Structural retrofitting of a simply supported reinforced concrete beam using turnbuckle type of exterior post tensioning method

Due to long term environmental exposure and excessive loading experienced by aging structures, the structural performance of reinforced concrete members are affected whereas RC beams deflect in time compromising the flexural performance and serviceability of the structure. Instead of demolishing structures considered to have poor performance, a turnbuckle type of exterior post tensioning system would be used as a retrofitting method in order to resolve the structural, environmental and cost problems. The turnbuckle exterior port tensioning (T-EPT) makes use of a turnbuckle mechanism to provide pre-stressing force to a flexural member. An experimental method was designed in order to determine the effectiveness of the T-EPT in terms of retrofitting RC beams back into its original condition and further increase its load carrying capacity. The experimental results proved that the effectiveness of applying the T-EPT depends on the elastic condition of RC beams. The T-EPT was effective in retrofitting RC beams deflected until the elastic range however, for beams deflected up to the inelastic range, the turnbuckle mechanism only provided 15% decrease in permanent deformation. Even if the inelastic RC beams were not brought back to its original condition (zero deflection), the pre-stressing force applied by the T-EPT increased up to 40% of load carrying capacity for the elastic range and up to 27% for the inelastic range. Based on the experiment made, recommendations were obtained to further improve some procedures in testing the T-EPT