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Experimental investigation on the cracking behavior of 3D printed kinked fissure

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Science China(Technological Sciences) 2018年第12期61卷 1872-1881页

作者： MA GuoWei DONG QianQian WANG Li College of architecture and civil engineering Beijing University of Technology school of civil and transportation engineering Hebei University of Technology

Uniaxial compression tests were carried out for 3 D printed samples having various types of kinked fissures by using the rock mechanics servo-controlled testing system. Photo-elastic technique is adopted to characterize and visualize the stress distribution and evolution of 3 D printed models subjected to vertical compression. The stress field in the loading process can clearly be captured via a high-speed camera. The results showed that fringes around the kinked fissure tips formed a central symmetrical interference fringe pattern, and failure firstly occurred at interference fringe of highest order. Two failure types i.e. tip-cracking and non-tip-cracking are categorized on the basis of crack propagation pattern of 3 D printed samples. Tensile crack propagation of wing cracks is the main form of failure of the antisymmetric kinked fissures, but the inclination of the branch fissures also played a key role on the location of initial fracture. The finite element method was applied to numerically simulate the process of crack propagation. The isochromatic fringe patterns are in good agreement with the experimental investigation. The current work gives an insight for implication of advanced technique to quantify and visualize the distribution of stress field, and provides further understanding of kinked fissure behavior at failure.

关键词： kinked fissure 3D printing cracking behavior stress field non-tip-cracking photo-elasticity

Heterogeneous traffic flow modeling with drivers’ timid and aggressive characteristics

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Chinese Physics B 2021年第10期30卷 219-230页

作者： Cong Zhai Weitiao Wu Songwen Luo school of civil engineering and transportation South China University of TechnologyGuangzhou 510641China school of transportation and civil engineering and architecture Foshan UniversityFoshan 528000China

The driver’s characteristics(e.g.,timid and aggressive)has been proven to greatly affect the traffic flow performance,whereas the underlying assumption in most of the existing studies is that all drivers are *** the real traffic environment,the drivers are distinct due to a variety of factors such as personality *** better reflect the reality,we introduce the penetration rate to describe the degree of drivers’heterogeneity(i.e.,timid and aggressive),and proceed to propose a generalized heterogeneous car-following model with different driver’s *** the linear stability analysis,the stability conditions of the proposed heterogeneous traffic flow model are obtained based on the perturbation *** impacts of the penetration rate of drivers with low intensity,the average value and standard deviation of intensity parameters characterizing two types of drivers on the stability of traffic flow are analyzed by *** show that higher penetration of aggressive drivers contributes to traffic flow *** average value has a great impact on the stability of traffic flow,whereas the impact of the standard deviation is trivial.

关键词： heterogeneous car-following model driver characteristic penetration rate stability

Effect of Friedel's salt on strength enhancement of stabilized chloride saline soil

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Journal of Central South University 2017年第4期24卷 937-946页

作者： CHENG Yin LI Zhan-guo HUANG Xin BAI Xiao-hong school of transportation Science and engineering Beihang University College of architecture and civil engineering Taiyuan University of Technology

In the field of soil stabilization, only calcium silicate hydrate(CSH) and ettringite(AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fill, an artificial chloride saline soil, and a non-saline soil were stabilized by Portland cement(PC) and PC with Ca(OH)_2(CH) with different contents. A series of unconfined compressive strength(UCS) tests of stabilized soil specimen after curing for 7 d and 28 d were carried out, and the hydration products and microstructure of the specimens were observed by X-ray diffractometry(XRD), scanning electronic microscopy(SEM), and energy-dispersive X-ray analysis(EDXA). The results showed that the strengths of PC+CH-stabilized chloride saline soils were much higher than those of PC-stabilized soils. A new hydration product of calcium aluminate chloride hydrate, also known as Friedel's salt, appeared in the PC+CH-stabilized chloride saline soils. The solid-phase volume of Friedel's salt expanded during the formation of the hydrate; this volume filled the pores in the stabilized soil. This pore-filling effect was the most important contribution to the significantly enhanced strength of the PC+CH-stabilized chloride saline soils. On the basis of this understanding, a new optimized stabilizer was designed according to the concept that the chloride in saline soil could be utilized as a component of the stabilizer. The strength of the chloride saline soils stabilized by the optimized stabilizer was even further increased compared with that of the PC+CH-stabilized soils.

