ii THE MECHANICAL PROPERTIES AND STABILITY OF RADIATA PINE STRUCTURAL TIMBER

Investigating stiffness, strength and stability in radiata pine structural timber is significant to the civil engineering, forestry industry and genetic selection in New Zealand due to the following reasons: 1. Radiata pine provides about 90 % structural timber for industry and is one of the major incomes of the forestry industry in New Zealand. 2. Stiffness, strength and stability are major quality criteria of structural timber. 3. Radiata pine stem has large proportion of corewood that tends to be low in stiffness, strength and stability. This study first presents the maps of average stiffness, average strength and average warp in radiata pine structural timber, obtained from sixty-two 27-year old, unpruned radiata pine trees. From these maps, one can conclude that the butt logs are problem logs, because the butt logs displayed the lowest stiffness, as well as the maximum bow and spring within the stems. The stiffness and strength distributions were compared with the typical distribution of wood density, which reveals that the wood density alon