Why do engineers love bridges? They're outstanding in their field.
Why do engineers love bridges? They're outstanding in their field.
Modern concrete bridges built from precast segments joined by post-tensioning, enabling rapid construction of long spans.
Total in US
421
Poor Condition
1.7%
Avg Sufficiency
67.4
Average Age
28 yrs
Segmental bridges represent one of the most important advances in concrete bridge construction. Rather than casting the entire bridge in place, the superstructure is divided into short segments (typically 3-5 meters long) that are either precast in a factory or cast-in-place one at a time. These segments are then assembled and joined using post-tensioning tendons that compress them together into a monolithic structure.
The segmental method revolutionized bridge building because it allows rapid, high-quality construction with minimal disruption below the bridge. Precast segments are manufactured under controlled conditions, ensuring consistent quality, and can be erected at rates of one segment per day or even faster. The balanced cantilever method of erecting segments outward from each pier eliminates the need for extensive falsework.
Segmental box girder bridges are now the standard for medium to long-span concrete bridges worldwide. The hollow box cross-section provides excellent structural efficiency, with the interior space allowing for inspection and maintenance access. Modern segmental bridges span 50 to 300 meters and carry everything from highway traffic to light rail systems.
Segmental bridges work by using post-tensioning to compress individual concrete segments together into a continuous beam or frame. Each segment is a short section of the box girder, cast with precisely formed match-cast faces (one segment is cast against the previous one so the faces fit exactly). During erection, a thin layer of epoxy is applied between segments, and post-tensioning tendons are threaded through ducts cast into the segments. When the tendons are stressed, they squeeze the segments together with enormous force, creating a structure that behaves as a single monolithic beam. The post-tensioning also creates compressive forces in the concrete that counteract the tensile stresses from bending under traffic loads. In balanced cantilever construction, temporary post-tensioning holds the cantilever arms in place during erection, and permanent continuity tendons are installed after the cantilevers from adjacent piers meet.
The Sunshine Skyway Bridge replacement in Tampa Bay, Florida was one of the first major cable-stayed segmental concrete bridges in the United States. Its precast segments were barged to the site and lifted into place by crane, with each 80-ton segment placed in just 45 minutes.
Linn Cove Viaduct (Blue Ridge Parkway, North Carolina)
Sunshine Skyway Bridge (Tampa Bay, Florida)
I-35W St. Anthony Falls Bridge (Minneapolis, MN)
Chesapeake & Delaware Canal Bridge (Delaware)
Mid-Bay Bridge (Florida)
Veterans Memorial Bridge (Texas)
| Rank | State | Count | % of Type |
|---|---|---|---|
| 1 | Florida | 91 | 21.6% |
| 2 | Massachusetts | 61 | 14.5% |
| 3 | Texas | 60 | 14.3% |
| 4 | Colorado | 17 | 4.0% |
| 5 | Indiana |
There are 421 segmental bridges in the United States.
Iconic bridges with a deck hung from cables draped over tall towers, capable of spanning enormous distances.
Modern bridges where cables run directly from towers to the deck, creating a dramatic fan or harp pattern.
One of the oldest bridge forms, using a curved structure to transfer loads outward to abutments at each end.
Bridges built from interconnected triangular elements, combining strength and material efficiency.
| 14 |
| 3.3% |
| 6 | Minnesota | 14 | 3.3% |
| 7 | New York | 12 | 2.9% |
| 8 | North Carolina | 12 | 2.9% |
| 9 | California | 11 | 2.6% |
| 10 | New Mexico | 9 | 2.1% |