Estimating response of structures to earthquake-induced tsunami: A simple approach per unidirectional analysis

The orientation of a structure with respect to the direction of propagation of tsunami wave may often be arbitrary. As such, it may be convenient to consider the tsunami wave as a combination of two orthogonal pair. The response of structures may then be computed to the simultaneous action of two components (bidirectional) covering multiple incidence angles. However, analysis of structures in three-dimension under two orthogonal components is a daunting exercise for routine design. Against this backdrop, beginning with the validation of the simulation of tsunami against real records, a detailed scrutiny of the response of simple building frames to tsunami is made over a range of orientations per both unidirectional and bidirectional analyses. This indicates the sensitivity of response over orientations and suggests that the maximum response to a bidirectional tsunami attack can be closely estimated by unidirectional analysis at appropriate orientations. This reveals the existence of the most intense orientations in which the response to unidirectional loading may approximately represent the maximum response to bidirectional loading over all orientations. Observing statistically significant positive correlation of tsunami potential (Pd) and peak destructive potential (Id) to the response to unidirectional tsunami attacks, these pure tsunami parameters are selected as suitable intensity measures (IM). Analytical (as well as graphical through standard Mohr's circle) expressions are then derived for the orientations in which such IM can assume the maximum. It is shown that the unidirectional analysis conducted in these orientations can closely estimate the maximum response to bidirectional attacks out of all possible orientations for single story and multistorey building frames. Hence, the straightforward unidirectional analysis in the most intense orientations may be adopted for design of coastal structures.