The use of physical phenomena to predict time effects in cracked reinforced concrete beams

A method of calculating the time effects on cracked reinforced concrete (RC) members, based on actual physical phenomena, is presented. The redistribution of stress due to the migration of the neutral axis, and the consequent elastic and creep recovery are included in the calculation using the method of time-discretization. A simplified multiplier derived from the initial/time-dependent curvature, which is a function of the long-term strain factor, is used to calculate the time-dependent deflection. The concrete non-linear creep model established on axially loaded specimens is modified by introducing a parameter to account for the steel restraining effect on the creep deformation of RC flexural member. The modified model also considers the effect of the compression of the steel on the creep of the RC member. The calculated values are compared with laboratory measured values for several test beams of different cross-sectional properties reported in the literature. The proposed method gives results that are in good agreement with experimental results.