Pre/Post Earthquake Damage Assessment for Infilled RC Frame Buildings
Andreas Stavridis Principal Investigator
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This project plans to dynamically test in the field an existing two-story reinforced concrete frame building infilled with unreinforced masonry walls. The building, located in El Centro, CA, was built in the 1920s and it is typical of the construction practice in California in that era. Buildings with similar characteristics are located in regions with high seismicity such as Los Angeles, San Francisco, the Mediterranean region, and Latin America. Such buildings often have historical significance but they have proved vulnerable to earthquakes. Understanding and improving their behavior has been a challenging task for engineers. The building selected in this study has sustained damage during earthquakes of 1940, 1979, and 1987 and 2010 which have been recorded in close proximity. The building was repaired and retrofitted after the first three earthquakes; however, the damage induced during the 2010 event cannot be repaired cost-effectively considering the economy in the area. Hence, the structure is scheduled to be demolished. This provides a unique opportunity to test a real life building using mobile shakers. The testing will be incremental and it is expected to bring the building on the verge of collapse. The unique experimental data from the field will enhance our understanding of the complex behavior of these structures and their failure mechanisms, and it will be useful for future analytical, as well as laboratory shake-table studies since it will provide benchmark data for researchers and practitioners involved with earthquake engineering. <br/><br/>The aim of the proposed research is to develop a framework for the reliable assessment of damage in existing reinforced concrete frames infilled with masonry walls. The data obtained from field testing will be used to validate finite element models and damage identification techniques. The combination of the two tools will allow the derivation of a damage index that can be used to identify the state of a structure prior or after an extreme event. Emphasis will be given in modeling the three-dimensional behavior of the structure including the out-of-plane behavior of the infill walls. Moreover, simplified models will be developed and validated with the results of the detailed analytical models. The building that will be the focal point of this experimental and analytical study was selected because it has sustained considerable damage due to four historical earthquakes that have been recorded in close proximity. The data obtained from the forced vibrations of the building will be also used for the validation of the analytical tools. In summary, the proposed research includes full-scale tests that will push a damaged structure further into the nonlinear behavior; finite element models to capture the in- and out-of-plane interactions between the infills and the bounding frame; validation of the model with data obtained from the tests, as well as validation with data from previous earthquakes; and development and validation of a system and damage identification techniques for the quantification of damage in a real structure.