摘要：
Fatigue cracking in welded joints is a critical problem in bridge engineering, especially for aging long -span steel bridges. The crack size and density are increasing gradually with the bridge aging process, where the crack interaction will accelerate the crack propagation or even short cracks merging into a long crack. However, the mechanism underlying the coupled propagation behavior of multiple cracks remains unclear. In this study, the coupling effect of multiple cracks was investigated based on numerical simulations. Subsequently, the numerical result was verified by a full-scale segmental fatigue experiment. In order to overcome the time-consuming iterative computations, the back propagation (BP) neural network was utilized to predict the effective coupling spacing between multiple cracks. Finally, a new crack reconstruction method was proposed to simplify crack merging processes. Results indicate that the coupled propagation behavior is significantly impacted by the effective crack spacing. The coupling effect is more significant at the near -end point compared to other feature points. In addition, the cracks with similar sizes have greater coupled effect, which is the worst -case scenario for the multiple fatigue crack problem. The experimental study demonstrates that the growth rate of the near -end point is 1.53 times that of the far -end point and pre -made cracks merge together successfully. By utilizing the BP neural network, the relative error of predicted effective spacing of two cracks is 3.52%. Compared to existing design specifications, the new reconstruction method provides a more reliable result for the fatigue life prediction of the welding seam with multiple fatigue cracks.
通讯机构：
[Zhang, L ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan Univ Technol, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
关键词：
boulder and hard rock environment;GPR;wavelet scale energy spectrum;wavelet packet energy;time-frequency characteristics
摘要：
The hard rocks in the stratum can pose safety risks and hinder the progress of urban underground tunnel construction using shield and jacking methods, thereby reducing construction efficiency and increasing construction costs. This paper utilizes wavelet scale energy spectrum, wavelet packet theory and statistical methods to conduct research on the detection of special geological formations such as hard rocks and voids, as well as the analysis of their signal time-frequency characteristics based on the ground-penetrating radar (GPR) technique. On the basis of calibrating the permittivity of different types of rock blocks, we established a forward model for detecting hard rocks and voids, and the simulated signals were analyzed in the time and frequency domains. Subsequently, laboratory experiments were conducted to perform GPR tests on different types of hard rocks in natural and water-saturated states and voids, to explore the time-frequency characteristics, frequency band energy variations, and statistical patterns of typical single-trace signals. The results show that the granite detection signal contains more low-frequency components, the sandstone detection signal contains more medium-low frequency components, while the limestone detection signal contains more medium-high frequency components in their natural state; the signal from the karst cave has relatively more low-frequency components than the signal from the empty cavity. The geometric shape of the rock has no influence on the dominant frequency and time-frequency distribution of its reflection signal. Generally, rocks with higher rebound values (hardness) also exhibit larger variance and standard deviation in frequency band energy. The research has important theoretical significance and practical value for the measurement and assessment of special geological features such as hard rocks and voids in urban underground trenchless construction.
摘要：
Stiff discontinuities have a significant influence on deep hard rock engineering disasters. To study the influence of these discontinuities on the deformation and failure mechanisms of deep hard rock during excavation, true triaxial tests are carried out on marble samples with natural stiff discontinuities; samples with different discontinuity inclination angles and thicknesses are tested under different true triaxial stress conditions. The experimental results show that the post-peak deformation and failure characteristics of a sample are significantly influenced by the inclination angle, thickness, and stress state of the stiff discontinuity. Under the conditions of a relatively high minimum principal stress, small intermediate principal stress, thick stiff discontinuity, and inclination angle close to the failure angle of the intact sample at the same stress level, the propagation and penetration of microcracks inside the sample are mainly controlled by the stiff discontinuity, and the sample is more prone to sudden and violent tensile failure along the stiff discontinuity. Based on these experiments, a sudden and violent failure tendency index of deep hard rock with a stiff discontinuity (psi) is proposed to evaluate the impact of stiff discontinuities on surrounding rock failure in deep engineering, and the characteristics of psi under typical stress levels are summarized. This research can provide a reference for the prevention and control of sudden disasters caused by stiff discontinuities in deep engineering.
