The requirement was for column free spaces of 2 bays of 150 x 48 meters to accommodate Olympic sized swimming pool, tennis courts and conference halls. Also the roof was required to be sloping RCC with wooded garden on top which imposed heavy dead loads due to soil filling and live load of 5 kN/m2 as public gathering was possible as it was envisaged as public space.
No conventional concrete method was found suitable. So the design that was developed was of 1200 dia steel pipe arches spaced at every 8 meters, which supported 250 dia V-braces at every 4 meters opening up to a mouth of 4 meter each. Thus, a grid of 4m x 4m was formed to support the RCC roof above. The biggest challenge in design was to support RC slab with total loading of 15 kN/sgm for 48m span. The salient feature is that nowhere such a mix of steel and concrete has been used to arrive at the required structural solution.
Since time was of essence, RCC arches were not possible as it would require a lot of time for shuttering & execution and also would have added a lot of unnecessary dead load to the structure making it more expensive. So as explained in the design concept the only solution were steel arches to span 48 meters. 25mm thick plate was rolled into a 1200 dia pipe and segmented arches were formed by welding them together with full penetration butt-weld. The central piece of the pipe was left to be bolted after the erection of the 2 side pieces to facilitate erection. This formed an elegant structure solution to support the RCC floor above.