Comparison of Measured and Simulated Traffic Loading based on BWIM Data from the Millau Viaduct

Traffic load modeling on road bridges requires detailed information of both the actual traffic load impact and the resulting structural responses. Reviewing common approaches on the topic, two different principal strategies can be identified: direct analysis of sufficiently detailed measurement data—either records of the passing road traffic or the resulting structural response for the structure under investigation—, or evaluation of synthetic traffic generated by numerical traffic simulation based on statistical data representing the traffic characteristics at site. Ideally, both methods can be combined by calibrating a numerical simulation model by means of detailed measurement data (e.g. WIM or BWIM data), thus reducing the uncertainty in the numerical model while maintaining its high flexibility (e.g. evaluation of different structures or different traffic scenarios). Therefore, it is essential to identify those relevant aspects within a certain traffic record actually governing the part of bridge loading relevant for structural design and reassessment (i.e. extreme values of load effects), and accurately represent them in the numerical simulation model. With an extensive and detailed traffic data record at hand, covering a period of 180 days of BWIM measurements at the Millau Viaduct in Southern France, this study performs a comparison of traffic loading resulting from the recorded traffic stream directly and from traffic generated by numerical simulation. The comparison is performed for a set of different load effects and bridge lengths on different levels, regarding governing traffic characteristics and extreme values of resulting load effects. Based on the findings from this comparison, suggestions for appropriate modeling using numerical traffic simulations can be proposed.