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SSRN 2024年

作者： Tian, Run-Ze Li, Xiao-Kang Zhang, Yu Zhang, Lu-Xin Yue, Zu-Run Li, Xu Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong University Beijing China School of Traffic and Transportation Lanzhou Jiaotong University Lanzhou730070 China China Railway Northwest Science Research Institute Co. Ltd China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China

The temperature disparity between shady and sunny slopes leads to uneven subgrade deformation in permafrost regions. In response, this paper introduces a novel photovoltaic sheltered boards (PSB) subgrade and conducts a numerical investigation into its mitigation of shady-sunny slopes effect. The study commences with developing a two-dimensional heat transfer model, accounting for the coupled boundary of solar radiation and air convection. The numerical model was validated through monitored temperature data from the Beiluhe observation station. Subsequently, the study calculates the temperature distribution of the exposed subgrade to illustrate the effect of shady-sunny slopes and identify influencing ***, this study explores the feasibility of equalizing differential temperatures through insulated boards (IB), which refers to the traditional subgrade with laid IB and the novel PSB subgrade with suspended IB. Finally, the mitigation effects of temperature difference of two modes are compared, considering key parameters including solar radiation, subgrade alignment, wind speeds, and reflection rate. The study concludes that solar radiation significantly influences the shady-sunny slope effect, followed by subgrade direction, wind speed, and reflection rate. Both IB and PSB modes can reduce thaw depths and mitigate the shady-sunny slope effect by blocking solar radiation, with PSB demonstrating superior effects due to heat convection among an adjustable suspension height. Additionally, PSB results in a reduction of over 3 ℃ in the average annual temperature of the sunny slope and is recommended to be suspended at a height exceeding 5.3 cm in the research area. In summary, the PSB subgrade effectively mitigates shady-sunny slopes and is recommended with comprehensive consideration of mitigation performance and carbon emissions. © 2024, The Authors. All rights reserved.

关键词： Heat convection

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The Dynamic mechanical behavior of Sap Based Porous Cement-Based Materials Suitable for Emas

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SSRN 2023年

作者： Yang, Haitao Bian, Hongjian Jing, Qingshuo Tan, Hongbo Sun, Guowen Wu, Lipeng Wang, Yichao Zhang, Zejun Wang, Wei School of Civil Engineering Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China State Key Laboratory of Mechanics Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China Key Laboratory of Roads and Railway Engineering Safety Control Ministry of Education Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China State Key Laboratory of Silicate Materials for Architecture Wuhan University of Technology Hubei Wuhan430070 China

Superabsorbent polymers (SAP) voids have the potential to prepare cement-based materials (CBMs) that meet the engineered materials arresting system (EMAS) requirements due to their similarity to entrained air voids. This idea was validated using a crushing test and an immersion softening test in this paper. The pore structure and micromechanical properties of CBMs incorporating SAP were analyzed using an image analysis, a boiling method, a microhardness test, and a nanoindentation test. Moreover, the influence of SAP on the quasi-static and dynamic mechanical properties of CBMs was studied using a rigid press machine and an SHPB system. The results show that the crushing and immersion softening properties of CBMs can meet the EMAS requirements when SAP dosages are 10% and 12%. The optimal dosage of SAP is 10%. Under quasi-static and dynamic compression, the compressive strength and elastic modulus decrease with increasing SAP dosage, due to the growth of the total porosity of samples and the decline in the micromechanical properties of the matrix. Increasing the SAP dosage can raise the total porosity, thereby enlarging the DIF-fc value and decreasing the DIF-E value. Raising the strain rate results will enlarge the DIF-fc and DIF-E values. This is due to the growth in the damage degree of the specimen and the change in the cracking behavior under dynamic compression. © 2023, The Authors. All rights reserved.

