Withdrawal behaviour of mechanical fasteners on laminated bamboo lumber

Experiments on connections were done 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 is found that shank type of fasteners has significant effect on failure modes. Nails were pulled out directly from the LBL without other visible damage due to smooth shank, while the bamboo fibers around the screws were tore under the action of screw thread. The load-slip curves of specimens are linear up to the maximum load and relative slip between the fasteners and LBL is small at this stage. However, the post-peak performance of nails and screws varies significantly on the descending portion of the curves. The specimens with nails inserted parallel to grain have the lowest withdrawal capacity, followed by those of the tangential and radial directions. As expected, the withdrawal capacity of the specimens increases linearly with the increase of the embedment depth and shank diameter. The measured load-slip curves were recorded and compared with the existing theoretical models. Results show that the Yuan and Ling model can be used to predict the load-slip relationship of the withdrawal behaviour of nails and screws in LBL respectively.