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Frontiers of Structural and Civil Engineering

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, Volume 11 Issue 3 Previous Issue   
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Hierarchical approach for fatigue cracking performance evaluation in asphalt pavements
Front. Struct. Civ. Eng.. 2017, 11 (3): 257-269.   DOI: 10.1007/s11709-017-0410-1
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In this paper, a hierarchical approach is proposed for the evaluation of fatigue cracking in asphalt concrete pavements considering three different levels of complexities in the representation of the material behaviour, design parameters characterization and the determination of the pavement response as well as damage computation. Based on the developed hierarchical approach, three damage computation levels are identified and proposed. The levels of fatigue damage analysis provides pavement engineers a variety of tools that can be used for pavement analysis depending on the availability of data, required level of prediction accuracy and computational power at their disposal. The hierarchical approach also provides a systematic approach for the understanding of the fundamental mechanisms of pavement deterioration, the elimination of the empiricism associated with pavement design today and the transition towards the use of sound principles of mechanics in pavement analysis and design.

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Multiscale mechanical modeling of hydrated cement paste under tensile load using the combined DEM-MD method
Yue HOU, Linbing WANG
Front. Struct. Civ. Eng.. 2017, 11 (3): 270-278.   DOI: 10.1007/s11709-017-0408-8
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In this paper, a combined DEM-MD method is proposed to simulate the crack failure process of Hydrated Cement Paste (HCP) under a tensile force. A three-dimensional (3D) multiscale mechanical model is established using the combined Discrete Element Method (DEM)-Molecular Dynamics (MD) method in LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). In the 3D model, HCP consists of discrete particles and atoms. Simulation results show that the combined DEM-MD model is computationally efficient with good accuracy in predicting tensile failures of HCP.

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Research Article
Construction risks of Huaying mount tunnel and countermeasures
Haibo YAO, Feng GAO, Shigang YU, Wei DANG
Front. Struct. Civ. Eng.. 2017, 11 (3): 279-285.   DOI: 10.1007/s11709-017-0414-x
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The Chongqing-Guang’an motorway is planned to cross Huaying mount at Jingguan town of Chongqing city. The whole mount is a colossal anticline whose core is consisted of coal measure strata (upper Permian Longtan formation P2l) and the limbs are limestone strata (middle Triassic Leikoupo formation T2l and lower Triassic Jialingjiang formation T1j). The tunneling is full of risks of collapse, gas explosion or gas outburst, water (mud) inrush, gas inrush because of existence of faults, high pressure gas, karst tectonics and coal goafs around the tunnel. In order to cope with the high risk, two main countermeasures were taken to ensure security of construction. One is geology prediction, and the other is automatic wireless real-time monitoring system, which contains monitoring of video, wind speed, poisonous gas (CH4, CO, H2S, SO2), people location, and automatic power-off equipment while gas contents being more than warning threshold. These ascertained the engineering safety effectively.

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Numerical investigation and optimal design of fiber Bragg grating based wind pressure sensor
Xiangjie WANG, Danhui DAN, Rong XIAO, Xingfei YAN
Front. Struct. Civ. Eng.. 2017, 11 (3): 286-292.   DOI: 10.1007/s11709-017-0415-9
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A wind pressure sensor based on fiber Bragg grating (FBG) for engineering structure was investigated in this paper. We established a transaction model of wind pressure to strain and proposed a method of temperature compensation. By finite element analysis, the basic parameters of the sensor were optimized with the aim of maximum strain under the basic wind pressure proposed in relative design code in China taking geometrical non-linearity into consideration. The result shows that the wind pressure sensor we proposed is well performed and have good sensing properties, which means it is a technically feasible solution.

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An investigation on modification mechanism of CH2O-modified low temperature coal tar pitches
Qiang XIN, Shanghong HUANG
Front. Struct. Civ. Eng.. 2017, 11 (3): 293-300.   DOI: 10.1007/s11709-017-0403-0
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Rising oil price has brought huge cost pressure for low grade highway construction, and it is urgent to find alternative resources. At the same time, there are nearly 50000–60000 tons of low temperature coal output in inner Mongolia region, China, which has high toxicity and high polluting. To make the low temperature coal be applicable for road constructions, the formaldehyde is used as cross linking agent, the concentrated sulfuric acid is used as catalyst, and the chemical modification of low temperature coal tar pitch in Inner Mongolia region is investigated. The road performance (softening point, penetration and ductility) of modified low temperature coal are tested. Results shown that the road performance of modified low temperature coal is increased significantly. Modification mechanism of low temperature coal is studied by Scanning Electron Microscopy and other analytical tools. Results show that, in the modified low temperature coal, resin content increases and the resin fiber diameter becomes larger with the increasing of formaldehyde content.

