This paper deals with the recent trend of anti-earthquake design of Japanese latgescale industrial plants such as a petro- chemical plant, an oil refinery, a power generation plant and a nuclear power plant. Their new key issues are also discussed.
These problems came from the results of Hyogoken Nanbu eathquake-1995, so called Kobe eathquake as well as Northridge eathquake-1994, and the policy of deregulation of the Governmenu control on industrial activity and safety.
Kobe eathquake brought approximately 6000 deaths and US $10 Billion loses in Kobe area, one of three major port cities in Japan. And we got many new engineering findings as well as their social effects. Since the event, Japanese Government issues new policy for disaster prevention and mitigation, and also researches in those fields. The fundamental policy is two step design, Level 1 for a rather frequent event, which is expected every 50 years or more at the particular site, and Level 2 for a rare event, which is expected every 100-1000 years at the particular site. At Level 1 event, all social funcitons must remain as normal or minor repair required. At Level 2, loss of human lives and public property must be avoid. According to this requirement with de- regulation policy, most of the governmental regulation and guideline for seismic design of various kinds of structures, approximately 40 subjects, had to be revised last five years.
During Northridge-earthquake and this Kobe event, some significant phenomena for seismic design were observed. One of them was brittle failure of heavy steel structures. The detailed mechanism has not been clarified completely, however, the peak velocity of ground motions, which is near to 100cm/sec, may be a key parameter to this mechanism. Also, phenomena developed by liquefaction of soil in industrial area near to sea side and ports caused major part of loss of industrial properties in Kobe.
The Natinal Institute for Earth Science and Disaster Prevention started the project of 1, 200 ton 3-D shaking table, which is expected to be completed in 2005, the 10 year aniversary of Kobe event. We expect many unknown phenomena will be clarified to high peak ground velocity up to 200cm/sec by this new facility.

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Shear-bending buckling of the cylindrical part of Fast Breeder Reactor (FBR) main vessels under horizontal earthquake loading is one of the major problems in structural design. Therfore, the evaluation method of buckling strength is developed based on buckling tests and numerical calculations. The purpose of this paper is to describe the results of static and dynamic buckling tests of cylindrical shells and presented methods for buckling strength evaluation and seismic safety assessment.
Shear buckling strength and bending buckling strength are evaluated under the assumption that both buckling modes interact slightly with each other. Then seismic safety assessment is performed, where effect of response reduction under dynamic loads is taken into account.

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Seismic design of piping systems is usually based on elastic vibration theory. However, increase in design earthquake intensity makes it necessary to permit plastic deformation of piping element. Although it is possible to calculate elasto-plastic vibration response of piping systems using the direct integral method, the approach is not suitable for design applications.
Static load test and vibration test of a simplified piping model were carried out in order to study the elasto-plastic behavior. The equivalent damping ratio during elasto-plastic vibration is calculated using equivalent plastic strain and the volume in which plastic deformation occurs.
Both nonlinear modal analysis and linear analysis using equivalent damping ratio were applied to two piping models and the analytical results were compared with those of the tests. The results of the two anaytical methods coincided witht those of the tests in the case of small plastic deformation.

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This paper describes a magnetic dynamic damper (MDD), which is a passive vibration absorber employing a permanent magnet and a conductor for both the restoring and damping force. The basic characteristics of this magnetic spring and damper system are examined through static loading tests and vibration tests using a pair of double cylindrical magnets. It is confirmed that the magnetic force analysis accurately simulates these tests results. Moreover, application of this system to a rotating machinery model shows that the MDD can effectively reduce two-dimentional vibration.
The top heavy valve equipped on piping vibrates biaxially at different frequencies. In this case, the presented MDD consists of two groups of multiple small rectangular magnets facing each other across a gap and a conductor installed in the gap, and can be tuned to different frequencies in two different directions simultaneously.
Comparison of calculation and vibration test indicates that the magnetic force analysis is good enough to estimate the restoring and damping characteristics of this MDD. Vibration tests using a valve-piping model are also carried out to examine the two-dimensional vibration reduction capability by the proposed MDD. These vibration reduction effects can be simulatde by the simplified analytical model.

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A major earthquake that occurred in Japan was used as an experiment to verify the adequacy of seismic design. We studied our current seismic design margins based on the elastic theory and using data observed in Hyogoken Nanbu Earthquake.
While a study of this sort should be treated statistically, the fact that there was only one set of data led us to employ quantitative analysis. In some cases, we found a margin of 1.4 to 4.8 times between the actual seismic behavior and the design basis (e. g., carbon steel pipe STK400). The reduction effect of the input ratio of waves depends largely on the foundation structures. In the case of liquid storage tanks, the liquid level during an earthquake is an important margin factor. The strength margin depends largely on the margins of stress evaluation and material strength.
The margin should not be used to cover the uncertainty of the designer or operator. The margin should be used to cope with the uncertainty of earthquake as a natural phenomenon. Anti-fracture design should be taken to the important structures like tanks.

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The Hansin Great Earthquake of January 17, 1995, was the most damaging seismic event in Japan since the Kantou Great Earthquake of 1923. At the event, an earthquake observation system measured the motions of LNG Aboveground Storage in Osaka Gas Senboku Terminal II. Probably, the observation of such large motions of LNG Aboveground Storage is the first case in the world, so far.
LNG Aboveground Storage responses through foundation and ground at earthquake.
It is very difficult to try an experiment of total system which is composed of storage, foundation and ground, except for an observation of motions at earthquake. Because there is a limit to scale up the ability of shaking equipment. The probability that a storage will encounter a large earthquake in the life is very small. SO, actually it is necessary to observe for a long time. The Hansin Great Earthquake is the first large motions from August 1983 when the system started to observe the motions.
Then, we verified the seismic design of LNG Aboveground Storage using the records of measured large motions and proved the adequacy of present seismic design (elastic method).

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The plastic collapse and LBB behavior of statically indeterminate piping system were investigated in this study, compared with statically determinate piping system. Special attention was paid to evaluate the crack opening displacement after a crack penetrated wall thickness. The main results obtained were as follows: (1) The reduction of ultimate strength caused by a crack was relatively small in the statically indeterminate piping system. The main reason is considered that a sufficient redistribution of the bending moment occurs in this system. From this study, it was also known that the statically indeterminate piping system has more safety margin for LBB behavior than the statically determinate piping system. (2) A method to evaluate the crack opening displacement after crack penetration in pipe with a nonpenetrating crack was proposed. From this method, it was known that the crack opening displacement could be evaluated by using the plastic rotation angle. (3) The acceptable defect size considering the deformation of a pipe was estimated by comparing the plastic moment at the defective part and the gross yielding moment at the nondefective section.

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