Experimental test of coupling effect on CLT hold-down connections

Abstract

This paper investigated the coupling effect of tension and shear loading on Cross Laminated Timber (CLT) hold-down connections through experimental tests. Monotonic and cyclic tests of the connections were carried out in tension with 3 different levels of co-existent constant shear forces, and in shear with 5 different levels of co-existent tension forces. Failure mode, hysteresis loops, strength and stiffness, equivalent viscous damping and strength degradation, energy dissipation, and coupling effect were described and discussed in details. The results show co-existent shear load weakened both the axial loading capacity and energy dissipation capacity at large vertical displacement; small co-existent tension load (0–20 kN) strengthened the shear behaviour while higher levels of co-existent tension load (30–60 kN) decreased the shear capacity and energy dissipation capacity rapidly at large lateral displacement. The research finds that, nails travelling in the gap within the wood embedment received resistance due to the co-existent force in the perpendicular direction under bi-axial loading, which caused the coupling effect. The study gives a better understanding of hysteretic behaviour of hold-down connections for CLT where rocking motions occur, and provides reliable data for future numerical analysis of CLT structures.