Abstract:
Accurate estimation of stress in unbonded tendons at the nominal strength limit state is essential for calculating the in-plane strength of unbonded post-tensioned wall panels. The study presented here was originally conducted for concrete masonry, and is currently being extended to include verification for precast concrete. International masonry and concrete design codes and standards provide varying equations for calculating unbonded tendon stress at the nominal strength limit state but in no case have these equations been verified for in-plane loading of walls. A finite element model validated against large-scale structural testing of post-tensioned concrete masonry walls is used in this paper to demonstrate the accuracy of these existing equations. A revised equation is then shown to provide the most accurate predictions of tendon stress for walls loaded in-plane and is recommended for inclusion in the masonry design standards NZS 4230. Subject to the results of current testing, it is expected that the equation shall prove equally suitable for inclusion in NZS 3101 also. The paper concludes by summarising the complete procedure for predicting the inplane response of post-tensioned masonry walls.
