Incremental analysis of time-dependent effects in composite structures

Abstract

An efficient numerical method is presented, 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 global behaviour of structural elements made of several viscoelastic materials (composite beams, layered plates or shells) is expressed in terms of the generalized variables of the structure mechanics. The incremental nature of the formulation results from the choice of a Dirichlet’s series to express the constitutive law of the materials. A specific algorithm which allows for a process of construction by phases is implemented in a finite element program. The use of the method is illustrated through two computation examples: a prestressed concrete beam previously tested over a 5-year period of creeping, and an existing cooling tower which is a thin reinforced concrete shell. The method provides valuable information about time effects that may be used either while designing new structures, or for the diagnosis of existing structures.