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Segmental bridges are built in—as the name implies—segments. This offers a variety of benefits, including a reduction of the footprint required to construct piers, superstructures that can easily travel over natural hazards and landmarks, and a flexible bridge radius.

Every bridge can be divided into two main parts: the substructure and the superstructure. The substructure acts as the foundation of the structure. All piers, abutments, and other support elements fall under this category. Any remaining items above the substructure make up the superstructure.

While the substructure portion of a segmental bridge is virtually indistinguishable from other types of bridges, the superstructure is where things begin to diverge. Segmental bridges lack basic elements that make up a traditional bridge design. They don’t use girders, which typically act as the primary structural supports for the bridge deck due to their high load-bearing capabilities. Instead, their design is fully integral—it’s one complete structure that’s held up with post-tensioning.

All segmental bridges are concrete structures, but the segments come in two types: precast and cast-in-place. Precast segments are poured offsite and brought in on either trucks or barges. This speeds up the erection process, as the concrete doesn’t have to cure onsite. Sometimes, these segments can be too heavy to transport, or the landscape makes it difficult to deliver them, which is where cast-in-place segments come in handy. For the purpose of this post, we’ll be focusing on cast-in-place construction—the kind of bridge Fay, S&B USA Construction is building at our Beaver River Bridge project.

As part of this project, Fay, S&B USA Construction is completing two 1,645-ft 5-span cast-in-place segmental bridges; these new structures will stand 200 ft above the river (which is 20 ft higher than the existing bridge). While segmental bridges are not uncommon, they are unusual to Pennsylvania. There are only two others in the surrounding area: the Turnpike’s Allegheny River Bridge in Harmarville and the Mon Fayette Bridge in Denbo. They’re more common in Israel, where our parent company, Shikun & Binui Ltd., is located. Due to their familiarity with the techniques used, Fay, S&B USA Construction requested experienced individuals from Shikun & Binui Ltd. to aid us during the construction process.

Our bridges at Beaver will be constructed using a balanced cantilever construction process, which is completed in the following series of steps:
Most of segmental bridges’ defining features occur during construction—it’s difficult to tell when a bridge was created using segmental construction techniques after it has been completed. If you’re beside or underneath it, you may be able to pick out faint lines that differentiate between pours, but if you’re driving over top of one, the differences are negligible.

As engineering demands evolve and innovative solutions become increasingly sought after, the segmental cast-in-place balanced cantilever approach will remain an appealing option for overcoming construction challenges and advancing the field of bridge design.