CENTRAL LONDON DECONSTRUCTION SCHEME

NASC Design Member, RDG Engineering was contracted to design a scheme to enable the deconstruction of two link bridges spanning 16m. The land occupied a heritage site with part of the London Wall beneath. This created loading constraints with a maximum reaction force of 10kN point load or 10kN per square meter. Site access was limited, requiring all materials to be manoeuvred piece small.

The deconstruction required craneage facilities above each link bridge with a capacity of 10t safe working load. The steel column within the building was utilised as a strong point, transferring the crane loads into the foundations of the building. This avoided physical contact with the building fabric, as requested by the client.

Conventional crane facilities usually run on steel. However, this was not a viable option due to the 16m span and site access constraints. The solution was to design a series of aluminium lattice beams to create a lattice girder. A tubular tracking system was placed on top of the aluminium lattice beams.

An access scaffold was erected on the outside of both link bridges to facilitate the removal of the link bridge windows. The scaffold could not be free-standing due to the point load constraints and could not be tied to the building fabric. A birdcage scaffold was designed to fill the void between the two link bridges to transfer the loading from the external access scaffold into a support frame.

The birdcage allowed all horizontal and lateral loads to dissipate to ensure that the 10kN point load was not exceeded.

Skips were positioned on the North side. Materials from the South side were transferred via a tracking system. The system was designed to distribute the load into the ground to ensure the 10kN constraints were not exceeded during the transfer of materials.