RAPID/Collaborative Research: Study of Soil-Structure Interaction Effects on Behavior and Damage to Structures in Washington, DC, during the August 23, 2011 Earthquake

Lehigh University, Bethlehem PA

Investigators

Abstract

The Virginia earthquake of August 23, 2011 occurred within a regionally well-established zone of earthquake activity, the "Central Virginia Seismic Zone". This area has produced small and moderate damaging earthquakes since at least as far back as the 18th century. The magnitude of the August earthquake was 5.7, and the epicenter was located in Louisa County, about 135 km southwest of Washington DC. Significant damage occurred to a number of structures in Washington, DC, including the Smithsonian Institute's Museum Support Center (MSC) and the Washington National Monument. Damage to both structures was unexpected. That is, there was a marked uptick in the shaking intensity and damages in the Washington, DC, region relative to other areas located much closer to the epicenter. This research is to investigate reasons that help explain this trend by performing detailed analyses of two important facilities that were damaged. The MSC, a large warehouse complex that serves as the main storage facility for the Smithsonian, is typical of many building systems in the eastern US. The Washington Monument is the world's tallest stone structure and the world's tallest obelisk, while also being of national historical significance. Preliminary analyses indicate that the damage to both of these structures is related to the interaction of key engineering factors, including their dynamic structural characteristics and the specific geologic and geotechnical (soil) conditions underlying the Washington, DC, area. The study is a collaborative effort between researchers at Lehigh University, Virginia Tech, and the US Geological Survey (USGS). Research activities involve both structural and geotechnical tasks. The structural engineering activities include gathering perishable damage data from the MSC and Washington Monuments, performing field vibration tests to establish the dynamic characteristics of these two structures, and developing advanced numerical models. The main geotechnical tasks involve working with USGS to perform field tests to characterize the dynamic behavior of the sites, and developing a detailed numerical simulation of the earthquake shaking that occurred during the magnitude 5.7 earthquake. Collectively, the researchers will use the structural models, dynamic site parameters, and ground shaking simulations to perform detailed analyses of both facilities to explain the observed damages during the magnitude 5.7 earthquake. The findings will then be extended by using the models to simulate different earthquake scenarios to better understand and communicate the potential impacts of the magnitude 5.7 or an even larger magnitude earthquake occurring closer to Washington, DC, or other populated areas in the region. Results will be shared with engineers, stakeholders, and decision makers in the engineering community and beyond. The two structures being studied represent a unique opportunity to analyze the behavior of east-coast US structures not designed to resist earthquakes. Our in-depth study will be insightful to the profession for establishing the vulnerability of eastern US structures to earthquake hazards and needs for renovation to ensure their resiliency. Of particular importance, this work will promote advancements in building codes and design procedures specific to the eastern US.