摘要：
In this study, metakaolin (MK)–ground granulated blast furnace slag (GGBFS) was used to prepare geopolymer mortar, and concrete was prepared using prismatic-shaped basalt or aged cement mortar block as coarse aggregate. The pore structure characterization of the mortar, chloride binding capacity of the corresponding paste and the micro dimension of the interfacial transition zone (ITZ) in concrete were analysed by using a mercury intrusion porosimeter, the chloride adsorption equilibrium method and scanning electron microscopy-energy dispersive spectroscopy, respectively. The medium transmission properties of the concrete and corresponding mortar were analysed through a moisture diffusion test, chloride migration test, and chloride natural diffusion test. On this basis, the permeability resistance of the ITZ in geopolymer concrete was studied by manipulating the parameters for the basalt aggregate. The result shows that the geopolymer mortar exhibits higher porosity compared to cement mortar with similar strength, while the most probable pore size is significantly smaller, with more than 80% of the pores showing a pore size of less than 50 nm. The chloride binding mechanism for geopolymer paste primarily involves physical adsorption, and shows a greater binding capacity than cement paste at a chloride ion concentration greater than 1 mol/L. The medium transmission coefficient for geopolymer concrete is found to be 55.1–79.0% of that of cement concrete for the same parameters of the coarse aggregate. The impermeability of geopolymer concrete and its ITZ is found to be always better than that of cement concrete for varying parameters of the coarse aggregate.
摘要：
In this study, the axial compressive behaviors of steel reinforced ternary composite geopolymer recycled fireclay brick aggregates concrete columns were investigated. The ternary binder material used in this study was produced by the combination of industrial by-products (i.e., granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA)) and alkali-activated solution. A total of 60 square steel reinforced composite columns (with a 200-mm side length and 600-mm height) were tested under axial compression. The tested variables included the mix proportion of ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates (GRA-RFBAC), the recycled coarse aggregate replacement ratios (0%, 30%, 50%, 70%, 100%), the longitudinal reinforcement ratios (1.13%, 2.01%), and the hoop stirrup reinforcement ratios (0.81%, 1.62%). Each group contained three identical samples. The ductility, failure mode, and axial load-bearing capacity of the columns were recorded and analyzed. The experimental results revealed that the damage progression and patterns of steel reinforced GRA-RFBAC columns were similar to those of ordinary Portland cement based recycled concrete columns. The ultimate bearing capacity of steel reinforced GRARFBAC columns decreased with an increasing replacement ratio of recycled coarse aggregate and increased with an increasing reinforcement ratio of longitudinal and hoop stirrups. Meanwhile, the stress-strain model of steel reinforced GRA-RFBAC columns under axial compression was proposed based on the experimental results. The present study suggests an efficient and environmental-friendly compression member.
关键词：
Reinforced concrete ribbed arch bridge;temperature field;solar radiation;temperature gradient;three-dimensional temperature field
摘要：
Advances in Structural Engineering, Volume 27, Issue 6, Page 995-1015, April 2024. <br/>The unique structural design of an arch ring featuring varying inclination angles for individual segments causes variations in the longitudinal distribution of the temperature field d along the arch axis. This study aims to enhance the understanding of temperature fields in reinforced concrete (RC) arch bridges with diverse arch ring structural configurations during their construction phases. A comprehensive investigation into the three-dimensional distribution pattern of solar-induced temperature fields within arch ribs during the construction of RC ribbed arch bridges was conducted. A field test specifically measuring the temperature distribution across arch rib cross-sections was conducted on-site, involving an RC arch bridge constructed using the cable-stayed cantilever cast in situ method. Analyzing the monitored on-site temperature data revealed the distribution characteristics of temperature fields at the arch foot cross-section under solar radiation. By comparing these findings with international standards, a vertical temperature gradient fitting model for arch rib cross-sections under solar radiation was formulated. Drawing upon meteorological records and solar radiation principles, an adaptive numerical simulation finite element model was developed to depict the temperature field within an arch rib section. This model was rigorously verified. Subsequently, a comprehensive analysis of the three-dimensional temperature field of the arch rib under solar radiation was performed. Additionally, a three-dimensional temperature gradient fitting model was proposed, accounting for the longitudinal inclination of the bridge.
