Sub-Frequency Interval Approach in Electromechanical Impedance Technique for Concrete Structure Health Monitoring

The electromechanical (EM) impedance technique using piezoelectric lead zirconate titanate (PZT) transducers for structural health monitoring (SHM) has attracted considerable attention in various engineering fields. In the conventional EM impedance technique, the EM admittance of a PZT transducer is used as a damage indicator. Statistical analysis methods such as root mean square deviation (RMSD) have been employed to associate the damage level with the changes in the EM admittance signatures, but it is difficult to determine the location of damage using such methods. This paper proposes a new approach by dividing the large frequency (30–400 kHz) range into sub-frequency intervals and calculating their respective RMSD values. The RMSD of the sub-frequency intervals (RMSD-S) will be used to study the severity and location of damage. An experiment is carried out on a real size concrete structure subjected to artificial damage. It is observed that damage close to the PZT changes the high frequency range RMSD-S significantly, while the damage far away from the PZT changes the RMSD-S in the low frequency range significantly. The relationship between the frequency range and the PZT sensing region is also presented. Finally, a damage identification scheme is proposed to estimate the location and severity of damage in concrete structures

Application of machine learning with impedance based techniques for structural health monitoring of civil infrastructure

Increased attentiveness on the environmental and effects of aging, deterioration and extreme events on civil infrastructure has created the need for more advanced damage detection tools and structural health monitoring (SHM). Today, these tasks are performed by signal processing, visual inspection techniques along with traditional well known impedance based health monitoring EMI technique. New research areas have been explored that improves damage detection at incipient stage and when the damage is substantial. Addressing these issues at early age prevents catastrophe situation for the safety of human lives. To improve the existing damage detection newly developed techniques in conjugation with EMI innovative new sensors, signal processing and soft computing techniques are discussed in details this paper. The advanced techniques (soft computing, signal processing, visual based, embedded IOT) are employed as a global method in prediction, to identify, locate, optimize, the damage area and deterioration. The amount and severity, multiple cracks on civil infrastructure like concrete and RC structures (beams and bridges) using above techniques along with EMI technique and use of PZT transducer. In addition to survey advanced innovative signal processing, machine learning techniques civil infrastructure connected to IOT that can make infrastructure smart and increases its efficiency that is aimed at socioeconomic, environmental and sustainable development

Electromechanical Impedance-based Techniques for Structural Health Monitoring

New developments on electromechanical impedance (EMI) based structure health monitoring techniques are presented in this thesis. Time frequency auto-regressive moving average (TFARMA) model based damage indicator is developed to enhance the sensitivity of EMI based method for structural damage detection. An innovative approach by using impedance sensitivity-based model updating and sparse regularization techniques is developed for structural damage localization and quantification. Numerical and experimental studies are conducted to verify the performance of the proposed approaches

Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

Characterization of concrete materials using non-destructive wave-propagation testing techniques

Non-destructive testing (NDT) of concrete members has been widely used for characterisation of material and assessment of functional structures without impairing their functions and performances. This thesis focuses on addressing critical challenges related to the practical implementation of NDT techniques based on wave-propagation approaches for characterisation of concrete members used in civil infrastructures. Specially, this research aims to achieve three interdependent objectives related to developing NDT techniques with piezoceramic-based transducers: monitoring of very early-age concrete hydration process, detection, and monitoring of cracking in concrete members of different complexity under loading. The concept of piezoceramic-based Smart Aggregate (SA) transducers is central to this research. Embedded SA transducers with an active sensing method have shown great potential for characterisation of construction materials such as concrete and concrete-steel composites. Based on the developed SA based approaches, an active sensing approach with appropriate arrangement of SAs in and on concrete members, and analysis of the received signal using the power spectral density, total received power and damage indexes is developed and applied in this thesis. To confirm its applicability for characterisation of very early-age concrete, a systematic investigation is performed into concrete specimens with different values of water-to-cement ratio due to slightly different initial water amounts, and different separation distances between the embedded SAs. For the detection and monitoring of cracking in concrete members under loading the mounted SA based approach is proposed and applied. It is shown that NDT systems, based on this approach, provide detection and monitoring of cracking in a variety of concrete members under loading, including relatively simple concrete beams and reinforced concrete beams under bending, and reinforced concrete slab as a part of a complex composite member under cyclic loading. Comparisons are provided between the proposed system and conventional load cell and strain gauge systems with each tested member

Novel Approaches for Structural Health Monitoring

The thirty-plus years of progress in the field of structural health monitoring (SHM) have left a paramount impact on our everyday lives. Be it for the monitoring of fixed- and rotary-wing aircrafts, for the preservation of the cultural and architectural heritage, or for the predictive maintenance of long-span bridges or wind farms, SHM has shaped the framework of many engineering fields. Given the current state of quantitative and principled methodologies, it is nowadays possible to rapidly and consistently evaluate the structural safety of industrial machines, modern concrete buildings, historical masonry complexes, etc., to test their capability and to serve their intended purpose. However, old unsolved problematics as well as new challenges exist. Furthermore, unprecedented conditions, such as stricter safety requirements and ageing civil infrastructure, pose new challenges for confrontation. Therefore, this Special Issue gathers the main contributions of academics and practitioners in civil, aerospace, and mechanical engineering to provide a common ground for structural health monitoring in dealing with old and new aspects of this ever-growing research field

Structural health monitoring of offshore wind turbines: A review through the Statistical Pattern Recognition Paradigm

