2005年宮城県沖の地震で天井落下被害の起きた建物の数値解析による基礎的考察

摘要

2005年の宮城県沖地震で天井落下被害の起きた公共屋内プールを例として数値解析を行い、樹こ吊長が変化して吊られている天井板の面内回転運動の影響を確認した。吊材の配置からx方向加振時の回転応答が顕著であり、回転運動が発生した場合、天井板の重心付近に比べ外周部の変位・加速度は非常に大きくなる。本建物においてはその影響が顕著に現れ、天井の損傷も、端部から対称性をもって発生しやすくなっていたことが推察される。%During the Miyagiken-oki earthquake occurred at Sendai region on 16 Aug.,2005 the suspended ceiling of a public indoor swimming pool was heavily damaged and many people were injured by the failed ceilings. About ninety percent of the suspended ceiling covering the swimming pool space was failed and fallen during the earthquake. Failure of ceilings in large roof buildings during earthquakes is repetitively reported but no reasonable explanation of such failure has been established, so far. In this article, the results of the numerical simulation of the suspended ceiling of the swimming pool mentioned above is reported. The focus was put on the general behavior of the suspended ceilings, especially in-plane rotation of the entire ceiling panel, since the ceiling was hang by the hunger bolts with different length. The results show the large displacements at the both sides of the ceiling, which may prove the symmetric failure of the ceiling.