Performance of Segmental and Posttensioned Bridges in Europe

With a history a decade or two longer than in the United States, the October 1999 Scanning Tour by the Federal Highway Administration was to examine European performance, durability and maintenance of prestressed concrete, segmental, and cable-stayed bridges to help identify possible concerns and to estimate future needs for maintenance, repair, retrofit or replacement in the United States. All countries reported corrosion of prestressing tendons, concrete, or reinforcing steel -- but generally in a minority (2% or so) of structures -- from poor quality grouting of tendons or honeycombed concrete allowing ingress of water and chlorides. For new construction, improved grouts and stringent practices have been introduced. Both external and internal tendons are used in European segmental construction. More “robust” ducts of durable polyethylene are being introduced (Switzerland) and new “greased and sheathed” monostrands find favor for repair or retrofit. Where appropriate, new fiber composite materials are used for rehabilitation as in the United States. Widespread European policy is to apply waterproof membranes, drainage, and protective overlays to bridge decks of all types of construction. Less aggressive deicing is being introduced. Structures have been replaced mostly for functional obsolescence rather than deterioration. Maintenance inspection is similar to that in the United States but with a greater commitment to upkeep. Available nondestructive investigation techniques for tendons and cable-stays include X-ray, ultrasonic, electrical resistance, magnetic perturbation, georadar, etc., but their use requires engineering expertise and interpretation. Instrumentation with remote monitoring is occasionally installed on major structures. European cable-stay structures are performing well. Current trends are to greased and sheathed monostrands in high-density polyethylene pipes. Wind-rain vibrations are suppressed by ribbed stay-pipes and/or various types of damping installed during or after construction. Segmental and cable-stay developments in Europe and the United States are moving in parallel directions and improved technology. With appropriate attention to improved grouting, these types of structures continue to be built and will serve well into the foreseeable future.