conducted at UNAM for evaluation of the response of connections with headed reinforcement under dynamic excitation.Intellectual Merit: This research will generate needed information that will allow practicing engineers and building officials to identify vulnerable flat-plate construction with headed reinforcement. This is one of a very few instances in which experimental research has prompted major concerns about the safety of modern structures before those concerns are confirmed by a major earthquake. Thus, the knowledge developed in this project could have a major impact in terms of protecting lives and reducing financial losses associated with potential failure or collapse of flat-plate structures during an earthquake.Broader Impacts: The education and outreach program targets undergraduate and pre-college level students. Through the use of the teleparticipation capabilities at the University of Minnesota NEES equipment site, these students will have the opportunity to witness the various steps of the experimental program and remotely attend lectures on the basics of earthquakes and design of concrete structures for ground motions. Data from this project will be archived and made available to the public through the NEES data repository.