Introduction
Groundforce Shorco’s modular hydraulic props have been used for a very different kind of project, not only above-ground but also on a moving structure.
Osprey Group called on Groundforce to provide lateral support to bridge abutments and wing walls during the lifting and transportation process of a new railway bridge replacement at Gipsy Patch Lane in the north Bristol suburb of Stoke Gifford.
The project
The bridge replacement is part of the Cribbs Patchway MetroBus Extension (CPME) scheme, a £57m investment to reduce congestion and improve journey times for road users by providing a new public transport system and an alternative to travelling by car.
The new bridge is a much grander replacement for the existing single-arch brick bridge. With a span of almost 25m, the new structure is a reinforced concrete bridge constructed by Welsh contractor Alun Griffiths.
Challenge
What made this project unique, however, is that the 4,500-tonne concrete bridge had to be transported and installed as one complete unit using a 144-axle self-propelled modular transport (SPMT) unit, supplied by specialist contractor Osprey Group.
Believed to be one of the heaviest SPMT bridge lifts of all time, the bridge was lifted from beneath the concrete deck, the hydraulic props acted in compression to hold the abutments apart and maintain rigidity.
Solution
Seven of Groundforce’s MP150 modular props were fixed across the bottom of the structure, spanning 24.4m beneath the bridge deck. Each prop has a maximum capacity of 1500kN giving a total capacity of 10,850kN.
The props were hung off steel mats using slings and chains with 25mm-thick hardwood packing plates bolted to each of the props’ end-bearing plates to avoid marking the concrete surfaces. With the props in position, they were then pre-loaded in preparation for the bridge lift.
Additional capacity was designed into the propping system as a contingency against any unforeseen events during the operation.
“Using SPMTs to install bridges has become quite a common method, but this is certainly one of the most ambitious ever undertaken in the UK”, said Osprey’s project manager, Mitchell Smith.
After the weight of the bridge was transferred to the SPMT it was then lifted and carried the 85m from the pre-cast yard to its final position. Alun Griffiths levelled and stoned the ground along the route to ensure a flat stable surface for the SPMT.
Throughout the operation, Groundforce monitored the loads acting on each of the props using its wireless load-monitoring system. This meant that Groundforce could also adjust each prop hydraulically throughout the installation process, if required.
The props were delivered to site in October 2020 and the bridge was lifted into position in November 2020.