Seismic fragility functions for a pervasive unique form of construction with very high potential for social losses in Trinidad and Tobago: Two-story houses

The twin-island republic of Trinidad and Tobago is fortunate to have a long history of abundance of natural resources resulting in its being a major source of economic support for the English-speaking sovereign states of the Caribbean. The economic stability of the Caribbean is threatened, via a domino effect, by the current prevalent form of residential structures in Trinidad and Tobago because of a lack of conformity with proper seismic design in an earthquake-prone region (SS of 1.1 g–1.8 g). Continuing from a previous study of single-story houses in Trinidad and Tobago, fragility functions for three types of typical two-story residential structures were derived using Incremental Dynamic Analysis considering both aleatory and epistemic uncertainties. The selected ground motion records are compatible with spectra derived for Trinidad and Tobago. Fragility functions for the structures are with respect to limit states of slight, moderate, extensive, and complete damage as well as out-of-plane dynamic instability. These fragility functions can be used for regional risk assessment hence the derivation of disaster mitigation and management plans thereby avoiding a major crisis in the Caribbean.