Response of Vertically Irregular Buildings to Tsunami

Structures with vertical irregularity are common for the purpose of good ventilation, lighting aesthetics etc. Seismic vulnerability of these structures relative to their symmetric companions has been studied in the past. Within the context of seismic loading, angle of attack of the excitation with respect to a principal axis of the structure, i.e., incidence angle is known to play a crucial role. With the increasing occurrence of a tsunami as in evidence worldwide, the response of vertically irregular buildings to tsunami loading taking the effects of incidence angles into account appears significant. In the present study, to achieve such end, a number of vertically irregular buildings are analyzed due to a set of generated tsunami histories. Structures are modelled using advanced fibre model, whereas the adequacy of the tsunami histories generated using standard software is validated against results reported earlier. The response of the buildings is computed for several incidence angles. A characteristic intensity parameter for the tsunami loading is defined and calculated for each orientation. A compilation of the response quantities and the associated intensity parameters across orientations suggest that the orientation for the maximum possible response can be uniquely identified in advance for a given tsunami history. This can eliminate the sheer enormity of analyzing buildings for several incidence angles by a single incidence angle and can be a very significant input in design. By and large, the responses of vertically irregular buildings are found greater than those of the symmetric counterparts.