作者机构：
[Han, Yanqun] School of Civil Engineering, Central South University, Changsha 410075, Hunan, PR China;[Peng, Xulong] School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, Hunan, PR China
通讯机构：
[Xulong Peng] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, Hunan, PR China
关键词：
Approximate temperature;Convective-radiative fin;Fin efficiency;Nonlinear heat transfer problem;Temperature-dependent thermal conductivity
摘要：
This article studies the thermal performance of a moving fin with temperature-dependent thermal conductivity in a convective and radiative environment. It corresponds to a nonlinear heat transfer problem related to the nonlinear ordinary differential equation (NODE) for the unknown temperature excess. The NODE is solved by converting it to a nonlinear Fredholm integral equation. An approximate temperature distribution is determined in the quadratic form for arbitrary values of the Biot and Peclet numbers. A comparison of our results with the previous ones indicates satisfactory accuracy of the obtained solution. The fin efficiency is also given explicitly in terms of prescribed parameters and calculated numerically. The heat dissipation to the surrounding medium due to convection and radiation is analyzed for various speeds of a moving fin. The influences of thermal conductivity, heat convection, radiation, and moving speed of the fin on the temperature distribution and thermal performance are elucidated.
This article studies the thermal performance of a moving fin with temperature-dependent thermal conductivity in a convective and radiative environment. It corresponds to a nonlinear heat transfer problem related to the nonlinear ordinary differential equation (NODE) for the unknown temperature excess. The NODE is solved by converting it to a nonlinear Fredholm integral equation. An approximate temperature distribution is determined in the quadratic form for arbitrary values of the Biot and Peclet numbers. A comparison of our results with the previous ones indicates satisfactory accuracy of the obtained solution. The fin efficiency is also given explicitly in terms of prescribed parameters and calculated numerically. The heat dissipation to the surrounding medium due to convection and radiation is analyzed for various speeds of a moving fin. The influences of thermal conductivity, heat convection, radiation, and moving speed of the fin on the temperature distribution and thermal performance are elucidated.
摘要：
Critical shear stress and erosion rate are two key factors for the prediction of the incipient motion of sediment and the transport of sediment. Seabed seepage can significantly alter the pore pressure gradient within the soil and the hydrodynamics around the surface of the seabed, further affecting erosion processes. Previous studies attempted to theoretically clarify the effect of the seepage force on sediment incipient motion. In this study, a newly designed erosion-seepage system (ESS) that considers the effect of seepage under steady or oscillatory flow is used to simulate the erosion process. Through the designed ESS, the erosion height per unit time was measured directly on the Yellow River sand, and the upward seepage force was applied at the bottom of the soil sample in the process. Then, the relationship between the erosion rate and seepage was established.The experimental results show that upward seepage reduces the critical shear stress of the sand bed and increases the erosion rate of the soils under both steady flow and oscillatory flow conditions. The erosion coefficients in the erosion models decrease with increasing seepage gradient. The effect of seepage on erosion is more obvious when the flow velocity of the steady stream is large, while the effect of seepage on erosion is relatively small under the oscillatory state with a shorter period. However, when violent erosion of soil samples occurs, seepage under both flow conditions greatly increases the erosion rate.
摘要：
A new method was proposed for predicting residual stress in light alloys using truncated conical indentation. In this method, a truncated conical indenter with a cone angle of 120°, insensitive to edge-chamfer and friction effects, was used to test the residual stress of light alloys. Selecting the ratio of indentation work between stressed and unstressed specimens as an analytical parameter, a dimensionless truncated conical indentation (TCI) model related to the ratio of indentation work between stressed and unstressed, material properties, and normalized residual stress was established via dimensional analysis and numerical calculations. The TCI model could predict equi-biaxial residual stress and uniaxial residual stress, and its accuracy was verified in a wide range of light alloys with varying residual stress by numerical simulation. The stability of the TCI model is verified numerically by introducing errors in material parameters. Truncated conical indentation tests were conducted on cruciform specimens and rectangular specimens respectively made of three aluminum alloys. The results exhibited the residual stress predicted by proposed method agrees well with the applied stress, and the relative errors between them were within ±10 % in most cases.
A new method was proposed for predicting residual stress in light alloys using truncated conical indentation. In this method, a truncated conical indenter with a cone angle of 120°, insensitive to edge-chamfer and friction effects, was used to test the residual stress of light alloys. Selecting the ratio of indentation work between stressed and unstressed specimens as an analytical parameter, a dimensionless truncated conical indentation (TCI) model related to the ratio of indentation work between stressed and unstressed, material properties, and normalized residual stress was established via dimensional analysis and numerical calculations. The TCI model could predict equi-biaxial residual stress and uniaxial residual stress, and its accuracy was verified in a wide range of light alloys with varying residual stress by numerical simulation. The stability of the TCI model is verified numerically by introducing errors in material parameters. Truncated conical indentation tests were conducted on cruciform specimens and rectangular specimens respectively made of three aluminum alloys. The results exhibited the residual stress predicted by proposed method agrees well with the applied stress, and the relative errors between them were within ±10 % in most cases.
