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The objective of this paper is to evaluate the aerodynamic effect of the high-speed train on an overpass cable-stayed bridge completed by the rotation method. Computational fluid dynamics software Fluent was used in this numerical study. Flow field under a high-speed train has been considered as a viscous, compressible and unsteady flow. Flow model of high-speed train and bridge was established by the sliding mesh approach. Simulated train is passing 7.25 m underneath the bridge with a speed of 350 km/h and 500 km/h to obtain the time history of lifting force, resistance force and torque such that those data can be later applied to the bridge under different construction stages. Numerical results showed that larger aerodynamic response was observed when the tail of the train passed the bridge and the maximum response was observed right above the train. As for current scenario, the aerodynamic effect on such type of concrete cable-stayed bridge could be ignored but it should be checked when structure became lighter (such as steel structure). [ABSTRACT FROM AUTHOR]

A three-dimensional model of the fixed plate of steel ball grinding machines is established using finite element methods. Its distortion and stress status are analyzed, and the natural frequencies and vibration features are obtained. By using the circular area of elastic contacts, the number of effective cutting edges is determined, and a mathematical model is established between the grinding pressure and depth. Then the structural optimization design is programmed with the APDL language of ANSYS. Under its strength being considered, the accurate and reliable design parameters of structures are obtained. Simulation results show that the machining accuracy of steel balls is improved. [ABSTRACT FROM AUTHOR]

Rigid Frame Bridge was widely used while the according seismic design was quite difficult and worth of discussion. Section sizes of piers were increased when elasticity seismic theory was adopted; plastic hinges were designed on the top or bottom of piers when ductility seismic theory was employed; and isolation bearings were installed when seismic isolation theory was applied. However, larger size may neither be cost-effective nor meet the requirements of seismic design. Furthermore, seismic rehabilitation would be extremely difficult when plastic hinges were employed, and isolation bearings were not applicable to Rigid Frame Bridge as there was nowhere to place them. A new method was proposed for Rigid Frame Bridge referred as base-isolation design. Based on introducing base-isolation concept, base-isolation design of Rigid Frame Bridge was achieved by setting seismic-isolation layer in cap. There were four kinds of base-isolation systems widely adopted in numerical investigation of base-isolation for Rigid Frame Bridge, i.e., laminated elastomeric bearings (EB) system, lead rubber bearings (LRB) system, EB and liquid viscous dampers (EB-LVD) system, and LRB-LVD system. It was found that: i) seismic effect transmitted to superstructure and substructure of bridge could be dramatically reduced by seismic-isolation layer; ii) efficiency of base-isolation system could be significantly promoted by using EB and LVD together; iii) mechanical parameters of isolation devices should be determined according to the actual situation of the bridge. [ABSTRACT FROM AUTHOR]

The random friction distribution is an objective phenomenon and always leads to great uncertainty in seismic responses of damper-friction isolation systems. As to optimize the seismic performance, this paper artificially made the friction distribution on a contact surface to be concave. When the damper-friction isolation system was subjected to different ground motions, more regular responses, due to the concave friction distribution, were obtained comparing with the responses of the random friction distribution. The concave friction distribution is always conducive to reducing the structural relative displacement and insignificantly increasing the structural acceleration. An optimization design example of an isolation building was carried out. And the results showed that as for a structure only being sensitive to acceleration or force, significant concave friction distribution and little damping constant would be the best design combination. It resulted in a much less acceleration and an acceptable relative displacement on the structure. [ABSTRACT FROM AUTHOR]

The objective of this paper is to study the reasonable stiffness of rubber mat layer of vibration reduction slab track and configuration of rubber mat layer of transition section slab tack between vibration reduction section and normal section in high-speed tunnel. Based on achievements of the related studies, a high-speed train, slab track and tunnel finite element coupling dynamic model was established, and corresponding program was developed with MATLAB and verified by in situ measured data. The dynamic responses of slab track under moving high-speed train with different vibration reduction configurations and transition arrangements in Shiziyang tunnel of Guangzhou-Hong Kong high-speed railway line in China were analyzed. The study shows that: the rubber mat layer under the slab of slab track can greatly reduce the tunnel vibration, but the slab bending moment and the rail vertical displacement will increase, so the stiffness of rubber mat layer under the slab of slab track in tunnel of high-speed railway line should not be too low; the stiffness of rubber mat layer of slab track in tunnel of Guangzhou-Hong Kong line is controlled by the rail vertical displacement, and the stiffness value of 0.04 N/mm³ is reasonable; the vibration and dynamic stress of slab track can be improved greatly by setting transition section between vibration reduction slab track and ordinary slab track, and the design of transition section slab track in tunnel of Guangzhou-Hong Kong line is reasonable. [ABSTRACT FROM AUTHOR]