Two awards won - IMIESA , August 2007
Jeffares & Green consulting engineers was the recipient of two prestigious Fulton awards at a gala event held recently by the Concrete Society of Southern Africa. The biennial Fulton awards recognise excellence in the use of concrete in engineering.
A panel of judges rigorously examines a range of diverse nominated projects – from mine shafts to luxury apartments – and the seven award categories are: Civil engineering, Building structures, Sculptures, Aesthetic appeal, Design concepts, Construction techniques and Special category. Jeffares & Green’s winning projects were both pedestrian bridges. The uMkomaas River Bridge (commissioned by the KwaZulu-Natal Department of Transport) won the Design concepts category, and the Bosmansdam Road Bridge (commissioned by the Western Cape Provincial Administration) won the Aesthetic appeal category.
The uMkomaas pedestrian bridge is the first pre-stressed ribbon bridge in Africa, and its clear span of 150 m meets the world record for this type of bridge. The judges cited innovation, simplicity, aesthetics and robustness of design, plus the use of unskilled, local labour as the winning factors in the design category. According to them, this project was not only a bridge between two points, it united two communities. The bridge was commissioned in response to a need expressed by a community in the uMkomaas valley who live on both sides of the uMkomaas River.
There is a trading store situated on one side of the river, and a school and a clinic located on the other side. For years, the river has posed a danger to the community. Jeffares & Green senior partner and bridge engineer, Corrie Meintjes, explains, “How this division occurred is not clear. However, the river poses a danger to the community and many children have lost their lives when swimming to and from school during the rainy seasons.”
The construction of the bridge began in November 2005 and was completed in April this year. Upon completion, the estimated cost of the project was about R3.5-million. There were many challenges during the design of the bridge. Meintjes said that the design and construction of the bridge were unique, as such a project had never been attempted previously in Africa. “An innovative design was required to prevent the swaying motion associated with several types of popular structures, such as suspension and hybrid bridges capable of providing a single span for the required 150m,” he adds.
However, to avoid fears expressed by the community of crossing a bridge that was in motion, Meintjes researched design options and decided on a pre-stressed concrete ribbon structure. This design resulted in Meintjes receiving an Achiever of the Year award from the KZN Concrete Society. The structure is made of a ribbon of pre-cast concrete elements that are suspended from cables tensioned between abutments. The elements are joined and compressed in the longitudinal direction of the bridge by tensioning a second set of cables placed in ducts through the elements. The compressible stress provides continuity in the deck and compensates for the tensile stress resulting from live loads.
One of the challenges that designers faced was the location on which the bridge was to be built. This resulted in the use of pre-cast elements in the construction process, which reduced the amount of construction required on the site.
“It is an innovative all-concrete design, aesthetically pleasing and environmentally responsible and functional. It does not interfere with the flow of the river and does not have stabilisers, towers or large abutments that might have imposed on the rural landscape,” says Meintjes.
The Bosmansdam Road bridge was also designed for a potentially dangerous area. The rapid development of the Montague Gardens Industrial Area, the Marconi Beam and Century City in Cape Town, has attracted traffic to Bosmansdam Road.
Between Montague Drive and National Route 7, large number of pedestrians need to cross the extremely busy road to and from their places or work, during morning and evening peak hours. As a result, the Western Cape Provincial Administration commissioned Jeffares & Green to undertake planning for the upgrading of the Bosmansdam Road, including the design of a new pedestrian bridge. The Fulton judges noted that the confined space that was available for construction made it challenging to achieve an appropriate structure. They praised Jeffares & Green for a design that demonstrated the maximum versatility of concrete, through the use of form and structure. Not only is the bridge functional and aesthetically pleasing, but it also has appropriate screens in place that took into account the concerns of the neighbours, who saw the proposed bridge as a threat to their privacy. Jeffares & Green are thrilled to receive two Fulton awards in the year that they celebrate their 85th anniversary.
This anniversary establishes the company as one of the oldest consultancy firms in structural and civil engineering in the province of KwaZulu Natal. Jeffares & Green has offices in all major centres in South Africa and employs about 300 staff members. In 1997, the firm began an ongoing process of transformation and has reached a level of 33.8% black ownership.
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