Precast concrete’s structural and aesthetic versatility, resiliency, accelerated construction, and quality make it an excellent choice for bridges and other transportation structures including noise barriers, median barriers, and pavements. These are comprised of a variety of shapes and components. This section addresses some of the most common shapes and components used in the transportation industry.
Bridge Superstructure Components
There are several different shapes of beams used throughout the U.S. for bridges, mostly determined by each state. Here are examples of the most common shapes and types:
Villanova University Pedestrian Bridge
Precast, prestressed flat slabs are used in short-span bridges. They typically have spans between 25 and 45 feet between supports. A concrete or asphalt wearing surface can be cast onto the structure.
South Maple Street Bridge Replacement
Adjacent box beams contain centric voids and are used to span short to medium distances with a shallow depth superstructure system. They also provide a stay-in-place formwork for a wearing surface to be cast onto after installation.
Samuel De Champlain Bridge
Pretensioned, prestressed beams are the most common precast element used in the bridge industry today. These are used in medium- to long-span bridges. The girders are typically placed and made composite with a deck. The deck may be precast or cast-in-place.
Wekiva Parkway #204 Systems Interchange
Orange County, FL
Using precast concrete, horizontally curved bridge elements are not new: a curved monorail guideway at Disneyland was built in the late 1960s. The Philadelphia, Pa., airport ramp (1983) was the first application of curved precast concrete girders for roadway bridges.
Bridge Substructure Components
There are a number of different precast substructure elements, including:
Precast End Bents
I-10 Tex Wash Bridge
Desert Center, CA
Precast End Bent Caps are used in small and large structures.
Piles and Pile Bent Caps
Bath Iron Works Land Level Transfer Facility
Precast Pile and Pile Bent Caps are often used for accelerating bridge construction projects.
Water Line Pile Caps
SC 802 Bridge
Lady's Island, SC
Similar to Pile bent caps, water line pile caps with a CIP column are designed to simplify dewatering operations and accelerate construction.
Manette Bridge Replacement
Precast columns are often used in bridge structures. Depending on the precast concrete producer, columns are available in round, square, and custom shapes and finishes.
Precast pavement slabs are a quick and durable method of replacing pavement and returning a roadway to service quickly. Slabs are available as both conventional reinforced and prestressed. Precast construction involves installing prefabricated concrete panels on grade. The panels themselves provide the final riding surface for the finished pavement and do not require an asphalt or cementitious overlay. They are typically used to replace existing pavement, but can also be used for new construction or to overlay existing pavement.
Precast panels are generally provided in sizes to match the width of one, two, or three lanes of the pavement, permitting one or multiple lanes of an existing pavement to be reconstructed at one time, depending on site clearance constraints. The precast panels are generally oriented transversely to the roadway centerline, and may also include shoulders. Panels may be prestressed in both directions. The panels are installed on a prepared base, connected (dowel bars or post-tensioned) together, and opened to traffic.
Sound Walls/Noise Barriers
These structures are designed to meet noise abatement requirements. They are normally constructed with a post and panel configuration. The project noise study will specify if the system is an absorptive or reflective design. They may include traffic barrier protections when constructed adjacent to the travel lane.
Related Resources & Articles