Local Bond-Stress to Slip Relationships for Hot Rolled Deformed Bars and Mild Steel Plain Bars

Abstract

A large number of tests were carried out to determine statistically reliable bond-stress to slip relations for 16 mm diameter hot rolled deformed bars and mild steel plain bars; two concrete covers, two directions of bar pull relative to the settlement of concrete, and different magnitudes of bar back load were used. A concrete embedment length of 38 mm or four times the deformed bar lug spacing was chosen. A considerable scatter was observed to slip curves and this confirms the necessity of statistically designed experiments. The maximum bond stress was not found to be significantly affected by the magnitude of the bar back load, but nevertheless it increased with increasing concrete cover and increased to a lesser extent when the bar was pulled in the opposite direction to that of casting as compared to pulling it in the same direction. /Author/