Preliminary performance-based design of a post-tensioned glue-laminated timber frame

Post-tensioned timber joints have been studied at the ,nstitute of Structural Engineering at the ETH =urich. A post-tensioned beam-column timber joint has been developed using glued laminated timber with local hardwood reinforcement. 2nly a single straight tendon is placed in the middle of the beam and post-tensioned to restrain the rotation of the joint. 1o additional steel elements are used. The developed joint is characterised by a high degree of pre-fabrication and easy assembly on site. The glue-laminated timber moment-resisting frame featuring this joint shows great potential for timber frame structures especially for multi-storey buildings. Robust performance-based design criteria are a necessity for a s uccessful market implementation of the proposed system. A simplified analytical model was developed in order to predict the structural performance of the post-tensioned timber connection and facilitate preliminary performance-based design. This model was implemented in 2penSees using a bi-linear rotational spring approach. The model was verified against an analytical model and validated against tests on a post-tensioned timber joints under gravity loading and under horizontal loading. Moreover, a complex numerical model was developed using 2penSees to check the accuracy of the proposed preliminary design model. The preliminary design model was used to design fictitious moment-resisting post-tensioned glue-laminated timber frame structures using the loads prescribed in the Swiss code. The design process showed that neither the gravity loads nor the seismic load controlled the design. The design was governed by the lateral deformations due to wind. Based on this finding it is recommended to focus further research on increasing the connection stiffness or on adding additional structural elements to address the seismic performance of post-tensioned timber frames in regions of high seismicity