ABSTRACT
ABSTRACT: This Bridge, which is located on the Black River Parkway, a freeway near Cape Town in the Western Cape, South Africa, crosses several railway lines and a major arterial road. The 26 span prestressed concrete beam and slab type bridge has an overall length of 378 m and an overall width of 26 m. Construction was completed around 1965. The structure has a maximum transverse super elevation of 6.8% and a longitudinal grade of up to 3.2%. When the structure was originally constructed the fixity of the deck was obtained by using thin rubber bearings, which were placed directly on the steep transverse and longitudinal slopes of the supporting structure, which consist of columns with transverse trestle beams (A total of 1040 bearings). Significant displacement of the bearings and deck as well as resulting damage to the structure necessitated the replacement of bearings and associated repairs. The final bearing replacement proposal consisted of purpose made structural steel jack supporting units, supported directly from the trestle beams. This adjustable configuration eliminated problems related to height and founding conditions. A detailed analysis of jacking force/deflection recordings using calibrated pressure and deflection dial gauges, was used to determine the final jack release preset for the beam soffits. Each jacking operation required careful analysis of jacking forces and deflections in order to ensure that allowable structural deformations were not exceeded and that load was transferred effectively to the new bearings. Interface compatibility was achieved by injection of an epoxy mortar paste and allowing curing before release of jacking loads. The bearing replacement techniques developed for this project ensured minimal disruption of traffic on one of the busiest routes in Cape Town.
