Cracking in Norfork Dam
F. W. Sims, James A. Rhodes and Ray W. Clough
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The development and detection of major transverse crocks in o moss concrete gravity dam is traced from the construction period through severol yeors of project operation. Methods for determining the extent and size of a principal crock in one block ore described. The results of structural behavior instrumentation observations showed the crock widths hove not changed sub-stantially, that the structure exhibits on elastic response to live loods and temperature variations, and that there has been no opparent change in the stability of the structure during the post 10 years. Application of the finite element method in the theoretical stress and displacement analysis of a cracked and uncracked gravity dam section is described. Results show stress concentrations of the order of 500 psi for the most unfavorable conditions of loading and specific crack height, and that only a moderate increase in maximum stress, to about 600 psi, will exist even when no limits ore imposed on crock height. Norfork Dam is considered to be safe, with a single transverse crack existing in most spillway monoliths, under normal loading conditions which may be expected. Provisions ore being mode to limit adverse hydrostatic pressures beneath and within the structure.