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Webinar: System Redundancy of Steel Twin Tub Girder Bridges


Webinar: System Redundancy of Steel Twin Tub Girder Bridges

The webinar will take place May 11, 2021 at 12:00 PM CST for 1 PDH.

>> Register now for this ASCE Texas Section’s Technical Webinar.

A common bridge type historically assumed to include fracture critical members (FCMs), based on a simplistic load-path redundancy assessment, is the steel twin-tub girder bridge. These bridges consist of two steel box girders, frequently trapezoidal shaped, composite with a concrete deck, and are very effective for curved ramps and connectors in multi-level interchanges. FCMs must be fabricated according to American Welding Society (AWS) D1.5 Fracture Control Plan, which requires more testing, certification, and base metal requirements during fabrication. They also require hands-on inspections every two years or less during the service life of the bridge. Oftentimes, these inspections are performed at night, on roadways with high traffic volumes, which require costly traffic control and lane closures, exposing the public to reduced safety inherent with traffic control.

Thanks to recent research, a simplified method for evaluating system redundancy in two-tub girder span bridges has been added to the state’s bridge policy and accepted by the Federal Highway Administration (FHWA). The TxDOT Bridge Design Manual-LRFD now presents a LRFD based methodology to design new steel twin tub girder spans to demonstrate that they possess adequate redundancy, so that members gain a system redundant member (SRM) designation instead of a FCM designation. This presentation will discuss the background and definition of system redundant members (SRMs), redundancy case studies, research, implementation, and future plans.


Jamie F. Farris PE is the Deputy Director of the Bridge Division at Texas Department of Transportation. In her role, she assists in overseeing operations that include planning assistance, geotechnical and structural plan preparation, construction and maintenance assistance, safety inspection and PS&E review. Ms. Farris graduated from the University of Texas at Austin with a BS in Architectural Engineering and an MS in Civil Engineering with an emphasis in Structures. Ms. Farris has served as the past Chair of the Texas Steel Quality Council and is the committee Chair of the Transportation Research Board (TRB) Steel Bridges Committee AKB20. She is also a member of the AASHTO Committee on Bridges and Structures (COBS), where she serves as a technical committee member on T-10 Concrete Design and T-14 Structural Steel Design committees.

With registration discounts for Section members, government employees, and students, don’t wait, register now!