Analysis of Crack Expansion and Morphology of Cross-Laminated Timber Planar Shear Test

To describe the dynamic cracking process of the CLT vertical layer, the correlation between a load-displacement curve, specimen cracking, and planar shear failure mechanism of the CLT were explored. A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT. In this study, the load-displacement curve is recorded, the experimental part is synchronized with the video, the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test. From the load-displacement curve, the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summarized. The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by planar shear strength value, cracking phenomenon, and azimuth angle of cracking surface. The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT, with a difference of only 5.7%. The original crack and the new crack expansion account for 18.9% and 81.1% of the main cracking surface, respectively. And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies, such as radial shake, ring shake, neither along with the radial shake nor along with the ring shake. The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test. The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.