Seite - 919 - in Book of Full Papers - Symposium Hydro Engineering

hazard and local site effects for large dams and evaluates six large dams, which have a height from river bed between 20.3 m and 89.0 m in the Kucuk Menderes and Gediz basins (Table 1). Table 1. Physical properties of dams considered for this study. No Dam Basin Height from river bed (m) Completed Year Volume of embankment (hm3) Volume of reservoir (hm3) 1 A.Kutlu Aktaş K.Menderes 15.3 1997 0.28 16.61 2 Balcova K.Menderes 63.4 1980 1.11 7.76 3 Gordes Gediz 82.9 2010 4.54 448.46 4 Guzelhisar Gediz 89.0 1982 3.21 158.00 5 Tahtali K.Menderes 54.4 1999 3.37 306.65 6 Urkmez K.Menderes 32.0 1990 0.98 7.92 2. MATERIALS AND METHODS For this study seismic study has been carried out by deterministic and probabilistic seismic hazard analyses. The deterministic seismic hazard analysis (DSHA) considers a seismic scenario that includes a four-step process. It is a very simple procedure and gives rational solutions for large dams because it provides a straightforward framework for the evaluation of the worst ground motions. The probabilistic seismic hazard analysis (PSHA), which is widely used for dam sites, considers uncertainties in size, location and recurrence rate of earthquakes. For the seismic hazard analysis of each dam site, all possible seismic sources were identified and their potential was evaluated in detail, as based on the guidelines given by [1] and the unified seismic hazard modeling for Mediterranean region introduced by [2]. Four separate predictive relationships for horizontal peak ground acceleration were used for this study [3,4,5 and 6]. Some institutions have defined some earthquake levels for dynamic analysis of dam structures. In this study, earthquake definitions given by FEMA were considered for seismic hazard analyses [7]. The Operating Basis Earthquake (OBE), which was defined by means of the probabilistic methods mentioned above, is the earthquake that produces the ground motions at the site that can reasonably be expected to occur within the service life of the project. MDE is normally characterized by a level of motion equal to that expected at the dam site from the occurrence of deterministically evaluated MCE. Safety Evaluation Earthquake (SEE) is the level of shaking for which damage can be accepted but for which there should be no uncontrolled release of water from the reservoir. Author states that most of large dams in Turkey were analyzed by using these definitions in past. ICOLD [8] also some earthquake definitions for dynamic analysis of dams. Author mentions these definitions more detail on their research [9]. Some methods are used to quantify the total risk factor of a dam. One of them considers the seismic hazard of the dam site and the risk rating of the structure separately [10[]. According to this method, the seismic hazard of the dam site regardless of type of dam, can be classified into four groups from low to extreme. This is a quick way for rating the seismic hazard. The hazard class of a dam site obtained from this method provides a preliminary indication of seismic evaluation 919