Design and pre-construction of concourse structures

The aim

The old London Bridge station had a train shed housing nine terminating platforms and six through platforms. The project’s aim was to reverse this to be six terminating and nine through platforms which would remove the bottleneck for train services.

The station footprint is sandwiched between Tooley Street and St Thomas Street and so there was no space available to add new platforms. The only solution was to untangle the crossing points, reduce the dead-end lines and hugely increase the throughput of trains.

A challenging programme

Work was carried out on the south terminating platforms, gradually moving two at a time towards the north. The first six platforms were re-covered with new steel canopies that ran the entire length of the platforms.

Working at a rate of approximately four platforms per year, each stage of the programme schedule was met on time allowed trains and passenger to start using the platforms again.

Fully integrated joint venture design team

The 50:50 Arcadis:WSP + Grimshaw Architects JV team took on a unique project identity so that all staff were taken outside their usual office traffic. This helped the team gain a vision of what they were aiming to achieve as a team which is illustrated in the visual flythrough animation.

The project team and the Network Rail team were co-located in Costain’s project office which meant everyone had access to each other. This made it easy for engineers to find out the client’s wishes and for the client to find out how the engineers would build things.

The team received minimal Document Review Notice (DRN) comments and there were good programme gains when the two criteria above were understood.

As is often the case, it was found that the original scheme plan was not buildable within the programme constraints. Programme deadlines were governed by major blockades of the station and so to achieve them, the following methods were introduced:

  • Modular components would be used for the façade, platforms and canopies.
  • Off-site fabrication would be necessary for the platforms and canopies / pile caps.
  • Rebar detailing and modelling by the suppliers, based on design intents, would be produced as offsite prototypes.

Rebar prototypes

A site in Edmonton, north London was used to assemble mock ups of the columns. A steel ‘dolly’ was used to hold the rebar in place. The smaller photos show the prototypes and the larger photo shows the first column that was built on site.

(See PDF below)

Bridge decks and platform structures

Work began on the bridge decks in October 2012 with 29 no. to be designed in detail. Form 3 was required by March 2013 at which point the final designs were required for 11 bridge decks for stage 1 and 1A. The programme critical date to begin construction was within two months of that on 24 May 2013.

The 29 decks were split into similar family types of size, span and skew angle as shown in this diagram.

(See PDF below)

The bridges totalled 3,700 tonnes of steel plate girders of which cost certainty was required for the tender. The final tender sum for the bridge deck steelwork was £6m.

A full steelwork design was developed for Family Group 1, pro-rated for the 29 decks of different lengths and skews. The first bridge girders were lifted into place on 8 October 2013.

The steelwork was optimised for maintenance free activity with weathering steel used on the exposed bottom flanges. Careful coordination was needed with the canopy columns installation and the beams were installed in braced pairs for stability during construction and during the acoustic fill placement.

Platform construction

This sketch, was drawn up in October 2012 at an engineering meeting between the architects, P&C team and the concourse team. By October 2013, the construction methodology had become this.

(See PDF below)

All deck steelwork on platforms 14 and 15 installed in October 2013. The acoustic infill is being laid.
The platforms (previously known as bridge deck H) were opened to traffic 311 days after construction started.

Cross section showing the platform design.

(See PDF below)

Concourse Structures

Coordination was required with all disciplines to fix the deck envelope designs. The structures had to include facades, platforms and canopies, MEP systems, station systems (existing and future requirements), public health and drainage, railway systems and geotechnical systems. This colour coded diagram (below) shows some of the complexities.Other coordination considerations included:

  • Bearing access and maintenance – RAMS
  • Timber ceilings – (for which the designer was not on board until late 2014).
  • The coordination of M&E and drainage services running both along the tracks and transversely across the station.
  • Material serviceability on platform and canopy designs that could accommodate any mid-span deflections of up to 40mm.