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Acoustic emission characteristics of damage evolution of multi-scale fiber reinforced rubberized concrete under uniaxial compression and tension after being subjected to high temperatures

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Frontiers of structural and Civil Engineering 2024年第8期18卷 1237-1266页

作者： Shaoqi ZHANG Yao ZHANG Qianru LEI Yumeng YANG Yichao WANG Fei XU Zhiguo YAN Hehua ZHU Laboratory of Fire Safety School of Safety Engineering and Emergency ManagementShijiazhuang Tiedao UniversityShijiazhuang 050043China Structural Health Monitoring and Control Key Laboratory of Hebei Province Shijiazhuang Tiedao UniversityShijiazhuang 050043China Department of Geotechnical Engineering Tongji UniversityShanghai 200092China

Recently developed multi-scale fiber(i.e.,CaCO3 whisker,polyvinyl alcohol(PVA)fiber,and steel fiber)reinforced rubberized concrete exhibits excellent mechanical properties and spalling resistance at high *** of macro properties such as strength and Young’s modulus cannot reveal and characterize damage mechanisms,particularly those relating to the multi-scale fiber strengthening *** this study,acoustic emission(AE)technology is applied to investigate the impact of multi-scale fiber on the damage evolution of rubberized concrete exposed to high temperatures,under the uniaxial compression and tension loading *** mechanical properties,AE event location,peak frequency,b-value,the ratio of rise time to amplitude(RA),average frequency(AF)values,and AE energy of specimens are *** results show that the number of events observed using AE gradually increases as the loading *** crumb rubber and fibers inhibit the generation and development of the *** is concluded that both the peak frequency and b-value reflect the extension process of *** the cracks develop from the micro scale to the macro scale,the peak frequency tends to be distributed in a lower frequency range,and the b-value decreases *** the peak stress point,the AE energy increases rapidly and the b-value *** specimens without multi-scale fibers exhibit brittle failure,while the specimens with fibers exhibit ductile *** addition,adding multi-scale fibers and crumb rubber increases the peak frequency in the medium and high frequency ranges,indicating a positive effect on inhibiting crack *** being subjected to high temperatures,the maximum and minimum b-values decrease,reflecting an increase in the number of initial cracks due to thermal ***,the RA and AF values are used to classify tensile and shear *** specimens fracture with more shear cracks under compression,and there are more tensile

关键词： multi-scale fibers acoustic emission fracture damage evolution rubberized concrete

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Full-Scale Cutting Experiments of Different Granite Integrity Using Tunnel Boring Machine Disc Cutter

SSRN

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SSRN 2022年

作者： Sun, Hao-Kai Gao, Yang Chen, Yong Geotechnical and Structural Engineering Research Center Shandong University Jinan250061 China Key Laboratory for Structure Health Monitoring and Control in Hebei Province Shijiazhuang Tiedao University Shijiazhuang050043 China

The complex geological conditions of tunnels with tunnel boring machine make geological exploration very difficult. To explore the method of predicting the rock mass integrity based on the cutterhead vibration signal, the mapping relationship between the rock mass integrity, cutter forces, and cutterhead vibration was studied by the full-scale rotary cutting machine. Our finding is that the mean amplitude, the single peak value of the normal force, and the RMS values of the cutterhead vibration all increase with ascending rock mass integrity. The average amplitude and single peak value decrease, and the RMS value increase with the increase of the rotation speed. The average amplitude increases, the single peak value decreases, and the RMS value increases as the advance speed increase. We demonstrated that there is an obvious corresponding relationship between the normal force and the vibration, and rock mass and operating parameters have significant effects on the vibration characteristics. © 2022, The Authors. All rights reserved.

关键词： Boring machines (machine tools)

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Hpp-Based Evaluation of 17 Thermal Conductivity Models for Frozen Soil

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SSRN 2023年

作者： Zheng, Shuang-Fei Wang, Meng Li, Xu Tai, Bo-Wen Li, Guo-Yu Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong University Beijing100044 China Key Laboratory of Structural Health Monitoring and Control Shijiazhuang Tiedao University Hebei province Shijiazhuang050043 China State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and Resources Chinese Academy Sciences Lanzhou730000 China

