Splitting failure of precast prestressed concrete during the release of the prestressing force

Bond between steel and concrete is fundamental for the transmission of stresses between both materials in precast prestressed concrete. Indented wires are used to improve the bond in these structural elements. The radial component of the prestressing force, increased by Poisson's effect, may split the surrounding concrete, decreasing the wire confinement and diminishing the bonding. This work presents a testing procedure to obtain the bond-slip curves, between steel and concrete, during the releasing of the prestressing force. The experimental procedure allows study of the splitting failure of the concrete, induced by the action of the indented wire. The influence of the distance between wires, the thickness of concrete cover and the depth of the wire indentations on the bond and splitting are examined. Specimens with three depths of the wire indentations and three thicknesses of concrete cover were tested. Moreover, a numerical procedure is presented for modelling the bond-slip, taking into account the possible failure of concrete by splitting. The numerical procedure accurately reproduces the experimental records and improves knowledge of this complex process. (C) 2009 Elsevier Ltd. All rights reserved.