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Glulam timber is gaining popularity as a structural element due to its cost-effectiveness, strength, and environmental benefits. However, being an organic material, it is susceptible to degradation. Therefore, nondestructive testing (NDT) methods are essential for assessing its structural health. In this study, two NDT approaches, ultrasound-based and modal updating, were used to predict the static bending modulus of elasticity (MOE) in Pinus Sylvestris and Spruce species. The results demonstrated that the modal updating and linear regression models outperformed the ultrasound technique in accurately determining the static MOE. Additionally, considering the influence of knots improved the accuracy of ultrasound predictions. [ABSTRACT FROM AUTHOR]

The paper aims to present a bibliographic study of works on the characterization of materials, for mosques and historical minarets, using destructive methods (uniaxial compression, tension direct and indirect), and nondestructive testing (Schmidt rebound hardness, ultrasonic pulse velocity (UPV), scanning electron microscope (SEM) and X-ray diffraction (XRD) and their usefulness in the field of protection built cultural heritage. These religious buildings usually are constructed of brick masonry, stone, or/and reinforced cement concrete. Further, the form and amount of a structural defect is a function of the environment to which the structure is subjected. The different techniques used, for various construction materials, have determined the following parameters: the surface hardness, pulse velocity, structural composition, compressive strength, tensile strength and chemical composition. In general, these parameters govern the behavior under the different actions, and contribute to the strengthening and protection of the structure. [ABSTRACT FROM AUTHOR]

• The damage evolution during fatigue tests and residual strength tests is characterized by AE, DIC, and Micro-CT. • The information recorded by different characterization instruments is classified and compared for verification. • Pearson correlation analysis of classified damage facilitates quantitative analysis of the residual strength evolution. The accumulation of fatigue damage leads to continuous degradation of the residual strength of three-dimensional braided composites, directly determining the fatigue life. However, the inability to continuously collect residual strength and multiple damage modes pose a challenge to study the residual strength degradation mechanisms of three-dimensional braided composites. In this work, digital image correlation and acoustic emission techniques are employed to assess the strain field and damage events of the specimens during the residual strength tests. X-ray computed tomography facilitates the visualization and quantification of the fatigue damage evolution in three-dimensional braided composites. Moreover, the "two-step" damage classification method is applied to isolate the damage mechanisms. The Pearson correlation analysis is preformed between the quantitative results of three non-destructive techniques and residual strength degradation of 3D braided composites. The integration of the outcomes provides a comprehensive depiction of the residual strength degradation mechanisms. [ABSTRACT FROM AUTHOR]

Limited studies have gathered information on structural health monitoring (SHM) of underwater structures, and most of those studies are outdated. The existing methods evaluated structural distresses separately, without accounting for the correlation between the distresses. This study developed a SHM tool which accounts for the reciprocal relationships and priority weights of different structural distresses, and assessed underwater structures using the developed structural health monitoring tool. A new rating method was developed using fuzzy analytic hierarchy process (FAHP) which incorporates visual inspections of surface distresses, nondestructive tests (NDTs), crack details, hydraulic conditions, and casual characteristics of the underwater structures. The SHM tool was applied to 12 underwater structures, including bridges, dams, canals, water tanks and quay walls. The results of NDTs such as rebound hammer tests and ultrasonic pulse velocity tests, crack surveys, and visual observations on underwater concrete structures are employed in the SHM tool and the structures were rated using priority weights allocated to different attributes. The SHM tool developed in this study supports enhanced efficiency and effectiveness of structural health monitoring of underwater structures and proposes a numerical framework which can be employed to rate and compare the structural health of different underwater concrete structures. [ABSTRACT FROM AUTHOR]

Concrete is considered an isotropic material for structural analysis and design purposes. However, during concrete placement and compaction, segregation and bleeding may occur. A water film is deposited around larger aggregate particles, especially on the bottom surface. This effect was already identified in the literature as a cause of anisotropy in compression strength, but there is no evidence of anisotropy of concrete in terms of elastic constants. In this paper, impact acoustics and ultrasound measurements were used to measure dynamic elastic properties in prismatic specimens (125×125×400 mm). The specimens were produced with two directions of concrete placement and compaction: longitudinal and transversal. Three concrete batches were produced with high, medium, and low percentages of cement. Five identical specimens were produced for each combination of concrete mix and direction of concrete placement. A pattern of anisotropy was identified for all specimens through natural frequencies of the specimens and measured ultrasonic wave velocities. Although this effect is small, it could be clearly identified by impact acoustics and ultrasonic tests. [ABSTRACT FROM AUTHOR]

Structural integrity is a major concern for both manufacturers and consumers, thus health monitoring is mandatory for a proper quality control. The use of more reliable and widespread techniques is urged. In this context, this work developed a nondestructive procedure for microstructural characterization of age-hardened aluminum alloys. By the combination of ultrasonic inspection parameters, we developed two highly sensitive methods of hardness evaluation. The results proved the versatility of ultrasonic waves for materials inspection and characterization, expanding the onsite evaluations range. [ABSTRACT FROM AUTHOR]

The LHC collimation system must adopt materials with excellent thermal shock resistance, high electrical conductivity, geometrical stability, and radiation hardness. Two novel composites, Molybdenum–Carbide–Graphite and Copper–Diamond, are proposed for the LHC collimation upgrade. A postirradiation examination was performed to assess the status of the composites, tested under intense proton beam impacts at the CERN HiRadMat facility. Metrology measurements, computed tomography, and 3D topography allowed to evaluate the localized spallation induced by the beam. This article provides an overview of the thermophysical characterization of the two composites before irradiation and nondestructive postirradiation results. [ABSTRACT FROM AUTHOR]

