Experimental investigation of the lumber-plybamboo-lumber screwed connections used in midply shear walls

Common midply shear walls constructed with wood-based mid-sheathing panels and nails usually exhibit substantial sheathing edge-tear and nail withdrawal failures, which will significantly limit the midply shear wall performance. This paper introduces an approach to prevent these connection failures, namely employing plybamboo panel and wood screw as middle sheathing and fastener, respectively. A preliminary experimental study on six groups of lumber-plybamboo-lumber screwed (LPLS) connections extracted from such improved midply shear walls were conducted, taking account of variables in terms of sheathing thickness and loading direction to the framing grain. Another three groups with Oriented strand board (OSB) mid-sheathings were tested for comparison. Test results show that the combined use of plybamboo panel and wood screw in the LPLS connections can effectively reduce the sheathing edge-tear and fastener withdrawal failures, and results in an over 70% increase in ultimate strength in comparison to the double-shear nailed connections with wood-based sheathing. However, the LPLS connections showed no advantage in elastic stiffness and ductility compared to the double-shear nailed connections with wood-based sheathing. The ultimate strength and ultimate displacement of the LPLS connections subjected to cyclic loading are 1.0–25.8% and 39.1–58.2% less than those of monotonically loaded connections, respectively, due to premature screw fatigue. The European Yield Model can reasonably predict the failure mode of the LPLS connections, but will underestimate the ultimate strength by 12–44%, probably due to underestimating the plybamboo embedment strength and ignoring the friction between plybamboo sheathing and SPF lumbers. The combined use of plybamboo panel and wood screw has great potential of being used in wood construction.