Development of External Prestressing in Bridges: Evolution of the Technique
Pierre Jartoux and Roger LacroixI
Appears on pages(s):
bridges (structures); ducts; friction; galvanized materials; grout; long span; prestressed concrete; prestressing; prestressing steels; reviews; unbonded prestressing; Design
After 10 or so years of research and practical application, the external prestressing of concrete is now becoming a normal procedure, soon to be codified in some countries. Among the technical solutions applied to a large number of works, in the U.S.A. and France particularly, some emerge as being the best examples both from the point of view of performance and economy. This is the case where normal strands in HDPE ducts are used with an injected grout. This technique can be used equally well with removable external prestressing and with external prestressing that is partially bonded. In difficult cases, such as very long structures (bridges with lengths exceeding 200 m or 600 ft) or structures with high curvature (tanks and various vessels) or where it is difficult to bring large jacks up to the anchorages, an external cable, formed of projected strands, gathered together in the same HDPE duct and isolated from one another, is a very effective and elegant solution with an unequalled degree of protection and with the opportunity to check the prestressing force throughout the entire life of the structure.