Fundamental Study for Slip Resistance Improvement of High-Strength Bolted Joints Subjected to Shear and Tension

Abstract

The objective of this study was to refine the slip resistance formulas for high-strength bolted joints subjected to combined shear and tension forces. Traditional formulas typically assume that the prying force generated at the contact surface does not contribute to the slip resistance. To explore the influences of the prying force on slip resistance, a trial design was conducted based on the Specifications for Highway Bridges and Recommendation for Design of High Strength Tensile Bolted Connections for Steel Bridges, with variations in parameters such as bolt diameter, bolt pitch, joint flange thickness, and joint flange material. Additionally, numerical analyses were performed to validate the design methodology incorporating prying force. The trial design results demonstrated that the slip capacity improved when the prying force was considered, especially in cases where the external force direction ranged between 27.6 and 90 degrees. The maximum observed improvement in slip capacity was a factor of 1.2. Moreover, the slip resistance of joints with thinner flanges was enhanced when prying force effects were accounted for. This increase in slip capacity due to prying force was further corroborated through fine element method (FEM) simulations. Finally, the findings suggest the potential for enhancing joint compactness and slip resistance.