Statics: Equilibrium

A footbridge

Fig. 1-8: A foot bridge can be lifted by a single person

The form of footbridge shown in Fig 1-8 is a development of the simple counter balanced barrier shown in Fig. 1-7.

The moment induced by the weight of the footbridge deck about the supporting points on the wooden frame is slightly larger than that induced by the balance weight, which is placed on and behind a wooden board. The addition of a small force, applied by pulling on a cable, causes the bridge to open.