Wavelet based experimental damage calibration using beam-moving load interaction model

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Pakrashi, Vikram
O'Connor, Alan J.
Basu, Biswajit
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Civil-Comp Press
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This paper presents a study of wavelet based prediction curves for the extent of damage using experimental data from the spatial domain. The methodology is illustrated through experiments on a simply supported beam traversed by a model two-axle accelerating vehicle. The beam is made of phenolic material and has an open crack situated on its underside. The proposed wavelet based damage calibration technique has been successfully employed to calibrate the extent of the damage for a range of crack depth ratios. Both static and dynamic cases are considered for this purpose. The damaged static and dynamic deflected shapes have been considered to be the spatial data required for the subsequent wavelet analysis based damage calibration. The calibration on dynamic deflected shapes has been carried out by considering the movement of the model two axle vehicle over the simply supported beam with an open crack to be a source of excitation and the dynamic deflected shapes have been identified through a digital video camera recording followed by an image processing based technique. The dynamic deflected shapes are acquired corresponding to various extents of damage. The identification of static deflected shapes has been performed likewise. The depth of the open crack in the simply supported beam has been gradually increased and the evolution of the damage has been related to the extent of the local maxima of the wavelet coefficients at the location of damage. A wavelet analysis based damage extent prediction curve has been achieved in the process. Consistent comparison with static deflections due to the presence of the same two-axle vehicle has been performed. The methodology is observed to be important for the health monitoring and assessment of bridge structures in its operating condition through the use of bridge-vehicle interaction data in the spatial domain. The proposed calibration technique is applicable to bridge-vehicle interaction data and can be beneficial in situations where the structure can seldom be closed down to obtain structural health monitoring data. The static calibration is simple, fast and efficient if the static deflection or strain data is spatially available by loading a bridge with a static and preselected vehicle of known weight.
Wavelet , Open crack , Beam-vehicle interaction , Damage calibration
Pakrashi, V., O'Connor, A., Basu, B., 2007. Wavelet Based Experimental Damage Calibration using Beam-Moving Load Interaction Model, In: B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 187, 2007. doi:10.4203/ccp.86.187
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