Cross-laminated timber : a state-of-the-art review towards a proposed structural analysis strategy

Abstract

Cross-laminated timber (CLT) has experienced growing global popularity in recent years, extending to South Africa with the adoption of SANS 8892 (2020), which allows for local manufacturing of performance-rated CLT. However, this standard requires all locally produced CLT layups to undergo extensive mechanical verification to determine strength and stiffness properties. Analytical methods have proven relatively accurate in predicting the out-of-plane mechanical properties of CLT. Incorporating these methods into design equations can aid in the structural design and sizing of CLT elements. The currently proposed prEN 1995-1-1 (2023) contains design factors specific to CLT, largely common with sawn timber. Adopting such an approach would simplify CLT design in South Africa, using established partial factors, as is the case for plywood. Resistance equations are therefore proposed using existing partial factors for sawn timber design in SANS 10163-1 (2003), incorporating Timoshenko beam theory calculations for bending and shear stresses in CLT. However, the material resistance factor value of 0.68 proposed for sawn timber may be overly conservative due to CLT’s inherent load-sharing behaviour. Using the methods outlined by Pagel (2019) and variability results of South African pine-only CLT obtained by Jacobs (2023), an average resistance factor of 0.79 was determined.