A New Seismic Design Criteria of Piping Systems in High Pressure Gas Facilities

After the Great Hyogoken-nanbu Earthquake, “Seismic Design Code for High Pressure Gas Facilities of Japan” was amended. This amended code requires two step seismic assessments, that is, evaluation of Level 1 Required Seismic Performance for Level 1 Earthquake and that of Level 2 Required Seismic Performance for Level 2 Earthquake. Seismic design of piping systems is newly involved in the scope of the code. For Level 2 Earthquake, possible ground displacement due to liquefaction is taken into account. When ground displacement occurs, foundations of structures settle, laterally move or incline as a conseqence, and a piping system supported by independent foundation structures suffers from relative displacements between supporting points, which may exceed several tens of centimeters. The evaluation method of Level 1 Required Seismic Performance is specified in the amended code and that of Level 2 Required Seismic Performance is proposed in the guideline. The former evaluation is based on elastic design and the latter on elasto-plastic design. The propriety of design criteria of piping systems against ground displacement was confirmed by large deformation tests. This paper introduces seismic design criteria of piping systems in the amended code and the evaluation method of Level 2 Required Seismic Performance proposed in the guideline, and also reports the results on the large deformation tests.