The Garden Bridge was designed as a 366m long footbridge crossing the River Thames between Waterloo Bridge and Blackfriars Bridge. The bridge was designed to carry an expansive garden, featuring trees, shrubs and plants, together with many paved footpaths and pedestrian areas.
Structurally, the bridge was to consist of a series of radial and circumferential steel trusses originating at the two main river piers. These trusses were to be enclosed by an upper ‘soil’ deck and a lower copper and nickel soffit shell of complex geometry to give the bridge an elegant and unique appearance.
Rendel was appointed as a member of the Bouygues Travaux Publics/Cimolai JV as the lead checking engineer for Category III design check. The check covered the main bridge and foundations but also the works in association with moving the HQS Wellington (mooring dolphins and river wall works).
Rendel provided independent checking, centred on the production of a global 3D model of the bridge in LUSAS. This model captured the complex geometry and topology of the bridge with the truss members modelled as beam elements, and the soffit modelled with shell elements. The model also captured the construction sequence of the bridge, which aimed to achieve ‘zero’ bending movement at the river piers on completion by using a combination of ballast and prestress.