Abstract In the competitive world of aircraft industry, the reduction of maintenance periods is a decisive factor when companies and arm forces are undergoing the procurement processes for the acquisition of their next fleets. Thus being, the investigation in the aeronautical sector today is focusing not only in the development of better and more reliable aircraft systems, but also in the development of techniques and tools that allow for the performance of the required maintenance tasks in faster and more optimized manners. This work arises within this field of investigation addressing the validation of innovative failure preventive equipment for the evaluation of the electromechanical impedance (EMI) response of aeronautical structures, and for the dynamic balancing of propellers of aircraft in the category of Normal, Utility, Aerobatic and Commuter. This work is divided into two parts, in which the first explores the accuracy and competitiveness of one alternative nondestructive test (NDT) equipment developed by Critical Materials S.A. in aeronautical applications, when compared to the classical NDT methods. This part ends with the assessment of the technique's capability to identify defects in one EPSILON TB-30 Nose Landing Gear of the Portuguese fleet which had been put out of service through a high-frequency eddy current inspection. The second part regards the development of a maintenance equipment for the dynamic balancing of propellers systems, specifically optimized for the dynamic balancing of the propeller of the Lycoming engine used in TB-30 aircraft of the Portuguese Air Force. This study ends by highlighting the gains achieved in the overall TB-30 maintenance costs with the use of the developed tool, by comparing the average time used for the process of balancing the Lycoming propeller, with and without the use of this tool. Highlights • The evaluation of the electromechanical impedance response of aeronautical structures was performed • The accuracy and competitiveness of one alternative nondestructive test equipment was explored • The validation of a failure preventive tool for aeronautical applications was carried out • The development and validation of an engine monitoring tool for the dynamic balancing of aircraft propellers was developed [ABSTRACT FROM AUTHOR]

Abstract We employed 2D/3D X-ray computed tomography in conjunction with microzone analysis to study the failure mechanisms of lithium-ion battery packs at low temperatures. A nondestructive X-ray computed tomography strategy confers the direct and comprehensive observation of the hard-swelling of lithium-ion battery packs at low temperatures. X-ray computed tomographic images indicate that severe wrinkles occur in the electrode components, thus shedding light on the evolution of the failure process, which provides a valid secondary analysis of the failure mechanisms without damaging the battery pack. Combined with the results of the microzone analysis, swelling failure can be attributed to the generation of Li dendrites, volume expansion and delamination of the active materials. These processes can be caused by the slow electrochemical kinetics of the active materials at low temperatures. Graphical abstract Image 1087 Highlights • 2D/3D X-ray computed tomography has been applied to studied failure of LIBs. • Nondestructive detection combined with micro-zone and component analysis is useful. • Research reveals that LIBs easily occur swelling failure at low temperature. • Reason of swelling failure of LIBs has been explored by various characterizations. [ABSTRACT FROM AUTHOR]

The ultrasonic pulse velocity method is a nondestructive test commonly used for the determination of the elastic properties of materials and verification of non-homogeneities and damages in structural elements. Another application for the ultrasound is the measurement of the stress state in a material. However, the use of ultrasonic waves for the latter purpose has been poorly studied, mainly regarding application in concrete structures. This paper addresses the use of ultrasound for the evaluation of stresses in concrete structures. Uniaxial compression tests were performed on concrete prisms. During the tests, longitudinal and shear ultrasonic waves were emitted to specimens subjected to different compressive stress levels. The results showed the increase of compression stress leads to higher velocities of ultrasonic waves, which proved the acoustoelastic effect. Such behavior was not observed in longitudinal waves emitted perpendicularly to the direction of the stress application. The largest increase in velocity was observed for longitudinal waves propagating in the same direction of the load application (variations on the order of 1%). Acoustoelastic coefficients were determined for each tested prism, according to the change in the velocities of the ultrasonic waves. The present study contributed to the knowledge on the acoustoelastic behavior of the concrete elements and shows the potential of ultrasonic tests to evaluate the stress state in concrete structures. [ABSTRACT FROM AUTHOR]

Diyarbakir Grand Mosque is one of the oldest and the most significant mosques in the Islamic world and the Mesopotamia. The mosque was heavily damaged due to fire following an earthquake which was predicted 8 magnitude in 1114. It was rebuilt between 1117 and 1125. It is predicted that a great earthquake in the forthcoming years will be occurred in the region. Therefore, conservation and retrofitting works should execute for this 891 years old building. In this study, nonlinear seismic analyses of the main prayer hall of the mosque are performed and damage assessment of it due to a probable great earthquake is determined. Material properties of the mosque are defined by using nondestructive tests. Three level seismic acceleration data are produced by considering seismic characteristics of the region. Damage regions on the mosque are obtained under these earthquake loads. Suggestions about retrofitting of this significant historical mosque are recommended. [ABSTRACT FROM AUTHOR]

The research goal was to assess the stress wave speed in the longitudinal and radial directions of Acer saccharum Marshall and Thuja plicata L. wood and weighting this parameter with the wood density, to determine the dynamic modulus of elasticity. For each species, 32 addoc wood specimens were prepared with an average moisture content of 11 % in which stress waves tests were realized. The experimental design consisted in normality and difference of means tests. The response variables were the wood density and for the longitudinal and tangential directions, the speed of the stress waves and the dynamic modulus. The wood species was considered the variation factor. The stress waves method allowed the dynamic characterization of A. saccharum and T. plicata wood. Significant statistical difference was found between the response variables. The density of A. saccharum wood is greater than the corresponding to T. plicata wood. In the longitudinal direction, the stress wave speed and dynamic modulus of A. saccharum wood are lower than the T. plicata ones. In the tangential direction, the stress wave speed of A. saccharum is bigger than the T. plicata wood. In contrast, the dynamic modulus is smaller. When compared to the tangential direction, the stress wave speed and dynamic modulus are bigger in the longitudinal direction for both species. [ABSTRACT FROM AUTHOR]

