It is resumed that 14 gas holders in Hansin district were shaked more than 300 gal acceleration at ground level by the Hyogo-ken Nanbu Earthquake. These holders had no damages, so the excellent earthquake resistance of holders were proved.The reasons why no damages are according to the design tolerance and others as below. ①Holders have seismic countermeasures as swan neck. ②Holders have steel structure near axial asymmetry and fine characteristic of stability, so have excellentearthquake resistance. ③Foundation structures have enough earthquake resistance because annular, radial and cylindrical beams are adopted as parts of foundation. And foundation and supporting structures are connected firmly, so actual damping value isless than one used at design stage. ④Actual value of parts are thicker and stronger than ones used at design stage. ⑤All foundation of the holder aren't shaken uniformly because the phase of earthquake wave is slipped at each points of large foundation. ⑥If the ground is liquefied, input ratio of wave from ground to foundation is reduced.When we consider that the holders in Hansin district had been designed, manufactured and maintained by Recommended Practice for Spherical Gas Holder by Japan Gas Association(JGA), we confirm gas holders by this guideline have excellent earthquakeresistance.
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