关键词： Pore structure

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Study on mechanical properties and failure characteristics of rock mass with weak interlayer subjected to freezing–thawing treatment

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Arabian Journal of Geosciences 2022年第10期15卷 1-9页

作者： Fang, Zhichun Zhu, Zhengguo Zhang, Shuai Wu, Siqi Ma, Chaoyi Wang, Renyuan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuag Tiedao University Shijiazhuang People’s Republic of China State Key Laboratory for Track Technology of High-Speed Railway China Academy of Railway Sciences Beijing People’s Republic of China Hebei Province Technical Innovation Center of Safe and Effective Mining of Metal Mines Shijiazhuang People’s Republic of China School of Traffic and Transportation Shijiazhuag Tiedao University Shijiazhuang People’s Republic of China

Influenced by the geological activity, there are a lot of weak interlayers in the surrounding rock of tunnels along railway in China, and the severe cold climate has a great influence on the engineering properties of rock in cold region. To better understand the influence of interlayer dip and freezing–thawing (F-T) cycles on the mechanical properties and failure characteristics of tunnel surrounding rock and therefore providing a theoretical basis for the tunnel support design, rock samples with different dips of weak interlayer and different F-T cycles were prepared in laboratory, and the triaxial compression test was carried out. The results show that (1) the deformation of hard rock part with weak interlayer is small, while the failure of soft rock interlayer is more severe. When the dip angle of the interlayer is small (β = 0° and 30°), the fracture crack is nearly parallel to the dip angle of the interlayer after rock failure. When the dip angle of the interlayer is large, the fracture surface of the rock mass and the interlayer present an X-shaped intersection. The more F-T cycles, the stronger the damage degree of rock mass. (2) Triaxial compression strength (TCS) and elastic modulus of rock mass decrease first and then increase with the increase of dip angle of interlayer, and the compressive strength and elastic modulus are the minimum when the dip angle of interlayer β = 45°. Compared with the rock mass with horizontal weak interlayer, the compressive strength decreases by 35.27%, and the elastic modulus decreases by 34.84%. (3) F-T cycles have a significant deterioration effect on the mechanical properties of rock mass. The bearing capacity of rock mass decreases with the increase of F-T cycles, but the plastic deformation capacity increases. There is a negative exponential correlation between TCS, elastic modulus, and F-T cycles and a positive linear correlation between peak strain and F-T cycles.

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Load Distribution Uniformity of Assembled Emergency Steel Bridge Pier Columns

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SSRN 2024年

作者： Liu, Zi-Yu Chen, Shi-Tong Zhi, Mo-Mo Cheng, Shuai-Qi Fan, Xin Collaborative Innovation Center for Performance and Security of Large-scale Infrastructure Shijiazhuang Tiedao University Shijiazhuang China Hebei Eng. Innovation Center for Traffic Emergency and Guarantee Shijiazhuang Tiedao University Shijiazhuang China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China

Throughout the utilization of assembled emergency steel bridge piers, there is a significant discrepancy in the load carried between different columns, which can lead to premature failure of individual columns and potentially trigger the collapse of the entire structure. Currently, there is no mature method for calculating and implementing load distribution. Based on an improved Fourier series and energy principle, this paper proposes a universal calculation method for the load distribution of columns in assembled emergency steel piers. A specific assembled emergency steel pier is selected as the research subject to conduct model tests and simulation experiments. Through mutual verification of theory, experiments, and simulations, this study analyzes the key factors affecting the load distribution of columns, examines the mechanisms and patterns of their impacts, and explores general principles for the even distribution of loads. The research shows: As the column height or diameter-to-thickness ratio increases, the proportion of load borne by the corner columns and transverse edge columns increases, while the central and longitudinal edge columns see a reduction in their load proportions. A pier-beam linear stiffness ratio based on an overall consideration is proposed. As the height of the columns or the diameter-to-thickness ratio increases, the pier-beam linear stiffness ratio tends to decrease. Using the coefficient of variation of column loads as the standard for evaluating the pier-beam linear stiffness ratio, the recommended threshold for the application of the pier-beam linear stiffness ratio in engineering should be between 3 and 3.86. © 2024, The Authors. All rights reserved.

关键词： Steel bridges

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Research on Multi-Scale High-Fidelity Digital Model and Reduced-Order Model for Digital Twin Modeling of Composite structures

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Forest Chemicals Review 2021年第JULY-AUGUST期2021卷 1469-1482页

作者： Zuo, Jiale Li, Dong Zhou, Ling Zhang, Cun Wang, Huicong Nanchang Hangkong University School of Aircraft Engineering Jiangxi Nanchang330063 China Hebei Jiaotong Vocational and Technical College Center for Quality Management Hebei Shijiazhuang050035 China Shijiazhuang Tiedao University State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Hebei Shijiazhuang050043 China Hebei Jiaotong Vocational and Technical College Department of Road and Bridge Engineering Hebei Shijiazhuang050091 China

