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194    CHAPTER 8 Seismic risk of RC water storage elevated tanks




































                         FIGURE 8.1
                         The general view of Sikh Oumedour tank.
                         should include supervision of conducted tests on materials, in order to meet general
                         terms and conditions of design, calculation, and execution. These quality controls are
                         used to limit the problems of form stability, the ductility, and the materials capacity
                         to deform plastically during high loads without significant reduction of strength.
                            During the consultation of the file in the archives, we are interested in the quality
                         of the concrete tank. We could read that the tests were conducted at a rate of three
                         samples of three compression test pieces of each, respectively, for 7, 14, and 28 days
                         for each corresponding element resistant to a class of concrete (foundations, support-
                         ing system, vessel, the dome cover, etc.). From the file, the concrete used for the dif-
                         ferent resistant elements have a characteristic strength of concrete between 20 and
                         25 MPa. These concretes are of average quality because they were carried out on site
                         in conditions far removed from those of concrete mixing plants equipped with mea-
                         surement and weighing instruments. The parameter is classified as class B.

                         5.3 SEISMIC BEHAVIOR
                         The seismic action results in an abrupt horizontal or vertical displacement of the soil,
                         causing the deformation of the foundations and underground parts of the tank. In a
                         partially filled tank, seismic excitation puts part of the fluid in motion, which leads to
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