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Title: Health Monitoring of GFRP Repaired Reinforced Concrete and Steel Fiber Reinforced Concrete Beams using Acoustic Emission Technique
Authors: Goyal, Priya
Supervisor: Kwatra, Naveen
Sharma, Shruti
Keywords: Health Monitoring;Reinforced Concrete Beam;Steel Fiber Reinforced Concrete Beams;Acoustic Emission Technique;Corrosion
Issue Date: 10-Nov-2022
Abstract: The vulnerability of concrete and reinforced concrete structures induced by deterioration and corrosion over a period of time makes it essential to continuously monitor these kind of structures. Damage monitoring becomes important for the purpose of further suggesting repair and retrofitting strategy for the structures for their sustenance over a longer period of time. Nowadays, numerous techniques have made it feasible to study and examine the behavior and damage characteristics of these structures by means of non-destructive testing techniques which are favorable as against destructive testing. Out of the various NDT techniques, AE has proven to be successful for real time diagnosis of damage in different kinds of structures including reinforced concrete (RC) structures. An attempt has been made in this research effort to utilize, Acoustic Emission (AE) Technique effectively to monitor damage in RC and steel fiber reinforced beams (SFRB) subjected to half cyclic load at various stages of initiation and progression of damage. Half cyclic load is applied with increasing loading levels, and an increment of 5 kN, is given at each load cycle. Further the damaged RC and SFRB beams repaired with GFRP (Glass Fiber Reinforced Concrete) wrapping are monitored using AE Technique when subjected to half cyclic loading to understand the variation in their damage mechanisms and prove the effectiveness of Acoustic Emission in predicting the damage progression after repairing. It was found that Acoustic Emission Technique is effective in monitoring damage initiation and progression in RC and SFRB beams when subjected to half cyclic loading. Additionally, in GFRP repaired RC and SFRB beams, fewer AE events & less release of AE energy due to pre-cracked condition of the beams clearly indicated efficacy of AE Technique in monitoring the damage after repair. The decrease in total acoustic energy for the repaired beams is approximately one-third to that of control RC beams. In case of SFRB beams the decrease in total acoustic energy for the repaired beam is approximately half to that of control SFRB beams. For the practical implementation of AE Technique, an attempt has been made to establish the procedure for developing an empirical equation between AE parameter of AE energy and damage indices with Genetic Programming tool. It was perceived from predicted GP model that Acoustic Emission technique can be used to fairly predict damage level in Reinforced Concrete and Steel Fiber Reinforced Concrete beams. Further AE technique is used to investigate the initiation and progression of corrosion induced damage in RC and SFRB beams and further when these beams are subjected to simultaneous corrosion and sustained load. It is observed that AE parameters effectively map the onset and initiation of corrosion in early ages in both kinds of beams. SFRB beams sustained the corrosion for longer duration (72 days as against 42 days in RCB) probably due to presence of steel fibres that bind concrete together and inhibit the distribution of corrosion cracking. Variation in number of AE hits and corresponding release in AE energy under simultaneous sustained load and corrosion exposure demonstrated various stages of damage initiation and progression (micro and macro-cracking), hence, proving its effectiveness as a corrosion monitoring indicator in real-life situations. AE activity in the form of cumulative AE hits increased by about 2.3 times in SFRB beams under simultaneous corrosion and sustained load as compared to when the beams are subjected to only corrosion. The increase in cumulative AE hits in RCB beams is 5 times under simultaneous corrosion and sustained load when compared to beams under corrosion only. Also, on comparison of cumulative AE energy parameter, the total energy release of 0.8 x 1010 mV-sec is seen in 16 days in RC beam as against 72 days in SFRB beam under simultaneous corrosion and sustained load. Thereby showing the effectiveness of acoustic emission monitoring for both kinds of beams. The AE parameters of Rise Angle (RA) and Average Frequency (AF) is also found effective in identifying the mode of cracking in RC and SFRB beams with corrosion and sustained loading. Moreover, it was also found that Improved b-value being sensitive to the generation of cracks due to corrosion, can be used to demonstrate the damage level in RC structural members. It is observed from this study that acoustic emission technique can effectively be used to track the damage and predict the damage level in reinforced concrete and steel fiber reinforced concrete beams. Moreover, AE also proved to be effective in predicting the damage progression in both RC and SFRB beams after repair. Furthermore, the AE Technique is also found to be effective in monitoring the behaviour of RCB and SFRB beams subjected to only corrosion and then simultaneous corrosion exposure and sustained load. Therefore, this would go a long way in non-destructive evaluation of structures, which would help a great deal in devising a maintenance strategy of these structures.
Appears in Collections:Doctoral Theses@CED

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