PEER has just published Report No. 2020/23: "Earthquake Damage Workshop," a report for the "Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings" Project. It was authored by Kylin Vail and Bret Lizundia, Rutherford + Chekene; David P. Welch, Stanford University; and Evan Reis, Reis Consulting.
Visit the PEER publications page to download a free color pdf of the document.
Abstract
This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.”
The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors.
This report is a product of Working Group 6 (WG6): Interaction with Claims Adjustors & Catastrophe Modelers and focuses on a damage workshop effort undertaken to provide repair estimates of representative damaged single-family wood-frame case study buildings to compare the differences in costs between houses with and without retrofits to cripple walls and sill anchorage. At the request of the CEA, 11 experienced claims adjustors from insurance companies volunteered to provide the estimates. Electronic cost estimation files for each case study building were developed by the PEER–CEA Project Team using the Verisk Xactware Xactimate X1 platform and provided to the claims adjustors to complete their estimates. These adjustor estimates served as the baseline for comparison against the FEMA P-58 [FEMA 2012] methodology used on the project for loss estimation. The term “damage workshop effort” is used to emphasize that the scope of work included not just a successful workshop meeting, but the broader development of a damage description package describing case studies and associated Xactimate descriptions before the workshop meeting and revisions after it, two rounds of estimates and survey question responses by adjustors, interpretation and clarification of the estimates for consistency, and synthesizing of estimate findings and survey responses into conclusions and recommendations.
Three building types were investigated, each with an unretrofitted and a retrofitted condition. These were then assessed at four levels of damage, resulting in a total of 24 potential scenarios. Because of similarities, only 17 scenarios needed unique Xactimate estimates. Each scenario was typically estimated by three to five adjustors, resulting in a final total of 74 different estimates.