PEER has just published Report No. 2020/19: "Cripple Wall Small-Component - Test Program: Comparisons," 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, Universiity of California, San Diego; and Kelly Cobeen, Wiss, Janney, Elstner Associates, Inc.
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 (WG4): Testing, whose central focus was to experimentally investigate the seismic performance of retrofit and existing cripple walls. Amongst the body of reports from WG4, in the present report, a suite of four small cripple wall test phases, in total 28 specimens, are cross compared with varied exterior finishes, namely stucco (wet) and non-stucco (dry) exterior finishes. Details representative of era specific construction, specifically the most vulnerable pre-1960s construction are of predominant focus in the present effort. Experiments involved imposition of combined vertical loading and quasi-static reversed cyclic lateral load onto cripple walls of 12 ft in length and 2 ft or 6 ft in height. All specimens in this report were constructed with the same boundary conditions and tested with the same vertical load. Parameters addressed in this report include: wet exterior finishes (stucco over framing, stucco over horizontal lumber sheathing, and stucco over diagonal lumber sheathing); and dry exterior finishes (horizontal siding, horizontal siding over diagonal sheathing, and T1-11 wood structural panels) with attention towards cripple wall height and the retrofit condition. The present report provides only a brief overview of the test program and setup; whereas a series of three prior reports present results of test groupings nominally by exterior finish type (wet versus dry). As such, herein the focus is to cross compare key measurements and observations of the in-plane seismic behavior of all 28 specimens.