A bridge abutment is a vertical structure that connects the deck of a bridge to the ground. It is constructed at the end of a bridge span. It transmits weight from the bridge superstructure to the ground. It also connects the bridge to the roadway and retains the roadway base materials from the bridge spans. Bridge abutments are built with brick masonry, stone masonry, precast concrete blocks, and RCC. They come in different shapes and sizes. The type of abutments selected is determined by available space, geologic factors of the bridge site, and project budget.
Functions of the Bridge Abutment
- Support for the bridge deck
- Retain earth pressure on the embankment
- Transfers the load on the bridge to its foundation
- Maintain equilibrium in the bridge by resisting vertical and horizontal loads
Components of the Bridge Abutment
- Bridge Seat: A top-surface horizontal shelf on an Abutment supports the bridge deck. They hold on to the end span of the embankment.
- Wing Wall: These walls are used when a bridge is connected to an embankment. It is a short wall used to prevent the structure from soil erosion.
- Back Wall: It is placed above the bridge deck and is utilised to support the embankment. It is the filament that connects the ground soil to the bridge seat Abutment.
- Footing of Abutment: It connects the pile to the ground. It consists of a horizontal surface that distributes the weight.
Types of Bridge Abutments
Full-height Abutment
A full-height abutment is constructed at the lower level of the roadway and is used in congested urban and metropolitan areas where structure depth is critical.
Gravity Abutment
The Gravity abutment comprises of the bridge seat, back wall, footing, and wing walls that resist soil and water pressure. It is constructed on the ground, and gravitational pull is its key element for its durability.
U-shaped Gravity Abutment
A U-shaped Abutment comprises a set of piles constructed with cement. This bridge Abutment type is placed at a 90-degree angle to the bridge’s seat.
Cantilever Walls Abutment
Cantilever wall abutment retains soil behind the bridge’s ends and the other supports the bridge superstructure.
Stub Abutment
A stub abutment is placed at the top of fill embankments. It is used to retain soil.
Semi-Stub Abutments
A semi-stub abutment is constructed between the top and bottom of an embankment. It is also used for retaining soil.
Integral Abutment
The integral abutment is placed on a single row of flexible piles and constructed without joints. It allows for expansion and contraction through movement at the abutments.
Mechanically Stabilized Earth Abutment
The Mechanically Stabilized Earth (MSE) consists of precast concrete panels, metallic soil reinforcing strips, and backfill to support the superstructure and support the roadway approach roadway embankment.
Counterfort Abutment
The counterfort abutment joins the wall to the footing. These counterfort walls are built at regular intervals to reduce the shear force and bending force imposed on the wall.
Spill-Through or Open Abutment
A spill-through or open abutment is used to decrease the amount of soil pressure on the abutment.
Pile Bent Abutment
The pile bent abutment replaces the wall-like supports with a series of piles, or columns, to hold the support beam. It consists of a series of piles or columns to provide support to the structure.
Conclusion
Discussed above are different types of pile abutments and their use in bridges. The required number of abutments is determined by the length of the bridge. Usually, for small bridges two abutments are installed but according to the bridge’s length, the additional abutments can also be installed.
Analysis of Different types of Bridge Abutments
Functions of the Bridge Abutment
Components of the Bridge Abutment
Types of Bridge Abutments
Full-height Abutment
Gravity Abutment
U-shaped Gravity Abutment
Cantilever Walls Abutment
Semi-Stub Abutments
Integral Abutment
Mechanically Stabilized Earth Abutment
Counterfort Abutment
Spill-Through or Open Abutment
Pile Bent Abutment