need to modify the fundamental grid of the support structure in a number of

Need to modify the fundamental grid of the support

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need to modify the fundamental grid of the support structure in a number of areas. These changes were introduced at a critical time: the implications were dramatic. The changes required to the critical structural design were both local and global. The architectural changes listed above affected the fundamental support system of columns and beams, which were already heavily loaded (for example via escalators). Changing the location of major masses and the location of the main lateral load resisting systems has a direct effect on the lateral seismic resistance, which is one of the critical load cases to be addressed. It was therefore necessary for the structural models and calculations first submitted as part of the Interim Design process to be recommenced, since it was now essential to derive a new vertical load carrying system down to foundation level and to re-assess the ability of the modified arrangement to resist lateral forces and cope with associated displacements. Only once those calculations were resubmitted and approved could the Contractor proceed with his Detailed Design work. In effect, the interim structural design had to be re-run. That redesign work was in progress when on 20 September 2011 the Engineer, following notification by the baggage handling system (BHS) contractor, instructed the contractor to revise the structural loads associated with the BHS systems. This was seven months after the commencement date and 10 months after the Contractor had begun work on the substructure structural design. The BHS system is always at the heart of any airport terminal project. The areas of the PTB affected by the loading changes were
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already the key work areas, and were now on the critical path of the project. Further redesign was necessary and structural calculations had to be recommenced once again. On 22 October 2011 those calculations were completed. Only then could detailed structural design for the critical zones of the PTB substructure properly commence. The contractor did everything within its power to mitigate the impact of these very late changes from the employer. It started work on the EI # 1 design in June 2011 before it was formally instructed. It agreed to submit the structural detailed design in separate phases and zones, to assist the engineer's review process. Works were started on site when drawings became available, in order to pour concrete where it was possible to do so. On each occasion, the contractor was entitled to insist on following the sequence set out in its baseline program, but did not, following repeated requests from the Engineer. However, despite its best efforts, significant delay to the project was inevitable. The Contractor warned the Engineer on 17 July 2011 that the instruction of EI # 1 would cause significant delay and additional cost. Three days later, the Engineer formally issued the instruction on behalf of the Employer, in full knowledge of the Contractor's time and cost estimates. The Engineer then
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