Comportamento e desempenho do reforço à flexão de vigas de concreto armado, solicitado a baixa idade e executado inclusive sob carga

Abstract

In this work, an experimental study of the behaviour and performance ofreinforced concrete beams under bending is presented. The strengthening was performed through the increase of the steel and concrete sections at the tensioned region of the beams, and loaded at early age. The influence of the number of stirrups crossing the interface of the old and new concrete was verified, as well as the contact area of these two regions and the loading condition at the time of thestrengthening. The improvement in performance was evaluated. The behaviour of monolithic and strengthened beams were described. Experimental and theoretical results were compared, as well as the applicability of the criteria in NBR-6118 for the design of strengthenings. The results indicated the effectiveness of the strengthening method which improved considerably the performance of the members. The bond area between the two concretes was sufficient to assure the joint behaviour under loading. The strengthening under loading did not affect the load bearing capacity of the beams, which presented performance in service compatible with the initial displacement and strain. Strengthened and monolithic beams had equivalent behaviour and performance, which were correctly evaluated by the theoretical calculation. The guidelines in NBR-6118 demonstrated to be safe in the prediction of the behaviour and performance of the strengthened beams.