Construction World December 2015

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Professional Services

Sundays River Bridge

In 2005, the South African National Roads Agency Limited (SANRAL) found signs of distress and exten- sive cracking in the 14,23 km, two-lane pavement of Section 11, National Route 2 between Soutwerke and Colchester in Eastern Cape. Concerned about the health and safety risk the damage posed to drivers, the SANRAL appointed the Semenya Aurecon joint venture (JV) to rehabilitate the route, which runs north-east and ends at the inter- section to Colchester. The appointment included detail assessment, detail design and documentation. In the assessment stage, it was also found that the Coega Industrial Develop- ment Zone (IDZ) development – the largest of its kind in South Africa – would generate traffic that would require a dual highway by 2015. Taking this factor, the financial viability

By incorporating aesthetic components throughout the design and construction phases to ensure the functional efficiency of the aesthetic elements, the project team delivered a product which serves as a model of an efficient, safe and aesthetically pleasing design. The bridge site is approximately 3 km from the ocean in a very corrosive envi- ronment. The decision to use concrete as the construction material for this project was based mainly on its excellent dura- bility characteristics. Pre-stressed concrete beams were used for the main structural elements of the deck, with a composite precast permanent shut- ters and in situ concrete deck slab. The final construction value of the new bridge came to R44 157 000 compared to a tender amount of R42 760 000. The construc- tion cost of R16 300 per square metre of deck area compares well with similar bridges, especially when considering the very deep piled foundations. The construction of the new bridge over a perennial river with challenging condi- tions, as well as raising the decks of the existing bridge, required innovative design solutions and construction techniques. The bridge was successfully commis- sioned in June 2014 and has seen the road conditions and safety significantly improved, as well as being able to accommo- date the growing traffic volumes generated by the Coega IDZ.

of an upgrade, the existing road’s struc- tural condition, and road capacity implica- tions into account, SANRAL then decided to not only rehabilitate the two-lane route, but to also upgrade it into a four-lane divided highway. The new bridge is 201,18 m long and consists of six spans, each 33,53 m long. The deck is supported by five piers and two abutments that are all founded on piles. Each deck span consists of six precast, pre-stressed concrete beams. Permanent formwork in the shape of precast concrete planks was placed between the beams before casting the in situ deck slab. The deck is made continuous over three spans during the casting of the in situ deck slab to reduce the number of high-mainte- nance expansion joints. The successful construction of the new bridge over a perennial river with challenging conditions as well as raising the decks of the existing bridge required innovative design solutions and construction techniques, such as the implementation of a meticulous and sophisticated technical design process that made extensive use of AutoCAD 3D. The addition of a new bridge over the perennial river provided the project team with an opportunity to incorporate innovative design elements to ensure the optimal safety of the road for the increasing amount of travellers, as well as serving as an aesthetically pleasing addition to the upgraded route.

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Project information • Company entering: Aurecon

• Project start date: 2013 • Project end date: 2014 • Client: SANRAL

• Main contractor: Concor Holdings • Subcontractor: Ibhayi Contractors • Consulting engineer: Dura Soletanche Bachy, Semenya Aurecon JV

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CONSTRUCTION WORLD DECEMBER 2015