This paper describes how to build an efficient numerical method to account for time effects in composite structures. The method is based on the theory of linear viscoelasticity and on the finite element method. The behaviour of usual structural elements is expressed in terms of the generalized stresses and strains of the beam, plate or shell theories. The incremental nature of the formulation results from the choice of Dirichlet's series to express the time dependent behaviour of the materials. The approach is developed for composite beams, layered plates or shells made of several viscoelastic materials. Its yields a general formulation, similar to thermoelastic problem, where the whole stress history of the structure is concentrated in a set of specific cumulative variables. This incremental formulation may be implemented in a finite element program. The choice of an object oriented program makes the implementation of the step-by-step procedure easier. A specific algorithm is proposed to allow for a process of construction by phases. Two computation examples illustrate the use of the method: a prestressed concrete beam previously tested by other authors over a period of five years of creeping, a cooling tower which is a thin concrete shell made of reinforced concrete. In the construction and for the next thirty years of service of the structure. The computation provides valuable information about the effects of creep and shrinkage on the stress and strain distribution and on the deflection of the structure.

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