If you are a contractor working with large earthworks, building roads, or transforming entire cities, the word abutment is not new to you. You understand the concept because you’ve built them, studied them, and you have seen what goes wrong when they are incorrectly done.
But in fact, if you have ever built something with Legos, or Lincoln Logs, or some other material, and then you tried to help it hold weight, you inadvertently were studying abutments, even if you didn’t know it.
An abutment, in short, is what holds up a bridge or other piece of construction that does not rest directly on pilings and the ground directly beneath it.
How does an abutment work?
The abutment in a construction design is Atlas at the bottom of the earth, holding everything else up.
The abutment rests firmly on the ground, and likely has piling dug deep into the soil and clay below. It had to be firm and steady, because it will end up holding a great more width than just the abutment itself.
The bridge, or other piece of construction (this is true for porches and other items that may extend out), is held in place on the abutment, and any weight that goes onto the bridge is transferred to the abutment.
That is, when you are driving and you get part way across the bridge, though you may feel as if the weight of your car is being held by the surface below you, there are actually complex forces at work.
The platform you are on is holding your weight at the moment, but it is not what is keeping your weight off the ground. That is, it is transferring your weight to an abutment. It is this abutment that truly holds the weight.
What does abutment mean?
It might help to know that to “abut” means to touch by way of a mutual border. That is, to share a common space or border. An abutment has a bridge or other span resting on it. This mutual space includes both the span and the abutment.
So if one thing is resting or placed against another, it can be said to be abutting it. In the case of a bridge, however, there is a permanent and secure seal. This allows the abutment and the span to work together to safely deliver you to the other side of the water below.