Damage In Reinforced Concrete Structures Research Articles

Exploring chloride-induced corrosion in reinforced concrete structures through embedded piezo sensor technology: an experimental and numerical study

Corrosion of steel in concrete is one of the major problems with respect to the durability of reinforced concrete (RC) structures. Thus, monitoring the corrosion in real-time is essential to prevent structural damage. However, one of the main challenges is to simulate the real-time development of corrosion in the RC structure. In recent years, smart aggregates, also called embedded piezo sensors (EPS), have become increasingly popular for monitoring localized and corrosion damage in RC structures using electro-mechanical impedance (EMI). This paper presents the experimental and numerical investigation of corrosion in RC structures subjected to the chloride-laden environment using EPS via the EMI technique. To fulfil this objective, the study has been carried out in two stages such as; in the first stage, the experiments are conducted on the RC specimen, and the EMI response was obtained both in a pristine state and when accelerated corrosion progressed. In the second step, a numerical model of the RC specimen has been developed based on the experimental data in the COMSOL software, and the effect of corrosion in the form of varying mass loss percentages has been simulated. Based on the results, it is concluded that the experimental and numerical conductance signatures before and after corrosion are matched. The deterioration in terms of stiffness loss in the RC specimen was 18.20% at 30% mass loss.

A Novel Approach to Discriminate Between Structural and Non‐Structural Post‐Earthquake Damage in RC Structures

In post‐earthquake damage assessment studies of reinforced concrete (RC) buildings, the most important consideration is to determine the damage and severity of structural elements is the determination of the damage and severity of structural elements. For earthquake damage to structural elements, such as columns and shear walls, decisions can be made about strengthening or demolition. However, due to the need for rapid assessment of damaged buildings after earthquakes, these two damage mechanisms can sometimes be confused. Non‐structural damage is classified as structural, leading to uneconomic structural decisions such as demolition or strengthening, or conversely, life safety issues arise from misidentifying critical structural damage with non‐structural damage. In this study, an artificial intelligence‐based damage assessment algorithm has been developed to accurately and quickly differentiate between structural and non‐structural damage. For the damage classification model, a deep learning algorithm was developed using the 9680 damage images obtained from field studies after the recent earthquakes of Mw ≥ 5; Istanbul‐Silivri (Mw: 5.8), Elazığ‐Sivrice (Mw: 6.8) and Izmir‐Seferihisar (Mw: 6.6) in Turkey. With an accuracy rate between 93% and 96%, the models constructed by selecting the optimal values correctly detected and categorised structural and non‐structural element damages in RC structures. The method developed in this study can help experts in damage assessment studies as a decision support mechanism.

Diagnosis of Historic Reinforced Concrete Buildings: A Literature Review of Non-Destructive Testing (NDT) Techniques

Non-destructive testing (NDT) techniques are employed by many authors as reliable and effective methodologies to investigate the current conservation state of historic buildings and to follow up its evolution in response to the surrounding environmental changes. This paper briefly reviews the scientific articles dealing with NDT techniques applied to historic reinforced concrete (RC) buildings. To this purpose, 32 articles were selected through the steps of the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) flow diagram and critically analysed. It emerges that Acoustic Emission and Ultrasonic techniques, Thermography, Rebound Hammer, and Electromagnetic techniques (e.g., Eddy Current and Ground Penetrating radar) are commonly employed due to their ability to detect damage in RC structures. As a result, the combined use of acoustic and mechanical methods (also known as “SonReb” Rebound Hammer and Ultrasonic Pulse Velocity) is found to be the approach more frequently used in the revised documents. This work allows to guide in the selection of NDT techniques to study the rate of decay, if any, and shows the way towards the development of new early warning approaches for historic RC structures.

Degradation of the first frequency of an RC frame with damage levels

Damage in RC structures causes the degradation of stiffness and frequency parameters. In this study, the relationship between the two coefficients and damage severities is numerically investigated considering a three-dimensional (3D) reinforced concrete (RC) frame in which the concrete damage plasticity model (CDPM) and the elastoplastic model are selected to define concrete and reinforcement materials, respectively. Crack propagation of the frame is obtained utilizing a nonlinear static pushover analysis (NSPA). After the pushing procedure, according to the base shear force versus top displacement curve, the bending stiffness of the RC structure is determined rapidly. Thereafter, the degradation of the first frequency is obtained based directly on the nonlinear curve of stiffness. As a result, it is observed that the degradation of the first frequency of the RC frame is proportional to the severity of damage but not linearly. More significant damage, a more profound decrease in the modal characteristic. Particularly, the fundamental frequency of the RC frame reduces gradually until the base shear force reaches 70% of the ultimate value at which the parameter is about 60% of the counterpart at the intact stage. After that, the reduction gets more significant when the bending capacity approaches the ultimate value.

