Experimental and Numerical Assessment of Woodframe Sheathing Layer Combinations for Use in Strength-Based and Performance-Based Design

Abstract

Woodframe buildings are unique in that the nonstructural finishes such as gypsum wall board and stucco provide significant stiffness and strength relative to the lateral force resisting system, e.g., wood shear walls. Wall finishes, or components within a woodframe wall subassembly, can consist of multiple layered modern and/or archaic elements such as wood planks, drywall, plaster on lathe, stucco, or plywood. There exist significant differences in ductility among these materials, raising questions about how best to superimpose single-degree-of-freedom hysteretic models or backbone curves during nonlinear time history analysis or when combining backbone curves for design and retrofit. This paper presents the method and results of an experimental study of 18 walls installed with one, two, or three of the previously described finishes. Testing was performed to determine the best approach to add the sheathing layers numerically when combining the backbone curves for analysis and design. Nonlinear dynamic analyses were conducted to quantify the difference between the behavior of the combined sheathing test and the superimposed single layer sheathings.