Halcrow was commissioned by DML in October 2000 to advise on the adequacy of the existing 9 Dock RAH design.
As a result of this review Halcrow was commissioned by DML to undertake a full and complete reanalysis and redesign of the RAH structure including the crane (the structure by this stage was essentially fully fabricated).
The reanalysis involved formulating a completely new finite element model of the RAH structure in ANSYS, including the 45te high integrity EOT crane located within the RAH and the low level transfer trolley. This model was used for the extreme hazards analyses which include seismic, extreme wind, blast and extreme temperatures. The work also involved impact analysis of the 9 Dock dockside crane hook on the RAH itself.
The structure houses a 45te high integrity EOT crane which is used for raising and lowering fuel onto the submarine reactor. The RAH structure is arguably one of the most complex and nuclear safety sensitive steelwork structures in existence and hence was subject to rigorous scrutiny during its approval by the NII. The RAH substructure box beams were designed in accordance with BS5400 Part 3 – 2000 and the superstructure in accordance with BS5950 – 2000.
The weatherproof envelope to the RAH structure is an aluminium KALZIP system. The cladding is designed for a range of hazard loadings including extreme wind, extreme precipitation, blast, seismic and temperature. Of particular note was the design of the cladding fixings against extreme suction / uplift affects.
Halcrow produced a complete reanalysis and redesign of this existing structure to the latest nuclear standards for ‘new build’ structures all to NII approval in 15 months. This ensured that the HMS Vanguard refit programme started on time. Failure to meet this programme would have seriously compromised the UK’s weapons deterrent.