Structural performance of adhesively bonded and hybrid screw-adhesive CLT panel-to-panel floor joints

Cross-laminated timber (CLT) panels are increasingly used in floor construction with the individual panels connected with self-tapping screws (STS) through surface spline or butt joints. These joints provide limited rotational stiffness in the out-of-plane direction. An alternative is the proprietary TS3™ technology which uses adhesive bonding to create near-rigid joints, which allow to better utilize the two-way resistance of CLT panels. However, TS3 joints fail in a brittle manner. The objective of the study presented herein was to evaluate the performance of STS and TS3 joints and to explore whether a hybrid solution is a viable alternative. To achieve this objective, screwed, TS3, and hybrid TS3-screw joints in the major and minor strength directions of CLT panels were investigated using out-of-plane three-point and four-point bending and in-plane shear tests. These tests demonstrated that the TS3 joints in the minor strength axis achieved similar effective bending stiffness and strengths like CLT panels, STS joints exhibited ductile behaviour, and although the STS in the hybrid solution could not prevent the brittle failure of the adhesive bond, they provided a secondary resistance mechanism after TS3 failure. • Adhesive bonding provides high rotational stiffness in CLT panel-to-panel floor joints. • Adhesive bonding in the minor-strength-axis provides similar strengths like CLT panels. • Hybrid screwed-glued joints provide a secondary resistance mechanism.