CMA AWARDS FOR EXCELLENCE :
Article Date: 15 October 2008
CMA AWARDS FOR EXCELLENCE 2008
CATHAY INDUSTRIES TROPHY WINNERS
CONCRETE RETAINING BLOCK WALLS
R2-7 Suikerbossie Nek - Houtbay
Joint Cathay Industries Trophy Winner Category – Retaining Wall Elements: retaining walls > 3m high, constructed from concrete retaining block elements.
This retaining wall project began when two engineering firms, Jeffares & Green and Mike van Wieringen and Associates were requested to investigate a cut slope failure at Suikerbossie Nek, situated above Victoria Road between Camps Bay and Hout Bay.
The engineers found that erosion and collapsing were caused by the angle of the slope. Although initially stable in terms of wedge or slip circle failure, over time the slope had been rendered unstable through weathering which reduced its surficial strength parameters. In addition, non-functional surface cut-off drains, situated above the cut face, had accelerated erosion and slip failure. Moreover, a lack of regular maintenance had led to silting and vegetation growth in the drain, resulting in choking with consequential over-topping.
Duncan Murphy, a civil engineer at Jeffares & Green, outlined the nature of the failure: "At some point erosion activity would have intersected the cut-off drain, and the formation of a large eroded gully in the cut face would have been the likely outcome. This could have resulted in the formation of a deep and irreparable gully extending a considerable way up the slope. Moreover, judging by the crack pattern in the head-scarp, a significant collapse onto the road during a period of high rainfall, was imminent."
Remedial options such as gunite and soil nails or an 8,5m vertical concrete retaining wall were discarded for aesthetic reasons. Instead a combination of a near vertical gabion toe wall up to 2,5m high, a 35º Terrafix covered slope topped with a concrete-lined cut-off drain, and Terraforce L12 side walls, was the option selected. Terrafix 150 blocks were laid to trap the maximum amount of topsoil on the face, a solution which has prevented erosion and weathering, and encouraged plant growth.
Because the slope was large and curved, near-horizontal concrete infill walers were used at five metre intervals to fill the uneven spaces between adjacent panels. These were secured with anchor bars so that any possible pressure on the gabion wall would be reduced, and Terrafixes' maximum laying density of 10 blocks per square metre was used to prevent lateral sliding.
Thousands of water-wise indigenous plants, ground cover and bulbous species, were planted and these have started to relieve the nondescript appearance of the slope.
Professional Team
Engineer: Jeffares & Green / Mike van Wieringen and Associates
Contractor: Dassenberg Retaining Systems
Manufacturer: Klapmuts Concrete
Lincensor: Terraforce
Product Information
150 Terrafix blocks
Terraforce L12 blocks (Sandstone)
Judges' Comments
A project visually sensitive to its context. The anchoring wall and landscape planting was well done.
SUSPENDED CONCRETE FLOOR SLABS
S1-1 Bridgeview Apartments – Braamfontien, Johannesburg
Joint Cathay Industries Trophy Winner
Category – Residential: houses, flats and townhouses
This five-storey high-density apartment complex in Braamfontein is South Africa’s tallest structure to date in which hollow-core concrete floor panels have been used.
The project required the use of two cranes to hoist 5 848m² of 150mm panels into position, a 30-ton mobile crane, and a tower crane for the upper levels. Despite space limitations on site, the storage of panels was never a problem; they were simply installed directly off Echo delivery trucks.
The Echo Prestress system is an ideal solution for multi-level load-bearing masonry structures such as Bridgeview, and as no propping is required, construction advances quickly. Other alternatives would have required back-propping all the way.
One of the building’s special design details was that a balcony over-hang effect was achieved with cantilever beams, and this created the illusion that the slabs were free-hanging.
According to Knutton Consulting, when used in conjunction with suitably detailed load-bearing masonry, hollow-core concrete flooring can be employed in buildings as high as seven storeys.
Professional Team
Architect: Messaris Wapenaar Partnership
Engineer: Knutton Consulting
Contractor: Dalmar Konstruksie
Manufacturer: Echo Prestress
Product Information
Echo Prestress 150mm slabs.
Judges’ Comments
Good design detail, particularly the overhang for the balcony. Innovative project.
CONCRETE ROOF TILES
T2-2 Pinnacle Estates – Sandton
Cathy Industries Trophy Winner
Category Residential B: houses and housing complexes with a unit area of 50 – 100m².
These townhouses embody style and sophistication. Marley’s Ludlow roof tile was selected for its flat, ribbed profile, clean lines and high performance. When combined with simple roof structures such as these, the tile accentuates innovative urban living, without impinging on the architecture of the development.
Professional Team
Architect: Hub Architects
Contractor: Summercon Holding Company
Manufacturer: Marley Roofing
Product Information
Marley Ludlow M22 roof tiles (Slate)
Judges’ Comments
Interesting and innovative use of the roofscape, which doesn’t dominate the overall design of the townhouses.
CONCRETE MASONRY
M3-5 Red Location Museum – Port Elizabeth
Cathay Industries Trophy Winner
Category - Commercial & Community: shopping complexes, office blocks, hotels, parking garages, recreation and entertainment centres, education and training buildings, churches, government and municipal buildings.
At the end of the Anglo Boer War in 1902, the British left a settlement of rusted corrugated iron huts on the outskirts of Port Elizabeth. Over time many black families settled in the area which later became known as Red Location. Owing to some important political and cultural leaders who were raised in the township, Govan Mbeki, John Kani, George Pemba and Raymond Mlaba among them, a decision was taken build a museum.
Red Location Museum is a robust, down-to-earth structure which will endure for many generations.
One of the requirements was for the building materials to blend in with the surrounding structures which consisted mainly of concrete and corrugated iron. The choice fell to Deranco’s grey Hollow Blocks and these were accurately laid in grid-type panel formation to match the concrete columns and other structural elements. On completion the final block work enclosed a large single-volume space.
Professional Team
Architect: Noero Wolff Architects
Engineer: De Villiers & Hulme
Quantity Surveyor: Walters & Simpson
Contractor: Alfdav Construction in association with SBT Construction (Eastern Cape)
Manufacturer: Deranco Blocks
Product Information
Hollow Blocks (Grey) 390 x 190 x 90mm
Hollow Blocks (Grey) 190 x 190 x 90mm
Judges’ Comments
This design celebrates the true appreciation of the use of concrete and shows the adaptability of concrete block work, with detailing conforming to the design. The landmark building set a benchmark in the application of concrete technology, and the application of design and materials were technically sound.
CONCRETE BLOCK PAVING
P1-14 Waterfall Equestrian Estate – Gauteng
Cathay Industries Trophy Winner
Category Residential: paving around residential buildings, driveways, footpaths, courtyards, patios and pool decks.
SmartStone’s timeless Huguenot Cobbles were used in conjunction with raw materials from the Lonehill area to create this exceptional driveway. Communal stables are a feature of the estate and the equestrian theme is evident in the design of the driveway, which was inspired by a cartwheel. The spokes of the ‘wheel’ were made from a combination of railway sleepers and stone, and its ‘hub’ plays host to a garden with indigenous plants and overgrowth.
Professional Team
Contractor: REE Paving
Manufacturer: Smartstone Midrand
Product Information
Huguenot Cobbles (Sandstone)
Judges’ Comments
The final product is well constructed, with good attention to detail. It blends in well with its surrounding environment.
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