摘要：
With the increase of the density of subway line in big cities, it is common for newly built shield tunnels to cross beneath the existing pile foundations at short distances. When the disturbance generated during the construction of the shield tunnels is transmitted to the bearing stratum of the existing pile tip, a punching shear failure may occur in the bearing stratum. To study the evolution process and final form of the punching shear failure of the bearing stratum, a scaled model test based on the Particle Image Velocimetry (PIV) technology is designed. By using PIV technology to analyze deformation images of the bearing stratum, the failure range and shape of the bearing stratum between the pile tip and tunnel induced by excavation are obtained. Using the failure shape of the bearing stratum provided by the model test, a theoretical failure mechanism based on the spatial discretization technique is constructed. The limit analysis theorem is employed here to calculate the theoretical solution of the punching shear failure surface of the bearing stratum. The good agreement of the failure range for the bearing stratum between the model test and theoretical result indicates that the model test presented here is effective.
With the increase of the density of subway line in big cities, it is common for newly built shield tunnels to cross beneath the existing pile foundations at short distances. When the disturbance generated during the construction of the shield tunnels is transmitted to the bearing stratum of the existing pile tip, a punching shear failure may occur in the bearing stratum. To study the evolution process and final form of the punching shear failure of the bearing stratum, a scaled model test based on the Particle Image Velocimetry (PIV) technology is designed. By using PIV technology to analyze deformation images of the bearing stratum, the failure range and shape of the bearing stratum between the pile tip and tunnel induced by excavation are obtained. Using the failure shape of the bearing stratum provided by the model test, a theoretical failure mechanism based on the spatial discretization technique is constructed. The limit analysis theorem is employed here to calculate the theoretical solution of the punching shear failure surface of the bearing stratum. The good agreement of the failure range for the bearing stratum between the model test and theoretical result indicates that the model test presented here is effective.
作者：
Zhenhao Zhang;Guoqing Wei;Zhe Zeng;Fengwei Teng
期刊：
ASCE-ASME J Risk and Uncert in Engrg Sys Part B Mech Engrg,2025年11(3):031205 ISSN：2332-9017
作者机构：
[Guoqing Wei; Zhe Zeng; Fengwei Teng] School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, China;School of Architecture Engineering, Beibu Gulf University, Qinzhou 535011, China;[Zhenhao Zhang] School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>School of Architecture Engineering, Beibu Gulf University, Qinzhou 535011, China
关键词：
random waves;Wiener process;safety threshold;wave period;anti-overturning;capsizing probability
摘要：
This paper investigates the impact of threshold-crossing events on ship capsizing through a probabilistic model that predicts random wave heights. Utilizing statistical data from wave height observations, this paper proposes that random waves can be approximated and modeled using the Wiener process, employing autocorrelation function identification and probabilistic statistical verification methods. The threshold-crossing duration of a random wave is just the period of the wave exceeds a given threshold, which can reflect the frequency property of the stochastic sea waves. And the probability distribution of the period can theoretically be determined using the derived probability density function for the time interval between any two adjacent crossings of the Wiener process and a threshold. Based on the above theories, the capsizing probabilities of a civil ship sailing in different wave areas are analyzed under different safety thresholds considering certain ratios of the ship's intrinsic period and wave period. The research results can provide a reference for the anti-overturning design of the ships under the action of random waves.
摘要：
The solid propellant is a particle-reinforced material with significant tension-compression asymmetry. Based on the constant-speed tensile test, constant-speed compression test, and cross-sectional SEM scanning test, this study investigated the differences in the mechanical properties of the HTPB propellant under tensile and compressive loading and the underlying mechanisms. The results show that the tensile strength of HTPB propellant is much smaller than compressive strength. According to the SEM test results of the failure surface, the tensile mechanical properties of the propellant are mainly affected by matrix, and the influence of particles on the mechanical properties is more obvious during the compression process. According to test data, a tension-compression integrated nonlinear constitutive model was constructed, and its application in simulation calculation was realized. The results show that the theoretical, simulation calculation and test results are in good agreement. At 15% strain, the maximum error between the theoretical results and the experimental curve is 9.1% and 4.8% respectively in the process of tension and compression. Therefore, the model can accurately describe the stress-strain relationship of HTPB propellant under different strain rates of tensile and compression. This model can provide theoretical support for accurately evaluating the structural integrity of SRMs.
