Reinforcement Effect of High-Strength Bolts for Stop-Hole under Out-of-Plane Bending Loads

Abstract

The base metal at a stop-hole edge will be in out-of-plane torsion under bending loads to resist bolt tightening and weaken the reinforcement effect. By carrying out numerical simulation and fatigue tests, the effect of bolt reinforcement for stop-holes under out-of-plane bending loads was analyzed and the influence degree of reinforcement form, pretightening force, and eccentric loading on the maintenance effect were clarified. By carrying out real bridge application and dynamic stress monitoring, the effect of bolting for cracks subjected to out-of-plane deformation was explored. The results demonstrate that bolt reinforcement can significantly restrain the in-plane tension and out-of-plane shear deformation and alleviate fatigue damage accumulation at the crack tip to arrest continuous growth. The reinforcement effect of double bolts is remarkable and will not cause excessive local stiffness to induce new fatigue cracking. An excessive increase in the pretightening force cannot effectively improve the reinforcement effect and even aggravates the risk of cracking at the bolt edge, while a reasonable ratio of loading amplitude to pretightening force is approximately 3:1. The fatigue life of components is negatively linearly related to the nominal stress at the bolt, according to which the fatigue life can be quantitatively evaluated.