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5 Audit Task 'a'. Load model for main cables
The objective of this task is to consider whether the assessed loading of the main cable can be accepted as accurate and whether it has been subject to the level of independent verification expected of a project of this nature.
A detailed load assessment has been carried out of the bridge by Fairhurst examining both the permanent and superimposed dead loads.
From the information made available during the period of the audit, it is understood that assessments of the permanent loads have been undertaken for FETA by both Faber Maunsell and Fairhurst; the latter being well placed to carry this out given their history and involvement with the Forth Bridge over many years. It is understood that close agreement was made between Faber Maunsell and Fairhurst of their separately calculated loadings of the main cables (to around 2%). Although there was no formal requirement for a 'Category III' check to be made of the permanent load assessment, both parties indicated that they considered their efforts represented the level of effort and independence required of a Category III check and will certify the structure to this effect. With such close agreement between the two exercises it was considered that there would have been little benefit in repeating this exercise during the period of the audit.
Discussions on the BSALL live load assessment were held between Flint & Neill Partnership and Fairhurst on Tuesday 13th December. Our review leads us to consider that the approach taken by Fairhurst is slightly conservative, albeit the degree of conservatism is sufficiently small with respect to load effects in the main cable that we would not recommend any refinement or third party review at this stage. The load effects in other elements were not reviewed as they were outside the scope of the audit. (1.1 - 1.10)
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