Analysis of anchorage zone stresses in post-tensioned concrete girders

Abstract

Application of pre-stressed concrete for the construction of civil engineering structures especially bridges has increased tremendously. In the pre-stressed post-tensioned concrete structures, anchorage zone is the critical area of concrete ahead of the anchorage device. During application and diffusion of the pre-stressing force in a post-tensioned girder, tensile bursting stresses are developed at some distance ahead of the anchorage device in a region known as the general zone. These stresses often lead to serviceability problems and congestion of reinforcement at the anchorage zone. In this paper, a rectangular end block of 600 × 600 mm, with a bearing plate size of 214 × 214 mm, subjected to a concrete pre-stressing force of 2204 kN was analysed using the methods like elastic method, deep beam analogy, strut-and-tie model approach, finite element analysis and also using the codal provisions specified in IRC: 18 and British code BS: 8110. From the analysis of 2D finite analysis, it was observed that the variation of bursting stress in the end block is parabolic in nature. It was observed that with increase in eccentricity of bearing plate, there was a decrease in bursting tensile stress, whereas the value of spalling tensile stresses increases drastically. However, with increase in the size of the bearing plate, both the spalling and bursting stresses decrease considerably. It was also found that the grade of concrete has negligible effect on the distribution which is of bursting tensile stress. The finite element analysis of anchorage zone with multiple anchors indicates that spalling stresses are more critical than the bursting stresses for the design of anchorage zone. © Springer Nature Singapore Pte Ltd 2021.