Predicting Creep and Shrinkage Effects in Cracked Concrete Elements

Based on Trost-Bazant stress-strain response relationship of concrete, an algorithm to predict the final stresses and strains including creep and shrinkage effects in initially cracked structural concrete elements with or without prestress is presented. Necessary expressions that give rise to familiar section modulus concept are developed for the general case of T section with compression reinforcement, nonprestressed tensile reinforcement, and prestressed reinforcement. In addition, the concepts of equivalent effective depth, equivalent eccentricity and equivalent normal force are introduced. Furthermore, the method takes into account the noncoincidence of the neutral axis of stress with the neutral axis of strain. To ease the computational effort, development of design aids in the form of tables is proposed. The numerical examples given in this paper demonstrate the advantages of the method, which are familiarity, simplicity, adoptability, and accuracy that is sufficient for design purposes.