Withdrawal behaviour of mechanical fasteners in laminated bamboo lumber

Abstract

Experiments were conducted to evaluate the effect of shank diameter, shank type, penetration depth and insertion direction on the nail-holding behaviour of laminated bamboo lumber (LBL). It was found that the shank type of the fastener had a significant effect on the failure mode. Nails, with a smooth shank, were pulled out directly from the LBL without other visible damage. However, when screw fasteners were used, bamboo fibres around the screws were torn. The load–slip curves of the specimens were linear up to the maximum load and the relative slip between the fasteners and the LBL was small at this stage. However, the post-peak performance of both nails and screws varied significantly on the descending portion of the curves. Specimens with nails inserted parallel to the grain showed the smallest nail withdrawal capacity, followed by specimens with nails inserted in the tangential and radial directions. As expected, the withdrawal capacity of the specimens increased linearly with an increase in embedment depth and shank diameter. The experimental load–slip curves were compared with existing theoretical models and the most suitable models to predict the load–slip relationship of the withdrawal behaviour of nails and screws in LBL were identified.