Reliability Analysis of Externally Prestressed Concrete Bridge Girders


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Title: Reliability Analysis of Externally Prestressed Concrete Bridge Girders

Author(s): A. S. Nowak, A. E. Naaman, and S. C.Ting

Publication: Special Publication

Volume: 120


Appears on pages(s): 437-454

Keywords: bridges (structures); damage; deterioration; evaluation; girders; loads (forces); prestressed concrete; prestressing; reliability; repairs; serviceability; strengthening; structural analysis; unbonded prestressing; Structural Research

Date: 6/1/1990

Evaluation of existing bridges is an important part of the strategy of dealing with the deteriorating infrastructure. Load and resistance parameters are random variables because of uncertainties in load components, material properties, and dimensions. Therefore, the reliability of a structure is a convenient measure of its performance. The load and resistance models are first summarized. The major load components in bridges are dead load and live load. The live load model is based on the weigh-in-motion studies. Girder distribution factors are derived using special computer procedures for bridge analysis. Behavior of composite girders is considered using a nonlinear model. The basic characteristic of the section is the moment-curvature relationship. The reliability is measured in terms of the reliability index. The approach is demonstrated on evaluation of a prestressed concrete girder bridge. Three cases are considered: original design condition, damaged with corroded strands, and repaired by external prestressing. The load components and load-carrying capacities are evaluated and then the reliability indexes are calculated for the three cases.