Innovative Projects

By Elements and Systems

Rapidly expanding technologies associated with materials and equipment have made it possible for components of bridges and assembled composites of bridge components-sometimes even entire bridges-to be prefabricated. Bridge engineers are increasingly turning to prefabrication of the following bridge elements and systems to save money, to solve project-specific challenges, and to increase the quality of bridges by conducting fabrication in a controlled environment.

Superstructure: Decks

Prefabrication offers exceptional advantages for deck construction, particularly for removing deck placement from the critical path of bridge construction schedules, for cost to place the deck, and for quality of the deck:

• Partial-depth prefabricated deck panels act as stay-in-place forms to not only speed construction but also allow more controlled construction for a more durable deck than fully cast-in-place decks.
• Full-depth prefabricated bridge decks facilitate and speed construction, and bridge designers are finding innovative ways to connect full-depth panels.

Here are examples of bridge projects that use prefabricated partial or full-depth decks.

Superstructure: Total Superstructure Systems

Increasingly, innovative bridge designers and builders are finding ways to prefabricate entire segments of the superstructure:

• Preconstructed composite units may include steel or concrete girders prefabricated with a composite deck, cast off the project site and then lifted into place in one operation.
• Truss spans can also be prefabricated. Prefabrication on this scale offers tremendous potential advantages in terms of constructibility, on-site construction time, and the need to have equipment on the construction site.

Here are examples of bridge projects that use prefabricated total superstructure systems.

Substructure: Bent Caps*

Cast-in-place bent caps require extensive formwork and curing times. If they are fabricated off-site, curing times are not a factor. As a result, bridge owners and contractors are increasingly turning to precast bent caps:

• For over-water bridges, they reduce the amount of time that workers need to operate over-water.
• For bridges over existing roadways, they minimize formwork required, reducing disruption to traffic on the lower roadway.
• For bridge with job-site constraints, such as power lines that affect work zone safety, they limit the amount of time that workers are at risk.

Here are examples of bridge projects that use prefabricated bent caps.

* The term "bent cap" refers to the horizontal member at the top of the columns that supports the superstructure.

Substructure: Columns*

Bridge construction times can be greatly reduced by using precast columns on cast-in-footings or drilled shafts. Columns can be segmental, post-tensioned, either hollow or concrete-filled. Here are examples of bridge projects that use prefabricated columns.

* The term "column" refers to a vertical member topped by a bent cap that supports the superstructure.

Substructure: Total Substructure Systems

A total substructure system may consist of individual pier(s) or prefabricated bent cap supported by prefabricated column(s). Here are examples of bridge projects that use total substructure systems.

Total Prefab Bridges

Total prefab bridge systems offer maximum advantages for rapid construction and depend on a range of prefabricated bridge elements that are transported to the work site and assembled in a rapid-construction process. Here are examples of bridge projects that use total prefab bridge systems.