Thermal conductivity is a key parameter for coupled thermal-hydro-mechanical calculations, significantly influencing the determination of the water and heat migration in frozen soil. However, during the measurement of thermal conductivity for frozen soil, the accuracy can be affected by the interference of ice and water caused by phase transitions with temperature elevation. Consequently, the experimental data on thermal conductivity for frozen soil is insufficient. In this study, the heat-pulse-probe (HPP) method was adopted to conduct measurements of thermal conductivity in silty clay, sand and sand loam, with the temperature perturbation of less than 0.3°C. Additionally, nuclear magnetic resonance (NMR) experiments were implemented to measure the unfrozen water content, enabling further calculation of the ice content. Furthermore, a literature review was conducted to categorize 17 commonly used thermal conductivity calculation models as normalized and hybrid models. The models were evaluated using the λ-θi-θw experimental data, leading to the following conclusions: Among the seven hybrid models, Zhang model shows the best predictive performance and requires no undetermined parameters, making it easy to apply. Sass model is suitable for soils insensitive to deformation of the frozen volume, such as the sand and sand loam studied in this research. Tian model requires the determination of soil-specific parameters, and when the parameters are appropriate, it demonstrates good predictive performance, as observed for the silty clay. Among the 10 normalized models, Joh, Cot, and Luo models are the three with the smallest errors. The establishment of the Ke function needs to consider variations in ice content during phase transitions and changes in the air volume fraction caused by deformation of the frozen volume. These research findings can provide references for future studies on thermal conductivity. © 2023, The Authors. All rights reserved.

关键词： Thermal conductivity

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Experiments on the effect of helical line on the stay-cable vibration at high Reynolds number

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Zhendong yu Chongji/Journal of Vibration and Shock 2018年第14期37卷 175-179页

作者： Liu, Qingkuan Lu, Zhaoliang Tian, Kaiqiang Hu, Bo Ma, Wenyong Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Hebei Province Key Lab of Structural Health Monitoring and Control Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Engineering Mechanics Shijiazhuang Tiedao University Shijiazhuang050043 China

Cable is one of the basic construction members of a cable-stayed bridge. The wind loads on cables constitute a high proportion of total wind loads on the bridge, and the wind-induced vibration is an important problem of great concern in bridge design. Through a self-designed vibration test system for stay-cables, the vibration model tests for a rigid stay-cables model with diameter of 120 mm as well as for 25 kinds models of stay-cables wound with helical lines were conducted in a wind *** changing rule of the vibration amplitude along with the Reynolds number was analyzed. The results show that winding a helical line on the cable can reduce the Reynolds number effects on it. When the helical line winding spacing is constant, the amplitude trends to decrease along with the increase of helical line diameter. When the helical line diameter is constant, the amplitude trends to decrease along with the decrease of helical line winding spacing. The vibration stability is improved with the increase of helical line diameter and the decrease of helical line winding spacing. © 2018, Editorial Office of Journal of Vibration and Shock. All right reserved.

关键词： Reynolds number

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Effective concrete surface crack detection based on extreme learning machine 8

Effective concrete surface crack detection based on extreme ...

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8th International Conference on structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Wang, Baoxian Zhao, Weigang Zhang, Hao Wang, Xinmin Zhang, Guangyuan Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang050043 China Collaborative Innovation Center of Large Infrastructure Disaster Prevention and Reduction of Hebei Province China

ISBN: (纸本)9781925553055

Concrete surface crack detection has been an important field for the safety of civil engineering structure. However, under the background of high-density data acquiring demand, the existing crack detecting methods could not obtain the favorable efficiency and capability. In this work, we present a novel concrete surface crack detector for efficiently dealing with the massive crack images. Specifically, discrete cosine transformation is firstly utilized to extract the frequency domain characteristics of concrete surface images. Then, with the calculated image frequency features, an emergent learning technique (i.e., Extreme Learning Machine) is exploited to find the optimal separate hyper-plane between the crack object and backgrounds. Experiments on the crack images from the railway ballast-less track slab validate the effectiveness of the proposed method. © 2017 International Society for structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Frequency domain analysis

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Reynolds number effects on mean aerodynamic forces acting on parallel cables of cable-supported bridges

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Gongcheng Lixue/Engineering Mechanics 2017年第3期34卷 189-196页

作者： Du, Xiao-Qing Zhang, Li-Ping Liu, Qing-Kuan Ma, Wen-Yong Liu, Xiao-Bing Department of Civil Engineering Shanghai University Shanghai200072 China Wind Engineering Research Center Shijiazhuang Tiedao University Shijiazhuang050043 China Hebei Province Key Lab of Structural Health Monitoring and Control Shijiazhuang050043 China

Parallel hanger cables and stay cables are used extensively in cable-supported bridges. However, the cross-wind mean lift of downstream cables induced by wake interference received little attention when calculating the wind loads on parallel cables. At Reynolds numbers between 0.9×105~4.6×105 (subcritical Reynolds regime and critical Reynolds regime), the aerodynamic characteristics of twin circular cylinders were investigated along with their relationships with the Reynolds numbers through a series of wind tunnel tests. Results show the mean aerodynamic forces of two circular cylinders in the critical regime were very different from those in the subcritical regime, showing strong Reynolds number effects. Furthermore, at the critical regime, the mean lift coefficients of the downstream circular cylinder discontinuously suffered abrupt change with the increase in the Reynolds number for some arrangements of the cylinders, which might be related to the shift of the flow state between different flow patterns. Under the wake interference of the upstream circular cylinder, the magnitude of the mean lift coefficient on the downstream cylinder was up to 1.25. Therefore, it is necessary to include the effect of mean lift when calculating static wind loads on parallel cables. © 2017, Engineering Mechanics Press. All right reserved.

