“Best of IBC” Webinar Series

The Best of IBC Webinar Series is a great way to preview the high quality technical content presented at the International Bridge Conference®.

Attendees can earn 1 pdh credit!

Virtual webinars are FREE to attend, but registration is required for pdh certification.

Topic: Rehabilitation, Part 1

IBC 21-14: Partial Steel Girder Replacement Due to Repeated Impact Damage and Use of Instrumentation to Monitor Effectiveness of Repair
Laura Magoon, P.E. and Christopher Kijak, P.E., RK&K, Baltimore, MD; David Barrett, Modjeski and Masters, Inc, Mechanicsburg, PA; Tekeste Amare, P.E., Maryland Transportation Authority, Baltimore, MD

The exterior steel girder of a 2-span continuous unit on a bridge over I-695 suffered repeated over-height vehicle impact damage. Heat straightening was ruled out and an alternate repair was provided to replace a portion of the damaged girder with a shallower section to provide additional clearance. Instrumentation indicated some permanent redistribution of the dead loads, with the live load properly distributed. This topic covers repair procedures and lessons learned to ensure proper load distribution.

IBC 21-18: Innovative Design Applications: 31st Street NW Bridge over C&O Canal, Washington, DC
Bradford Shaffer, Jason Bortz, Thomas Trapnell, and Elliott Mandell, AECOM, Arlington, VA; Mark Clabaugh, District DOT, Washington, DC

Replacement of 31st Street NW Bridge over the C&O Canal in Historic Georgetown had a multitude of unique constraints and stakeholder expectations as well as unknown challenges that were discovered during construction. This single span steel girder bridge on integral abutments was the 3rd bridge to span this location over the last 150 years.

The existing structure was supported by abutments founded on the historic canal walls of the C&O Canal, and a cast iron pier. Due to the age of the existing structure and canal, as-built information was minimal and an assessment determined the pier was no longer structurally viable; however, the substructure units were determined to be historically significant and required to be maintained in their current location. Preserving the historic elements required a single span structure, with the new abutments placed behind the canal walls and the rehabilitated pier serving as an architectural element only.

While designing a single 51’ span steel girder bridge is not typically challenging, the structural depth was severely restricted to 26” to maintain both the vertical clearance required below for safe passage of the tourist barge below and the vertical profile of the roadway. 31st Street is also a major utility corridor which required that 49 utility lines be maintained in place, most with uninterrupted service, as part of the bridge replacement.

Findings during construction led to value engineering using micropiles for the foundations as well as revising the deck to lightweight concrete to accommodate changes in construction staging and schedule.