Failure Behavior of Piping Systems With Wall Thinning Under Seismic Loading

Abstract

Shaking table tests of three-dimensional piping models with degradation were conducted in order to investigate the influence of degradation on dynamic behavior and failure modes of piping systems. The degradation condition induced in the piping models was about 50 percent full circumferential wall thinning at elbows. Four types of models were made for the shaking table tests by varying the location of wall thinning in the piping models. These models were excited under the same input acceleration until the models failed and a leak of pressurized internal water occurred. Through these tests, the change of the vibration characteristics and processes to failure of degraded piping models were obtained. The deformation of the piping models tended to concentrate on the degraded elbows, and the damage was concentrated on the weakest elbow in the piping models. The failure mode of the piping models was a low-cycle fatigue failure at the weakest elbow.

Effect of wall thinning on deformation and failure of copper‐nickel alloy elbows subjected to low cycle fatigue

“…Various industrial standards, such as ASME and the Japanese JEAC, specify the minimum number of cycles, which pressure equipment must tolerate during a single seismic event. [4][5][6][7] However, bends and elbows over time are subjected to the flow accelerated corrosion leading to the localised wall thinning. [8][9][10] Therefore, it is important to understand the effect of these structural defects on the strength in order to maintain the safety and integrity of hazardous structures.…”

“…Therefore, their performance and behaviour during seismic events are critical from the structural integrity point of view. Various industrial standards, such as ASME and the Japanese JEAC, specify the minimum number of cycles, which pressure equipment must tolerate during a single seismic event . However, bends and elbows over time are subjected to the flow accelerated corrosion leading to the localised wall thinning .…”

Investigation of the Seismic Safety Capacity of Aged Piping System: Shake Table Test on Piping Systems With Wall Thinning by E-Defense

“…Though there are a lot of excitation tests and numerical analyses on piping system models without degradation or pipe elements with degradation [1][2][3][4][5][6][7][8][9], the studies on degraded piping systems are not numerous, and the data to discuss the safety capacity of degraded piping systems are still insufficient. The authors have conducted a series of experiments and analyses to investigate the ultimate strength and the failure modes of pipe elements and piping systems with or without degradation, and established the analytical model to estimate the fatigue life of piping systems [10][11][12][13]. Through these experiments and analyses, it is understood that the failure mode of the piping systems with wall thinning under seismic loads is mainly the fatigue failure accompanied by the ratchet deformation.…”