What Is Bridge Abutment? What Are the Types of Abutments? Importance of Bridge Abutment

What Is Bridge Abutment? | Uses of the Abutment in Engineering | Bridge Abutment Vs Piers

What Is Bridge Abutment?

A bridge abutment is a structure that projects from the side of a bridge to form an angle with the main span.

Bridge abutments are designed to resist lateral forces on the bridge. Bridge abutments also help support the weight of bridges, and act as structural supports for the roadway and train tracks below them.

Bridge abutments come in many different shapes and sizes, but generally it’s an area where they meet at a right angle near one end and slope down towards each other at an angle in between.

Bridge abutments are structures that support a bridge across water or land. They are used alongside the banks of a canal or river, and they can be constructed from concrete, brick, steel, masonry or timber.

An abutment is the support that carries a bridge’s superstructure. Each end of a bridge’s span is supported by one abutment, and each abutment contains pilasters (columns) and wing walls to support the bridge as well as an embankment for the roadway approach.

An abutment serves as a platform for the bridge portion of a structure that spans a river or canal and is also used to resist ground pressure caused by the weight of the superstructure.

Situated on both sides of the waterway, an abutment maintains its relationship with the embankment it rests against.

What Are the Types of Abutments?

A bridge is a structure that spans a gap of water, which has the ability to carry loads and is designed to support its own weight as well as those of the loads it carries.

The two parts are known as abutments and piers. The abutment is positioned on one side of a channel or gap and rests on bedrock or other supporting material. The opposite end has the pier, which supports the structure.

Types of Abutments include:

1. Gravity abutment: A gravity abutment is constructed of mass concrete and is usually narrow enough to span the entire width of the canal it crosses. It carries its own weight and any additional water load caused by rain or runoff.
2. Under-reamed abutment: An under-reamed abutment is very similar to a gravity abutment, but it also incorporates a system for collecting and discharging any ground water that might flow into the canal through cracks in the earth at the place where the opposite sides of the canal meet.
3. Cantilever abutment: A cantilever abutment is constructed on the side of the canal that faces away from the road. It is often wider than the waterway so that if there is any seepage or leakage, it will gather on the outer surface rather than get behind the structure.
4. Arch-support abutment: An arch-support abutment carries its own weight and also supports the weight of a deck truss bridge or another type of structure. It carries about two-thirds of the bridge’s weight and the deck truss structure carries the remaining third of the bridge’s weight.
5. Dressed abutment: The dressed abutment is a concrete chamber that is hollowed out in its center, leading into and out of the side of a canal wall. The bridge segment rests on its sides within this artificial fissure, supported on top by masonry pilasters or piers which hold up an overhead cantilever section.
6. Counterfort abutment: A counterfort abutment is constructed with its top heavily reinforced, in order to support the weight of the canal. Counterfort abutments are often topped with concrete walls or steel guard rails, which offer protection to pedestrians.
7. Deck-girder abutment: A deck-girder abutment is constructed in a manner similar to a dressed abutment, except that it lacks the central chamber and instead supports the bridge segment directly on top of its pilasters or piers.
8. U abutment: U abutments are constructed in the shape of an inverted “u” and carry the weight of a bridge on their backs, although they may be reinforced with pilasters to increase the amount of weight they carry.

Uses of the Abutment in Engineering

The abutment can be used in various ways. For example, an abutment is used to support the overhang of canal bridge piers, which may need to be wider than the width of the waterway.

Abutments also need to support tall bridges or bridges with high horizontal spans

In summary, the bridge abutment is used to;

• Load transfer from a superstructure to its base components
• Self-weight, lateral loads (such as ground pressure), and wind loads must be resisted or transferred.
• To provide support for one end of an approach slab
• To maintain a balance between an arch bridge’s vertical and horizontal force components.

Bridge Abutment FAQs

1. What Is Bridge Abutment?

An abutment is a foundation that supports the superstructure at the ends of a bridge span or dam.

Abutments at each end of a single-span bridge offer vertical and lateral support for the span while also functioning as retaining walls to oppose lateral movement of the earthen fill of the bridge approach.

Piers are needed to hold the extremities of spans that are not supported by abutments on multi-span bridges.

Dam abutments are often the walls of a valley or canyon, but they can also be man-made to support arch dams.

2. What is a bridge abutment wall?

The abutment wall is a wall built near the banks of a river to strengthen the side of a bridge.

An abutment wall is generally a retaining wall supporting the ends of a bridge, and, in general, retaining or supporting the approach embankment.

3. What is the purpose of bridge abutment?

The purpose of a bridge abutment is to provide support for a structure. It supports one end of an approach slab or walkway, and it transfers weight from its superstructure to its base components beneath the ground or water.

4. Why is an abutment important to bridges?

Abutments are used at bridge ends to maintain the embankment and transmit vertical and horizontal stresses from the superstructure to the base.

Abutment foundations must also be built to prevent differential settling and excessive lateral displacement.

An abutment usually acts to support the ends of a span across a river or canal, and it is also used to provide support for an approach embankment.

Abutments are needed to resist vertical and lateral forces as well as ground pressure, which can be transmitted to the superstructure from the bridge.

5. What types of abutments are there?

There are many different types of abutments because each is necessary for different bridges.

Gravity abutments are constructed of mass concrete and are usually narrow enough to span the entire width of the canal they cross.

The most common form of the abutment is the conventional gravity abutment, which contains the bridge seat, backwall, footing, and wing walls to support the bridge’s deck as well as a retaining wall for the embankment.

The wing walls are often set parallel to the bridge seat or at a little backward inclination into the embankment.

U-Abutment is another type of abutment that varies from a gravity abutment in the angle of the wing walls. These are positioned perpendicular to the bridge seat and extend toward the embankment and away from the bridge.

Cantilever abutments support a bridge structure on their outer surface while allowing groundwater to drain away from its inner side.

Spill-through abutments often sustain the bridge at regular intervals along its span. While there are no wing walls or backwalls to keep the embankment in place, the deck is supported by columns or a short wall. Water and roads can pass between the supports.

The support structure’s length varies to accommodate the distance between the level bridge and the varying terrain below.

The pile bent abutment is a spill-through abutment variation that replaces the wall-like supports with a sequence of piles, or columns, to sustain the support beam.

6. What is difference between abutment and pier?

A pier is a column that supports a load, while an abutment is a wall that resists lateral forces.

An abutment supports and transfers the weight of an entire structure to the earth in front of it, while a pier supports only a segment of the structure and adds no lateral resistance.