Sensitivity-based finite element model updating of a pontoon bridge

Abstract

4Numerical models of large civil engineering structures are prone to errors and uncertain system parameters, which inevitably affect the ability of such models to accurately predict dynamic behaviour. Finite element (FE) model updating can be used to calibrate the numerical models towards the observed behaviour. In this paper, a case study of the sensitivity method in FE model updating is presented. The methodology is applied to the Bergsøysund Bridge, which is a long-span floating pontoon bridge in Norway. A system identification is performed based on acceleration data and thirty vibration modes are identified. The FE model is calibrated by reducing the difference between the identified and numerical natural frequencies and mode shapes of the bridge. The model uncertainties are parametrized with a total of 27 parameters. We demonstrate how an analytical sensitivity matrix can be constructed for floating structures, where the system mass and damping matrices are functions of frequency due to fluid-structure interaction.After updating, the mean error in natural frequencies is decreased from 3.23% to 2.34%, and the average MAC number is increased from 0.87 to 0.94. Although the largest errors are significantly reduced, the updated parameters are believed to be affected by noise from the system identification. Challenges related to the presence of very closely spaced vibration modes are also shown, in which matching the identified modes to the modelled modes becomes difficult. This study indicates that models of large bridges can be significantly improved, but many practical issues still exist.

Model updating of seven-storey cross-laminated timber building designed on frequency-response-functions-based modal testing

“…Sometimes, a criterion that combines the MAC value and the frequency is used (e.g. Petersen & Øiseth, 2017), but in our case, the frequencies in question are so close that such a criterion does not separate between a good and a bad mode pair. We used the Auto-MAC matrices in order to find matching mode pairs.…”

The Use of a Vibro-Acoustic Based Method to Determine the Composite Material Properties of a Replicate Clavicle Bone Model

“…The methodology of updating FE models with experimental vibrational data is widely used in civil engineering applications [ 24 , 36 ]. Besides civil engineering applications, this methodology also showed value in biomechanical applications where cadaveric bone models were studied [ 25 , 29 , 30 , 31 , 32 , 37 ].…”

Experiences from the Five-Year Monitoring of a Long-Span Pontoon Bridge: What Went Right, What Went Wrong and What’s Next?

“…This encompasses both the structural part of the model and the excitation model. This may furthermore be subdivided in the following sub-tasks: (i) evaluation of accuracy of structural model and excitation model, with reference to measurements; (ii) model updating [3]; (iii) system identification, both as a part of the first objective and by itself to study the behaviour of the structure [4]; and (iv) force identification [5].…”