Structural behaviour of hardwood veneer-based circular hollow sections of different compactness

Abstract

This paper presents the capacity and structural behaviour of hardwood veneer-based circular hollow sections (CHS) tested in bending, shear and compression. The sections were manufactured from early to mid-rotation (juvenile) Gympie messmate (Eucalyptus cloeziana) plantation thinned logs. In total twenty-one 167 mm Outside Diameter (OD) × 1.2 m long CHS were manufactured in seven sets of three nominally identical sections. Two different wall thicknesses were investigated to produce nine compact and twelve more slender cross-sections. The sections were also manufactured in three different structural grades. A sudden failure mode was observed in the compression zone of the slender sections tested in bending. In compression, the compact sections showed a ductile behaviour, while the slender sections showed a more brittle behaviour, with the sections bursting into longitudinal strips. While a relationship was observed between the bending and compressive capacities, and the structural grade, no such relationship was noticed for the shear capacity. Comparison to steel and concrete sections of similar outside diameter proved that the timber sections are the most efficient in terms of bending and compressive capacity to linear weight ratio. The timber sections fall behind their steel and concrete counterparts in terms of shear efficiency, however they still have enough shear capacity for representative structural applications.

Veneer-based timber circular hollow section beams: Behaviour, modelling and design

“…This section introduces the experimental tests which were used to validate the FE model in this paper. The tests were performed in [2] on four 145 mm × 15 mm, and in [1] on three slender 167 mm × 12.5 mm and three compact 167 mm × 25 mm CHS timber beams, all specimens subjected to a constant bending moment. The sections were manufactured from juvenile hardwood plantation Gympie messmate (Eucalyptus cloeziana) rotary peeled veneers and aimed at finding a high-value market for this under-utilised resource.…”

“…Nominal 2.5 mm thick veneers were used in the manufacturing process and all were orientated along the longitudinal axis of the sections. A CHS beam was composed of two half-sections which were manufactured from different veneer sheets to fit the research purpose in [1,2] and be consistent with what would be expected in industrial applications. The half-sections were butt-jointed together using structural epoxy resin, as shown in Figure 1 (a), and the butt joints were positioned at the neutral axis of the cross-sections during the bending tests.…”

“…Additionally, strain gauges recorded the longitudinal strain of the 167 mm diameter cross-sections at mid-span and at both tensile and compressive extreme fibres. The experimental bending test set-up is fully detailed in [1,2] and the reader is kindly invited to refer to these papers for more information.…”

“…Hollow timber structural elements, either manufactured from boards or veneers, have been proposed in the literature [1][2][3][4][5][6][7][8][9][10][11][12][13] and some products are commercially available [14,15]. These products have efficient cross-sectional shapes, are lighter than conventional plain timber elements and can be manufactured in sizes currently not available in sawn timber.…”

“…These products have efficient cross-sectional shapes, are lighter than conventional plain timber elements and can be manufactured in sizes currently not available in sawn timber. Experimental investigations showed that they have the stiffness and strength required to be used, for instance, as structural elements [1,2] and temporary anchor nails [12,16,17]. However, tests performed on Circular Hollow Sections (CHS) manufactured from either juvenile hardwood plantation veneers [1,2] or moulded from beech boards [13], showed that the cross-section in compression could fracture and open.…”