What Is Segmental Bridge? How Segmental Bridge Construct?
WHAT IS SEGMENTAL BRIDGE?
A Segmental Bridge is a bridge built in short sections (called segments), that is one piece at a time, and then segments are erected to make the bridge. The bridge is either cast-in-place or precast.
ADVANTAGES OF SEGMENTAL BRIDGE
- Very economical for long spans.
- Prefabricated segments provide more quality control.
- The structure can be fully loaded immediately after being pre-stressed.
- The pre-stressed cables can be inspected and replaced at all times.
- Low weight due to thin bridge sections.
- Industrialization of the construction process.
- Innovations in construction equipment.
- Low maintenance costs.
- Speed of construction, time taken less
DISADVANTAGES OF SEGMENTAL BRIDGE
- High construction loading or high technology is used.
- Need high safety precautions during construction
- Extra cost (due to more pre-stressing required)
Segmental bridges are classified under the following Categories.
- Balance Cantilever Bridges
- Progressive Placement Bridges
- Span-by-Span Constructed Bridges
- Incrementally Launched Bridges.
Construction of segmental Bridges
The following steps are used for the construction of Segmental bridges.
- Casting of Segments
Two method used for casting of segments
- Short Line Method
In this rate of segment production is slow. Three or four segments cast at a time.
- Long Line Method
In this rate of segment production is fast. Segments equal to one span cast at a time.
After casting the segments are stored at staking yard and curing of segments will be done.
- Transfer the segment at erection site.
After casting or curing of segments are transferred at erection site with the help of traveler or crane.
- Erection of the segments:
The precast segments are erected on the sites by following erection methods.
- Balanced Cantilever erection
- Progressive Placement erection
- Span by Span erection
- Incremental Launching erection
High Machinery are used for the erection of segments some of the following.
- Launching Truss & accessories
- Launching girder & accessories
- Gantry crane or other cranes
- Hydraulic jacks
- Epoxy Glueing
In between the two segments epoxy Glueing is used to prevent the leakage of grout during grouting.
- External per-stressing
Used for giving the final strength to bridge.
- Pre-tension method
- post tension method
The main purpose of grouting is to protect the all strands against corrosion and develop the bond between prestressing steel and surrounding concrete.
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