DEVELOPMENT OF A CORRELATION MODEL FOR TORSIONAL SHEAR MODULUS PROPERTIES BETWEEN STRUCTURAL SIZE SPECIMENS BASED ON EN 384:2016 AND SMALL CLEAR SPECIMENS (MS544: PART 2)
DOI:
https://doi.org/10.11113/jurnalteknologi.v86.20819Keywords:
Shear modulus, torsion testing, structural dimension, small defect-free samples, tropical hardwood timberAbstract
In timber design, the shear modulus of timber beams is vital for ensuring torsional stability and minimizing issues with vibrational serviceability. Typically, the shear modulus is determined by the ratio of E to G, which is 16:1. However, the bending test introduces a combination of flexural and shear stresses, making it challenging to accurately assess the pure shear properties and shear stiffness value. The most recent British Standard, BS EN 408:2012, advocates for the torsion test as the standard method for characterizing properties of structural size timber or timber composite materials. Currently, this method has garnered limited attention in Malaysia. The main aim of this study is to investigate the torsional shear modulus of Malaysian tropical timbers categorized into different strength groups (SG), such as Balau (SG1), Kempas (SG2), Kelat (SG3), Kapur (SG4), Resak (SG4), Keruing (SG5), Mengkulang (SG5), Light Red Meranti (SG6), and Geronggang (SG7). Torsion tests were conducted following BS EN 408 standards, and the resulting shear modulus values were compared with modulus of elasticity published in MS554: Part 2. The results revealed that the shear modulus values for all timbers exhibit the following order: Balau > Kempas and Resak > Kelat, Kapur, Keruing, and Mengkulang > Geronggang > Light Red Meranti. The modulus of elasticity to shear modulus ratio for all species falls within the range of 17:1 to 29:1, with an average ratio of 21:1, markedly exceeding the conventional E:G ratio of 16:1.
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