Pull-out strength of steel rods bonded into mengkulang (tarrietia javanica) glulam at five different angles to the grain

Abstract

The design of a glued-in rod into timber, with respect to the grain, is critical as the capacity of the joint is highly dependent on the grain orientation. Since there has been no research carried out on mengkulang (Farrietia javanica) glulam experimental pull-out strength at different angles to the grain, this study is important to provide fundamental information for steel rod connection. A total of 25 pull-out strength tests were conducted on glued-in threaded steel rods bonded into glulam made of mengkulang at 0° (parallel), 45°, 60°, 75° and 90° (perpendicular) to the grain, using epoxy adhesive. The rod was subjected to constant cross-head displacement of 2 mm min-1. The pull-out strength was found to be negatively correlated with the angle of the grain, with failure load decreasing from 97 to 62 kN as grain angle increased from 0° to 90°. Displacement (until failure) was greatest (10 mm) when the load was applied perpendicular (90°) to the grain and smallest (6.8 mm) at 45°. The highest percentage difference in strength (44.12%) was between 0′ and 90° angles to the grain, thus the former was twice as strong as the latter connection. Significant increase in percentage of strength (11.2%) was observed as grain angle decreased from 90° to 0°. Shear breakage along the adhesive and timber interface was the dominant mode of failure recorded for all the samples tested.