The use of digital image correlation for identifying failure characteristics of cross-laminated timber under transverse loading

The localised crack induced by external load on an individual cross laminated timber (CLT) structural element will generate stress concentrations, which leads to the failure of a structural member. A better understanding of the structural performance of CLT in terms of its strength and failure modes under transverse loading needs to be developed to ensure structural stability, safety and resilience of mass timber buildings. The monitoring and prediction of crack initiation and the failure modes of structural elements before and after localised deformation could enable the mitigation of severe damage in timber buildings. In this study, four-point bending tests were conducted and the digital image correlation (DIC) technique was used as a cost-effective solution to monitor the crack initiation and growth behaviour and predict the failure types of Australian radiata pine CLT panels under out-of-plane loading. Both a speckled surface pattern and the natural grain of the timber were used in the DIC analysis. This will aid with the development of efficient performance-based design guidelines for timber buildings. Based on the crack growth rates and strain fields, the DIC technique can predict the failure locations and modes, namely rolling shear or delamination. This study also highlighted that DIC analysis with a natural grain of timber can be used to measure the crack growth rates in CLT.