Acoustic emission techniques for the damage assessment of reinforced concrete structures

This thesis examines the role of Acoustic Emission (AE) techniques as a nondestructive testing (NDT) technique for reinforced concrete structures. The work focuses on the development of experimental techniques and data analysis methods for the detection, location and assessment of AE from the reinforced concrete specimens. Three key topics are investigated: 1. Method of analysis for laboratory-based pre-corroded and postcorroded reinforced concrete specimens tested in flexure. Experimental results from a series of laboratory studies are presented. The work investigates the changing behaviour of the reinforced concrete beams due to chloride-induced reinforcement corrosion by using a parameter-based approach to detect, locate and follow the progression of cracks. The use of AE absolute energy as an indication of concrete cracking is also explored. 2. A practical investigation into acoustic wave propagation in reinforced concrete structures. Experimental results from acoustic wave propagation of two source modes (parallel and normal to sensor face) are presented. The work investigates the wave velocity in concrete structures over a variety of source-to-sensor distances with the influence of pre-set threshold levels. Specimen geometry, specimen conditions and source orientation is explained. The application of modal behaviour on the AE from both artificial and real sources is examined. Experimental data describing signal attenuation is also presented. 3. The detection of damage within an in-service concrete crosshead. Further analysis of a commercial bridge inspection is given. A comparison of results from both clustered and non-clustered events, with laboratory based results is made. Apart from being interested with clustered events, nonclustered events are also an important contribution to damage detection in structural monitoring

Damage Source Identification of Reinforced Concrete Structure Using Acoustic Emission Technique

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damagemonitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE.The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures

Analysis of failure mechanisms in fatigue test of reinforced concrete beam utilizing acoustic emission

The acoustic emission technique is used for monitoring the fatigue failure mechanisms in reinforced concrete beam under three point bending. The analysis was conducted by using the bathtub curve method plotted from acoustic emission data. In this study, the fatigue behavior was divided into three stages. The first stage is involved with the decreasing failure rate, known as early life failure or burn-in phase, the second stage is characterized by constant failure rate and the third stage is called the burnout phase which is an increase of failure rate. The three parameters used in analyzing is the fatigue behavior for each stage of failure which are severity, signal strength and the cumulative signal strength. From severity analysis, the range of each stage of failure had been determined while from signal strength analysis, the initiation of distribution of crack had been detected through the fluctuation of signal strength. Cumulative signal strength parameter provides a clearer view of the initiation and distribution of crack

Damage classification in reinforced concrete beam by acoustic emission signal analysis

Acoustic Emission (AE) is a non-destructive testing technique which can be used to identify both the damage level and the nature of that damage such as tensile cracks and shear movements at critical zones within a structure. In this work, the acoustic emission parameters of amplitude, rise time, average frequency and signal strength were used to classify the damage and to determine the damage level. Laboratory experiments were performed on a beam (150 x 250 x 1900 mm). The acoustic emission analysis was successfully used to determine crack movements and classify damage levels in accordance with the observations made during an increasing loading cycle

Fatigue Crack Inspection and Acoustic Emission Characteristics of Precast RC Beam under Repetition Loading

Abstract. Fatigue crack of the precast reinforced concrete beam under repetition loading is vital to be examined. Reinforced concrete structures exposed to excessive repetition loading could lead to the failure of the structures. In order to examine the active fatigue crack, the reinforced concrete beams were subjected to three-point repetition maximum loading. Eight phases of maximum fatigue loading with sinusoidal wave, frequency of 1 Hz and 5000 cycles for each phase were performed on the reinforced concrete beams. The inspection was carried out with visual observation of the crack pattern and acoustic emission technique for each load phase. The signal strength of acoustic emission was investigated. It is found that the signal strength of acoustic emission and crack pattern of the reinforced concrete beam subjected to repetition loadings showed promising results for structural health monitoring

Fracture Formation Evaluation of Reinforced Concrete Beam Subjected to Cycle Loading Using Acoustic Emission Technique

Abstract. Acoustic emission (AE) technique is one of the non-destructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. In present study, AE technique with a new approach was employed to investigate the process of fracture formation in reinforced concrete (RC) structure. Thirty RC beam specimens with continuous and non-continuous longitudinal rebar were prepared. The RC beams were tested under loading cycle and were simultaneously monitored using AE. The AE test data was analyzed using Relaxation, Load and Calm ratio. The trend of these methods during loading and unloading was compared with behaviour of each type of specimens. The trend of Relaxation ratio and Calm and Load ratio method during loading and unloading showed that these methods are strongly sensitive with cracks growth in RC beam specimens and were able to indicate the levels of damage. Also, results showed that AE can be considered as a viable method to predict the remaining service life of reinforced concrete. In addition, with respects to the results obtained from Relaxation, Load and Calm ratio indicated, a new chart is proposed

Failure mode maps of bio-inspired sandwich beams under repeated low-velocity impact

Existing sandwich structures failure maps are confined only to data from the quasi-static bending tests even for describing failure modes due to the impact event. Strengths of the constituent layers, which are not well-described by these maps, can reasonably change especially under the repeated impact load case. Hence, a new series of more realistic failure mode maps have been developed from the experimentally and numerically obtained observations on recently proposed bio-inspired dual-core sandwich beams in the presence of repeated low-velocity impacts of different energy levels. The beams consist of top and bottom carbon fiber reinforced polymer skins sandwiching the rubber and aluminum honeycomb cores. Departing from the modified Gibson model, an actual presentation of skin and core behaviors has been modeled following the trend of strengths variations for the construction of the failure mode maps when subjected to numerous impact numbers and energies. The produced maps offer the flexibility to accommodate the changes in strengths due to deterioration or densification of constituent layers after impact, and hence following more favorably the physical failure description of the sandwich beams. Accompanying these maps, a general set of mathematical expressions have also been produced for practical convenience. It is found that the failures from observations are within the proposed map boundaries with accuracies ranging from 85.7% to 100%. © 2019 Elsevier Lt

The use of acoustic emission for the early detection of cracking in concrete structures

Acoustic emission testing of concrete structures shows great potential for monitoring and assessing their condition. The aim of this paper is to relate the AE obtained from reinforced concrete beams to the onset of cracking of these beams subjected to the four-point bending test. A pre-corroded test specimen was used where the cross-sectional area of the bar was reduced but, as they were cleaned before being cast into the concrete, the integrity of the concrete itself and the bond between the steel and the concrete were unaffected by the corrosion. This paper explores the capability of acoustic emission that can be used to obtain a warning of developing distress and the growth of internal microcracking at critical locations before the crack is visible on the surface. In addition, a comparison between visual observations of the cracking process and acoustic emission source location analysis indicates that areas of damage owing to cracking can be clearly identified by acoustic emission source location