Design Trend of Tower Shapes toward Long-Span Suspension Bridges

Towers of long-span bridges play a key role as iconic symbols. The role of tower becomes more significant for longer span bridge structures. As the aesthetics has been appeared as one of dominant in decision process for tender design, innovative and unique tower shapes have been brought to birth in the world. However feasible tower shapes for long-span bridges are somewhat limited to a few specific structural systems. Such limitation might be inevitable when the structural safety at lower cost is imposed as strong constraints. Therefore, the development of a better looking tower shape satisfying the imposed constraints is a key issue to be addressed for super-long span bridge design to create an attractive landscape including the bridge. Considering that understanding design trends is very important step to establish design guide lines for future design, existing tower shapes have been investigated considering structural material, structural system, and architectural styles. This paper will focus mainly on the two issues: (1) the identification of the important factors affecting tower shapes by investigating the tower shapes of existing suspension bridges and (2) the proposal of tower shapes for the prototype suspension bridge whose main span is 2800m.