Creep effect on composite beam with perfect steel-concrete connection

In the context of primary creep, a new approach to the study of the effects of creep on the resistance of a composite beam is reported. The beam is in perfect connection, statically determinate and bent under a moderate load applied at time t0. The proposed model is based primarily on the theory of linear viscoelasticity of concretes and specifically on the principle of the irreversible law of deformation established by Dischinger. In this work, two equations of equilibrium and two other equations of compatibility at the steel-concrete interface are considered. This compatibility is rewritten according to Dischinger's rheological equation for ageing materials while adopting elastic behaviour for the metal profile. Then, the mathematical treatment of the written compatibility should lead to the establishment of a system of two differential equations of the first order. The analytical resolution of this system provides the expressions for the generalized internal forces of the composite beam in terms of time. Using these mathematical expressions, it is easy to predict the state of internal stresses and the strains of the beam at any time, t. Finally, the proposed analytical approach is confronted with various other methods.