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An investigation on stress distribution effect on multi- piezoelectric energy harvesters
Hailu YANG, Dongwei CAO
Front. Struct. Civ. Eng.. 2017, 11 (3): 301-307.   DOI: 10.1007/s11709-017-0404-z
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With the fast development of piezoelectric materials and due to its green and renewable characteristics, the piezoelectric energy harvesting technology has been paid more and more attention by pavement engineers. The stress distribution will significantly affect the piezoelectric material performance. In this paper, the effects of multiple piezoelectric elements on the generation of electrical energy and output power are studied. In the case of constant external load, the number of the piezoelectric units does not necessarily produce more energy. When the same multi piezoelectric units work together, if the stress state of the piezoelectric units is different, the total output energy affected by the connection mode. For uneven stress distribution, the optimal output mode is that each of the piezoelectric units rectified before connected in parallel.

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A methodology of implementing target mixing ratio for asphalt mixture
Yucheng HUANG, Lun JI, Rui WEN, Ming ZHANG
Front. Struct. Civ. Eng.. 2017, 11 (3): 308-314.   DOI: 10.1007/s11709-017-0405-y
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In order to implement the objective mix design of hot mix asphalt adequately during the construction process, the significance of objective mixing ratio was elaborated, and the variability of materials and its control method were analyzed. An engineering example is used to illustrate the debugging process of asphalt mixture batching & mixing plant and the dynamic quality management methods. The results show that the set of methods can not only implement the objective mixing ratio of hot mix asphalt adequately, but also control production during the construction process effectively.

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Investigation on the performance and detoxification of modified low temperature coal tar pitch
Fengyan SUN, Yu LIU
Front. Struct. Civ. Eng.. 2017, 11 (3): 315-321.   DOI: 10.1007/s11709-017-0386-x
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In this paper, studies on the modification on the low temperature coal tar pitch extracted from coal tar residue in Inner Mongolia are conducted. First, the low temperature coal tar pitch in liquid state is solidified with a higher softening point by chemical crosslinking modification. The modified coal tar pitch can achieve the standard pavement performance requirements. Then, the effects of chemical crosslinking agent and physical modification additives on the mechanical performance and toxic properties of coal tar pitch are investigated. The detoxification mechanism is also studied, which further promote the applicability of modified low temperature coal tar pitch in the pavement constructions.

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Mechanical properties of rock materials with related to mineralogical characteristics and grain size through experimental investigation: a comprehensive review
Wenjuan SUN, Linbing WANG, Yaqiong WANG
Front. Struct. Civ. Eng.. 2017, 11 (3): 322-328.   DOI: 10.1007/s11709-017-0387-9
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Mechanical properties of rock materials are related to textural characteristics. The relationships between mechanical properties and textural characteristics have been extensively investigated for differently types of rocks through experimental tests. Based on the experimental test data, single- and multiple- variant regression analyses are conducted among mechanical properties and textural characteristics. Textural characteristics of rock materials are influenced by the following factors: mineral composition, size, shape, and spatial distribution of mineral grains, porosity, and inherent microcracks. This study focuses on the first two: mineral composition and grain size. ?

This study comprehensively summarizes the regression equations between mechanical properties and mineral content and the regression equations between mechanical properties and grain size. Further research directions are suggested at the end of this study.

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A study on fatigue damage of asphalt mixture under different compaction using 3D-microstructural characteristics
Jing HU, Pengfei LIU, Bernhard STEINAUER
Front. Struct. Civ. Eng.. 2017, 11 (3): 329-337.   DOI: 10.1007/s11709-017-0407-9
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The aim of this paper is investigating the microstructural characteristics of asphalt mixture under different compaction powers. In order to achieve this aim, a test track was built to provide asphalt mixture specimens and X-ray computed tomography (XCT) device was used to scan the internal structure. The aggregate particles and air-voids were extracted using Digital Image Processing (DIP), so the relationship between compaction and air-voids was determined at first, and then, the effect of aggregate particles on the morphology of air-voids can be evaluated, finally, fatigue properties of asphalt mixture with different air-void ratio were measured by indirect tensile fatigue test as well. The research results release the distribution of microstructures in asphalt pavement. 3D fractal dimension is an effective indicator to quantize the complexity of aggregate particles and air-voids; suffering the same compaction power, aggregates cause different constitutions of air-voids in asphalt mixture; investigation in this paper can present the essential relationship between microstructures and fatigue properties.

