Interaction between Rib and Superstructure in Concrete Arch Bridges

Certain phases of the interaction between the rib and spandrel structure of concrete arch bridges are discussed herein with a view toward relating the action of the structure to the system of classification of indeterminate structures presented in 1935 by Hardy Cross2 M. Am. Soc. C. E. Certain limiting cases of the arch with integral super structure are normal and can be designed directly from the results of a preliminary analysis. Structures in which either the rib or the deck girder develop all the flexural resistance are normal. A third type of structure having normal characteristics for most cases of loading is similar to a Vierendeel truss, with rigid columns and with floor and rib of approximately equal stiffness.