Dowel-Bearing Strength Properties of Two Tropical Hardwoods

Abstract

Bearing strength of wood is one of the properties that are use to estimate the lateral connection of wood design strength based on the European Yield Model (EYM), National Design Specification [NDS 2005 in National design specification for wood construction american forest and paper association (AFPA), Washington D.C, 2005] theory. This study investigated the characterisation of load to grain directions and two dowel sizes in two high-density Malaysian hardwood species; Kempas (koompassia Malaccensis) and Kapur (Dryobalanop spp.). Experimental work as stipulated in ASTM 5764-9a [American Standard Testing Method (ASTM) D 5764-95a in ), Standard test method for evaluating dowel-bearing strength of wood and wood-based products, 2007] was adopted. Result shows that according to the species, the lower strength group of species attributes to higher bearing strength of wood. It was also found that the bearing strength of parallel to the grain is higher than the perpendicular to the grain. In terms of dowel diameter, the bearing strength perpendicular and parallel to the grain decreased slightly as the dowel diameter increased regardless of the timber species. The EYM equations were found viable and sufficient in predicting the dowel-bearing strength of bigger dowel diameter for Kempas but not for the smaller dowel diameter. Contradict to Kempas species; the EYM equations were viable for the smaller dowel diameter and not for the bigger dowel diameter for Kapur. Thus, in the case of the insufficient predictions, three modified equations based on EYM, were proposed according to the specific gravity, density, species, dowel diameter and loading directions respectively.