Increasing the Capacity of Existing Bridges byudUsing Unbonded Prestressing Technology: A Case Study

摘要

External posttensioning or unbonded prestressing was found to be a powerful tool for retrofitting and for increasing the lifeudextension of existing structures. Since the 1950s, this technique of reinforcement was applied with success to bridge structuresudin many countries, and was found to provide an efficient and economic solution for a wide range of bridge types and conditions.udUnbonded prestressing is defined as a system in which the post-tensioning tendons or bars are located outside the concrete crosssectionudand the prestressing forces are transmitted to the girder through the end anchorages, deviators, or saddles. In response toudthe demand for a faster and more efficient transportation system, there was a steady increase in the weight and volume of trafficudthroughout the world. Besides increases in legal vehicle loads, the overloading of vehicles is a common problem and it must alsoudbe considered when designing or assessing bridges. As a result, many bridges are now required to carry loads significantly greaterudthan their original design loads; and their deck results still deteriorated by cracking of concrete, corrosion of rebars, snapping ofudtendons, and so forth. In the following, a case study about a railway bridge retrofitted by external posttensioning technique will beudillustrated.