Collapse mode-based fragility curves against tsunami for low- and medium-rise reinforced concrete buildings

This paper proposes tsunami fragility curves for low- and medium-rise RC building considering collapse modes, such as overturning and sliding, based on the examination of the database of damaged buildings during the 2011 off the Pacific coast of Tohoku Earthquake. Log normal distribution is assumed for fragility curves, and the median and logarithmic standard deviation are estimated. One of difficulties for mode-based fragility estimation is that it is impossible to identify the most contributing collapse mode beforehand. The maximum likelihood method using multi-nominal likelihood function (Nakamura & Ugata, 2009) is extended, so that no assumption is needed about the relationship between each collapse mode. Proposed fragility curves include statistical uncertainty considering limited number of damaged buildings in the database.