Testing and nonlinear modelling of industrialized light-frame wooden diaphragms including optimized nailing and nonstructural sheathing

Abstract

This article presents the outcomes of a large project towards the investigation of the lateral performance of full-scale industrialized light-frame wooden diaphragms. 10 full-scale diaphragms of 3.6 m by 2.4 m were tested under in-plane lateral loading (monotonic and cyclic), considering different sheathing, nailing, and framing. Besides, the behavior of bare slabs (without any sheathing), gypsum finishes and the potential benefits of using optimized nailing patterns instead of regularly spaced nailing was also studied. Experimental tests were non-linearly modeled using the modified Steward hysteresis model (MSTEW) and MCASHEW software. Experimental strength and stiffness results proved to be consistent with those proposed by other international campaigns, and in particular, the design principles of SDPWS fitted well with the obtained results. However, chord tensions were 30 % greater than the ones obtained by principles of engineering mechanics, which might be explained by eccentric tensile load transfer. As expected, the behavior of both sawn lumber and I-joist framed diaphragms was mainly controlled by nailing. In fact, optimized nailing patterns allowed to equal the peak capacity, increase by 20 % stiffness and 75 % ductility with 8 % less nails. Screwed gypsum finishes increased the peak capacity and stiffness by 15 %, and 20 %, respectively. The modelling approach – mainly used only in shear walls in previous investigations – proved its capability of finely reproducing the behavior of all diaphragm configurations. The numerical results were also in good agreement with the prescriptions of the SDPWS standard.