ABSTRACT
The origins of the suspension bridge go back a long way in history. The modern suspension bridge originated in the 18th century when the development of the bridge structure and the production of iron started on a full-scale basis. Bridges are classified into single-span, two-span, or three-span suspension bridges with two towers, and multispan suspension bridges which have three or more towers. Flexible towers are commonly used in long-span suspension bridges, rigid towers for multispan suspension bridges to provide enough stiffness to the bridge, and locking towers occasionally for relatively short-span suspension bridges. In some short-span suspension bridges, the girders do not have enough stiffness themselves and are usually stiffened by storm ropes. Vibration analysis is needed to determine the natural frequency and vibrational modes of the entire suspension bridge as part of the design of wind and seismic resistance.
