Nonstructural Components and Systems
In 2016 alone, over 500 M3+ earthquakes have occurred in the Central and Eastern parts of the United States, while in 1973-2008 there were only an average of 21. Most of these recent events are not naturally occurring, but rather, are human-induced due to oil and gas industry activities. In 2017, these induced earthquakes occurred over broader areas than they had in previous years. Few of the 7 million people impacted by these events have previously dealt with the threat of earthquakes. According to USGS, the likelihood of experiencing a damaging earthquake in parts of the Central U.S., such as Oklahoma, is now comparable with that in California. In fact, much of the observed damage following the 2011 M5.7 Prague, OK, the 2016 M5.8 Pawnee, OK, and the 2016 M5.0 Cushing, OK earthquakes includes masonry veneer and chimney failures in residential homes, which has generated millions of dollars of insurance claims. Unlike areas of the West Coast where construction practices have changed with improved knowledge of seismic effects, these areas are most at risk to experience damage, particularly nonstructural damage, in existing buildings, which were not designed with consideration of earthquake activity. In addition, national building code committees are unsure of how to treat this new form of hazard, largely due to lack of information and uncertainty associated with predicting hazards tied to future human activity. This presentation will discuss part of a multi-disciplinary project sponsored by Texas State legislature, through the TexNet Seismic Monitoring Program and the Center for Integrated Seismicity Research (CISR) at the University of Texas at Austin focusing on the fragility of residential construction, and more specifically masonry veneers, to induced earthquake hazards. The masonry veneer study builds on past research, utilizing experimentally-validated computational models to evaluate sensitivity of the façade fragility due to the induced earthquake characteristics, as well as changes or issues in veneer construction. The ground motions used in this study are selected from over 200 recorded earthquakes in the Texas, Oklahoma, and Kansas region. The presentation will discuss the effects of various seismic hazards on masonry veneer fragility by comparing results from different ground motion ensembles (e.g. recently recorded Oklahoma ground motions, West Cost ground motions of similar magnitude, ground motions representative of natural Oklahoma seismic hazards from the New Madrid region, etc.). The presentation will also discuss how common masonry veneer construction issues (e.g., use of non-code compliant brick ties or tie spacing, which are common of residential construction) and retrofit strategies impact seismic veneer performance. These fragility curves will then be combined with area-specific ground motion prediction models to evaluate the regional extent of damage expected from induced seismic events. The target audience of this presentation will be structural design engineers and construction professionals, especially those focusing in the residential sector or who practice in regions affected by induced earthquake hazards. Additionally, earthquake engineering researchers interested in various topics, including the impacts of induced seismicity on the built environment and Central US seismic risk, will be interested in this presentation.