A Methodology for Estimating Seismic Retrofit Costs
Juan F. Fung, David T. Butry, Siamak Sattar, Steven L. McCabe
Presidential Executive Order 13717 (EO 13717), Establishing a Federal Earthquake Risk Management Standard, encourages federal agencies to enhance resilience...[to] future earthquakes by evaluating and retrofitting existing federal buildings based on current existing building codes. However, while guidance on evaluation and retrofit practices is readily available, a standard approach to estimating retrofit costs does not exist. Moreover, the absence of easily obtainable estimates can make retrofits prohibitive for decision-makers. This paper develops a cost-estimating methodology for seismic retrofits that (1) captures the essential factors that drive seismic retrofit costs, such as building construction and square footage; and (2) is reproducible using data available to decision-makers. The methodology builds on FEMA 156 and 157, Typical Costs for Seismic Rehabilitation of Existing Buildings, Volumes 1 and 2. A series of regression models is fit to the data used for the FEMA reports, with the models varying in the level of data required; e.g., a decision-maker may not have information on building construction for each asset in their inventory. Thus, the trade-off from estimating retrofit costs subject to data limitations can be quantified in terms of prediction error, providing decision-makers with a set of options for estimating costs together with a measure of predictive performance. We find that a simple model, in terms of data requirements, can deliver reliable predictions.