Optimal intensity measure assessment and developing fragility curves for submerged intake towers under near-fault ground motions

This paper aims to study probabilistic seismic demand models (PSDMs) of intake tower structures under the forward-directivity effects of near-fault earthquakes numerically using finite element method. The relationship between earthquake parameters and structural response was depicted to investigate the onset of damage to the structure. Furthermore, seismic demand hazard curves were developed to indicate the annual possibility of surpassing a particular EDP for any certain IM while taking into account the hazard level of the site or area. Finally, seismic fragility curves for estimating the initial vulnerability of intake towers after the occurrence of earthquakes with and without the FD effect are demonstrated. The results show that near-fault records with NFD effects provide more predictivity in measuring potential hazards induced by the intake towers and choosing optimal IM criteria than those with FD effects. It is also demonstrated that, unlike earlier studies in the literature in which peak ground acceleration and spectral acceleration at the first natural period were commonly chosen as optimal IMs, ASI, Cordova Intensity, and Two-period Intensity can also be appropriate IMs for seismic vulnerability assessment of intake towers.