Calcul de résistance de structures planes en béton armé de fibres

Résumé

Une méthode de calcul de structures armées de fibres est présentée. Les caractéristiques du matériau sont exprimées au moyen de relations matricielles, compte tenu de l'arrachement des fibres dans une matrice plane fissurée. La méthode par éléments finis permet de prévoir le comportement élastique et plastique, ainsi que la fissuration et la rupture. Les résultats de l'analyse générale sont comparés avec les résultats d'essais sur deux poutres en béton armé, l'une avec fibres et l'autre sans.

Summary

This article treats about the strength behaviour of brittle construction materials, especially concrete, reinforced with steel fibres. The material characteristics are expressed by matrix relationships, which describe the elasto-plastic behaviour as well as the cracked behaviur of concrete reinforced with fibres. Those relationships permit to predict the bearing capacity of any structure in the elastic, the plastic and the cracked states. After cracking of the concrete, the fibres are pulled out while the adhesion and the attachment are resisting.

The material laws are then incorporated in an analysis with the finite element method: the plane structure is subdivided in elements in which a proper account is taken of the variable material characteristics. When a crack appears in a finite element, the stress state alters and this change gives rise to compensative nodal forces. These forces alter again the stress state and new cracks can appear, so that an iterative scheme must be adopted for each load increment.

The results of the general analysis are compared with results of tests on two reinforced concrete beams, one with and one without steel fibres.

The analysis has the feature to predict the overall behaviour of fibre reinforcement for any complex structural shape at any load stage.