Multiple roadways overlap in this image of the I-81 intersection. Thanks to a rapid response, the interchange was restored within seven months of a devastating fire.

I-81 River Relief Route Emergency Design


In 2013, a tanker truck carrying 7,500 gallons of diesel fuel overturned on the I-81 northbound ramp to U.S. Route 22 in Harrisburg, and a massive fire shut down one of the busiest sections of the interstate.

Searing heat severely damaged the bridge, warping the metal guide rails and incinerating portions of the deck. At the request of the Pennsylvania Department of Transportation (PennDOT), Gannett Fleming immediately sent a team to the crash site to evaluate the structural stability of the overhead bridge.

Before the smoke had cleared, the team began analyzing the damage and determining how to remove the old bridge and design the replacement structure. As the original designers of the nearly 40-year-old bridge, our firm supplied the information needed to start the design process promptly. This immediate response aided in the rapid replacement of the overhead structure and rehabilitation of the ramp bridge, which helped PennDOT restore the entire interchange within seven months of the fire.

What We Did

Our structural engineering team conducted analysis of bridge elements based on the contractor’s proposed demolition sequence and calculated crane pick weights for each stage of the demolition. Due to the long lead time required to fabricate bearings, our structural engineers were asked to develop drawings for replacement bearings for both the ramp bridge and the U.S. Route 22/322 eastbound bridge.

Our firm also redesigned and detailed the cross girders for the new bridge, which included reviewing shop drawings for the refabrication of the steel superstructure. Additionally, we developed repair procedures for the Ramp B bridge following PennDOT’s forensic analysis of the steel superstructure.

Construction services included the review of a crane pad for the demolition of the remaining portion of the fire-damaged bridge and erection of the new superstructure. Our firm also developed construction drawings for the Ramp B structure and reviewed the:

  • Work platforms.
  • Formwork.
  • Demolition and erection analysis.
  • Crane pad.
  • Stay-in-place (SIP) bridge forms.
  • Strip seal dams.

Key Features

  • Structural analysis guided demolition of damaged overhead bridge.
  • Replacement bearing and cross girder redesign provided effective superstructure support.
  • Repair procedures developed for restoration of Ramp B bridge.

Awards & Recognition

  • Grand Conceptor Award, 2015, American Council of Engineering Companies (ACEC) of Pennsylvania, Diamond Awards for Engineering Excellence
  • National Recognition, 2015, American Council of Engineering Companies, Engineering Excellence Awards


  • Reopened I-81, serving 85,000 motorists daily, within days.
  • Rapid response enabled quick start to demolition and design.
  • Restored severely damaged interchange within seven months.


Pennsylvania Department of Transportation


Harrisburg, Pa.


Analysis, Design, Rehabilitation, and New Construction

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