Civil Engineering PE

Answer: D - The only arch design type that is statically determinate is the three-hinged arch. Because horizontal forces are always acting on an arch (including its own weight), an arch must be fixed that its support so that it does not flatten out. Two reaction components are present at each support (horizontal and vertical). Three-hinged arches are commonly used for shorter bridge spans (less than 600 feet long) and for structures that require large interior spaces (for example, airplane hangars and gymnasiums).