Performance of pull out glued-in-rod for different grain angle directions and rod diameters of mengkulang glulam / Wan Nor Nasuha Mohamad

The most crucial aspects when designing glued-in rod (GiR) connection on glulam timber structure is to ensure the efficiency of detail design parameters consideration. Question arise on whether the GiR is practical enough to be used in structures that may involve the connection at different and incline direction to the grain such as notches, curved and arch beam and others. The effect of load-to-grain direction is considered as one of these parameters. It governs the strength performance of GiR as shear stresses along the jointing part will tend to act differently. Since there has been no research carried out on mengkulang (Tarrietia javanica) glulam experimental pullout strength at different grain directions, this study is important to provide fundamental information of GiR connection practices for glulam structures. Thus, pull-out tests on 150 numbers of GiR with selected rod diameters (12, 16 and 20 mm) for five different angles (0°, 45°, 60°, 75° and 90°) made of Mengkulang glulam were conducted in this study. The adhesive used was epoxy resin, Sikadur-30 and the rod is high strength of mild threaded steel rod. The rod was subjected to constant cross-head displacement of 2mm/min and set up to pull-push loading configuration. The test is carried out until failure in the specimen by using the Universal Testing Machine with load capacity of 1000kN. The result shows that the load-to-grain direction and rod diameter had linear correlation to the strength of pull-out test. The load acting on 0° to the grain direction demonstrated the strongest bond overall with able to cater the highest load and displacement. The load was up to 136.87kN for 0° and the lowest 69.84kN recorded for 90° grain direction, while 45°, 60° and 75° were in between these two angles. The difference between these angles however, did not vary significantly. Sequentially, the highest load was recorded for 20 mm rod diameter and decreased with smaller rod diameter. The shear stress along the timber-adhesive interface was found to be the weakest compared to adhesive-rod interface which showed the failure occurred due to some part of timber along the joint had sheared out together with steel rod when subjected to pull-out test. Timber-Adhesive failure is concluded as dominant mode of failure in this study by 36.11% failed.