Repair of Cracked Prestressed Concrete Girders, I-565, Huntsville, Alabama.

摘要

Wide cracks were discovered in prestressed concrete bridge girders shortly after their construction in Huntsville, Alabama. Previous investigations of these continuous-for-live-load girders revealed that the cracking resulted from restrained thermal deformations and inadequate reinforcement details, and that the cracking compromised the strength of the girder end regions. A wet-layup fiber-reinforced polymer (FRP) repair system was installed. To assess the efficacy of the FRP repair solution, load testing and finite-element analyses were conducted for pre- and post-repair conditions of two repaired spans. Post-repair testing included controlled truck loading as well as the monitoring of structural response to diurnal thermal conditions. Results indicate that the girders should be considered simply supported for conservative strength-limit-state design of the FRP repair system. FRP response to thermal conditions was accurately estimated using simplified analysis of restrained temperature gradient effects. A design procedure was developed for FRP repair of similar structures in accordance with AASHTO LRFD Bridge Design Specifications and the recommendations of ACI 440.2R-08. The reported procedure was formulated to provide the girder end regions with adequate strength for the combined effects of shear and flexure, as well as to provide adequate performance under daily truck loads and temperature variations.