In order to investigate the influence of degradation on dynamic behavior and the failure mode of piping systems with local wall thinning, shake table tests using 3-D piping system models were conducted. The degradation considered in this study was wall thinning, which would be caused in piping systems due to the effects of aging. The degradation condition induced in the piping system model was 50 % full circumferential wall thinning at an elbow. The test model was designed to cause out-of-plane bending moment to the thinned-wall elbow by excitation tests. The model without wall thinning was also used in the excitation test to compare the behavior of the piping system models. These models were excited under same input acceleration until fatigue cracks penetrated or an excessive deformation occurred to the models. Through these tests, the vibration characteristic and the process to failure of degraded piping models were obtained for the out-of-plane bending model. This paper describes the dynamic response and failure behavior of piping systems with wall thinning based on the test results. The failure mode of the piping model with thinned wall elbows under out-of-plane bending was a low-cycle fatigue failure accompanied with a remarkable ratchet deformation, and the life of the model with thinned wall elbow reduced less than 1/5 of the model without wall thinning. A fatal excessive deformation was not observed in these tests, but it can be said that the wall thinning at elbow subjected to out-of-plane bending should be paid enough attention to consider the failure of the piping system under excessive seismic load.
Effect of local wall thinning on the dynamic behavior of piping systems
2005
7 Seiten, 11 Bilder, 2 Tabellen, 11 Quellen
Aufsatz (Konferenz)
Englisch
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