Title: Fatigue of Reinforced Concrete in Sea Water
Author(s): W. S. Paterson
Publication: Symposium Paper
Appears on pages(s): 419-436
Keywords: beams (supports); crack width and spacing; cyclic loads; fatigue (materials); fatigue tests; loads (forces); reinforced concrete; sea water.
Tests have been carried out to determine the fatigue life of Torbar cold worked reinforcement in concrete beams in a seawater environment at a loading frequency of 0.1 Hz (near wave frequency) and also at 3.0 Hz so that long endurance tests at low stress ranges could be accomplished within a reasonable time scale. The adoption of a mechanical loading system offered a considerable saving in construction and running costs of the rigs compared with conventional servo-hydraulic systems. It also simplified the arrangements for tests at a simulated water depth of 30m which were performed in a purpose made pressure chamber. The results have indicated that the fatigue life of Torbar in seawater is lower than in air when the test duration is greater than 1 to 2 months when the conditions exist for a fatigue crack to initiate at a corrosion site. A significant feature of the research was that the beams exhibited the phenomenon of 'cyclic stiffening' resulting from a build up of deposits in the cracks in the concrete. This caused a progressive reduction in the deflection range, the applied load range remaining unchanged. While the stress range in the Torbar was correspondingly reduced, corrosion was not inhibited.