| The increasing use of high strength concrete in pretensioned concrete bridge girders drove the development of new prestress loss provisions that were introduced to the AASHTO LRFD Bridge Design Specifications in 2005. The provisions have led to industry concerns because of the complex implementation of the equations and seemingly unconservative results. The research documented in this thesis studies the models used historically for prestress loss analysis in bridge girders, then proposes a simplified method for design. The simplified method is derived from fundamental principles of mechanics and validated by comparison with a detailed time step analysis. Monte Carlo simulation is used to consider the inherent uncertainty in time-dependent analysis of concrete girders. The simplified approach, called the Direct Method, is formatted for inclusion in the AASHTO LRFD Bridge Design Specifications. |
