Girder beam installation for London Bridge Station, UK
ALE installed six curved girders to form part of a new viaduct for the London Bridge Redevelopment Scheme. The works utilised 16 axle lines of SPMT and four 30t scissor lifts which were connected to the bed of the SPMT.
ALE were contracted by the client to transport and install six number girders to form part of a new viaduct in an agreed sequence. The six curved girders ranged in weight, from 50t – 70t, and from 19m to 32m long.
ALE utilised 16 axle lines of SPMT and four scissor lifts which were connected to the bed of the SPMT, allowing the beams to be lifted safely to the required installation height.
It was not possible to use a crane as its loadings would overload the existing structure below, which formed London Bridge underground station.
A 30t air hoist was connected to the outer girders of the RAV (Railway Approach Viaduct), an existing viaduct, via a beam and was used to offload the SPMT, engine and scissor lifts. No equipment or materials could be left in the road under the RAV, as access was required by News International.
The girders were bought to site on extendable trailers during a series of weekend bus station closures and offloaded under the RAV. The girders were jacked-up to a height where the SPMT and scissor lifts could fit underneath. The girders were then secured to the scissor lifts and driven out from under the RAV into the bus station, where the scissor lifts were powered up and the beams lifted to installation height.
The SPMT was then driven over the roof of London Bridge underground station ticket hall, which was constantly monitored throughout the works, into the beam installation position. The beam was slowly lowered down to approximately 25mm above the temporary bearing to allow any minor changes to be made before finally landing the beam. The beam was then secured by the client onto the temporary works. Once secured, the scissor lifts were fully lowered and the SPMTs moved from under the girder and parked ready to collect the next beam.
ALE faced several challenges during the project. There was a maximum ground bearing pressure allowed on the roof of London Bridge underground station (the installation location for the girders). This meant that the ground bearing pressures had to be kept low. Furthermore, it was not possible to get a crane big enough into the newly formed bus station to be able to offload and install the girders.
ALE provided experienced engineers throughout the design stages and the engineers involved then carried out the site works so there would be continuity throughout the scheme. Preparation and design works took approximately eight months and the operation took one month to execute.