Olifants River Bridge Widening

HHO Consulting Engineers, Cape Town, South Africa

^* Corresponding author: andrew@hho.co.za

Abstract

The Olifants River Bridge B3611 carries the N11 over the Olifants River, just North of the Loskop Dam. This structure was originally built in 1979 and was recently widened as part of the South African Roads Agency Limited (SANRAL)’s upgrade to the N11. At the time of design, very little was known about the bridge as no ‘As Built' drawings were available. Due to the remote locality of the structure, exploratory investigations were reserved until the construction phase. The final design solution was therefore amended during the construction phase in order to account for the reinforcement found within the structure. In addition to the heavier dead weight of the new widened deck, the bridge would be required to carry higher loads under modern loading codes. Widening works included new widened cantilevers with new reinforced concrete balustrades, tying into existing reinforcement. Strengthening for bending was provided to the main deck beams by means of longitudinal FRP plates epoxied to the soffit. Transverse pierhead strengthening using DYWIDAG bars was installed to counter increased moments, and pier strengthening using a reinforced concrete jacket was implemented to strengthen the piers. Durability concrete was specified in accordance with current SANRAL regulations and the durability performance of the concrete, even in this remote location was excellent. This paper summarises the work that was completed as part of this project.