Abstract
The purpose of this study is to evaluate the seismic performance of existing and rehabilitated wood floor and roof diaphragms in typical pre-1950's, unreinforced masonry (URM) buildings found in the Central and Eastern portions of the United States. Current guidelines have challenging criteria for practicing engineers to seismically rehabilitate URM structures with limited information on how to achieve an acceptable retrofit, particularly for the diaphragms. This research focuses on two major objectives: (1) assessing the adequacy of current seismic rehabilitation guidelines for evaluating existing wood diaphragms in pre-1950's URM buildings and for designing necessary retrofits; and (2) evaluating the effect of diaphragm retrofits, as designed by the FEMA guidelines, on the overall seismic response of URM structures. The study utilizes current guidelines and tools available to practicing engineers to evaluate two existing wood diaphragms in URM buildings for seismic demands and design appropriate rehabilitations for these diaphragms. After evaluating each available analysis, the linear static procedures from the FEMA 273 and FEMA 356 guidelines are used for the evaluation of two case study buildings. Lastly, a parametric study is performed that focuses on observing the variation in system response as the diaphragm in a two-story URM prototype structure is retrofitted. The retrofit includes strengthening the in-plane strength of the diaphragms and improving the connection of the diaphragm to the URM walls. This impact of retrofit is evaluated for several existing conditions of the masonry walls. Conclusions are drawn from observations of the changing behavior of the system. The parameters used in this part of the study approximate realistic values for existing buildings based on the FEMA guidelines. This study provides an assessment of the usefulness of retrofitting the diaphragms in URM structures and identifies areas where additional information is needed in the seismic rehabilitation guidelines for a thorough evaluation of similar buildings.
Grubbs, Amber Jo (2002). Seismic rehabilitation of wood diaphragms in unreinforced masonary buildings. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2002 -THESIS -G79.