New PEER Report 2020/17: "Cripple Wall Small-Component Test Program: Dry Specimens"

December 15, 2020

PEER has just published Report No. 2020/17: "Cripple Wall Small-Component Test Program: Dry Specimens," 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  measures  and  documents  seismic performance of wood-frame houses with cripple wall and sill anchorage deficiencies as well  as  retrofitted  conditions  that  address  those  deficiencies.  Three  primary  tasks  support  the  earthquake  loss-modeling  effort.  They  are:  (1)  the  development  of  ground  motions  and  loading  protocols that accurately represent the diversity of seismic hazard in California; (2) the execution of a suite of quasi-static cyclic experiments to measure and document the performance of cripple wall  and  sill  anchorage  deficiencies  to  develop  and  populate  loss  models;  and  (3)  nonlinear  response history analysis on cripple wall-supported buildings and their components.

This  report  is  a  product  of  Working  Group  4:  Testing,  whose  central  focus  was  to  experimentally investigate the seismic performance of retrofitted and existing cripple walls. This present report focuses on non-stucco or “dry” exterior finishes. Paralleled by a large-component test  program  conducted  at  the  University  of  California,  Berkeley  (UC  Berkeley)  [Cobeen  et  al.  2020], the present report involves two of multiple phases of small-component tests conducted at University  of  California  San  Diego  (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 style, gravity load, boundary conditions, anchorage, and deterioration. This report addresses all eight specimens in the second phase of testing and three of the six specimens in the fourth phase of testing. Although conducted in different testing phases, their results are combined here to co-locate observations regarding the behavior  of  all  dry  finished  specimens.  Experiments  involved  imposition  of  combined  vertical  loading and quasi-static reversed cyclic lateral load onto eleven cripple walls. Each specimen was 12 ft in length and 2-ft or 6-ft in height. All specimens in this report were constructed with the same boundary conditions on the top, bottom, and corners of the walls. Parameters addressed in this report include: dry exterior finish type (shiplap horizontal lumber siding, shiplap horizontal lumber  siding  over  diagonal  lumber  sheathing,  and  T1-11  wood  structural  panels),  cripple  wall  height, vertical load, and the retrofitted condition. Details of the test specimens, testing protocol (including  instrumentation),  and  measured  as  well  as  physical  observations  are  summarized.  Results from these experiments are intended to support advancement of numerical modeling tools, which  ultimately  will  inform  seismic  loss  models  capable  of  quantifying  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.