Section analysis and cyclic behavior of post-tensioned jointed ductile connections for multi-story timber buildings

A new seismic resisting system for multi-story timber buildings has been recently developed and proposed by the authors based on refinement and adaptation of jointed ductile connections, using post-tensioning technology, originally developed for precast concrete construction. Successful implementation of the concept and confirmation of the high structural and seismic performance of such systems has been obtained through extensive experimental testing on system subassemblies carried out at the University of Canterbury in the past few years. In this contribution, a simplified analytical model for the analysis of the section and overall connections behavior is proposed based on the extension of existing procedures proposed and adopted for the design and analysis of jointed ductile precast concrete walls and frames. Particular focus will thus be given to the specific modifications required when dealing with the peculiarity of post-tensioned connections using orthotropic timber engineered wood materials such as Laminated Veneer Lumber or Glu Laminated systems. The modified procedure, suitable for both analysis and design, is herein verified rising the aforementioned extensive experimental test data from quasi-static cyclic tests on wall, column, and beam-column subassemblies. Based on detailed analytical-experimental comparison, looking at both local and global connection behavior, suggestions are given in terms of (a) strain penetration contribution when dealing with internally glued mild steel reinforcement, (b) actual stiffness of the connection when accounting for the bearing effects in the parallel or perpendicular-to-the-grain directions. These considerations are then implemented into the design procedure in order to guarantee control over the re-centering/dissipative system mechanism.