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Zhou H.,Beijing University of Technology | Zhou H.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Wang Y.,Tsinghua University | Yang L.,Beijing University of Technology | Shi Y.,Tsinghua University
International Journal of Fatigue | Year: 2014

Abstract A general methodology for seismic low-cycle fatigue assessment of welded beam-to-column connection in steel moment resisting frames (SMRFs) is presented. Fatigue deformability curves of seven connection categories are elaborated using the available cyclic tests. Inter-storey drift history imposed on each connection of SMRF is generated by seismic dynamic analysis and adopted in fatigue damage calculation based on Palmgren-Miner's rule and the experimentally determined fatigue curve. The most critical connection identified by preliminary fatigue evaluation is refined with solid finite elements in global-local model where the cyclic void growth model is integrated to give a more accurate fatigue prediction including load sequence effects. The proposed approach is applicable to fatigue evaluation of welded connections in SMRFs under earthquakes.© 2014 Elsevier Ltd. All rights reserved.


Li P.-F.,Beijing University of Technology | Li P.-F.,Southwest Jiaotong University | Li P.-F.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Zhou X.-J.,Southwest Jiaotong University
China Ocean Engineering | Year: 2015

Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the country rock that surrounds a tunnel, thereby lowering the arching effect and stratum stability of the structure. In this paper, the mechanical behavior and shape optimization of the lining structure for the Xiang’an tunnel excavated in weathered slots are examined. Eight cross sections with different geometric parameters are adopted to study the mechanical behavior and shape optimization of the lining structure. The hyperstatic reaction method is used through finite element analysis software ANSYS. The mechanical behavior of the lining structure is evidently affected by the geometric parameters of crosssectional shape. The minimum safety factor of the lining structure elements is set to be the objective function. The efficient tunnel shape to maximize the minimum safety factor is identified. The minimum safety factor increases significantly after optimization. The optimized cross section significantly improves the mechanical characteristics of the lining structure and effectively reduces its deformation. Force analyses of optimization process and program are conducted parametrically so that the method can be applied to the optimization design of other similar structures. The results obtained from this study enhance our understanding of the mechanical behavior of the lining structure for subsea tunnels. These results are also beneficial to the optimal design of lining structures in general. © 2015, Chinese Ocean Engineering Society and Springer-Verlag Berlin Heidelberg.


Jiao C.-Y.,Beijing Urban Transportation Infrastructure Engineering Technology Research Center | Jiao C.-Y.,Tongji University | Zhang Y.,Beijing Inno Olympic Real Estate Development Co. | Long P.-H.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Hou S.-W.,Beijing Collaborative Innovation Center for Metropolitan Transportation
Gongcheng Lixue/Engineering Mechanics | Year: 2016

There are three kinds of methods for modeling and analyzing the existing curved girder bridges. They are single-beam method, grillage method and entity method. According to the previous literature, the single-beam method is not so accurate, but it is generally popular because of its higher speed in analyzing and higher efficiency in calculating. So the research of the single-beam method has practical significance. Central angle is the key factor to determine whether the curved girder bridge can be analyzed with the single-beam method. According to A ramp bridge of Jingkai overpass, several models of curved girder bridges with different spans, deck widths and central angles are built and compared using the grillage method and the single-beam method in this paper. Then by taking 10% as the control index, the applicable condition of the single-beam method is obtained. © 2016, Engineering Mechanics Press. All right reserved.


He H.,Beijing University of Technology | He H.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Li R.,Beijing University of Technology | Chen K.,Beijing University of Technology
Shock and Vibration | Year: 2015

Jerk is the time rate of acceleration and mainly represents the nonstationary component in high frequency band of the earthquake wave. The study on jerk and its response spectra can enhance the recognition of the nonstationary ground motion. The mechanical meaning and research value of jerk are described. Jerk is recommended to be solved by establishing state-space equations and Runge-Kutta method. The solution method of elastic and inelastic jerk response spectra under ground motion is established, and the accurate jerk spectrum should be calculated directly according to numerical computing instead of pseudo-acceleration spectrum. The characteristics of jerk response spectra are studied according to the influencing factors, such as site condition, amplification factor, ductility factor, and reduction factor. The concept of impact reduction factor is presented. The statistical results show that the jerk spectrum has similar rules as the acceleration spectrum, and the amplitude is relative to the predominant period, especially for structures with short or medium period. If the ductility is improved, the effective jerk will reduce obviously, and the impact reduction factor will be enhanced. Different from the strength reduction factor, the impact reduction factor is nearly not relevant to the period. © 2015 Haoxiang He et al.


He H.,Beijing University of Technology | He H.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Li R.,Beijing University of Technology | Chen K.,Beijing University of Technology
Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and Engineering | Year: 2016

Chloride attack and carbonization are the two major factors affect the durability of reinforced concrete structures, and each theoretical model is systematically established. However, the quantitative analysis and models about the coupling effect of chloride attack and carbonization are incompetent, so the precision and level of durability analysis of reinforced concrete are restricted. Diffusion-limited Aggregation (DLA) model can intensively simulate the process of gaseous diffusion and condensation with randomness and fractal characteristics, which is suitable to reveal the durability evolution process of the chloride attack, carbonization and the coupling action in concrete. Based on the principle of DLA, considering the factors such as diffusion depth, concrete properties and exposure conditions which influence the characteristics of chloride diffusion and carbonization, as well as the coupling effect, an integrated DLA model is presented. The concentration of carbon dioxide and chloride at any time and any location can be obtained and be dynamically displayed based on the DLA model. The performance predict method for concrete and steel bars considering fatigue effect is presented based on DLA, according to the demand for bridge durability analysis. Numerical examples show that the method can dynamically and intensively simulate the durability evolution process of reinforced concrete bridges. © 2016, The Editorial Board of Journal of Basic Science and Engineering. All right reserved.


