Structural Conditions Research Articles

Deformation tracking of honeycomb structure based on image skeletonization and branch point matching

Honeycomb structures have attracted much attention in various engineering fields due to its superiorities in high specific strength, high specific stiffness and excellent energy-absorbing characteristics. Therefore, it is very important to obtain the deformation state of honeycomb structure in the studies of its manufacturing process and mechanical behavior. In this study, a simple and efficient strategy for tracking the deformation of thin-walled honeycomb structure based on image skeletonization and branch points matching is presented. Principle and process of the new proposed strategy are first detailed, including image skeletonization, branch points selection, matching expansion and deformation calculation, etc. Simulations and experiments with compression and tensile deformations are performed to verify the efficiency of the proposed strategy. The results indicate that the displacement measurements based on the proposed strategy are able to provide subpixel-level accuracy, even though some interference branch points are generated during deformation. In addition, the limitations of the proposed strategy are discussed, which points out the train of thought for the subsequent research.

LONGITUDINAL-RADIAL VIBRATIONS OF A VISCOELASTIC CYLINDRICAL THREE-LAYER STRUCTURE

The paper considers a cylindrical three-layer structure of arbitrary thickness made of viscoelastic material. It consists of two external bearing layers and a middle layer, the materials of which are generally different. The problem of nonstationary longitudinal-radial vibrations of such a structure is formulated. Based on the exact solutions in transformations of the three-dimensional problem of the linear theory of viscoelasticity for a circular cylindrical three-layer body, a mathematical model of its nonstationary longitudinal-radial vibrations is developed. Equations are derived that allow, based on the results of solving the vibration equations, to determine the stress-strain state of a cylindrical structure and its layers in arbitrary sections. The results obtained allow for special cases of transition into cylindrical viscoelastic and elastic two-layer structures, as well as into homogeneous single-layer cylindrical structures and round rods.

Features of the defect structure of a lithium-gradient nonlinear optical single crystal LiNbO3 and their manifestation in the Raman spectra

LiNbO3 crystal with a lithium composition gradient of Li/Nb = 0.8 wt%/cm (Li0.97..1.01Nb1.03..0.99O3) were obtained. A monotonic change in the edge of the UV absorption edge is observed when scanning the surface of the gradient crystal along the growth direction. Raman spectra from different areas of studied crystal were analyzed in a wide frequency range, which includes the region of fundamental vibrations of the crystal lattice (100–900 cm−1) and the region of overtone processes (900–3000 cm−1). A compositionally homogeneous, congruent LiNbO3 crystal was used as a comparison sample. It was found that in the spectra obtained from different parts of the gradient crystal, there is a significant scatter in the frequency values of the lines corresponding to the fundamental vibrations of the crystal lattice, but at the same time, the number of lines corresponding to the fundamental vibrations of the lattice for the gradient and compositionally homogeneous LiNbO3 crystals is the same. Moreover, in the spectrum of a gradient crystal in the region of overtone processes of fundamental vibrations, significantly more lines (35 lines) are observed than in the spectrum of compositionally homogeneous crystals (15 lines). The data obtained show that the state of the defect structure of compositionally homogeneous crystals and gradient LiNbO3 crystal is significantly different. The discovered differences between the defective structure of a gradient crystal and the defective structure of a compositionally homogeneous crystal may be the reason for compensation (damping) of distortions during nonlinear optical conversion of laser radiation by a gradient crystal due to the uneven temperature distribution along the length of the crystal. In compositionally homogeneous crystals, such temperature distortions significantly limit the efficiency of nonlinear optical conversion.

Prediction of automotive body-in-white distortion in paint baking process

Thermal-induced distortion prediction of thin shell structures is a challenging task. It often involves highly nonlinear buckling behaviour, where the critical buckling temperature and post-buckling deformations are very sensitive not only to structural stiffness and boundary conditions but also minute geometric imperfections (a.k.a., “surface quality”) of the incoming parts. In the present work, novel Computer Aided Engineering (CAE) methods were developed to predict the thermal-induced distortion of automotive Body-in-White (BIW) panels during paint shop oven-baking processes. The CAE methodology consist of a set of three Finite Element Analysis (FEA) procedures, i.e., thermal-buckling mode analysis, thermo-structural analysis, and imperfection analysis. Two vehicle level case studies showed that simulations successfully predicted the thermal-induced distortion for panels such as the Body Side Outer (BSO) header. It was concluded that the distortion depends primarily on the temperature difference between the BSO and the rest of the BIW during the oven-baking process, rather than the temperatures themselves. Body panel forming quality (e.g., residual stresses and thickness thinning) and assembly dimensional quality were also found to impact the distortions.

