In-grade testing of Norfolk Island pine (Araucaria heterophylla) to enable characterisation of the timber

This report deals with an investigation into the structural properties of the timber species, Norfolk Island pine (Araucaria heterophylla) to enable characterisation of the timber. The various structural properties (bending stress, shear stress, compressive stress, tensile stress and Modulus of Elasticity) are determined by full-scale (in -grade) testing procedures.

Full-size specimens were tested at the University of Central Queensland in Rockhampton and NSW State Forests Research facility at Pennant Hills in Sydney.

The timber is being used on Norfolk Island as a structural and decorative timber. Because it is a limited but renewable resource, optimum use needs to be made of it as a building material to make maximum use of the material. Presently Norfolk Island has an inverse balance of payments with timber products, the vast majority of which is imported New Zealand radiata pine. If this balance of payments is to be reversed, better utilisation needs to be made of the locally produced timber. Implied in this also is improved utilisation of local labour and industry in producing the local product.

No significant testing has been done in the past on Norfolk Island pine. The only technical references to it in the literature appears to be in the botanical and silvicultural context. One author has given the material a provisional grading only (this would be based on small clear specimens, possibly not even produced on Norfolk Island).

It is only with rigorous full-scale testing of the product that its structural properties can be determined with any confidence so as to make better use of it as a building material.

This thesis reports on such testing of full-size, randomly selected, locally -produced specimens. The work is undertaken in accordance with the recent joint AS/NZ Standard AS 4063:1992. It is believed that this is the first work of this type that has been undertaken on this material.

The results are varied, indicating relatively higher shear and compressive strengths but, by comparison, lower bending and tensile strengths and Modulus of Elasticity. Without doubt, the timber is weakest in tension (some 3 grades below its equivalent compression classification). Careful selection will need to be made of the timber for applications where it is in tension.

The relatively close spacing of the knots appears to have strong influence on reduced strength. If the knots can be reduced by improved silvicultural techniques or eliminated in post-harvesting/milling operations, such as excising the knots and re -jointing (eg finger - jointing) then a much improved product could be obtained.