ABSTRACT
It is estimated that Brazil has around 120 thousand bridges. Historically, the country keeps no records of the number and the conditions of its bridges. Consequently, there is no information about the safety of Brazilian bridges based on the current live loads. This paper aims at addressing this problem regarding the prestressed bridges. Reliability assessment of 39 bridges were performed. These bridges have the span length varying from 14 to 60 meters. The girder spacing of selected bridges varies from 215 cm to 340cm. The bridge set is composed of girder bridges with 3,4,5,6,7 and 10 I girders and also box girders. The bridges are from different states in Brazil including Pernambuco, Ceará, Bahia, São Paulo, and Minas Gerais. Most of the bridges have a concrete strength of 40 MPa. The weigh-in-motion data were used to model the loads over these bridges and the safety level under the current Brazilian live load is computed. Data from two different WIM stations were considered to evaluate the traffic load. One station on Fernão Dias highway in the State of São Paulo which is comprised of two adjacent lanes in one direction and the 20 months of data were obtained (September 2015 to August 2017). The second station is in Rio Grande do Sul State collecting data from three adjacent lanes in one direction. The data is comprised of 78 days (March 2014 to June 2014). Probability of failure was estimated in terms of moment and shear. The strength state limit was evaluated in this study. It was found that Brazilian bridges present a high safety level with beta around 5 and 6. Also, for bridges designed with the current live load model, the reliability indices tend to decrease as the span length increases. This means that for larger spans the probability of failure is higher than the ones for shorter spans.