Over their lifetime, concrete structures can suffer from different pathologies, one of them is exposure to high temperatures, which diminishes their load-bearing capacity. This study describes how different concrete types were exposed to high temperatures. To simulate fire extinction, where the temperature of the overheated concrete descends suddenly, different cooling systems were applied: slowly cooling in the open air and fast cooling by spraying different water volumes. Several physical-mechanical characteristics were analyzed such as compressive strength, splitting tensile strength, porosity, capillary suction, and carbonation depth. Ultrasound nondestructive tests were conducted to quantify deterioration. A petrographic study using a stereomicroscope and microscopy of polarization was performed on thin sections to evaluate aggregate composition and concrete characteristics, focusing on interface areas. Physical and mechanical properties were affected by the increase in temperature, with damage worsening through the appearance of cracks and microcracks when water is used as a cooling system. [ABSTRACT FROM AUTHOR]

Shrinkage compensating concrete (SCC) and Self-stressing concrete (SSC) technique have been employed for reducing early-age cracking and leakage while the addition of expansive agent would have a negative impact on mechanical properties and durability. The objective of the current research was to quantitatively assess the damage development in cementitious materials with expansive agent by both the strength tests and nondestructive acoustic tests including ultrasonic measurements and acoustic emission (AE) tests. The damage degree was defined based on strength as well as ultrasonic properties and a significant linear relationship was observed between the damage degree and autogenous strains. AE parameters such as AE amplitude, AE counts and AE energy were related to AE activity of the cement-expansive agent system. Crack mode identification was performed based on the relationship between average frequency and RA value (rise time/amplitude). A decreasing ratio of tensile cracks and an increasing ratio of shear cracks were observed which could be an indication of aggravated damage inside the materials. [ABSTRACT FROM AUTHOR]

Degradation of reinforced concrete ( RC) structures is a serious safety problem affecting all industrialized countries, and the economical aspect of this problem cannot be neglected. One of the main reasons for the degradation of RC is the corrosion of steel reinforcing bars as a result of concrete cover cracking and reduction in bar cross section. As a consequence, the structural capacity of RC elements decreases progressively as degradation develops. Nondestructive testing and/or analytical formulation represent high-quality rapid methods for evaluating the corrosion penetration of bars and provide useful parameters for designing retrofits. This paper presents an additional tool that can be used to evaluate and assess the vulnerability of existing structures in terms of the determination of bar cross section lost. Using simple charts and formulas, this can be accomplished by calculating reinforcing bar cross section loss due to corrosion by measuring external crack widths in the concrete cover. Predictions were obtained by using two analytical models developed. These predictions have been satisfactorily compared with both the literature and new experimental results, as well as with previous empirical models available in the scientific literature. The experimental results were obtained by corroding real-scale concrete specimens reinforced with smooth and ribbed bars (according to old and modern building codes) using 3.5 wt% sodium chloride solution and an applied current. [ABSTRACT FROM AUTHOR]

Although several researchers have been working on the mechanical and physical characterization of iron-ore tailings (IOT) in order to consider the possibility of using this material to replace natural aggregate in the preparation of mortars, they have not investigated the dynamic and static modulus of elasticity of IOT mortars yet. Therefore, the main goal of this study is to present an experimental investigation on the determination of the static and dynamic Young’s modulus of IOT mortars using destructive and non-destructive tests respectively. It is also presented the correlation between the IOT mortar static (E ci ) and dynamic (E) elasticity modulus. It is seen that 88% of the observed variation in the elasticity modulus is attributable to the approximate linear relationship between the dynamic and static values, a very impressive result. The results indicate that it is possible to obtain high-performance mortars to be used not only as rendering material but also as structural material in building construction. [ABSTRACT FROM AUTHOR]

Using recycled materials in construction of asphalt pavements yields both economic and technical advantages. Recycled asphalt shingles (RAS) and reclaimed asphalt pavement (RAP) are two major sources to serve this purpose for which proper design and characterization are key elements. In this study, engineering properties of asphalt concrete containing RAP and RAS under dynamic loading were investigated. Three asphalt mixes were designed and included in this research: a conventional mix with no RAP/RAS as a control, a mix with 35% RAP, and finally a mix with 35% RAP and 5% RAS. A conventional resonant column (RC) apparatus was retrofitted and used for testing the specimens in torsional mode. Testing was conducted at five temperatures ranging from 10 to 45°C. Damping ratios and moduli of the mixes were analyzed and compared to assess the effect of the recycled materials on dynamic properties of asphalt concrete. Results clearly show the impact of RAP and RAS in increasing the mix stiffness. The study also included uniaxial dynamic modulus (DM) testing of the control mix to compare the moduli measured at high frequencies through RC testing to those estimated by the DM master curve through extrapolation. Results show that the modulus obtained from RC testing correlates well with that extrapolated from DM tests. Results also indicate that the accuracy of such correlation is significantly increased once dependency of Poisson's ratio on modulus is incorporated. [ABSTRACT FROM AUTHOR]

