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Stress state evaluation in axially loaded structural members is significant for sustaining and preserving the service life of buildings. While successful monitoring furnishes staunch information on the health, integrity, safety and serviceability of structures, maintaining the structural performance of a building with time significantly depends on assessing the occurrence. Variations in the stress in axially loaded members may occur in masonry buildings or space structures caused by different conditions and human-induced factors. In the last decades, numerous nondestructive methods have been generated to furnish practical means for identifying axial load in the tie-rods of masonry buildings and in the structural members of space structures. Significant effort has been put into dynamic-based approaches, which make use of the vibrational response of the monitored member to investigate its condition and evaluate the axial load. In particular, wide laboratory and field tests have been executed worldwide, resulting in several findings. Meanwhile, with flourishing sensing technology and computing power, Artificial Intelligence (AI) applications, such as hybrid methods, optimization techniques and deep learning algorithms, have become more practicable and widely used in vibration-based axial stress prediction, with efficiency and, frequently, with strict precision. While there have been various manuscripts published on dynamic-based axial stress evaluation, there are no works in which the passage from traditional methods to combinations with AI approaches have been illustrated. This article aims to address this gap by introducing the highlights of the traditional methods, and furnish a review of the applications of AI techniques used for nondestructive-based axial stress prediction in tie-rods and structural members. Conclusions, including further studies and field developments, have also been mentioned at the end of the article.

With the development of fiber optical technologies, fiber Bragg grating (FBG) sensors are frequently utilized in structural health monitoring due to their considerable advantages, including fast response, electrical passivity, corrosion resistance, multi-point sensing capability and low-cost production, as well as high accuracy and resolution over a long period. These characteristics allow FBG to be a proper alternative sensing element for displacement measurements. In this article, the recent sensing advances and principles of detection of FBG-based displacement sensors are illustrated. Specifically, the latest FBG-based displacement technologies are examined from three principles of detection, i.e., wavelength, intensity and phase signal demodulation. Regarding wavelength detection methods, the problem related to the cross-sensitivity can significantly be reduced depending on the new type of cantilever–FBG-based sensing developed. Vice versa, only the packaging method of FBG prestressed between two fixed ends can still avoid the chirp phenomenon in the reflection spectrum. Moreover, to attenuate the influence of temperature variations on the accuracy of FBG displacement sensors, specific temperature self-compensation structures were successfully designed according to the concepts of phase signal demodulation. In future investigations, different elastic structures and gratings manufactured through special fibers and new methodologies for temperature compensation will still highly refine the efficiency of FBG-based displacement sensors.

Prestressing methods were used to realize long-span bridges in the last few decades. For their predictive maintenance, devices and dynamic nondestructive procedures for identifying prestress losses were mainly developed since serviceability and safety of Prestressed Concrete (PC) girders depend on the effective state of prestressing. In fact, substantial long term prestress losses can induce excessive deflections and cracking in large span PC bridge girders. However, old unsolved problematics as well as new challenges exist since a variation in prestress force does not significantly affect the vibration responses of such PC girders. As a result, this makes uncertain the use of natural frequencies as appropriate parameters for prestress loss determinations. Thus, amongst emerging techniques, static identification based on vertical deflections has preliminary proved to be a reliable method with the goal to become a dominant approach in the near future. In fact, measured vertical deflections take accurately and instantaneously into account the changes of structural geometry of PC girders due to prestressing losses on the equilibrium conditions, in turn caused by the combined effects of tendon relaxation, concrete creep and shrinkage, and parameters of real environment as, e.g., temperature and relative humidity. Given the current state of quantitative and principled methodologies, this paper represents a state-of-the-art review of some important research works on determining prestress losses conducted worldwide. The attention is principally focused on a static nondestructive method, and a comparison with dynamic ones is elaborated. Comments and recommendations are made at proper places, while concluding remarks including future studies and field developments are mentioned at the end of the paper.

