Structural Analysis of an “Ancient Arch Bridge”

The Rainbow Bridge, an arch-shaped truss bridge originally engineered by the Chinese in or before the 12th Century, is of unique curve configuration, piecing together a few unstable trusses into one stable truss assembly which is not only cost-efficient but more structurally sound in terms of lighter dead load than the traditional arch bridge and simple details of member connection. The Rainbow Bridge is revolutionary in its design, it behaves neither like a beam nor like a truss, but a combination of both, and it would better suit today's bridge and other structure design than many existing configurations. This paper aims to briefly examine the structural configuration and behavior of the bridge. A scaled-down physical model of the Rainbow Bridge was constructed to test for deflection, and it compared well the finite element models. A parametric study indicated that the design of the Rainbow Truss with flat curves and long members causes it to induce less bending moment and deflection.

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