A parallel between earthquake sequences and acoustic emissions released during fracture process in reinforced concrete structures under flexural loading

• Influences of different factors on relaxation ratio of acoustic emission signals related to reinforced concrete were presented.
• Relaxation ratio analysis of AE released during reinforced concrete was discussed in detailed.
• AE based b-value analysis was studied for different reinforced concrete beams.

This article reports on the influence of (i) concrete compressive strength (ii) specimen geometry (iii) change in rate of loading (iv) percentage of steel reinforcement [area of steel reinforcement as a percentage of the effective area of reinforced concrete (RC) structural member’s cross section] (v) mode of failure on the relaxation ratio parameter (Colombo et al., 2005a, 2005b) of acoustic emissions (AE) released during fracture process in reinforced concrete (RC) flanged beam specimens. The aim is to study the feasibility of relaxation ratio analysis of AE signals for damage assessment in RC beams. The beam specimens were tested in the laboratory under incremental cyclic loading. The loading cycle first entered into the relaxation dominant phase in the relaxation ratio plot was equal or close to the loading cycle entering first into the heavy damage zone in the NDIS-2421 damage assessment plot proposed by Japanese society for nondestructive inspection. Further, the lowest AE based b-value was observed at the same or nearer loading cycle. Relaxation ratio analysis of AE signals is a useful method to assess the current load carrying capacity of a structure and state of damage in concrete structures in-situ.