STRUT-AND-TIE MODEL FOR INTERMEDIATE ANCHORAGES IN POST-TENSIONED CONCRETE BRIDGES

Within intermediate anchorage zones in post-tensioned concrete bridges, there are combinations of splitting actions ahead the anchors and tie-back actions behind the anchors. First, the finite element analysis is carried out to reveal the elastic stress distributions and stress trajectories in the intermediate anchorage. It is shown that there is an equal share of concentrated load transferred ahead and behind the anchor. After that, a strut-and-tie model is developed to reflect the load-transfer mechanisms in the intermediate anchorage. Furthermore, the principle of minimum strain energy is introduced to find out the optimal configuration of the strut-and-tie model. From the equilibrium of forces in the strut-and-tie model, explicit equations for splitting force and tie-back force are developed. The accuracy of the proposed equations is verified by the comparison with the results of finite element analyses.