Cannon Street Railway Bridge

Year:1866

Duration:3 years

Cost:£193,000 (£22.6m today)

Country: London, UK

What did this project achieve?

Extend the South Eastern Railway to north of the River Thames and provide a City of London terminal

Cannon Street Railway Bridge sits between London Bridge and Southwark Bridge in London, connecting the City of London on the northern shore with south and south-east London by rail.

The iron bridge carries trains on the Southeastern line over the River Thames to Cannon Street Station.

An Act to enable the construction of the bridge, Cannon Street Station, and the connecting railway was obtained in 1861.

The works, under the direction of engineer Sir John Hawkshaw, began in 1863. Hawkshaw, ICE Past President (1862-3) and fellow civil engineer Sir John Wolfe-Barry designed the bridge for the South Eastern Railway Company.

The bridge opened to traffic in 1866, with five spans on cast-iron Doric columms filled with concrete and brickwork. A span is the distance between two supports for a bridge. A Doric column is a design from ancient Greece, where the column is wider at the bottom than at the top and has grooves along its shaft.

Between the abutments – the ends of the bridge – the bridge is 706ft long (215m).

The length of the two shore spans are about 126ft (38m) each, and the three middle spans 136ft (41m) each.

It’s supported by piers of cast-iron columns, 18 feet in diameter at the base and 12 feet in diameter above the bed of the river, filled with concrete and brickwork.

The superstructure of the bridge – the part of the bridge that directly supports the traffic – is made of plate girders. A plate girder is an iron beam built up from plates and shapes welded together.

Between 1886 and 1893, the bridge was widened by Francis Brady, engineer for South Eastern Railway, to a width of around 20m.

This allowed the bridge to have double the number of tracks, going from five to 10.

The bridge has undergone extensive renovations between 1979 and the early 1980s.

Cannon Street Bridge shortly after it opened.

Cannon Street Bridge shortly after it opened.

Difference the project has made

The construction of the bridge allowed the South Eastern Railway Company to extend its train route, which ran into London Bridge Station, to the City of London on the northern shore of the River Thames.

How the work was done

The original Cannon Street Railway Bridge had four piers, each made of four cast iron cylinders sunk into the riverbed.

This increased to six pillars for each pier when the bridge was widened in 1886-93.

Each cylinder was filled with cement concrete, a method also used with Charing Cross Bridge, up to the riverbed. Above this, the cylinders were filled with brickwork in cement.

After they were filled with concrete, cast-iron girders were placed on top of the cylinders. A girder is a large iron (or steel) beam used for building bridges.

Works to make the bridge stronger were carried out in 1910-13, so that it could bear the weight of increasingly heavy trains. This involved building new girders at the piers and in between the existing girders of the bridge.

Further strengthening work was carried out in 1983. This included filling gaps between the inner surface of the iron cylinders and the brick lining with pressure grouting. This technique involves injecting a grout material into voids in hard-to-access spaces.

Reinforced concrete collars were also added at the top of the cylinders to make the bridge stronger.

Fascinating facts

The piers of the bridge contain about 2,500 tons of cast iron and the superstructure weighs 4,200 tons.

The same engineer, Sir John Hawkshaw, designed Cannon Street Bridge and Charing Cross Bridge. The latter was designed a year earlier.

Cannon Street Station was closed on Sundays for nearly 100 years after off-peak services into it were discontinued in the early 20th century. It re-opened on Sundays as part of the Thameslink Programme development in the 2010s.

The bridge was originally called Alexandra Bridge, after the wife of King Edward VII, Alexandra of Denmark.

People who made it happen

  • Client: South Eastern Railway Company
  • Engineers: Sir John Hawkshaw, Sir John Wolfe-Barry and Francis Brady.

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