Experimental Investigation of Cross-Laminated Timber Connections with Glued-In Rods under Monotonic and Cyclic Loading

Glued-in rods are proficient and high-performance connectors, finding application in the construction of new timber edifices as well as retrofitting of pre-existing timber structures. Given the prevalence of high-rise timber constructions facilitated by the advent of cross-laminated timber (CLT), there exists an opportunity for the incorporation of glued-in rods in the connectivity solutions for these load-bearing structural elements. This study examines the empirical behavior of CLT connections employing multiple glued-in rods. To achieve this objective, comprehensive experiments were conducted, involving full-scale tests on specimens subjected to both monotonic and cyclic loading conditions. The investigation included variations in the embedment lengths of the rods (250 and 350 mm) as well as their orientations with respect to the wood grain (parallel, perpendicular, and interposed amid layers). The monotonic test results showed that glued-in rods embedded on the edge of the CLT could provide high-capacity connections. The angle at which the rod was oriented relative to the wood grain had an impact on both the failure mode and the shape of the force-displacement curve in the connections. To calculate the pull-out strength of the glued-in rods anchored in CLT, a design equation is proposed based on the shear strength of the bondline. Additionally, a comparative investigation was performed to study the effect of the reinforcement by screws on the connections strength under monotonic loading in tension and in compression. Moreover, it was observed that glued-in rod connections keep their elastic properties until failure under cyclic loading. The results obtained from this research exemplified that this specific connection type could present a reliable and sturdy option for use in CLT construction projects.