Seismic design options for post-tensioned timber walls

Structural systems made of prefabricated laminated timber members connected by unbonded post-tensioning andadditional mild steel reinforcement have recently been proposed for multi-storey timber buildings. The benefits of theuse of post-tensioning to assemble prefabricated timber elements are rapid erection, simple connections, and highseismic resistance. It has been shown that prefabricated post-tensioned timber members can be designed to haveexcellent seismic resistance, with the post-tensioning providing re-centering capacity after major earthquakes, whileenergy is dissipated through yielding of replaceable steel elements. Both post-tensioning and energy dissipatingelements contribute to the stiffness and strength of the overall system.Investigation into the seismic response of twin post-tensioned timber walls, uncoupled and coupled, with and withoutenergy dissipaters has been performed as part of a larger research programme on timber structures at the University ofCanterbury. The walls were fabricated from laminated veneer lumber (LVL). A number of special fuses all made of mildsteel were used as energy dissipating devices. The energy dissipaters are attached externally so that they can beremoved and replaced easily after a major earthquake. Under gravity or low-seismic loading they would be able toprovide, as per standard mild steel reinforcement, substantial stiffness and strength. As additional option, plywoodsheets have been used to couple the LVL walls in which case the nails dissipated energy through yielding during rockingmotion of the walls. This paper discusses the experimental tests and numerical validation of the response of post-tensioned timber wall systems. The results show excellent seismic behaviour with very little residual damage. Thisresearch also demonstrates the practical feasibility of post-tensioned timber walls for multi-storey timber buildings aswell as their versatility of design and use.