The Brazilian code NBR 7188 for highway bridge design prescribes a live load model consisting of a 3-axle vehicle plus a uniform load, which are both affected by an impact factor when considering dynamic effects. It does not play out actual traffic static effects and may be, in some cases, non-conservative. This work presents two load model configurations developed by gathering a real traffic database, traffic simulations, modeling of the dynamic interaction between vehicles and structure, and statistical extrapolations. Proposed load models comprise dynamic effects and were calibrated for two-lane single carriageway bridges with span lengths up to 40 m under free-flowing traffic. The target values of the effects were compared to those generated by the new proposed load models, as well as by the Brazilian design load model. Adequacy of the proposed models is demonstrated; results show that the effects generated by the Brazilian design load model are underestimated in many cases, particularly for negative moments in cantilevers.

Purpose: Realistic composite vehicles with 2, 3, 5 and 9 axles, consisting of a truck with one or two trailers, are addressed in this paper by computational models for vehicle–bridge interaction analysis.Design/methodology/approach: The vehicle–bridge interaction (VBI) models are formed by sets of 2-D rigid blocks interconnected by mass, damping and stiffness elements to simulate their suspension system. The passage of the vehicles is performed at different speeds. Several rolling surface profiles are admitted, considering the maintenance grade of the pavement. The spectral density functions are generated from an experimental database to form the longitudinal surface irregularity profiles. A computational code written in Phyton based on the finite element method was developed considering the Euler–Bernoulli beam model.Findings: Several models of composite heavy vehicles are presented as manufactured and currently travel on major roads. Dynamic amplification factors are presented for each type of composite vehicle.Research limitations/implications: The VBI models for compound heavy vehicles are 2-D.Social implications: This work contributes to improving the safety and lifetime of the bridges, as well as the stability and comfort of the vehicles when passing over a bridge.Originality/value: The structural response of the bridge is affected by the type and size of the compound vehicles, their speed and the conservative grade of the pavement. Moreover, one axle produces vibrations that can be superposed by the vibrations of the other axles. This effect can generate not usual dynamic responses.

The design of Brazilian highway bridges is based on the NBR 7188 code, which prescribes a live load model consisting of a 450 kN truck load and a distributed load of 5 kN/m2, both affected by an impact factor. Previous studies have shown that this load pattern does not adequately reproduce the effects of the real traffic. Two alternative load models that are more appropriate to represent actual Brazilian traffic effects were recently proposed; both were calibrated considering two-girder deck bridges, with span lengths up to 40 m. In such cases, the critical effects are associated with the free flow of heavy vehicles, including dynamic effects. This paper presents the procedures developed to assess the applicability of the previously proposed load models to five-girder bridges, with spans lengths ranging from 30 m to 50 m. For this span range, traffic jam scenarios are included in the analyses. The results indicate that the NBR 7188 load model is unsafe in several situations. Furthermore, one of the load models previously proposed was found to satisfactorily reproduce the effects of real traffic for this new set of bridges.