Accelerometer-assisted computer vision data fusion framework for structural dynamic displacement reconstruction

Accurate displacement measurement provides crucial information for evaluating the structural health condition. It is important to note that both direct and indirect displacement measurement methods have their own limitations, which can be remedied by leveraging each other’s strengths. In this study, a novel accelerometer-assisted computer vision data fusion framework is developed for accurately reconstructing structural dynamic displacement. The framework does not require a specific mathematical model or prior knowledge about the data’s characteristics, allowing it to be applied more broadly across different applications without the constraints of model assumptions. The core of this framework is to integrate successive variational mode decomposition (SVMD) and Bayesian optimization approaches to adaptively determine the weight factors of the fusion components. Importantly, an enhanced optical flow approach is presented for converting pixel movement to structural displacement from natural targets. This approach can effectively reduce the selection of mis-matched points within the ROI (Region of Interest), thereby reducing drift errors. The developed framework is verified via shaking table tests of a reinforced concrete frame structure under seismic excitation. Results indicate that the developed framework excels in accurately estimating structural dynamic displacement. Compared to single-vision displacement identification results, the proposed framework demonstrates lower peak error (< 1.65 mm) and normalized root mean square error (< 0.30). Meanwhile, the reconstructed displacement, by introducing dynamic displacement component from acceleration measurement, presents a wider frequency range than the vision-based displacement.

Recommendations for empirical syndemics analyses: A stepwise methodological guide

Syndemic theory posits that co-occurring diseases interact in a manner that increases disease transmission, progression, and negative health outcomes. And that adverse socioeconomic and environmental conditions promote this disease or health condition clustering and interaction. The concept offers two important contributions to the health sciences. First, it positions socioeconomic, structural, and environmental conditions as central to disease burdens. Second, as a portmanteau – ‘syn’ for synergy and ‘demic’ for disease epidemics – syndemic theory indicates that in some cases diseases do not merely co-occur but synergistically interact to affect an outcome that is more than the accumulation of the individual disease effects. The difficulty in operationalizing these central elements has resulted in a divergence of scholarship from the centralizing principles of the theory towards a simpler accumulation perspective in which more conditions equate to worse health outcomes. In addition, all empirical syndemic assessments should include robust qualitative assessments of the dynamics, however, much syndemic scholarship focuses only on quantitative analyses. To address these issues, a five-step approach to quantitative analyses of syndemic arrangements is proposed: (1) identifying disease clusters within a defined population; (2) determining the relevant social and structural factors that support disease clustering; (3) determining if clusters are distinct by social/demographic groups within the population; (4) evaluating if the identified disease cluster contributes to worse health outcomes; and (5) assessing for synergy between clustering diseases. This stepwise strategy ensures not only a rigorous assessment of hypothesized syndemic interactions but also presents a closer alignment of scholarship with syndemics theory. As an illustration, the approach is applied to an assessment of a hypothesized HIV/cardiovascular disease syndemic in South Africa. While syndemics theory has proven valuable in guiding public health interventions and policy, progressive improvement must be made in the application of the theory to ensure that it continues to effectively inform comprehensive practice.

Модель автоматизации управления процессом обследования зданий на этапе эксплуатации

The article presents a study of the possibilities of automating the inspection processes of load-bearing building structures, with a special emphasis on the use of CRM systems with specialized modules. Practical examples of the implementation of such systems in the activities of construction organizations are analyzed. The necessity of engineering and technical inspection of buildings at all stages of their life cycle is discussed, based on the relevance of information on the technical condition of structures to ensure the safety of users. A process map has been developed covering various stages, such as data preparation, task creation, accounting and reporting documentation, using Bitrix 24. The key actions involved in each stage are identified, as well as the role and interaction of various departments of the organization. The importance of using BPMN for business process modeling is emphasized, which makes it possible to improve the management and coordination of work, reduce the risks of errors and increase the deadline for completing tasks. The work offers a systematic approach to conducting building surveys, covering key aspects of automation and process organization, which can significantly improve the quality and efficiency of surveys in the construction industry. Such modeling makes it possible to optimize the interaction between specialists, minimize the likelihood of errors and speed up the execution of work, ensuring systematization and control at all stages of the examination.