Classification of Corrosion Severity in Concrete Structures Using Ultrasonic Imaging and Linear Discriminant Analysis

The deterioration of concrete structures due to rebar corrosion is a key issue affecting the safety and service life of civil infrastructure. Reinforced concrete (RC) structures in coastal areas are subjected to harsh environmental conditions that cause rebar corrosion. From the perspective of safety, repair, and structural rehabilitation, it is essential to ascertain the level of corrosion severity and associated damage in RC structures through non-destructive evaluation (NDE) techniques. In this study, the potential of pattern recognition techniques for ascertaining the severity damage at various stages of rebar corrosion in concrete samples was explored. A contact ultrasonic compressional wave transducer pair with 250 kHz centre frequency was used as source and reflected signals from the rebar were acquired using a tied-together scanning approach. To expedite the corrosion process in the laboratory, accelerated corrosion of the embedded rebar was employed. The synthetic aperture focusing technique (SAFT) was applied to reconstruct the image of the concrete subsurface from the acquired B-scans. Two approaches, i.e., the Mahalanobis distance (MD) and linear discriminant analysis (LDA), were adopted; both methods correctly classified the level of corrosion severity and damage to the concrete. The developed pattern recognition techniques can, therefore, be potential tools for generating important information towards economical and timely repair of damaged concrete structures affected by rebar corrosion.

Steel corrosion damage monitoring in reinforced concrete structures with the acoustic emission technique: A review

• An in‐depth literature review and discussion on AE‐based corrosion monitoring in RC is presented. • Consistency of parameter‐ and signal‐based AE methods for corrosion monitoring is analyzed. • AE‐based condition assessment of corroded RC elements during load testing is discussed. • An overview on availability of AE data sets for corrosion tests in lab and in‐situ is presented. • Research challenges for in‐situ monitoring of corrosion damage in RC structures are discussed. Corrosion is a major issue in construction and infrastructure management, giving rise to high repair costs, safety concerns and structural failures. Especially reinforcement corrosion in concrete structures is a complex issue. As degradation starts internally, visual inspection lacks efficiency in early stages of the corrosion process. Acoustic Emission (AE) monitoring provides major advantages as this technique enables to detect internal damage in an early stage. However, the use of AE monitoring also comes with certain challenges. The aim of this paper is to review appropriate protocols for AE-based reinforced concrete (RC) corrosion monitoring based on an overview of reported lab experiments, highlighting challenges and pitfalls, and to provide a solid basis for extension of the research focus towards on-site AE-based corrosion monitoring in RC structures. Therefore, this paper firstly discusses AE monitoring during (accelerated) corrosion tests, including methods for data analysis and best-practice protocols. Secondly, application of the AE technique for condition assessment of corroded RC elements during load testing is discussed. Thirdly, an overview is presented of reported on-site AE monitoring studies on corroding RC structures. The paper concludes with a discussion and future research challenges, especially towards on-site monitoring of existing RC structures.

Multifractal-spectrum shape parameters for characterizing distribution and evolution of multiple cracks in concrete structures

The evolution of cracks in reinforced concrete (RC) structures may trigger critical failure modes of the entire structure. In order to adequately assess the damage in RC structures, it is essential to characterize the distribution and evolution of cracks. Compared with existing quantitative methods of describing concrete cracks, multifractal analysis (MUTFA) is an emerging and sophisticated tool for characterizing the complexity and irregularity of crack distributions in RC structures. Despite the fact that MUTFA embodies a greater capability than monofractal analysis (MONFA), the uncertainty of the mechanism of the multifractal spectrum for representing concrete cracks is a major limitation in using MUTFA to depict cracks. To address this drawback, this study illustrates the difference between the features of MUTFA and MONFA as well as proposes a multifractal-spectrum shape parameter to characterize the complexity and irregularity of fractal-like cracks. The advantages of MUTFA in portraying concrete cracks are demonstrated in two typical cracking scenarios of concrete structures, namely, crack distributions in shear-controlled concrete beams and crack patterns in thin and lightly-reinforced concrete walls. The results of the study show that the proposed multifractal-spectrum shape parameter offsets the deficiency of traditional multifractal parameters in revealing the heterogeneity of crack distributions. The results demonstrate that MUTFA is competent in distinguishing the subtle differences between two similar distributions of concrete cracks, and it provides a path to assess damage in concrete structures.

