Different flexibility formulae for finite element modelling and analysis of the dynamic behaviour of a structure with bolted joints

Accurate representation of bolted joints in the finite element (FE) model of a built-up structure is a crucial factor in ensuring the accuracy and reliability of the dynamic behaviour prediction of the structure. Modelling of bolted joints in industrial structures has not been widely and thoroughly studied, especially in the dynamic response of the bolted joint itself. The aim of this work is to investigate several flexibility formulae for the calculation of the stiffnesses of CBUSH elements for the modelling of the bolted joints. The flexibility formulae used in this work are attributed to Huth, Tate & Rosenfeld, Boeing, Swift and Grumman. The results of the normal modes analysis of the FE models with different flexibility formulae were compared with those obtained from the experimental modal analysis (EMA). EMA was performed to measure the natural frequencies and mode shapes of the structure with bolted joints. The total errors calculated from the comparisons between FE and EMA were recorded for all flexibility formulae. The results of the investigation demonstrated that there are noticeable variations in the total errors recorded using different flexibility formulas for the CBUSH element representing the bolts in the FE model of the structure with bolted joints. It was found that the Swift’s flexibility formula is the most appropriate for the prediction of the natural frequencies of the structure with bolted joints.