High torsional rigidity and attractive aesthetics in construction of twin-tub girder bridges make them preferable for the design of curved bridges. However, according to the concepts associated with the term “Fracture Critical (FC)” that are in place today, all two-girder bridges are classified as having FC members (FCMs) due to their perceived lack of load path redundancy. For a steel bridge with FCMs, the fracture of any of the FCMs is assumed to result in complete catastrophic failure or significant loss of serviceability; hence, every two years twin-tub girder bridges undergo very expensive hands-on field inspections.

This report presents a simplified approach to ensure newly designed twin-tub girder bridges will meet all the requirements defined in the 2018 AASHTO Guide Specifications without performing in-depth FEA. AASHTO-ready proposed specifications are included in Appendix A. It is anticipated that these provisions could be incorporated into the AASHTO LRFD BDS as a new article 6.6.3 Special Provisions for Twin Tub Girder Bridges.


twin tub girder bridge, fracture critical member, steel bridge

Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

Date of this Version