Work was programmed to run concurrently due to late handover. We needed to solve for onsite labour and lay-down area constraints, as well as interfacing with other trades, the need to remove the OTE scope off the critical path plus provide flexibility to accelerate program.
Additionally, we needed to manage the interface between structure and support steel with tolerances only +/-10mm over 172meters despite variation in the cavern walls of 80mm.
Moving away from concrete plenum designs used on previous stations, we were able to transform a stick build structural steel design into an offsite, prefabricated solution allowing multiple services trades and structures to occur simultaneously.
A modular approach comprising 144 modules weighing up to 2,200kg each encompassing the OTE and SA/SE /AE ducts with dampers and access panels, structural steel elements and overhead wire fixing points all pre-assembled and clad with fire protection boards from our factory. Attention was paid to the design of the frame connection plates to allow for movement of cavern structure over time whilst providing adjustment to continue to meet required tolerances. A dedicated offsite assembly and storage facility was used to meet the accelerated install program. We also developed an onsite install approach that eliminated working under live loads and solved access constraints.
“PFS met all program dates and the track handover deadline within a fixed price budget with no variations. Testing and pre-commissioning of the OTE and SE were seamless based on offsite testing quality control. This is the model all stations should adopt.”
