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First reveal on £1bn London Bridge works

London Bridge concourse 3x2

Two-thirds of London Bridge station’s new concourse opened to the public last month, unveiling just one part of a station’s estimated £1bn redevelopment.

The ambitious programme will upgrade the 179-year-old station in nine stages, creating a new concourse and changing six through and nine terminus platforms to nine through and six terminus platforms without causing serious passenger disruption.

Little wonder the project has been described by architect Grimshaw principal Andrew Byrne as trying to perform “open heart surgery while jogging”.

London Bridge upgrade the original condition

London Bridge upgrade the original condition

The original through and terminating tracks before work started in 2012.

London Bridge upgrade what happens now

London Bridge upgrade what happens now

The next stage of the development involves constructing the remaining third of the concourse and the final through platforms.

London Bridge upgrade final stage

London Bridge upgrade final stage

The finished concourse and tracks when the project is complete (2018).

Around 125,000m3 of material was removed to make way for the 175m x 75m concourse, which features granite floors and is constructed using pre-cast concrete and stainless steel cladding.

The concourse features 14 concrete columns made with self compacting concrete of which seven have yet to be unveiled. The largest columns incorporate 82m3 of concrete and weigh 207.5t.

The columns vary in size from 3.8m by 2.2m at the base and 3.6m to the underside of the cross heads – supporting the terminating platforms – to 4.1m by 2.5m at the base and 5.1m to the underside of the cross heads, which support the through platforms.

The new concourse is much larger than the existing 55m by 40m terminating concourse and will eventually be as large as the pitch at Wembley stadium, holding 80 retail units when complete in 2018.

Given the size of the concourse, it is unsurprising that passenger flow was at the heart of the design.

London Bridge upgrade platform 8

London Bridge upgrade platform 8

The upgrade, as seen from platform 8

“The actual passenger movement effectively drove the design,” explains the WSP Parsons Brinckerhoff/Arcadis joint venture’s design director Adrian Tooth.

“We want a station that people can actually move through freely.”

The station currently serves 120,000 people during the two two-hour peak periods (mornings and evenings). This is expected to rise to 160,000 over the design life of the station as the population rises, meaning an increase from 56M passengers annually to 70M.

With these numbers in mind, the team had to consider how best to manage the flow of people through the station at peak times, using a software programme called Legion to model passenger movements during the design phase.

Everything we’ve done through the design and through construction is to generate certainty

Adrian Tooth, WSP Parsons Brinckerhoff and Arcadis joint venture

Considering passenger flow was a fundamental issue, it might seem strange that the concourse was opened when it could only handle two-thirds of its capacity.

It was crucial, however, as the new through tracks – platforms seven, eight and nine (which measure 250m by 12m at the widest point) – are only serviced from concourse level.

Platforms and tracks

To minimise the amount of time spent on site, the team adopted a modular precast concrete design to create the through platforms. The largest module measured 3.1m x 3.1m.

The steel and aluminium canopy above the platforms is also modular. A 53m section of this was tested off site, allowing the contractor to experiment with the most effective construction method.

“Everything we’ve done through the design and through construction is to generate certainty,” says Tooth.

London Bridge upgrade concourse 1

London Bridge upgrade concourse

The London Bridge concourse

“We’ve used a 3D building information model to make sure that services are co-ordinated with the structure and the architecture, so we take out risk from construction on site.

“The modularisation has been undertaken to try and make sure that we generate things very quickly that can actually be built quickly on site.”

As a result of this approach a modular brick façade took a number of weeks instead of months to erect.

Arches

London Bridge is the capital’s oldest rail terminus, so it is unsurprising that the team had significant heritage challenges to consider.

Parts of the station sit on Victorian brick arches, most of which were used to house shops or businesses before construction began.

[The arches are] visible to the public – probably more visible now than they were a few years back

Adrian Tooth, WSP Parsons Brinckerhoff/Arcadis joint venture

But the new concourse required space – for the escalators running down from track level, for the safe movement of people and for platform connectivity. Inevitably, some of the arches had to be removed.

