Creep analysis of P.C. bridge beams repaired with external tendons

The evaluation of the time evolution of the prestressing force in cracked P.C. bridge beams repaired with external tendons is performed in the domain of linear viscoelasticity for concrete and linear elasticity for steel. The problem is governed by a system of volterra integral equations, solved by means of the algorithm of the Reduced Relaxation Functions. The strong influence exerted by the amount of added prestressing steel on the reduction of the prestressing force is clearly pointed out. A numerical example related to a beam repaired with external tendons or external prestressing bars having quite different admissible final stresses allows to widely discuss the consequences of adopting different prestressing devices and the need of performing accurate analyses in order to guarantee a reliable behaviour of the repaired beams.