Design of timber structures

Well-designed and well-constructed timber structures can have an excellent response under earthquake loading due primarily to the high strength to weight ratio of wood. Nevertheless, the seismic performance of timber buildings involves various inter-related factors that need to be properly understood. Many of the aspects related to the resistance of timber buildings spring from the atypical mechanical characteristics of wood as a construction material. In particular, there are significant differences in wood strength and stiffness depending on the orientation of the load with respect to the grain direction as depicted in Figure 8.1. It follows from the schematic strain-stress curves, indicated in Figure 8.1, that tension failures in wood are brittle and should be avoided while compressive behaviour (parallel to the grain) is a preferred mode of failure but should be limited. In fact, it is a typical approach of codes of practice to ensure a ductile failure mechanism by inducing yielding in metallic connectors between timber members instead of the wood material itself in order to provide a sustained source of energy dissipation during seismic shaking.