An arch bridge is a type of bridge where the main supporting elements are arches. The bridge has abutments at each end shaped as a curved arch, which work by transferring the weight of the bridge and its loads partially into a horizontal thrust held by the abutments at either side. The arch carries the load directly to the abutments or supports as compressive forces, and bending moments and shear forces are small compared to girder bridges, making it a more economical choice. The abutments/supports are one of the most important components of arch bridges because most of the loads carried by the arch rib are transmitted into the abutments. Arch bridges can be made of stone, concrete, iron, or steel and typically require less material than other types of bridges.

There are three main types of arch bridges being built nowadays: deck arch bridges, through arch bridges, and tied-arch or bowstring arch bridges. In deck arch bridges, the deck lies on top of the arch rib, while in through arch bridges, the deck passes through the arch. Tied-arch or bowstring arch bridges have a horizontal tie between the arches at the bottom of the bridge, which helps to reduce the horizontal thrust against the abutments.

Arch bridges have been used for over 3000 years and have evolved over time as engineers came to better understand the possibilities inherent in different materials. Until the 1800s, most arch bridges were constructed of stone, and such masonry arches have several great advantages over horizontal stone beams, or lintels. Modern arch bridges are made from reinforced concrete, steel, or laminated wood, which are highly rigid and lightweight, so that the horizontal thrust against the supports is small.

In summary, an arch bridge is a type of bridge where the main supporting elements are arches, and the bridge has abutments at each end shaped as a curved arch. The arch carries the load directly to the abutments or supports as compressive forces, and bending moments and shear forces are small compared to girder bridges, making it a more economical choice. Arch bridges can be made of stone, concrete, iron, or steel and typically require less material than other types of bridges.