Time-Dependent Post-Peak Softening of RC Members in Flexure

To investigate the rate effects on post-peak structural behavior accompanying the compression softening of structural concrete, experimental studies were carried out on over-reinforced concrete beams with and without confinement under varied rates of flexural loading. The effects of loading rate on the capacity and ductility of RC beams were found more pronounced in confined cases than unconfined cases. The generic time-dependent constitutive model of compression-softened concrete was applied to nonlinear collapse analysis and its applicability was verified by experiments. The strain rate in the compressive localized zone in structures rapidly increased after the member reached its peak capacity even though the rate of displacement was kept unchanged especially in the case of unconfined beams. In the case of confined RC beams, localization of weak strain occurred but with comparatively greater time-dependent plasticity and fracturing within the structure. These deformation characteristics were adequately simulated by nonlinear analysis using a time-dependent constitutive model for softened concrete in compression.

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