Numerical modeling investigation of cross-laminated timber connections consisting of multiple glued-in rods

Glued-in rods are stiff and high-capacity connections that are used in timber structures. Regardless of the many advantages of glued-in rods, research on the glued-in rods in CLT is limited, especially on numerical modeling. This paper provides the numerical modeling principles, validation details, and parametric studies of glued-in rods embedded on the edge of CLT. The numerical modeling was performed on a 3D finite element basis, and the cohesive surface method was used to define the bond lines along the rods. To validate the numerical models, 24 replica experiments were performed and investigated the effect of the rod diameter and of the embedment length on the pull-out strength of rods embedded perpendicular, parallel, and on the boundary of two cross-wised layers. The numerical models were validated according to the maximum load, stiffness, as well as the failure mode of the glued-in rods. The numerical models showed high reliability in simulating the experiments and predicted the strength of the glued-in rods with a maximum of 4% difference. After validation of the numerical models, the parametric study covered the pull-out strength investigation of rods with 20, 24, and 30 mm diameter and anchorage lengths of 250, 350, and 450 mm embedded in the perpendicular, parallel, and on the boundary of cross-wised layers on the edge of 5 and 7 layer CLT panels. The findings showed that increasing the embedment length and rod diameter enhanced the pull-out strength of the glued-in rods, regardless of where the rod was positioned on the CLT's edge. Rods embedded perpendicular to the grain showed the highest pull-out strength, and two rods with 30 mm diameter and 450 mm embedment lengths reached 961 kN pull-out strength. Numerical models showed that for the same diameter and embedment length of two rods embedded on the parallel and on the boundary of two cross-wised layers reached 836 and 738 kN pull-out strength, respectively. Finally, A design equation is provided to determine the pull-out strength of the glued-in rods embedded in CLT based on the shear strength of the bondline.