作者机构：
[Song, Jun; Wang, Xiangjun; Li, Chunguang] School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, China;Elite Engineering School, Changsha University of Science & Technology, Changsha 410114, China;State Key Laboratory of Disaster Prevention & Reduction for Power Grid, Changsha University of Science & Technology, Changsha 410114, China;[Li, Kai] School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>Elite Engineering School, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>State Key Laboratory of Disaster Prevention & Reduction for Power Grid, Changsha University of Science & Technology, Changsha 410114, China;[Han, Yan] School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>Elite Engineering School, Changsha University of Science & Technology, Changsha 410114, China
通讯机构：
[Kai Li] S;School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>Elite Engineering School, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>State Key Laboratory of Disaster Prevention & Reduction for Power Grid, Changsha University of Science & Technology, Changsha 410114, China
摘要：
Nonlinear flutter has attracted wide attention due to the bottleneck caused by linear flutter theory on flutter-resistant design of super-long-span bridges. The longer the span, the more closely spaced the natural modes, which may cause competition among flutter-modes in a nonlinear flutter, but it is rarely reported so far. To this end, this study experimentally investigates the 3D nonlinear flutter characteristics of a long-span suspension bridge with closely spaced natural modes based on full-bridge aeroelastic model wind tunnel tests. Since there are two unstable flutter-modes within the interested post-critical regime and thus various complex but interesting flutter-modes competition processes were observed, such as continuous modes competition where the vibration amplitude evolution exhibits various different types of “sawtooth” shapes during stable vibration stages. Meanwhile, the complex nonlinear bifurcation behaviors caused by modes competition were also observed. The evolutionary characteristics of flutter-modes competition are analyzed in detail and relevant mechanisms are discussed. As the wind speed increases, the flutter of the studied bridge mainly undergoes a transition from being dominated by the symmetric mode to being dominated by the antisymmetric mode, accompanied by a continuous modes competition zone in between as a transitional zone. The results show that the continuous modes competition will result in a decrease in the maximum amplitude RMS of the full-span, which is beneficial for the structure. But it may also lead to a transient increase in the maximum amplitude of the full-span due to the coupling vibration shape formed by the two significant flutter-modes, which may be bad for the structure.
Nonlinear flutter has attracted wide attention due to the bottleneck caused by linear flutter theory on flutter-resistant design of super-long-span bridges. The longer the span, the more closely spaced the natural modes, which may cause competition among flutter-modes in a nonlinear flutter, but it is rarely reported so far. To this end, this study experimentally investigates the 3D nonlinear flutter characteristics of a long-span suspension bridge with closely spaced natural modes based on full-bridge aeroelastic model wind tunnel tests. Since there are two unstable flutter-modes within the interested post-critical regime and thus various complex but interesting flutter-modes competition processes were observed, such as continuous modes competition where the vibration amplitude evolution exhibits various different types of “sawtooth” shapes during stable vibration stages. Meanwhile, the complex nonlinear bifurcation behaviors caused by modes competition were also observed. The evolutionary characteristics of flutter-modes competition are analyzed in detail and relevant mechanisms are discussed. As the wind speed increases, the flutter of the studied bridge mainly undergoes a transition from being dominated by the symmetric mode to being dominated by the antisymmetric mode, accompanied by a continuous modes competition zone in between as a transitional zone. The results show that the continuous modes competition will result in a decrease in the maximum amplitude RMS of the full-span, which is beneficial for the structure. But it may also lead to a transient increase in the maximum amplitude of the full-span due to the coupling vibration shape formed by the two significant flutter-modes, which may be bad for the structure.
期刊：
Journal of Materials in Civil Engineering,2025年37(5):04025118 ISSN：0899-1561
通讯作者：
Jianxin Peng
作者机构：
[Jianren Zhang] Professor, Dept. of Bridge Engineering, School of Civil Engineering, Changsha Univ. of Science and Technology, No. 960, Section 2, Wanjiali South Rd., Changsha, Hunan 410114, China;[George Vasdravellis] Professor, Dept. of Sustainable Built Environment, Heriot-Watt Univ., Edinburgh EH14 4A, UK;[Ying Chai] Ph.D. Candidate, Dept. of Bridge Engineering, School of Civil Engineering, Changsha Univ. of Science and Technology, No. 960, Section 2, Wanjiali South Rd., Changsha, Hunan 410114, China;[Jianxin Peng] Professor, Dept. of Bridge Engineering, School of Civil Engineering, Changsha Univ. of Science and Technology, No. 960, Section 2, Wanjiali South Rd., Changsha, Hunan 410114, China
通讯机构：
[Jianxin Peng] P;Professor, Dept. of Bridge Engineering, School of Civil Engineering, Changsha Univ. of Science and Technology, No. 960, Section 2, Wanjiali South Rd., Changsha, Hunan 410114, China
摘要：
Bridge steel, frequently employed in cross-sea bridge construction, exhibits excellent weldability, superior strength, and toughness. The service life and stability of steel structures are influenced by the presence of corrosive ions within marine environments, necessitating an in-depth examination of the corrosion mechanisms affecting bridge steel. In this study, Q370qD bridge steel was subjected to heat treatment to evaluate the influence of microstructural variations on its corrosion behavior. The microstructure of untreated steel (alloy F) predominantly consists of granular ferrite. Subsequent high-temperature heat treatment induces a partial transformation in the steel microstructure (alloy A), yielding lath carbide-free bainite. Post-immersion tests show both alloy surfaces densely covered with γ - FeOOH , α - FeOOH , and a mixture of Fe 3 O 4 and Fe 2 O 3 . Over time, γ - FeOOH undergoes partial conversion into the more stable α - FeOOH form, enhancing the protective barrier against the matrix for both alloys. Alloy F exhibits a significant reduction in corrosion rate compared to alloy A. The proportion of α - FeOOH in alloy A initially decreases then increases with prolonged exposure, while in alloy F, it consistently rises. The corrosion resistance of alloy A surpasses that of alloy F, which is attributed to the lath-shaped carbide-free bainite’s effectiveness in obstructing Cl − penetration and thereby improving corrosion resistance.