In this work, two new face structures of the open-air protection fence were investigated, where a method was proposed for analyzing the condensation of water vapor in the protection fence to search for a condensation zone. Another method for calculating the amount of condensed vapor in a multiwall protection fence with closed gap spacings was proposed. The analytical results illustrated that the magnitude of the range of temperature variations of the worked-out structures with gap spacings and without heat-reflecting screens was 7.14% lower, while the existence of heat-reflective screens reduced this value to 27.14%. The investigation of the water vapor transmission magnitude demonstrated that the steam permeability strength of the interior side and retaining walls of the developed buildings amounts to the standard one, while the usage of a locked air space with a thermo-reflective panel allows the movement of the appropriate condensing region over the external face of the fencing. Mass analysis of the precipitated vapor during the heating time of 1 m2 of the retaining wall showed that in face structures in closed gap spacings with heat-reflective screens, the mass of the precipitated vapor was 24.8% greater relative to that of the face without heat-reflective screens. Moreover, the examination of the absence of distillation in the oxygenated gap spacing proved that, in the gap spacing in the considered face structures, the condensate does not fall out such that there is no aggregation of humidity according to the annual balance. Furthermore, the drying time of the face structure with heat-reflecting screens was 17.9% longer than that of the traditional one. The research results can complement the works performed earlier by the authors, as well as be applied in the engineering and construction of buildings to save thermal power, considering the climatic features of the development region.

This article analyzes the convergence of the obtained values as a result of the authors’ earlier experimental and theoretical studies. On the basis of the correlations, it was found that the analyses of a traditional cylindrical steel tank without a steel wire strand wrapping and with a filling level of zero by a liquid showed a difference in natural vibration frequencies of 8.4%, while with half and maximal filling by a liquid showed differences equal to 3.2% and 6.2%, respectively. Vice versa, analyses of a cylindrical steel tank with a steel wire strand winding pitch of a = 3d and with a filling level of zero by a liquid showed a difference in natural vibration frequencies of 8.1%, while with half and maximum filling by a liquid and with the same steel wire strand winding pitch showed differences of 10.1% and 5.9%, respectively. Conversely, analyses of a cylindrical steel tank with a steel wire strand winding pitch of a = d and in absence of filling level amounted to a difference of 5.5%, while with half and maximum filling and with the same steel wire strand winding pitch of a = d, differences of 1.6% and 1.4% were, respectively, achieved. Based on the aforementioned results, the general difference between experimental and theoretical vibration frequencies showed up to 10%, which is a satisfactory result of convergence. The obtained findings of this research can be used by engineers and technical workers in the industries of various fields, research institutes and professional companies in designing new earthquake-resistant steel tanks and strengthening existing ones. Conclusions were then mentioned at the end of the article.

Based on a reduced model of a linear section of a steel gas pipeline between four supports and with a crack-like through defect, ANSYS FE software is used in this study to develop numerical approaches regarding three key parameters of a composite bandage in the form of a circular lining: the type of composite material and the length and thickness of the composite lining. The approach for assessing the static strength of a damaged section of a steel pipeline with a composite lining that is subjected to internal pressure allows for the determination of the optimal thickness of the composite lining itself, which is equal to the indicator “50.0% to 62.5%” of the pipe thickness. Furthermore, the approach for assessing the dynamic strength and analyzing the possible destruction of the reinforced damaged section of a pipeline experiencing an increase in internal pressure allows for the determination of the optimal length of the composite lining, which, in turn, should be at least 241.2 mm. This work also considers cases when there is no internal pressure and the steel pipeline is subjected to critical pressure. It is found that the frequency spectrum of pipeline oscillations without a composite lining is higher than that with a composite lining. The difference between the corresponding dynamic oscillations increases with the thickness or the length of the composite lining. In the absence of internal pressure, all frequencies of the steel pipeline with a crack closed by a composite lining are paired. This pairing is disrupted when the pipeline is subjected to critical internal pressure, and the difference between its oscillation frequency spectrum without and with a composite lining increases. In this case, the oscillation modes significantly differ from those of the same pipeline structure when unloaded. The results ensure the optimal stress distribution in the defect area of a steel pipeline wall and improve the reliability and safety of pipelines under seismic actions. The approach for increasing dynamic strength and eliminating defects can be applied to pipelines with a large diameter regardless of the causes and geometric dimensions of the defects. Moreover, this approach to increasing the strength can be used by various industries and/or institutes which work on the design of new, earthquake-resistant, reinforced pipelines.