关键词： chloride saline soil stabilized soil Friedel’s salt strength enhancement effect

Experimental and numerical study on hysteretic performance of SMA spring-friction bearings

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Earthquake engineering and engineering Vibration 2016年第4期15卷 597-609页

作者： Zhuang Peng Xue Suduo Nie Pan Wang Wenting school of civil and transportation engineering Beijing University of Civil Engineering and Architecture Beijing Higher Institution engineering Research Center of Structural engineering and New Materials Beijing University of Civil Engineering and Architecture College of architecture and civil engineering Beijing University of Technology

This paper presents an experimental and numerical study to investigate the hysteretic performance of a new type of isolator consisting of shape memory alloy springs and friction bearing called an SMA spring-friction bearing （SFB）. The SFB is a sliding-type isolator with SMA devices used for the seismic protection of engineering structures. The principle of operation of the isolation bearing is introduced. In order to explore the possibility of applying SMA elements in passive seismic control devices, large diameter superelastic tension/compression NiTi SMA helical springs used in the SFB isolator were developed. Mechanical experiments of the SMA helical spring were carried out to understand its superelastic characteristics. After that, a series of quasi-static tests on a single SFB isolator prototype were conducted to measure its force-displacement relationships for different loading conditions and study the corresponding variation law of its mechanical performance. The experimental results demonstrate that the SFB exhibits full hysteretic curves, excellent energy dissipation capacity, and moderate recentering ability. Finally, a theoretical model capable of emulating the hysteretic behavior of the SMA-based isolator was then established and implemented in MATLAB software. The comparison of the numerical results with the experimental results shows the efficacy of the proposed model for simulating the response of the SFB.

关键词： sliding isolation bearing SMA helical spring hysteretic performance quasi-static test theoretical model

Numerical analysis and field monitoring tests on shallow tunnels under weak surrounding rock

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Journal of Central South University 2015年第10期22卷 4056-4063页

作者：刘建华刘晓明张永杰肖庭 school of Traffic and transportation engineering Changsha University of Science and Technology College of civil engineering Hunan University school of civil engineering and architecture Changsha University of Science and Technology

The Jianpudong No. 4 tunnel is a shallow tunnel, which belongs to Shaoshan County scenic highway in Hunan province, China and whose surrounding rock is weak. According to its characteristics, the field monitoring tests and numerical analysis were done. The mechanical characteristics of shallow tunnels under weak surrounding rock and the stress-strain rule of surrounding rock and support were analyzed. The numerical analysis results show that the settlement caused by upper bench excavating accounts for 44% of the total settlement, and the settlement caused by tunnel upper bench supporting accounts for 56% of the total settlement. The maximum axial force of shotcrete lining is 177.2 k N, which locates in hance under the secondary lining. The maximum moment of shotcrete lining is 5.08 k N·m, which locates in the arch foot. The stress curve of steel arch has three obvious stages during the tunnel construction. The maximum axial force of steel arch is 297.4 k N, which locates in tunnel vault. The axial forces of steel arch are respectively 23.5 k N and-21.8 k N, which is influenced by eccentric compression of shallow tunnel and locates in hance. The results show that there is larger earth pressure in tunnel vault which is most unfavorable position of steel arch. Therefore, the advance support should be strengthened in tunnel vault during construction process.

关键词： tunnel engineering shallow tunnel weak surrounding rock numerical analysis field monitoring tests

Modified stochastic user-equilibrium assignment algorithm for urban rail transit under network operation

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Journal of Central South University 2013年第10期20卷 2897-2904页

作者：朱炜胡昊徐瑞华洪玲 Center of transportation Research School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong University school of transportation engineering Tongji University

Based on the framework of method of successive averages(MSA), a modified stochastic user-equilibrium assignment algorithm was proposed, which can be used to calculate the passenger flow distribution of urban rail transit(URT) under network operation. In order to describe the congestion's impact to passengers' route choices, a generalized cost function with in-vehicle congestion was set up. Building on the k-th shortest path algorithm, a method for generating choice set with time constraint was embedded, considering the characteristics of network operation. A simple but efficient route choice model, which was derived from travel surveys for URT passengers in China, was introduced to perform the stochastic network loading at each iteration in the algorithm. Initial tests on the URT network in Shanghai City show that the methodology, with rational calculation time, promises to compute more precisely the passenger flow distribution of URT under network operation, compared with those practical algorithms used in today's China.