Non-Destructive testing to detect multiple cracks in reinforced concrete beam using electromechanical impedance technique

One of the most common engineering constructions is the Reinforced Concrete (RC) structure. As a result, it's critical to monitor the structure's health constantly. Significant causes of damage in RC structures are overloading, deficient design, fatigue; these factors induce cracks. These induced cracks severely impact the capacity of RC structures. It's critical to surveil the existence and progression of cracks early on in the damage cycle to prevent catastrophic structural failure. Electromechanical Impedance (EMI) is an effective non-destructive testing technique that uses smart materials-based Lead Zirconate Titanate (PZT) to detect cracks. The EMI technique generates admittance ((Y)) ̅ comprising of conductance, G and susceptance, B. The structure's diagnosis of damage signature is a plot of G over a frequency range. Any variation in the plot of G indicates damage in the structure. The proposed method is experimentally validated using surface-bonded PZTs on the lab-sized RC beam of grade M25. Two PZTs are bonded near each support, with one in the RC beam's centre. The RC beam is put through a four-point bending test in the experiment. Shear and flexural cracks in the beam have been monitored continuously by extracting admittance signatures from the surface bonded PZTs using an LCR meter. The admittance signatures measured at the pristine and damaged stage are compared to locate the damages. The lateral and vertical shifts in conductance signatures indicated cracks in the beam. RMSD and MAPD are used as pattern recognition techniques to quantify the variations of damaged signatures with undamaged signatures of the host structure. It demonstrates that EMI method based on PZT transducers have the ability to detect the shear and flexural cracks of the beam, and the pattern recognition techniques can effectively quantify the damage levels. The proposed method of damage detection is quite effective and sensitive to concrete.

Nonlinear ultrasonics-based technique for monitoring damage progression in reinforced concrete structures

In reinforced concrete (RC), material nonlinearity is evident even in its undamaged state due to the inherent microstructure. In the present work, damage progression in RC structure at different levels of damage is investigated using linear and nonlinear ultrasonic techniques. The primary focus of this study is to monitor the structure from its initiation stage(s) of damage to advanced stages. Ultrasonic velocity tomography is first implemented to identify the weaker regions and map any damage occurring at various levels of loading. Two critical regions are identified from ultrasonic tomography and further damage characterization is carried out using various ultrasonic techniques to quantitatively assess the progression of damage in these two regions. The linear ultrasonic techniques such as time-of-flight (TOF) and attenuation, and the nonlinear ultrasonic techniques such as sub- and super- harmonic, energy distribution, etc. are employed to detect the damage progression. It is found that the changes in linear parameters due to damage progression in RC structure are often insignificant and inconsistent. However, some of the nonlinear ultrasonics-based techniques are found to be very efficient to monitor the damage progression. A relatively new and promising nonlinear ultrasonic technique, namely the sideband peak count-index (or SPC-I) provides a very clear and consistent indication of damage at the early stage. The present study shows that during the initial stages of damage, SPC-I based nonlinear technique performs significantly better (at both regions as identified through ultrasonic tomography) than other linear and nonlinear techniques, whereas at higher damage stage the superiority of this nonlinear ultrasonic technique slowly diminishes. The present study also shows that out of all nonlinear ultrasonics-based techniques considered here, SPC-I technique provides the highest sensitivity to the damage progression and can be effectively used as a very robust nonlinear ultrasonic tool for identifying the onset and progression of damage in RC structures.

24 January 2020 Sivrice (Elazığ) earthquake damages and determination of earthquake parameters in the region

The 24 January 2020 (Mw=6.8) earthquake with epicentre in Elazig (Sivrice) on the East Anatolian Fault Zone caused loss of life and property. The information was given about the seismotectonic setting and regional seismicity along this fault zone and aftershock activity and ground motion data of this earthquake. Earthquake parameters were obtained for five different earthquake stations which were closer to the epicentre. Horizontal and vertical design spectra were obtained for the geographic locations for each earthquake station. The obtained spectra for the earthquake epicentre were compared with selected appropriate attenuation relationships. The damages after earthquake were evaluated via geotechnical and structural aspects. This study also aims to investigate the cause-effect relationships between structural damage in reinforced-concrete and masonry structures, respectively. The lack of engineering services was effective on the amount of damage in masonry structures. Insufficient reinforcement and concrete strength, dimensions and inadequate detailing increased the amount of damage in reinforced-concrete structures. Importance should be given to negative parameters that may weaken the defence mechanisms of structures for earthquake-resistant structural design.

