Structural performance of out-of-plane moment connections in the minor strength axis of cross-laminated timber panels

The structural performance of panel-to-panel connections in the minor strength axis of cross-laminated timber (CLT) panels was investigated using experimental and numerical methods. These connections are crucial for achieving two-way span action in point-supported floors of a large structural grid. Five different connections were studied: plywood splines attached with inclined self-tapping screws (STS), glued plywood splines, T-joints, wood X-fix shear keys, and steel rebars. Based on 4-point and 3-point bending tests, the glued splines had the highest rotational stiffness, followed by the STS spline and T-joints. Steel rebar and X-fix connections had the lowest rotational stiffness. In terms of ductility, the glued spline exhibited brittle behavior, whereas others displayed a moderate level of ductility, while the steel rebars provided high ductility. The STS spline and glued spline had similar bending moment capacities, with the glued spline's capacity being affected by plywood quality. Steel rebars, T-joint, and X-fix connections had 70%, 50%, and 23% of this capacity, respectively. Subsequently, a numerical model, validated by the experimental results, was used to evaluate the connection demands for point-supported CLT floors in the minor direction for different dimensions and applied loads. Increasing the rotational stiffness from 500 to 5000 kNmrad⁻¹m⁻¹ significantly improved floor structural performance, reducing the deflection by about 50%. Further increasing rotational stiffness only yielded an additional decrease in deflection of 15%. With the tested configurations, both glued and screwed splines can provide 5000 kNmrad⁻¹m⁻¹, T-joints could potentially achieve this value, while an unreasonably high number of connectors would be necessitated for X-fix.