Long-Term Bending Behaviour of Adhesive CLT Panel-to-Panel Connections

The growing interest in point-supported cross-laminated timber (CLT) floor systems and the desire for open space designs led to the development of on-site adhesive solutions such as the TS3™ system, which joins panels along their minor-axis direction. Load duration affects the design of such floors at both the serviceability and the ultimate limit states. In the Canadian Standard for Engineering Design in Wood (CSA O86), load-duration effects are considered via a factor that lowers the resistance and a creep factor (KCr = 2.0) that increases the deflection; yet, the long-term behaviour of adhesive connections between CLT panels has not been tested. Here, creep was monitored for fourteen months on TS3™-connected CLT panels loaded in flat-wise bending under dry service conditions. The creep factors were on average below 1.8, not exceeding the CSA O86 creep factor. The residual short-term resistance and apparent bending stiffness after long-term loading were determined as 102% and 108%, respectively, of a reference group, demonstrating that long-term loading had no detrimental effect on the short-term performance. These findings are based on mean-level comparisons for the tested CLT species and stress grade and should be regarded as indicative of the long-term behaviour of TS3™-connected CLT panels in dry indoor conditions.