This article presents one part of a study on the dynamic deformation and fracture of sections of steel gas pipelines with an external crack-like defect under the action of internal pressure. This work was performed on the basis of finite-element simulations using a cylindrical shell model executed by ANSYS-19.2 on the example of the section of the steel gas pipeline “Beineu–Bozoy–Shymkent” in the Republic of Kazakhstan. The propagation of the incipient crack-like defect along the pipeline and the resulting dynamic fracture in its tip area were investigated. The options of pipeline loading by working and critical internal pressure were both considered. It was found that, within the time of 1.0 ms, the formed crack expanded in the circumferential direction up to the maximum value, which depended on the value of the internal pressure. A further growth of cracks occurred along the longitudinal direction. At the operating pressure, the initial length of the crack increased by a factor of 5.6, while the equivalent stresses increased by a factor of 1.53 within 3.5 ms. Within the time of 3.75 ms, the equivalent stresses stopped growing due to the gas decompression. Specifically, there was a stop to the crack growth along the longitudinal direction. Vice versa, at the maximum pressure, the pipeline fracture did not change qualitatively, while at the time of the process, it decreased up to 3.5 ms. The finite-element results of the stress–strain state and pipeline fracture in the crack tip area at the working pressure showed that, within the time of 1.0 ms, the distance between the crack walls reached 23 mm at the free edge. Conversely, within the time periods of 2.25 and 3.5 ms, it increased two and three times, respectively. The crack elongation in the longitudinal direction occurred 5.8 times with time. Together, within the time of 3.5 ms, the equivalent stresses increased twice, after which the growth of the crack stopped due to the gas decompression. Moreover, studies on the growth of the crack-like defect in its tip area at the maximum pressure showed that additional considerations on the pressure on the crack edges led to an increment of 3.6% of the crack length. The results of this work can be used for the development of measurements for operating gas pipelines in the field of structural reinforcement.

This work treats a finite‐element analysis of the oscillations in damaged pipeline sections reinforced with a composite wrap performed by ANSYS software when the thickness of the composite wrap was 2.0, 3.0, and 4.0 mm, while the length of the wrap was 400, 600, and 800 mm, respectively. The outcome showed that to compensate for the stress concentration in the damaged zone of a pipeline with a thickness between 11.9 and 14.3 mm, the thickness of the composite wrap should be 2 ÷ 4 mm, that is, not lower than 17% of the original pipeline thickness at thinning and not lower than 34% of the original pipeline thickness at large cracks. An increment in the pipeline thickness from 11.9 up to 14.3 mm with a reinforced composite lining leads to an increment in the first oscillation frequency not higher than 0.1%. The lowest fundamental frequency was at a pipeline with lining located at the restrained supports, while the highest frequency was between two free‐moving supports in the middle span. The difference between the first frequencies did not exceed the percentage of 4%. By applying a composite lining with a length of 20% of the pipeline length between a restrained support and a longitudinally movable one and a thickness of 33.6% of the nominal pipeline thickness, we were able to increase the frequency spectrum of the oscillations in comparison with the unreinforced pipeline. Therefore, for the fundamental frequency, this increment was equal to 13.9% for the operating pressure and almost four times for the critical one. Consequently, the developed approach can be used as an adjustment method for damaged pipeline sections characterized by low critical frequencies.

This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure. This study establishes the use of scaled-down experimental models for assessing the dynamic strength of damaged pipeline sections reinforced with wire wrapping or composite sleeves. A generalized dynamic model is introduced for numerical simulation to evaluate the effectiveness of reinforcement techniques. The model incorporates the elastoplastic behavior of pipe and wire materials, the influence of temperature on mechanical properties, the contact interaction between the pipe and the reinforcement components (including pretensioning), and local material failure under transient internal pressure. Based on these parameters, a finite element model was developed using ANSYS 19.2 to enable parametric studies. The accuracy of the proposed model was verified by comparing the simulation results with the experimental findings. Pipeline section samples containing non-penetrating longitudinal cracks were subjected to comparative analyses and transient pressure until critical failure. The unreinforced and steel wire-wrapped sections were investigated. The results confirm the feasibility of applying the computational model to study the dynamic strength of reinforced damaged pipe sections. Furthermore, pipelines with longitudinal cracks reinforced using circular composite overlays with orthotropic mechanical properties were examined, and recommendations are provided for selecting the geometric parameters of such overlays.