Study on the strength of glued laminated timber beams with round holes: difference in structural performance between homogeneous-grade and heterogeneous-grade timber

Abstract

Various design codes and design proposals have been proposed for glued laminated timber beams with round holes, assuming that the entire beam is composed of homogeneous-grade timber. However, in Japan, glued laminated timber composed of homogeneous-grade timber is rarely used for beams. In this study, the difference in the load-bearing capacity of glued laminated beams composed of homogeneous-grade timber and heterogeneous-grade timber with round holes when fractured by cracking was investigated experimentally and analytically. The materials used in the tests were glued laminated beams composed of homogeneous-grade Scots pine timber with a strength grade of E105-F345 and heterogeneous-grade Scots pine timber with a strength grade of E105-F300. Experiments confirmed that although the glued laminated beams composed of heterogeneous-grade timber have a lower material strength in the lamina with holes, its resistance to fracturing due to cracks associated with the holes is almost the same as that of the glued laminated beams composed of homogeneous-grade timber. The stresses acting on the holes in the laminated timber with holes of less than half the beam height were lower in the glued laminated beams composed of heterogeneous-grade timber than in the glued laminated beams composed of homogeneous-grade timber. The ratio of the stresses was found to be approximately equal to the ratio of the maximum bending stress or the maximum shear stress acting on the inner layer lamina, as determined by Bernoulli–Euler theory.

Performance of Densified Wood Glulam as Building Bio-Material

“…The other structural application of glulam is in columns, trusses, reinforcing members, bridges deck and etc. Besides, the bonding ability of glulam components provides it for further applications [4][5][6][7][8][9]. The interest to apply this technology is to reduce product variability and make it less affected by natural growth features like knots.…”

Behavioral Assessment and Evaluation of Innovative Hollow Glue-Laminated Timber Elements

“…A great contribution to the investigation into the strength of glue-laminated timber beams with round holes was made by Okamoto et al [15]. Differences between homogeneous and heterogeneous timber grades were explored.…”