A segmental bridge is constructed in the little parts (called segments), as compared to traditional techniques that are created in extremely big portions.
The bridge is comprised of either cast-in-place (completely completed in its final position) or precast concrete.
In this article you’ll learn:
- Intro of the segmental bridge.
- Types of the segmental bridge.
- Merits and Demerits segmental bridge.
- Lots more.
So, if you’re ready to go with a segmental bridge this article is for you.
Introduction to Segmental Bridge:
Segmental bridge construction initially debuted in the early 1950s.
In 1950, the first cast-in-place segmented concrete bridge was built in German, spanning the Lahn Riverbed.
The very first precast segmental concrete bridge was erected across the Seine River in France in 1962.
Segmental Bridge Construction:
Segmental bridges are built using the procedure described here.
1. Segment Casting:
In a particular variable casting machine, each segment is cast next to the preceding segment.
When built, this guarantees that the connection between the two segments fits perfectly.
The following part is then cast adjacent to the preceding one.
Segment casting can be accomplished in two ways.
Short Line Method:
The pace of segment manufacturing in this method is sluggish. Three or four portions are cast at once.
Long Line Method:
At this pace of segmental bridge, production is quick. Casting one spanning segment at a period.
After casting, the segments are stored at the staking yard, where they will be cured.
2.Transfer the segment at the erection site:
The segments are kept at the staking station and will be cured there.
3. Erection of the segments:
The precast segments are constructed on the job sites according to the techniques outlined below:
- Balanced Erection of a cantilever.
- Progressive Erection of a placement.
- Erection of spans by spans.
- Incremental Starting an erection
Some of the following portions are erected using high machinery.
- Launching Trusses and accessories.
- girder for launch and accessories.
- Cranes such as gantry cranes and various types of cranes.
- Jacks for hydraulics.
4. Epoxy Gluing:
Epoxy Gluing is utilized between the two segments to prevent grout from leaking during grouting in segmental bridge.
5. External prestressing:
This is used to provide the final strength to the bridge.
Methods of pretension.
Method of posttension.
The primary goal of grouting is to preserve all strands from corrosion and to strengthen the link between prestressing steel and surrounding concrete.
Classification of Segmental Bridges:
Segmental bridge are categorized into the following categories.
Balance Cantilever Bridges:
Balanced cantilever bridges are utilized for longer spans when simply supported, continuous, or rigid frame superstructures are inadequate.
Bridges with spans greater than 20 to 25 m are simply supported; Necessitate deeper depths hence become economically unfeasible.
Progressive Placement Bridges:
Progressive placement is comparable to span-by-span construction in that both begin at one end of the building and work their way to the other.
Precast portions are gradually put in subsequent cantilevers on the same side of the same bridge in progressive placement.
Temporary stays with temporary towers are erected on the pier for progressive placement to reduce cantilever strains and deflections.
Span-by-Span Constructed Bridges:
A span-by-span construction approach is a most popular, simplest, and typically most cost-effective way for precast segmental bridge.
It is often focused on long bridges with a large number of 25-45m spans with a large plan radius, and it is suitable with simply-supported and continuous sections.
Span-by-span construction bridges, in which parts are cast on opposite sides of the same pier to offset the hogging moment at the pier.
Incrementally Launched Bridges:
The incremental launch is an engineering method of creating a complete bridge deck from one bridge abutment alone, with the superstructure of the bridge built in segments to the opposite side.
Advantages of Segmental Bridge:
- For large distances, it is quite cost-effective.
- Prefabricated portions provide for greater quality control.
- After prestressing, the structure may be completely loaded immediately.
- At all times, the pre-stressed cables may be examined and replaced.
- Because of the thin bridge components, the bridge is light.
- Construction procedure industrialization.
- Construction equipment advancements.
- Low operating expenses.
- Fast Construction speed.
Disadvantages of Segmental Bridge:
- High construction loads or high technologies are employed.
- High safety precautions are required during construction.
- Extra expense (due to more prestressing required).
Also read: Types of Bridges | Cantilever Bridge | Accelerated Bridge Construction
Segmental Bridge technology is great for bridge-building that provides an aesthetically pleasing view or high quality.
Long bridge construction is now simple, these are environmentally friendly building.
This approach heavily automates the construction line.