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Zhang X.-D.,China Merchants Chongqing Communications Research and Design Institute Co. | Ding Y.,Ningbo University | Ren X.-C.,University of Iowa
Gongcheng Lixue/Engineering Mechanics | Year: 2013

The extended finite element method (XFEM) provides an effective way for the numerical simulation of the crack propagation process of structures. The implementation method for the numerical simulation of the crack propagation process of concrete structures with the extended finite element method is introduced. The fictitious crack model is adopted to simulate the concrete nonlinear fracture behaviour. The detailed formulations of a two-dimensional quadrilateral element for the finite element analysis are derived. Three schemes are employed to solve the nonlinear system of equations and their implementation procedures are analyzed and summarized. The numerical simulation of an edge-cracked uniaxial tensile concrete plate is conducted and the corresponding results are analyzed.

Chen L.,Chongqing University | Chen L.,China Merchants Chongqing Communications Research and Design Institute Co. | Jin X.,Chongqing University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2012

When the finite element strength reduction method is applied for analysis of slope stability, the resultant safety factors of slope rely on the criteria of instability. Usually the abruptness of displacement of feature parts, connectivity of plastic zone and convergence of numerical calculation are taken as the judging criteria of slope instability. However, there were different views for applications of these three criteria. This paper compares and analyzes the magnitudes of safety factors of three common criteria based on numerical models of general slopes and steep slopes. The results show that all three criteria exhibit good consistency for general slopes, but have large differences for steep slopes. It is found that tensile shearing is not considered in the yield criterion for strength reduction methods, i.e. overestimation of the tensile strength of materials is a critical cause leading to widespread disputes on the three criteria, and this inclusion is verified by calculating the safety factor of stalactites model. Therefore, the finite element strength reduction method should take equal reduction of both tensile strength index and shear strength index into consideration, so as to guarantee correctness of calculation and consistency of the three judging criteria. The strength reduction method in tensile and shearing damages has universal applicability to analysis of slope stability.

Jiang S.,China Merchants Chongqing Communications Research and Design Institute Co. | Wen D.,Chongqing Institute of Coal Science Institute | Zheng S.,Chongqing Jiaotong University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

As the key position of tunnel seismic design, the portal section is extremely vulnerable to foundation failure and structure damage. The longitudinal distances of 100 m in portal section of Galongla tunnel are selected as the prototype to conduct large-scale shaking table test. The research results are shown as follows: (1) The soil around tunnel has obvious amplification effect on the input seismic waves with the frequency near the predomination frequency of soil; and also it has filtering effect on the input seismic waves with high frequency. (2) The tunnel vibrates synchronously with the surrounding soil; and it doesn't show its own natural vibration frequency. The inertial force has little effect on underground structure's seismic response. So the key point of tunnel's anti-seismic research is failure prevention of surrounding rock under the earthquake; and the main purpose of structure's aseismic design is to reduce the structure damage from the failure of its surrounding rock. (3) The absorbers and aseismatic joints don't change the spectrum characteristics of lining; but they can increase the peak acceleration of lining. So, the damping effect should not be judged by the acceleration magnified coefficient at these places. The research results have important application value to aseismic design and shock absorption design of tunnel.

Zhang X.D.,China Merchants Chongqing Communications Research and Design Institute Co.
Advanced Materials Research | Year: 2014

A scheme is presented for the free vibration analysis of beam-like structures containing a crack with the extended finite element method(XFEM). The scheme is compared with the traditional scheme with the finite element method. The natural frequency of a cantilever beam is analyzed using both the methods and the results are compared. A new method for the damage identification of a cantilever beam containing a crack is then presented. © (2014) Trans Tech Publications, Switzerland.

Song G.,China Merchants Chongqing Communications Research and Design Institute Co.
Applied Mechanics and Materials | Year: 2013

Time-varying linear quadratic Gaussian (LQG) control for vibration of coupled vehiclebridge system is studied. The vehicle is modeled as a moving mass model with three degrees of freedom, which consists of vehicle body, bogie and wheel. Active suspensions are adopted for the primary and secondary ones, and the control forces are produced by two actuators placed between the bogie and wheel, and between the vehicle body and the bogie, respectively. Vehicle-bridge coupling systems are time-dependent, which lead to the time-varying Riccati differential equation and the time-varying Kalman-Bucy filter equation in the LQG controller design. However, both of them are solved precisely via precise integration method and symplectic conservative perturbation method. In the example, the time history responses of the bridge and the vehicle were calculated respectively for the vehicle with passive suspensions or with active suspensions. Numerical results show that with active suspensions adopted, ride comfort can be improved when the vehicles passing through the bridge. © 2013 Trans Tech Publications Ltd, Switzerland.

