Stresses In Tendons Of Post-Tensioned Concrete Structures At Ultimate Limit State

Abstract

Currently post-tensioned concrete structures, which are designed with bonded or unbonded tendons, are widely used in construction. The features of calculation of post-tensioned structures with unbonded tendons, which are contained in some other design codes, are considered. It is noted that the current design code for plain and reinforced concrete structures include the provisions for the calculation of post-tensioned concrete structures with bonded tendons. However, there are no recommendations for the calculation of post-tensioned concrete structures with unbonded tendons, taking into account the specific features of the stress-strain state of structures with such prestressing tendons. These features significantly affect both the ultimate moment resistance of structures and their deformations, usually in the unfavorable direction in comparison with structures in which the bonded tendons are accepted. Therefore, the main attention when developing a method for calculating of post-tensioned concrete structures with unbonded tendons was paid to determining the stresses in such reinforcement at the ultimate limit state capacity check. As a result, a method for determining the stresses and increase of the stress from the external load in the unbonded tendons was developed for calculating the ultimate moment resistance of structures. The proposed method presented in the article showed a close correspondence with the data obtained from other studies, in which the stresses in the unbonded tendons were determined by the results of experimental and theoretical studies.