Influence of material properties on the elongation of tendons

The elongation variation between the theoretical and real elongation of a post-tensioned tendon is used as one of the measures of quality in post-tensioning. The South African design standards (Sans 2001-CC1 and Colto) prescribe an elongation variation limit of ±6% and an average variation limit of ±3%. Most often these limits are exceeded in practice. If the elongation variation of a tendon falls outside the prescribed elongation limits it must be assessed by the engineer. This paper analyses the data of bonded tendons from numerous post-tensioned structures. The aim of this study is to determine the influence of material properties on the elongation variation of tendons in these structures. The structures ranged from reservoirs (Mthatha, Malendela and Kwa-Mashu) to viaducts (Jean Avenue P76-P80 and John Vorster P6-10). To achieve this, selected stress–strain graphs of tendons from these structures are presented and discussed.