• Interval analysis model is applied to quantify the uncertainties in the elastic wave tomography of concrete structures. • The relationship between the measurements error and tomography uncertainty was established. • The identified uncertain boundaries provide more information to make a better assessment of the internal condition of concrete. This paper presents a non-probabilistic uncertainty quantification method for the elastic wave tomography of concrete structures. An interval analysis model is applied to establish the relationship between the measurement error and identified tomography images. Measurements of parameters such as travel time and wave amplitude are modeled as intervals described by their upper and lower boundaries. Based on the straight-ray assumption of the wave propagation path, the relationship between wave velocity and travel time measurements is described by a set of linear equations. The inversion linear equation is converted into an extended fuzzy linear equation using interval analysis. Subsequently, a simultaneous iterative reconstruction technique is applied to solve this fuzzy linear equation. In contrast to the traditional methods, the obtained tomography images are described in terms of the upper and lower boundaries. Finally, numerical simulation and experimental investigation using several plain concrete models are conducted to verify the proposed approach. [ABSTRACT FROM AUTHOR]

Aluminum alloys have been chosen over other lightweight structural materials because of their advantages regarding strength, long-term durability, and low cost. Aluminum comes under the category of highly reactive metals, where an inherently stable oxide layer can protect against aggressive corrosive conditions. Therefore, this research investigated the application of the ultrasonic nondestructive technique for inspection and monitoring of corrosion behavior of AA6351 heat-treated aluminum alloys. The samples were artificial age hardened at five different conditions. The complementary engineering experiments for materials evaluation included hardness, X-ray diffraction and salt spray tests. Overall findings showed correlations between ultrasonic and destructive data representing a fast, versatile and reliable inspection technique. Furthermore, findings show a significant correlation (>99%), thus supporting the benefits of the multiparametric ultrasonic test for heat treatment inspection and quality control of lightweight structural materials. • The effect of age hardening on the mechanical and corrosion behavior of AA6351 alloys was examined. • Findings support the applicability of the ultrasonic nondestructive tests for corrosion evaluation. • The technique tested enables the determination of peaks and adjacencies of mechanical strength in AA6351 alloys. • The technique tested can be used in Al-alloys in T4 and T6 conditions. [ABSTRACT FROM AUTHOR]

Estimating pavement surface thicknesses without requiring large footprint equipment or pavement repairs is critical for the structural evaluation of airfield pavement. A research team from the U.S. Army Engineer Research and Development Center conducted an evaluation of eleven nondestructive technologies, including eight ground penetrating radar (GPR) devices and three wave propagation technologies, on twenty-one hot-mix asphalt concrete (AC) and nineteen portland cement concrete (PCC) test locations with varying pavement thicknesses. The different technologies were used to estimate pavement thickness over predetermined test points. For each pavement structure, a core was extracted from one of the test points to provide calibration data of each testing device for data refinement. The accuracy of each technology was quantified by calculating the absolute difference between the actual core measurement and the estimated thickness measurement. The results from the devices tested led to the conclusion that separate devices are required on AC and PCC for optimal performance. The ultrasonic tomography and impact echo devices worked best on PCC surfaces, and the 1 GHz horn antenna GPR devices performed best on AC surfaces. The side-by-side testing demonstrated the capabilities of the technologies on varying pavement structures without discrepancies that would likely occur when comparing one set of results to those from a different study. [ABSTRACT FROM AUTHOR]

Drilled shaft foundations are increasingly being used to support various types of buildings and infrastructure facilities. The load carrying capacity of these drilled shafts is largely dependent on their diameter. The large loads carried by such structural elements make quality control and assurance of their diameters during construction extremely critical. Current methods adopted by the industry for measuring drilled shaft diameters during construction depend on discrete points of concrete volumetric measurements that lack both accuracy and continuity. An empirical model is developed and presented in this paper for computing the diameter of drilled shaft foundations that overcomes these limitations. The model is developed using signal processing performed on cross-hole sonic logging (CSL) experimental data obtained from three drilled shaft specimens. The model is validated using experimental data obtained from two separate specimens. The research reported in this paper demonstrates that there exists a high correlation between the maximum amplitude of CSL signal frequency and thickness of concrete. The results show that the model is capable of accurately computing the diameter of drilled shafts, with an absolute average error of 2.42%. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the steel-to-concrete bond phenomenon in two kinds of deformed bars: black steel and hot-dip galvanized steel. The differences in the steel-to-concrete bond behavior are identified in terms of the load-slip curves and the acoustic emission (AE) patterns measured during pull-out tests. Test results show that the bond capacity and the initial stiffness of the bond stress-slip curve of black steel are approximately 20 and 50% greater, respectively, than those of galvanized steel, and the slip corresponding to the maximum bond stress is approximately 20% times larger in the latter. By measuring the AE activity, it is possible to identify the transitional points between the four stages characterizing interaction between the concrete and the bar subjected to pull-out force. Each transition coincides with a sudden drop in the AE activity. [ABSTRACT FROM AUTHOR]

Two dimensional carbon fiber reinforced silicon carbide composites (2D C/SiCs) subjected to low-velocity impact (LVI) damage were investigated, in order to evaluate the efficiency of stitching as a reinforcing mechanism able to improve the delamination resistance of 2D C/SiCs. The damage microstructures of the specimens at different stitched density (SD) were observed by infrared thermography and industrial computed tomography scanners. While the damage depth of specimens with the SD of 10 mm/needle was greater than that of specimens with SD of 5 or 15 mm/needle, the residual tensile strength of the specimens with the SD of 10 mm/needle was the highest. With the decreasing of SD, the real damage radius of 2D C/SiCs measured by thermography increased whereas the residual tensile strength did not appear the same phenomenon. The 2D C/SiCs with the SD of 5, 10, and 15 mm/needle had good damage resistance after the LVI, with the tensile strength still retaining 72.43%, 95.20%, and 91.49%, respectively. [ABSTRACT FROM AUTHOR]

