A Comparative Assessment of the Collapse Performance of Soft, Weak or Open-Front Wall Woodframe Buildings Retrofitted using Alternative Procedures

摘要

The main objective of this study is to conduct a performance-based assessment of a multi-unit residential woodframe buildings with open-front wall construction, to compare the incremental increase in collapse safety that results from applying three alternative retrofit procedures: (1) the basic structural guidelines of the LA Ordinance, (2) the FEMA P-807 guidelines and (3) ASCE 41-13. Three-dimensional structural models of the existing and retrofitted building cases are constructed in OpenSees and subjected to nonlinear static and response history analyses including incremental dynamic analysis to collapse. The building cases are evaluated using the FEMA P-695 guidelines using median collapse capacity as the measure of collapse safety. The median collapse capacity of the building case retrofitted using the ASCE 41-13 guidelines is 36% higher than the existing building case. 61% of the collapse cases occurred in the transverse direction in the existing building and all in the 1st story. In contrast, the collapse cases occurred equally in the longitudinal and transverse directions and all in the 2~(nd) story for the ASCE 41-13 retrofitted building case. For the structural model that incorporated the LA Ordinance retrofit, the median collapse capacity increased by 14%. The FEMA P807 retrofit had the lowest impact on collapse safety with an 11% increase in the median collapse capacity.