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Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete pavements
Yanhua GUAN, Ying GAO, Renjuan SUN, Moon C. WON, Zhi GE
Front. Struct. Civ. Eng.. 2017, 11 (3): 338-345.   DOI: 10.1007/s11709-017-0411-0
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The fast-track repair of deteriorated concrete pavement requires materials that can be placed, cured, and opened to the traffic in a short period. Type III cement and Calcium Sulfoaluminate (CSA) cement are the most commonly used fast-setting hydraulic cement (FSHC). In this study, the properties of Type III and CSA cement concrete, including compressive strength, coefficient of thermal expansion (CTE) and shrinkage were evaluated. The test results indicate that compressive strength of FSHC concrete increased rapidly at the early age. CSA cement concrete had higher early-age and long term strength. The shrinkage of CSA cement concrete was lower than that of Type III cement concrete. Both CSA and Type III cement concrete had similar CTE values. Based on the laboratory results, the CSA cement was selected as the partial-depth rapid repair material for a distressed continuously reinforced concrete pavement. The data collected during and after the repair show that the CSA cement concrete had good short-term and long-term performances and, therefore, was suitable for the rapid repair of concrete pavement.

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Study on micro-texture and skid resistance of aggregate during polishing
Zhenyu QIAN, Lingjian MENG
Front. Struct. Civ. Eng.. 2017, 11 (3): 346-352.   DOI: 10.1007/s11709-017-0409-7
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The skid resistance performance of pavement is closely related to the micro-texture of pavement aggregate, while there is very few research on the relationship between micro-texture and the skid resistance. In this paper, the optical microscope is used to acquire the surface morphology of three types of aggregates including basalt, limestone and red sandstone respectively, where a total of 12 indicators are developed based on the surface texture information. The polishing effect on aggregate is simulated by Wehner/Schulze (W/S) device, during the polishing procedure, the skid resistance are measured by British Pendulum Tester (BPT). Based on the results of independent T-test and the polishing resistance analysis, it shows that the surface texture of basalt is significantly different between limestone and red sandstone. Three indicators including the average roughness (Ra), the kurtosis of the surface (Sku) and the mean summit curvature (Ssc) are selected to describe the characteristics of aggregate micro-texture based on the correlation analysis. The contribution of micro-texture to the skid resistance can be described with the secondary polynomial regression model by these indicators.

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Study on the cohesion and adhesion of hot-poured crack sealants
Meng GUO, Yiqiu TAN, Xuesong DU, Zhaofeng LV
Front. Struct. Civ. Eng.. 2017, 11 (3): 353-359.   DOI: 10.1007/s11709-017-0400-3
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Filling crack sealant is a main method to repair cracking of pavement. The cohesion and adhesion of crack sealant directly determine its service performance and durability. However, the competitive mechanism of cohesion and adhesion failure modes is not clear currently. This research proposed two methods to evaluate cohesion and adhesion of crack sealant, and analyzed the influence of temperature on cohesion and adhesion. The effect of moisture on low-temperature performance of crack sealant was also be evaluated by conducting a soaking test. Results show that with the decrease of temperature, the cohesion force of crack sealant increases significantly, while the adhesion force changes little. There is a critical temperature at which the cohesion force equals the adhesion force. When the temperature is higher, the adhesion force will be greater than cohesion force, and the cohesion failure will happen more easily. In contrast, the adhesion failure will happen more easily when the temperature is lower than the critical value. Soaking in 25 °C water for 24–48 hours will slightly improve the low-temperature tension performance of crack sealant. However, soaking in 60 °C water for 24 hours will decrease the failure energy of low-temperature tension and damage the durability of crack sealant.

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Investigation of mechanical performance of prestressed steel arch in tunnel
Yaqiong WANG, Yunxiao XIN, Yongli XIE, Jie LI, Zhifeng WANG
Front. Struct. Civ. Eng.. 2017, 11 (3): 360-367.   DOI: 10.1007/s11709-017-0429-3
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In the traditional tunneling method, the steel arch are often adopted to support surrounding rock to ensure the structural stability. If the steel arch is prestressed in time, tunnel support can effectively prevent the development of rock crack, thereby increasing the overall strength of tunnel support and suppress the deformation of the surrounding rock. Based on the mechanical model of steel arch established in this paper, the stress distribution of steel arch is investigated via the numerical simulation method, and the impact on surrounding rock is also analyzed. Through a field test, the rules of the arch strain distribution are observed and discussed. The results show that the prestressed steel arch structure can provide effective support and the stress gradually decreases from stress point to another arch springing. Furthermore, the stress distribution applied by the prestressed steel arch on the surrounding rock is uniform in a certain extent, and it is suggested that this construction method utilizing the prestressed steel arch to squeeze surrounding rock is feasible from a theoretical view.

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14 articles