A one-of-a-kind footbridge connected to nine diagrid pylons that open into lotus flower petals, requiring advanced geometric analysis and optimisation tools for this magnificent design.
Spread over 220 acres of verdant greenery in Delhi, Bharat Vandana Park is being developed as a major tourist destination. Shaped as a lotus flower, it will be a one-of-a-kind park with an eco-forest zone, several lakes, cultural attractions and adventure sports facilities. Eckersley O’Callaghan has been tasked by the local project engineers Anup Structural Consultants, with the structural design of two signature elements in this project – the spectacular 1.2km footbridge and nine diagrids forming 45m tall pylons.
The cable-stayed footbridge will be suspended in the air anchored to the top of the pylon concrete cores. The challenging design of the footbridge sees a series of cables eccentrically supporting the 150 m span deck, with the cables switching side after midspan requiring a supporting strategy for the deck which needs to be torsionally stiff.
Our structural engineers presented a creative solution to cope with the double task of allowing the thermal movement in such a long footbridge and at the same time reaching an adequate level of lateral stiffness to preserve the cable tension – a system of two Shock Transmission Units (STU) coupled with two elastomeric sliding bearings is introduced at the deck midspan to allow the flexibility of expansion under slow loads and stiff locking under fast loads. Thus allowing the whole bridge to work as a unique structure, considerably reducing the expected movements and stresses in the deck, and minimising the axial load variation in the cables.
Wrapped around each of the nine bridge concrete pylons are steel diagrids which rise to form a lotus flower at the crown of each pylon. We developed a variation of three diagrid designs, all allow the bridge cable-stays to reach the top crown of core by passing through dedicated steel tubes which act like “sleeves”. Our structural engineers improved the buildability of the tender stage design for the diagrids by using advanced geometry analysis tools to achieve consistency in angles at tube intersections while retaining the architectural intent and vision.