New PEER Report 2020/23: "Earthquake Damage Workshop"

December 16, 2020

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.


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.