In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their lo...In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their load carrying capacity and stability, a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible air flow governing equations. The realizable κ-ε model was used as a turbulent closure illustrate that the interaction exists between shock waves The supersonic flow field near air inlets was analyzed. The flow structures and boundary layer, and the flow separation is formed at the lower comer and the lower wall around the point of a maximum velocity. The numerical results show that the conversion from supersonic flow to subsonic flow in spherical air bearing occurs through a shock region （pseudo-shock）, and the viscous boundary layer results in the flow separation and reverse flow near the shock. The calculation results basically agree with the corresponding experimental data.展开更多
The objective of this investigation was to study the behavior of deep pile caps and the ultimate load-carrying capacity. Four 1/10 scaled models of nine-pile caps were cast and tested on vertical loads to failure. The...The objective of this investigation was to study the behavior of deep pile caps and the ultimate load-carrying capacity. Four 1/10 scaled models of nine-pile caps were cast and tested on vertical loads to failure. The destruction shapes of pile caps,the correlation between load and displacement,and the internal stresses were analyzed systematically. The results demonstrated that the failures of all the four models are resulted from punching shear; the internal flow of the forces in nine-pile caps can be approximated by "strut-and-tie" model. Furthermore,the failure loads of these specimens were predicted by some of the present design methods and the calculated results were compared with the experimental loads. The comparative results also indicated that the "strut-and-tie" model is a more reasonable design method for deep pile caps design.展开更多
The peculiarities of calculating isolated structures with spherical bearings are analyzed in this paper. Some of peculiarities are caused by the lack of data at the moment when engineering solutions had to be made, Ot...The peculiarities of calculating isolated structures with spherical bearings are analyzed in this paper. Some of peculiarities are caused by the lack of data at the moment when engineering solutions had to be made, Other peculiarities are connected with physical peculiarities of the device behaviour. To provide the analysis of structure hehaviour under the condition of the lack of input information, two types of design models of seismic protection devices were considered. They are the dampers linearization and the modelling of real dampers by dry friction ones. The dampers linearization makes it possible to use the existing software for calculating linear strongly-damped systems. To calculate structures with dry friction dampers, a new software was worked out. In this case, the structure is described as a piecewise-linear system of a relay-type. The investigations of the structure oscillations take into account both horizontal and vertical components of earthquake input. Under this condition, horizontal oscillation equations of structures are the MaRie-Hill ones. The input and structure parameters which caused the structure instability are estimated. To exclude the structure instability, high damping devices should be used. These methods were used for seismic resistant analysis of bridges with spherical bearings and hydraulic dampers applied in Sochi.展开更多
基金Project(2002AA742049) supported by the National High Technology Research and Development Program of China
文摘In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure, which could decrease their load carrying capacity and stability, a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible air flow governing equations. The realizable κ-ε model was used as a turbulent closure illustrate that the interaction exists between shock waves The supersonic flow field near air inlets was analyzed. The flow structures and boundary layer, and the flow separation is formed at the lower comer and the lower wall around the point of a maximum velocity. The numerical results show that the conversion from supersonic flow to subsonic flow in spherical air bearing occurs through a shock region （pseudo-shock）, and the viscous boundary layer results in the flow separation and reverse flow near the shock. The calculation results basically agree with the corresponding experimental data.
基金National Key Project of Scientific and Technical Supporting Programs funded by Ministry of Science &Technology of China (No. 2006BAG04B00)
文摘The objective of this investigation was to study the behavior of deep pile caps and the ultimate load-carrying capacity. Four 1/10 scaled models of nine-pile caps were cast and tested on vertical loads to failure. The destruction shapes of pile caps,the correlation between load and displacement,and the internal stresses were analyzed systematically. The results demonstrated that the failures of all the four models are resulted from punching shear; the internal flow of the forces in nine-pile caps can be approximated by "strut-and-tie" model. Furthermore,the failure loads of these specimens were predicted by some of the present design methods and the calculated results were compared with the experimental loads. The comparative results also indicated that the "strut-and-tie" model is a more reasonable design method for deep pile caps design.
文摘The peculiarities of calculating isolated structures with spherical bearings are analyzed in this paper. Some of peculiarities are caused by the lack of data at the moment when engineering solutions had to be made, Other peculiarities are connected with physical peculiarities of the device behaviour. To provide the analysis of structure hehaviour under the condition of the lack of input information, two types of design models of seismic protection devices were considered. They are the dampers linearization and the modelling of real dampers by dry friction ones. The dampers linearization makes it possible to use the existing software for calculating linear strongly-damped systems. To calculate structures with dry friction dampers, a new software was worked out. In this case, the structure is described as a piecewise-linear system of a relay-type. The investigations of the structure oscillations take into account both horizontal and vertical components of earthquake input. Under this condition, horizontal oscillation equations of structures are the MaRie-Hill ones. The input and structure parameters which caused the structure instability are estimated. To exclude the structure instability, high damping devices should be used. These methods were used for seismic resistant analysis of bridges with spherical bearings and hydraulic dampers applied in Sochi.
