It is resumed that 14 gas holders in Hansin districtwere shaked more than 300 gal acceleration at ground level by theHyogo-ken Nanbu Earthquake. These holders had no damages, sothe excellent earthquake resistance of helders were proved.The reasons why no damages are according to the designtolerance and others as belows. ① Holders have seismiccountermeasures as swan neck.② Holders have steel structurenear axial aymmetry and fine characteristic of stability, so haveexcellent earthquake resistance.③ Foundation structures haveenough earthquake resistance because annular, radial andcylindrical beams are adopted as parts of foundation. Andfoundation and supporting structures are connected firmly, soactual damping value is less than one used at design atage. ④Actual value of parts are thicker and stronger than ones used atdesign stage. ⑤ All foundation of the holder aren't shakenuniformly because the phase of earthquake wave is slipped at eachpoints of large foundation. ⑥ If the ground is liquefied, inputratio of wave from ground to foundation is reduced.When we consider that the holders in Hansin district had beendesigned, manufactured and maintained by Recommended Practicefor Spherical Gas Holder by Japan Gas Association (JGA), weconfirm gas holders by this guideline have excellent earthquake resistance.
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