COVER STORY such as during pre-stressing, after roof construction and after roof depropping, in order to ensure longterm stability. The ring beam was monitored throughout these stages and the actual movements were compared with predicted values. The results indicated that all movements were less than predicted. Prior to the erection of temporary works, the QP (ST) would review the imposed loads of these works on permanent structures. This was to ensure that there were no adverse effects on the permanent structures. Yongnam also installed extensive working platforms within the roof steel structure for assembly and welding of the steel splice joints, to significantly reduce the risk to staff who were working at that height (Figure 16). The Arup design team carried out significant analysis of the effects of concrete shrinkage and thermal movements of the National Stadium concrete bowl structures, at Level 1 and the suspended superstructure levels. In order to eliminate movement joints in the Level 1 slab and therefore reduce complexity, Arup carried out detailed finite element modelling of the effects of shrinkage on this slab and provided additional slab reinforcement to limit and distribute cracking in the slabs. Similarly at the upper suspended levels (Level 2 to Level 7) of the concrete bowl structure, Arup carried out finite element modelling of the effects of concrete shrinkage and thermal variations to minimise the number of radial movement joints required. Only four radial movement joints were adopted in the entire bowl structure, thereby reducing risk in installation. The QP(ST) for the Aquatic Centre and Arena ensured that structural adequacy was met by scrutinising the construction access needs required by cranes. This involved limiting the size of cranes entering the site and in close proximity to
the basement structure (to avoid overloading the sub-structures). QP(ST)’S SUPERVISION PROGRAMME Arup built a Resident Site Staff (RSS) team whose members had comprehensive experience and were competent for the technical challenges of the project. The team was large enough to provide comprehensive supervision across all aspects of the construction. The RSS provided a body of experience and potential for mentorship that enabled the team to op-
erate effectively across such a large project. The RTOs was organised by the CRE and were based on site to inspect all of the construction works. Additionally, inspectors were placed at the Yongnam fabrication yards in both Tuas, Singapore and Johor Bahru, Malaysia. The team followed comprehensive procedures which were outlined in the Arup Project Execution Plan for site works. This outlined the roles and responsibilities for all parties within the RSS team, and the procedures for the gathering and recording of inspection information.
Figure 16:Working platforms installed within the roof structure (indicated in red in the image)
August 2016 THE SINGAPORE ENGINEER
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