Collapse simulation of multi-story buildings through hybrid testing with substructuring techniques
Hashemi, M. Javad
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Collapse prevention and life safety are of utmost importance in earthquake resistant design. Structures, however, have a small probability of collapse due to uncertainties in the ground motion and the structure's response. The assessment of this probability requires the prediction, with sufficient confidence, of the structure's response through collapse and, thus, poses significant challenges. In order to validate those predictions and evaluate phenomena that are not adequately represented in component tests, experimental tests at the structure level are needed. Shaking table tests, although an excellent option at first glance, can be very complex, expensive and potentially dangerous. Hybrid testing can be an attractive alternative since it can provide information of the system response without having to test the entire structure, making it a versatile and cost-effective testing approach to investigate structural behavior through collapse. In addition, hybrid simulation can be executed on an extended time-scale to carefully inspect the specimen, track the process of damage, and the sequence of failures leading the structure to collapse. The benefits of hybrid simulation through collapse can be further enhanced through accurate and practical substructuring techniques that do not require testing of the entire structure and focus only on the critical portion. An innovative substructuring technique for hybrid simulation of structures subjected to large deformations is proposed to simplify the boundary conditions by overlapping the domains between the numerical and experimental subassemblies. The advantages of this substructuring technique are that: it requires only critical components of the structure to be tested experimentally; it reduces the number of actuators at the interface of the experimental subassemblies; and it can be implemented using typically available equipment in laboratories such as strain gauges or load cells. Further studies were conducted to improve the capability and reliability of the substructure hybrid simulation utilizing advanced optimization techniques and online model updating. A new hybrid test framework is proposed with an updating scheme to optimize the initial modeling parameters of the numerical models based on the instantaneously-measured response of similar experimental elements as the test progresses. A recently developed state observer, the Unscented Kalman Filter, that can be utilized online in real-time for highly nonlinear behavior was implemented in application for substructure hybrid simulation.