Embedment Behaviour of Hybrid Cross-Laminated Timber (HCLT) Made of Fast-Growing Chinese Fir and OSB

The embedment strength and stiffness of wood products are key parameters in the design of timber structures using dowel-type connections. The embedment behaviour of layered wood products such as hybrid crosslaminated timber (HCLT) will result from a combination of the behaviours of the multiple layers. In this paper, half-hole embedment tests according to ASTM D5764-2013 are presented, evaluating the embedment performance of HCLT made of fast-growing Chinese fir and OSB with self-tapping screws (STS). Six prediction models proposed by current standards and other scholars are compared with the measured data for strength, and two modified models are proposed to predict embedment strength for HCLT. Specimens loaded parallel to the grain of longitudinal layers had a higher bearing capacity, yield and ultimate embedment strength. An increase of STS diameter improved the bearing capacity of specimens but had a negative influence on the embedment strength. The modified models proposed here achieved more accurate prediction of the experimental characteristic values for HCLT than the existing methods, both for yield and ultimate embedment strength. The findings of this study represent progress towards the safe and economical structural design and wider application of innovative CLT products in the construction industry.