Finite Element Modelling and Updating of a Bolted Structure Using Elements Representing the Stiffness Members, Bolts and Affected Areas of the Joints

Efficient and accurate analytical representation of bolted joints in an assembled structure for the prediction of the dynamic behaviour of the structure has been a crucial unsolved issue in the finite element (FE) community. 3D modelling of bolted joints, possessing a large number of degrees of freedom, leads to very high computational time. This paper proposes an efficient representation of bolted joints for the prediction of the dynamic behaviour of a bolted structure. The FE model of the bolted joints was developed using CBUSH element connectors for bolt shanks and CELAS element connectors for the stiffness of the members at the affected areas of the bolted joints. The results of the normal modes analysis of the FE model of the bolted structure were in a very good correlation with experimental modal analysis (EMA) counterparts quantified by a range of MAC values between 0.91 to 0.99 for all modes. Finite element model updating was used to improve the accuracy of the FE model of the bolted joints. The updated FE model of the assembled structure was validated with the physical tested structure. It was found that the comparison of the results has shown good agreement. In addition, the natural frequencies and mode shapes predicted from the proposed model have been found to be more accurate than the results obtained from the previous analytical models reported in the literature on bolted joint modelling of dynamic behaviour investigation. The proposed model can be used for a large and complex structure.