Experience of duplex stainless steels as structural materials for bridges

Abstract

The use of duplex stainless steel (DSS) in bridge construction has increased significantly in the last twenty years because of the material’s high strength and good corrosion resistance. The high corrosion resistance of DSS results in a low maintenance requirement and hence low life cycle costs. There is now a range of DSS grades available and it is possible during the design phase to undertake a material selection exercise for DSS to align the required material performance with the bridge environment. Lean alloyed and less costly DSS grades can be specified in less harsh environments. This paper presents the results from inspection of various existing road, rail and pedestrian bridges. In each case a DSS was used for the main structure and each bridge illustrates the performance of the material in a representative European environment. The environments were retrospectively classified in accordance with the recently introduced EN 1993-1-4 Annex A and a comparison of actual performance made with the guidance given in this annex. Previous high-level cost studies have indicated that durable, low-maintenance bridge designs using DSS are achievable without incurring excessive initial construction costs, and that significant life cycle cost savings can be made over the life of the structure. The present work has confirmed that, when appropriately selected and used, DSS can be anticipated to give long service lives in bridge structures, greatly reducing corrosion problems that may necessitate re-painting and remediation of carbon steel structures.