An Investigation on Axial Force Reductions of High-strength Bolts by Induction Heating for Paint-coating Removal

Abstract

Removal of anti-corrosion paint is key to the maintenance of aging structures. Previous investigations showed that heating high-strength bolts for coating removal reduces their axial strength. Herein, a series of experiments were conducted to investigate the effect of heating rate on axial force reduction, in search of possible methods to suppress this reduction. The high-strength bolts were heated to 200ºC, at different heating rates, and the changes in axial force were estimated, by measuring the strain at the bolt shafts as the temperature increased. The mechanism of the axial force reduction could be explained by the strain behavior at the bolt shafts. The results showed that the shorter the heating time was, the more the axial force was reduced, suggesting that heating bolts over 15-30 seconds suppressed the axial force reduction to 5% of the initially installed axial force of the high-strength bolts.