伝統的木造建築の耐震性に関する調査研究

• Published in: 住宅総合研究財団研究年報 Vol. 20; pp. 339 - 348
• Main Authors: 坂本 功, 大橋 好光, 河合 直人, 後藤 治, 渡辺 一正
• Format: Journal Article
• Language: Japanese
• Published: Housing Research Foundation "JUSOKEN" 1994; 一般財団法人 住総研
• ISSN: 0916-1864; 2423-9879
• DOI: 10.20803/jusokennen.20.0_339

In the recent trend of reassessment of wooden buildings it has been increasingly desired to build shrines and temples with wood instead of rein forced concrete in steel. However, according to the current method in which the bearing walls are considered as the primary elements for horizontal resistance, there remains many problems to be solved if we try to apply the structural system of traditional wooden buildings to these buildings. in addition, the continuous absence of coordination between those who involved in actual construction like carpenters and those who involved in research of structure has left many problems to be solved. The seismic performance of traditional wooden buildings was surveyed quantitatively. A case study was made on the damage in Kamakura brought by 1923 Kanto Earthquake. First, records and literature about the soil of Kamakura were collected and the thick and soft alluvium layer, were found along the coast and in the inland area. At the same time a research on the damage of wooden buildings in the area was performed through records and literature. The result shows the high damage ratio among wooden buildings and a certain correlation between the damage and the location of the alluvium. Through a questionnaire survey sent to as shrines and temples in the area in addition to references to literature and supplementary hearings, the following conclusions as to what types of buildings were damage ; 1 ) as for types of buildings, the damage ratio of main halls at Buddhist temples was rather high, 2 ) as for roof materials, the heavier materials like thatched roof or tiled roof caused heavy damage, 3 ) as for periods when the building was constructed, not much difference was found, 4) the higher the wall ratio was, the smaller the damage was found, and 5 ) the thicker the alluvium was, the heavier the damage was brought as in the case of wooden houses. There was also found a certain correlation of the damage ratio between houses and shrines and temples. As a result of this survey, there are well organized data sheets of these buildings, which will make it possible for a further study on individual buildings. For the next stage of this study, a structural analysis of these buildings by methods of response analysis will be made. 木造建物の再評価に伴って，社寺などの伝統的な構法で建てられてきた建築物についても木造で造りたいという要望が高まっている。しかし，これらの建物は，耐力壁を主要な水平抵抗要素とする現在の考え方によれば，そのまま建設することは難しく，また，戦後続いた現場関係者（大工など）と構造研究者の乖離の結果，これらの建物の耐震性に関しては未解明のままとなっていた。本研究は，これらの問題に応える端緒となるもので，民家や社寺などの伝統的な建築物が，実際にどの程度の耐震性を有していたかを定量的に把握することを目的としている。具体的には，関東地震における鎌倉市内の地震被害を通して，伝統的木造建築の耐震性を調べた。まず，鎌倉市内の地盤に関する文献を収集して，軟弱地盤と言われる沖積層厚を整理した。その結果，鎌倉には，海岸や内陸に厚い沖積層があることが分かった。並行して，鎌倉市内の木造家屋の被害を，文献を中心に調べた。その結果，木造家屋の被害率はかなり高く，また，沖積層厚とかなりの相関があることが分かった。また，市内の社寺建築を可能な限り拾い出し，それらについてアンケート，文献調査，及び補足ヒヤリングを実施して，どういう建物がどのような被害を受けたかを調査した。その結果，(1)形式的には，寺院建築では仏堂系の建物が被害率がやや大きい，(2)屋根葺材の種類では，茅葺きや瓦葺きなど屋根の重いものに被害率が大きい，(3)建設年代による差は小さい，(4)壁率が大きいものの被害率は小さい，(5)木造家屋と同様に，沖積層が厚いほど被害率は大きい，などが分かった。また，木造家屋の被害率とかなりの相関があることも明らかになった。なお，本研究の成果の1つとして，これらの建物のデータシートが整っており，今後，個別の建物の検討が可能である。また，これを基に，振動解析などの手法を用いた構造解析を行なう予定である。