The Index Building is an 80-level tower standing 328 metres tall over a seven-level basement. BG&E made changes to the original scheme produced by the concept engineers, Halvorson & Partners, to suit Multiplex’s construction methodology which all formed part of the tender bid.
There were a number of structural aspects reviewed by BG&E, in particular buildability of the tower, especially the large form concrete walls and the two transfer zones located at mid-height and top of the building. Value Engineering involved numerous workshops with Multiplex to develop a method of constructing these elements of the structure while also ensuring that design of these elements was practical and cost-effective.
BG&E ALTERNATIVE DESIGN
Unlike the majority of high-rise towers, this building does not have a central concrete core box and columns supporting the building for vertical and lateral loading. Instead, there are massive concrete portal frames and attenuated buttress walls.
- The initial scheme included an 8m deep concrete beam at transfer level spanning 25m that was very difficult to support during construction. BG&E introduced self-supporting steel trusses strand jacked up to position supporting the construction of the transfer beam and a portion of the 50 floors of structure above.
- BG&E eliminated the structural steel bracing framing that was originally located at each side of the building to all concrete cores. This was all incorporated in the self-climbing formwork and minimised interface issues between concrete and structural steel and also eliminated an extra trade on the work front.
- BG&E’s structural system enables the majority of dead and live loads to be carried by the main concrete buttresses which ensures that the walls remain predominantly in compression. This enables high-strength concrete to support the load with minimal reinforcement as no tension is present in walls.
- BG&E’s value engineering input assisted significantly in reviewing areas of the structure which were modified to suit Multiplex’s construction methodology, reducing the overall project’s construction cost
- Multiplex and the tender team were successful in winning the project which at the time was one of the biggest projects in Dubai.