New Index for Earthquake Damage in Considering Response Spectra and Number of Cycle

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This study deals with a new index for earthquake damage in considering response spectra and number of cycle of response. The maximum acceleration has been used as a typical index for earthquake damage so far. Although great acceleration more than 1,000gal was recorded in the 1993 Kushiro-oki earthquake in Japan and 1994 Northridge earthquake in USA,little structural damage occurred. Not only the maximum acceleration or maximum response acceleration but also the number of cycle of great response acceleration should be considered for explanation of structural damage.Fatigue response spectrum is proposed in this study. This spectrum is combined with response spectrum and number of cycle, that is, x axis is natural period of structure, y axis is number of cycle in each response level and z axis is response level. Fatigue response acceleration spectrum, fatigue response velocity spectrum and fatigue response displacement spectrum can be evaluated from response acceleration spectrum, response velocity spectrum and response displacement spectrum, respectively. Based on fatigue response spectrum, FSI value (Fatigue Spectral Intensity) was estimated. This value is defined as a volume of fatigue response spectrum.The correlation between FSI value and earthquake damage is investigated using data of the 1993 Kushiro-oki earthquake, 1993 Notohanto-oki earthquake, 1994 Hokkaido Toho-oki earthquake, 1994 Sanriku Haruka-oki earthquake and 1995 Hyogoken-Nambu earthquake. This study is focusing on the damage to wooden houses and water supply pipelines.