When do contemporary wildfires restore forest structures in the Sierra Nevada?

BackgroundFollowing a century of fire suppression in western North America, managers use forest restoration treatments to reduce fuel loads and reintroduce key processes like fire. However, annual area burned by wildfire frequently outpaces the application of restoration treatments. As this trend continues under climate change, it is essential that we understand the effects of contemporary wildfires on forest ecosystems and the extent to which post-fire structures are meeting common forest restoration objectives. In this study, we used airborne lidar to evaluate fire effects across yellow pine and mixed conifer (YPMC) forests of California’s Sierra Nevada. We quantified the degree to which forest structures in first-entry burned areas (previously unburned since ~ 1900s) and unburned controls aligned with restoration targets derived from contemporary reference sites. We also identified environmental conditions that contributed to more restorative fire effects.ResultsRelative to unburned controls, structural patterns in first-entry burned areas aligned more closely with reference sites. Yet, across all burn severities, first-entry wildfires were only moderately successful at meeting targets for canopy cover (48% total area) and ladder fuels (54% total area), and achieving these targets while also producing tree clump and opening patterns aligning with reference sites was less common (16% total area). Moderate-severity patches had the highest proportion of restorative fire effects (55–64% total area), while low- and high-severity patches were either too dense or too open, respectively. Our models (and publicly-available mapped predictions) indicated a higher probability of restorative effects within 1 km of previous fires, within the mid-upper climate range of the YPMC zone, and under moderate fire intensities (~ 1–2 m flame lengths).ConclusionsFirst-entry wildfires can sometimes restore structural conditions by reducing canopy cover and ladder fuels and increasing structural heterogeneity, especially within moderate-severity patches. However, these initial fires represent just one step toward restoring dry forest ecosystems. Post-fire landscapes will require additional low- to moderate-intensity fires and/or strategic management interventions to fully restore structural conditions. In yet unburned forests, managers could prioritize mechanical treatments at lower elevations, early-season burning at mid to high elevations, and resource objective wildfires in landscapes with mosaics of past wildfires.

Experimental investigation on vortex-induced vibration characteristics of the dual parallel suspenders

This study investigates vortex-induced vibrations (VIVs) on dual parallel suspenders using wind tunnel experiments and employs a two-degree-of-freedom setup for each circular cylinder to closely simulate actual structural conditions. The VIV responses of dual cylinders exhibit notable deviations and complexity due to aerodynamic interaction. Results indicate a significant shift in the VIV lock-in range towards higher values for dual cylinders, compared to single ones. Both upstream and downstream cylinders demonstrate lower maximum VIV amplitudes than the single-cylinder. The cylinders exhibit effects of negative aerodynamic damping within the VIV process, with the aerodynamic damping becoming more pronounced as amplitude increases. Additionally, the time-dependent phase relationship between the cylinders contributes to these variations in response. Further analysis of surface wind pressure distribution reveals that aerodynamic interference in dual-cylinder systems leads to intricate pressure patterns and modal behaviors.

Intelligent Assessment of Pavement Structural Conditions: A Novel FeMViT Classification Network for GPR Images

Intelligent Assessment of Pavement Structural Conditions: A Novel FeMViT Classification Network for GPR Images

Steel Structures to Withstand the Elements: What Structural Engineers Need to Know about Corrosion

While regimented design processes for load-induced effects in structures are ubiquitous, similar design processes for considering corrosion resistance are lacking. This is a critical gap in the structural engineering profession as material degradation is the most common cause of diminishing structural condition for bridges and other infrastructure exposed to the elements. This results in both safety and financial consequences. This paper addresses this gap by reviewing basic principles governing corrosion, how these corrosion principles translate to real-world environments, commonly available corrosion protection systems, long-term field data assessing corrosion in varied quantified environments and associated conclusions, and practical design and maintenance strategies for improving corrosion resistance. These concepts are connected through a proposed framework for considering corrosion as a limit state that can be applied to all structures. Detailed consideration of uncoated weathering steel (UWS) bridges is provided as a pilot material and structure type for considering corrosion as a limit state. Thoughtful application of these concepts can be used to optimize corrosion resistance, improving life-cycle costs and service lives of civil engineering structures.

