Resistance of cross laminated timber members under axial loading—a review of current design rules

Cross laminated timber (CLT) has become an important type of engineered timber product due to its superior material properties, making it suitable for mass timber construction. CLT is manufactured from naturally grown sources, and hence, it offers significant environmental benefit within the construction sector in comparison to its traditional counterparts such as concrete and steel. As a naturally grown material, timber products possess some inherent variabilities in material properties. These uncertainties make it difficult to develop universally accepted design rules for timber products, as the basic material properties may vary significantly based on its origin. This paper presents a review of current design rules for CLT under axial loads. Design procedures outlined in Eurocode, North American and Chinese standards as well as other relevant CLT handbooks have been thoroughly investigated. Experimental evidences available from literature have been used to compare the performance of those design guidance in predicting axial resistance of CLT members, where appropriate. Overall, it was observed that despite having considerable variations in mechanical properties, similar reliability concepts are adopted for specifying characteristic values, design values as well as for devising design rules for CLT structures. Once the design rules are critically evaluated based on test evidences, some design rules for CLT members under ultimate limit states have been summarised herein.