Waterhammer is the phenomenon which occurs due to rapid valve operation or sudden stop of pumps. When the waterhammer occurs, unbalanced pressure between elbows causes transient load on piping system. In the piping design against the waterhammer, it is necessary to evaluate the strength and the displacement of piping system against the transient load, and required to provide adequate piping supports. In the piping design, dynamic analysis and static analysis with DLF (Dynamic Load Factor) are often conducted to consider dynamic effect of the water hammer load. The piping support often regarded as rigid in the piping system analysis, however, because of support characteristic (flexibility, plastic behavior, sliding friction), the dynamic response of piping system changes from analysis result with rigid support. For this reason, support characteristics shall be considered adequately. Nevertheless, effect of the support characteristics on the piping design has not been discussed sufficiently.

In this paper, to clarify the effect of the support characteristics against the waterhammer load, a series of the nonlinear dynamic analyses were conducted. Based on the analysis results, the response spectra and the ductility charts considering the nonlinearities of the piping system were created. the design approach to properly control the displacement of piping system based on the nonlinear response spectra and ductility charts, is proposed, and the dynamic response against waterhammer load in the piping system of LNG loading line is discussed.

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