Shear Failure Capacity Prediction of Concrete Beam–Column Joints in Terms of ANFIS and GMDH

Vulnerability assessment of structures in an earthquake is one of the most important topics in structural engineering. HAZUS instruction is the code widely used for assessment of structures for satisfied damage based on the interstory drift. In a structure, there are several parameters, such as forces and responses in elements, which cause damage to the structure simultaneity, and therefore, the use of only one parameter, such as interstory drift, could be unrealistic. In this paper, reinforced concrete (RC) beam–column joints are studied, with the aim of determining the maximum shear capacity of RC joints as a key parameter in the damage of RC structures. For this purpose, two strong approaches, including group method of data handling (GMDH) and adaptive neuro-fuzzy inference system (ANFIS), were used. The selected models were created based on a large experimental database. The results indicated that the considered methods are capable of determining the shear capacity of RC joints with high accuracy.

Determination of yielding point by means a probabilistic method on acoustic emission signals for application to health monitoring of reinforced concrete structures

Reinforced concrete (RC) flanged beam specimens were tested under incremental cyclic load till failure in flexure, and simultaneously, the acoustic emission (AE) signals released by the specimens were recorded. To assess damage in RC structures, a previously published index of damage (ID) based on AE signals was used. This index, however, needs to know the yielding point of the specimen. In the present study, yielding point was identified with a probabilistic method known as Gaussian mixture modeling (GMM) applied to the AE signals, as compared with that obtained by means of the plastic strain energy. It was observed that yielding load obtained with both methodologies was almost same, thus validating the GMM method. This result permits to use the ID index for damage monitoring of RC structure in practical scenarios, by using only information hidden in the AE signals. The influence of loading rate, failure type (tensile and shear), RC beam depth, concrete compressive strength, and percentage of tensile steel reinforcement on ID were studied in this work.

Prognosis of low-strain fatigue induced damage in reinforced concrete structures using embedded piezo-transducers

Fatigue induced damage under low-strain conditions is a commonly encountered phenomenon in reinforced concrete (RC) structures subjected to continuous vibrations, such as bridges under vehicular loads, buildings under wind and structures directly supporting or in the vicinity of vibration emitting machinery. This type of fatigue tends to weaken the structure silently, and quite often, its timely cognizance is missed out in the life-cycle management of the structure. Among the various structural health monitoring (SHM) frontiers, very scarce research has been devoted to this kind of damage in RC structures. This paper covers a long-term experimental study related to low-strain fatigue damage monitoring encompassing a real-life sized RC structure. The experimental specimen was subjected to over eight million cycles of flexural loading with the maximum bending strain values restricted to 50 µm/m. The structure was instrumented with piezo-based composite concrete vibration sensors (CVS), which were embedded inside the beam near the surface. The CVS operated in dual mode, acting as sensor for the global vibration technique as well as the local electro-mechanical impedance (EMI) technique. As EMI sensors, they facilitated the determination of the equivalent stiffness parameter (ESP), and were found to be very expedient for damage detection as well as localization during the incipient stages of fatigue damage, coinciding with the appearance of first few cracks. The ESP served to represent the diminishing trend to actual residual stiffness fairly well during the initial stages. Acting in the global mode, determination of the overall stiffness of the structure by the same CVS provided an alternate damage measure, in terms of a realistic estimate of the overall residual flexural stiffness. This proved useful parameter during moderate to severe damage conditions, and in particular near the final failure of the structure. The monitoring paradigms presented in the paper pave way for effective prognosis of fatigue induced damage in real-life RC structures.

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 damage monitoring 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.

Damage limit states of reinforced concrete beams subjected to incremental cyclic loading using relaxation ratio analysis of AE parameters

This paper presents an experimental study on damage assessment of reinforced concrete (RC) beams subjected to incremental cyclic loading. During testing acoustic emissions (AEs) were recorded. The analysis of the AE released was carried out by using parameters relaxation ratio, load ratio and calm ratio. Digital image correlation (DIC) technique and tracking with available MATLAB program were used to measure the displacement and surface strains in concrete. Earlier researchers classified the damage in RC beams using Kaiser effect, crack mouth opening displacement and proposed a standard. In general (or in practical situations), multiple cracks occur in reinforced concrete beams. In the present study damage assessment in RC beams was studied according to different limit states specified by the code of practice IS-456:2000 and AE technique. Based on the two ratios namely load ratio and calm ratio and when the deflection reached approximately 85% of the maximum allowable deflection it was observed that the RC beams were heavily damaged. The combination of AE and DIC techniques has the potential to provide the state of damage in RC structures.