Paper number 241

A THIRD-ORDER APPROACH FOR THE REINFORCEMENT OF CONCRETE SHELLS WITH EXTERNAL COMPOSITE LAMINATES

A. J. M. Ferreira, A. T. Marques , J. C. De Sá

Departamento de Engenharia Mecânica e Gestão Industrial, Faculdade de Engenharia da Universidade do Porto
Rua dos Bragas, 4099 Porto Codex, PORTUGAL

Summary

It is presented a third-order approach for the reinforcement of concrete shells with external composite laminates. Reinforced concrete (RC) structures are a very important sector in civil construction industry. Corrosion of steel re-bars is a common problem, due to the porosity of concrete. The use of external composites (FRP) bonded to the faces of concrete are today a good solution to the strengthening and retrofitting of degraded structures [1-3]. The behaviour of such structures is highly non-linear. The need for non-linear geometrical and material models implies the use of numerical methods such as the finite element method. The use of higher-order shear deformations is now common in the analysis of composite laminates. In this paper it is proposed the use of a third-order shear-deformation theory in the analysis of concrete shells strengthened with external composite unidirectional strips. This theory is an alternative to the first-order theory proposed by Ferreira et al [11]. The theory is implemented in a shell element that allows for a layered discretisation of the laminate materials. A perfect plastic and a strain-hardening plasticity approach are used to model the compressive behavior of the concrete. A dual criterion for yielding and crushing in terms of stresses and strains is considered, which is complemented by a tension cut-off representation. The material law for the unidirectional composites is linear elastic/brittle. A simply-supported concrete beam, reinforced with composite strips is analised. The effects of the reinforcement, the use of the third-order theory and the comparison of composite strengthening and steel rebars on concrete are discussed.

Keywords

concrete shells, finite element analysis, frp reinforcement, composite materials, composite reinforcement, third-order theory.