The effects of corrosion on the reliability of concrete bridge girders

The objective of this thesis is to model the strength losses due to corrosion of steel in concrete bridge girders and to develop an analytical procedure for evaluation of the effects of reinforcement corrosion on bridge reliability. The corrosion loss model is developed from information concerning the temporal availability of corrosives in the environment and the spatial variability of concrete cover in its properties and thickness. In the model, stochastic processes are utilized simulating the sample functions for concrete variability over space, as well as for corrosive availability through time. Both reinforced and prestressed concrete structures are considered.;The behavior of corroded conventional reinforced concrete members is evaluated. For axial tension members, closed form solutions are formulated. As for flexural members, a general numerical procedure is developed to evaluate the behavior of a member's section, considering the irregularity of the section's geometry and the nonlinearity in the properties of concrete and reinforcing steel.;In determining the effective prestressing force in a prestressed concrete member with corroded prestressing steel, closed form formulation is derived for both axial and flexural members. A numerical procedure, similar to the one developed for the conventional flexural reinforced concrete sections, but more intricate, is developed for evaluating the behavior of prestressed concrete members. Moreover, both noncomposite and composite structures, with either unbonded or bonded tendons, are included in the flexural members considered.;Stochastic finite difference methods are used to evaluate the responses of concrete beams, considering that the available local element behavior varies over the length of the member. Sensitivity studies are performed for the parameters involved in the stochastic model.;The developed methodology is demonstrated by examining the reduced safety for typical concrete bridge girders containing corroded reinforcing or prestressing steel. The structural safety is measured in terms of the reliability index. A longer projection period will produce a larger possible loading, and a smaller remaining amount of reinforcement due to corrosion. The resulting relationship of reliability decreasing with time is expected. The developed procedure for the evaluation of corroded concrete bridge girders can also be applied to new bridges.