Experimental analysis of bolted connections: Snug versus preloaded bolts

The rotational stiffness of bolted connections can be properly predicted by means of the so-called "component method." In this method, the T-stub plays a fundamental role, because it is used to compute the stiffness contribution of the most important joint components. For this reason, an experimental analysis on bolted T-stub assemblies has been performed. On the basis of this analysis, the possibility of predicting the axial stiffness of the T-stub assembly is investigated. In addition, as the joint behavior is strongly influenced by the bolt preloading, the experimental analysis has been performed applying three different levels of bolt preloading and, starting from the obtained experimental results, simple rules to take it into account are suggested. Finally, the reliability of the relationships derived from the T-stub analysis has been verified through the application of the component method to the prediction of the rotational stiffness of a wide number of tested specimens concerning extended end plate connections, both with snug-tightened and pretensioned bolts, collected in the technical literature.