arch bridges
Introduction
An arch bridge is a bridge with supports located at the ends of the span "Light (engineering)") to be bridged, between which there is an arch-shaped structure "Arch (architecture)") with which the loads are transmitted. The deck can be supported or hung from this main structure, giving rise to different types of arch bridges depending on the relative position of the deck with respect to the arch.
Arch bridges work by transferring the own weight of the bridge and the use overloads to the supports by compressing the arch, where they are transformed into a horizontal thrust and a vertical load. [1] Normally the slenderness of the arch (ratio between the maximum arrow and the span "Span (engineering)") is high, making the horizontal forces much greater than the vertical ones. For this reason they are suitable in places where the support foundations are capable of providing good resistance to horizontal thrust.
When the distance to be covered is large, they can be made with a series of arches, although it is common nowadays to use other, more economical structures. The ancient Romans already planned structures with multiple arches to build bridges and aqueducts.
These types of bridges were invented by the ancient Greeks, who built them in stone. Later the Romans used cement in their arch bridges. Some of those old bridges are still standing. The Romans used only semicircular arch bridges, but longer and slender bridges can be built using elliptical or inverted catenary figures.
Simple Compression Arch Bridges
Advantages with the use of simple materials
Stone and many similar materials are resistant to compressive stresses, and somewhat resistant to shear stresses. But tensile stresses are very weak, which is why many arch bridges are designed to work constantly under compression. In construction, each arch is built on a temporary arch-shaped formwork. In early compression arch bridges, a keystone in the middle of the arch distributes the weight to the rest of the bridge. The more weight is put on the bridge, the stronger the structure becomes. Masonry arch bridges use an amount of fill (typically compacted gravel and gravel) over the arch to increase the dead weight on the bridge and thus prevent points of the arch from going into tension, which could occur when loads move across the bridge. Mass concrete (unreinforced) and brick are also used to build this type of bridge. When using stonework (cut stone) the angles of the faces are cut to minimize shear stresses. When masonry (uncut and unprepared stones) is used, a mortar is used between them and the mortar is applied and allowed to harden before the formwork is removed.