Post-tensioned timber frame buildings

This paper describes the development of post-tensioned timber frames for multi-storey timber buildings. Post-tensioned timber beams and frames give opportunities for much greater use of timber and engineered wood products in large buildings, using innovative technologies for creating high quality buildings with large open spaces, excellent living and working environments, and resistance to hazards including earthquakes, fires, and extreme weather events. Post-tensioned timber building systems are being developed at the University of Canterbury in collaboration with the Structural Timber Innovation Company Ltd (STIC) funded by Australian and New Zealand industries, and the New Zealand government. The post-tensioned structural system uses unbonded steel tendons in ducts in large timber box beams. In moment-resisting timber frames, the horizontal steel tendons also pass through the columns, providing moment resistance. Added advantages for extreme loading are ductility, and total re-centring of the building after an earthquake. The system can also be used with draped tendons in long span beams over a number of internal supports, or with vertical post-tensioning in columns or solid timber shear walls with vertical ducts for the tendons. The post-tensioning also provides for rapid erection, and simple and economical connections between the large timber elements. This paper gives details of experimental testing and the design of prototype buildings, describing other features such as high fire resistance, thermal and acoustic performance, and low carbon footprint.