This serves as an introduction to the accompanying papers on the Tsitsikama bridges. A brief history is given of the evolution of bridges, with special reference to arches. Modern understanding of the design process and design criteria for bridges are discussed in the list of developments in the philosophy of structural engineering. The Gouritz river bridge which, together with the Storms river and Van Staden's gorge bridges, was a forerunner of the above bridges, is descriptionbed in outline and the influence of 'secondary' effects on the results of the analysis is explained.
The Bloukrans Bridge is the largest of three malor arch bridges recently constructed on the Garden Route in the Southern Cape. This paper briefly descriptionbes the procedures followed in the development of the final structural configuration, the main design considerations; investigations, surveys, the geological evaluation of the site and foundation conditions.
The paper descriptionbes the Groot River Bridge and the site in which it is situated. A brief history of the development of the design of the bridge is given, together with some aspects of the final design. Construction problems peculiar to the site are discussed and construction methods used only on the Groot River Bridge, such as the casting of columns to full height In one continuous operation, are descriptionbed.
A descriptionption is given of the steps taken during the development of the design of a large arch bridge, of its analysis and of the structure as it was presented to tenderers and subsequently built.
The simultaneous construction of 3 large concrete arch bridges, of which the one over the Bloukrans Gorge ranks as the 4th largest of its kind in the world, required the development of some sophisticated construction techniques and equipment; the mobilization and commissioning of no less than 5 cable cranes; and the appointment of sufficient and competent construction personnel, capable of achieving the relatively tight programme safely, profitably and to a high standard of quality and workmanship. The completion of all three bridges ahead of their tendered schedules and the subsequent accolades bestowed upon the Bloukrans Bridge in particular are evidence not only of the success of the construction process, but also of the unique relationships which developed between contractor and consultants and which had such marked effects on the end result.