作者机构：
[Wei Wang; Xie-dong Zhang; Ying-qi Liu] School of Transportation and Logistics Engineering, Wuhan University of Technology, Wuhan 430063, China;[Hong-xu Wang] School of Engineering and Technology, The University of New South Wales, Canberra, ACT 2600, Australia;[Bai Zhang] School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China
通讯机构：
[Ying-qi Liu] S;School of Transportation and Logistics Engineering, Wuhan University of Technology, Wuhan 430063, China
摘要：
The current understanding of the shear behavior of double embedded nuts bolted connectors (DENBCs) in steel-fiber reinforced concrete (SFRC) remains unclear, particularly when DENBCs are embedded in the negative moment region (NMR). Two types of push-off test specimens were designed to investigate the differences in shear performance of DENBCs in the positive and negative moment regions of steel-SFRC composite beams. The experimental parameters primarily included bolt diameter, bolt grade, steel fiber volume content, and concrete type and strength. Compared to the failure mode of push-off specimens in the positive moment region (PMR), the concrete slabs in the NMR exhibited more pronounced crack development due to the influence of the tensile stress field. Adding steel fibers in normal-weight concrete (NC) and increasing fiber volume content effectively suppressed the initiation and propagation of cracks. The uplift of DENBCs was more noticeable in the NMR compared to the PMR. The steel fiber volume content had a marginal impact on bolt shear capacity but significantly enhanced ductility. Bolt shear capacity saw augmentation with higher concrete strength, bolt diameter, and grade. The shear resistance of DENBCs in the NMR exhibited lower values than in the PMR. Finite element (FE) models, validated through test data, were utilized to perform parametric studies encompassing concrete strength, bolt pretension, diameter, and bolt tensile strength. Based on the experimental and FE findings, practical design recommendations were formulated to predict the shear capacity and the load-slip response of DENBCs in the PMR and NMR of steel-SFRC composite beams.
The current understanding of the shear behavior of double embedded nuts bolted connectors (DENBCs) in steel-fiber reinforced concrete (SFRC) remains unclear, particularly when DENBCs are embedded in the negative moment region (NMR). Two types of push-off test specimens were designed to investigate the differences in shear performance of DENBCs in the positive and negative moment regions of steel-SFRC composite beams. The experimental parameters primarily included bolt diameter, bolt grade, steel fiber volume content, and concrete type and strength. Compared to the failure mode of push-off specimens in the positive moment region (PMR), the concrete slabs in the NMR exhibited more pronounced crack development due to the influence of the tensile stress field. Adding steel fibers in normal-weight concrete (NC) and increasing fiber volume content effectively suppressed the initiation and propagation of cracks. The uplift of DENBCs was more noticeable in the NMR compared to the PMR. The steel fiber volume content had a marginal impact on bolt shear capacity but significantly enhanced ductility. Bolt shear capacity saw augmentation with higher concrete strength, bolt diameter, and grade. The shear resistance of DENBCs in the NMR exhibited lower values than in the PMR. Finite element (FE) models, validated through test data, were utilized to perform parametric studies encompassing concrete strength, bolt pretension, diameter, and bolt tensile strength. Based on the experimental and FE findings, practical design recommendations were formulated to predict the shear capacity and the load-slip response of DENBCs in the PMR and NMR of steel-SFRC composite beams.
摘要：
This study investigates the coupled responses between the alongwind and acrosswind directions of a variable cross-section bridge tower model through wind tunnel experiments. Uniform and two turbulent flows with four different wind directions are designed to study their influences. The results show a significant coupling effect between the alongwind and acrosswind responses, influenced by incoming flow conditions and structure damping. In uniform flow, two distinct vortex-induced vibration (VIV) regions are observed when the structural damping is low, possibly due to the variable cross-section. When coupled VIV occurs, the responses of both alongwind and acrosswind directions show a hardening non-Gaussian distribution, and the kurtosis value is close to 1.5. The increase of structural damping will weaken the coupling effect, but slightly increase the dominant frequency of the coupling. Turbulence intensity reduces the VIV effect and coupling effect but does not eliminate the coupling in galloping. In particular, the critical wind speed of galloping will decrease with the increase of turbulence intensity. The coupling effect is prominent at 0° wind direction, mainly dominated by the acrosswind direction. However, the coupling effect is weak in other wind directions and is primarily dominated by the alongwind direction. The coupling effect makes the energy transfer between the alongwind and acrosswind directions, which is crucial for designing variable cross-section high-rise buildings and tower structures susceptible to wind-induced vibration.
