A COMPARATIVE STUDY ON CHARACTERISTIC OF BOLT PRETENSION LOSS OF RELAXATION IN HIGH STRENGTH BOLT FRICTION JOINTS

Abstract

 The characteristics of decrease of bolt pretension by relaxation differ depending on the type of contact surfaces. To enhance the safety of bolted joints, it is important to verify that the tension of high strength bolt is retained proper level even after relaxation. By investigating characteristics of decrease of bolt pretension by relaxation referring to past literatures about high strength bolted joints, we showed the characteristics of decrease of bolt tension by difference of contact surface type; painting, rust, rough surface, sprayed surface, and galvanization surface. In addition, this study also dealt with the effect of the initial tension of high strength bolt, the type of joint, the length of bolt, the thickness of paint.