Volume 13, Issue 2 (2013)                   MCEJ 2013, 13(2): 1-15 | Back to browse issues page

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1- Tarbiat Modares University
Abstract:   (10089 Views)
Abstract: No dam could be safely designed without functionality dependence on reliable performance of a number of appurtenant structures. Gates are the main appurtenant structures responsible for controlling  water flow from the reservoir. Earthquakes induce acoustic and surface waves in the reservoir and cause hydrodynamic pressure on the adjacent gates. Hydrodynamic pressures might surpass hydrostatic pressure on some locations of the dam upstream face. Some engineers use the hydrodynamic pressure solution concerning  to  axi-symmetric offshore and coastal structures for  the design of such hydro-mechanical  gates. Flexibility  of these gates may magnify the hydrodynamic pressure due to severe generation  of vibrations separate from the dam body itself even for those installed within the dam bodies. This statement reflects the design philosophy of secondary structures. Fundamental frequency of such gates are usually reduced due to  the presence of infinite fluid in their vicinity. Therefore the  study of their behavior is somehow complicated during the earthquake. Design regulations of hydraulic structures, demand the hydrodynamic pressure as a design action and usually admits its simple calculation from the Westergaard formula. In this article, by using floor response spectrum in gate level which is used to design the secondary systems and also the spectral acceleration parameter in gate level which is used based on predominant frequency of gate-reservoir, the common relation of gate design against hydrodynamic pressure has been corrected. Then a new non-dimension factor is suggested for sliding rectangular gates in different levels of dam body that is related to the performed analyses and log-normal distribution of data.. In general for various conditions the dimensionless coefficient of Westergaard formula changes  from 0.875 to widely varying values between 0.25 to 2.5 when using the base acceleration. However when the spectral acceleration of the floor response spectrum is used for the fundamental frequency of gate-reservoir, this coefficient is more precisely determined for vertical rectangular gates.
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Received: 2013/08/17 | Accepted: 2013/04/21 | Published: 2013/08/17

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