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An advanced video deflectometer using actively illuminated LED targets is proposed for remote, real-time measurement of bridge deflection. The system configuration, fundamental principles, and measuring procedures of the video deflectometer are first described. To address the challenge of remote and accurate deflection measurement of large engineering structures without being affected by ambient light, the novel idea of active imaging, which combines high-brightness monochromatic LED targets with coupled bandpass filter imaging, is introduced. Then, to examine the measurement accuracy of the proposed advanced video deflectometer in outdoor environments, vertical motions of an LED target with precisely-controlled translations were measured and compared with prescribed values. Finally, by tracking six LED targets mounted on the bridge, the developed video deflectometer was applied for field, remote, and multipoint deflection measurement of the Wuhan Yangtze River Bridge, one of the most prestigious and most publicized constructions in China, during its routine safety evaluation tests. Since the proposed video deflectometer using actively illuminated LED targets offers prominent merits of remote, contactless, real-time, and multipoint deflection measurement with strong robustness against ambient light changes, it has great potential in the routine safety evaluation of various bridges and other large-scale engineering structures.

Airport pavements are widely constructed as airport runways, taxiways, and aprons. The airport traffic should be considered during the design stage of airport pavements before the construction. To protect airport pavements from negligent overload, a pavement strength rating system and an aircraft load classification system are adopted. Under the rating systems developed by the International Civil Aviation Organization (ICAO), Aircraft Classification Number (ACN) and Pavement Classification Number (PCN) are calculated to assess the aircraft loads and the load-carrying capacity of the airport pavements for unrestricted operations. With the increase in the air transport demand, increasing attention on the continuous evaluation of airport pavement conditions is introduced to airports across the globe. The load-carrying capacity can be evaluated to assess airport pavement conditions by calculating the value of PCN continuously during the service cycle of pavements. The value of PCN can be estimated by testing the response of stationary dynamic loads, adopting a Falling Weight Deflectometer (FWD) or a Heavy Weight Deflectometer (HWD) device that simulates the stress generated by aircraft movements. By evaluating the PCN continuously in Airport Pavement Management System (APMS), cyclic determinations of the load-carrying capacity can be conducted to support the maintenance and rehabilitation (M&R) decision-makers. This review summarizes the methodology for determining the PCN and the tests conducted for evaluating the strength of airport pavement presented in the published literature. Further, the review highlights the benefits of determining PCNs by adopting the FWD or HWD field data with more precise results through mechanistic procedures.

In-situ testing programs are conducted to evaluate the potential use of the light weight deflectometer (LWD) device for measuring the in-situ deformation modulus of subgrade soil layers stabilized with geosynthetic reinforcement. A series of in-situ field tests are carried out on six test sections that include 1) unstabilized subgrade soil and 2) geogrid- and geocell-reinforced stabilized subgrade soil. Field measurements on the modulus improvement factor ( MIF ) of stabilized subgrades provide more practical and realistic results. The MIF value depends on the type, geometry, location of geosynthetic reinforcements, and characteristics of subgrade soil. An accurate and quick evaluation of MIF can help in the timely design and execution of new road networks. The novelty of the study comprises of measuring the in-situ MIF of geosynthetic stabilized subgrade soil using a light weight deflectometer (LWD) device and comparing the results with the in-situ plate load test (PLT) and falling weight deflectometer (FWD) devices for the considered test configurations. The deformation modulus from LWD test demonstrated a similar trend to the modulus values obtained from PLT and FWD. The improved in-situ deformation modulus from three different tests ( E PLT , E LWD , and E FWD ) are found to be 29.5 MPa, 34.5 MPa and 114.8 MPa for geocell; 21.1 MPa, 25.7 MPa and 86.2 MPa for biaxial geogrid; 37.2 MPa, 29.7 MPa and 89.5 MPa for triaxial geogrid, when the geosynthetic reinforcement is embedded at a depth of 100 mm. In addition, the MIF values of geosynthetic stabilized subgrade soil for the considered test sections are found to be in the range of 1.0 to 2.5.

