Veneer based composite hollow utility poles manufactured from hardwood plantation thinned trees

Abstract

Australia's utility pole network is aging and approaching its end of life. It is estimated that 70% of the 5 million poles currently in-service nationally were installed within the 20 years following the end of World War II and require replacement or remedial maintenance. Additionally, an estimated 21,700 high-durability new poles are required each year to support the expansion of the energy network. Utility poles were traditionally cut from native forest hardwood species. However, due to agreements which progressively phase out logging of native forests around Australia, finding new sources for utility poles presents a challenge. This paper presents the development of Veneer Based Composite hardwood hollow utility poles manufactured from mid-rotation Gympie messmate (Eucalyptus cloeziana) plantation thinned trees (also referred to as "thinning"), as an alternative to solid hardwood poles. The incentives behind the project and benefits of the proposed products are introduced in the paper. Small diameter poles, of nominal 115 mm internal diameter and 15 mm wall-thickness, were manufactured in two half-poles butt jointed together, using 9 hardwood veneers per half-pole. The poles were tested in bending and shear, and experimental test results are presented. The mechanical performance of the hollow poles is discussed and compared to hardwood poles sourced from mature trees and of similar size. Additionally, the required dimensions of the proposed hollow pole to replace actual solid poles are estimated. Results show that the proposed product represents a viable technical solution to the current shortage of utility poles. Future research and different options for improving the current concept are proposed in order to provide a more reliable and cost effective product for structural and architectural applications in general.

Characterisation of Physical and Mechanical Properties of Unthinned and Unpruned Plantation-Grown Eucalyptus nitens H.Deane & Maiden Lumber

“…The interest in fast-growing plantation species such as eucalypt is increasing as they may have the potential to ensure a sustainable supply of raw materials for producing mass laminated timber products for different structural building applications [1][2][3][4][5][6]. The goal of this study was to characterise the physical and mechanical properties of lumber obtained from a 16-year-old pulpwood Eucalyptus nitens (E. nitens) H.Deane & Maiden resource.…”

Perpendicular to grain and shear mechanical properties of veneer-based elements glued from single veneer sheets recovered from three species of juvenile subtropical hardwood plantation logs

“…The approach above is currently followed (Gilbert 2018, Gilbert, et al 2017a, Gilbert, et al 2017b to determine the mechanical properties of Laminated Veneer Lumber (LVL) and plywood panels manufactured from Australia's underutilised hardwood plantation forest resources in structural applications, namely juvenile (early to mid-rotation) hardwood plantation logs. The methodology will also be extended to derive the design properties of innovative veneer-based hollow structural products manufactured from the same resource (Gilbert, et al 2014, Gilbert, et al 2017c.…”

Structural solutions to produce long timber Veneer Based Composite hollow sections

“…Spindleless technology has demonstrated to recover up to 70 % of these small diameter logs into veneers [2] and offers the possibility to use this resource for Veneer Based Composite (VBC) products. In this effort, VBC hollow sections are currently being developed [3] and are seen as a potential solution to meet a range of applications, offering new market opportunities. These novel sections have the advantage of having an efficient cross-sectional shapes and able to be manufactured in large cross-sectional sizes that are no longer available in sawn timber.…”

“…The two half-sections are then butt joined together to form a full section, as shown in Figure 1 (a) for circular hollow sections (CHS). The concept was tested in [3] and proved to be an efficient and structurally sound solution to Australia's current shortage of traditional solid hardwood utility poles [5]. With applications also extending to the building industry, the sustainability of the product was studied in [6].…”

“…When tested in compression, failure was initiated by local buckling of the GFRP. This paper experimentally assesses the bending capacity, efficiency and suitability of three different manufacturing concepts designed to produce useable lengths of the circular hollow VBC sections investigated in [3] and presented in Figure 1. The capacity of each concept is reported and compared to the capacity of a reference VBC hollow section.…”