. Journal of electricity . tes areopened and the dam will be over-topped by about 12feet of water. Theory of Construction — The design of this dam was based upon theusual assumption that all the water pressure be sup-ported by horizontal arching. The vertical cantileveraction which necessarily has to occar even in damsof slender cross section was simply assumed as in-creasing the safety of the structure to an unknowndegree. On the other hand, the stresses in the horizontalarches were determined in a similar way as for con-crete arches for bridges. Therefore not only thedirect stresses due to t
. Journal of electricity . tes areopened and the dam will be over-topped by about 12feet of water. Theory of Construction — The design of this dam was based upon theusual assumption that all the water pressure be sup-ported by horizontal arching. The vertical cantileveraction which necessarily has to occar even in damsof slender cross section was simply assumed as in-creasing the safety of the structure to an unknowndegree. On the other hand, the stresses in the horizontalarches were determined in a similar way as for con-crete arches for bridges. Therefore not only thedirect stresses due to the water and ice pressurewere considered, but also the stresses from shrink-age in the concrete and those due to changes in thetemperature of the arches. Temperature Consideration — For the purpose of design it was assumed thatthe shrinkage of the concrete was equivalent to adecrease in temperature of 18 degrees Fahr. in theupper poi-tion of the dam, and 9 degrees Fahr. in the 80 JOURNAL OF ELECTRICITY [Vol. 45—No. 2. Cross section of concrete arch dam, showing special features of reinforcement to withstand temperature changes and excessive tensile stresses. lower portion. The seasonal changes in the tempera-ture of the arches were assumed as a lineai functionof the combined action of the changes of water andmean air temperature. The maximum range of archtemperature considered was the variation of + 27degrees Fahr. in summer to — 31 degrees Fahr. invery cold winters, measured from the pouring tem-perature of the concrete. By considering the horizontal arches as hingedat the side abutments, the stresses in the archeswere obtained to somewhat over 850 lbs. per sq. the concrete and about 25,000 lbs. per sq. in. inthe steel. This example of arch dams presents two moststriking features: first, the heavy reinforcement ofthe horizontal arches from the crest of the dam tolittle above the foundation, and second, the high unitstresses occurring under the assumptions made. A
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