Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its de...Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.展开更多
To study the dynamic behavior of pipeline systems installed with large-mass valves within nuclear power plants during earthquakes,seismic simulation tests are carried out on a pipeline system equipped with a DN80 gate...To study the dynamic behavior of pipeline systems installed with large-mass valves within nuclear power plants during earthquakes,seismic simulation tests are carried out on a pipeline system equipped with a DN80 gate valve,and the FEM updating technique is used to identify the stiffness distribution of the valve.By conducting tests and a numerical analysis,the following conclusions are obtained:After a large-mass valve is installed in the pipeline,the system shows higher sensitivity to intermediate and high frequency components in the earthquake than low frequency components.It is possible for the intermediate frequency components to be amplified by the valve in the horizontal direction,while the pipes tend to amplify the high frequency components in horizontal and vertical directions.Changes in the high-order modes of the system depend on valve stiffness distribution.Since the existence of a valve makes pipeline system damping distribute with an obvious non-proportional feature,when the response spectrum method is used to calculate the response of the pipeline system,it could result in an underestimation of low-damping positions and overestimation of high-damping positions.展开更多
文摘Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.
文摘To study the dynamic behavior of pipeline systems installed with large-mass valves within nuclear power plants during earthquakes,seismic simulation tests are carried out on a pipeline system equipped with a DN80 gate valve,and the FEM updating technique is used to identify the stiffness distribution of the valve.By conducting tests and a numerical analysis,the following conclusions are obtained:After a large-mass valve is installed in the pipeline,the system shows higher sensitivity to intermediate and high frequency components in the earthquake than low frequency components.It is possible for the intermediate frequency components to be amplified by the valve in the horizontal direction,while the pipes tend to amplify the high frequency components in horizontal and vertical directions.Changes in the high-order modes of the system depend on valve stiffness distribution.Since the existence of a valve makes pipeline system damping distribute with an obvious non-proportional feature,when the response spectrum method is used to calculate the response of the pipeline system,it could result in an underestimation of low-damping positions and overestimation of high-damping positions.
