Fatigue behavior of bonded and sandwich systems for strengthening orthotropic bridge decks

The strengthening systems studied consist of bonding a second steel plate to the existing orthotropic bridge deck, either by using a 2 mm thick epoxy adhesive layer (bonded system) or a 15–30 mm thick polyurethane core (sandwich system). The aim of applying the reinforcement is to reduce the stresses at the deck and extend the fatigue life of orthotropic bridge decks. Three and four point bending fatigue tests were carried out on beam type specimens representing the reinforced deck. Linear elastic simulations using FEA were performed to determine the stress distribution during tests. Results show that the fatigue damage of the reinforcements are caused by the shear stresses at the adhesive layer, for the bonded system, and by the shear stresses at the faces-to-core interface, for the sandwich system. The fatigue strength of the bonded system is not significantly affected by adhesive thicknesses between 1 and 3 mm. The same can be found for the sandwich system with 15 mm and 30 mm polyurethane-core thickness.