The strength of the anchor zone of the prestressed span structure against local bursting stresses

Abstract

   The concrete of the anchorage zone of a post-tensioned reinforced concrete element is in a complex stress-strain state. The concrete area behind the anchor experiences significant local tensile stresses – bursting stresses transverse to the longitudinal prestressing force.
   In most cases, the anchorage zones in the main girders of superstructures are located near the support sections. In this way, dense reinforcement for shear force and torsion can be found in the analysis area. However, in addition to the standard transverse reinforcement, extra transverse reinforcement must be considered to provide strength for local bursting stresses.
   Actual national standards require the designer to take into account the stress-strain state during the analysis the reinforcement of anchorage zones, but do not provide a design method.
   This paper presents a method of design the transverse reinforcement to provide strength for bursting stresses for a post-tensioned main girder of an overpass with a large set of anchors AKS-19 (STS, Moscow). Two design cases are considered: the first one with anchorage zone located above the bearing pad (the bearing influence on the stress-strain state of the anchorage zone concrete is taken into account); the second one with anchorage zone located on the border of the casting sections (the stress-strain state is determined directly by post-tensioning). A description of the applied analysis models is made, specifying the preconditions and assumptions in the analysis. The results of bursting force calculations and design of additional transverse reinforcement are given.