Construction of Segmental Bridge

by ce on November 21, 2014

A segmental bridge is a bridge built in short parts (called segments), i.e., one piece at a time, as opposed to traditional methods that build a bridge directly in full length. The bridge is made of concrete that is  either cast-in-place (constructed fully in its final location) or precast concrete (built at another location and then transported to their final location for placement in the full structure). These bridges are very economical for long spans (over 100 meters), especially when access to the construction site is restricted. They are also chosen for their aesthetic appeal.

Sequence of construction is similr to traditional concrete bridge builiding, i.e., build the support towers (columns), build the temporary falsework, build the deck, perform finish work. The principle differences are as follows:

  1. The support towers may be built segmentally. Often this is accomplished using “slipform” construction, where the falsework moves (slips) upward following sequential concrete “pour.” The falsework uses the newly constructed concrete as the basis for moving upward.
  2. After the towers are built, a superstructure is built a top of towers. This superstructure serves as the “launcing” point for building the deck. (The deck is often built in both directions away from the tower, simultaneously.)
  3. The deck is now constructed sequentially, beginning at the tower, one section at a time. 
    • In cast-in-place bridges, the falsework is connected to the previously installed concrete and allowed to cantilever freely. Next, the permanent reinforcing steel and supports are installed. finally, the concrete is place and cured, freeing the falsework to be moved.
    • In pre-cast bridges, the concrete segment is constructed on the ground, and then transported and hoisted into place. As the new segment is suspended in place by the crance, workers install steel reinforcing that attches the new segment to preceding segments. Each segment of the bridge designed to accept connections from both preceding and succeeding segments.
  4. The process in step 3 is repeated until the span is completed.

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