Método simplificado de cálculo de la respuesta última de elementos de hormigón reforzados a flexión con materiales compuestos. Propuesta y verificación experimental

Simplified method for prediction bending response of RC members strengthened with FRP composites. Proposal and experimental validation

Reinforced concrete members strengthened in bending by bonding of surface-mounted fiber-reinforced polymer (FRP) may present several failure modes: failure of material (reinforcing steel, concrete, composite material) or failure of the interface between concrete-adhesive or adhesive-FRP. Nevertheless, experience gained from testing confirms that in most cases delamination prevails over the other possible rupture modes. Delamination typically results in detachment of the concrete cover between the plane of longitudinal reinforcing steel and the composite reinforcement to which is bonded. Delamination in FRP strengthened sections is a difficult to model issue because of the fragile nature of this rupture mode, but also for it involves multiple parameters such as FRP stiffness, adhesive material properties, presence of cracks in concrete, among others. There are some methods to obtain delamination strain by means of a complex sectional elastoplastic analysis, solving numerically some equation adopted as a failure criterion. A simplified method derived from one of these proposals is presented in this paper. The method is used to predict debonding strain of FRP flexural strengthenings in real RC members. The experimental validation of this model is presented as well. With this purpose CFRP and AFRP strengthened bond characterization specimen and large scale bridge models tests results are considered. The types of bridge models tested include externally-prestressed box-girder bridge and monolithic RC continuous girders.