Response of an instrumented masonry shear wall building with flexible diaphragms during the Loma Prieta Earthquake

The subject structure of this study is a two-story office building located at Palo Alto, California. The structure was built in 1974. Recorded peak ground accelerations were as high as O.21g and peak roof accelerations as high as O.S3g. Considerable amplifications of the peak accelerations between the ground and the roof were observed. The building withstood the Lorna Prieta Earthquake with little damage. Masonry construction used in Northern California is similar throughout the United States. Because moderate earthquakes are expected east of the Rocky Mountains, the response of the office building at Palo Alto can help foretell the earthquake hazard in the eastern and midwestern United States. The ground motions recorded at the office building at Palo Alto represent an upper bound for assessing possible hazards associated with similarly constructed buildings in the eastern United States. Since the building was not appreciably damaged, even with these high accelerations, there is hope that similar historic buildings across the nation may survive a future earthquake. However, such extrapolation is not warranted unless a detailed investigation is done to examine the reasons for the superior performance. The objectives of this study are the following: 1) Investigate the reasons of the survival of the office building at Palo Alto with the use of both simplified and state-of-the-art methods. 2) Assess the effectiveness of a discrete MDOF dynamic model on the seismic evaluation of this building and similar masonry buildings with flexible diaphragms. 3} Correlate the recorded, observed and computed response at the office building at Palo Alto with estimates of dynamic response and prescribed strength by state-of-the-art masonry and seismic codes.