Seismic vulnerability of masonry facades in Texas and Oklahoma regions

In the Oklahoma and Texas area, an increase in human-induced seismic activity has resulted in millions of dollars of damage in the region, primarily to residential homes. The most common damage is to chimneys and masonry veneers. This study focuses on better understanding and evaluating the fragility of brick veneers to the human-induced earthquakes that have been experienced in this region. A computational wall model was developed based on previous experimental and computational research on non-seismically detailed brick veneers from the literature. A suite of ground motion recorded in Texas, Oklahoma, and Kansas since 2010 was provided by geotechnical engineering researchers at the University of Texas at Austin and was used in this study to represent the seismic hazards expected in the region. Fragility curves were developed using the experimentally validated computational models, in which ground motion uncertainty was accounted for in the suite of ground motions used in the fragility analysis. To evaluate the effects of different seismic hazards on brick veneer fragility, ground motion ensembles representing both the New Madrid and the Texas-region seismic events were considered. Fragility curves were also generated using brick veneer models with variations in brick tie types and configurations to evaluate the effects of veneer anchorage detailing and retrofit strategies on seismic performance. The study has shown that when trying to predict the fragility of masonry façade, it’s important to utilize ground motions from the region and seismic hazard of interest, as it has an impact on the relative fragility of the wall model because of varying characteristics. Although using a code compliant gauge for veneer ties is ideal, it was shown that the most critical part of installation is including ties in the upper portion of a wall panel. If it is desired to strengthen an existing brick veneer wall, without having to reinstall the wall, adding additional anchorage at the top of the wall will still provide increased seismic resistance, which may be a good course of action if it is suspected that there are ties that are missing, have corroded, or were not installed properly.