Partially saturated compacted-sand specimens were characterized by using three-dimensional (3D) image registration of dualmodal (neutron and X-ray) tomography data. Neutron and X-ray imaging provide complementary information for precisely identifying the three phases (silica sand, air, and water) of a compacted sand specimen that is partially saturated. Neutron tomography provides high contrast of the water phase, whereas X-ray tomography provides high contrast of the silica sand phase due to different fundamental interaction mechanisms of neutron and X-ray with matters. X-ray interacts with the electron cloud surrounding the nucleus, whereas neutron radiation interacts with the nucleus of an atom. In this paper, a computational technique was developed to unify digital images of dual-modal data obtained at different image resolution and specimen orientations based on the maximization of the normalized mutual information to combine the information from the water phase inferred from a neutron image and information from the sand and pore phases obtained from an X-ray image. The combined microstructure obtained from registered X-ray and neutron images can thus be analyzed in 3D to precisely differentiate silica, air, and water distribution spatially. Microstructure information for granular assembly including pore size distribution and coordination number was determined from X-ray tomography data due to higher precision in identifying solid particle boundaries. Local values of saturation along the height of the specimen are obtained from the pore and water phases segmented from the registered neutron and X-ray images. Image registration of neutron and X-ray images provides the ability to obtain the microstructure of partially saturated sand in terms of the detailed variation of solid particles, air, and water phases spatially. [ABSTRACT FROM AUTHOR]

Nondestructive testing (NDT) methods for identifying stress levels in materials mostly rely on the theory of acoustoelasticity. However, the sensitivity and the accuracy of acoustoelasticity are affected by several factors such as the (1) type, (2) propagation, and (3) polarization directions of the used signals. This paper presents the results of an experimental investigation of longitudinal waves propagating perpendicular to the applied uniaxial tensile stresses in structural steel specimens. The changes in four ultrasonic signal characteristics were investigated with increasing stress levels ranging from below to above the yield stress of steel. The considered signal characteristics were the peak amplitudes and signal energy in the time domain, and the fast Fourier transform (FFT) and chirp-Z transform (CZT) in the frequency domain. Even though the acoustoelastic effect on the type ultrasonic signal used is very small, clear distinctions between prior to and postyielding are observed for all investigated parameters. The results are presented with a detailed statistical and receiver operating characteristics (ROCs) analyses. The results show that identifying damage to steel structures due to local yielding is possible using the simple ultrasonic signal classification. [ABSTRACT FROM AUTHOR]

Stress and residual stress are two crucial factors which play important roles in mechanical performance of materials, including fatigue and creep, hence measuring them is highly in demand. Pulse eddy current (PEC) and ultrasonic testing (UT) are two non‐destructive tests (NDT) which are nominated to measure stresses and residual stresses by numerous scholars. However, both techniques suffer from lack of accuracy and reliability. One technique to tackle these challenges is data fusion, which has numerous approaches. This study introduces a promising one called neural network data fusion, which shows effective performance. First, stresses are simulated in an aluminium alloy 2024 specimen and then PEC and UT signals related to stresses are acquired and processed. Afterward, useful information obtained is fused using artificial neural network procedure and stresses are estimated by fused data. Finally, the accuracy of fused data are compared with PEC and UT information and results show the capability of neural network data fusion to improve stress measurement accuracy. [ABSTRACT FROM AUTHOR]

The lightweight deflectometer (LWD) is a portable device that measures surface deflections and applied force, from which dynamic stiffness and elastic modulus can be estimated. The inclusion of radial offset sensors with LWD testing, referred to here as multiple sensor LWD testing, stemmed from the well-established falling weight deflectometer (FWD) testing method. However, little research exists in the literature addressing LWD use on stabilized or lightly bound layers with multiple sensors, or exploring the applicability of backcalculating/ isolating layer moduli from multiple sensor LWD tests. To this end, over 200 multiple sensor LWD tests on stabilized base materials were performed at five sites and rigorously analyzed to determine if the test could capture growth in stabilized base stiffness while the underlying subgrade layer remained unchanged. Deflection results demonstrate that the LWD test is capable of detecting changes in the stiffness of the stabilized base material during curing as illustrated by the decreasing magnitude in center deflections. Furthermore, radial offset deflections measuring 60 cm from the plate center remained constant during curing, providing valuable information about the subgrade support. The findings made directly from the deflections were confirmed via an analytical backcalculation using Boussinesq's equations and Odemark's method of equivalent thickness. The use of multiple sensor LWD testing allows for a richer interpretation of earthwork behavior than the traditional center deflection LWD results. [ABSTRACT FROM AUTHOR]

The results of studies into the usefulness of 3D surface roughness parameters determined by 3D laser scanning, for the nondestructive evaluation of the pull-off adhesion of concrete layers are presented. Twenty-one 3D roughness parameters were identified. Their correlations with pull-off adhesion f b determined by the semi-nondestructive pull-off method were established. For two of the parameters, i.e. the texture aspect ratio ( Str ) and the peak material volume ( Vmp ) the correlation coefficient was found to be high. The possibility of the nondestructive evaluation of the pull-off adhesion on the basis of solely the existing concrete topography examinations is critically looked at. [ABSTRACT FROM AUTHOR]

