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Rock, Paper, Structure
Most of us are familiar with the age-old game rock-paper-scissors played between two people, in which each player forms one of three elements with his hand.
There is a convention determining which element prevails over another. Rock overcomes scissors, but is defeated by paper. Paper overcomes rock, but is defeated by scissors. Scissors overcomes paper, but is defeated by rock. This is a zero-sum game, where one person's gain is equivalent to another's loss. The net benefit is therefore zero.To the inexperienced player, i.e. 99% of players, rock-paper-scissors is a game of chance with a one in three chance of winning. Research, however, has shown that certain strategies can be employed to ensure one's chance of winning.
DESIGN ELEMENTS
Clinix Health Group has commenced working on its seventh hospital that is set to be a game-changer for community healthcare. The new hospital, situated in Soweto, will be named after the late Dr Nthato Motlana, one of the founding members of Clinix Health Group. We at Pierre Badenhorst Engineers (PBE) are privileged to have been working on the civil and structural design and planning of the Dr Nthato Motlana Memorial hospital.While working on the structural design of the hospital, we noted elements with a resemblance to the elements in the rock-paper-scissors game:
- Rock. The site in Protea Glen, Soweto, is classified as a D3 dolomite site. This poses several challenges, both civil and structural, since all designs are required to adhere to the relevant SANS 1963: Development of dolomite land standards.
- Paper. The co-architects on the project (Greenspace Studios & TAG Design) have designed an awe-inspiring building including, among others, large open spaces, cantilevers and overhangs in excess of 6 m, planted slab edges and roof gardens, an atrium roof spanning more than 20 m and slanted columns. Numerous sheets of paper in calculations are required to make this structurally possible.
- Scissors. The hospital is planned to be the first of its kind – a 5-Star Greenrated building. Reductions in cement quantity, virgin steel used, emissions and more must be made to surpass Green Star requirements, minimising the environmental impacts.
The convention has, however, changed. In this situation, the elements do not oppose one another. Here the elements all collaborate towards an optimum and balanced solution. We call it rock-paper-structure.
As opposed to the zero-sum outcome with zero-net benefits, a win-win strategy is applied in the design of the structure. This is a collaborative strategy and resolution process that aims to accommodate all elements.
As opposed to the zero-sum outcome with zero-net benefits, a win-win strategy is applied in the design of the structure. This is a collaborative strategy and resolution process that aims to accommodate all elements.
Various strategies and options were explored to ensure that the hospital building, built on dolomite, is structurally safe and at the same time adheres to the Green Star requirements. The structure will be founded on a reinforced earth mattress and raft foundation system designed to bridge a 5.0 m loss of support, to take into account noncatastrophic failure of the structure. Various options were explored to reduce the dead load of the structure and consequently the required foundation sizes. A structural steel building was considered instead of a concrete structure. The foundation sizes of the structural steel option were found to be 30% smaller than those of the concrete option.
reduced foundations. Special attention is also being given to the design and placement of wet services on the site to ensure that dolomitespecific requirements are met.
The superstructure has various areas, each with different design solutions. In the conventional areas, in-situ reinforced concrete slabs supported on reinforced concrete columns are used. The slab thicknesses are dictated by the span/effective depth ratios to ensure that allowable deflections aremaintained to limit damage to finishes.
The roof over the atrium, spanning over 20 m in some areas, will incorporate steel trusses and beams to traverse the large spans between columns. A Bond-Dek roof slab is proposed over the atrium to reduce nominal dead loads supported by the steel structure. The steel beams and trusses will be adequately fireproofed.
The south-eastern wing of the structureconsists alternatively of three storeys which cantilever more than 5 m over slanted columns. Post-tensioned slabs are being investigated to mitigate large deflections in this area. With the support of Solid Green Consulting, different strategies are being utilised to attain credits towards a 5-star Green-rated building. Concrete mixes will be specified where the absolute quantity of Portland cement, as an average across all concrete mixes, is reduced by 30% to 40% by substituting it with industrial waste products or oversized aggregates.
The project specifications will also require that 60% of all reinforcing or stressing steel, by mass, has a postconsumer recycled content greater than 90%, and that 90% of all steel (structural steel, reinforcing steel, stressing steel and steel products) in the building has a postconsumer recycled content greater than 60% or is reused.
It is clear that an intricate balancing act is required to accommodate all the elements required in the building design. Careful planning is needed to produce the desired win-win outcome.
We call it rock-paper-structure.
The south-eastern wing of the structure will consist of three storeys which cantilever more than 5 m over slanted columns
The hospital is planned to be the first of its kind, a 5-Star Green-rated building