Seismic Proving Test of Ultimate Piping Strength: Ultimate Strength Test

The proving test of a large-scale piping system with a piping bore of 200A (8B) and made from carbon steel material was conducted to assure the safety margin of the current and new design codes for piping. Two test models were used, one for the design method confirmation test and one for the ultimate strength test. The design method confirmation test model reflected the structural features and vibration characteristics of piping systems. For the ultimate strength test, the piping system was modified by adding one more mass and removing one horizontal support. The original seismic wave to the input seismic wave was selected to be the “S₂” seismic wave for a PWR building. The time-pitch and the excitation level were then modified to meet the test conditions. For the ultimate strength test, a series of tests was initiated at a pseudo-elastic design stress level of about 9 times the current allowable primary stress limit (3Sm) for the “S₂” seismic wave, and repeated until the occurrence of piping failure due to through-wall fatigue cracking was obtained during Run 5 of seismic shaking. Pre-test and post-test analyses were performed. The post-test analysis results, which assessed certain differences of actual input acceleration, damping ratio, mass distribution and fatigue damage, compare well with the ultimate strength test results of elasto-plastic global response, local strain and the number of runs to piping failure.