The strength of the anchorage zone of tensioned reinforcement bundles at prestressing on concrete

Abstract

The anchorage zone of a prestressed reinforcement element is a critical area of the reinforced concrete structure. The manufacturer of the prestressing system is only responsible for the local area – the area of concrete for which the confinement(local) reinforcement is designed. The analysis of national and international literature carried out by the authors has shown that when using complex forms of anchoring devices, confinement (local) reinforcement is difficult to select by analytical methods, and changes in its design must be confirmed by full-scale tests.

The article presents the experience of local reinforcement design for the OS-55 bearing plate by STSd, which has a complex shape and is used in nuclear power plant (NPP) containment. Requirements for testing of anchor zones are given. The description of calculation schemes with indication of applied models and properties of materials, assumptions in calculation is made. Methodology of testing according to European standards with indication of stages of loading, controlled parameters and scheme of installation of measuring devices is described. The results of calculations, tests and their comparison are given. The difference between the calculated and experimental values of displacements of the support surface of the bearing plate was not more than 2.9 % at loading levels of 80-105 % of the characteristic ultimate resisting force of the tendon. According to the methods of two national codes the calculated values of crack opening widths at the loading level of 80 % of the characteristic ultimate resisting force were determined. The theoretical and actual values were compared, the difference was not more than 3.5 %.

On the basis of comparison of the calculation results with experimental data, obtained during testing, the conclusion about successful verification of the accepted methodology of anchor zone design was made.