Effect of Adhesive Viscoelasticity on the Creep Behaviour of FRP Strengthened Concrete Beams

This paper focuses on the effect of the viscoelasticity of the adhesive layer on the flexural creep response of reinforced concrete beams strengthened with composite materials. A theoretical model is developed, which considers the strengthened beam as a layered structure that consists of the reinforced concrete beam, the adhesive layer, and the FRP strip, and accounts for the creep of each component. The model also accounts for cracking and tension-stiffening of the reinforced concrete and for the deformability of the adhesive layer in shear and through its thickness, which allows the evaluation of the edge and interfacial stresses. A parametric study of different viscoelastic material properties of the adhesive is presented, and their effect on the time variation of the internal forces and edge stresses is investigated.