Post-tensioning makes possible the cost-effective construction of high-quality bridges over a wide range of conditions and span lengths including highway alignment. Bridge structures constructed using post-tensioning have high intrinsic durability and are able to be built quickly with minimal impact on the human and natural environment. Further, structures constructed using post-tensioning also benefit from the method’s ability to limit cracking, reduced structural depth, ease of accommodating curved roadway alignment and low maintenance costs. And, these benefits do not come at the expense of aesthetic expression.Cast-in-place cantilever construction has become the preferred method of building long-span concrete bridges as well as concrete arches with the help of temporary towers and stays. It is a proven cost-effective means of building spans ranging from 200-feet (60 m) to more than 1,000-feet (300 m). It has been used to cross major bodies of water, deep mountain canyons, and densely populated urban areas. Further, post-tensioning can be used effectively to build bridges on alignments that are curved in plan.
Post-tensioned superstructures, which can be built quickly and without touching the land or water below the bridge, are a relatively low impact structural system and optimal solution. For longer spans (commonly up to 300-feet or more), shallower girder depths, and continuously curved superstructures, post-tensioning offers ductility and seismic performance as well as superior aesthetics to today’s precast designs. Post-tensioning also provides more flexibility in the layout of span lengths, bent configurations and roadway geometrics than precast I-girders or reinforced concrete box girders.
Advantages of precast segmental bridge construction include:
-The economy of precast prestressed concrete construction is extended to a span range of 100 to 400 feet (30 to 120 m). Longer spans may be economical where use of heavy erection equipment is feasible.
-Precast segments may be fabricated while the substructure is being built, and rapid erection of the superstructure can be achieved.
-Higher quality control because of the repetitive industrialized manufacturing techniques, with the inherent potential of achieving high-performance concrete.
-Minimal interference with Bridge Environment: The need for false work is eliminated and all erection may be accomplished from the top of the completed portions of the bridge. This may be of particular importance for high-level crossings or in cases where it is necessary to minimize interference with the bridge environment.
-The effects of creep and shrinkage are substantially minimized through the use of precast segments that have matured to full strength.