Live load reliability index evaluation for post tensioned balanced cantilever bridges

Çakır, Berk Bora
The purpose of this study is to determine the level of safety of the segmental post tensioned bridges designed according to AASHTO LRFD. Main span lengths are 90, 120, 150, 180 are studied in this paper. Four types of trucks are used; H30-S24T and L (currently be in use to design bridges in Turkey), HL-93(AASHTO), KGM-45 (is a new type of load consisting both axle load and lane load). Statistical parameters of truck loads are determined according to the data gathered from the Division of Transportation and Cost Studies of the General Directorate of Highways of Turkey. Target reliability index for ultimate state is chosen as 4.5 at first, then Service 3 stresses with corresponding reliability indices for ultimate capacities are computed. Moreover, this study shows if it is suitable to use the AASHTO LRFD tension limit stress for Service 3 Load Combination. Computing the uncertainties of live load models, extrapolation factors are calculated for 75 years and results are compared whether the corresponding live load models are adequate for the service life of infrastructures. The most critical reaction is considered in reliability index calculations, the negative moment of pier zone. In addition, reliability indices are calculated for different level of stresses for Service 3 and optimum tensile limit stress is rearranged for Turkish Design Code.


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Citation Formats
B. B. Çakır, “Live load reliability index evaluation for post tensioned balanced cantilever bridges,” M.S. - Master of Science, Middle East Technical University, 2015.