Strengthening and Retrofitting of Steel Bridges

This chapter begins with a brief description of the most common typologies of steel bridges. Typical structural deficiencies and damages of steel bridges are outlined to identify the basic needs of rehabilitation actions. It includes the damage produced by corrosion, fatigue, increasing of live loads, seismic actions, poor detailing and vehicle collision. Initially, a description of the characteristics and performance of traditional rehabilitation techniques is outlined. Later, the superstructure rehabilitation techniques based on the use of composite materials as carbon, aramid or glass fibre plates, as bonded external reinforcement, and aramid or glass fibre rods for prestressing are considered. The experience about the behaviour of strengthened beams under overloading and fatigue conditions are also outlined and the heat strengthening of steel girders after a collision is commented as well. The use of steel jacketing of columns is also described and the benefit of using link beams to improve the transverse seismic response of multicolumn bents. Base isolation as an appealing strategy for reducing the seismic demand in piers and foundations and the advantages of its application is discussed and the use of cable restrainers added for limiting the longitudinal displacement is also analysed. In the end, the methodologies more employed to assess the seismic vulnerability of bridges to select the best retrofit technique, and the parameters to be considered for a better selection of the bridge intervention are described.