Values for k should be given in technical approval documents, and will generally be in the range 0.005 < k < 0.01 per metre. The value depends on the quality of workmanship, on the distance between tendon supports, on the type of duct or sheath employed, and on the degree of vibration used in placing the concrete.
The above recommended values for u and k are mean values. The actual values used in design may be increased or decreased, depending on standards of control, workmanship, special precautions, etc., provided that the selected values can be justified.
(9) Time dependent losses should be calculated from:
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