Flexural Performance of Splice Connections in Cross-Laminated Timber

Abstract

This study demonstrates the moment resistance performance of various splice connections of cross-laminated timber (CLT) subjected to flatwise bending. A total of 33 samples in two groups (half-lapped and single-splined) were tested under four-point bending. The influence of fastener types on the half-lapped connections was investigated. Additionally, different lap lengths were considered to understand the influence of lap length on different fastener types. Steel plates with two different thicknesses and plywoods were attached with bolts onto the bottom face only to make the single spline connections. Additionally, plywoods were attached to the CLT members in two ways: (i) with the bolt only and (ii) glue plus bolts. The effect of bolt diameters on the spline connections was also examined, and the connections were tested along both the major and minor axes. To determine the characteristic values of the resistance properties, a statistical analysis was carried out following EN 14358:2016. The results indicate the bolted lap connections experience plastic deformations, whereas the screwed lap connections exhibit relatively linear behaviour until failure. The bolted and screwed lap connection with a lap length of 100 mm showed 39% and 33% higher moment capacity, respectively, than that with a 75 mm lap length. Additionally, the rotational rigidity and ductility of the lap connections increase with the increase in lap length. Irrespective of lap lengths, the bolted lap connections show higher moment capacity, support rotation and ductility, but lower rotational rigidity than screwed lap connections. An increase in bolt diameter increases moment capacity but decreases rotational rigidity. Compared to the plywood spline connections, the steel spline connections showed approximately 24%, 5% and 73% higher moment capacity, rotational rigidity and ductility, respectively. Additionally, the plywood spline connections without glue performed better than glued connections. Overall, compared to the half-lapped connections, the single-spline connections showed better performance.