Cunene River Bridge
The challenges of building Angola’s longest bridge
The Cunene River Bridge in south-western Angola, which is of strategic importance to the main arterial road linking Angola to other Southern African countries, had been destroyed early in the Angolan conflict. The project involved the construction of a new bridge 20 m downstream of the remains of the original bridge structure, to the north-west of the village of Xangongo.
The new bridge is 880 m long, spanning a perennial river channel approximately 100 m wide, and then crossing the major part of the flood plain for 780 m to reach an embankment that traverses the remainder of the flood plain. Zutari provided the design and preparation of bid documents, as well as site supervision, in joint venture, for the new bridge, together with additional approaches and drainage structures.
The construction of the new Cunene River Bridge was an award-winning feat of engineering, carried out under immensely challenging conditions. The logistical and natural challenges posed by the project included the presence of landmines, floods (the plain is regularly inundated during the five-month rainy season), the width of the river, shortage of skilled labour, difficulty acquiring building materials due to the distance from commercial centres, lack of suitable aggregates, long supply lead times, and challenging importation procedures and border delays.
Poor foundation conditions prompted a bridge configuration design with fairly long spans and a lightweight deck. The most economical solution was a 50 m span length and a composite steel/concrete deck type formed from dual steel box girders, with an in-situ infill concrete slab.
Proudly spanning the Cunene River, the new bridge is both serving its commercial purpose, and acting as source of pride and achievement as the longest bridge in Angola for the people of the region.
The fabrication of 142 box girder sections in Qing Huang Dao, China, was completed concurrently with the construction of 1 384 precast concrete deck slabs on site in Angola. The box girders were shipped to the Port of Namibe in Angola and transported 600 km by road to the Cunene River Bridge construction site.
The choice of a composite construction design had the advantage of allowing the manufacturing of the structural steel substructure in parallel with the construction of the concrete substructure. Once the steel box girders had been launched into position, construction of the concrete deck could continue uninterrupted and without being affected when the river flooded. Before the bridge sections could be launched, reinforced substructures consisting of 16 piers and two abutments, founded on piles, had to be constructed. An assembly and welding yard were established at one end of the bridge to weld girders together, two at a time, and then incrementally launched using hydraulic jacks.
Expert project planning resulted in the successful delivery of the new bridge despite the many challenges. Proudly spanning the Cunene River, the new bridge is both serving its commercial purpose, and acting as source of pride and achievement as the longest bridge in Angola for the people of the region.
*The Aurecon Africa business has been officially renamed Zutari as at 21 July 2020. Zutari acquired Aurecon Middle East on 20 November 2020.