This paper presents a new nondestructive way of identifying the values of pull-off adhesion between the concrete layers in concrete floors. It based on the roughness parameters of the base layer surface, using the nondestructive optical technique, and on the floor surface, using the nondestructive acoustic techniques and employing artificial neural networks (ANNs) for this purpose. The new way has a potential for being widely used in practice, whereby it may become possible to employ previously trained ANNs to identify the pull-off adhesion, without impairing the surface of the tested concrete floor. [ABSTRACT FROM AUTHOR]

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter () varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance () and receiver spacing (), and (2) for two different heights () of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength () and minimum wavelength () associated with the combined dispersion curve, corresponding to a particular combination of and , were noted to increase almost linearly with an increase in the magnitude of the input source energy (). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of . Based on statistical analysis, two regression equations have been proposed to determine and for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. [ABSTRACT FROM AUTHOR]

This paper presents the development and validation of a cyberinfrastructure architecture for research in nondestructive evaluation (NDE) using acoustic emission (AE) data. Existing cyberinfrastructures for civil engineering focus in the curation and preservation of data. In contrast, the proposed cyberinfrastructure is intended to serve as a tool to enable innovation by providing a platform to prototype analysis techniques and sharing data and analysis methods among a research team while removing the burden of memory and computational cost from the user. This is achieved by streamlining the access of large and complex experimental data sets, facilitating the selection of part of the experimental data depending on data features, distributing data analysis using a distributed computing strategy, and allowing the creation of new data features that can be used for subsequent analysis. The experimental data set potentially include data from AE sensors, strain gages, load cells, clip gages, and accelerometers. The proposed framework uses a relational database to store data, web services for data communication, a Condor pool for high throughput computing, and a graphical interface for interaction with the user. An example using data obtained from a compact tension fatigue test is used to show the capabilities of the developed framework. [ABSTRACT FROM AUTHOR]

This paper is about diagnosis and classification of bearing faults using Neural Networks (NN), employing nondestructive tests. Vibration signals are acquired by a bearing test machine. The acquired signals are preprocessed using discrete wavelet analysis. Standard deviation of discrete wavelet coefficient is chosen as the distinguishing feature of the faults. This feature vector is given to the design network as inputs. The input vector is normalized prior to be applied to neural network. There are four output neurons each of which corresponds to: 1) bearing with inner race fault 2) bearing with outer race fault 3) bearing with ball defect, and 4) normal bearing. The structure of NN is 6:20:4 and with 99 % performance. [ABSTRACT FROM AUTHOR]

The falling weight deflectometer (FWD) testing develops a deflection basin on the pavement surface. Depths of this deflection basin from the center of the falling weight are measured at different radial offsets. These deflections are used for the backcalculation of the pavement layer moduli. Most of the available backcalculation software uses the layered elastic theory and static load to calculate moduli from known pavement surface deflections. However, the FWD test load is dynamic, and layer materials may show nonelastic behavior. Layered elastic theory in these types of software cannot characterize dynamic response of the pavement. Also, elastic theory is unable to accurately predict the surface deflection whenever stress developed in any pavement layer exceeds the yield point. For this reason, this study has performed a finite-element analysis of the airport pavement under the FWD test considering the dynamic load and materials plasticity. The analysis presented here includes elastoplastic behavior of pavement layer materials. Both axisymmetric and quarter cube models have been developed in ABAQUS. Time-deflection histories are simulated to match the FWD test data. A comparison is made between the dynamic, static, and field deflection basins. Contours of vertical deflection and strain are also plotted to observe their distribution on both the axisymmetric and quarter cube models. Analysis results show that the time-deflection histories are in close agreement with the field data. The axisymmetric model yields better results than the quarter cube model. Deflections from the static analysis are greater than the dynamic analysis for an identical set of the layer modulus of elasticity. A uniform distribution of strain is observed from the static analysis in both of the geometries. However, the dynamic analysis does not show similar distribution because of the time-dependent response. [ABSTRACT FROM AUTHOR]

The paper deals with the nondestructive identification of defective concrete zones in unilaterally accessible massive members, for example, access galleries in hydroelectric power plants. The concrete in such zones is, for various reasons, excessively porous. The authors propose to use state-of-the-art acoustic testing techniques, including ultrasonic tomography, integratively to detect and identify defective zones. An original methodology for such tests has been developed. The methodology is illustrated with an example of its practical application to a real civil engineering structure. [ABSTRACT FROM PUBLISHER]

The topic of the present paper is a damage detection technique based on the theory of proper orthogonal decomposition (POD). Numerical examples and experimental verification are conducted on an aluminum plate. The numerical examples provide useful information on the effect of several parameters, such as damage severity, type of excitation, noise level, and grid size of the sensors and on the reliability of the technique. The experimental verification using the POD method on the acceleration data show that it is possible to locate some defects in a cantilever plate; however, the analysis of the experimental data highlights the sensitivity of the method to the modification of the boundary conditions. Finally, the application of this technique to the detection of delamination in composite materials is conducted numerically on a cantilever beam. A three-dimensional model was used to investigate how the position of the damage along the length and thickness of the beam is detected and to demonstrate the sensitivity of the method to the location of the sensors with respect to the position of the damage. [ABSTRACT FROM AUTHOR]

The future of highway infrastructure in the United States is at a critical junction. Nearly one-third of U.S. bridges are nearing the end of their design life, and one in ten bridges is categorized as structurally deficient. While the design and construction of the next generation of U.S. highway bridges is underway, existing bridges must be maintained through proper inspection and load rating. This paper proposes an objective load rating protocol that takes advantage of a shift in the bridge design, construction, and management paradigm to include structural modeling, instrumentation, and nondestructive testing. A baseline structural model is created and verified using structural health monitoring (SHM) data collected during a controlled static load test. The structural model is then used to calculate load rating factors of the bridge at both current and simulated damaged conditions. The resulting load rating factors are compared with the AASHTO load resistance factor rating method. [ABSTRACT FROM AUTHOR]