He H.,Beijing University of Technology | Chen K.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Li R.,Beijing University of Technology
Advances in Materials Science and Engineering | Year: 2015

Compared with the traditional steel rigid connection, the beam-column connections with weakened beam end have better ductility, but the local buckling in the weakened zone and the overall lateral deformation may occur in strong earthquake. The replaceable steel connection with low yield point metal is proposed based on the concept of earthquake resilient structure. In this connection, the weakened parts in the flange slab and web plate are filled with low yield point metal, and the metal firstly yields and dissipates energy sufficiently in earthquake; hence, the main parts are intact and the yield point metal can be replaced. The seismic performances of the three types of connections which include traditional connection, beam end weakened connection, and replaceable connection with low yield point steel under low cycle reciprocating load are studied. In addition, the energy dissipation capacity and damage characteristics of different connections are compared. The multiscale finite element models for the steel frames with different connections are analyzed by time-history method; both the computational efficiency and the accuracy are assured. The analysis results approve that the replaceable connection can confine the major damage in the replacement material and have better energy dissipation ability, safety reserves, and resilient ability. © 2015 Haoxiang He et al.


He H.,Beijing University of Technology | He H.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Wang X.,Beijing University of Technology | Zhang X.,Beijing University of Technology
Advances in Materials Science and Engineering | Year: 2016

In view of the disadvantages such as higher yield stress and inadequate adjustability, a combined low yield point steel plate damper involving low yield point steel plates and common steel plates is proposed. Three types of combined plate dampers with new hollow shapes are proposed, and the specific forms include interior hollow, boundary hollow, and ellipse hollow. The "maximum stiffness" and "full stress state" are used as the optimization objectives, and the topology optimization of different hollow forms by alternating optimization method is to obtain the optimal shape. Various combined steel plate dampers are calculated by finite element simulation, the results indicate that the initial stiffness of the boundary optimized damper and interior optimized damper is lager, the hysteresis curves are full, and there is no stress concentration. These two types of optimization models made in different materials rations are studied by numerical simulation, and the adjustability of yield stress of these combined dampers is verified. The nonlinear dynamic responses, seismic capacity, and damping effect of steel frame structures with different combined dampers are analyzed. The results show that the boundary optimized damper has better energy-dissipation capacity and is suitable for engineering application. © 2016 Haoxiang He et al.


Du X.,Beijing University of Technology | Du X.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Ma C.,Beijing University of Technology | Ma C.,Beijing Collaborative Innovation Center for Metropolitan Transportation | And 2 more authors.
Lixue Xuebao/Chinese Journal of Theoretical and Applied Mechanics | Year: 2014

The failure of material can be concluded to the shear fracture and each material has a specific shear sliding surface. The shear strength is the function of normal stress on sliding surface. A series of shear sliding surface is unified and nonlinear unified strength model of geo-materials is proposed. Sliding surface of nonlinear unified strength model is isoclinic surface in β stress space. The Strength surface of nonlinear unified strength model is circular conical surface in the β stress space and a series of conical surfaces are continuous smooth and convex in principal stress space. The nonlinear unified strength model can be illustrated as a curve between the Drucker-Prager and SMP in deviatoric plane, and as a straight line in meridian plane. There are only three mechanical parameters in the model which have definite physical meanings. Compared with large numbers of data under true triaxial tests, the applicability of nonlinear unified strength model is verified to different materials. And the proposed model can describe the nonlinear strength property of various materials reasonably.


Han E.-Z.,Beijing University of Technology | He H.-X.,Beijing University of Technology | He H.-X.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Lu Y.-W.,Beijing University of Technology
Zhendong Gongcheng Xuebao/Journal of Vibration Engineering | Year: 2016

The dynamic responses of the structure are different when the ground motions generate along different directions as excitations, and there exits a critical angle to attain the maximum response. The critical angle calculated based on traditional method is a horizontal angle because only the two-component ground motions in the plane are considered, and the adverse effect of the vertical ground motion is not concerned. The common mechanism between maximum principal stress direction in elastic mechanics analysis and the critical angle of structure in the plane is demonstrated. The expression of maximum principal stress direction in the space is derived and the formula of the structure critical angle for three-dimensional ground motions is proposed. The calculation method of the three-dimensional critical angle for inelastic structure in three-dimensional ground motions is presented based on nonlinear finite element analysis. The characteristics and regularity of the critical angle in three-dimensional ground motions is discussed based on numerical modeling. It is proved that the three-component seismic motion and the corresponding critical angle should be calculated for the structure has obvious vertical modal shapes, and the critical angle of the inelastic structure is transient and is related to the structural damage degree. © 2016, Nanjing University of Aeronautics an Astronautics. All right reserved.


Xu C.-S.,Beijing University of Technology | Xu C.-S.,Beijing Collaborative Innovation Center for Metropolitan Transportation | Liu H.-Q.,Beijing University of Technology | Du X.-L.,Beijing University of Technology | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

A test method is developed to simulate the deformation and strength characteristics of soils in real sites. This test method reveals the mechanism of seismic liquefaction of saturated sand under confined condition. A dynamic true triaxial test system is applied. This device provides mixed boundary conditions for samples and installation of advanced CATS test control system. The test results show that use of the dynamic true triaxial apparatus for sand liquefaction test research is feasible. Moreover, the mechanism of soil liquefaction under confined condition is investigated. Namely, the liquefaction will be generated when the axial and lateral pressures as well as the pore water pressure are equal to each other. It indicates that in the process of vibration load, the stress redistribution has a significant influence on the strength of sand liquefaction and the development mode of pore water pressure.

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