Investigation of the shear resistance performance of cross-laminated timber connections with self-tapping screw applications

The effects of connection types and nailing angles on the shear resistance performance of cross-laminated timber (CLT) connections using self-tapping screws were investigated in the study. The 5-layer- and 5-ply-CLT connections with heterogeneous-grade construction were made using Cryptomeria japonica plantation timber, and were also mixed with southern pine (Pinus spp.). Results showed that the maximum shear capacity, yield shear load, and initial stiffness of a CLT surface spline connection were 16, 13, and 22%, respectively, of a CLT butt connection. The maximum shear capacity, yield shear load, and initial stiffness of a CLT half-lap connection were 63, 64, and 38%, respectively, of a CLT butt connection. As to effects of nailing approaches, the maximum shear capacity of connections fastened with self-tapping screws at angles of either 90° or 45° were 40% of that with double angles of a 30°-45° approach. The yield shear loads obtained from both 90° and 45° nailing approaches were 30 and 47%, respectively, of that with double angles of the 30°-45° approach. Values of initial stiffness were 11 and 35%, respectively, of that with double angles of the 30°-45° approach. Improvement in the shear resistance was found in a butt connection fastened with self-tapping screws when southern pine laminae were used for outer layers of the CLT. CLT connections fastened with self-tapping screws were classified based on the obtained ductility. The connection assembled with a surface spline was classified into the high-ductility category, the CLT butt connection was in the moderate-ductility category, and the CLT half-lap connection was in the low-ductility category. © 2019 Taiwan Forestry Research Institute. All rights reserved.