New PEER Report 2020/16: "Cripple Wall Small-Component Test Program: Wet Specimens I"

December 15, 2020

PEER has just published Report No. 2020/16: "Cripple Wall Small-Component Test Program: Wet Specimens I," 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 Brandon Schiller and Tara Hutchinson, University of California San Diego; and Kelly Cobeen, Wiss, Janney, Elstner Associates, Inc.

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 4: Testing and focuses on the first phase of an experimental  investigation  to  study  the  seismic  performance  of  retrofitted  and  existing  cripple  walls  with  sill  anchorage.  Paralleled  by  a  large-component  test  program  conducted  at  the  University of California [Cobeen et al. 2020], the present study involves the first of multiple phases of  small-component  tests  conducted at the UC San Diego. Details  representative  of  era-specific  construction, specifically the most vulnerable pre-1960s construction, are of predominant focus in the  present  effort.  Parameters  examined  are  cripple  wall  height,  finish  materials,  gravity  load,  boundary conditions, anchorage, and deterioration. This report addresses the first phase of testing, which consisted of six specimens. Phase 1 including quasi-static reversed cyclic lateral load testing of six 12-ft-long, 2-ft high cripple walls. All specimens in this phase were finished on their exterior with stucco over horizontal sheathing (referred to as a “wet” finish), a finish noted to be common of  dwellings  built  in  California  before  1945.  Parameters  addressed  in  this  first  phase  include:  boundary  conditions  on  the  top,  bottom,  and  corners  of  the  walls,  attachment  of  the  sill  to  the  foundation,  and  the  retrofitted  condition.  Details  of  the  test  specimens,  testing  protocol,  instrumentation; and measured as well as physical observations are summarized in this report. In addition, this report discusses the rationale and scope of subsequent small-component test phases. Companion reports present these test phases considering, amongst other variables, the impacts of dry finishes and cripple wall height (Phases 2–4). Results from these experiments are intended to provide an experimental basis to support numerical modeling used to develop loss models, which are  intended  to  quantify  the  reduction  of  loss  achieved  by  applying  state-of-practice  retrofit  methods  as  identified  in  FEMA  P-1100, Vulnerability-Base  Seismic  Assessment  and  Retrofit  of  One- and Two-Family Dwellings.