An abutment in construction is a structure located at the ends of a bridge, serving to retain the soil of the embankment and transfer the loads from the bridge superstructure to the foundation below.
Essentially, it's the "end support" for a bridge. Here's a more detailed breakdown:
Functions of an Abutment:
- Retaining Earth: Abutments prevent the earth embankment from spilling or eroding away at the bridge's ends. They act as retaining walls.
- Load Transfer: Abutments are designed to bear the weight of the bridge deck (superstructure), including traffic loads, and distribute this load to the foundation, which can be soil, piles, or bedrock. This involves both vertical (weight) and horizontal (forces from traffic, wind, etc.) loads.
Key Components:
While designs vary, a typical abutment consists of the following:
- Back Wall: This is the part of the abutment that directly retains the soil of the embankment.
- Wing Walls: These are extensions of the abutment that provide additional soil retention and protect the embankment from erosion. They can be angled or straight.
- Breast Wall (or Stem Wall): The main vertical wall that supports the bridge superstructure.
- Footing: The foundation element that distributes the abutment's load to the underlying soil or piles.
Types of Abutments:
Abutments are classified based on their structural design and function. Some common types include:
- Gravity Abutments: These rely on their own weight to resist the forces from the soil and the bridge. They are typically massive concrete structures.
- Counterfort Abutments: These have vertical supports (counterforts) on the back face to provide additional stability and reduce the amount of concrete needed.
- Pile Abutments: These are supported by piles driven into the ground. This type is used when the soil conditions are poor or when the abutment needs to be elevated.
- Integral Abutments: The bridge deck is rigidly connected to the abutment, eliminating expansion joints. This reduces maintenance and improves ride quality.
Importance:
Abutments are critical components of bridge construction. A well-designed and constructed abutment is essential for the stability and longevity of the entire bridge structure. Failure of an abutment can lead to significant structural damage or even collapse.