This study investigates the coupled responses between the alongwind and acrosswind directions of a variable cross-section bridge tower model through wind tunnel experiments. Uniform and two turbulent flows with four different wind directions are designed to study their influences. The results show a significant coupling effect between the alongwind and acrosswind responses, influenced by incoming flow conditions and structure damping. In uniform flow, two distinct vortex-induced vibration (VIV) regions are observed when the structural damping is low, possibly due to the variable cross-section. When coupled VIV occurs, the responses of both alongwind and acrosswind directions show a hardening non-Gaussian distribution, and the kurtosis value is close to 1.5. The increase of structural damping will weaken the coupling effect, but slightly increase the dominant frequency of the coupling. Turbulence intensity reduces the VIV effect and coupling effect but does not eliminate the coupling in galloping. In particular, the critical wind speed of galloping will decrease with the increase of turbulence intensity. The coupling effect is prominent at 0° wind direction, mainly dominated by the acrosswind direction. However, the coupling effect is weak in other wind directions and is primarily dominated by the alongwind direction. The coupling effect makes the energy transfer between the alongwind and acrosswind directions, which is crucial for designing variable cross-section high-rise buildings and tower structures susceptible to wind-induced vibration.
摘要：
Internal damage imaging in concrete structures has consistently presented significant challenges as a complex multi-component material. To enhance the accuracy and efficiency of internal damage identification in concrete structures, an improved plane wave imaging technique based on the wavenumber algorithm is proposed in the paper. The introduction of the wavenumber algorithm provides a mathematical solution to the inverse problem for the assumed forward wave propagation model, which is more rigorous than the ray-based theory in mathematics. By comparing with the total focusing method and the conventional plane wave imaging technique, the proposed imaging technique exhibits significant advantages in imaging different types of damage in concrete structures. Subsequently, the 3D damage state of the simulated reinforcement steel debonding in concrete structures was reconstructed employing the proposed imaging technique. The enhanced imaging efficiency and optimized imaging quality settled the proposed imaging technique a promising candidate for future internal damage identification of concrete structures.
Internal damage imaging in concrete structures has consistently presented significant challenges as a complex multi-component material. To enhance the accuracy and efficiency of internal damage identification in concrete structures, an improved plane wave imaging technique based on the wavenumber algorithm is proposed in the paper. The introduction of the wavenumber algorithm provides a mathematical solution to the inverse problem for the assumed forward wave propagation model, which is more rigorous than the ray-based theory in mathematics. By comparing with the total focusing method and the conventional plane wave imaging technique, the proposed imaging technique exhibits significant advantages in imaging different types of damage in concrete structures. Subsequently, the 3D damage state of the simulated reinforcement steel debonding in concrete structures was reconstructed employing the proposed imaging technique. The enhanced imaging efficiency and optimized imaging quality settled the proposed imaging technique a promising candidate for future internal damage identification of concrete structures.
摘要：
Images captured under improper exposure conditions lose their brightness information and texture details. Therefore, the enhancement of low-light images has received widespread attention. In recent years, most methods are based on deep convolutional neural networks to enhance low-light images in the spatial domain, which tends to introduce a huge number of parameters, thus limiting their practical applicability. In this paper, we propose a Fourier-based two-stage low-light image enhancement method via mutual learning (FT-LLIE), which sequentially enhance the amplitude and phase components. Specifically, we design the amplitude enhancement module (AEM) and phase enhancement module (PEM). In these two enhancement stages, we design the amplitude enhancement block (AEB) and phase enhancement block (PEB) based on the Fast Fourier Transform (FFT) to deal with the amplitude component and the phase component, respectively. In AEB and PEB, we design spatial unit (SU) and frequency unit (FU) to process spatial and frequency domain information, and adopt a mutual learning strategy so that the local features extracted from the spatial domain and global features extracted from the frequency domain can learn from each other to obtain complementary information to enhance the image. Through extensive experiments, it has been shown that our network requires only a small number of parameters to effectively enhance image details, outperforming existing low-light image enhancement algorithms in both qualitative and quantitative results.
Images captured under improper exposure conditions lose their brightness information and texture details. Therefore, the enhancement of low-light images has received widespread attention. In recent years, most methods are based on deep convolutional neural networks to enhance low-light images in the spatial domain, which tends to introduce a huge number of parameters, thus limiting their practical applicability. In this paper, we propose a Fourier-based two-stage low-light image enhancement method via mutual learning (FT-LLIE), which sequentially enhance the amplitude and phase components. Specifically, we design the amplitude enhancement module (AEM) and phase enhancement module (PEM). In these two enhancement stages, we design the amplitude enhancement block (AEB) and phase enhancement block (PEB) based on the Fast Fourier Transform (FFT) to deal with the amplitude component and the phase component, respectively. In AEB and PEB, we design spatial unit (SU) and frequency unit (FU) to process spatial and frequency domain information, and adopt a mutual learning strategy so that the local features extracted from the spatial domain and global features extracted from the frequency domain can learn from each other to obtain complementary information to enhance the image. Through extensive experiments, it has been shown that our network requires only a small number of parameters to effectively enhance image details, outperforming existing low-light image enhancement algorithms in both qualitative and quantitative results.
