Assessment of Brazilian highway bridges’ live load models on five girders decks under free flow and traffic jam situations
Abstract
Design of Brazilian highway bridges is based on the NBR 7188 code, which prescribes a live load model composed by a 450 kN weight truck and a distributed load of 5 kN/m2, affected by an impact factor. In previous studies it was demonstrated that this loading pattern does not adequately reproduce the real traffic effects. Two load models that are more appropriate to represent actual Brazilian traffic were recently proposed; both were calibrated considering 2-girder deck bridges, with span length up to 40 meters. In these cases, the critical effects are due to the free flow of commercial vehicles, with dynamic effects. This paper describes the steps developed to verify the suitability of the previously proposed load models to the specific case of 5-girder bridges, spanning between 30 m and 50 m. For this span range, traffic jams scenarios are included in the analyses. It is concluded that the NBR 7188 load model is unsafe in several situations; furthermore, one of the load models proposed for two-girder bridges satisfactorily reproduces the real traffic in this new set of structures.
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