Hydraulic Effects on a Large Piping System During Strong Earthquakes

Abstract

Liquid in a large piping system could become a resonance column under axial excitations. A 1000-m long closed-boundaries pipeline with pressure wave propagation velocity of 1000 m/s would have the fundamental liquid resonance frequency of 0.5 Hz. Then, some hydraulic transients might occur during strong earthquakes. If dynamic pressure amplitude exceeds the value of system stationary pressure, then vaporizing at negative pressure, and after that, cavity or liquid column separation and reconnection can be produced. One of the effects of these behaviors would be equivalent damping of dynamic response, and the other an impact force on pipe structural system. The latter effect is considered as one of potential damage factors of a large liquid piping system. In this paper, an analytical method of earthquake-induced hydraulic transients of piping system is applied to a real underground large piping system subjected to a strong earthquake motion which has occurred in Japan. The results of the analysis have shown that the occurrence of earthquake-induced negative pressure in liquid column is possible. Further, the analysis has explained the difference between two long straight pipelines buried in the same route, one failed by axial cracking and the other had no damages.

Frequency Domain Analysis for Detecting Pipeline Leaks

“…The problem with this approach is the long time required to sweep through each frequency, as each frequency requires that the system settle down to steady oscillatory conditions. In addition, the excitation of a pipeline at the resonance frequencies can also inflict substantial damage to the system (Ogawa et al, 1994).…”

Fluid transients and fluid-structure interaction in flexible liquid-filled piping

“…Ogawa et al [73] applied an analytical model of earthquake-induced fluid transients to an inplace underground piping network. Using an artificially modified earthquake for excitation 33 combined with frequency-domain analysis, they concluded that induced sub-atmospheric pressures in the liquid were possible, and demonstrated how two parallel pipes in the same network could have one fail axially while the other experienced no damage, because of the different waterhammer response in each pipe.…”

Transient Modeling of Arbitrary Pipe Networks by a Laplace-Domain Admittance Matrix

“…In Ogawa [1980]; Ogawa et al [1994], system matrix transfer functions for pressure and velocity sinusoidal amplitude distributions were derived for arbitrary networks. In this work, spatial earthquake vibrations were the transient state driver for the system, and as such, the fluid line equations incorporated axial displacement terms.…”

“…In this work, spatial earthquake vibrations were the transient state driver for the system, and as such, the fluid line equations incorporated axial displacement terms. Ogawa [1980]; Ogawa et al [1994] reduce their model to a set of two unknowns for each pipe (one coefficient for each pipe's positive and negative traveling waves).…”