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December 10, 2019

As one famous Scottish bridge faces serious structural challenges in the months ahead, we learn of plans for 13 more bridges to be constructed in London.  Every bridge is unique. But the same questions must be asked: You need to know what the bridge is crossing: a river, a motorway or a deep valley? What will be the span? How will it be built?  Will it carry heavy trains or pedestrians?  Where is the bridge located – an urban environment or a national park? How will it affect the lives of the people using it and living near it? (IstructE)

Design and build may have developed over the years, but the symbolism and purposes of bridges remain very much the same; unlocking areas for development, improving economic growth and in some cases bridging links between cities and cultures. We take a look some of the world’s oldest, most interesting and dangerous bridges, some of which have survived centuries, world wars and extreme weather conditions.

1. THE ØRESUND BRIDGE – WHERE BRIDGE MEETS TUNNEL

The Øresund Bridge is the longest combined road and rail bridge in Europe. This cable-stayed bridge links Copenhagen in Denmark to Malmo in Sweden and runs for 8km before submerging under the Flinte Strait and turning into a 4km tunnel. The point at which bridge meets tunnel is at a man made island called Peberholm which was created from material dredged from the seabed.

The concept of the bridge dates as far back as 1930s (although some claim that it was earlier) but plans were dropped during World War 2. Construction didn’t actually begin until 1990s and the completion of the structure was eventually symbolised in 1999 with the meeting of the Prince of Denmark and the Princess of Sweden midway.

Reasons for the cable-stayed design are because the spinning of the main cable on a suspension bridge is expensive and tricky where as cable-stayed bridges carry a much more direct load path through the cables to the pylons, stiffening the bridge further. This extra stiffness is especially useful as the bridge is carrying rail traffic, which requires less deflection than would be acceptable for a road bridge only (University of Bath).

It may not be the most aesthetically pleasing of structures, but the practicality of this bridge has not only joined two cities and connected mainland Europe to Sweden, it has encouraged cultural, economic and educational links in the region and received an IABSE Outstanding Structure Award.

2. MILLAU VIADUCT – ARCHITECTURAL BEAUTY MEETS STRUCTURAL EXCELLENCE

This Anglo-Saxon collaboration was the creation of French structural engineer Michel Virlogeux and British architect Norman Foster. Not only the design a favourite of our MD Geoff’s but it’s ranked as one of the greatest structural achievements in the world.

The bridge, which received the 2006 International Association for Bridge and Structural Engineering Outstanding Structure Award was privately financed and cost a cool £272 million and sits in the clouds at 343m high.

3. THE GOLDEN GATE BRIDGE – THE MOST PHOTOGRAPHED BRIDGE IN THE WORLD

The Golden Gate Bridge is certainly one of the most famous bridges in the world.

When it first opened, it was walked by 200,000 pedestrians, local to San Francisco, now, it’s walked by 10 million tourists every year, and, since it opened in 1937, it’s been crossed by over 2 billion vehicles.

4. PONTE VECCHIO, ITALY – THE HOME OF RENAISSANCE ARCHITECTURE

The Ponte Vecchio is Europe’s oldest segmental arch bridge and one of the most iconic landmarks of Florence, a city known for its Renaissance architecture, art and culture. It was also best known as the centre of trade and finance in the Medieval ages and is still ranked as one of the most beautiful cities in the world. Its purpose was to connect the  Uffizi to the Palazzo Pitti so that the Medici could connect to the people they were ruling on the other side.

The stone bridge crosses the Arno at its narrowest point and is comprised of 3 segmental arches.  Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side (Wikipedia). The bridge withstood huge pressures when the Arno burst its banks in 1966.

Most notably the bridge is occupied by merchants whose shops line the outsides of the bridge (this was apparently for tax exemption during the medieval era). Perhaps because of its beauty, the Ponte Vecchio was the only bridge in Florence that remained intact during World War 2.

5. KHAJU BRIDGE IRAN – PERSIAN ARCHITECTURE AT ITS FINEST

brown concrete building during night time

The oldest bridge in Iran, the Khaju Bridge, is said to be one of the finest examples of Persian architecture.

At 132m long and 20m wide it has 23-arches, 26 smaller and 21 larger inlets all made of stone. It is a semicircular structure with abutments on each end (part of a structure that bears the weight or pressure of an arch). The arches shift the weight from the bridge deck to the support structure. The force of compression is pushed outward along the curve of the arch toward the abutments. (Historical Iran).

It has been referred to as one of the world’s best multi functional bridges as it doubles up as a dam, controlling water-flow thanks to sluice gates that, when closed, raise water levels to help facilitate the irrigation to surrounding areas.

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