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

Abstract

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.

Direct Path-Integral Scheme for Fatigue Simulation of Reinforced Concrete in Shear

“…These compressive constitutive equations were verified in terms of material and structural member levels by El-Kashif and Maekawa (2004b). This model targets the space-averaged stress strain relation for the referential size of 20 cm.…”

Three-Dimensional Fatigue Simulation of RC Slabs under Traveling Wheel-Type Loads

“…Furthermore, time-dependency and fatigue effects have been investigated by El-Kashif and Maekawa (2004) for compression modeling. For shear transfer, Maekawa (2006a) and Gebreyouhanness (2006) extended the original contact density model (Li and Maekawa 1989) to the fatigue one.…”

Nonlinear Modeling of 3D Structural Reinforced Concrete and Seismic Performance Assessment

“…They pointed out that if the high speed nonlinear creep (relaxation) that occurs in the high strain region is not taken into consideration, it is difficult to further improve the accuracy. For this purpose, the nonlinear creep model developed by El-Kashif and Maekawa (2004) was also used. In addition, the reinforcement model by Dhakal and Maekawa (2002) that simply modeled the concrete spalling criterion for the concrete cover and the lateral buckling of reinforcing bars was used.…”