Investigation and improvement of strut-and-tie model for design of end anchorage zone in post-tensioned concrete structure

The strut-and-tie model (STM) is commonly used for the design of the end anchorage zone in post-tensioned concrete structures. In present work, the most accepted STMs in practice design for either centric or eccentric anchorage zone were inspected comprehensively based on experimental investigations and FEM simulations, to improve the models in accuracy, economy and efficiency. FEM was first employed to obtain the stress distribution in the anchorage zone, to reveal the influence of the anchor size and tension eccentricity on the compressive force, bursting force, spalling force and flexural tensile force. Based on FEM findings, the Mörsch STM for the design of centric end anchorage zone was configured and modified by taking into account the counteractive effect of the spiral circle and reinforcement on the distribution of stress in the anchorage zone. The adjusted Mörsch STM was employed for small eccentric end anchorage zone with the simplified equations from the FEM simulations. For the large eccentric end anchorage zone, a completely design procedure based on Schlaich model was offered by improving the determination method of the spalling force and bursting force in both values and locations. In above improvements on STMs, simplified equations were proposed for engineers to design the end anchorage zone more conveniently.