In order to investigate the influence of degradation on dynamic behavior and failure modes of piping systems, shaking table tests of 3-D piping models with degradation were conducted. The degradation condition induced in the piping models was about 50% full circumferential wall thinning at an elbow or elbows. By varying the induced parts in the piping model, 4 kinds of models were made for the shaking table tests. These models were excited under the same input acceleration until the models failed and caused leak of pressurized internal water. Through these tests, the change of the vibration characteristic and the process to failure of degraded piping models were obtained. The deformation of the piping models tended to concentrate on the degraded elbows, and therefore the damage concentrated to a weakest elbow in the piping models. The failure mode of the piping models was a low-cycle fatigue failure at the weakest elbow.
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