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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.

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.

Bu Z.,Ningbo University | Tang G.,China Merchants Chongqing Communications Research and Design Institute Co.
Zhongguo Tiedao Kexue/China Railway Science | Year: 2011

The model of unbonded prestressing precast segmental bridge piers with energy dissipation bars was set up utilizing fiber beam-column element with the OPENSEES program developed by the Pacific Earthquake Engineering Research Center in the U.S. to investigate the pseudo static test procedure. The parametric analysis about the influence of the prestressing level, axial compression ratio and prestressed tendon or conventional rebar ratio upon the earthquake response of the bridge piers and columns was carried out. The results show that raising prestressing level can increase the yield strength but has little effect on the ultimate lateral strength. A total axial compression ratio of 20 to 30 percent of prestressing and superstructure dead load contributes to higher lateral strength and larger equivalent damping ratio of bridge columns. The column has stable lateral strength and energy dissipation ability as the prestressing tendon ratio is between 0.20 and 0.50 percent. The equivalent damping ratio of the bridge piers will be decreased with the increase of tendon ratio. The yield strength, ultimate lateral strength, energy dissipation and equivalent damping ratio will be increased remarkably with the increase of conventional rebar ratio, but the residual displacement will also be increased. The seismic response analysis reveals that the lateral strength can be raised by adding conventional reinforcement in precast segmental bridge piers. The shear at the damage level of precast segmental bridge piers bottom under history excitation is approximately 70 to 90 percent of pseudo static test results. The ultimate displacement of the pier top is only about 50 percent of that in pseudo static tests.

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.

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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