作者机构：
[Li, Tao; Li, Jixiao] Key Laboratory of Safety Control of Bridge Engineering, Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China;[Li, Tao; Li, Jixiao] School of Civil and Environmental Engineering, Changsha University of Science & Technology, Changsha 410114, China;[Li, Tao; Li, Jixiao] National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment, Changsha 410114, China;[Li, Bingyang] Elite Engineering School, Changsha University of Science & Technology, Changsha 410114, China;[Yu, Guangtao] School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China
摘要：
In order to investigate the influence of the coexistence of clay and silt on the compression characteristics of sand, one-dimensional compression consolidation tests were carried out on reconstituted saturated sand-silt-clay mixtures with a constant initial void ratio, and the effects of fines content (FC) and clay-silt ratio (CS) on the compression characteristics of mixed soils were studied. The mechanism of the experimental results was additionally explained from a microscopic perspective. The test results show that: the compressibility of mixed soil increased with the increase in FC; the compressibility change rule of mixed soils with different CS is consistent under the same FC; the influence of CS on the e-lgp (the void ratio (e) versus logarithm of the pressure (p)) curve of mixed soil is inconsistent when FC is different: when FC = 3%, the compressibility of mixed soil decreased with the increase in CS; when FC = 7% and 10%, the compressibility of mixed soil gradually increased with the increase in CS; when FC = 5%, the compressibility of mixed soil did not show an obvious changing law with the increase in CS, and the compressibility of the specimen with FC = 5%-CS = 1 (FC = 5%, CS = 1) was the largest; when CS was same, the difference between e-lgp curves of mixed soil with different FC increased with the increase in CS. The compression model of sand-silt-clay mixtures was established, which can consider the effects of FC and CS. The reliability and applicability of the proposed model were verified by combining the experimental results of this paper and the test data of sand-clay mixture and sand-silt mixture in other literature.
摘要：
The existence of multiple cracks accelerates chloride ion penetration within damaged concrete, substantially shortening the lifespan of the structure. Therefore, this paper conducts an in-depth analysis of chloride migration mechanisms in cracked concrete subjected to multiple cracks under drying-wetting cycles. Firstly, a series of accelerated chloride diffusion experiments were conducted on prestressed concrete beams subjected to multiple cracks. The analysis examines how crack width, depth, and density affect chloride concentration distribution. Then, a chloride diffusion coefficient prediction model incorporating the effects of multiple cracks was established using the crack interaction function and verified through experimental data. Finally, this paper explored the distribution patterns of chloride concentration and convection zones in concrete subjected to multiple cracks under various environmental conditions. The experimental results showed that crack width exerts the strongest effect on chloride diffusion, followed by crack depth, while crack density has the smallest impact. At the same depth of diffusion, the chloride concentration in concrete specimens with crack width of 0.3 mm increased by 45 % and 25 % on average compared with those with crack width of 0.1 mm and 0.2 mm, respectively. The dry-wet time ratio and initial moisture saturation significantly affect chloride concentration distribution, with the depth of the convection zone showing a negative correlation with initial moisture saturation.
The existence of multiple cracks accelerates chloride ion penetration within damaged concrete, substantially shortening the lifespan of the structure. Therefore, this paper conducts an in-depth analysis of chloride migration mechanisms in cracked concrete subjected to multiple cracks under drying-wetting cycles. Firstly, a series of accelerated chloride diffusion experiments were conducted on prestressed concrete beams subjected to multiple cracks. The analysis examines how crack width, depth, and density affect chloride concentration distribution. Then, a chloride diffusion coefficient prediction model incorporating the effects of multiple cracks was established using the crack interaction function and verified through experimental data. Finally, this paper explored the distribution patterns of chloride concentration and convection zones in concrete subjected to multiple cracks under various environmental conditions. The experimental results showed that crack width exerts the strongest effect on chloride diffusion, followed by crack depth, while crack density has the smallest impact. At the same depth of diffusion, the chloride concentration in concrete specimens with crack width of 0.3 mm increased by 45 % and 25 % on average compared with those with crack width of 0.1 mm and 0.2 mm, respectively. The dry-wet time ratio and initial moisture saturation significantly affect chloride concentration distribution, with the depth of the convection zone showing a negative correlation with initial moisture saturation.
摘要：
Stress-constrained topology optimization under geometrical nonlinear conditions is still an open topic as it often encounter difficulties such as mesh distortion, inaccurate stress evaluation and low computational efficiency. For this purpose, this paper develops a novel parallel-computing based topology optimization methodology for geometrically nonlinear continuum structures with stress constraints. To alleviate the mesh distortions in the low-density regions, a smooth material interpolation scheme from with different penalization for the elastic and nonlinear stiffness is proposed. Moreover, a new hybrid stress finite element formulation is included into the geometrically nonlinear topology optimization to capture a more accurate stress distribution that is less sensitive to mesh distortions. Then, to improve the computational efficiency of geometrically nonlinear and sensitivity analysis, a parallel computing framework based on the assembly free iterative solution is established. Meanwhile, an efficient sparse matrix-vector multiplication strategy, which is applicable to solve the geometrically nonlinear problems, is proposed to exploit the computing power of GPU effectively. Finally, several numerical examples are given to illustrate the efficiency and feasibility of the proposed method.
