Assessing Modeling Complexities on the Seismic Performance of a Short Period Instrumented Hospital

Low-rise, short-period buildings dominate the construction in the United States including residential, recreational, and critical, including hospital, facilities. Previous analytical studies have indicated that these structures behave poorly under seismic excitation compared to buildings with longer fundamental periods; however, such trend has not been observed in previous earthquake events. In this paper, a case study is considered to better evaluate the dynamic response of short-period light-frame wood buildings and help identify the modeling parameters and level of complexity required to accurately capture their dynamic response. For this purpose, a portion of the Twin Cities Community Hospital, located in Templeton, California (called herein the Templeton Hospital), was considered. This one-story light-frame wood building with a large roof diaphragm layout did not suffer any structural damage during the 2003 San Simeon earthquake despite being subjected to intense ground shaking. The Templeton Hospital was located at a distance of 38 km from the epicenter of the 2003 M6.5 San Simeon earthquake. The hospital structure was instrumented during this earthquake event, and recorded motions at various locations in the building are available in the public domain. Nonlinear numerical models of the selected portion of the Templeton Hospital building were developed in this study. These models incorporated varying levels of complex behaviors, so the influence of these behaviors on the level of correlation between predicted and recorded responses was assessed. Nonlinear response time history analyses were performed for each of the models developed under the ground motions recorded at the Templeton Hospital site during the 2003 San Simeon earthquake. Comparisons between predicted and recorded response time histories at various locations in the building were used to evaluate the effects of different levels of modeling complexity and to determine the minimum level of complexity needed to accurately reproduce the recorded data for this building. The results of this study indicated that the modeling of the in-plane diaphragm flexibility is the most crucial parameter needed to be accounted for in the analyses in order to accurately capture the observed response of this instrumented hospital during the San Simeon earthquake. It should be noted that the peak relative displacement measured for the Templeton Hospital was almost in the elastic range and, therefore, the findings of this study are focused on near-elastic response and not the full range of nonlinear response.