关键词： urban rail transit stochastic user equilibrium assignment algorithm method of successive averages network operation

Effects of Clay on Properties of Polycarboxylate Superplasticizer and Solutions

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Journal of Wuhan University of Technology(Materials Science) 2015年第6期30卷 1167-1171页

作者：王林 WANG Dongmin school of civil and transportation engineering Beijing University of Civil Engineering and Architecture school of Chemical and Environmental engineering China University of Mining and Technology

The infl uence law of clay on mortar fluidity mixed with polycarboxylate superplasticizer was studied. Several methods of inhibiting clay adsorption of polycarboxylate superplasticizer were discussed. The experimental results show that clay has signifi cant effect on the dispersion of polycarboxylate superplasticizer and montmorillonite clay has more signifi cant impact on mortar fluidity than other clays. The pH value and the salts of the solution can affect the adsorption of clay to polycarboxylate superplasticizer. The incorporation of a small amount of sodium hydroxide solution, sodium silicate or cationic surfactants can improve the effect of the clay on the dispersion of polycarboxylate superplasticizer.

关键词： clay polycarboxylate superplasticizer fluidity adsorb

A new continuum model with driver's continuous sensory memory and preceding vehicle's taillight

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Communications in Theoretical Physics 2020年第10期72卷 29-41页

作者： Cong Zhai Weitiao Wu school of transportation and civil engineering and architecture Foshan UniversityFoshan 528000 GuangdongChina school of civil engineering and transportation South China University of TechnologyGuangzhou 510641 GuangdongChina

Car taillights are ubiquitous during the deceleration process in real traffic,while drivers have a memory for historical *** collective effect may greatly affect driving behavior and traffic flow *** this paper,we propose a continuum model with the driver's memory time and the preceding vehicle's *** better reflect reality,the continuous driving process is also *** this end,we first develop a unique version of a car-following *** converting micro variables into macro variables with a macro conversion method,the micro carfollowing model is transformed into a new continuum *** on a linear stability analysis,the stability conditions of the new continuum model are *** proceed to deduce the modified KdV-Burgers equation of the model in a nonlinear stability analysis,where the solution can be used to describe the propagation and evolution characteristics of the density wave near the neutral stability *** results show that memory time has a negative impact on the stability of traffic flow,whereas the provision of the preceding vehicle's taillight contributes to mitigating traffic congestion and reducing energy consumption.

关键词： memory time preceding vehicle's taillight continuum model stability modified KdV-Burgers equation

An Integrated Hydrodynamics and Control Model of A Tethered Underwater Robot

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China Ocean engineering 2018年第5期32卷 557-569页

作者： WU Jia-ming XU Ying TAO Long-bin YU Miao DOU Yi-zhe Department of Naval architecture and Ocean engineering School of Civil Engineering and TransportationSouth China University of Technology Department of Naval architecture Ocean & Marine EngineeringUniversity of Strathclyde

An integrated hydrodynamics and control model to simulate tethered underwater robot system is proposed. The governing equation of the umbilical cable is based on a finite difference method, the hydrodynamic behaviors of the underwater robot are described by the six-degrees-of-freedom equations of motion for submarine simulations, and a controller based on the fuzzy sliding mode control(FSMC) algorithm is also incorporated. Fluid motion around the main body of moving robot with running control ducted propellers is governed by the Navier–Stokes equations and these nonlinear differential equations are solved numerically via computational fluid dynamics(CFD) technique. The hydrodynamics and control behaviors of the tethered underwater robot under certain designated trajectory and attitude control manipulation are then investigated based on the established hydrodynamics and control model. The results indicate that satisfactory control effect can be achieved and hydrodynamic behavior under the control operation can be observed with the model; much kinematic and dynamic information about tethered underwater robot system can be forecasted, including translational and angular motions of the robot, hydrodynamic loading on the robot, manipulation actions produced by the control propellers, the kinematic and dynamic behaviors of the umbilical cable. Since these hydrodynamic effects are fed into the proposed coupled model, the mutual hydrodynamic influences of different portions of the robot system as well as the hydrological factors of the undersea environment for the robot operation are incorporated in the model.

关键词： tethered underwater robot umbilical cable ducted propeller fuzzy sliding mode control CFD trajectory and attitude control