Gert Heshe

Size Effects on the Bending Behaviour of Reinforced Concrete Beams

ABSTRACT Load-deformation curves for reinforced concrete beams subjected to bending show size effects due to tensile failure of the concrete at early stages in the failure process and due to compression failure of the concrete when the final failure takes place. In this paper these effects are modelled using fracture mechanical concepts, and size effects of the models are studied and compared with experimental results.

Appendix D: Fracture Mechanical Model for Rotational Capacity of Heavily Reinforced Concrete Beams

Abstract In this appendix the flexural behaviour of reinforced concrete beams is investigated by analytical methods originally introduced by A. Hillerborg. A simple analytical model is presented which describes the bending moment-curvature relation for normal and over-reinforced beams taking into account the strain localization within the compression zone of the concrete. The strain softening part of the stress-strain curve for the concrete is described as a stress-deformation relation which is dependent on the length over which the compression failure extends along the beam axis. On the basis of the moment-curvature relation estimated by the model, the load-deflection curve is calculated, and the rotational capacity is obtained as the total plastic work divided by the yield moment of the beam. The results of the model are obtained assuming a linear compression softening curve with different values of the critical compression deformation and the fracture zone length. The results are compared with experiments.

Appendix A: Test Programme for Bending Failure of Reinforced Concrete Beams of Different Scale

Abstract In this appendix a brief summary of experiments on reinforced concrete beams in three-point bending performed at Aalborg University is given. The aim of the investigation is to determine the full load-deflection curves for different beam sizes, different types of concrete and different amounts and types of reinforcement, and to calculate the rotational capacity for all beams. The rotational capacity is here defined as the non-dimensional area under the load-deflection curve, and the results are shown as functions of the reinforcement ratio.