Page - 1223 - in Book of Full Papers - Symposium Hydro Engineering

2. SEISMIC VULNERABILITY ASSESSMENT Seismic vulnerability is commonly assessed by estimating the probability distribution of EDP for a given IM, EDP|IM. The complementary cumulative distribution function of EDP|IM is used to compute the probability that EDP exceeds a certain level edp, given that IM = im. This estimation can be combined with a ground motion haza14rd hIM(im), to compute the mean annual rate of exceeding the EDP level edp [9]:      IM IMEDP imdhimIMedpEDPPedpR )()|()( (1) The ground motion hazard hIM(im) is the mean annual rate of exceeding the IM level im, obtained using probabilistic seismic hazard analysis. The conditional probability P(EDP>edp|IM=im) is called as the seismic fragility which is a plot of this probability against various IM levels. REDP(edp) is a measure of seismic reliability of structure. Relationships between ground motion IM and structural response EDP have been well established for various types of structures in the context of probabilistic seismic demand models. In this approach, probabilistic estimations of the EDP as a function of the IM is computed through statistical analysis of nonlinear dynamic analysis results under a set of earthquake ground motions [9]. 3. PULSE-LIKE RECORDS The near-field earthquakes are recorded close to active faults; they possibly include velocity pulses resulted from the forward-directivity. So they are categorized as “pulse-like” or “non-pulse-like”. The forward-directivity effects may be generated when the site is located at one end of the fault, and rupture initiates at the other end of the fault and travels towards the site, the arrival of the wave front is observed as a pulse with large amplitude that occurs at the beginning of the record. These effects are normally long period and are typically observed in the velocity time-history. However there may be backward- and neutral-directivity depending on the fault orientation and rupture propagation [1]. The velocity pulse may occur in the fault-normal direction; ground motion shaking in the fault-parallel direction is typically less intense. Directivity effects are a major concern for researchers studying velocity pulses, and the effects of these pulses on structures [9]. The period of the velocity pulse Tp, can be determined as the period associated with the peak of the original ground motion’s velocity response spectrum. It is an important parameter such that the ratio of the pulse period to the fundamental 1223