Real road load compared to standard load for Brazilian bridges

The first objective of this paper is to compare values of global forces arising from moving loads specified by three international standards on box-girder bridges with different spans and support conditions and try to understand the differences. The second is to present a methodology for the analysis of loads arising from real vehicles over bridges. In the context of the Brazilian reality, the case of a traffic jam is studied. In this methodology a verification model based on the Monte Carlo simulation method is proposed. The data used are related to weighing and the number of vehicles from a highway in the countryside of the state of São Paulo. The third objective is to evaluate the adequacy of the present class 45 standard road load, given by the Brazilian standard (NBR 7188-1984), considering real road traffic and the requirements of the actions and safety standard (NBR 8681-2003). The conclusions are that the Brazilian conditions are different from those prevailing in developed countries, owing to heavier vehicles and traffic jams, and that the standard load is acceptable for two lanes and could be reduced for more lanes. These conclusions were the basis for current revision of the corresponding standard (NBR 7188-1984).