Anirban Sengupta, Sr. Vice President - Technical Quality & Yogesh G. Waingankar, Associate Principal - Manager Design/CTO-STUP Consultants
Any bridge or infrastructure is designed for 100 years of design life. The structure remains an integral part of the surrounding areas and adds to the overall look and feel. Hence, importance should be given to the aesthetical parameters of the structure.
As a principle, the aesthetics of a structure should be achieved through structural forms, without hampering the structural efficiency, and without adding any non-structural elements.
A pedestrian bridge connects two different places; it connects and acts as a transition space for people from one environment/activity to another. It also forms an integral part of the street life.
A pedestrian bridge structure being structurally light, opens up opportunities for introducing various forms and experimentations in the structural form. Such bridges add to the cityscape and often become landmark/identity of the city.
Theme-based concepts of the structural forms are evolved through collaborative efforts of architects and engineers. Examples include the Atal Pedestrian Bridge over River Sabarmati, Ahmedabad; the Sambhaji Cable-stayed pedestrian bridge, Pune; and the Deccan FOB in Pune.
Atal Bridge, Ahmedabad
Ahmedabad is also known as the ‘city of flying colours’. Since 1989, the city has hosted the International Kite Festival as part of the official celebration of Uttarayan, during which, the skies over most of the cities of the state fill with colourful kites of various shapes, designs and sizes.
Elevation of Atal Bridge
Taking inspiration from the unique shape of a kite, the bridge’s overall triangulated structure with rhombus shaped cross section has been used as the structural form. The structure is made up of tubes, probably the first of its kind in India to be of such magnitude.
Salient features of the structure
Cross Section of Atal bridge
- Span arrangement 3x100m across River Sabarmati.
- Dual level bridge merging in the central span connects both the upper and lower promenades, making it more flexible and people-friendly.
- Steel truss with tubular members, the cross members are inspired by the shape of kites.
The Sambhaji FOB across River Mutha connects the Sambhaji Park Metro Station on the east side and the Vartak Garden on the west. The Balgandharva auditorium is near the bridge site.
Sambhaji Bridge has been conceptualized based on the ‘Tanpura’ - a classical instrument. The shape of the pylon represents the instrument. The pylon is inclined with a height of 75m from the base. The deck is cable supported RCC beams. Cables are connected at the top of the A-shaped pylon.
Elevation of Sambhaji Bridge “Tanpura Bridge”
- Span at deck level: 88m (5.8m+82.2m) + 40m
- Pylon height from base: 72.5m
- Pylon inclination: 200
- Deck: RCC Girders + Cross Girder + Deck slab
The Deccan FOB across River Mutha connects the Deccan Metro Station on the east side and the Riverside road on the west.
In Maratha history, warriors of King Shivaji were called ‘Mavlas’ and their headgear was known as Mavla Pagdi, which has a deep cultural value in Maharashtra. The design of the Deccan Bridge has been conceptualized based on the Mavla Pagdi wherein the cross section of the deck looks like a Pagdi (turban).
The main arches of the bridge are transversely inclined outwards and interconnected using cables for stability. The deck is suspended on the hangers from the arches.
Cross section of Deccan FOB
- Span at deck level: 13.5m + 73m +13.5m.
- Deck width: 9m minimum, varying with viewing gallery at pylon location.
- Deck: RCC cast in situ girders and deck slab.
- Height of arch above deck level: 18.5m.
- Cable type: Locked coil wire rope with UTS 1570 MPA as per IS 9282:2002 swaged in caste steel spelter sockets.
- Structural Steel: E350 BR as per IS 2062:2011.
All the three bridges are conceptualized and designed based on a theme that represents the local heritage and culture of the region, and which is very close to the sentiments of the public.
While conceptualizing, engineers and architect collaborate to ensure that the architectural concepts are realized in the structural forms, without hampering the structural efficiency. All the members used are structural forms and no ornamental members have been added.
Acknowledgement: Sabarmati River Front Development Corporation Limited (SRFDCL), Ahmedabad, and Maha Metro Pune.