Time-dependent Stiffness of Cracked Reinforced and Composite Concrete Slabs

The effects of creep and shrinkage on the time-dependent behaviour of reinforced concrete and composite steel-concrete slabs are discussed and procedures for the prediction of the long-term deflection are presented. The time-dependent deformations caused by creep and shrinkage are modelled using tractable formulations developed using the age-adjusted effective modulus method of analysis. The procedure includes the time varying nature of tension stiffening and the effects of time-dependent shrinkage-induce cracking. Sample calculations are provided. The methods are validated against a range of test data and are shown to provide reliable estimates of in-service deformations.