A bridge abutment is a unique structure located at the ends of an overpass span connecting the bridge’s deck to the ground. It supports the weight of the platform vertically and horizontally. So, the bridge conveys importance to the bridge’s foundation from the superstructure at the end of the bridge.
It plays the role of retaining the materials used to make the roadway base from the spans at both ends of the extension and connecting the bridge to the roadway. If constructed on a river, it serves to protect the dam from the force of the stream. The materials used in making link support can be reinforced concrete or masonry plain concrete. This link https://www.builderspace.com/4-best-materials-for-building-bridges has more on bridge construction materials.
The abutment can be trusted for transferring loads from a structure to the foundation elements. It can equally transfer lateral loads, self-weight, and wind loads. Furthermore, it can provide support for one end of an approach slab. It is used extensively for maintaining a balance between the arch bridge’s horizontal and vertical force components.
Short and Long Bridges
A short overpass can use one support satisfactorily, and reliance can be placed on any of the sides of the platform. The two will be connected to the retaining walls and embankment. Connection to the retaining wall is not always the case.
If the extension is longer, it will come with a different abutment, and this can be placed along the span or length of the extension. Once installed, it offers essential support for the bridge at particular intervals. The longer links do not come with a vertical wall, but they provide vertical support satisfactorily.
The space available can determine the particular type to go for between the long and short supports during bridge construction.
The project site’s public funding and geological features can equally determine the right to choose between the long and short types.
Types of Abutments
The various types of bridge abutments are discussed below:
- Pile Bent
- Spill-through or pedestal bridge
- Typical Gravity
- Closed bridge
This represents a full-height wall bearing wing walls on both sides. They are put in place to retain the height of the approach embankment. This type comes with a minimized span length of the abutment. It is, however, not a good choice for soft foundations and high embankments. It is crucial first to construct the abutment before the embankment adjacent.
It is usually difficult to make proper compaction and placement in areas like the middle of the wing walls. The wall may go out of vertical alignment and lateral if the backfill is compacted using heavy equipment. The backfill weight can increase the foundation’s compression and also benefit the post-construction settlement.
This type is considered the most common type of support. Its many features include wing walls, footing, back wall, and bridge seat. It helps the deck of the link ideally and also features a barrier for the embankment. The wing walls are usually arranged parallel to the connection seat. The angle may also be slightly backward and dip into the embankment. This type uses its gravity for resisting horizontal pressure.
This is different from the gravity Abutment only in the angle you can find in the wing walls. It is perpendicularly placed at the platform’s seat, and it extends in the direction of the barrier, with its angle not in the direction of the extension. As its name implies, this type comes with the U-shape.
This provides periodic support for the bridge via its span. It does not come with back wall or wing walls for retaining the embankment, but the deck is supported by a specially created beam, which is in turn aided by short walls or columns. It is wide enough to permit easy passage of roadway and water under it.
This is related to the spill-through type of Abutments. It is referred to as the variant of this type of Abutment. It includes a series of piles, holds, and supports that work to replace the wall-like support for the beams.
There are several other types, but the ones we have mentioned above are the most common ones that you should focus on as far as Abutments are concerned.
There are five components of Abutment, and you can find these components in such Abutment located on either side of the bridge. If the Abutment is located close to the bridge span, such an Abutment will not have the back wall and the wing walls. The various components are discussed below:
It is a shelf placed horizontally to provide support for the bridge deck. It can be on top or close to the top of the Abutment. It helps in holding the span end and those located along with the span work by reducing stress.
You can only find them in Abutments connected to the embankment. The retaining walls are short, and this keeps erosion at bay. They can equally be trusted for stability aside from erosion prevention.
You can only find them in an embankment abutment. They brace the embankment horizontally from the bridge deck, as wells, reduce the frequency of erosion at the point of connection. You can find more here on the usefulness of back wall in construction.
It can either be a column row that connects the foot with the seat or a vertical wall for the same purpose. The vertical structure offers a retaining wall, and the mid-span abutment features cost-effective columns.
This part is responsible for connecting the vertical portion of the bridge that bears the load to the ground. It is usually buried deep into the ground. Its horizontal surface can be broad, and this helps with effective weight distribution.