Steel-encased pull-through tests of seven-wire strands
Pull-through tests of seven-wire strands were conducted to investigate the bond properties of strands with different surfaces. Three types of strands were tested, denoted old smooth, new smooth, and indented. Steel-encased specimens were used, and not only the bond and slip were measured, but also the tangential strain in the steel tube to investigate the normal stresses generated by the bond mechanism.
The tests show that the smooth strands behave stiffer initially than the indented strand. The new smooth has a higher bond capacity than the old smooth; for large slip values the new smooth even has a higher capacity than the indented strand. For slip values between 0.3 to 4 mm, the indented strand has the highest capacity. However, the indented strands also causes the largest tangential strains in the steel tube; i.e. the indented strands causes larger normal stresses than the smooth strands, which increases the risk for splitting failure. The two different types of smooth strands appear to cause approximately the same normal stresses.