The nature of gravity’s influence on antimatter systems is still one of the most profound questions in modern physics, probing the very foundation of both General Relativity and the Weak Equivalence Principle (WEP). By performing a precise measurement on the free-fall acceleration of antihydrogen (${\\bar {H}}$ H¯ ) experiments investigate whether antimatter experiences acceleration due to gravity in the same way as ordinary matter systems, a fundamental assumption that, if falsified, could signal new physics beyond the Standard Model. In the Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy (AE${\\bar {g}}$ g¯ IS), located at CERN, a pulsed ${\\bar {H}}$ H¯ beam is formed via charge-exchange reaction of positronium (Ps) and antiprotons (${\\bar {p}}$ p¯ ). The ultimate intention for this beam is to pass the ${\\bar {H}}$ H¯ through an instrument designed to measure the free-fall of particles, this device is known as a moiré deflectometer. In transport from the ${\\bar {H}}$ H¯ formation to the moiré deflectometer, the ${\\bar {H}}$ H¯ produced encounter both physical obstacles and nonuniform environmental conditions. ${\\bar {H}}$ H¯ atoms entering the moiré deflectometer will be monitored from multiple detector systems designed to measure annihilation radiation both axially and radially. The purpose of this report is to present the operating physics principles and current developmental status of the moiré deflectometer.

The article investigates the impact of applying a dynamic computational model that considers inertia forces on pavement deflections under rapidly changing loads over time. This study is particularly relevant to the modelling of falling weight deflectometer (FWD) testing. Initially, the article examines the deflection values obtained from computational models under loads with varying frequencies. In this context, considering inertia forces was significant for load durations shorter than 0.04 s. In such cases, the results of static and dynamic analyses differed considerably. One application of FWD measurement results is determining the stiffness moduli of pavement layers using backcalculation. The study explored the impact of incorporating inertia forces into the pavement model on the estimated values of stiffness moduli obtained via backcalculation. The results revealed differences of several percent between the stiffness moduli calculated using dynamic and static numerical models. Subsequently, the key pavement deformations and fatigue life were determined using the obtained moduli. Again, significantly different results were observed between dynamic and static cases. Based on these findings, it can be concluded that dynamic effects should not be ignored when using FWD testing for backcalculation. Additionally, the article addresses the sensitivity of backcalculation results, which is crucial for the accurate interpretation of the obtained data.

In the context of the Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy (AEgIS) located at CERN, positron-positronium converters with a high positron-positronium conversion efficiency have been designed in both reflection and transmission geometries. The converters utilize nanochanneled silicon target technology with positron conversion efficiencies up to around 50% and around 16%, at room temperature and in the absence of magnetic fields, for reflection and transmission respectively. The positron-positronium converters allow for the pulsed production of antihydrogen ( H ¯ ) within the AEgIS experiment. This paper discusses the use of a pulsed H ¯ beam in a moiré deflectometer to perform a precise gravitational measurement on H ¯ at AEgIS. This work describes the principles and technical details of the current design of a moiré deflectometer using the pulsed H ¯ beam. The main goal of this work is to summarize the ongoing project of adding the described moiré deflectometer to the AEgIS experiment to further their efforts toward probing the material dependence of gravity and testing the weak equivalence principle (WEP).

Geosynthetics are increasingly used in forest road construction for their potential to improve structural performance and reduce material consumption. However, little is known about their influence on dynamic modulus measurements derived from Light Weight Deflectometer (LWD) testing. This study investigates how different geotextiles affect stiffness measurements immediately after construction and two years later. Five reconstructed forest roads in the Czech Republic were divided into control and geotextile-reinforced subsections (PP150 with geogrid, PP200, and PP800). Modulus differences between the surface and subgrade (S–SG) and differences after two years (S2–SG) were analysed using permutation ANOVA, Cohen’s d, and linear mixed-effects models. The results showed significant short-term reductions in measured modulus for PP150 and PP800, which diminished over time. Only PP800 maintained a strong effect at the two-year mark. Interaction effects with base material types revealed potentially adverse synergies, particularly between PP800 and vibrated gravel. These findings suggest that as LWD is commonly used during road construction for quality control, these early misleading readings may lead to unnecessary over-compaction or increased layer thicknesses, resulting in elevated construction costs and a higher carbon footprint, which counteract the sustainability goals often associated with geosynthetic use. The study highlights the need for long-term monitoring and method refinement in evaluating geosynthetic-reinforced unpaved roads.