The research purpose of this paper is to establish a multi-scale high-fidelity digital model and a reduced-order model for digital twin of composite structures. Firstly, a high-fidelity digital model is established for the composite structure using micro-meso-macro multi-scale method to accurately describe the composite structure. Then, in order to meet the real-time needs of digital twin, the reduced-order model is studied by using three training algorithms for comparative study: Bayesian Regularization (B-R), Levenberg-Marquardt (L-M), and Scaled Conjugate Gradient (SCG). B-R training algorithm with smaller error is chosen to establish a neural network reduced-order model. Finally, with the multi-scale high-fidelity digital model as a reference, the maximum error of the established reduced-order model is 5.64%, which can meet the needs for multi-scale digital twin modeling of composite structures. © 2021 Kriedt Enterprises Ltd. All right reserved.

关键词： Structure (composition)

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Study on the Band Gap and Directional Wave Propagation Mechanism of Novel Single-Phase Metamaterials

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SSRN 2022年

作者： Cheng, Shu-Liang Yang, Hong-Yun Yan, Qun Wang, Bin Sun, Yong-Tao Xin, Ya-Jun Ding, Qian Yan, Hao Wang, Liang Key Laboratory of Mechanical Reliability for Heavy Equipment and Large Structure of Hebei Province Yanshan University Qinhuangdao China Tianjin Key Laboratory of Soft Soils and Engineering Environment Tianjin Chengjian University Tianjin China Department of Mechanics Tianjin Key Laboratory of Nonlinear Dynamics and Control Tianjin University Tianjin China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China Key Laboratory of Aeroacoustics and Dynamics Aircraft Strength Research Institute Xi’an China Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province Yanshan University Qinhuangdao China

In this paper, a new type of single-phase metamaterial is proposed. Based on the finite element method, the band gap characteristics of the structures with different branches are comprehensively analyzed, and the existence of the band gap is further verified by the frequency response transmission spectrum. Then, the propagation characteristics of elastic waves of different frequencies in different combinations of structures are investigated respectively. The results show that the proposed single-phase metamaterial structure has an excellent band gap range, and under the action of relatively low-frequency elastic waves, the wave propagation in the structure has a certain direction and regionality, while the elastic waves at higher frequencies are applied, the propagation direction of the wave tends to propagate in all directions. This paper provides a new idea for studying the structural design of metamaterials with specific wave propagation directions. © 2022, The Authors. All rights reserved.

关键词： Energy gap

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Analyzing Convective Heat Transfer in Combined Solar Chimneys: A Theoretical and Numerical Study of key Influencing Parameters

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SSRN 2024年

作者： Cui, Huimin Han, Mengjiao Zhang, Jitao Han, Zhiming Liu, Qingkuan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Shijiazhuang050043 China Department of Mathematics and Physics Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China

Combined solar chimneys represent a potent mechanism for harnessing solar energy to bolster natural ventilation in green building designs. This study focuses on the impact of structural parameters and external conditions on the ventilation and heat transfer performance of such systems. Through scaling analysis and numerical simulations, we investigate the flow dynamics and heat transfer mechanisms. We examine the mechanism and the influence of three critical control parameters: inlet size ratio (h/H), ratio of inclined to vertical section lengths (L/H), and Rayleigh number (Ra). Our findings indicate that ventilation and heat exchange performance exhibit an initial increase followed by a decline as the inlet size ratio expands from 0.10 to 0.40. Optimal ventilation efficiency is observed at a Rayleigh number of 1.98×1014 with an inlet size ratio of 0.15. Conversely, a low ratio of inclined to vertical section lengths (L/H=0.20) correlates with suboptimal ventilation performance. Both ventilation intensity and efficiency are positively correlated with increases in Ra. This research quantitatively delineates these relationships, providing a theoretical foundation for the design of natural ventilation systems in sustainable buildings using combined solar chimneys. © 2024, The Authors. All rights reserved.