Stress-constrained topology optimization under geometrical nonlinear conditions is still an open topic as it often encounter difficulties such as mesh distortion, inaccurate stress evaluation and low computational efficiency. For this purpose, this paper develops a novel parallel-computing based topology optimization methodology for geometrically nonlinear continuum structures with stress constraints. To alleviate the mesh distortions in the low-density regions, a smooth material interpolation scheme from with different penalization for the elastic and nonlinear stiffness is proposed. Moreover, a new hybrid stress finite element formulation is included into the geometrically nonlinear topology optimization to capture a more accurate stress distribution that is less sensitive to mesh distortions. Then, to improve the computational efficiency of geometrically nonlinear and sensitivity analysis, a parallel computing framework based on the assembly free iterative solution is established. Meanwhile, an efficient sparse matrix-vector multiplication strategy, which is applicable to solve the geometrically nonlinear problems, is proposed to exploit the computing power of GPU effectively. Finally, several numerical examples are given to illustrate the efficiency and feasibility of the proposed method.
摘要：
Traditional physical-driven modal methods are inappropriate for damage diagnosis of long-span flexible structures with complex mechanical behaviour. This study develops a deep Convolutional Neural Network-based damage diagnosis method for in-service bridges by using dynamic responses under moving loads. The dynamic responses were collected from the critical points on the girders of a cable-stayed bridge specimen under vehicle loading. These collected data was transformed into images based on Gramian Angular Field and Markov Transition Field (MTF). A deep learning algorithm based on VGG-19 was used to extract the damage feature from the data images associated with the structural responses. Finally, the unlabelled vibration data were input into the VGG-19 model for structural damage diagnosis. An experimental study was conducted for the damage diagnosis of a scale specimen of a cable-stayed bridge under moving loads. The acceleration signals of the main girder of the cable-stayed bridge under several damage conditions were monitored. The numerical results show the training accuracy of the deep learning method based on VGG-19 with MTF is up to 88%, and the average accuracy of the test dataset is 86.46% for each classification label. The transfer learning method can increase the classification accuracy up to 97.89%, indicating the advantage of intergrating transfer learning and VGG-19 network for structural damage diagnosis. The combination of VGG-19 and MTF algorithm provides a better solution for structural damage diagnosis of in-service infrastructures with long-term monitoring data.
期刊：
Journal of Building Engineering,2025年:112287 ISSN：2352-7102
通讯作者：
Hao Zhou
作者机构：
[Yan Liu; Zupan Zhang; Pengxiang Gao; Hao Zhou] School of Civil Engineering, Changsha Univ. of Science and Technology, Changsha 410114, China;Hunan Provincial Key Laboratory of Green Construction and Maintenance of Bridges and Buildings, Changsha Univ. of Science and Technology, Changsha 410114, China;[Youbao Jiang] School of Civil Engineering, Changsha Univ. of Science and Technology, Changsha 410114, China<&wdkj&>Hunan Provincial Key Laboratory of Green Construction and Maintenance of Bridges and Buildings, Changsha Univ. of Science and Technology, Changsha 410114, China
通讯机构：
[Hao Zhou] S;School of Civil Engineering, Changsha Univ. of Science and Technology, Changsha 410114, China
摘要：
Interlocking 3D printed concrete printed by tooth-like nozzles exhibits superior interfacial tensile performance. However, the influences of geometric parameters on the interlayer tensile strength of interlocking specimens remains unclear, and there is an urgent need to establish formulas to quantify the influences. To address these issues, this study, based on a novel single-tooth nozzle designed to enhance interlayer performance, comprehensively considers macro-mechanical performance testing and micro-porosity analysis. It reveals the failure modes of interlayer interfacial tension in single-tooth interlocking 3D printed concrete and proposes the tensile strength calculation formulas. Firstly, the theoretical analysis of the interlayer interfacial tensile strength of 3D printed concrete was performed. Then, conducted uniaxial tensile tests and validation experiments, and confirmed the validity of the theoretical formulas. Finally, the stress-strain curves of interlayer interlocking specimens with different single-tooth angles were analyzed. The results indicate that: (1) The interlayer interfacial tensile strength of interlocking 3D printed concrete with single-tooth nozzle is higher than that with square nozzles. (2) The failure cracks of specimens with square nozzle propagated horizontally in a straight line, while those of single-tooth interlocking specimens exhibited a serrated pattern along the interlocking interface. (3) The interlayer interfacial tensile strength formulas can effectively estimate the interlayer interfacial tensile strength of single-tooth interlocking 3D printed concrete. These findings provide methods and empirical insights for subsequent theoretical analysis and the establishment of calculation formulas for the strength of interlocking 3D printed concrete.
