Vibration Characteristics And Dynamic Response Analysis Of Urban Natural Gas Pipeline

Urban natural gas pipeline system is one of the municipal infrastructure systems to maintain the normal operation of the city and ensure the rapid development of urban economy.Running through every corner of modern city,it is referred to as the artery of modern industry and city.The pipeline is prone to vibration,instability and deformation due to external loads.In severe cases,secondary accidents such as leakage and explosion may occur,causing huge economic losses and casualties.In order to ensure the safe operation of the natural gas pipeline system,it is necessary to analyze its vibration characteristics and dynamic response.In this thesis,the urban natural gas pipeline is taken as the research object,and the coupled vibration characteristics of natural gas pipeline,the response spectrum analysis of the suspended pipeline under seismic loads and the dynamic response of buried pipeline under traffic loads are studied by theoretical analysis and numerical simulation method.The main research work and innovation of this thesis are as follows:(1)The vibration differential equation of natural gas straight pipe is established,and the theoretical expressions of natural frequency and natural mode are derived.On this basis,the Hamilton principle is used to establish the differential equation of the fluid structure coupling lateral vibration of the pipeline considering the influence of natural gas pressure,pipe diameter and wall thickness.Through the comparison between the theoretical calculation results and the the finite element simulation results,it is proved that the ANSYS Workbench finite element modeling method used in this thesis is feasible.(2)Based on ANSYS Workbench finite element platform,the suspended pipe model considering unidirectional fluid-structure coupling is established.Three kinds of pipeline constraint forms are established through the reasonable simplification of the pipeline constraint in several practical engineering,and the influence of different parameters of natural gas pressure,wall thickness,pipe diameter and constraints on pipeline modal is also analyzed.The results show that the influence of pressure on the pipeline can not be ignored under the condition of secondary high pressure and high pressure,the influence of pipe diameter change on the system modal is obviously greater than that of the wall thickness,and the constraint conditions have a significant impact on the system modal.(3)ANSYS Workbench is used to analyze the seismic response spectrum of suspended pipeline,the stress and deformation of natural gas pipeline under different parameter are obtained.The research results show that under the condition of secondary high pressure and high pressure,the effect of flow field pressure will have a greater impact on the peak displacement and stress of pipeline under seismic load,and the effect of seismic load on lateral vibration of pipeline is greater than that of axial vibration.Increasing the pipe diameter and pipe restraint force is beneficial to improve the seismic performance of the pipeline system.(4)In order to truly simulate the influence of traffic load on the mechanical properties of buried pipeline,the three-dimensional modeling of multi-layer road structure is carried out in this thesis.The steady state harmonic load is used to simulate the traffic load,and the Drucker-Prager constitutive model is used to simulate the elastic-plastic state of the soil.the influence law of different wheel pressure,speed and pavement aging degree on the mechanical characteristics of buried pipeline is obtained.The results show that the actual force of pipeline is larger than that of traffic load due to the interaction of soil gravity and traffic load,and the vertical deformation and stress of buried pipeline increase significantly with the increase of wheel pressure.The influence of vehicle speed and pavement aging on the equivalent stress of the buried pipeline is greater than that of vertical displacement.The research methods and results of this thesis can provide some reference for the structure optimization and design of urban natural gas pipeline system.