Scissor Mechanisms for Transformable Structures with Curved Shape The "Jet d'Eau" Movable Footbridge in Geneva

In this paper we focus on transformable structures and more specifically on structures that can change from a flat shape to a curved shape in a continuous process. We present a method for building a mechanism from any kind of curve that can be flattened by modifying only one degree of freedom. Such mechanisms are based on scissor-pair mechanisms; recently, their technology has been improved to be able to match all sorts of curved shapes. We applied this method in a contemporary ongoing project at the "Jet d'Eau" in Geneva, a structural footbridge spanning 12 meters over a thin lake channel. This footbridge consists of 30 couples of stainless-steel scissors that can be either flat or raised and in the raised position looks like a wave with a sinusoidal geometry. This footbridge resolves a public mobility issue and combines wheelchair and gentle mobility with boat passing in the lake channel: When the footbridge is horizontal, the deck is flat and pedestrians can pass even if in a wheelchair while the boat traffic is closed; when the footbridge is raised, the deck becomes stairs so that pedestrians can pass on it and boats can navigate underneath.