Investigations on RC Beams Retrofitted with UHSCC Overlay under Fatigue Loading

The present study aims to investigate the use of Ultra High Strength Cementious Composite (UHSCC) overlay strips for strengthening of pre-damaged RC beams. Fatigue loading was conducted in the study, one control beam was tested up to failure. Preloading of 80-90% in terms of number of cycles to failure was applied keeping stress ratio as 0.2 and frequency as 3Hz. Constant amplitude loading spectrum with different maxima minima but keeping stress ratio same was applied to control beam to examine any changes in structural behavior such as deflection and stiffness degradation of beams. The beams used were made of RCC with dimension 1500x100x200mm. The strengthened beams were tested to extract the parameters such as cycles for failure, load, deflection, crack initiation and failure phenomenon. It was observed that the beams retrofitted with UHSCC overlay strips performed efficiently in terms of number cycles to failure in comparison with conventional RCC beams under fatigue loading. Preloaded fatigue beam (FB1) had 17.6% higher load carrying capacity as compared to the control beam. Similarly preloaded fatigue beam (FB2) had 11.7% higher load carrying capacity as compared to the control beam. Acoustic Emission technique is a novel Non-destructive testing method which is used to identify the crack propagation and physical behavior of the beam at selected locations during the onset of loading, which gives a precise idea of the crack initiation and crack propagation under different loading condition.