Seismic performance and retrofit for tilt-up concrete buildings in Mid-America

Seismic risk is a concern in the Mid-America region because of the series of severe earthquakes that occurred in the New Madrid Seismic Zone in 1811-1812. Many existing concrete structures in this area are considered to be vulnerable in a moderate to significant seismic event because they were not designed for the seismic provisions of the current International Building Code. Seismic performance assessment and fragility analysis are used to evaluate the seismic vulnerability of existing structures. Based on these analyses, possible retrofit techniques are considered to reduce structural damage and corresponding losses. Based on available inventory data for Memphis, Tennessee, tilt-up concrete buildings are the most common type of concrete structure in Memphis. Tilt-up construction is commonly used for low-rise industrial buildings and has several advantages, including a large open space and low construction costs. However, many tilt-up concrete buildings were damaged during previous earthquakes in the Western U.S. and other regions. Typical damage included collapse of wall panels and roof diaphragms due connection failures. To improve seismic performance of tilt-up concrete buildings, several seismic retrofit techniques are currently used including the addition of anchors to strengthen the roof-to-wall connections.