Structural performance of dowelled cross-laminated timber hold-down connections with increased row spacing and end distance

Abstract

This paper presents an experimental study to assess the structural performance of dowelled cross-laminated timber (CLT) hold-down connections that are critical components for a CLT shear wall under seismic loads. It aims to quantify the enhanced connection performance by increasing row spacing and end distance in the dowel layout compared with the standard spacing/distance specified by design standards. A total of 47 dowelled hold-down connection specimens with standard and increased row spacing and end distance in three-, five-, and seven-layer CLT layups were tested under monotonic and cyclic loading. Additional attempt was also made to investigate the benefits of applying screw reinforcement to deter the onset of potential brittle failure modes or mode cross-over. The increased row spacing and end distance provided comparable connection strength but significantly increased ductility. Displacement capacity and ductility increased by 35% and 20%, respectively and the effect was most pronounced in the five-layer CLT specimens. Dowel embedment tests were performed to verify the CLT Handbook equation and to determine theoretical overstrength. The maximum connection overstrength factor was 1.70 and the average was 1.61. Reinforcement by fully threaded inclined screws or the use of threaded dowels with nuts can further enhance the connection performance.