The light weight deflectometer (LWD) is a portable, nondestructive testing device that can estimate pavement layer parameters, namely moduli. Conventional backcalculation of layer parameters from LWD deflections is formulated as an inverse problem where predicted vertical deflections are matched to observed vertical deflections using a gradient search algorithm. In this paper, we present an LWD backcalculation scheme to recover layer parameters, including top-layer thickness, of a two-layer earthwork system. Our approach resolves the problem using a dynamic finite-element (FE) model for the forward calculation of LWD deflection data and implements a genetic algorithm (GA) as the inverse solver. The objective function we minimize is formulated as a measure of the data misfit between predicted and observed data, normalized by the peak deflections, and it includes 180 data points from the dynamic deflection time history. The objective function contains multiple local minima that can potentially trap gradient search algorithms, thus validating application of GA as a global search technique for this problem. The GA is applied to both synthetic and experimental data, and we demonstrate that the recovered top-layer thickness, top-layer modulus, and underlying modulus for the experimental data compare favorably with expected values. [ABSTRACT FROM AUTHOR]

Ground reinforcement anchorages are a means of ensuring the stability of a wide range of structures and retaining walls. The performance of an individual anchorage depends on the tensile load that the anchorage is carrying but this will change over the anchorage's life span, so it is therefore necessary to have some way of measuring this load. A nondestructive technique, ground anchorage integrity testing (GRANIT), in which impulse responses of anchorages are determined to evaluate whether load transfer is maintained, has previously been developed for anchorages in rock. This research examines the possibility of extending this to soil anchorage systems. In this work, implementation of a model nondestructive testing system is tested using a geotechnical centrifuge. Load distributions along centrifuge model anchorages are measured and found to reduce gradually within the fixed length, as is the case with rock. Anchorage frequency responses to impulse loads are then evaluated to validate the consistency of the results obtained. Various anchorage inclinations and fixed lengths are also investigated, showing that inclined anchorages contain a greater range of frequencies in their signature response. The practical importance of these results is that nondestructive testing may be usable for anchorages in soil as well as anchorages in rock. Further investigation is necessary to refine the relationship between anchorage load and response frequencies. This may be accomplished using centrifuge modeling. [ABSTRACT FROM AUTHOR]

In recent decades, road inspections have increasingly relied on the use of nondestructive instrumentation for the evaluation of road conditions. This work aims to test a ground-penetrating radar system to provide insight into nonvisible subsurface engineering with respect to an underpass arch-shaped structure. One important structural parameter that affects the stability of the arch structure and must be monitored is the quantity and thickness of the backfill used to fill the structure until the road is level. Frequencies of 500 and 200 MHz were used to detect the different layers over an arch structure. However, the heterogeneity of the backfill over the arch hampered interpretation of the field data. Finite-difference time-domain modeling was used to understand the response of the radar wave and to assist in interpretation. More realistic models were created based on the accurate geometry provided by a mobile light detection and ranging (LiDAR) device. The methodology is not excessively time-consuming, with all of the procedures taking a total of approximately 7 h. With this system, the layers built and their thicknesses can be defined with a maximum error of 5%. Appropriate nondestructive testing of the subsurface structure is useful in facilitating structural analysis and the prediction of critical failures. [ABSTRACT FROM AUTHOR]

Magnetic methods are progressing in the detection of corrosion in prestressing strands in adjacent precast, prestressed concrete box-beam bridges. This study is the first field trial of magnetic strand defect detection systems on an adjacent box-beam bridge. A bridge in Fayette County, Ohio, which was scheduled for demolition, was inspected. Damage to prestressed box-beams is often due to corrosion of the prestressing strands. The corroded strands show discontinuities and a reduced cross-sectional area. These changes, due to corrosion, are reflected in the magnetic signatures of the prestressing steel. Corrosion in the prestressing steel was detected using two magnetic methods, namely the ‘magnetic flux leakage’ (MFL) and the ‘induced magnetic field’. The purpose of these tests was to demonstrate the ability of the magnetic methods to detect hidden corrosion in box-beams in the field and tackle the logistic problem of inspecting box-beams from the bottom. The inspections were validated by dissecting the bottom of the box-beams after the inspections. The results showed that the MFL method can detect hidden corrosion and strand breaks. Both magnetic field methods were also able to estimate corrosion by detecting the effective cross-sectional area of the strand in sections of the beams. Thus, it was shown that the magnetic methods can be used to predict hidden corrosion in prestressing strands of box-beams. [ABSTRACT FROM AUTHOR]

High spatial resolution () neutron tomography was performed on partially water-saturated compacted silica sand specimens with two different grain morphologies (round and angular) at Helmholtz Zentrum Berlin using cold neutrons at the cold neutron radiography and tomography beam line. A specimen mixed with heavy water was imaged for contrast comparison purposes. Microfocus X-ray imaging was also performed on these specimens with slightly higher resolution () using geometric magnification to locate the solid phase (silica particle boundaries) more precisely. Image processing was performed to remove unwanted gammas detected because of the gadox scintillator used for the high-resolution neutron imaging system. The visualization of solid, gas, and liquid phases for different grain morphologies is presented at the grain level. Using dual-modal contrast possible from simultaneous use of neutrons and X-rays, the authors introduce, for the first time, an improved ability to distinguish solid silica, liquid water, and gas phases. Quantitative analysis using three-dimensional tomography data is demonstrated for obtaining void ratio, void percentage variation over the height, and particle size distribution. [ABSTRACT FROM AUTHOR]

