PEDESTRIAN BRIDGES

The creative design facet of constructions plays a pivotal role in their rise to fame. In the first of this four-part series, we explore the architectural aspects of renowned engineering feats in relation with the structural elements. We look at pedestrian bridges which showcase incredible design elements

Words: Revati Rajwade

1.Zubizuri bridge - Spain_1

There are some constructions which possess the extraordinary quality of generating admiration as soon as a person sets eyes upon them. More often than not, man has shown affinity towards magnanimity and hence, this is the foremost criteria, which tends to create awe and inspiration.

Dams, lighthouses, tunnels, bridges and various other such constructions which span across huge dimensions have taken the world by surprise since their inception. The engineering of such structures is a daunting task and is rightfully given its credit by attributing these to technical feats.

However, the architectural aspect of these constructions is sidelined and seldom rises to the forefront

Engineering involves the working, construction, durability and several such other aspects of a proposal. However, as German architect Walter Gropius (1883-1969) had famously said: “Architecture begins where engineering ends.”

It is indeed the skillful amalgamation of architecture and engineering which results in some of the best constructions which adorn the world. The two, when implemented in tandem can unravel the hidden possibilities of the ‘to be built’ environment.

An excellent example of this would be the structures of Santiago Calatrava – a structural engineer and an architect. The very fact that Calatrava is an engineer as well as an architect enables him to transform his concept driven dynamic forms into reality with finesse.

ZUBIZURI BRIDGE, SPAIN

The design for his Zubizuri bridge in Bilbao, Spain is a striking form coupled with neat engineering. The design began in 1990 but execution started 4 years later. Like all of Calatrava’s structures which receive inspiration from nature or the human body, this bridge too has a connection with nature as the basic composition of steel and glass represents a skeletal frame.

Since the bridge spans across a river, the chosen symbolism of a fish was well-received by the public. The walkway of the bridge represents the backbone of a fish with its narrow stainless steel ribs supporting translucent glass panels. The thought process and concept behind the project is thus instrumental in placing it in the right context.

The curved walkway design is supported with suspension cables from an inclined arc which majestically rises to 15.3 m above the pedestrian movement. This rise was made possible owing to the use of 50 mm diameter tubes for the arc.

Steps and ramps lead people to the bridge from both the sides. The walkway is raised 8.5 m above the water and its width varies between 6.5 and 7.5m. The 75m span of the bridge is flanked by 39 steel cables on each side at an interval of 1.8m. The dominating structural element – the bow – is inclined at an angle of 80° to the horizontal.

In plan, this arc rhythmically travels from the lower left corner to the upper right corner.

FACT FILE: ZUBIZURI BRIDGE

Structural Engineer and Architect: Santiago Calatrava
Location: Bilbao, Basque Country, Spain
Year of design: 1990
Years of construction: 1994 – 1997
Height: 15 m
Width of walkway : 6.5 m – 7.5 m
Span of the bridge: 75 m

The steel cables and the glass pathway result in a sharp contrast of materials. The various materials have been provided a finish and colour such that they appear holistic.The main structural steel arch has been painted white like the rest of the structure.

2. The majestic arch of Zubizuri Bridge

However, in the modern setting, design does not end at these aspects. The lighting element is an important factor which highlights the outline and proves to be a landmark in the city.

Thus, in each of the lower ribs of the bridge one lighting device has been placed after due consultation with a lighting expert. The illuminated composition is indeed a spectacle.

An apt description of the bridge by author Philip Jodidio states: “As in many other designs by Santiago Calatrava, an apparent disequilibrium or rather a sense of frozen movement is heightened by the lightness of the structure.”

TABIAT BRIDGE, IRAN

A stark contrast to the simplistic Zubizuri bridge is the Tabiat bridge in Tehran designed by Iranian architect Leila Araghian which is famous for its complexity. The structural engineer Maffeis has brought the multi layered design to its logical conclusion.

It is located in the northern area of Tehran known as Abbas Abad, which houses several libraries and museums. This is an example of a design where the concept journey’s its way through the entire arduous design process to reach the final destination, unscathed.

3. Tabait Bridge- Tehran

“From the very beginning the concept was to have a spatial structure large enough to create an architectural space, while at the same time acting as the structure,” explained Araghian, who was just 26 years old when she designed the bridge. “It is intended to be a place to linger rather than just one to pass through and to act as an extension of the parks which lie on either side of the bridge.”

Usually the virgin idea is compromised owing to several factors like functionality, cost and structural requirements but such is not the case here. The bridge is an assortment of different pathways which encourages pedestrians to meander on it, thus creating interest and offering a new dimension to the mundane activity of crossing a busy road.

The aim is to encourage people to stay and ponder and not merely pass. The bridge lies across the Modares Expressway and the design was conceived by the architect for a competition. On winning it, Araghian’s studio Diba Tensile Architecture completed the 270-metre-long bridge in 5 years.

Since its completion in 2014, it has been the largest pedestrian bridge in Iran.

The structure comprises three levels that follow a curved path and which are connected by various ramps and stairs. The bridge has a mammoth steel truss structure that marks the bridge a place in the skyline.

4.Levels of walkways of Tabait Bridge

Columns have multi-branches as they have been inspired from the dense foliage in the parks alongside. The bridge is a result of a total of 2,000 tonnes of steel and 10,000 cubic metres of concrete. The width of the pathway varies from 6 to 13 meters where spaces with greater width have seating spaces for people to enjoy the space.

The several levels of the bridge have wooden finished walkways which meander as an S shape to create a sense of mystery about the destination. “There are multiple routes from one point to the other, encouraging pedestrians to wander and get lost on this bridge,” added Araghian.

The construction was a huge challenge since the bridge lies across a busy highway. Platforms and temporary tunnels had to be built to ensure that the road below was not affected in any way. This is thus truly a feat of engineering as well as architecture.

FACT FILE: TABIAT BRIDGE

Architect: Leila Araghian
Structural engineer: Maffeis Engineering
Location: Tehran, Iran
Years of construction: 2010-2014
Width of walkway: 6 m – 13 m
Span of the bridge: 750 m

NEXT ISSUE :
THE MAGNIFICENCE OF DAMS


Revati is an Architect and Interior Designer by profession and a writer by passion. She can be reached
at: revati@urbanvaastu.com