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Measurement based detection of vehicle weights considering the dynamic interaction between vehicles and bridge expansion joints

A traffic monitoring system especially detecting vehicle weights, based on measurement signals recorded during the crossing of vehicles over bridge expansion joints is proposed. For a proper approximation of the vehicle weight the dynamic behaviour of the bridge expansion joint as well as the dynamic motion of the vehicles induced by the pave-ment roughness have to be considered.

Signals measured during the crossing of a vehicle over an expansion joint contain beside the dynamic wheel forces further dynamic components due to the oscillations of the expansion joint. These mass inertia forces would lead to a poor approximation of the true axle loads which could be improved by intelligent signal processing algorithms consider-ing additional information obtained by theoretical considerations and numerical simulations of the expansion joint [1].
In most of the cases the matter of interest are the static axle or vehicle loads and not the measured dynamic ones. For this reason further investigations regarding the dynamic oscillations of the vehicles leading to a dynamic shift in the wheel forces are necessary. Concentrating on the dominating eigen mode shapes, the vehicles are modeled as multi body systems with rigid bodies interlinked via discrete spring and damper elements. Using the complex frequency re-sponse matrix of the linearized vehicle model, the power spectral density and therefore the variation of the vehicle oscillations due to random pavement roughness can be calculated. In this manner the accuracy of the approximation of the static vehicle weights can by quantified.
The developed weigh in motion system has been proven by numerous in field measurements using an instrumented vehicle where the wheel forces as well as the accelerations of the vehicle body had been measured [2].

References
[1] Mangerig, I., Friedl, R.: Dynamic Interaction between Vehicles and Expansion Joints, EURODYN 2014, Porto
[2] Friedl, R., Mangerig, I.: Wheel force amplification of road vehicles with regard to the loads exerted on bridges and bridge expansion joints, 10th Japanese-German Bridge Symposium, 16.-17.9.2014, Munich

Author(s):

Roland Friedl    
Universität der Bundeswehr München
Germany

Ingbert Mangerig    
Universität der Bundeswehr München
Germany