Many of the older bridges in the United States have no original contract documents available, and about 26,000 bridges that are rated as scour critical have unknown foundation conditions. Thus, no information is available regarding the type, depth, geometry, or material of these scour critical bridge foundations. The unknown bridge foundations pose a significant problem to bridge owners because of safety concerns. This paper presents the determination of an unknown bridge foundation depth at Forth Worth, Texas. The bridge was supported by driven steel H-piles. Three nondestructive testing (NDT) techniques were utilized: (1) the parallel seismic (PS) method, (2) the sonic echo (SE) method, and (3) resistivity imaging (RI). The main objective of this present study was to compare the suitability of NDT techniques to determine the unknown bridge foundation depth. Based on the field test results, both PS and RI methods provided foundation depth close to actual foundation depth. However, the SE method was determined to be unsuitable for determining the unknown steel H-pile depth. [ABSTRACT FROM AUTHOR]

This paper is a transitory decadal overview capturing the current research and technology accomplishments that are being developed by the Optical Instrumentation and Nondestructive Evaluation (NDE) Branch at the National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC). The emphasis is on the latest GRC research and technology advances with a brief discussion of the history and technical background of optical instrumentation since the 1940s, NDE sciences and methods since the 1970s, fiber optics since the 1980s, space-qualified instrumentation since the 1990s, and propulsion health monitoring since the beginning of the current century. This paper also identifies and describes recent and future technical directions based on/guided by current NASA strategic and GRC and NASA project implementation plans. [ABSTRACT FROM AUTHOR]

The field application of three different nondestructive tests (NDTs)-air-coupled impact echo (IE), infrared (IR) thermography, and sounding (chain drag)-are evaluated in this paper, where an actual in-service concrete bridge deck is tested. Two different contactless IE test equipment sets are deployed as part of an effort to develop new rapid measurement methods. The IE data are presented as two-dimensional frequency maps, and the IR data are presented as temperature maps over the tested area. Sounding (chain-drag) result maps are also presented. For verification of the location of near-surface delamination damage, eight drilled core samples were extracted from the test area. The results obtained from each of the individual NDT methods show reasonably good agreement with the drilled cores in terms of locating near-surface delamination. Finally, the NDT methods are compared across general performance criteria, considering accuracy, testing practicality, and costs. The analysis shows that all of the evaluated NDT methods are comparable, and the chain-drag method is not more accurate and reliable for detection of shallow delamination in the deck. [ABSTRACT FROM AUTHOR]

The paper reports the results of a research aimed at analyzing and interpreting the cracking pattern on the Cappella dei Principi (Prince's Chapel, the Medici's mausoleum) in the Basilica of San Lorenzo (Florence, Italy). The research was motivated by the sudden collapse of a keystone of an internal barrel vault sustaining one of the lateral apses. After a brief description of the geometry of the structure, the principal results obtained from in situ surveys (flat-jack tests and cored samples) are described; then the numerical analyses developed both to obtain the static identification of the monument and to assess the possible causes leading to the observed failure are illustrated. The numerical modeling operation has been performed step by step, from linear and quite simple models built with plane elements up to a nonlinear model with three-dimensional elements. The nonlinear FEM, which has been tuned by utilizing the results of the in situ measures, is allowed to both qualitatively and quantitatively reproduce the behavior of the structure and its static problems in the area of the barrel vault over the side apses, allowing for justification of the manifested damage. The comprehension of the structural behavior allows identification of a proper retrofitting strategy. [ABSTRACT FROM AUTHOR]

This paper presents a network-level structural capacity indicator for asphalt pavements in the state of Virginia. A literature review revealed that several network-level structural capacity indexes have been proposed, and a number of states use structural capacity measures in their network-level decision processes. Some decision methods and structural indexes are compared in this paper using network-level deflection data collected using the falling weight deflectometer and distress data from tests conducted on Virginia interstates. One index that is based on the structural number concept, the Structural Capacity Index, is found to produce network-level decisions that most closely match project-level work done by the Virginia Department of Transportation during the 2008 construction season. The index was adopted, and its sensitivity to various input parameters was determined. Furthermore, the impact of the structural capacity of the pavement on the service life of a pavement maintenance treatment was clearly established in this paper. Equations to define the service life of a corrective maintenance treatment as a function of the structural condition of the pavement are also presented in this paper. [ABSTRACT FROM AUTHOR]

In our country, in-situ quality control/quality assurance (QC/QA) of granular pavement layers (subgrade, subbase and base) still relies on their density and moisture measurements. With the coming changes from an empirical to mechanistic-empirical pavement design methods, it becomes essential to move towards changing the QC/QA procedures of compacted granular materials from a unit weight-based criterion to a stiffness/strength based criterion. Unit weight criteria unable to provide sufficient information about the engineering properties of granular layers, thus a missing link occurs between the design process and construction quality control. Dynamic Cone Penetrometer (DCP) is a non-destructive, effective, fast and reliable testing method which is used to determine the stiffness/strength of granular pavement layers and subgrade. In this study, information about the DCP test device, implementation and evaluation of the test results are given, and studies are summarized in the literature. It is seen that very limited research has been done in our country on this subject. Adaptation of in-situ stiffness/strength measuring test device such as DCP to quality control/quality assurance specifications of our country will make it possible to provide more information about the mechanical properties of the granular pavement layers for the pavement design and maintenance engineers. [ABSTRACT FROM AUTHOR]