Parametric Study on the Rolling Truss Typology

This contribution is presenting a parametric study on rolling trusses, inspired by Thomas Heatherwick’s Rolling Bridge in London. The purpose of this study is to analyse the principles of the rolling truss, to identify essential parameters, evaluate the load bearing behaviour and dynamic performance. Finally, the scope is to reveal the structural and kinematic principles of this structural typology and to convey them to further configurations.

The essential feature of the ‘rolling truss’ is delivered by the playful unfurling movement from a straight line to a curled-up polygon. The structural system corresponds to a kinematic chain mechanism: rigid segments composed of rigid frames, shaped by their polygonal curl with flexible articulations: triangulated kinetic deltoids actuated by hydraulic rams.

In the parametric study, the total girder length is assumed to be constant and the numbers of segments are varied to study the influence on geometry, static height, evolution of actuator forces and stresses during deployment. The study leads to following conclusions: The actuators are reduced to zero force members while the bridge is extended in horizontal position. Therefore the hydraulic jacks are solicited mainly to lift and curl the bridge. The maximum stresses occur right after the rolling truss starts to retract when it is cantilevering freely from one side. A rolling truss with higher numbers of segments is of advantage, despite the increasing number of actuators and complexity: Varying the number of segments from 3 to 8, the free span of the rolling truss is increasing relative to ist total length as well as the girder height.