Retrofitting of Bridge B421 over the Olifants River after flood damage

Author(s): W. Findlay, F. Kromhout
Paper category: Conference
Book title: Concrete Repair, Rehabilitation and Retrofitting III (ICCRRR)
Editor(s): M.G. Alexander, H.-D. Beushausen, F. Dehn, P. Moyo
Print ISBN: 978-0-415-89952-9
Publisher: Taylor & Francis Group
Pages: 393- 394
Total Pages: 2
Language: English

Bridge B421 is located on Route R555 between eMalahleni (Witbank) and Middelburg in Mpumalanga, South Africa. On 6 January 2011, after heavy rains, road users reported that a large sinkhole has formed in the road behind the eMalahleni Abutment. The routine road maintenance contractor investigated the cause of the sink hole and found that the abutment and wing wall on the downstream side of the bridge has failed. The South African National Roads Agency SOC Limited (SANRAL) contacted an experienced consulting bridge engineer to investigate the reason for the failure.
Bridge B421 is a simply supported 4-span bridge with span lengths of 16 m each. The deck consists of simply supported reinforced concrete voided slabs. The piers are wall-type on spread footings and the abutments are wall-type closed abutments with splayed wing walls. The three piers and the Middelburg Abutment were founded on weathered mudstone, but contrary to good practice, the eMalahleni Abutment was founded on clayey sand. The shift in the river channel due to scour during 32 years had shifted the position of river scour to the one abutment. When the Witbank Dam sluice gates were opened on 6 and 7 January 2011, the lack of foundation support due to undermining scour and rapid drawdown water pressure behind the abutment wall combined to cause half of the abutment to fail completely. Route R555, which carries more than 14 000 vehicles a day was closed for traffic.
This paper describes the investigations done and the actions taken to support the deck temporarily while constructing a new abutment, supported on piles, underneath the overhanging deck structure, as well as additional works to upgrade the bridge.

Online publication: 2014
Publication Type: abstract_only
Public price (Euros): 0.00