Influence of release grooves, edge gaps and aspect ratios of transverse layer on shear performance of CLT made from fast-growing Chinese fir

To promote the utilization of local species in cross-laminated timber (CLT), fast-growing Chinese fir, an important wood specie in southern China, has recently been developed for CLT production. The short-span four-point bending tests were conducted to evaluate the shear performance of Chinese fir CLT. An orthogonal experiment was employed to investigate the influences of manufacturing parameters of the transverse layer, such as the aspect ratio, width of edge gaps, and depth of stress release grooves, on the ultimate load-bearing capacity of CLT in shear test. Shear strength of CLT was calculated using three theoretical methods, and the results were compared to assess the differences among them. It was found that rolling shear failure was the main failure mode among the four failure modes of specimens under short-span four-point bending test. For specimens with edge gaps or release grooves, rolling shear cracks were observed around these features. Aspect ratio of transverse layer had slight positive influence on the CLT shear performance. However, both stress release grooves and edge gaps of transverse layer showed significant negative influence. Furthermore, the shear strength calculated by the GB 50005–2017 method is relatively close to that calculated by shear analogy method, whereas the shear strength calculated by the gamma method is lower than the theoretical values calculated by the other two methods. The findings here provide practical guidance for the engineering design and application of fast-growing Chinese fir CLT.