Effects of embedment side and loading direction on embedment strength of cross-laminated timber for smooth dowels

Abstract

Embedment strength is a decisive mechanical property of the dowel-type connection in cross-laminated timber (CLT) structures. Dowels can be installed in the plane or/and narrow side of CLT, which may result in different dowel embedment strength. To investigate the effects of embedment side and loading direction on the embedment strength of CLT, six groups of cubic specimens with predrilled half-holes, including three embedment positions and two loading directions, were tested according to the ASTM D5764-97a half-hole test method in this study. It was found that the embedment side, loading direction and the thickness ratio of transverse layer (TRTL) of CLT had significant influences on CLT embedment properties. The load-deformation behaviors and failure modes of each group were significantly different. The existence of transverse layers could reduce the embedment strength and improve the ductility of CLT under embedment tests. When only one layer bore the load parallel to the grain of wood, the crack occurred along the grain of this layer. When the transverse and longitudinal layers shared the dowel embedment load jointly, CLT had a better ductility. For dowels installed in the narrow side, the maximum and minimum embedment strength values were 37.66 MPa and 12.55 MPa, respectively. For dowels installed in the plane side, the embedment strength decreased with the increase in TRTL. The embedment strength of CLT calculated by the existing design models was different from the experimental values. These findings are important to providing a safe and efficient joint to achieve more efficient use of CLT products.