Offshore Wind has become the most profitable renewable energy source due to the remarkable development it has experienced in Europe over the last decade. In this paper, a review of Structural Health Monitoring Systems (SHMS) for offshore wind turbines (OWT) has been carried out considering the topic as a Statistical Pattern Recognition problem. Therefore, each one of the stages of this paradigm has been reviewed focusing on OWT application. These stages are: Operational Evaluation; Data Acquisition, Normalization and Cleansing; Feature Extraction and Information Condensation; and Statistical Model Development. It is expected that optimizing each stage, SHMS can contribute to the development of efficient Condition-Based Maintenance Strategies. Optimizing this strategy will help reduce labor costs of OWTs׳ inspection, avoid unnecessary maintenance, identify design weaknesses before failure, improve the availability of power production while preventing wind turbines׳ overloading, therefore, maximizing the investments׳ return. In the forthcoming years, a growing interest in SHM technologies for OWT is expected, enhancing the potential of offshore wind farm deployments further offshore. Increasing efficiency in operational management will contribute towards achieving UK׳s 2020 and 2050 targets, through ultimately reducing the Levelised Cost of Energy (LCOE)

Structural Health Monitoring of Laminate Structures Using Shear-Mode Piezoelectric Sensors

Structural health monitoring (SHM) employing embedded piezoelectric transducers has shown potential as a promising solution for inspection of different engineering structures such as aircraft, bridges, and renewable energy structures. Despite advancements in the field of ultrasonic SHM, inspection of laminate structures is still a major challenge due to their susceptibility to various joint defects. This thesis presents a novel approach to tackle the challenge of inspecting laminate structures using shear-mode (d35) piezoelectric transducers that are made of lead zirconate titanate (PZT). This study begins with the characterization of d35 piezoelectric transducers using analytical, numerical, and experimental approaches. The results were found to match well. A finite element (FE) simulation of a laminate structure was developed based on multiphysics analysis to identify the propagating waves generated by d35 PZT actuators embedded within the bondline of the laminate structure. The group velocities of voltage signals as well as the distributions of normal displacements and stresses induced by the propagating waves showed that the elastic waves generated by the d35 PZT actuator exhibit the characteristics of antisymmetric (flexural) waves coupled with strong transverse shear stress across the thickness of the adhesive layer. The FE results were validated by testing laminate specimens with bondline-embedded d35 PZTs in a pitch-catch arrangement. A parametric study was performed to provide design guidelines for d35 PZT sensors and actuators. The thickness and length of d35 PZT transducers were varied while monitoring the actuation strength and the sensed voltage signal. It was found that thicker and shorter d35 PZT sensors can produce stronger signals compared to thinner and longer d35 PZT sensors. On the contrary, d35 PZT actuators were noticed to exhibit the opposite response to d35 PZT sensors. The selectivity of d35 PZT sensors was also investigated in multiphysics simulations by comparing voltage signals obtained from a bondline-embedded d35 PZT sensor and a surface-mounted conventional (d31) PZT sensor. It was found that d35 PZTs offer a selective hardware filter that primarily captures antisymmetric wave modes in the laminate structure while suppressing symmetric wave modes. Filtering symmetric modes significantly reduced the complexity of signal processing and this could potentially enhance the process of SHM as well. Various joint defects including disbonds, cracks, and voids were introduced in the bondline of laminate structures to investigate the feasibility of embedding d35 PZT transducers in the bondline of laminate structures for detection of joint defects. It was observed that antisymmetric waves generated by d35 PZT actuators exhibited strong interaction with joint defects especially nonlinear defects such as cracks and disbonds. By placing the transducers within the bondline and at the neutral axis of the laminate structure, it provided a direct strong coupling between the bondline and the d35 PZT transducers resulting in high transmission and sensitivity of flexural waves to joint defects. Several specimens were prepared and tested. The results obtained from experiments and simulations were found in good agreement. The proposed approach was also evaluated experimentally for health monitoring of bondline integrity. A laminate specimen with bondline-embedded d35 PZT and surface-mounted d31 PZT piezoelectric transducers was subjected to a three-point bending test to create joint defects. Damage indices were implemented to detect the presence of damage and its severity. The experimental results demonstrate the ability of bondline-embedded d35 PZTs to be used as sensors and actuators for ultrasonic SHM of bondline integrity. The proposed approach successfully produced promising results for detection of joint defects that often impose a significant challenge to detect using conventional nondestructive evaluation techniques. The results presented in this thesis provided fundamental work towards creating embedded, automated damage detection systems for laminate structures using bondline-embedded d35 piezoelectric transducers

Nondestructive Testing in Composite Materials

In this era of technological progress and given the need for welfare and safety, everything that is manufactured and maintained must comply with such needs. We would all like to live in a safe house that will not collapse on us. We would all like to walk on a safe road and never see a chasm open in front of us. We would all like to cross a bridge and reach the other side safely. We all would like to feel safe and secure when taking a plane, ship, train, or using any equipment. All this may be possible with the adoption of adequate manufacturing processes, with non-destructive inspection of final parts and monitoring during the in-service life of components. Above all, maintenance should be imperative. This requires effective non-destructive testing techniques and procedures. This Special Issue is a collection of some of the latest research in these areas, aiming to highlight new ideas and ways to deal with challenging issues worldwide. Different types of materials and structures are considered, different non-destructive testing techniques are employed with new approaches for data treatment proposed as well as numerical simulations. This can serve as food for thought for the community involved in the inspection of materials and structures as well as condition monitoring