摘要：
The welding of steel generates substantial welding residual stress (WRS), which exerts a significant impact on the fatigue life of steel bridges. In this study, a physical model for calculating the fatigue crack growth (FCG) life of welded specimens in the WRS field is established based on the weight function method. Experimental data validates the reliability and precision of the proposed physical model. The impact of WRS on the fatigue life of structural components is scrutinized and analyzed. On this basis, a digital twin (DT) framework driven by a physical-data model is proposed to consider the inherent parameter uncertainty in FCG behavior within the WRS domain. A dynamic Bayesian network (DBN) is used to characterize the evolution characteristics of fatigue crack states over time in the digital space. Particle filter algorithm is used as DBN inference method. The results show that the calculation of the physical model is in good agreement with the experimental values. Neglecting the influence of WRS distribution may lead to an overestimation of fatigue life in welded structures. The DT framework can update uncertain parameters online and realize the accurate prediction of the FCG life in the WRS field.
作者机构：
[Zhenzhou Jin; Xin Ye] School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China;[Jiangang He] Hunan Renjian Baogu High-Tech Development Co., Changsha 410114, China;Author to whom correspondence should be addressed.;[Guangyao Li; Chao Wang; Xuemei Huang] School of Transportation Engineering, Changsha University of Science and Technology, Changsha 410114, China;[Weijun Yang] School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Hunan Renjian Baogu High-Tech Development Co., Changsha 410114, China
通讯机构：
[Jianyu Yang] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
摘要：
The huge demand for sand and gravel resources in road engineering construction leads to excessive consumption of resources and environmental damage. Recycling waste concrete and industrial solid waste as a road material is a promising alternative. In order to explore the application of these solid wastes in the road base, this paper studies the effect of adding lithium slag activated by an alkaline activator, fly ash (FA) and a combination of the two on the compressive strength, splitting strength and shrinkage performance of recycled cement-stabilized macadam mixture (RCSM). The optimum content of recycled aggregate (RA), alkali-activated lithium slag (AALS) and FA in composite-improved RCSM was optimized using a response surface method (Box–Behnken), and the microscopic characteristics of the mixture were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the optimum dosage of AALS, FA and RA determined by the response surface method is 15%, 10% and 40%, respectively. Compared with the cement-stabilized macadam mixture (CSM) with 40% RA, the 28 d compressive strength and 28 d splitting strength of the composite-improved RCSM are increased by 26.8% and 22.9%, respectively, and the dry shrinkage coefficient and average temperature shrinkage coefficient are decreased by 25.8% and 14.8%, respectively. Microscopic tests show that AALS and FA participate in the hydration reaction, generate more hydrated silicate (C-S-H) and ettringite (AFt), refine pores, effectively improve the performance of the internal interface transition zone of the mixture, make the microstructure of the mixture denser, and improve the strength and shrinkage performance of RCSM. This study provides technical support for the reuse of resources and the sustainable development of road construction.
摘要：
To investigate the vortex-induced vibration (VIV) of a flexible cable in the uniform flow, experiments were conducted using a flexible cable with an external diameter of 80mm and a length of 10.48m in the wind tunnel. The characteristics of multi-modal VIV, time-frequency and traveling wave behavior of the flexible cable were analyzed. Moreover, the effects of twist direction, diameter and the single/double helical wire on the VIV characteristics of the flexible cable were investigated. It is found that the flexible cable experiences single and multi-modal VIVs in uniform flow at different incoming wind speeds, respectively. For the multi-modal VIV of the flexible cable, the vibration over the time history is dominated by two adjacent modal frequencies and shows a phenomenon of beat vibration. The multi-modal VIV responses of the flexible cable show a mix of standing and traveling wave behaviors, in which the effects of standing wave are more pronounced near both ends and the effects of traveling wave are more dominant in the middle region of the flexible cable. The twist direction of the helical wire has little effect on the VIV responses of the flexible cable. The VIV amplitudes of the flexible cable can be reduced by a single helical wire. With the diameter of the helical wire increases, the suppression effects of the single or double helical wire on the VIV of the flexible cable can be improved. Particularly, the double helical wire with diameter 0.10D can effectively suppress the VIV of the flexible cable.
