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COMPANY AWARDS

In 2009 Ibhayi Contracting won the Fulton Award in the Special Category: Repair & Maintenance Project, for the concrete retro tment solutions utilized at the Van der Kloof Dam spillway bridge.

Mr.RetselisitsoeMaliehe (Ibhayi Contracting) and Mr. Phillip Ronné (BKS).
Mr.RetselisitsoeMaliehe (Ibhayi Contracting) and Mr. Phillip Ronné (BKS).
The Van der Kloof Dam spillway bridge.
The Van der Kloof Dam spillway bridge.

This project honors the unique concrete solutions employed to retro t the Van der Kloof dam spillway bridge. The Van der Kloof dam spillway bridge provides a vital ling over the Orange River for tourism, the surrounding rural communities and in particular for the agriculture- originated heavy vehicles. The client closed the bridge to public traf c, based on road users reported experiences of ‘rollercoaster” sensations and anticipated structural defects.

The Van der Kloof dam is South Africa’s highest concrete double curvature arch dam wall and South Africa’s second largest dam by storage volume. Comprising 15 spans with an overall length of 204 m, this bridge structure is classi ed as a major bridge and is positioned at signi cant height above natural ground level. These physical constraints further complicated the nature and scope of the rehabilitation work.

A forensic engineering approach, comprising a comprehensive suite of concrete material tests, visual inspection by experts, thorough review of record drawings and advanced structural modeling, was utilized to determine the characteristics and extent of the defects. Signi cant longitudinally-oriented cracking was observed in the deck slab, midway between adjacent longitudinal beams. The detailed structural assessment indicated that the existing superstructure con guration utilized two end transverse beams in each span and relied on the deck slab to provide transverse stiffness to the structural system. This resulted in the commissioning of specialized vibration-based dynamic testing of the superstructure, conducted by the University of Cape Town.

This state-of-the-art vibration-based testing quanti ed the dynamic response of the bridge superstructure and con rmed that inadequate transverse stiffness was the root cause of the serviceability limit state defects. Poorly functioning bridge bearings were also a signi cant structural concern.
The design utilized a systems approach that integrated the retro tment activities, rehabilitation works, routine maintenance, access, legislative safety and environmental requirements. Technically challenging retro tment activities performed at the Van der Kloof bridge superstructure included the installation of new reinforced concrete transverse beams and the construction of a fully-bonded concrete pavement (or roadway); while routine rehabilitation activities included concrete repairs, replacement of bridge bearings, replacement of expansion joints and other ancillary works. The new transverse beams were constructed by introducing viscosity-controlled self compacting concrete through holes cored through the existing deck slab into suspended steel shutters housing a reinforcement cage dowelled through the existing longitudinal beams. The physical constraints posed by the double curvature arch dam wall and the envisaged scope of work at the spillway bridge resulted in the development of innovative temporary access systems.

The success of the retro tment actions was quanti ed by repeating the specialized vibration-based evaluation post-retro tment. Quanti able improvements in the transverse stiffness, as much as 25 times, were achieved for the retro tted structure.

Despite the technical complexity of the retro tment solutions, superior compliance with environmental management plans, as well as occupational health & safety plans were integrally achieved with the technical tasks. A signi cant economic contribution was made to the local communities via experiential training and employment opportunities.

As quoted from the Fulton Awards 1979 – 2009 Concrete Beton Journal, Concrete Society of Southern Africa.

From left to right: Mr. Smuts (BKS), Mr. A Newmark (BKS), Mr. T Maliehe (Ibhayi Contracting), Mr. P Adams (Sika), Mr. P Ronné (BKS), Mr. N Wild (Sika) and Dr. C Oostuizen(DWAF)

From left to right: Mr. Smuts (BKS), Mr. A Newmark (BKS), Mr. T Maliehe (Ibhayi Contracting), Mr. P Adams (Sika), Mr. P Ronné (BKS), Mr. N Wild (Sika) and Dr. C Oostuizen(DWAF)