Inspection Guidelines for Bridge Post-Tensioning and Stay Cable Systems Using NDE Methods (2017) / Chapter Skim
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5 Post-Tensioning and Stay Cable Systems Introduction This chapter is comprised of four major sections. The first section presents an overview of the bridge post-tensioning system, which consists of the internal and the external posttensioning systems.
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6Internal Post-Tensioning Internal post-tensioning is characterized by placement of the steel tendons in longitudinal ducts that are within concrete elements. Figure 2-3 shows examples of internal tendons in precast concrete elements.
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7 of corrosion of PT tendons is more critical to the structural performance of post-tensioning systems than conventionally reinforced systems. In addition, the cost to replace tendons can exceed several hundred thousand dollars per tendon.
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8are typically used in anchorage blisters, external tendon deviation points, and as looped vertical tendons in precast PT piers. • Smooth high-density polyethylene (HDPE)
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9 cables of a cable-stayed bridge must have large tensile strength and high fatigue resistance. There are several systems for cable-stayed bridge cables that have been used in the past and continue to be used today.
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10 Corrosion Protection Systems The corrosion protection system is just as important as the structural properties of the strand. Corrosion protection systems can include various combinations of galvanizing, epoxy coatings, corrosion inhibiting greases and waxes, sheathing, and other materials.
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From page 11... ...
11 Saddles Saddles are used to avoid tower anchorages and enable a continuous stay cable passing over the tower. This requires that the MTEs be jacked simultaneously at the two deck anchorages on each side of the pylon, both during construction and future maintenance.
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