Blog 3
Twickenham Bridge

Twickenham Bridge

Structure Information

Figure 1. Twickenham Bridge

The Twickenham Bridge was designed by Alfred Dryland, head engineer, and Maxwell Ayrton, architect, in 1931. Aubrey Watson Ltd built the bridge for £217,300 to connect the Old Deer Park in Richmond with the district of St. Margaret’s on the north bank. A crossing at the Thames River at this location was brought to discussion as early as 1909 (22 years earlier) but the bridge was known locally as ‘The Bridge that Nobody Wants’ [1]. With a title like that, I would also wait 22 years before acting… There were disagreements about the exact route and the financing of the bridge, but finally in 1926, the Ministry of Transport agreed to go ahead and finance the bridge. The Twickenham Bridge was part of a three-bridge road scheme, known as the Great Chertsey arterial road scheme, in order to relieve Hammersmith Bridge and alleviate congestion in Richmond [2].

Alfred Dryland was considered “the greatest expert in Britain of his day” and “a pioneer in the planning and construction of motorways.” The architectural ornamentation of the bridge was done by Maxwell Aryton. He apparently was a very famous architect and was an advocate for concrete stating concrete is “a material worthy of architectural recognition” [1]. Basically, the Twickenham Bridge had some successful people working on it.

Historical Significance

Twickenham Bridge was an innovative structural engineering design because it was the first large-hinged concrete arch bridge to be built in the UK. It is hinged at the crown and at the springing points of the arch, thus the arches overcame many of the defects are inherent in fixed arch bridges, particularly the difficulty in calculating abutment reactions. This is just good news for me because it makes my analysis easier.  Although the three-hinged arch was developed by many engineers in the mid-19th century for arched metal roofs and bridges, the concept was only applied to reinforced concrete structures in the early 20th century [1].

Cultural Significance

As I was researching the history of this bridge, I came across a ‘Transport for London’ journal that was written in 2008 and stated “Twickenham Bridge remains as important today, as it was seventy-five years ago.” The article was celebrating the bridges 75th anniversary and described how it greatly improved London’s traffic flow [2]. I can’t think of too many things that remain good with age (other than wine and cheese) so the fact that the bridge that was designed for traffic in the early 1900s is still relevant now is impressive.

Once the bridge design was finalized, there were mixed reactions towards the bridge. About 200 men were hired to construct the bridge which was a big deal because it was during a time of high unemployment. However, in order to construct the new traffic route, over 300 families had to relocate as houses and shops that were in the way were demolished. Also, the initial designed featured four 70-foot towers at the river banks and retaining walls that were 20 feet above the road level. The Daily Telegraph organized a local petition against the design claiming this was “inappropriate to the setting in Richmond.” Luckily, the engineers and architects were very responsive and changed the design. About 56,000 vehicles cross the bridge every day, which is significant. While the bridge was originally built to relieve traffic, it remains just as important today [2]. Fun fact: the bridge was declared a Grade II listed structure in 2008, providing protection to preserve its special character from unsympathetic development [3].

The Twickenham Bridge is supposed to represent a unity between architecture and structural engineering, but honestly after taking Historical Structures, I don’t know if I can look at an architect the same way ever again. The Art Deco theme is continued in the use of ornamental tiles that are embedded in horizontal seams and in the bronze cover plates over the expansion joints at the abutments [1].

Structural Art

Figure 2. Stairs leading up to the deck.

Scientifically, the arch does show the loads. All the loads are brought from the top deck to through the arch to the columns and to the footings. Socially, for the towns of Richmond and St. Margaret’s and the surrounding areas, this bridge was a big deal. It allowed for the towns to easily be connected and helped relieve the traffic congestion around the surrounding areas. Symbolically, this bridge is the first three hinged arch concrete large bridge in the UK. The architect wanted to make sure it was known to be a big technical feat and portrayed that through the design. From these statements alone, it would seem as though the bridge qualifies as structural art. However, this structure is heavily ornamented by an architect. Even though the architect’s main purpose was to accentuate the structure and loads, I think the ornamentation goes against what Billington defines as structural art; the structure should speak for itself without the need for additional design. Because of this, I would say this bridge is not structural art.

Structural Analysis

The Twickenham Bridge is a 145.5m long and 21.3m wide bridge that has 5 arches. The central span is 31.4m while the two arches next to that are 29.9m. The two arches on land each measure 17.1m. The bridge is made of reinforced concrete arches on top of very narrow piers. When looking closely at the bridge, you will notice some striations. This is purely architectural and textured by a bush hammer. One of the most distinctive features of this bridge are the decorative bronze cover plates. These are an Art Deco style (just like the Bank of America Plaza, my first blog post!) and help accentuate the three structural hinges at the crowns and springings of each arch. The architect, Maxwell Aryton, wanted to make sure the hinges stood out and “gave prominence to the bridge’s technical virtuosity” because it was the first large three-hinged concrete arch bridge to be built in the United Kingdom [1].

As mentioned in the cultural significance section, the construction of this bridge was a big deal. Many people who were unskilled were hired so the construction had to be simple. Although the form was a newer one for the UK, constructing bridges had been done before and this one was no different. Many parts were assembled at factories and then taken to the construction site. The footings were sunk into the water and the construction proceeded from there. Because the bridge was over water, many of the parts were floated to the site by boat.

The loads on the bridge travel from the deck to the arches and down to each of the springings/ footings. The arches are all in compression due to the reactions from the footings acting upwards.

In order to calculate all the reactions in the bridge, I idealized the bridge as a typical three-hinge arch bridge and only focused on the central span. I chose a live load of 952.4 kg/m as that is the average live load for a vehicular arch bridge of this size.

Consider the equilibrium of the entire structure:

∑Fy = 0

(952.4 kg/m)(31.4m) + RAV + RBV = 0

From symmetry: RAV = RBV

RAV = RBV = 14952.68 kg

Break into parts and only consider left side:

P1 = ()(952.4kg/m)= 14952.68 kg

∑MC= 0

(RAV) () – (P1)() – RAH (HMAX) = 0

(14952.68 kg) () – (14952.68 kg)() – RAH (6.1m) = 0

RAH = 19242.38 kg

∑FX = 0

RAH = RBH  = 19242.38 kg

Explaining this design to the stakeholders was important as it took about 17 years for the bridge to actually start construction from which the idea was brought up for the bridge. What finally persuaded the stakeholders to commit to the design was the *surprise surprise* finances and path of the new roadway. The design drawings were most likely used to explain how efficient the three-hinge arch design is and how an efficient design can save money because of less material and less need for restoration.

Personal Response

To be honest, one of the reasons I chose to analyze this bridge because it was located far from our hostel, so I knew that no one else would choose it. But once I actually looked into the history of the bridge, I didn’t realize how important it was to the surrounding communities and the city of London. This bridge has been alleviating traffic for over 75 years and was the first large concrete three hinged bridge in the UK. That’s actually pretty impressive! I guess I chose well.