A Study on the Seismic Load on the Safety of Buildings and Social Allowable Damage of Buildings

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The most important thing in the prevention of earthquake disaster is to reduce the seismic damage under social allowable impact. The social impact can be estimated by the amount of seismic damage report in newspapers. The report ratios of seismic damage report to total report in newspapers about 28 earthquakes from 1945 to 1995 are surveyed for 14 days after earthquakes. The report ratio exponentially decreases after earthquake. The social allowable limit is estimated about 25 dead persons.Seismic hazard maps in Japan are analyzed by the probabilistic method using the seismic sources by the tectonics. Seismic occurrence model are determined from the modified magnitude distributions by the earthquake catalogs. The seismic hazard map of the maximum acceleration and the velocity are calculated using these parameters.A seismic urban factor of the structural seismic load to prevent seismic structural damage in the social allowable limit is analyzed for the wooden houses in 694 cities in Japan using the seismic hazard model and the structural strength model obtained by the Kobe earthquake. The urban factor is estimated as 1.6 when ground motion ratio 1.7. However, the urban factor is estimated as 1.8 when building ratio grows up to 16. The correlation coefficient of number of buildings to the urban factor is higher than that of ground maximum velocity.