Experimental and analytical assessment of the combined in-plane bending-shear behavior of timber frame walls

Abstract

As timber buildings grow taller, understanding the mechanical behavior and robustness of multi-story timber structures is increasingly important. In Europe, Eurocode 5 governs their design but offers little guidance for failure scenarios. In particular, it lacks provisions for diaphragm walls under combined bending and shear forces that can occur during events like wall loss. This study investigates the behavior of such walls through experimental and analytical methods. An experimental campaign was conducted using eleven timber frame walls with OSB sheathing, fastened with either screws or staples. Five walls underwent four-point bending tests, two were tested under shear, and four experienced combined bending-shear loading. In the latter, a vertical preload was applied before monotonic shear loading to failure. Walls fastened with staples showed ductile failure with significant yielding, whereas walls fastened with screws exhibited brittle failure via screw tear-out. Shear failures primarily occurred at sheathing-to-framing connections in the lower rail. Under combined loading, increased vertical preload reduced shear capacity, displacement at failure, and force at yielding. The experiments supported an analytical model developed to estimate in-plane bending strength and maximum allowable shear load in combined loading scenarios. The model conservatively predicted the behavior of walls fastened with screws in bending but overestimated the strength of walls fastened with staples. For combined loading, the model provided a conservative estimate of maximum shear resistance.