Yao J.-J.,China Merchants Chongqing Communications Research and Design Institute Co. | Li J.,China Merchants Chongqing Communications Research and Design Institute Co.
Bridge Construction | Year: 2013

The north main bridge of the Xiazhang Sea-Crossing Bridge is a steel box girder cable-stayed bridge with double pylons, double cable planes and with a main span 780 m. The anchorage for the stay cables of the bridge at the main girder is of the anchor tensile plate structure. For the zone under the anchor tensile plate is the place where the stress concentration is most notable, to improve the structural force condition of the zone and to find out the optimal scheme for the structural transition in the zone, the finite element software ANSYS was used to build up the sectional models for the complete anchor tensile plate structure. The stress of the different structural transition types of the zone was analyzed and the plastic strain thereof was compared, respectively using the models of the elastic material and ideal elastoplastic material. The results of the analysis reveal that with the increase of the curvature radius of the transition zone, the maximum stress value of the stress concentration zone will be gradually reduced and the range of the plastic zone will accordingly change. In terms of the comparison and analysis and in regard of the requirement for tight arrangement of the anchor tensile plate structure, the 1/4 round arc transition type with a radius of 40 mm is selected for the transition zone of the anchor tensile plate for the north main bridge.

Li C.,China Merchants Chongqing Communications Research and Design Institute Co.
Energy Education Science and Technology Part A: Energy Science and Research | Year: 2014

To use the energy - quantity conversion relation on water contained in soils become current study trend to estimate subgrade moisture. Subgrade moisture of highway in aridity regions is significantly affected by climate conditions. Along with field investigation of subgrade moisture in typical areas of aridity regions, the authors realized characteristics of moisture equilibria of subgrade and distribution law of rainfall infiltrated into subgrade soils. The authors selected Thornthwaite moisture index (TMI) as index of climate factors. Through correlation analysis of influencing factors of moisture, the authors established climatic effect model to express moisture equilibria of subgrade with TMI and weighted plasticity index as parameters. The authors collected data of field investigation to verify the acceptance of climatic effect model. The results show that climatic effect model is more precise than groundwater table model in quantitative expression of influence of environment factors on subgrade moisture for aridity regions. The absolute error and algebraic error of climatic effect model is 14.86% and 3.36% respectively. And those of groundwater table model is 56.09% and 22.10% respectively. © Sila Science. All rights reserved.

Li J.,China Merchants Chongqing Communications Research and Design Institute Co.
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2016

A novel melt blending method was adopted to prepare polyethylene glycol(PEG)/unsaturated polyester resin (UPR) composites as shape-stabilized phase change materials (PEG/UPR SS-PCMs) with various PEG mass fractions for thermal energy storage. In SS-PCMs, PEG serves as latent heat storage material and silica gel acts as supporting material to keep the stable shape of the composites during the phase transition. The thermal property, thermal stability, chemical structure, the physical and chemical action between the components of the SS-PCMs and crystallization properties of SS-PCMs were studied by DSC, TG, XRD and FT-IR. Results show that the terminal hydroxy groups of PEG respectively enter into addition reaction and intermolecular dehydration reaction with the carbon-carbon double bond and the terminal hydroxy groups or terminal carboxyl groups of UPR or cured UPR, and thus produce ether or ester; the strong chemical acting force is formed, which hinders free movement of PEG and demonstrates a solid-solid phase change behavior which is different from that when it moves freely, so the phase change temperature of SS-PCMs with various PEG mass fractions (about 60℃) is higher than pure PEG, and the phase change enthalpies (80.1~133.7 J/g) are 9.1%~17.4% lower than the theoretical phase change enthalpies. The intermediate connectors of PEG are ether groups that can move freely, and the amount of the terminal hydroxy groups is small, most segments of PEG can crystallize and display phase change behavior, and its crystallization property is stable. In addition, there is no thermal degradation in SS-PCMs below 382.6℃, thus it can be concluded that the composites have a high thermal stability. © 2016, Editorial Board of Polymer Materials Science & Engineering. All right reserved.

Liu Y.,China Merchants Chongqing Communications Research and Design Institute Co. | Yang J.,China Merchants Chongqing Communications Research and Design Institute Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

Granite soils are widely distributed over the South China. With the development of highways, there have been more and more granite soil high slopes along highways. The prestressed cables frame is a common method to reinforce the granite soil high slopes. Through field test on a actual slope of Shantou-Jieyang highway, the internal force distribution and the counterforce endured of frame, the transferring rules of anchoring force in the soil, and the tensile force distribution rules of each section of cable. The results are very valuable to guide the design and construction of similar projects.

Wang J.-J.,Chongqing Jiaotong University | Zhang H.-P.,Chongqing Jiaotong University | Tang S.-C.,China Merchants Chongqing Communications Research and Design Institute Co. | Liang Y.,Chongqing Jiaotong University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013

This paper focuses on the effects of particle size distribution on shear strength of accumulation soil. A series of direct shear box tests and triaxial tests were performed to characterize the shear strength of the accumulation soil. Results from the direct shear tests indicate that the range of the angle of shearing resistance of the accumulation soil is 33.5-54.6°, and those from the triaxial tests indicate that the angle is 37.2-50.7°. The basic properties of the soil, such as median particle diameter, coefficient of uniformity, and gravel content, were used to analyze the effects. The angle of shearing resistance is generally increasing with increasing median particle diameter and gravel content and decreasing with increasing coefficient of uniformity. © 2013 American Society of Civil Engineers.

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