Engineers work to make historic buildings safer during strong earthquakes

UC San Diego engineers recently tested a 1920s era masonry building in order to design retrofit guidelines for such structures, which exist all over the world. Photo:UC San Diego Jacobs School of Engineering

San Diego—Recent simulated earthquake tests conducted by UC San Diego engineers are expected to lead to retrofit schemes that make historic buildings safer. The structural engineers tested a structure similar to those that were built in California in the 1920s that have masonry-infilled walls and reinforced concrete frames.

Based on data collected from tests performed on the world’s only outdoor shake table, the engineers will come up with new seismic assessment tools and critical retrofit designs for these kinds of structures, which were not designed according to current standards. As part of the project, the engineers subjected a three-story structure with non-ductile reinforced concrete frames with unreinforced masonry infill walls to shaking representative of a series of different seismic events.

Infill walls can generally improve the seismic safety of a building up to a certain level of earthquake intensity depending on the number of walls present and their locations. Once the strength of the walls is exceeded by the earthquake force, the failure of such structures could be sudden and catastrophic as demonstrated in the recent UC San Diego tests. Due to the frame-panel interaction, the earthquake load resisting mechanism of these structures is complicated and it is difficult for engineers to assess their seismic resistance. The objectives of this project are to investigate the resistance of this type of structure under realistic seismic load conditions with large-scale tests and develop and calibrate reliable analytical models to assess their seismic performance.

"We will also look into retrofit methods to push the performance envelope of these structures. In reality, some of these structures may not have sufficient walls to resist earthquake loads or some walls may be missing in critical locations of a building. Hence, we need reliable means to assess and improve their performance," said Benson Shing, a structural engineering professor at the UC San Diego Jacobs School of Engineering, and the lead researcher on the project.

The recent seismic tests were conducted at the UC San Diego Englekirk Structural Engineering Center, which is about eight miles from the main university campus in La Jolla, and has the largest shake table in the country and the only outdoor shake table in the world. The concrete masonry structure is the largest of this type ever tested on a shake table.

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