Due to open in March 2016, this impressive complex will feature CCL’s 37×32-metre transfer slab, supported by four columns along two opposite lengths and shear walls to the other two sides, with post-tensioning installed in one direction.
The design features 12-metre-high walls, planted on the slab towards the mid-span, and several voids. Meanwhile, in order to counteract punching shear above the columns, the slab’s two-and-a-half-metre thickness was increased to three metres around the columns.
Challenges and Considerations
Understandably, there were a number of challenges during the design and construction phases that, if no solution was found, could potentially cost the contractor both time and money. The first of these issues was the impressive size of the slab itself.
On first view, the self-weight of this imposing transfer slab would require the support of specialised scaffolding – totalling three stories in height – incurring a substantial additional cost in the process.
In order to avoid this, CCL’s design team conceived a solution that would be delivered across two phases.
Initially, the slab was cast at a depth of 1150mm directly above the columns and 850mm along the slab, with shear links designed to protrude from the slab at this stage of the build.
These dimensions allowed the slab to be supported by traditional – cost-effective – scaffolding and strong enough to safely carry its own weight.
CCL then set about casting the second phase, which would complete one single unit measuring 2500mm deep, increasing to 3000mm around column points.
This innovative approach resulted in one singularly large transfer slab, cast and secured in two sections yet performing as one complete element.
With site operatives needing to traverse the slab between both phases of the design, CCL’s engineers intelligently incorporated a pathway into the shear links’ layout pattern during the design phase.
This provided staff with a clear passage across the slab between stages and without abating design efficacy or structural integrity.