Seismic Performance Assessment and Retrofit of Non-Ductile RC Frames with Infill Walls

Researchers of UC San Diego conducted shake table tests on a 3-story, non-ductile, masonry-infilled, reinforced concrete frame representing structures built in California in the 1920's. The tests on the 2/3 scale specimen are part of the collaborative project between University of Colorado at Boulder, Stanford University and University of California San Diego, which is the lead institution. The research project is funded by the George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES) and is already in its 4th and final year.

The goal of the research team led by Benson Shing, a UCSD structural engineering professor, is to develop and implement analytical tools to assess the seismic vulnerability of existing structures and techniques to retrofit them. To succeed in their goals, the researchers also collaborate with a Professional Advisory Panel, a group of practicing engineers from different parts of the country, with significant experience in analyzing and retrofitting this type of structures.

The focal point of this study has been a structure designed in UCSD to represent the building practice in California in the 1920's era. At that time infill panels were often considered as non-structural elements, but even nowadays their exact role and behavior during an earthquake is unclear since they interact with the bounding RC frame. Currently, there is a lack of reliable analysis methods to evaluate the seismic performance of these structures, and validated retrofit methods to improve their seismic behavior. The ultimate goal is to provide methods to assess and improve the seismic performance of historical buildings located in areas like downtown Los Angeles and San Francisco. However, the impact of this research project is larger since this type of structural system is very common in areas of high seismicity around the world, like China and the Mediterranean region.

The earthquake tests are conducted at the NEES@UCSD outdoor shake table which is part of the UCSD Jacobs School of Engineering's Englekirk Structural Engineering Center and also one of the 15 NEES testing facilities After the structure is tested to failure, the researchers will use the data to validate the analytical models and analyze the failure patterns and behavior of the structure so that they develop a scheme to retrofit a second specimen with the same design that will be built and tested in early 2009. These tests will conclude a series of tests ranging from small-scale quasi-static tests at Stanford to large-scale single-bay, single-story specimens at NEES@Colorado. The test data will be shared with the community for blind prediction analysis.