Effects of bolt diameter and load direction on dowel-bearing behaviour of laminated bamboo

The dowel-bearing strength is a crucial parameter for determining the bearing capacity of pin connections, which is essential for calculating the bearing capacity and reliability of such connections. In this study, bolts with diameters of 6, 8, 10, and 12 mm were used to conduct monotonic loading tests on 128 specimens across eight groups. The dowel-bearing strength was determined using the 5% diameter off-set method. The effects of bolt diameter and load direction on the dowel-bearing strength of laminated bamboo were thoroughly examined. The test results assessed the predictability of dowel-bearing strength theoretical equations for laminated bamboo in previous studies and standards. The findings revealed that the bolt diameter had minimal influence on the stiffness of the compression specimens parallel-to-grain, but had a significant effect on the stiffness of the compression specimens perpendicular-to-grain. As the bolt diameter increased, the stiffness of the compression specimens perpendicular-to-grain also increased, exhibiting a linear relationship. The dowel-bearing strength decreased with the increase in bolt diameter from 6 to 8 mm, and the reductions were more pronounced for the specimens perpendicular-to-grain. For the specimens parallel-to-grain, their stiffness was considerably greater than that of the specimens perpendicular-to-grain, and the dowel-bearing strength was 1.75–1.90 times that of the specimens perpendicular-to-grain. By comparing relevant literature, standards, and test results, a modified formula for the dowel-bearing strength of laminated bamboo was proposed. The modified formula demonstrated a superior ability to predict the dowel-bearing strength of laminated bamboo.