Impact of engineering modeling assumptions on assessing seismic resistance of Montgomery block building

The Montgomery Block building is used as a case study to assess the effectiveness of conventional analysis methods commonly used by practicing engineers throughout North America when conducting seismic evaluation work to predict the seismic performance of unreinforced masonry (URM) buildings. This building predominantly constructed of URM pier-and-spandrel facades and URM shear walls was built in 1853 and survived the 1906 San Francisco Earthquake despite being roughly 15 km from the San Andreas Fault that ruptured in 1906. It is found that the impact of engineering modeling assumptions can be of nearly an order of magnitude for buildings of that type, depending on the structural model selected by the engineer. Of all the conventional modeling procedures considered in this paper, it is found that only the special procedure of the Uniform Code for Building Conservation (UCBC) comes close to predicting the observed seismic response. However, some extensions of the more conventional modeling procedures are useful in demonstrating the potentially beneficial period elongation that accompanies structural strength degradation as damage progresses.