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<br />I <br />I <br />I <br />I <br />I <br />I <br />I I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I' <br />I <br />I <br />I <br />I <br /> <br />in this case. Normally, the reservoir would be emptied in early fall and it <br />would not be typical operating procedure for the reservoir to be full throughout <br />the winter. <br />The Bureau defines an "unusual" loading combination to be the maximum <br />design reservoir elevation combined with the effects of mean concrete tem- <br />perature occurring at that time. This would correspond to the maximum normal <br />water surface at elevation 10,978 feet with January temperatures as previously <br />described. The loading condition for overtopping by a probable maximum flood <br />would also be considered an "unusual" loading condition. <br />The 'Iextreme" loading combination is defined as any of the above usual <br />loading combinations plus the effects of a maximum credible earthquake. In this <br />analysis the extreme loading combination is represented by the maximum normal <br />water surface elevation, June 14 temperatures and a earthquake loading of 0.16g. <br />, Input Parameters <br />For purposes of analysis, the dam was divided into seven arch sections <br />each 10 feet thick and eleven cantilever sections of various widths. The <br />stresses in the dam were analyzed using the parameters shown in Table IV. <br />Values for for Poisson's Ratio of concrete and rock and the coefficient of ther- <br />mal expansion of concrete were based on parameters recommended by the Bureau of <br />Reclamation which may be assumed for preliminary studies when no test data are <br />available. Values of concrete unit weight, modulus of elasticity of concrete, <br />and modulus of deformation of the rock mass were based on laboratory results. <br />Dam thicknesses were based on actual field measurements. <br />It was assumed that the modulus of elasticity of concrete for the <br />existing dam was 1.5 x 106 psi. On the basis of laboratory tests on core <br />samples, the concrete modulus was found to range from 2.4 to 5.2 x 106 psi with <br />an average of 3.7 x 106 psi. The average concrete modulus based on the correla- <br />tion between pulse velocities and concrete modulus yielded an average value of 2 <br />x 106 psi. Since the existing structure cannot be considered as a massive homo- <br />-19- <br /> <br />, 1 <br />