Mechanical Characteristics and Design of Bolted T-Shape Flange Joints Subjected to Tensile Loadings

Bolted joints have been widely used in mechanical structures. However, a design of bolted joints has been carried out empirically. In designing a bolted joint, it is necessary to know a ratio of increment F_t in axial bolt force to an external tensile loading W, that is, the load factor φ=F_t/W. In our previous paper, the new formulation for obtaining the value of the load factor φ for a bolted joint in which two hollow cylinders were clamped was proposed by introducing the tensile spring constant K_pt for clamped parts. Then, it is shown that the values of the load factor of bolted joint obtained from our formulation are in a fairly good agreement with the experimental values. In addition, the effect of the position where an external load is applied to the joint is significant on the value of the load factor. In the present paper, a method for obtaining the value of the load factor for bolted T-shape flange joints in which two T-shape flanges are clamped by two bolts and nuts under tensile loadings is demonstrated using two-dimensional theory of elasticity. In the analysis of the load factor φ, the compressive spring constant K_c for a hollow cylinder around the bolt hole is calculated. The value of the correction factor K_c′/K_pt is also analyzed using the two-dimensional theory of elasticity. When the external tensile loads are applied to the joints, the bolts are inclined and as the result, the bending moment occurs in the bolts. A method for analyzing the bending stress in the bolts is also demonstrated. In the numerical calculations, the distance C between the bolt position and the center of T-shape flange is varied and the effect of the distance C on the load factor is examined. For the validation of the analyses, calculations are also carried out. Experiments to measure the load factor and the maximum stress due to the bending moment occurred in the bolts were carried out. The numerical results of the load factor and the maximum stress in the bolts are fairly coincided with the experimental results. Furthermore, a design method for the joints is discussed, that is, how to determine the bolt position C, the bolt preload for the external tensile loading, how to choose the bolt strength.