Структурный подход к оценке работоспособности системы мониторинга инженерных конструкций вантового моста через Петровский канал в створе автомобильной дороги «Западный скоростной диаметр» в городе Санкт-Петербурге. Часть 2

Purpose: assessing the performance of the monitoring system for engineering structures and assessing the current state of the structures of the cable-stayed bridge across the Petrovsky Canal in the alignment of the Western High-Speed Diameter highway in the city of St. Petersburg due to the occurrence of emergency situations in which accelerometers on the pylons record values exceeding the limit. Methods: statistical data from the databases of the existing system of monitoring engineering structures is used to obtain the results. The tasks, set within the framework of the study, are accomplished by applying the theoretical methods of scientific knowledge: the analytical method, the mathematical statistics theory, induction. Results: the resulting structural approach to assessing the performance of the monitoring system for engineering structures on cable-stayed bridges makes it possible to reduce the number of false alarms of the system and assess the current state of the bridge structure. Within the framework of the III stage of the structural approach, it is proposed to develop a methodology for assessing the performance of the monitoring system for engineering structures with subsequent assessment of the current state of cablestayed bridge structures. Practical significance: the results of the work are important for construction as they expand the understanding of the features of the mechanism of soil freezing.

ANALYSIS OF THE DEFORMATION OF ROAD SURFACE CONSTRUCTION BASED ON MONITORING CLIMATIC FACTORS

The article presents the results of simulation of the deformation state of a road surface structure intended for traffic categories KR 3-4. Climatic factors such as temperature and humidity were obtained from a database collected based on the installed monitoring. The performed validation of the deformation state indicated a very good fitness of the model to the experimental results, provided that the viscoelastic model. The results indicated that the difference in pavement load time between 1 s and 1200 s in summer may result in an increase in horizontal deformation under the asphalt layer by 949%, and in winter by 74%. The calculated vertical displacement in winter after 1200 seconds of loading is equivalent to the displacement calculated after 1 second of loading the road surface in summer.

Diversidad y distribución de los helechos y licófitos de un bosque subandino del norte de los Andes

Background and aims: Ferns and lycophytes are highly diverse in Neotropical forests, and their distribution is influenced by various biotic and abiotic factors, including disturbance. This study analyzes the effect of some of these factors on the diversity of these plants in a sub-Andean forest. M&amp;M: Four transects of 400 m2 (80×5 m) were established, two in highly disturbed sites, grassland, and stream edge, and two in the forest. Each transect was divided into 16 plots where all terrestrial and epiphytic individuals were recorded. Clustering analyses were performed to recognize the presence of floristic groups, and a canonical correlation analysis was performed to identify how soil chemistry and vegetation structure affect the composition and diversity of these plants. Results: A total of 4935 individuals were found, representing 42 species. Amauropelta rudis (Kunze) Pic. Serm. (2485 individuals) and Asplenium flabellulatum Kunze (1190 individuals) were the dominant terrestrial species. The clustering and ordination analyses revealed that the plots of open sites are more related to each other than to those of the forest. Species of open sites are more correlated with a lower layer of litter, a lower height and coverage of trees or saplings, a higher concentration of aluminum and a lower concentration of sodium. Conclusions: Ferns and lycophytes are influenced by the environmental, structural and disturbance conditions of the site where they grow. Key words Disturbance, diversity, edaphic factors, multivariate analysis, pteridophytes, richness, structural factors.

A Hybrid GAN-Inception Deep Learning Approach for Enhanced Coordinate-Based Acoustic Emission Source Localization

