Construction World December 2017

Category A1: Civil Engineering Contractors

CONSTRUCTION OF PEDESTRIAN BRIDGES ON NATIONAL ROUTE N17 PROJECT INFORMATION

• Company entering: Stefanutti Stocks Civils • Client: Sanral

Stefanutti Stocks Civils was awarded the contract for the construction of three pedestrian bridges across the N17 highway by Sanral in January 2016.

metres above the surrounding terrain. The soffit of the deck has been built to a concave radius of 450 metres. The geometry of the V-shaped pylons required that the pylon be constructed in three lifts using self-compacting 50 Mpa concrete which was pumped into the formwork moulds. One of the features of this bridge, and in fact all three bridges, is that there is no supporting column in the median of the highway. This a safety feature specified by the client at design stage. This eliminates the possibilities • Contract value: R75-million • Start date: January 2016 • End date: 31 August 2017 • Main contractor: Stefanutti Stocks Civils • Principal agent: SMEC South Africa • Project manager: Sanral • Consulting engineer: SMEC South Africa of vehicles colliding with a column in the median, which recent events in Johannesburg have shown can be quite catastrophic. The Sanral concrete specifications for the contract required that the bulk of the 3 000 m 3 of concrete for the bridges be 40 Mpa durability (W) concrete. The concrete for all three bridges was therefore supplied by AfriSam from their Nigel and Prolecon plants.

The primary purpose of the project was to provide safe walkways over the highway for local residents who would otherwise be crossing the highway on foot, which has previously resulted in motor accidents and fatalities. The bridges are named Regents Park, Ergo and Kwa Thema, the names based on their localities. There has been particularly heavy pedestrian traffic in each of these Ergo bridge is situated at km 27,4 of section 2, approximately 2 km east of the Ergo gold processing plant. The bridge consists of a 42 metre main span across the highway, 40 metres of adjoining back spans, 220 metres of access ramps and staircases which lead up to the main span. The bridge structure is of reinforced concrete, with post tension cables installed over the main span and back spans. The soffit of the main span and back spans has been formed to concave radii of approximately 400 m and the tops of the supporting upstand beams have been formed to convex radii also of approximately 300 m. This results in a very sleek, aesthetically pleasing structure. The geometry of the bridge made for complicated formwork designs during particular spots. Ergo Bridge

construction in order to achieve the desired lines and shapes specified. The bridge crosses the highway at an angle of 63 degrees. Kwa Thema Bridge Kwa Thema Bridge is situated a further 3 km on towards Springs. Its design is similar to that of Ergo bridge, but crosses the N17 highway at 90 degrees to the traffic flow. This results in a slightly shortened main span of 37 metres. It also has 35 metres of back spans and 140 metres of access ramps leading up to the main span. Similar to Ergo bridge, the deck soffits and upstand beams have all been formed to concave and convex radii varying from 220 metres to 140 metres respectively. The resulting lines and shapes give an aesthetically pleasing structure. Regents Park Bridge Regents Park Bridge is situated at km 55 of section 1 on the N17 highway and provides a valuable link for pedestrians travelling from City Deep to Regents Park. The bridge is a reinforced concrete suspension cable bridge with a main span between pylons of 57 metres. The curved concrete deck is suspended from suspension cables that are anchored at the two pylons on either side of the highway. The two V-shaped pylons tower 13

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