Abstract
The primary goal of earthquake resistant design is to protect life safety of occupants by preventing the collapse of structures. Specifically, structures should have only a very small probability of collapse. Assessment of this small probability of collapse poses major challenges, as it requires the ability to predict, with sufficient confidence, the response of structures through collapse. To validate collapse predictions and to evaluate phenomena that are not represented adequately in component tests, experimental tests at the structure level are needed. Shaking table testing represents an excellent option. However, shaking table testing to collapse is very complex, very expensive, and potentially dangerous. Hybrid testing can provide information on the response of the structure without having to test the entire structure. This makes hybrid testing a potentially versatile and cost-effective testing approach to investigate response of structures through collapse. This paper summarizes the results of a three-year collaborative research project between four universities whose main goal of this investigation was to advance knowledge and develop techniques to improve our understanding of the response of structures as they approach collapse. Results from hybrid simulation of a 1/8 scale steel moment frame previously tested on a shaking table to a sequence of ground motions with increasing intensity is presented. Detailed comparisons between shake table results and hybrid simulation results are presented and discussed. Additionally results from small scale testing of deep wide flange steel columns under various loading protocols to analyze the influence of axial load at large levels of deformation are presented. A third phase of the project included half scale testing of new interior “gravity-only” connections which not only preserve vertical load carrying capacity at interstory drift demands as large as 9% but they also significantly decrease the probability of collapse in the building. Education, Outreach and Training activities conducted as part of this investigation are also summarized.