Study On Creep Of Reinforced Concrete Beams Based On B3 Model

Creep is an important long-term performance of concrete, which will increase deflection and induce the stress redistribution between concrete and steel bar of reinforced concrete (RC) beams. This phenomenon will influence suitability, security, as well as durability of the structure. Due to the complexity of the mechanism that creep effects on RC beams, the problems are far from to be solved up to now.In this paper, concrete creep model B3 based on solidification theory is introduced into creep calculation of RC beams. With analysis of mechanical characteristics of RC beams, a creep model of RC beams that agrees with microcosmic mechanisms and characteristics of concrete creep is proposed, and then a computation model for long-term deflection of RC beams is present. The model takes the stress redistribution between steel and concrete, as well as the continual change of the height of the neutral axis into consideration. Afterwards, B3 model is substituted for ACI and CEB-FIP model form 2 new models. Calculation results of all the models are compared with experimental data, drawing with the conclusion that creep model of RC beams based on B3 model is more reasonable and accurate than other models.This paper analyzed the influence of reinforcement ratio (ρ) to the long-term creep of RC beam and draw the conclusion that the long-term deformation of beam decreases with the increasing of reinforcement ratio (ρ). Since the influence of concrete mix proportion on concrete creep has been taken into account in B3 model, using the proposed model, effects of several internal factors that are considered to have impact on creep of reinforced concrete, such as water to cement ratio(w/c) and aggregate to cement ratio(a/c) of concrete. Results show that creep of reinforced concrete beam increases with the increasing of load magnitude and water to cement ratio; and decreases with the increasing of aggregate to cement ratio.