Bridge Abutment: Types & Components

A bridge abutment is a structural element that supports the end of a bridge and transfers the weight of the bridge and its load to the underlying foundation. It is typically made of concrete or masonry and is designed to resist lateral and vertical forces generated by the bridge deck and its load.

Bridge abutments come in various shapes and sizes and can be designed to match the architectural style of the bridge and the surrounding environment. Some common types of abutments include wing walls, rubble masonry abutments, and reinforced concrete abutments

What Is a Bridge Abutment?

An abutment is an important part of a bridge, which vertically supports the structure of the bridge utilizing for circulating the weight of the bridge. The span of a bridge is associated with embankments by means of abutments.

Abutments Bridge are established on the ground surface. They adjoin the ground and deck of the bridge. The load or weight of the bridge deck is supported by the abutments.

Abutments are vertically positioned within the water or obstacle on a broad and heavy foundation. The abutments withstand the pressure exerted by water flow and soil due to their heavy weight.

Types of Bridge Abutments

The different types of bridge abutments are as follows,

1. Gravity Abutment

Gravity abutment has the function to prevent the horizontal earth and water pressure with its dead weight. The foundation of such abutments is extremely wide and heavy.

As the word mentions, the structure of the abutments is entirely seated on the ground, the gravitational pull of the earth makes the abutment sustainable.

2. U-shaped Gravity Abutment

This butment type has wings perpendicular to the face which performs as counter-forts. These are relatively stable types of abutments. The wing walls of an abutment are at a 90° degree angle (perpendicular) to the seat of the bridge.

A U-shaped abutment has a set of piles, which are at a distance similar to the width of the bridges. These kinds of abutments are constructed with reinforced cement concrete.

At the bottom, both the piles of the abutment are attached to each other utilizing the foundation. Both piles have a common foot.

3. Cantilever Wall Abutments

There are two objectives of a cantilever wall abutment, the first is to retain the soil behind the edges of the bridge, second is to support the bridge superstructure. One of the most popular types of abutment structures is a retaining wall. although.

A retaining wall is utilized to hold back an earth embankment or water and to retain a sudden elevation change. The abutment serves the following functions

Allocating the loads from the bridge ends to the ground resists any loads that are directly imposed on it and gives vehicular and pedestrian access to the bridge. In the case of the retaining wall type Abutment bearing capacity and sliding resistance of the foundation materials and overturning stability must be examined.

4. Full Height Abutments

It is a big height abutment that is constructed at the lower level roadway and should support the whole embankment. This abutment is expensive and is normally utilized in congested urban and metropolitan areas where structure depth is critical.

Full-height abutments are more complicated to build; however, they tend to decrease the length of the end spans.

5. Stub Abutment

Usually supported on piles, they are short abutments established at the top of an embankment or slope of the embankment. They are relatively and not visible from above ground level.

Several wall abutments are referred to as stub abutments. These abutments are created as short as feasible and are established at the top of fill embankments. Stub abutments usually just retain soils that are slightly greater than the superstructure thickness.

Stub abutments can be extremely economical; however, they tend to enhance the length of the end spans. Additional wall abutments can be extensively taller and are often constructed to the full height of the crossing.

6. Semi-Stub Abutments

The height of the semi-stub abutment is between the heights of full height and stub abutment. Unlike stub abutments, others are built on the top or nearby the top of the embankment, also the full-height abutment is formed at the bottom of the embankment.

These abutments are built between the top and bottom of the embankments. As they are bigger than the stub abutments and shorter than the full-height abutment, therefore they are remembered as Semi-Stub abutments.

7. Counterfort Abutment

Counterfort Abutments are the same as the counterfort retaining wall. In the counterfort abutment, a thin wall called a counterfort attaches the breast wall to the footing.

These counterforts are created at spaces of regular intervals so that the breast wall is composed of a supported slab rather than a cantilever.

8. Spill-Through Abutment

The main purpose of the spill-through abutments is to decrease the amount of soil pressure on the abutment by establishing huge voids in the stem.

Piers and Spill-through abutments have equality within them instead the majority of the structure is below grade.

9. MSE(Mechanically Stabilized Earth) System

MSE stands for Mechanically Stabilized Earth. MSE real abutments (no piles) are better cost-effective than different abutments (piles under the bridge seat).

Both are inexpensive compared to conventional concrete abutments and dramatically reasonable in place of concrete abutments on piles.

10. Pile Bent Abutment

The pile bent abutment is a variant of a spill-through abutment that restores the wall-like supports with a string of piles, or columns, to carry the support beam.

Uses Of Abutment

To transfer the loads from a superstructure to its foundation components.
To resist or transmit self-weight, lateral loads (such as the earth pressure), and wind loads.
To support one edge of an approach slab.
To protect a balance between the vertical and horizontal force elements of an arch bridge.

Components Of Bridge Abutment

An abutment has various structural components, abutments placed at either end of a bridge typically include the following five components, which are as under:-

Bridge Seat
Wing Wall
Back Wall
Pile Of The Abutment
Footing Of The Abutment

1. Bridge Seat

The top of the abutment, which includes a broader span than the filament of the abutment, where the deck of the bridge is placed, is called Bridge Seat.

2. Wing Wall

This component of the abutment is just comprised of the abutments which adjoin the bridge with an embankment. These are short retaining walls that prohibit the embankment from erosion.

3. Back Wall

It is also simply contained in embankment walls. Back walls are vertically established at ends of the most bridges. The back walls support the expansion joints of the bridge span or deck.

4. Pile Of The Abutment

The Pile of the abutment is the filament that is attached to the foundation of the abutment using the bridge’s seat. The length of the pile relies on the height of the bridge and the depth of the obstruction (canal, river, and stream).

5. Footing Of The Abutment

The footing of the abutment is similarly called the foundation of the bridge. The footing attaches the pile to the ground. The footing is broader and extremely heavy. The purpose of footing is to avoid the abutment to sink into the ground surface.

Selection Of Abutment

The process of choosing the most appropriate type of abutments can be based on the following consideration,

Construction and maintenance expenses.
Cut or fill earthwork situation.
Traffic maintenance during the construction.
Construction period.
Protection of construction workers.
Availability and expenditure of backfill material.
Superstructure depth.
Size of an abutment.
Horizontal and vertical alignment differences.
Area of excavation.
Aesthetics and similarity to adjoining structures.
Previous experience with the classification of the abutment.
Ease of access for assessment and maintenance.
Expected life, loading condition, and acceptability of deformations.

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Bridge Abutment: Types & Components

What Is a Bridge Abutment?

Types of Bridge Abutments