ABSTRACT
Any architectural feature which is not supported at its extremity can be described as a cantilever. The foregoing description and analysis of a cantilevered beam has emphasized the identity of a cantilever as an extension of an otherwise simply supported or continuous beam. The propped cantilever is not so much a deliberately devised structural form as an acceptance of support conditions beyond the control of the designer. The system effectively consists of a simply supported central span resting on the ends of two cantilevered beams. The effect of unequal fixing moments from adjacent cantilevers as a result of a train crossing the bridge is to alter the value of each of the vertical support pairs, increasing one and decreasing the other. The essential role of all four upper Ionic columns becomes one of creating fixity by preventing the stone below it from rotating about the top of the Doric column supporting it..