“You need to generate some space so if it’s in a rabbit warren of arches, it’s very difficult for people to navigate around,” explains Tooth.

“Wherever we’ve been able to keep arches we’ve done that, celebrating that they’re there by cleaning them, making them into retail spaces.

“They’re visible to the public – probably more visible now than they were a few years back.”

The team was required to lodge reports with the Museum of London Archaeology (Mola) regarding the arches and the original train shed roof, which has found a new home with a rail heritage society in Wales.

Rebuilding the quadripartite arches

Not all of the arches were removed to make way for the concourse.

London Bridge upgrade concourse escalators

London Bridge upgrade concourse escalators

The concourse elevators.

On the Western Arcade route only some of the original quadripartite arches were retained because they are covered by walkways located above.

However, as a result of needing to increase the width of the northern part of the station for three extra lines, tracks were shifted to run over the arches.

The resulting load was deemed too great and a some of the original brick quadripartite arches was replaced.

The new composite board-finished concrete arches are each made of approximately 16.5m3 concrete and 28m3 of polystyrene void former.

Despite being constructed using more modern materials, they retain the shape of the original quadripartite arches.

Collaboration

The scale of the project means that challenges are bound to arise. But Tooth insisted that the collaborative approach of the joint venture created a positive atmosphere – in fact, WSP Parsons Brinckerhoff received BS11000 accreditation using this project as evidence of its collaboration.

I think it’s probably gone to the next level, to a point. It’s gone away from a ‘them and us’ scenario to a project-related scenario.

Adrian ToothAdrian Tooth, WSP Parsons Brinckerhoff/Arcadis joint venture

“It’s very easy to say ‘well it’s a joint venture so this company takes this bit of the design and this company takes that bit of the design and off you go’. We consciously made a decision that we weren’t going to do that,” says Tooth.

“What we said is we’re going to have an integrated team which meant that we had a group of people from both companies working within a particular area and actually we split the project up into areas, so we had a platforms and canopies team, we had a concourse team, for instance.”

“I think it’s probably gone to the next level, to a point. It’s gone away from a ‘them and us’ scenario to a project-related scenario.”

The station upgrade, which is part of the £7bn Thameslink Programme to improve north to south rail travel and through parts of London, is expected to finish in 2018.

London Bridge upgrade concourse from above

London Bridge upgrade concourse from above

The London Bridge concourse from above

Project details

Platforms and canopies

  • Size of platform canopy sections (largest) = 3.1m(w) x 9.8m(l) x 0.5m(d) (example taken from platform 10 wedge void)
  • Size of platform pre-cast modules (largest) = 3.1m(l) x 3.1m(w)
  • Length of all platforms (along centreline) = through platforms 1-9 are approximately 250m and terminus platforms 10-15 are approximately 275m

Concourse columns

  • Tallest column, bridge deck C = 7.3m
  • Smallest column, bridge deck H = 4.7m
  • Maximum crosshead span, bridge deck A,B,C,D = 10.5m
  • Minimum crosshead span, bridge deck H = 10.1m
  • Average m3 of concrete per column (largest) = 82m3 (207.5t)
  • Average steel tonnage for rebar cages (largest) = 26.6t

Space carved out

  • Approximate m3 of material carved out to make the new concourse space = 125,000m3
  • Approximate m3 of additional material carved out to make the new western arcade = 1,178m3

Concourse areas

  • Approximate floor area of terminating concourse = 2,500m2 (unpaid part)
  • Approximate floor area of main concourse (as it is now) = 5,500m2
  • Approximate floor area of main concourse (in 2018) = 10,500m2

Additional details

  • Approximate total number of prefabricated canopy sections on the whole project = 1,560
  • Approximate linear metres of western red cedar (timber soffit cladding) = 76,750m (the length of almost two full marathons)
  • Approximate m3 of concrete per Western Arcade quadripartite arch = 16.5m3
  • Approximate m3 of polystyrene void former quadripartite arch = 28m3
  • Length and area of Western Arcade (in 2018) = length will be 134m and area will be 2,107m2

 

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