Project: Stepney Green Walkway 1/201 Installation of Elevated Slab & Works to Staircase 1/604
Client: TfL SWIP ASPIRE
Works Value: £350,000
D&D Rail were instructed to undertake works to construct a new walkway slab 1/201 within Stepney Green station. The existing slab currently forms the ceiling of various equipment rooms within the station. Our works were to construct a new slab above the existing, which was left in-situ. As part of this construction, works were also undertaken to extend Staircase 1/604 by 2no. risers and a new handrail, tactiles, nosings and other premises modifications were also made to Staircase 1/604.
Steel beams were fixed to the side walls of the walkway to support the new slab. Works commenced during engineering hours prior to a planned weekend station closure. During these shifts we formed pockets in the walkway walls and cast pad stones for the steel beams around staircase 1/602.
Station Closure Works
During the weekend station closure we drilled holes and chem fixed wall plates for the support of the steel beams, in the side walls of the walkway. Following pull tests on the studs fixing the wall plates in place we commenced the installation of the steel beams for the new walkway. These beams were then bolted to the wall plates to form a grillage.
Comflor sheets were laid between the steel beams forming a permanent steel deck to retain the concrete once poured. This deck was suspended in place above the existing walkway leaving a void below. The steel deck extended onto the Overbridge 1/636 where is sloped down to meet the existing floor level some 5 metres along its length, to reduce the slope in this area. There was also a requirement to form 2no. new steps at the top of staircase 1/604 to mitigate to increased height of the surface of the walkway. The floor tiles were removed locally and we made up plywood/ timber shutters to form these new steps. Once the steel deck was completed and inspected by LUL we commenced the concrete pour.
Parex concrete was mixed on site and poured directly onto the Comflor in the gaps between the steel beams. The Parex was poured to a height level with the top of the steel beams and also poured to form a ramp/ slope on the overbridge to ensure a smooth transition from the height of the new walkway. Finally, we cast the 2no. new steps at the top of staircase 1/604 to allow passengers to access the walkway from this staircase.
Due to the fast early strength gain when using Parex, we were able to build a temporary walkway on top of the new deck the following morning. The temporary walkway was made up of Dricon Plywood pre-coated with an approved paint & non-slip grit supported by Dricon timbers. As part of this temporary work a ramp was constructed from the walkway to the overbridge. The Temporary walkway was then fixed to the new (parex) concrete deck in preparation for the start of Traffic Hours at the end of the Closure.
The existing stair nosings were removed from Staircase 1/604 and all fixings and dust was removed from the timber treads. Dricon plywood was fixed to the treads to bring the height of each step into tolerance and new AATI nosings were screwed in place. Dricon plywood was also fixed to the risers as a temporary measure to ensure passenger safety on the resumption of foot traffic. A phenolic tread plate was laid on the tread between the AATI and the riser and fixed in place with adhesive and screws, to form a non-slip step. Finally, we cut the handrails on staircases 1/602 & 1/604 and installed temporary sections to reflect the change in the height of the walkway at each location.
Following the weekend closure we returned to the station to complete the works. Foam concrete was pumped into the station to fill the void between the new deck and the existing walkway to prevent access by vermin. This concrete was pumped into the station and through core holes pre-drilled in the new slab. The temporary walkway was lifted and replaced on a nightly basis to allow works to progress and ensure a safe route was left for passengers each morning. We laid screed on top of the new deck followed by new Granazzo Cem Terrazzo tiles. The complete area of the walkway was tiled along with the ramp on the overbridge to meet the new levels.
Stainless steel backed phenolic riser plates were fitted to staircase 1/604 along with new handrails to replace the existing to bring the staircase within full DDA requirements. Tactile paving was installed at the top and bottom of staircase 1/604 and 1/602. The lower landing of 1/604 was broken out and regraded prior to the laying of MMA resin to a fall which matched the height of the new tactiles.
Due to the change in levels the skirting on the walkway and overbridge was repainted. We also painted the exposed steel beams in the equipment rooms below the existing walkway to prevent further corrosion and as a check on progressive water ingress in these rooms.
The Aco drainage channel at the junction between the walkway and the overbridge was covered when the new deck was installed. A new Aco channel was concreted into position at the required height along with new stainless pipework to connect it to the track drainage in the lobby area below the walkway.