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Spatio-temporal variations in air/ground freezing–thawing indices along the China–Nepal Highway during 1987–2017

Journal of Mountain Science 2025年第2期22卷 521-536页

作者： ZHANG Tianqi LUO Tao ZHANG Chonglei YU Wenbing PEI Wansheng shaanxi key laboratory of safety and durability of concrete structures Xijing UniversityXi’an 710123China State key laboratory of Mountain Hazards and Engineering Resilience Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China Institute of Future Civil Engineering Science and Technology Chongqing Jiaotong UniversityChongqing 400074China key laboratory of Cryospheric Science and Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given ***-depth analysis of the freezing-thawing indices not only enables the prediction of permafrost distribution and its dynamic changes,but also facilitates the assessment of damage risk to infrastructure under freeze-thaw *** this paper,the air/ground freezing–thawing indices from 1987 to 2017,based on daily temperature observations from meteorological stations along the China–Nepal Highway(CNH),were calculated,and their spatial and temporal variation patterns were *** results showed that:(1)Both mean annual air temperature and mean annual ground surface temperature along the CNH fluctuated upward,with climate tendency rates of 0.43 and 0.52.C·(10a)~(-1),respectively;(2)The number of days with negative air temperature and ground temperature showed fluctuated downward,with change rates of-8.6 and-8.3 d·(10a)~(-1),respectively;(3)The ranges of air freezing index,air thawing index,ground freezing index,and ground thawing index over the years were 157.05-458.88°C·d,2034.20-2560.73°C·d,108.78-396.83°C·d,and 3515.25-4288.67°C·d,*** climate tendency rates were-5.42,10.22,-6.79,and 12.14.C·d·a-1,respectively,showing a general warming trend;(4)The air freezing index,ground freezing index,and ground thawing index changed abruptly in 1999,2000,and 2002,respectively,evincing significant changes after *** research results can provide a basis for the risk assessment of freezing–thawing erosion and the prevention and control of permafrost engineering diseases along the CNH.

关键词： China–Nepal Transportation Corridor China–Nepal Highway Freezing–thawing indices Spatio–temporal change

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Dynamic properties of low-density expandable polystyrene concrete materials

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Defence Technology(防务技术) 2025年第1期43卷 94-108页

作者： Jue Han Hualin Fan Army Engineering University of PLA Nanjing 210007China Research Center of Lightweight structures and Intelligent Manufacturing State Key Laboratory of Mechanics and Control of Aerospace StructuresNanjing University of Aeronautics and AstronauticsNanjing 210016China Henan International Joint laboratory of Dynamics of Impact and Disaster of Engineering structures Department of Civil EngineeringNanyang Institute of TechnologyNanyang 473004China

Expanded polystyrene(EPS)concrete,known for its environmental friendliness,energy absorption capacity,and low impedance,has significant potential application in the fields of wave absorption and vibration *** study designed and prepared EPS concrete materials with four levels of ***-static uniaxial compression and Split Hopkinson Pressure Bar(SHPB)impact tests were conducted to obtain stress-strain curves,elastic moduli,failure modes,energy absorptions,and strain rate effects of the EPS concrete under quasi-static and dynamic loading *** influences of density on various performance indicators were *** combining the Zhu-Wang-Tang(ZWT)constitutive model with a modified elastic-brittle model,a modified dynamic constitutive model was *** accuracy of the model was validated by the experimental *** results indicate that the addition of EPS particles enhances the ductility of the EPS *** EPS concrete has significant strain rate effect,which gets stronger as density *** modifiedconstitutive model accurately characterizes the dynamic stress-strain curves of the EPS concrete.

关键词： EPS concrete Impact behavior Constitutive model SHPB test

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Analysis on Pore Structure of Non-Dispersible Underwater concrete in Saline Soil Area

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Journal of Renewable Materials 2021年第4期9卷 723-742页

作者： Fang Liu Baomin Wang Mengsai Wang Xiaosa Yuan shaanxi key laboratory of safety and durability of concrete structures Xijing UniversityXi’an710123China School of Civil Engineering Dalian University of TechnologyDalian116023China

In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore characteristics of concrete,analyze the pore characteristics,porosity and pore distribution of concrete in different hydration stages,and reveal the relationship between pore structure and permeability of *** results show that the pore-size distribution of concrete in fresh water condition is better than that in sulfate environment and mixed salt environment,and therefore,sulfate as well as mixed salt are not conducive to the development of pore structure of non-dispersible underwater concrete;chlorine salt has little effect on the pore structure of nondispersible underwater concrete;under the three conditions of sulfate,chlorine and mixed salt,the porosity of concrete mixed with slag powder is lower than that of concrete without slag *** results indicate that the addition of slag powder can ameliorate the pore size distribution of non-dispersed underwater concrete,reduce the porosity,and make the concrete structure more compact,which is beneficial to improve the permeability resistance of concrete at the macro level.

