The Concrete Coalition is a network of individuals, governments, institutions, and agencies with a shared interest in assessing the risk associated with non-ductile concrete buildings and developing strategies with which to mitigate that risk. The Coalition is a program of the Earthquake Engineering Research Institute, the Pacific Earthquake Engineering Research Center (PEER) at UC Berkeley, the Applied Technology Council and their partners, including the Structural Engineers Association of California, The American Concrete Institute, BOMA of Greater Los Angeles and the U.S. Geological Survey. With funding from the California Emergency Management Agency, the Concrete Coalition is helping California assess the size and scope of the potential risk by providing an educated estimate of the existing non-ductile concrete building stock.
For purposes of this project, the Coalition uses “pre-1980 concrete buildings” as a practical surrogate for “non-ductile concrete buildings.” The Coalition has now estimated the number of pre-1980 concrete buildings in the 23 counties (and two additional cities) with the highest seismicity and exposure, using sidewalk surveys, public records, data compiled by government agencies, and a regression model. Coalition members recognize that there is a large uncertainty with some of these numbers, particularly those generated by the regression model, and encourage volunteers throughout the state to conduct surveys in the cities with questionable data. Over time it is expected that these estimates will improve and as more city surveys are provided, the robustness of the regression model will improve.
Table 1 Estimated Number of Pre-1980 Concrete Buildings in the 23 Highest Seismicity and Exposure Counties of California
Not all of these buildings are collapse hazards or even prone to severe earthquake damage. The next level of inventory and loss estimation involves more careful study of specific buildings, applying our understanding of the riskiest structural conditions and details.
Under the leadership of Craig Comartin, a core group of volunteers managed the project, with the assistance of EERI staff. The project engaged more than 250 volunteers, from those who participated in early planning and project development meetings to those who spent weekends documenting building types in specific cities. A summer intern provided by PEER in 2009 gathered data for the regression model and interviewed volunteers about the nature of their estimates. A website was built to contain basic information on the building type as well as the individual reports from the cities (www.concretecoalition.org).