Construction World March 2018

FROM LEFT: The completed Tugela River Bridge; Engaging with local community was a priority throughout construction at the steep access to site; Inaccessible site caused work to be more labour-intensive and Suspension bridge main cables erected.

undertakes designs. For that reason, although the design procedure for the structure followed a regular process, the design innovation goals for this project were to deliver increased value to the local community, successfully complete the project safely, on time and within budget, and to exceed Client expectations. Value to the local community was achieved through giving special attention to the bridge aesthetics and ensuring that the bridge was in harmony with the natural environment, specifying finishing details in securing the cable and hanger ends, end-plates at the ends of the decks, and double-nuts to all connections to negate the risk of bridge elements being tampered with over the long-term. In addition to the above, Hatch spent excessive time and effort to educate local community members on the bridge design, project progress, and construction activities. This, along with the collaborative effort with the Contractor to resolve site challenges, allowed a high-quality product to be delivered on time and within budget. Innovative technology The challenges associated with the Location of the Works resulted in increased demands for work execution by skilled labour. Large mobile cranes and cherry-pickers, which would have normally been used during the construction of the concrete and steel portions of the tower elements, and during the erection of the suspension bridge cables; were unable to access the site. The site was also inaccessible to concrete-supply trucks and all concrete was therefore batched on site. Transportation of materials to site was an additional challenge. The Prefabricated Parallel Wire Strand suspension main cables weighed approximately 12 kg/m, or an approximate total of 3 tonnes for one main cable that was erected across the bridge length. The main cables were pulled across the bridge length and seated in the saddles of the tower elements largely through manual labour operations. A special temporary working platform footbridge was then positioned below the free cable profile to enable work at a convenient height for the remainder of the suspension bridge work, such as the cable clamp and hanger erection, and deck erection. Environmental Impact Consideration Limiting the environmental impact was the governing consideration in the Hatch design process and in the choice of bridge type. Consequently, the limiting design restraint was that the bridge piers could not be located within the river, and this resulted in the bridge deck being required to span 130 m between piers intended to be positioned on the river banks at the narrowest crossing point of the river. Steel material then became a natural choice for the bridge

deck construction, since it is much lighter than the concrete alternative and is therefore eminently suitable for long span bridges. A suspension bridge structure was envisaged to be a suitable mechanism to support the deck loads at incremental distances along the deck length from above, as opposed to providing pier supports below the deck. The bridge design was therefore a solution that minimised environmental impact while also being economical and aestheti- cally pleasing. 

The bridge prior to attention on aesthetics and safety finishes.

Project information • Client: KwaZulu-Natal Department of Transport • Contract value: R7 782 065 • Project start date: 2012 • End date: June 2017

• Main Contractor: Ingonyama Nicon • Consulting Engineer: Hatch Africa • Steel Contractor: Steelcon

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CONSTRUCTION WORLD MARCH 2018