Titre du résumé français joint : Modèle d'interface homogénéisée décrivant des défauts périodiquement répartis sur une surfaceNational audienceWe undertake the homogenization of a three-dimensional elastic medium, which contains heterogeneities localized on a surface. These can be either reinforcements, like steel reinforcements in concrete, or defects, like microcracks periodically distributed. We propose a simple model describing the effective behaviour of these heterogeneities. This model, formulated in an energetic framework, com- bines an elastic interface behaviour with that of a membrane. Its interest is discussed through several applications.See http://hal.archives-ouvertes.fr/docs/00/59/28/84/ANNEX/r_O1H9ABAW.pd