Interlocking 3D printed concrete printed by tooth-like nozzles exhibits superior interfacial tensile performance. However, the influences of geometric parameters on the interlayer tensile strength of interlocking specimens remains unclear, and there is an urgent need to establish formulas to quantify the influences. To address these issues, this study, based on a novel single-tooth nozzle designed to enhance interlayer performance, comprehensively considers macro-mechanical performance testing and micro-porosity analysis. It reveals the failure modes of interlayer interfacial tension in single-tooth interlocking 3D printed concrete and proposes the tensile strength calculation formulas. Firstly, the theoretical analysis of the interlayer interfacial tensile strength of 3D printed concrete was performed. Then, conducted uniaxial tensile tests and validation experiments, and confirmed the validity of the theoretical formulas. Finally, the stress-strain curves of interlayer interlocking specimens with different single-tooth angles were analyzed. The results indicate that: (1) The interlayer interfacial tensile strength of interlocking 3D printed concrete with single-tooth nozzle is higher than that with square nozzles. (2) The failure cracks of specimens with square nozzle propagated horizontally in a straight line, while those of single-tooth interlocking specimens exhibited a serrated pattern along the interlocking interface. (3) The interlayer interfacial tensile strength formulas can effectively estimate the interlayer interfacial tensile strength of single-tooth interlocking 3D printed concrete. These findings provide methods and empirical insights for subsequent theoretical analysis and the establishment of calculation formulas for the strength of interlocking 3D printed concrete.
摘要：
This study presents a novel method for calculating the stress and bending moment in reinforced concrete (RC) beams strengthened with prestressed near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP), focusing specifically on separation failure at the end concrete cover. By characterizing the geometry of the failure body and integrating it with the concrete tooth model, a comprehensive theoretical framework has been developed. This framework utilizes sectional strain distribution characteristics to establish the bending moment-curvature relationship and the load-deflection curve during loading. Comparisons with experimental data confirm the accuracy and applicability of this analytical model. The results demonstrate that the model is capable of accurately predicting the load-deflection behavior of the strengthened beam. Additionally, this study underscores the substantial impact of the CFRP prestress level on the concrete cover separation failure, showing that optimizing prestress settings can effectively enhance the ductility and bearing capacity of the strengthened beam.
摘要：
In order to enhance the efficiency of stochastic vibration analysis for train-bridge coupling systems, this paper proposes a novel approach based on the parallel adaptive enhanced (PAE)-surrogate model. First, an initial surrogate model is established to predict the extreme values of dynamic responses in the train-bridge coupling system using a small number of training samples. Second, a multipoint adaptive sampling method is employed to determine a set of new samples that provide more information. The theoretical extreme values of the dynamic responses corresponding to the new samples are calculated using parallel computing technology. Third, the surrogate model is optimized by incorporating the set of new samples and their corresponding theoretical extreme values. Finally, new samples are continuously added, and the surrogate model is enhanced until the number of training samples reaches the preset requirement. To validate the effectiveness of the proposed method, two examples are examined, encompassing analytical functions and the analysis of the wheel load reduction rate (WLRR) for trains on the bridge. The results show that the proposed PAE-surrogate model can select samples containing valuable information, significantly improving the prediction accuracy of the surrogate model without increasing the number of training samples. Additionally, the proposed method can fully exploit computational resources, thereby decreasing the number of iterations needed and increasing training efficiency. By considering a four-car CHR2 train passing through a three-span simply supported girder bridge as an example, the proposed method achieves 2.62times higher training efficiency compared to the nonparallel method.
摘要：
Images captured in the wild often suffer from issues such as under-exposure, over-exposure, or sometimes a combination of both. These images tend to lose details and texture due to uneven exposure. The majority of image enhancement methods currently focus on correcting either under-exposure or over-exposure, but there are only a few methods available that can effectively handle these two problems simultaneously. In order to address these issues, a novel partition-based exposure correction method is proposed. Firstly, our method calculates the illumination map to generate a partition mask that divides the original image into under-exposed and over-exposed areas. Then, we propose a Transformer-based parameter estimation module to estimate the dual gamma values for partition-based exposure correction. Finally, we introduce a dual-branch fusion module to merge the original image with the exposure-corrected image to obtain the final result. It is worth noting that the illumination map plays a guiding role in both the dual gamma model parameters estimation and the dual-branch fusion. Extensive experiments demonstrate that the proposed method consistently achieves superior performance over state-of-the-art (SOTA) methods on 9 datasets with paired or unpaired samples. Our codes are available at https://github.com/csust7zhangjm/ExposureCorrectionWMS .
Images captured in the wild often suffer from issues such as under-exposure, over-exposure, or sometimes a combination of both. These images tend to lose details and texture due to uneven exposure. The majority of image enhancement methods currently focus on correcting either under-exposure or over-exposure, but there are only a few methods available that can effectively handle these two problems simultaneously. In order to address these issues, a novel partition-based exposure correction method is proposed. Firstly, our method calculates the illumination map to generate a partition mask that divides the original image into under-exposed and over-exposed areas. Then, we propose a Transformer-based parameter estimation module to estimate the dual gamma values for partition-based exposure correction. Finally, we introduce a dual-branch fusion module to merge the original image with the exposure-corrected image to obtain the final result. It is worth noting that the illumination map plays a guiding role in both the dual gamma model parameters estimation and the dual-branch fusion. Extensive experiments demonstrate that the proposed method consistently achieves superior performance over state-of-the-art (SOTA) methods on 9 datasets with paired or unpaired samples. Our codes are available at https://github.com/csust7zhangjm/ExposureCorrectionWMS .
