Temporary Platforms for the Construction of Montgomery Bridge, Canary Wharf
A new 26 metre bridge is being constructed to provide vehicular and pedestrian access between Montgomery Square and the new Wood Wharf development in Canary Wharf. RDG were involved in the initial phase of construction which required access for the positioning of steel casings for the foundation piles of the new bridge.
A pair of platforms were designed using RMD equipment to cantilever out over the water to the specific location where the piles were to be imbedded. The piling rig was located on a stabilised barge which was positioned alongside both of the platforms in readiness for piling. Due to the position of the London Underground Jubilee line running below the water bed the location of the piles had no flexibility.
The basic design brief for both platforms was to provide a safe working platform suspended above the water level with a safe working load of 2.5 kN m-2. The platforms had to have local strength to resist impact from moving pilling casings as they were guided into position. In addition both platforms were to be designed to resist impact from the floating stabilised barge whilst they were being positioned alongside the platforms.
The first of the two platforms was a simple cantilever over the edge of the Montgomery St. wharf wall using packing pieces to ensure the platform was level and precast concrete blocks positioned at the rear to provide counter ballast. The second platform to the south side of the site required greater design ingenuity due to a perimeter secant pile wall which could not sustain any support. A residual void left behind the secant wall after its construction provided an opportunity for constructing an independent RMD structure that could cantilever out without resting on it. The structure was restrained at the rear off an existing reinforced retaining wall. Due to casing cut off levels, the access platform had to be positioned as low as possible which resulted in the underside of the platform skimming the top of the existing secant wall. From this location the pilling access platform was further modified to incorporate pile locations that also cantilevered to the sides as well as directly in front. The combination of using standard RMD frames and equipment became challenging when large cantilever lengths were required with minimal increases in platform thickness. This was achieved and provided a ‘tooth edge’ profiles cantilever platform extending 4.000m over the secant wall. Perimeter edge protection was provided to ensure safety of the piling operatives.