TSUNAMI ANALYSIS OF STRUCTURES: COMPARISON AMONG DIFFERENT APPROACHES

The widespread damage caused by past tsunami, e.g. 2004 Indian Ocean Tsunami and 2011 Great East Japan tsunami, has
\nmotivated several research activities in tsunami engineering. The behaviour of buildings subjected to tsunami actions has
\nreceived particular attention. Some studies have been published regarding the estimation of tsunami action; many papers, as
\nwell as existing building codes suggest modelling the tsunami-structure interaction with an equivalent force approach.
\nThese literature papers propose that the tsunami force and its distribution along the height of the structure are strictly related
\nto the features of the tsunami flow, e.g. flow velocity and inundation depth. However, there is a lack of published literature
\nconcerning the analysis methodologies to adopt for estimating the response of buildings to these tsunami loads. A question
\ntherefore arises as to which analysis method is the most appropriate in the case of tsunami inundation of buildings and
\nwhether the nonlinear static analysis method, commonly used in earthquake engineering, is suitable for this case.
\nThis paper presents a study aimed at shedding light on analysing buildings subjected to actions due to tsunami inundation.
\nIn particular, three different analysis methodologies of constant-height pushover (CHPO), variable-height pushover
\n(VHPO), and time-history (TH) analyses are compared in terms of their abilities to predict structural response. An existing
\n10-storey reinforced concrete tsunami evacuation building in Japan is considered as case study. A distributed plasticity
\napproach is adopted to model the RC frame structure. Two different load patterns, i.e. triangular and trapezoidal, are
\nadopted to distribute the tsunami force along the height of the structure. The two pushover analysis methodologies, i.e.
\nCHPO and VHPO, are compared to TH analysis in terms of their abilities to predict structural response for an extensive set
\nof simulated tsunami inundation time-histories. It is found that the results of VHPO provide a good prediction of the
\nengineering demand parameters obtained from the TH analysis under a wide range of tsunami time-histories. CHPO gives a
\nworse prediction of the demand; it overestimates interstorey drift ratio and underestimates column shear by about 5-20%. It
\nis concluded that pushover methods are a good proxy for TH. In particular, it is recommended that VHPO be used in future
\nanalysis of buildings subjected to tsunami. It should be also highlighted that pushover methods may be inadequate in cases
\nwhere the tsunami inundation force time-history is characterised by a double-peak, which subjects the structure to a twocycle
\nload.