Civil Engineering March 2022 | Vol 30 No 2

40 March 2022 Civil Engineering D ue for completion in April 2022, the reservoir is being built by CSV Construction on behalf of the City of Cape Town, with Cape Concrete supplying the precast elements for the structure’s 14 500 m² roof. The water storage unit is 160.5 m long and 90.9 m wide with a maximum water depth of 8.5 m. The structure comprises an in-situ 200 mm concrete floor flanked by 5.5 m high 1:2.5 sloping concrete embankments topped with 4.6 m high vertical retaining walls. The roof’s precast beam and hollow-core slab assembly is supported by 99 in-situ concrete columns measuring 9 m × 700 mm, supported on elastomeric bearing pads. ROOF DESIGN The roof has an apex on the longitudinal centre line and slopes at 1:150 to the perimeter walling on either side for drainage. The first roof section was completed in August 2021, followed by the second section in November 2021. The roof comprises 48 panel sections, each consisting of two or three hollow-core bays with 11 hollow-core slabs in each. The panel sections are interlinked with transverse in-situ beams which run the full width of the structure, thereby creating larger panels and a more robust structure. Cast with a joint former between them, these beams also act as expansion joints. The 8.8 m (length) × 1.2 m (width) × 200 mm (thickness) hollow-core slabs are supported by 108 I-beams and the perimeter walling. The I-beams measure 13.5 m (length) × 1.2m (height) × 500 mm (base width). Massive reservoir roof constructed with precast concrete The construction of a 100 Mℓ reservoir in Contermanskloof, Cape Town is soon to be completed. The mammoth structure makes use of precast concrete I-beams and hollow-core slabs to support a roof comprising 48 panel sections.