关键词： Non-dispersible underwater concrete slag powder saline soil mercury intrusion porosimetry(mip) pore structure

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Effect of Recycled Mixed Powder on the Mechanical Properties and Microstructure of concrete

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Journal of Renewable Materials 2022年第5期10卷 1397-1414页

作者： Chao Liu Huawei Liu Jian Wu shaanxi key laboratory of safety and durability of concrete structures Xijing UniversityXi’an710123China School of Civil Engineering Xi’an University of Architecture and TechnologyXi’an710055China

In this paper,recycled bricks and recycled concrete were applied to prepare eco-friendly recycled mixed powder(RMP)cementitious material,as a supplementary to replace conventional cement for improve the recycling of construction and demolition *** on the effect of cementitious materials on the hydration of silicate cement,the effects of RMP on the workability,mechanical properties and microstructure of recycled mixed powder concrete(RMPC)with the different replacement ratios and the 8:4 and 6:4 mixing ratio of recycled brick powder(RBP)and recycled concrete powder(RCP)were *** results showed that the fluidity of the mix decreased with increasing of the replacement ratio and the mixing ratio of RBP and RCP,but the influence of the fluidity was smaller within 15%replacement *** the replacement ratio increases,the internal pore structure of RMPC tends to be loose and porous,which exhibits a significant pore volume distribution *** number of large capillaries was considerably increased at replacement ratio of 45%.The 7 d compressive strength of RMPC was slightly lower than that of ordinary *** compressive and splitting tensile strengths of RMPC at 28 d increased by 4.2%and 10.1%,respectively,with increasing curing age at 15%replacement ratio and 6:4 mixing *** RMPC mechanical strengths with RBP and RCP at the mixing ratio of 6:4 was higher than those of 8:***,a basis for the recycling of RBP and RCP in the construction industry can be provided by the results of this study.

关键词： Recycled concrete recycled mixed powder pore structure mechanical properties

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Influences of Ignition Temperature, Urea-to-Metal Nitrates Molar Ratio, and Further Calcination on Synthesis of C_4AF via the SPCR Method

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Journal of Wuhan University of Technology(Materials Science) 2018年第5期33卷 1168-1175页

作者： LI Yang HE Zhen JIANG Rui State key laboratory of Water Resources ＆ Hydropower Engineering Science Wuhan UniversityWuhan 430072China shaanxi key laboratory of safety and durability of concrete structures Xo＇ing UniversityXi＇an 710123China

The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as *** decomposition behavior of dried gels,phase identification and crystallinity of synthesized C4AF,and impact of urea to metal nitrates（UR/MN）molar ratio on synthesis effect were investigated with the aid of differential thermogravimetric analysis,X-ray diffraction and Fourier transform inferred *** is found that pure C4AF can be prepared by the SPCR method in 2 h at 500℃.The UR/MN molar ratio plays a significant role in the thermal decomposition behavior of dried gel,purity,crystallinity and crystallite size of synthesized *** temperature should be not lower than 500℃but higher temperatures were *** trace of free lime in synthesized C4AF is detected and calcium carbonate is the transition *** calcining the synthesized C4AF at high temperatures is beneficial for increasing crystallinity,purity and crystallite *** activation energy of the further calcination process is 119.6 kJ/*** is more efficient to improve the synthesis effect by increasing UR/MN molar ratio than further calcination at high temperatures.

关键词： C4AF combustion synthesis self-propagating brownmillerite purity low temperature

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Evolution of suspension bridge structural systems,design theories,and shape-finding methods:A literature survey

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第2期11卷 225-244页

作者： Wenming Zhang Genmin Tian Yupeng Chen key laboratory of concrete and Pre-stressed concrete structures of Ministry of Education Southeast UniversityNanjing 210096China State key laboratory of safety Durability and Healthy Operation of Long Span BridgesSoutheast UniversityNanjing 210096China

Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two *** performance under dead and live loads depends on their structural and main cable systems,while cablesupported bridges especially rely on the design analysis and construction control of the main *** literary survey systematically analyzes the research progress and state-ofthe-art status quo in the structural systems and design theories of suspension bridges,focusing on the structural systems,main cable shape analyses,live load effect analyses,and emerging lucrative research *** than 100 reliable references have been surveyed.(1)Multi-span or multi-main cable schemes appeal to increasing attention,which may become a better choice in terms of structural systems in scenarios with extremely long spans and heavy *** cable layouts,such as spatial main cables and hybrid cable-stayed suspension systems have also become feasible approaches for enhancing structural stiffness.(2)The shape-finding analysis during the construction phase is more complex and has more essential factors than that of the completed bridge *** theories combining analytical methods and finite element methods are more suitable for the shape-finding analysis of complex cable systems than any single theory of the two,especially for novel cable systems.(3)The live load effect analysis methods based on traditional deflection theory or modified/improved deflection theories still have wide applications,but the refined theory of treating hangers as discrete members is also constantly developing,which is expected to provide new ideas for more complex structural analysis under the different types of live loads and their distribution forms.

关键词： Suspension bridges Structural system Cable analysis Shape-finding analysis Construction control and calculation Live load effect

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Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints

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Journal of Central South University 2015年第4期22卷 1536-1547页

作者：孙建邱洪兴 key laboratory of concrete and Prestressed concrete structures of Ministry of Education (Southeast University)

To study the seismic performance and load-transferring mechanism of an innovative precast shear wall(IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame(CSF) distributes uniformly; and each high-strength bolt(HSB)primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly; and the HSBs at both ends of the CSF transfer the maximum shear forces.

关键词： precast shear wall vertical joint seismic behavior high-strength bolt connecting steel frame

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Theoretical modeling of steel reinforced ECC column under eccentric compressive loading

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Science China(Technological Sciences) 2015年第5期58卷 889-898页

作者： PAN JinLong GU Jie CHEN JunHan key laboratory of concrete and Prestressed concrete structures of Ministry of Education Southeast University

Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.

关键词： compressive reinforced ultimate durability constitutive reinforcement tensile columns carrying calculating

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Synthesis Mechanism and Material Characterization of C4AF Obtained by the Self-propagating Combustion Reaction Method

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Journal of Wuhan University of Technology(Materials Science) 2018年第5期33卷 1099-1107页

作者： HE Zhen LI Yang shaanxi key laboratory of safety and durability of concrete Structure Xoing UniversityXi＇an 710123China State key laboratory of Water Resources ＆ Hydropower Engineering Science Wuhan UniversityWuhan 430072China

To investigate the influence of preparation process on the properties of synthesized C4AF,the powder was prepared via the self-propagating combustion reaction（SPCR）method using urea as fuel and metal nitrates as cation *** mechanism of the SPCR method,calculation and adjusting principles of urea dosage were detailedly *** characterization of synthesized C4AF was performed with the aid of X-ray diffractometry,Fourier transform infrared spectrometry,scanning electron microscopy,energydispersive X-ray spectroscopy,^27Al nuclear magnetic resonance and isothermal microcalorimetric *** content of transition phase of calcium carbonate in synthesized C4AF was determined by quantitative analysis of X-ray *** was found that there was no difference in the hydration behavior of C4AF synthesized by the SPCR method and the traditional solid-state reaction（SSR）method.C3AH6 and amorphous iron（III）hydroxide（Fe（OH）3）would be formed during the hydration of C4AF while CH *** size of synthesized C4AF was 16.1 A and the apparent activation energy was 36.2 kJ/*** condition of Al in C4AF can be detected by ^27Al NMR technique,but the peaks were broadened and the intensities were relatively low,supporting the use of ^27Al NMR for the quantitative analysis of C3A in Portland cements.

关键词： C4AF self-propagating SPCR urea ^27Al NMR apparent activation energy

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Failure mechanism of full-size concrete filled steel circle and square tubes under uniaxial compression

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Science China(Technological Sciences) 2015年第10期58卷 1638-1647页

作者： CAI JingMing PAN JinLong SHAN QiFeng key laboratory of concrete and Pre-stressed concrete structures of Ministry of Education Southeast University

In this paper, the failure mechanisms of full-size concrete filled steel tubes(CFST) under uniaxial compression were investigated with nonlinear finite element method. Existing experimental results were employed to verify the validity of the finite element models of CFST specimens. Then, the numerical analysis was further conducted to study the mechanical behaviors of full-size CFST columns with circular and square cross sections under uniaxial compression. The simulation results indicate that the distribution of the contact pressure between circular steel tube and core concrete is much more uniform than that between square steel tube and concrete, resulting in much higher confinement and more efficient interaction between steel tube and core concrete in circular CFST columns, as well as ultimate load capacity and ultimate displacement. Extensive parametric analysis was also conducted to examine the effect of various parameters on the uniaxial compression behaviors of circular and square CFST columns.

关键词： CFST uniaxial compression finite element analysis interaction mechanism

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