关键词： Reynolds number

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The influence of surface roughness on the dry galloping of inclined cables

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Gongcheng Lixue/Engineering Mechanics 2017年 34卷 174-178页

作者： Lu, Zhao-Liang Liu, Xiao-Ling Zheng, Yun-Fei Liu, Qing-Kuan Ma, Wen-Yong Liu, Xiao-Bing School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Hebei Province Key Lab of Structural Health Monitoring and Control Shijiazhuang050043 China

Although new cables are covered by smooth polyethylene material, weathering and dust adhesion increase the surface roughness of the cables with the growth of service time. In this paper, the influence of roughness of stay cables on aerodynamic stability was studied. The surface roughness of cables was changed through covering the cable with different sandpapers, and the surface roughness was measured with the SJ-410 high-precision by free vibration wind tunnel test. The influence of surface roughness on the vibration of stay cables at high Reynolds number was studied by vibration experiments. It was shown that the vibration of stay cables was inhibited with the increase of the surface roughness;the Reynolds number effect became weaker with the increase of surface roughness of the stay cable models. © 2017, Engineering Mechanics Press. All right reserved.

关键词： Surface roughness

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Experimental research on wind pressure distribution of cooling towers

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Gongcheng Lixue/Engineering Mechanics 2017年 34卷 269-272页

作者： Tian, Kai-Qiang Qin, Qi-Wei Zheng, Yun-Fei Liu, Qing-Kuan Liu, Xiao-Bing Ma, Wen-Yong School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Hebei Province Key Lab of Structural Health Monitoring and Control Shijiazhuang050043 China

To study the influence of the roughness of cooling tower surface on the flow characteristics, a rigid model of a hyperbolic cooling tower covered with wallpaper was measured in a wind tunnel. The wallpaper was selected by comparing the tested pressure distribution at throat position with that of the load code. Then we studied the wind pressure distribution on the entire model that is covered with the selected wallpaper. The results show that the largest pressure appeared at the throat position. Drag coefficient exceeded the standard value, and was larger at both ends than that in the middle. Mean and fluctuating wind pressure distribution at the edges of the cooling tower shows a significant three-dimensional effect. For cooling tower wind resistance design, it is necessary to focus on the reinforcement of edges. © 2017, Engineering Mechanics Press. All right reserved.

关键词： Reynolds number

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Experimental study on helical line parameters and rain-wind induced vibration control of stay-cables

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Gongcheng Lixue/Engineering Mechanics 2016年第10期33卷 138-144页

作者： Liu, Qing-Kuan Zheng, Yun-Fei Zhao, Shan-Bo Ma, Wen-Yong Liu, Xiao-Bing Chen, Jin-Jie Wind Engineering Research Center Shijiazhuang Tiedao University Shijiazhuang050043 China Hebei Province Key Lab of Structural Health Monitoring and Control Shijiazhuang050043 China

Helical lines are often used to control rain-wind induced cable vibration. Wind tunnel tests were carried out to obtain optimized parameters of helical line, and vibration control effects were analysed for helical line with different parameters including diameter, single or double twine around way, space, when they are twined around different cable model (the diameter is 90 mm, 110 mm, 155 mm, 160 mm respectively). Results show that for same helical line space, vibration control effect becomes better when helical line diameter becomes large;while for same helical line diameter, vibration control effect becomes better when helical line space becomes small;and for same helical line diameter and twine around way, helical line space needs to be small when cable diameter becomes large. Helical line parameters for different cable diameter to control cable vibration were provided. To choose appropriate helical line parameters, main factors, including cable diameter, surface roughness, production and erection procedures, should be considered synthetically. © 2016, Engineering Mechanics Press. All right reserved.

关键词： Wind tunnels

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Experimental research on wind load distribution of four-center-circle coal shed

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Gongcheng Lixue/Engineering Mechanics 2017年 34卷 59-62页

作者： Wang, Xiao-Jiang Zheng, Yun-Fei Liu, Qing-Kuan Liu, Xiao-Bing Ma, Wen-Yong School Of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China HeBei Province Key Lab of Structure Health Monitoring and Control Shijiazhuang050043 China

According to the requirements of engineering design and experimental research, the wind tunnel tests on a large-span coal shed structure for a thermal power plant were carried out. The influence of wind direction angle on wind-load-shape coefficient was studied. After analyzing the shape coefficient of each measuring point under different working conditions, the wind-load-shape coefficients on the structure surface were obtained. The results showed that: the measuring point had the largest volume coefficient when the angle between the measuring point and the incoming wind was among 30 ~ 40 degree;at different wind direction angles, the coefficients at the top and the edge areas of the model were relatively large, therefore, these areas should be strengthened when building a coal shed. © 2017, Engineering Mechanics Press. All right reserved.

关键词： Coal

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