Influence of shrinkage cracks on the mechanical properties of bolted-type glulam joint with slotted-in steel plate: Experimental study

Environmental shrinkage cracks are obviously observed in bolted-type glulam joints due to the material mechanical-physical properties and high moisture transport rate. The objective of ongoing research mainly presents an experimental study on the mechanical properties of bolted-type glulam joints with cracks. To shorten the test time and control the crack pattern, the outer moisture-induced shrinkage cracks are replaced by preset cracks. Thus, thirteen glulam joints with different preset cracks are designed and tested. The parameters are three locations (i.e., along the top bolts, neutral axis, and bottom bolts), two lengths (i.e., 140 mm, and 330 mm), three depths (i.e., 30 mm, 60 mm, and 118 mm), and two kinds of layouts (i.e., cracks on the same side and different sides). In the experiments, the loading process and failure modes of the joints were observed, the load-displacement relationships were analyzed and the residual bearing capacity of the joints was recorded. The joint exposed to the controlled climate change test showed that longitudinal cracks were easily observed along with the bolts in multiple steel-to-wood joints and four reasons were presented for this phenomenon. Furthermore, significant reduction values were observed due to cracks for joints in terms of their initial stiffness k, peak load P-max, and displacement Delta(max) up to 79.3%, 75.39%, and 95.1%, respectively. Additionally, reduction coefficients were proposed for the calculation of residual bearing capacity. The calculation results showed good consistency with the experimental tests.

Automated summary

The ongoing research focuses on the mechanical properties of bolted-type glulam joints with environmental shrinkage cracks, showing significant reductions in parameters such as initial stiffness, peak load, and displacement due to cracks. Controlled climate change tests revealed the effects of cracks on the longitudinal integrity of joints, with proposed reduction coefficients for residual bearing capacity calculations demonstrating good consistency with experimental tests.