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With regard to piping systems of industrial facilities, sometimes they are subject to large deformation with high local plasticity. This results mainly from the detrimental ground movement due to possible liquefaction near seaside when a strong earthquake occurs. Especially the high local plasticity concentrates on elbows (bends) in piping systems. In this paper, the elbow behaviors of in-plane (closing: deflection to decrease elbow radius of curvature and opening: deflection to increase its radius of curvature) and out-of-plane bending are analyzed in a large plastic range using Nonlinear Finite Element Method (FEM) with the shell elements of material and geometrical nonlinear characteristics. The flexibility factor of elbows depends on flexibility characteristics, angular distortion and yield stress of material. Thus, in order to estimate the behaviors of piping systems with large plasticity at elbow by a simplified method, the modified flexibility factor method is introduced from results of FEM. Calculation results obtained using the simplified method are compared with experimental results, and this method gives an index to assess behaviors of piping systems subject to extremely large movement of supports. It is also possible to estimate local plasticity at elbows in piping systems by this conventional analysis.Copyright © 2002 by ASME

A design method of piping components for Level 2 earthquake (the possible strongest earthquake with extremely low probability of occurrence) such as bolted flanged joints, expansion joints, and equipment nozzles is described. This design method is provided taking into account their failure modes and degree of safety. The failure modes for each piping component is classified according to the past damage experience due to earthquake, and each criterion is provided against the failure mode. The typical failure modes are gas leakage, fatigue failure, cumulative plastic deformation during and after earthquake for bolted flanged joints, expansion joints and equipment nozzles in piping components, respectively. Specifically, the simplified method of bolted flanged joints is proposed as the convenient design method for chemical plants and petroleum refineries, etc. (here in after calls as plant) The method is derived using gasket factor, gasket dimensions and clamping forces due to bolts for external piping load. This practical method is investigated and verified due to the experimental results on the welding neck type flanges subjected to static bending moment, in which the bolted flanged joints of NPS 4″ and 8″ in size, 3 types of gaskets are used. In addition, the dynamic inertia force effect is also studied by the shaking table tests using cantilever model of bolted flanged joints at fixed side with changing the bolt clamping forces and gasket types.Copyright © 2002 by ASME

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.Copyright © 2002 by ASME

The Seismic Design Code for High Pressure Gas Facilities was established in advance of other industrial fields in 1982. Only exception was that for nuclear power plants. In 1995, Hyogoken Nanbu earthquake brought approximately 6,000 deaths and more than 100,000 M$ loss or property in Kobe area, Japan. This unexpected serious event enforced us that industrial facilities should pay to special considerations of their damages including ground failure due to the liquefaction. Their strong ground motions brought serious damages to urban structures in the area. Thus, the Seismic Design Code of the High Pressure Gas Facilities were improved to include 2 step design assessments, that is, Level 1 earthquake (operating basisearthquake, the probable strong earthquake in the service life of the facilities), and Level 2 earthquake (safety shutdownearthquake, the possible strongest earthquake with extremely low probability of occurrence). For Level 2 earthquake, the ground failure by possible liquefaction shall be taken into account. In regard to Level 1 earthquake, the system must be remained safety without critical damage after the earthquake, in addition to no leakage of “gas”. In regard to Level 2 earthquake, the required seismic performance is that peventing systems must be remained without gas leakage, and stable. It means a certain non-elastic deformation without gas leakage may be allowed. The High Pressure Gas Safety Institute of Japan has set up the Seismic Safety Promotion Committee to modify their code in advance of other industries, and continue to investigate more reasonable seismic design practice for more than 5 years. Andthe final version of the guideline has been established for the design practices both in Level 1 and Level 2 earthquakes. This paper explains the activities of the committee, their new design concepts and scope of applications.Copyright © 2002 by ASME