Study on Theoretical Elongation of Small Radius Prestressing Tendons in Anchorage Zone of Cable-stayed Bridge Pylon

In view of the phenomenon that the actual elongation of small radius prestressing tendons is slightly greater than the theoretic elongation, all kinds of factors that influencing the elongation of the tendons were analyzed and the constitution feature of the tensioning elongation of the tendons was pointed out.Started with the research of the position variation of small radius prestressing tendons in the corrugated pipe during the tensioning process,the variation in geometry length of the tendons from ideal state to that before the corrugated pipe distorts was obtained.The compression factor ξ was introduced,the formula to calculate the additional elongation of the tendons was given,and a calculation method of the geometry elongation which caused by the deformation of the corrugated pipe was proposed.Finally,the proposed method for calculating the tensioning elongation was verified by the data from several engineering projects.The results show that the deviation of elongation between measured value and calculated value can be controlled within the stipulation of the technical specification(±6%),which can fully satisfy the control requirements of tensioning small radius prestressing tendons.