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Project Description
Deep in the rainforest of Equatorial Guinea, the government is building a new capital city: Oyala. These three cable-stayed bridges across the Wele River were completed in 2011, 2012 and 2014; respectively. They will become a new emblematic entrance to the new city and have been designed to have a clear identity without disturbing the natural environment.
The three bridges share similar characteristics. They are all 135 m long, with a main span of 80 m. Being 22.6 m wide, the deck is wide enough to accommodate six vehicular traffic lanes, a central median, and two pedestrian walkways. The deck is a composite steel-concrete structure supported by two cable planes and consists of two 1.4 m deep prestressed concrete girders, which are supported by stays spaced at 6.7 m. Transversally to these girders, steel beams support the top concrete slab. The two stay-cable planes are connected to four pylon legs, forming an H-shaped pylon with open legs at the top. Each mast has a total height of approximately 27 m, of which 21 m are above the deck.
Design/Construction Approach
Advanced software was used for the structural analysis of the bridges. The models included the substructure, every component of the superstructure and the counterweights of the abutments. Construction of the central span used the balanced cantilever method to reduce impact on the river. During the entire bridge construction process, Pedelta provided construction engineering services. The actual stay forces and precambers were continuously updated to take into account actual site measurements of material properties as well as the duration of the erection stages. Given the difficult access to the site, the minimization of material quantities was a major feature to reduce the construction cost.
Further Information
Sobrino J.A.; Two Cable Stayed Bridges in Oyala (Eq. Guinea). International Bridge Conference. Pittsburgh (USA), June 2012.
Sobrino, J.A.; Oil Refining Industry adds more roads, bridges to Guinea Landscape. pp. 20-24. Roads & Bridges, October 2012.