作者机构：
[Yonggang Huang] College of Civil Engineering, Hunan City University, Yiyang, China;China Light Industry Changsha Engineering Co., Ltd., Changsha, China;[Guiyao Wang] College of Civil Engineering, Changsha University of Science and Technology, Changsha, China;[Jingliang Fu] China Light Industry Changsha Engineering Co., Ltd., Changsha, China<&wdkj&>College of Civil Engineering, Changsha University of Science and Technology, Changsha, China
通讯机构：
[Yonggang Huang] C;College of Civil Engineering, Hunan City University, Yiyang, China
关键词：
Vetiver root;Root–soil interface;Expansive soil;Pullout test
摘要：
Studying the pullout characteristics of roots can help to gain a deeper understanding of the interaction mechanism between plants and soil, and provide theoretical support and practical guidance for engineering applications. This paper aims to investigate the pulling characteristics of the root–soil interface in expansive soil reinforced by vetiver roots. For this purpose, the study focuses on exploring the correlation between the pullout force (PF) required to extract the roots and the pullout displacement caused by the extraction. The research also examines how the geometry of the roots affects the pulling characteristics of the root–soil using a pullout test. It is found that with increasing root diameter, root length segment (RLS), root volume, and root surface area (RSA), the maximum PF increases. The highest correlation coefficient was found between RSA and maximum PF, which explained 81.4% of the variation in maximum PF. Then, the functional relationship between RLS and PF is established. Using RSA to predict the maximum PF of vetiver root is relatively reasonable. The assessment of PF must consider RSA indicators. The increase in RSA due to a high number of roots results in the improvement of the PF of vetiver root. These findings could assist in enhancing the strength of expansive soils.
摘要：
The low carbon footprint and superior properties of geopolymer make it a potentially suitable alternative to ordinary Portland cement, which has been one of the dominating research focuses in the last decades. However, the mechanisms of geopolymeric reactions and the nanostructure of geopolymer are still questionable. Besides, some undesired properties in geopolymer synthesis limit the field application of geopolymers. This paper focused on the current knowledge of the reaction chemistry and nanostructure of geopolymer and factors affecting metakaolin-based geopolymer synthesis. A systematic summary of the reaction process, chemical bonds in geopolymer, and models of geopolymer were provided to better understand the reaction mechanisms of geopolymerization. Various factors important to geopolymer's properties, including Si/Al ratio, Na/Al ratio, type of alkaline activator and alkali cation, water/solid ratio, and curing condition, were comprehensively reviewed to guide the geopolymer synthesis. Through this review, we hope to promote this field's continued growth and development and encourage the wider adoption of geopolymers as a sustainable alternative to traditional construction materials.
摘要：
The challenge for practical application of frame structural optimization had previously been investigated by many works, while the mechanical performance requirements such as the displacement, stress, and stability requirements, were often considered separately within optimization, hindering their practical applications. For this purpose, an integrated topology and size optimization strategy of frame structures, in which the structural weight is taken as the objective with the constraints regarding the displacement, stress, as well as stability, is presented in this paper. Different from former researches, each beam is assigned with a topology variable representing the presence of the beam and a size variable correspond to the cross-sectional geometric properties. To achieve an optimized design with standard members, by cooperating the ordered multi-material SIMP (solid isotropic material with penalization) interpolation with the normalized Heaviside functions, the continuous size design variables are projected onto the discrete standard sizes conformed to standard library. Moreover, the comprehensive measure, including the stress relaxation, the pseudobuckling mode treatment scheme, the aggregation constraint, and varying constraint limit schemes, is employed to deal with the multiple constraints in the optimization model. Then, the sensitivities of the objective and constraint functions with respect to topology and size design variables are derived, respectively, and the proposed integrated optimization problem is solved by a nested optimization algorithm. Finally, several numerical examples are presented to demonstrate the feasibility of the proposed approach.
通讯机构：
[Han, Y ] C;Changsha Univ Sci & Technol, Sch Civil Engn, 960 2nd Sect Wanjiali South Rd, Changsha 410114, Hunan, Peoples R China.
关键词：
3D nonlinear flutter analysis;Time-dependent nonlinear self-excited force model;Geometric nonlinearity;Long-span bridge;Full-mode nonlinear flutter analysis
摘要：
The present study aims to investigate the influence of geometric nonlinearity on post-flutter responses by developing a full-mode coupled nonlinear flutter analysis method (frequency-domain method) and a time-dependent nonlinear analysis scheme (time-domain method). This approach integrates the three-dimensional (3D) nonlinear finite element model and nonlinear self-excited force described by amplitude-dependent rational functions (RFs). By comparing post-flutter responses obtained from frequency-domain and time-domain methods, not only the influence of geometric nonlinearity on post-flutter responses is quantified, but also the underlying physical mechanism is revealed. The results show that the geometric nonlinear effect will become more significant with the increase of the amplitude and thus will induce a super-harmonic resonance behavior. The behavior is mainly characterized by the higher harmonic frequencies vibrations with higher-order mode shapes involved in the vertical and torsional displacement responses. Meanwhile, the larger the vibration amplitude, the more significant the super-harmonic resonance behavior. Besides, the geometric nonlinear effect will also cause a significant uplifting of the bridge deck in the vertical direction during 3D nonlinear flutter process. The main physical mechanism for the reduction in the amplitude of post-flutter response (dominated by the vibration with fundamental harmonic frequency) after considering the geometric nonlinear behavior is that the vibrations with higher harmonic frequencies play a role of absorbing energy and reducing vibration (similar to tuned mass damper effect) for the vibration with fundamental harmonic frequency. For the long-span suspension bridge with a main span of 1650 m studied in this study, the geometric nonlinear effect may need to be considered when the torsional amplitude at mid-span is only greater than 1.5 degrees.
