Rickmansworth bridge replacement, London
ALE has carried out the successful removal and installation of overbridge MR88 in Rickmansworth in North West London, UK.
The existing bridge weighed approximately 80t and was removed utilising 16 axle lines of SPMT in a 4 file 8 configuration. The SPMTs steelwork packing consisted of a jacking frame and climbing jacks. The climbing jacks enabled the old bridge to be lifted from its bearings and clear of all obstacles on the abutment before being driven back to the compound ready for demolition.
The new bridge weighed approximately 150t and was installed using another 16 axle lines of SPMT in a 4 file 8 configuration. Again, the SPMTs’ packing consisted of a jacking frame and climbing jacks. The new bridge had to be driven in below the services and above the new cill units, which were at various levels.
The bearings were attached to the underside of the bridge prior to the bridge move. The bridge was lowered down utilising the climbing jacks on the SPMTs and the bearings were lined up with pre-formed pockets in the cill units by incorporating alignment gear into the scheme.
There were several major challenges that ALE needed to overcome to ensure that the scheme was a success. Due to space restrictions in the site compound, it was necessary to rig the SPMTs during planned night time road closures and prior to the possession, as well as de-rig the SPMTs during the planned night time road closures during the possession.
Another challenge ALE faced was moving the old bridge into the site compound up a steep ramp. ALE used a tractor unit to assist with pulling the SPMTs and old bridge off the road and into the compound. This operation had to take place within a one hour window due to traffic management restrictions.