A More Realistic Estimation of Ductility in Reinforced Concrete Beams Through Three-Dimensional Finite Elements

Abstract Ductility in reinforced concrete (RC) beams subjected to bending is generally assessed on the basis of the one-dimensional (1D) beam theory through the moment–curvature relationship of its cross-section. The inhomogeneity of concrete, however, inevitably imposes a three-dimensional (3D) stress state in any RC structural member. The importance of this work is its different approach to assessing the ductility in RC beams, taking into account this triaxial stress state. A concrete model which has been well documented experimentally in the literature is used, in conjunction with an in-house 3D smeared fixed-crack finite element code. Simply supported beams under three-point monotonic loading are used as numerical examples. After validating the results with experiments, three important parameters which affect the ductility and strength of RC beams are investigated. These are the tension reinforcement ratio, the yield strength of tension reinforcement steel and the compression reinforcement ratio. It appears that, for the first two, the general trend remains the same as with the 1D approach of the Codes, whereas the third does not affect the ductility of the under-reinforced beams, contrary to the Codes.

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