The 2,000-ft-long, 301-ft-high Kinzua Viaduct was the longest and tallest railroad viaduct in the world when built in 1882. After a 2002 inspection revealed deterioration to the tower columns and anchor system, an emergency rehabilitation project began. But with only 50% of structure repairs completed, an F1 tornado struck the viaduct in July 2003 and the unrepaired portions collapsed. Officials championed the restoration of the damaged southern remnants, converting it to an observation deck for visitors.
The original anchor system consisted of a single wrought-iron anchor bolt per column, grouted into a masonry stone pier. Investigators identified this as the main cause of failure during the tornado. The team's solution comprised offset brackets to connect four anchor bolts per column, two primary rock anchor bolts extending 70 feet into bedrock and two shorter bolts grouted into the concrete-jacketed masonry stone piers.
The upper 35-ft-high portion of the 225-ft-high Tower #15 was damaged during the tornado. The upper sections of the columns and the cap beam were replaced with identical fabrications based on original 1899 plans secured from the Smithsonian Institution.
With widths in excess of 100 ft at the base, the tallest towers originally had roller bearings installed beneath the base plates to relieve the temperature stress of the substantial towers. After decades of minimal cleaning and lubrication, the 130-year-old assemblies had completely seized and partially disintegrated. Repairs involved jacking towers that were over 200 ft high and installing corrosion resistant, self-lubricating expansion plates.
The site is in northern Pennsylvania's rough terrain, where subzero temperatures, high winds, heavy lake-effect snows, roaming bears and harsh topography are common. A rugged trail was the crew's only access to the base of the structure, where the terrain grade averages 15% and in some locations exceeded 70%.
Despite the difficult site conditions, the project completed with no OSHA-recordable incidents and no lost time.
Kinzua Sky Walk Mount Jewett, Pa Key Players
General Contractor: J.D. Eckman, Inc., Atglen, Pa.
Owner: Pennsylvania Department of Conservation & Natural Resources, Harrisburg, Pa.
Lead Design: Herbert, Rowland & Grubic, Inc., Harrisburg, Pa.
Structural Engineer: Herbert, Rowland & Grubic, Inc., Harrisburg, Pa.
Civil Engineer: Herbert, Rowland & Grubic, Inc., Harrisburg, Pa.
Submitted by Herbert, Rowland & Grubic, Inc.