Abstract
The coefficient of friction in an unbonded post tensioning system is influenced by many factors, and these factors include the thickness of lubricant or grease present in the system, clearance between the strand and the plastic sheath, surface characteristics of the strand and plastic sheath. In order to determine the effect of these factors, a series of friction tests were performed on two different diameters of strand, namely; 12.7 mm and 15.24 mm diameters. Through a regression analysis, it was found that the frictional force decreases with increase in the thickness of the grease and that friction increases with increase in the mass of the strand. The amount of friction was found to be dependent on the surface characteristics of the strand and plastic sheath, clearance between the plastic
sheath and the strand and the extrusion process of the plastic sheath.