ABSTRACT
This chapter commences by examining the dimensional changes that occur in timber following variations in its moisture content and/or temperature. The magnitude and consequently the significance of such changes in the dimensions of timber are much greater in the case of alterations in moisture content compared with temperature. The chapter then examines the effect of stress on deformation. When a sample of timber is loaded in tension, compression or bending, the instantaneous deformations obtained with increasing load are approximately proportional to the values of the applied load. In applying the elements of orthotropic elasticity to timber, the assumption is made that the three principal elasticity directions coincide with the longitudinal, radial and tangential directions in the tree. Creep behaviour in timber, like that of many other high polymers, can be interpreted with the aid of mechanical (rheological) models comprising different combinations of springs and dashpots.
