Efficient End-Zone Detailing of Pre-tensioned Concrete Elements

Abstract

Throughout the literature concerning end-zone detailing of pre-tensioned concrete elements, different methods can be identified to determine the necessary passive reinforcement to account for the tensile stresses occurring in the anchorage zone. Moreover, some of these models provide ambiguous instructions concerning the exact placing of the reinforcement. When these models are evaluated for the same element, a range of possible end-zone reinforcement lay-outs is obtained. These different reinforcement lay-outs also lead to different performances concerning the end-zone crack control. This paper presents a new strut-and-tie model (STM) for the calculation of the necessary end-zone reinforcement area. The design of the STM is based on stress field vector plots obtained from a finite element model in which both the transfer of the prestress force from the tendons to the surrounding concrete and the non-linear material behaviour of concrete is modelled in detail. A comparison of end-zone detailing, obtained from commonly used design models and from the proposed STM, is presented and the efficiency of these reinforcement lay-outs is evaluated in terms of crack control. It is concluded that the newly presented STM provides a simple method to determine the necessary amount of reinforcement area, leading to efficient end-zone crack control of pre-tensioned concrete elements.