Evolutionary Spectral Analysis of Seismic Response of Infinitely Long Surface-Mounted Pipeline Considering Hydrodynamic Pressure of Viscous and Compressible Fluid in Pipe Han Do Kim
ABSTRACT It is no exaggeration to say that the existing studies on fluid-structure interaction are largely limited to the exterior problem. Furthermore, there are many cases where it is assumed that the objective fluid is ideal and so few it is compressible, especially viscous in the studies on interior problem that it is necessary the analysis in consideration of the effects of the compressibility and viscosity of fluid. This paper includes a seismic response analysis of infinitely long surface-mounted pipeline transporting the crude oil, by considering the dynamic characteristics of fluid in it. The hydrodynamic pressures were calculated by modeling the ideal fluid and inviscid compressible fluid with coupled boundary element-finite element method and the viscous incompressible fluid with finite element method, and they were applied to infinitely long surface-mounted pipeline. Finally, by carrying out evolutionary spectral analysis of seismic response, it was discussed the necessity of considering the viscosity and compressibility of fluid, by comparing and testing the values of moment obtained at a observed support in the wave number domain, frequency domain and time domain. It was observed that the responses when the fluid in pipe was modeled with inviscid compressible fluid were larger than with ideal fluid in the entire time history. When it was assumed that the pipe was rigid and the viscosity of fluid was considered, the high-frequency system was transferred to low-frequency one, for an excessive decrease of natural wave number and natural frequency. Besides, it was learned that the RMSV of moment and the response in the time domain were very small. It will be, therefore, a large possibility of resulting in destruction in the case of neglecting the compressibility of fluid in a practical seismic design, the uneconomical execution and danger of resonance when an earthquake happens, with ignoring the viscosity of it. To prevent such phenomena, it is insisted that it should be reflected in a seismic design, the result from determining appropriately whether the viscosity or compressibility of fluid is considered, by the judgement of engineer according to the circumstances of soil, pipeline and fluid in it.
Key Word evolutionary spectral analysis of seismic response, infinitely long surface-mounted pipeline, transfer matrix, wave-propagation technique, RMSV of moment, hydrodynamic pressure, sloshing, coupled boundary element-finite element method, finite element method, viscosity, compressibility, penalty formulation, relative motion formulation, wave number response function, frequency response function
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