In this paper, we propose a novel approach to coordinate-based acoustic emission (AE) source localization to address the challenges of limited and imbalanced datasets from fiber-optic AE sensors used for structural health monitoring (SHM). We have developed a hybrid deep learning model combining four generative adversarial network (GAN) variants for data augmentation with an adapted inception neural network for regression-based prediction. The experimental setup features a single fiber-optic AE sensor based on a tightly coiled fiber-optic Fabry-Perot interferometer formed by two identical fiber Bragg gratings. AE signals were generated using the Hsu-Nielsen pencil lead break test on a grid-marked thin aluminum plate with 35 distinct locations, simulating real-world structural monitoring conditions in bounded isotropic plate-like structures. It is demonstrated that the single-sensor configuration can achieve precise localization, avoiding the need for a multiple sensor array. The GAN-based signal augmentation expanded the dataset from 900 to 4500 samples, with the Wasserstein distance between the original and synthetic datasets decreasing by 83% after 2000 training epochs, demonstrating the high fidelity of the synthetic data. Among the GAN variants, the standard GAN architecture proved the most effective, outperforming other variants in this specific application. The hybrid model exhibits superior performance compared to non-augmented deep learning approaches, with the median error distribution comparisons revealing a significant 50% reduction in prediction errors, accompanied by substantially improved consistency across various AE source locations. Overall, this developed hybrid approach offers a promising solution for enhancing AE-based SHM in complex infrastructures, improving damage detection accuracy and reliability for more efficient predictive maintenance strategies.

ANALYSIS OF MODERN SCIENTIFIC AND PRACTICAL RESEARCH IN THE FIELD OF WATER DISTRIBUTION SYSTEM

Solving the problem of ensuring the reliable functioning of drainage systems is important not only for Ukraine, but also for scientists around the world. Since these systems are critically important for life support, their uninterrupted operation is of strategic national importance. The issue of preservation and restoration of existing underground communications is gaining particular relevance due to increased environmental requirements. To protect groundwater from contamination with aggressive reagents, it is important to understand the reasons for the destruction of underground communications structures and effective methods of their repair. The article analyzes scientific works related to the problems of ensuring the trouble-free operation of objects that are part of the complex of constructions of sewer tunnels of the city. Grouped according to the direction of research work: research on the corrosion process in water drainage networks; analysis of modern ones; materials, laboratory tests; technologies for restoring drainage networks. Analysis of studies of the condition of structures of objects; research of materials and methods of repair and restoration of sewage tunnels and inspection shafts, which are currently used with high efficiency in domestic and foreign practice; development of technological and organizational solutions and restoration of destroyed sewage structures of drainage networks. The analysis of the researches of domestic scientists showed that the sewer tunnels of large cities of Ukraine are worn out as a result of long-term operation, ineffective solutions to protect structures from the influence of an aggressive environment, low-quality materials and structures used during construction. Restoring normative operational characteristics, increasing the durability of sewage tunnels is a costly and technically complex task, the solution of which is urgently needed to prevent accidents, including those with serious environmental consequences. Existing modern technologies of work performance, materials and structures used for repair and restoration works with different efficiency solve these problems, at the same time, the need to reduce costs for repair and restoration works requires the search for cost-effective materials, structures and methods of work performance. The analysis of the conducted studies shows that the problem of increasing the durability of sewage network structures should be solved comprehensively, taking into account the current situation.

Corrosion-mechanical destruction of bainite structures in oilfield environments

The main direction in solving the problem of increasing the reliability of field equipment, is the creation of new steels with higher resistance to corrosion-mechanical destruction. Currently, to produce oil and gas pipeline systems, low-carbon, low-alloy steels are used, in which lath carbide-free bainite is formed when quenched in water. Such a structure provides a combination of high strength and resistance to brittle fracture. However, issues of increasing corrosion resistance are still open. The purpose of this work is to identify the structural condition of low-carbon, low-alloy, pipe steels, providing a combination of high mechanical properties with increased corrosion resistance in oilfield environments. The studies were carried out on the latest generation 08KhFA, 08KhFMA and 05KhGB steels, most popular when manufacturing oil and gas pipelines. Samples for the study were cut from the pipes and quenched from the austenite region in water, which formed the structure of lath carbide-free bainite. The quenched samples were tempered at temperatures of 200, 300, 400, 500, 600, and 700°C. To identify the relationship between the morphology of bainite structures and their properties, the samples after quenching and tempering at each temperature, were subjected to metallographic analysis, X-ray diffraction analysis, mechanical tests, and corrosion resistance tests. The work shows the sequence of structure transformation, temperature ranges of phase and structural transformations, changes in mechanical properties, and corrosion resistance that occur during tempering of lath carbide-free low-carbon bainite. It is shown that tempering of lath carbide-free bainite (08KhFA, 08KhMFA and 05KhGB steels) does not affect the rate of carbon dioxide corrosion. It has been found that medium tempering forms the structural condition of carbide-free low-carbon lath bainite providing a combination of high mechanical properties and high corrosion resistance in oil field environments. For each of the steels under study, the authors give recommended heat treatment modes.

