Managing Florida's fracture critical bridges - phases 1 and 2 : final report.

Final reportPDFTech ReportBDV29-977-17Before and after studiesBox girder bridgesCrackingEvaluation and assessmentField testsFinite element methodFracture mechanicsSteel bridgesUnited StatesFloridaFlorida. Dept. of Transportation. Research CenterPham, HuyGull, Jawad H.Mohammadi, AlirezaAzizinamini, AtorodFlorida International University. Dept. of Civil and Environmental EngineeringFlorida. Dept. of TransportationUS Transportation CollectionBased on the definition given in the AASHTO LRFD Bridge Design Specifications, twin steel box-girder bridges areclassified as bridges with fracture critical members (FCMs), in which a failure of a tension member is expected tolead to a collapse of the bridge. However, a number of such bridges with either a partial or full-depth crack in onegirder have been reported and are still providing service without collapsing. The main objective of this researchproject is to understand the behavior of twin steel box-girder bridges and to develop methods for evaluating theirredundancy level in the event of the fracture of one tension member.The research project included an experimental investigation on a small-scale steel twin box-girder bridge, fieldtesting of a full-scale twin box-girder, analysis of existing research and design data, and an extensive amount ofnumerical analyses carried out on calibrated 3-D nonlinear finite element models. The results from this study providein-depth understanding of twin steel box-girder bridge behavior before and after a fracture in the tension memberoccurs. In addition to the experimentally verified finite element method, the report also proposes a simplified methodfor evaluating the performance of twin steel box-girder bridges and provides a list of important factors that couldcontrol the reserve capacity of the damaged bridge.A result of this project is the development of a comprehensive roadmap for assessing the redundancy of twin steelbox-girder bridges in which the elements of the roadmap are identified, and solutions for several of the steps areprovided. The development of solutions for remaining steps of the roadmap is proposed for a future research