Analytical Study on Changes in Contact Pressure Distribution due to Expansion of Bulb Sleeve Annealing Range in Huck One-side Bolt Used in One-Side Construction

One-sided bolts are typically used for bridge repair and reinforcement. Unlike regular high-strength hexagonal bolts, they lack a head washer, with the large bulb of the bulb sleeve serving as the bolt head after plastic deformation. The shape of the large bulb is crucial because it dominates the contact pressure between the surfaces of the connection members and affects the performance of joints using one-sided bolts. This study focused on the contact pressure transmitted to connection members through the deformation of a large bulb, with the annealing range of the bulb sleeve as a parameter. Results show that expanding the annealing range by approximately 1 mm increases the outer diameter of the large bulb by 0.2 mm, decreases the peak contact pressure by approximately 8 N/mm², and widens the distribution range of contact pressure between the surfaces on the connection members.