A Moment-Rotation Model of Semi-Rigid Steel Structure Joints with Bolted Connection

Abstract

ANSYS software was used to analyze the moment-rotation relationship of semi-rigid steel structure joints with bolted connection. A parametric study was conducted to examine the influence of eight key variables—including bolt number, bolt grade, angle steel grade, bolt diameter, angle steel thickness, angle steel width, preload magnitude, and friction coefficient—on the bending behavior of semi-rigid joints with bolted connection. Parametric analysis reveals that the initial rotational stiffness is most significantly influenced by the bolt diameter, the width and thickness of the angle steel, the bolt preload, the coefficient of friction, and the bolt number. The stiffness exhibited an average increase of 50.6% for every 4 mm increment in bolt diameter from 12 mm to 24 mm. Expanding the angle steel width from 50 mm to 75 mm resulted in a substantial 88.5% average increase in stiffness, while a further width increase from 75 mm to 110 mm led to a smaller average increase of 17.4% per 17.5 mm. Similarly, the stiffness rose by an average of 33.8% for every 2 mm increase in the thickness of the angle steel within the 4 mm to 10 mm range. A 25% increase in bolt preload correlated with a modest average stiffness gain of 2.7%. The rate of stiffness improvement diminished with increasing friction coefficient. In contrast, the initial rotational stiffness exhibited a relationship that is approximately linear with respect to the quantity of bolts. Regarding the ultimate bending moment, the key influencing factors were identified as bolt diameter, preload, coefficient of friction, and number of bolts. The ultimate moment demonstrated a non-monotonic relationship with bolt diameter, characterized by an initial increase, followed by a decrease, and then a sharp subsequent rise. Linear enhancements in the ultimate moment were observed with increases in both bolt preload and coefficient of friction. Furthermore, the ultimate bending moment showed a gradual increase with the number of bolts. Based on the results, a bending moment-rotation curve model of joints with bolted connection is established, and the expression of each parameter in the model is calculated. This model can be applied to simulation of the bending performance of semi-rigid joints with bolted connection.