The falling weight deflectometer (FWD) test is a prevalent non-destructive testing (NDT) technique in engineering that is essential for evaluating pavement conditions. In this work, the transfer function (TF) theory in frequency domain analysis was applied to address the technical challenges present in FWD research. A pavement system transfer function (PSTF) was proposed as a novel approach for evaluating pavement conditions. The spectral method with fixed-end boundary conditions (B-SEM) was employed to compute the theoretical deflection data for different pavement structures with bedrock during FWD testing. The fast Fourier transform (FFT) technique was used to convert the data into the frequency domain, enabling the construction and calculation of the PSTF. The validity of the PSTF theory was confirmed, and the pavement information contained in the PSTF spectrum was discussed. An analysis and summary are conducted on the impact of variations in pavement attributes on the spectrum. The results indicate that the proposed PSTF contains information regarding pavement system, including the structural layer modulus, structural layer thickness, and bedrock depth. The pavement conditions can be evaluated by directly analyzing the PSTF without considering external factors. The PSTF spectrum is most significantly influenced by bedrock depths between 200 and 500 cm. For every 50 cm variation in bedrock depth, the coefficient of increase and decrease (CIE) of peak frequency ranges from 8.1% to 23.1%. The PSTF spectrum is highly sensitive to variations in the subgrade modulus between 40 and 70 MPa. In this range, the CIE of peak amplitude is greater than 11% for every 10MPa variation in subgrade modulus. The impact of the modulus and thickness of both the surface layer and base layer on the spectrum is noteworthy and should not be disregarded. Spectral analysis is used to summarize the variation in pavement attributes within the PSTF spectrum, serving as a theoretical foundation for further investigations.

This study analyzes the dynamic deflection, stress, and strain responses of cement concrete pavement under different void positions, areas, shapes, surface layer parameters, and Falling Weight Deflectometer loads, based on a three-dimensional solid model of the void area in cement concrete pavement. Results show that the void position has a significant impact. For slab corner voids, the deflection presents a semi-sinusoidal variation with a lagging peak. For slab edge voids, the deflection increases monotonically with the void area. For slab center voids, the deflection is insensitive to the void area, and the damage exhibits cumulative and irreversible characteristics. Among the surface layer parameters, an increase in elastic modulus reduces the deflection and strain at all positions (while increasing the stress at slab edges and centers). An increase in thickness consistently reduces the deflection and strain (with a slight increase in stress at slab centers). And changes in Poisson’s ratio have a negligible effect on the responses. The influence of void shape varies by position: rectangular voids tend to cause high stress concentration, while oval and polygonal voids result in better (more favorable) responses. This study provides a theoretical foundation for void disease assessment based on multi-dimensional mechanical parameters.Article highlightsFor slab corner voids, max deflection linear with void area, max stress decreases then rises, max strain evolves in 4 stages.For slab edge/center void, edge has monotonic deflection & 3-stage strain; center shows slight deflection, dispersed stress & decrease-increase-decrease strain.All voids’ mechanical parameters rise linearly with FWD load, but differ in mechanisms: corner (stress concentration), edge (cantilever), center (global bending).

The application of supervised machine learning algorithms to provide solutions for various civil engineering problems is an emerging trend. This paper presents the utilization of artificial neural network (ANN) and random forest regression (RFR) for the prediction of the elastic moduli of multi-layered pavement based on the falling weight deflectometer (FWD) test. The establishment of ML models includes data preprocessing, hyperparameter optimization, and performance evaluations. The ML models are created from both ANN and RFR techniques using 122,500 datasets from a theoretical model of the FWD test, generated by employing an exact stiffness matrix method for the analysis of multi-layered flexible pavement. The performance measures of both ML models, developed from the synthetic dataset, indicate that the output variables (the predicted pavement moduli) are precisely explained by the input parameters (the measured surface displacements). Both ML solutions are then compared with the FWD test results performed on the road infrastructures in Thailand, showing good agreement with the predicted moduli from the FWD tests. Between the two ML solutions, RFR displays better accuracy in predicting the pavement moduli from the FWD tests with the R2 values of the predicted elastic moduli exceeding 90%. Besides, a sensitivity analysis is carried out to illustrate the impact of surface deflections recorded at each geophone on the predicted pavement moduli. The present study demonstrates the efficacy of ML techniques in assessing road infrastructures and highlights the significance of sensitivity analysis in enhancing the accuracy of pavement performance prediction.