The Influence of Lack of Fit and Redundancy on Dynamic Behaviour and Model Updating - A Case Study

摘要

The dynamic behaviour of a small framework comprising a small two dimensional doubly braced rectangular structure is examined. The length of one of the cross braces is adjustable by means of a turnbuckle allowing load to be transferred into the structure. The nature of the loading being measured by means of strain gauges mounted about the structure. The dynamic behaviour of the experimental structure is determined in the out of plane direction by means of a laser velocimeter while the structure is supported in conditions close to free-free. It is observed that very significant changes to the dynamic behaviour of the frame occur while the structure undergoes levels of loading well within serviceability limits. Resonant frequencies of the structure are found to be perturbed both upwards and downwards. Predictions of the perturbations to the resonant frequencies of the loaded structure are established with some success using non-linear finite element modelling (FEM) analysis procedures. These results indicate that the stress regime in structures should be taken into account when validating FE models against experimental data and in particular when using experimental data to update FE models.