期刊：
Journal of Civil Structural Health Monitoring,2024年:1-22 ISSN：2190-5452
通讯作者：
Tianyong Jiang
作者机构：
[Chunjun Hu; Lingyun Li] School of Civil Engineering, Changsha University of Science and Technology, Changsha, People’s Republic of China;Key Laboratory of Bridge Engineering Safety Control by Department of Education, Changsha University of Science and Technology, Changsha, People’s Republic of China;[Tianyong Jiang] School of Civil Engineering, Changsha University of Science and Technology, Changsha, People’s Republic of China<&wdkj&>Key Laboratory of Bridge Engineering Safety Control by Department of Education, Changsha University of Science and Technology, Changsha, People’s Republic of China
通讯机构：
[Tianyong Jiang] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha, People’s Republic of China<&wdkj&>Key Laboratory of Bridge Engineering Safety Control by Department of Education, Changsha University of Science and Technology, Changsha, People’s Republic of China
关键词：
Complex background;Semantic segmentation;Phase;Complexity pursuit;Cable frequency estimation
摘要：
This paper proposes a new complex background segmentation method based on the modified fully convolutional network semantic segmentation for noncontact cable vibration frequency estimation. The estimation of frequency from video data is challenged by the presence of background object motion, which directly impacts the accuracy of the video-based method. To address this issue, image tests were carried out among the existing model (U2-Net) to explore the effect of the efficient channel attention (ECA) and convolutional block attention module (CBAM) on cable segmentation performance. As a result, a relative optimal model was identified. This modified model was then used to remove the complex background, while retaining the vibration signals specific to the cable. Subsequently, phase matrices encoding cable vibration were calculated using a phase-based motion estimation algorithm at various cable locations. The modal response of the cable vibration was estimated using the complexity pursuit (CP) algorithm from the segmented video. Finally, the vibration frequency of the cable was estimated. The proposed method was validated on a small-scale cable model. The results are in good agreement with the values sampled by the accelerometer, with an average relative error of 4.50%. This estimation shows the significant potential of the proposed method in structural health monitoring.
期刊：
Journal of Building Engineering,2024年86:108799 ISSN：2352-7102
通讯作者：
Zhou-ping Yu
作者机构：
Yuanpei College, Shaoxing University, Shaoxing, 312000, China;[Wei-jun Yang] College of Civil Engineering, Changsha University of Science and Technology, Changsha, 410076, China;[Zhou-ping Yu] Yuanpei College, Shaoxing University, Shaoxing, 312000, China<&wdkj&>College of Civil Engineering, Changsha University of Science and Technology, Changsha, 410076, China
通讯机构：
[Zhou-ping Yu] Y;Yuanpei College, Shaoxing University, Shaoxing, 312000, China<&wdkj&>College of Civil Engineering, Changsha University of Science and Technology, Changsha, 410076, China
摘要：
This paper has investigated the effects of the six factors of concrete volume density, polystyrene particles, water-cement ratio, sand rate, glass powder, and silicon ash on the thermal properties of polystyrene granular concrete, analyzed the degree of influence of various factors through the principal component method, established a comprehensive index where the thermal conductivity of polystyrene granular concrete, is affected by multiple factors and determined a model equation for the standard value of the thermal conductivity. On this basis, the conclusion has been reached. Specifically, the polystyrene particle content has the most significant effect on the thermal conductivity of the polystyrene particles, followed by the bulk density of concrete, with glass powder having the most negligible impact. When the replacement rate of silicon ash is greater than 10%, the thermal conductivity of polystyrene granular concrete could be reduced to improve its thermal performance. When polystyrene granular concrete is prepared using silicon ash, its thermal conductivity is reduced by 22%. When the replacement rate of glass powder does not exceed 20%, it exerts a positive effect on reducing the thermal conductivity of polystyrene granular concrete. Among them, when the glass powder replacement rate is 10%, the thermal conductivity reaches a minimum value, which is 16.1% lower than that of the control group. With the increase of the sand rate, the thermal conductivity of polystyrene granular concrete increases, and the higher the bulk weight of the concrete, the smaller the increase in thermal conductivity.