关键词： Computational fluid dynamics

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Analyzing Convective Heat Transfer in Combined Solar Chimneys: A Theoretical and Numerical Study of key Influencing Parameters

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SSRN 2024年

Combined solar chimneys represent a potent mechanism for harnessing solar energy to bolster natural ventilation in green building designs. This study focuses on the impact of structural parameters and external conditions on the ventilation and heat transfer performance of such systems. Through scaling analysis and numerical simulations, we investigate the flow dynamics and heat transfer mechanisms. We examine the influence of five critical control parameters: inclination angle (α), inlet size ratio (h/H), ratio of inclined to vertical section lengths (L/H), Rayleigh number (Ra), and the temperature difference between indoor and outdoor environments (Δθ). Our findings indicate that ventilation intensity escalates with increasing inclination angle, particularly within the range of 15°to 75°, achieving standard requirements at angles of 30° or greater. Ventilation and heat exchange performance exhibit an initial increase followed by a decline as the inlet size ratio expands from 0.10 to 0.40. Optimal ventilation efficiency is observed at a Rayleigh number of 1.98×1014 with an inlet size ratio of 0.15. Conversely, a low ratio of inclined to vertical section lengths (L/H=0.20) correlates with suboptimal ventilation performance. Both ventilation intensity and efficiency are positively correlated with increases in Ra and Δθ. This research quantitatively delineates these relationships, providing a theoretical foundation for the design of natural ventilation systems in sustainable buildings using combined solar chimneys. © 2024, The Authors. All rights reserved.

关键词： Computational fluid dynamics

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Enhancing Solar Chimney Performance with Novel Passive Optimization Strategies for Dual Carbon Goals

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SSRN 2024年

作者： Han, Mengjiao Cui, Huimin Han, Zhiming Liu, Qingkuan School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Mathematics and Physics Shijiazhuang Tiedao University Shijiazhuang050043 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Shijiazhuang050043 China

The development of green buildings plays a pivotal role in achieving "dual carbon" goals. This study focuses on the Combined Solar Chimney (CSC) as an effective method for utilizing solar energy to enhance building ventilation and heat exchange, thereby reducing air-conditioning energy consumption. We introduce two innovative passive optimization measures: deflectors and segmented heat-absorbing walls. Using numerical simulations, we analyze the impact of five control parameters—the angle and length of the straight deflector, the central angle of the curved deflector, the number of heat-absorbing wall segments, and the Rayleigh number (Ra)—on CSC performance. Our findings detail the temperature distribution and the vertical vortex dimensions to elucidate underlying mechanisms. Results indicate that air changes per hour (ACH) can be significantly improved with the implementation of deflectors and segmented walls. Optimal deflector configurations are identified as a 25° angle, a 0.375 length-to-width ratio (l/W), and a 60° central angle. The study recommends using two heat-absorbing wall segments for practical applications. When both measures are applied, ventilation performance can be enhanced by up to 25.71%. Additionally, this research establishes quantitative relationships between the control parameters, ACH, and heat exchange efficiencies, providing a theoretical foundation for practical engineering designs. © 2024, The Authors. All rights reserved.

关键词： Solar chimneys

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Experimental Investigations on the Wind Load Interference Effects of Single-Axis Solar Tracker Arrays

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SSRN 2022年

作者： Ma, Wenyong Zhang, Weida Zhang, Xiaobin Chen, Wei Tan, Qiang School of Civil Engineering Shijiazhuang Tiedao University Hebei 050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Hebei 050043 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Jiangsu Guoqiang Singsun Energy Co. Ltd 213300 China

Aiming at the interference effect of wind loads on single-axis solar tracker arrays, this study conducts rigid-model pressure measurement wind tunnel tests on a single-row solar tracker and solar tracker arrays. The effects of the tilt angle and wind direction on aerodynamic characteristics are examined. The basic characteristics of the wind-induced interference effects of a single-axis solar tracker array are clarified. The results reveal that when the tilt angle is small, the interference effect is small, the tilt angle increases, the interference effect becomes stronger. From the mean pressure and torque coefficients, the interference effect is mainly manifested as a shielding effect. Based on the fluctuating pressure and torque coefficients, the interference effect appears as a shielding effect and an amplification effect in small- and large-tilt angle ranges, respectively. The wind load power spectrum of the solar modules in the rear-row of the solar tracker arrays presents remarkable frequency peaks, and experiences stronger wind-induced vibrations than the front-row modules. The influence of the wind direction results in nonuniform distributions of wind loads along the length of the solar tracker. Thus, the enhancement in wind loads on the edge areas of solar arrays caused by the wind direction should be considered. © 2022, The Authors. All rights reserved.

关键词： Wind stress

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