Abstract
When tension is applied to steel tendons they elongate in proportion to the tensile force, as
predicted by Hooke’s law. This elongation is used by the South African standard on concrete
structural works (SANS 2001-CC1) and South African standard specification for road and
bridgeworks (COLTO) to determine the adequacy of the force applied in a tendon. The
standards prescribe an elongation variation limit of ±6% and an average elongation variation
limit of ±3%. According to these standards, if the elongation variation of the tendon falls
outside these prescribed limits it must be brought to the attention of the engineer. The scatter
of tendon elongation results is often greater than the range prescribed by these standards. This
usually requires the contractor to re-tension the tendons at huge financial costs. In most cases
the results obtained after re-tensioning are the same. This paper analyses tensioning data
obtained from a variety of projects that have been completed in South Africa in recent years.
The aim of this investigation is to determine the causes of variation in elongation and suggest
adjustments, if any, to the current elongation variation.