On the Design of Bolted Connections With Gaskets Subjected to Fatigue Loading

Abstract

Bolted connections subjected to fatigue loading are usually considered to be the “weak point” in a design. They usually are highly preloaded to increase their resistance to external dynamic loading resulting in selecting large bolt diameters. This paper presents a design method for calculating an optimal bolt diameter required for a specific fatigue-loading situation. When load is applied to the bolted connection, the bolt tensile stress increases and the members undergo a decrease in compression. Based on the fact that the decrease in the deformation of the connected members must be equal to the increase in the deformation of the bolt, expressions are derived for maximum and minimum forces and stresses on the bolt. Using Soderberg’s failure line, an expression is developed for bolt diameter. It implies that there exists an optimal safe bolt diameter satisfying the loading conditions. Using a lower-bound value of bolt preloading produced an expression for the critical diameter of the bolt in terms of maximum and minimum dynamic force applied, the yield strength of bolt material, the factor of safety, and the stiffness constant. Examples are given to illustrate the design procedure.