Rush hour traffic is a common daily occurrence nationwide. Highway and bridge construction further aggravates the situation. The Department of Transportation in several states and other government agencies are looking for ways to expedite construction. Increased use of precast concrete bridge piers and abutments is a step towards this goal.
The use of precast concrete bridge piers and abutments is not a new concept. This has been used in the past in Texas, Florida, New York, New Hampshire, and other states. The Federal Highway Administration (FHWA) with its Prefabricated Bridge Elements and Systems (PBES) initiative encourages the use of precast bridge piers and abutments. States like New Jersey and Virginia are actively looking into their use. In New Jersey, the value engineering proposal to use precast piers in order to expedite construction in the Rt. 3 over Passaic River Bridge Project is under review. For the I-295 Direct Connect Project, the New Jersey Department of Transportation (NJDOT) required the use of post tensioned segmental piers to expedite construction and to relieve motorists from construction related delays.
In precast construction, much of the substructure fabrication can be done in an off-site precasting plant. This shortens the on-site labor and construction time, thereby reducing traffic delays and detours during construction. A precasting plant allows for both the efficiency of mass production and a high level of quality control. Consequently, the cost of the precast substructure will be reduced. With the high level of quality control attainable in a precast plant, high performance concrete can be used. This results in more durable substructure units with higher quality and better finish. The higher strength of high performance concrete allows the use of hollow sections. Hollow sections result in material savings, lower hauling and erection weights, and decreased foundation costs. The use of post-tensioning with precast substructures will further improve durability by eliminating cracking under service loads and providing stiffer vertical elements that minimize deflections.