摘要：
In recent advancements, a novel strengthening approach employing engineered cementitious composites (ECC) and fibrereinforced polymer (FRP) materials has emerged. This method integrates ECC as the matrix, carbon fibre-reinforced polymer (CFRP) grid as the internal strengthening component, and epoxy resin for bonding the overlay to the concrete substrate. This study conducted tests on four reinforced concrete (RC) beams under a four-point load configuration. One beam served as an un-strengthened control specimen, while three were subjected to different shear strengthening methods: polymer-modified mortar (PMM), ECC, and CFRP grid-reinforced ECC matrix composites layer (FGREM). The investigation covered failure modes, load-deformation relationships, and load-strain relationships. Finite element (FE) analysis was employed to reproduce the test results. Key findings include the ability of ECC as a matrix to substantially reduce concentrated interfacial bond stresses, preventing debonding failure. The FGREM-strengthened specimen exhibited a failure mode characterized by side concrete cover separation, resulting in a notable 124% enhancement in shear resistance. The proposed FE model, incorporating interfacial behaviour, accurately simulated the performance of all specimens.
作者机构：
[Huiping Zhang; Zhefeng Liu] School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China;Author to whom correspondence should be addressed.;[Qi Han; Shougang Fan; Chenxin Qin; Zhijie Xu] Huadian New Energy Group Corporation Limited Hunan Branch, Changsha 410014, China;[Pengfei Li] School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
通讯机构：
[Pengfei Li] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
wind turbine;foundation with embedded steel ring;aerodynamic imbalance;error in pitch angle;fatigue damage;finite element simulation
摘要：
Wind turbine (WT) foundations with an embedded steel ring (ESR) are widely used in onshore WTs due to construction convenience. The research group found that WT foundations with damage were often accompanied by blade issues. To investigate the potential correlation between aerodynamic imbalance and fatigue damage of the WT foundation with an ESR, this study focuses on a 2 MW WT with an ESR. It investigates the influence of an error in pitch angle (PAE) on the WT’s foundation load and stress, utilizing one year of SCADA data to analyze the fatigue damage caused by PAE. The main conclusions are as follows: Firstly, the effect of PAE on the amplitude value of load and stress is significantly greater than on the average value of load and stress. Secondly, when the PAE is within the range of −3° to 3°, the foundation fatigue damage incurred over one year is minimal, but once this limit is exceeded, the foundation fatigue damage increases dramatically. Thirdly, the peak value of fatigue damage to the foundation caused by PAE does not necessarily occur in the main wind direction, but in the direction with the highest probability of the occurrence of high wind speeds, and the larger the PAE, the more significant the trend.
摘要：
In this study, a fast hybrid algorithm based on surrogate and theoretical models is proposed. It solves surrogate model failure with too many inputs to the system and improves the computational efficiency in random vibration analysis of train-bridge systems under crosswinds. First, the surrogate model to rapidly predict the wheel-rail force time history and the theoretical model (finite element model) of the bridge are established. Then, a large number of samples of fluctuating wind speeds and track irregularities are generated based on the Monte Carlo method. Next, the wheel-rail force and the dynamic response of the bridge are calculated using the surrogate and theoretical models, respectively, and the coupling of the train and bridge subsystems is realized through iteration. Finally, the random vibrations of the train-bridge system under crosswinds are analyzed based on the calculation results of all samples. The results of the hybrid algorithm agree well with those of the traditional calculation method. The maximum normalized mean square error (NMSE) is only 0.0105, and the computational efficiency of the hybrid algorithm is nearly 4 times higher than that of traditional calculation methods. When the train is in the midspan of the bridge, the bridge dynamic response has a large mean and standard deviation. Under crosswinds, wheels on the windward side determine the safe running of the entire train. Under the wind speed of 15 m/s and Chinese high-speed railway track irregularities, the train operation reliability on the bridge is 98 %.
