Flexural Reliability of Reinforced Concrete Bridge Girders Strengthened with Carbon Fiber-Reinforced Polymer Laminates

Abstract

This paper presents the development of a resistance model for reinforced concrete bridge girders flexurally strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) laminates. The resistance model is limited to pure flexural failure and does not address shear failure, laminate debonding, or delamination. The resistance model is used to calculate the probability of failure and reliability index of CFRP-strengthened cross sections. The first-order reliability method is employed to calibrate the flexural resistance factor for a broad range of design variables. The study shows that the addition of CFRP improves reliability somewhat because the strength of CFRP laminates has a lower coefficient of variation than steel or concrete. However, the brittle nature of CFRP laminates necessitates a reliability index that is greater than that generally implied in the AASHTO LRFD for 1998. This leads to a lower resistance factor than is currently accepted for reinforced concrete sections in flexure.