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Cyclic Bond Testing of Steel Bars in High-Performance Underwater Concrete

Abstract A limited number of investigations have been carried out to assess the cyclic bond behaviour of reinforcing steel bars in underwater concrete (UWC). An experimental campaign with 57 pull-out specimens was undertaken, testing one mixture previously developed and characterized to be used in a cable-stayed bridge project. Half of the specimens were cast in underwater conditions using construction equipment to replicate real on-site conditions, while the other half were cast in dry conditions to be used as reference samples. Two different cyclic load ranges were tested in conjunction with a varying number of cycles, including reference monotonic (static) loading tests. Test results show the influence that the different test parameters such as load cycle amplitude, maximum load and number of cycles have on UWC bond behaviour, as well as the comparison between underwater cast specimens and dry cast samples. An average bond reduction of 8% is found in the underwater samples not subjected to previous cyclic loading compared with dry cast samples. This reduction decreases to 6% when the specimens were previously subjected to cyclic loading. An average increase of 31% in the slip was found in the underwater samples subjected only to static load and 3% in the specimens with previous cyclic load. The adjustment of slip behaviour to one existing theoretical model shows good correlation.