Seismic design options for post-tensioned timber walls

A. Iqbal, S. Pampanin, A. Palermo, A. H. Buchanan & M. Fragiacomo

Structural systems made of prefabricated laminated timber members connected by unbonded post-tensioning and additional mild steel reinforcement have recently been proposed for multi-storey timber buildings. The benefits of the use of post-tensioning to assemble prefabricated timber elements are rapid erection, simple connections, and high seismic resistance. It has been shown that prefabricated post-tensioned timber members can be designed to have excellent seismic resistance, with the post-tensioning providing re-centering capacity after major earthquakes, while energy is dissipated through yielding of replaceable steel elements. Both post-tensioning and energy dissipating elements 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 without energy dissipaters has been performed as part of a larger research programme on timber structures at the University of Canterbury. The walls were fabricated from laminated veneer lumber (LVL). A number of special fuses all made of mild steel were used as energy dissipating devices. The energy dissipaters are attached externally so that they can be removed and replaced easily after a major earthquake. Under gravity or low-seismic loading they would be able to provide, as per standard mild steel reinforcement, substantial stiffness and strength. As additional option, plywood sheets have been used to couple the LVL walls in which case the nails dissipated energy through yielding during rocking motion of the walls. This paper discusses the experimental tests and numerical validation of the response of posttensioned timber wall systems. The results show excellent seismic behaviour with very little residual damage. This research also demonstrates the practical feasibility of post-tensioned timber walls for multi-storey timber buildings as well as their versatility of design and use.


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