My name is Lauren, and Im a secondary school student in Ontario. For my gr11 advanced math class I have to find out how and why parabolics are used in arch bridges and write 3 paragraphs on it. People who cohse satelites and whatnot are lucky  I've found a ton of info, but for arch bridges there seems to be nothing. PLEASE HELP ME!!! I'm soooo desperate becasue I cant find anything except pictures! Thank you. Looking forward to your response, ~Lauren~ Hi Lauren,There are two curves with very similar shapes that are important in bridge construction. One is called a catenary and the other a parabola. The best two references I could find have to do with suspension bridges, but the princilpe is the same. If you hang a cable between two towers, as you see in power lines, the curve you see is a catenary. If you hang a bridge from a pair of such cables by vertical cables that are uniformly spaced along the length of the bridge, then the curve of the suspension cables becomes approximately a parabola. The first reference I found, Suspension bridges says: In the second reference if you scroll down to "Catenary and parabola" there is a further explanation. I also found a page with definations of terminology in the bridge and tunnel induster that saya: a form of arch defined by a moving point which remains equidistant from a fixed point inside the arch and a moving point along a line. This shape when inverted into an arch structure results in a form which allows equal vertical loading along its length. A famous example of this shape is the Gateway Arch in St. Louis, MO. Harley
