Embedment strength of smooth dowel-type fasteners in cross-laminated timber

Abstract

Embedment strength is a fundamental parameter for dowel-type connection design in timber structures. It is known as a system property dependent on the characteristics of both the fastener and the wood material. The orthogonal layup in cross-laminated timber (CLT) differentiates it from solid timber (ST) and glued-laminated timber (GLT) in terms of connection properties. The effects of CLT layup feature (i.e., the thickness ratio of transverse layer to the total thickness, TRTL) as well as wood density, dowel diameter, and loading angle on the embedment strength of smooth dowel-type fasteners were investigated in this study. A total of 660 CLT embedment tests were performed according to the half-hole method in ASTM D5764. The results indicated that the embedment strength and failure modes of CLT were different from those of GLT due to the existence of a transverse layer in CLT. The influence trends of four effective factors on the CLT embedment strength were different, and each factor had a statistically significant impact on the embedment strength of the CLT. The experimental data were used to examine the existing predictive models of CLT embedment strength. It was found that the influences of the four effective factors on CLT embedment strength differed among the models. A modified design equation was proposed based on the test results with a better agreement than the existing design equations.