System identification for structural condition assessment: Application to critical neoclassical monuments in Nepal

This paper presents structural condition assessment of some critical neoclassical monuments in Nepal using nonparametric and parametric system identification techniques. Neoclassical buildings in Nepal house critical administrative units. Structural condition assessment of such buildings is therefore important for the safety of their occupants and interrupted function during and after major earthquakes. The historical and cultural values of such monuments necessitate regular structural assessment for maintenance, repair, and preservation. Dynamic characteristics such as natural vibration frequencies of structures provide valuable insights on their structural condition. While numerical models are commonly used to estimate eigen frequencies of structures, they are associated with large uncertainties in massive monuments with complex structural and geometrical configurations. Noninvasive dynamic identification techniques provide an alternative means in such structures. Ambient vibration records from six neoclassical monuments in the Kathmandu Valley, Nepal are used in this study to estimate vibration frequencies of the structures in different states. The structures were damaged during the 2015 Gorkha earthquake, and subsequently retrofitted. Changes in vibration frequencies before and after retrofitting provide useful insights on structural improvement through retrofitting. Input-output and output-only system identification techniques are tested to simplify the structural condition assessment approach. We conclude that the state space system identification can stably quantify dynamic properties so stiffness variation can be confidently extracted, which is the key application for noninvasive structural system identification. Also, using minimum number of sensors, we captured damage aggravation deploying the modal assurance criterion. The outcomes indicate that structural condition assessment of complex structures is possible using a limited number of sensors for circumstances such as damage aggravation to temporal variation (evolution/reduction) of dynamic characteristics.

Technical aspect of the operation of accelerometers as composition of a system for monitoring engineering structures of a cable-stayed bridge over the Petrovsky canal in the construction of the Western Speed Diameter highway in Saint Petersburg

Aim. This study analyzes the current monitoring system for the engineering structures of a cable-stayed bridge across the Petrovsky Canal, part of the Western High-Speed Diameter highway in St. Petersburg, focusing on emergency situations where accelerometers on pylons record values that exceed limits. Methods and Materials. The study utilizes statistical data from existing monitoring system databases. The tasks, set within the framework of the study, are accomplished by applying theoretical scientific methods including analytical techniques, mathematical statistics, and induction. Results. The analysis presents an overview of the current system used for monitoring engineering structures and highlights issues related to emergency situations in which accelerometer readings exceed threshold values. This study proposes a method for assessing the reliability of the monitoring system by classifying the data obtained from the accelerometer into two groups. The research identifies the need for further investigations to understand the root causes of these issues. Conclusion. Тhe results can assist in the design and installation of monitoring systems of the engineering structures for cable-stayed bridges, as well as for modernization and optimization of existing monitoring systems to improve the quality of structural technical condition assessments.

Study on the 2D equivalent nonlinear dynamics simulation model related to high speed precision bearing and spindle

The stiffness and contact stress of the bearing spindle system are the key factors affecting its machining accuracy and service life under the condition of high-speed service, which will be affected by different structural parameters and service conditions. It is essential to establish an efficient and accurate computational simulation model to understand the influence of complex factors on the nonlinear dynamic characteristics of the bearing spindle system. Firstly, in the paper, a 2D axisymmetric finite element model of the bearing, aims at the relationship between stiffness and contact stress of the bearing under high-speed service, has been built based on a classical dynamic analysis model and the reversed method of material parameters of equivalent rolling balls. Additionally, for the BT30 spindle, the 2D axisymmetric finite element model of the bearing spindle system also has been built and applied in mechanical analysis of spindle under different conditions of assembly and service, based on the bearing model. The results show that the axial force of bearings decreases as the rotational speed increases, and an augmentation in speed will result in a reduction in the axial stiffness of the BT30 spindle. In addition, the maximum contact stress exhibits a slight decline as the rotational speed increases. Furthermore, with an escalating preload, the stiffness and contact stress of the spindle undergo substantial increments, however, these parameters will cease to alter once a certain threshold is reached.