What is a bridge abutment?
A bridge typically consists of two main parts, the substructure and the superstructure. The substructure of a bridge includes the abutment, which supports the soil on which the bridge sits. Additionally, substructure can also refer to the piling, which transfers the bridge loads from the bridge into the piling and into the deeper layers of the soil. The substructure might also have wing walls, which retain the soil along the sides of the bridge abutment.
The benefits of sheet pile bridge abutments
Steel sheet pile bridge abutments are an innovative solution which provides savings in time and cost on many types of bridge projects. The basic concept of this solution is that the sheet piles can provide both the temporary formwork for the construction of the bridge, as well as the final abutment face and piling support for the bridge deck.
Steel sheet pile bridge abutments are considered an accelerated construction method, significantly reducing the overall construction time in many cases. With a concrete abutment, formwork must be built, concrete poured, and curing time allotted to enable the concrete to achieve its design strength. With a steel solution, the sheet piles are able to begin carrying loads on the day theyare installed and do not require any formwork.
A sheet pile bridge abutment solution is compact, allowing the abutments to be brought closer together to reduce the span length. Reduction of the span length provides overall reduction in the cost of the superstructure. Additionally, due to the compact nature of this solution, disruption of natural streams can be avoided and in-water permitting can be simplified or avoided altogether.
Another added benefit to this solution is the built-in scour protection when crossing a river or stream. With traditional concrete bridge abutment and piles, significant scour can erode the soil under the concrete abutment, undermining its integrity and requiring repairs. Steel sheet piles are driven much deeper into the soil than a concrete abutment, providing significant automatic scour protection. Pile lengths can be specified and purchased at long lengths to meet long-term scour estimates, ensuring bridge durability.
Abutment construction process
There are many different construction methods for bridge abutments which utilize steel, concrete, geosynthetics, and other materials. Abutments can be integral, where the bridge and the abutment move together, or semi-integral, where the abutment and the superstructure move independently when responding to forces on the bridge. There are pros and cons to each type of bridge abutment and construction method. Review your local Department of Transportation’s guidance regarding types of bridges that are acceptable or recommended in your state.
Sheet pile bridge abutments are constructed by first installing the sheet piles for both the abutment face and the wing walls. Tie rods and a deadman wall are required in some high-load applications. Additional pilings behind the sheet piles can be used if insufficient bearing and skin friction capacity cannot be obtained with the sheet piles themselves. From there, soil backfills behind the sheet piles and construction of the concrete cap and bridge deck can proceed. As described, it’s clear to see that this solution eliminates a lot of construction stages, and therefore can eliminate a significant amount of time and show increased cost savings.
Sheet piling offerings
Nucor Skyline offers NZ, PZ, and SKZ sheet piles which are made in America and meet federal Buy America guidelines. This product range is suitable for any Department of Transportation (DOT) project you may have in design. To see some examples of how sheet piling is used for bridge abutments, please click here to visit our case studies.