Behavior-Based Resistance Model for Bearing-Type Connection in High-Strength Steels

This paper investigates the bearing resistance of bolted connections with consideration of bolt hole elongations. Based on the test results of 27 single-bolt connections and 36 two-bolt connections fabricated from three grades of high strength steels, Q550, Q690, and Q890, with nominal yield stress of 550 MPa (80 Ksi), 690 MPa (100 Ksi), and 890 MPa (129 Ksi), the applicability of existing rules to limit the excessive elongation of bolt hole is evaluated. The comparison shows that current limitations of bolt hole elongation may overestimate the deformation capacity of connections with small end distance or with small bolt hole diameter. To find the balance between the bearing strength and the bolt hole elongation of bolted connections, a quantified load-displacement model is proposed based on a growth model. The key parameters affecting the shape of the curve are identified and analyzed. Based on the test results and the numerical simulations, global and local behavior transition states are identified. Related resistance formulae are established for these two behavior-transition states. A three-stage process for the development of bearing resistance is proposed. This three-stage bearing process describes the development of bearing resistance in relation to bolt hole elongation. A behavior-based resistance model with the flexible adjustment of reserved safety is proposed. According to the proposed resistance model, a reasonable bearing resistance design with consideration of the bolt hole elongation can be achieved. (C) 2020 American Society of Civil Engineers.