The case study focuses on design of the Singapore National Stadium roof and its architectural and structural constraints.The dialog between performance form generation and aesthetics was challenged through several design iterations and is critically reviewed in this paper.The collaboration of engineers and architects gave a form to this significant building that was slightly changed several times due to various conditions.The complex shape of the dome structure was resolved in one parametric model that could react on aesthetical and structural requirements.The landmark roof structure generated in computer had to be evaluated by designers and presented to decision making bodies.

The new 55,000-seat National Stadium is the centrepiece of the Singapore Sports Hub project due to be completed in mid-2014. The stadium features bowl cooling to all spectators as well as the 30,000-seat lower tier being able to be reconfigured and moved to transition from football to athletic and cricket modes. The roof is a highly efficient dome spanning 310 m with a rise of 85 m from the ground level. The fixed roof dome structure will be the largest dome roof in the world covering a stadium and also supports a symmetrical movable roof in two halves. The fixed roof dome structure is formed by a series of arch shaped steel trusses varying in depth from 5 m at the centre to 2.5 m at the base and a post-tensioned concrete ring beam support. These trussed arches are constructed from circular hollow section elements and span in multiple directions and cross the roof opening to form a highly efficient braced dome structure. To manage the design of such a huge multi-element structure, Arup used advanced parametric design software as well as in-house software specifically developed for the project to optimise and exchange information between architect and engineer, and then to fabrication. As well as Arup designing the structure, a second Arup team was engaged by the steel subcontractor to carry out highly complex and challenging connection design. The structure forming the roof is exposed architecturally with the roof having no ceiling or cladding on the underside, meaning that the structural sections and form of the connections are important architecturally as well as structurally. The circular hollow sections used to form the trusses and the truss forms themselves ensure clean and elegant lines within the structure. Due to the movable roof there is a varying load on the structure and fatigue needed to be considered. While the structure is not highly fatigue sensitive, fatigue needed to be carefully considered in the design and form of the connections to ensure that it did not become governing in the design or the structural members. This paper focuses on the architectural concept development, the fixed and movable roof design as well as the post-tensioned concrete ring beam support structure. The paper also describes an exercise to investigate the potential savings in material use that could have been made if higher strength, high elongation steel had been economically viable and could have been competitively tendered. It is shown that it could be possible to make a significant saving on element steelwork if either hot finished Niobium grain refined S500 or S690 could be adopted for similar projects in the future.