十勝沖地震における鉄筋コンクリート造校舎の耐震性について : 被害建物と無被害建物の比較検討

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Failures of reinforced concrete school buildings due to 1968 Tokachi-oki earthquake, May 16, 1968, were investigated by comparing failed buildings with similar buildings in the same area which survived the earthquake. Most remarkable and important mode of failure of these buildings was the shear failure of the first story columns, mostly short columns. Natural period was measured, and structural analyses showed that calculated period, based on the uncracked section including finishings, was very close to the measured value if the building was safe or only partially damaged. However there was no remarkable diflerence between the calculated periods of safe and damaged buildings. Earthquake response was calculated for these buildings, As to the maximum relative displacement of the first story, again, there was no remarkable diflerence. Based on the elastic theory, shear strain and stress in the columns of the first story were calculated. It was shown that ther was remarkable diflerence in the shear strain and stress, and that shear stress may be approximately estimated if the base shear coefficient was evaluated. The base shear coefficient of low, rigid reinforced concrete buildings may be assumed to be approximately constant, or in other words, it dous not depend on the natural period of the structure. Thus, safety against shear failure of columns may be estimated by means of W_e/A, where W_e is the effective weight of the building as related to the particular column, and A is the cross-sectional area. Furtheremore, relation between shear strength and shear span ratio was studied. It was found that an empirical equation by Dr. Arakawa showed a very good agreement with the observed failure in the earthquake. Also it was shown that short columns were apt to fail because the stress concentration due to its high rigidity exceeds the increase in the strength.
1970-02-28

十勝沖地震における鉄筋コンクリート造校舎の耐震性について : 被害建物と無被害建物の比較検討

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