Kinzua Bridge (2003) Pennsylvania, USA
The original Kinzua Bridge of 1882 was the brainchild of General Thomas L. Kane a decorated veteran of the American Civil War. Kane saw the opportunity of supplying rapidly industrialising America with coal and timber from the richly endowed Pennsylvanian highlands and bridging the Kinzua Valley was the most efficient way to accomplish it. The 626 metre iron trestle viaduct, soaring over 91 metres above the valley floor was completed in 1882, the deck itself taking a mere four months to construct.
Kane’s viaduct was a celebrated affair, lauded as the 8th wonder of the world and a record breaker in length and height. A project of famed bridge designer Octave Chanute, it carried a single track working railroad, supported by 20 towers of iron, in turn supported by massive sandstone piers. It became a tourist attraction almost immediately.
The viaduct survived a train crash in 1889, yet a rebuild was mooted as early as 1890 as it could not carry the ever heavier loads. It was deconstructed tower by tower and in 1900 rail traffic began to cross the new, steel Kinzua Viaduct and continued to do so until it was closed to commercial traffic in 1959. The land was shortly after acquired for a state park.
It was as a tourist attraction that the Kinzua Bridge survived, visitors crossing by foot or by excursion train, until 2002 when it was closed for safety reasons - it was rusted and bent in parts and potentially unstable in high winds. On the July 21st, 2003 a tornado tore through the valley and destroyed the bridge, which had been cleared of workers endeavouring to stabilise the structure. There were no fatalities or injuries.
The Board of Inquiry report found that the tornado, at speeds of up to 150 k.p.h., had hit the bridge twice, first from the east, then from the south. The bridge had been built to withstand the prevailing westerly winds and the fixed bearings on the western side of the structure in effect acted as hinges in the toppling of the structure. In addition the bridge was suffering from age fatigue, the anchor bolts in particular had been reused from the original structure during the rebuild of 1900. The inquiry identified 4 distinct collapses, all taking place in a 30 second time period. 11 of the 20 towers were toppled.
On September 15th, 2011 the Kinzua Bridge was reborn as the Kinzua Sky Walk, following a multi-million dollar investment programme. Utilising the remaining towers a 183 metre pedestrian walkway stretches out almost 69 metres above the valley, featuring a partial glass floor, octagonal viewing platform and original rail tracks.