Why Do Bridges Use Arches

After more than 2,000 years of architectural use, the arch continues to feature prominently in bridge designs and with good reason: Its semicircular structure elegantly distributes compression through its entire form and diverts weight onto its two abutments, the components of the bridge that directly take on pressure.

Why do some bridges have arches on top?

Bridges featuring arches were among the earliest large-scale engineering and construction projects. Arch bridges can span vast areas because they transform the forces affecting them into compressive stresses, which eliminates tensile stresses. (This is often referred to as “arch action.”)

Why do arches work?

Arches work by transferring the load through the arch to the supporting foundation via the abutments. As the load tries to straighten out the arch, the outward movement is resisted by the abutments and the downward force is transferred to the foundation.