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The hinged archesinvolve three hinge arrangements: single-hinged type, two-hinged type, and three-hinged type. In arch bridges, two hinges or three hinges are frequently used. The two-hinged arch has pins at the end bearings, so that only horizontal and vertical components of force act on the abutment. The two-hinged arch is most often used to bridge long spans. The three-hinged arch has a hinge at the crown as well as the abutments, making it statically determinate and eliminating stresses due to change of temperature and rib shortening. In addition, the less complex forces on the bases can simplify the foundation design. Three-hinged arch also has obvious drawbacks. For example, three-hinged arch bridges have smaller rigidities and therefore experience much more deflection. In addition, the hinges are complex in fabrication. Steel arch bridge can be built as either hingeless (fixed) or hinged.
