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Mothman

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Christian Kielbasa
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« Reply #30 on: June 05, 2009, 01:32:43 pm »

Silver Bridge Rocker towers
The towers were "rocker" towers. These allow the bridge to respond to various live loads by a slight tipping of the supporting towers which were parted at the deck level, rather than passing the suspension chain over a lubricated or tipping saddle or by stressing the towers in bending. Thus the towers required the chain on both sides for their support, so failure of any one link on either side, in any of the three chain spans  would result in the complete failure of the entire bridge.

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Christian Kielbasa
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« Reply #31 on: June 05, 2009, 01:32:57 pm »

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Christian Kielbasa
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« Reply #32 on: June 05, 2009, 01:33:14 pm »

Silver Bridge Design loads
At the time of its construction, a typical family automobile would be the Ford Model T, with a weight of about 1,500 lb (680 kg). The maximum permitted truck gross weight was about 20,000 lb (9,072 kg). At the time of the collapse, a typical family automobile weighed about 4,000 lb (1,814 kg) and the large truck limit was 60,000 lb (27,216 kg) or more. Bumper-to-bumper traffic jams were also much more common - occurring several times a day, five days each week.

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Christian Kielbasa
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« Reply #33 on: June 05, 2009, 01:33:30 pm »

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Christian Kielbasa
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« Reply #34 on: June 05, 2009, 01:34:00 pm »

The Human Loss
At right is a list of those that dies from the collapse of the Silver Bridge that fateful night in Point Pleasant.
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Christian Kielbasa
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« Reply #35 on: June 05, 2009, 01:34:18 pm »

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Christian Kielbasa
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« Reply #36 on: June 05, 2009, 01:35:04 pm »

Wreckage Analysis Of The Fallen Silver Bridge
The bridge failure was found to be due to a defect in a single link, eyebar 330, on the north of the Ohio subsidiary chain, the first link below the top of the Ohio tower. A small crack was formed through fretting wear at the bearing, and grew through internal corrosion, a problem known as stress corrosion cracking. The crack was only about 0.1 inch deep when it went critical, and it broke in a brittle fashion. Growth of the crack was probably exacerbated by residual stress in the eyebar created during manufacture. When the lower side of the eyebar failed, all the load was transferred to the other side of the eyebar, which then failed by ductile overload. The joint was now only held together by three eyebars, and another slipped off the pin at the centre of the bearing, so the chain was completely severed. Collapse of the entire structure was inevitable since all parts of a suspension bridge are in equilibrium with one another. Witnesses afterward estimated that it took only about a minute for the whole bridge to disappear.

See the videos above for more detail on the failure modes of the Silver Bridge.

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Christian Kielbasa
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« Reply #37 on: June 05, 2009, 01:35:26 pm »

Inspection Difficulties
"Inspection prior to construction would not have been able to notice the miniature crack. ...the only way to detect the fracture would have been to disassemble the eye-bar. The technology used for inspection at the time was not capable of detecting such cracks."

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Christian Kielbasa
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« Reply #38 on: June 05, 2009, 01:35:46 pm »

Aftermath Of The Disaster
The collapse focused much needed attention on the condition of older bridges, leading to intensified inspection protocols and numerous eventual replacements. There were only two other bridges built to a similar design, one upstream at St. Marys, West Virginia and a longer bridge at Florianópolis, Brazil. They were both closed immediately, and the St. Marys bridge was demolished in 1971. Explosive charges were placed on the main chains, and fired to remove the structure, although
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Christian Kielbasa
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« Reply #39 on: June 05, 2009, 01:35:58 pm »

a small truss bridge was kept to allow access to an island in the river. The Brazilian bridge remains, but is closed to traffic. It was built to a higher safety factor. Modern non-destructive testing methods allow some of the older bridges to remain in service where they are located on lightly traveled roads, while most heavily used bridges of this type have been replaced with modern bridges of various types, and as an extra benefit containing additional lanes.

The new bridge that replaced the Silver Bridge was named the "Silver Memorial Bridge".

A scale model of the original Silver Bridge can be seen at the Point Pleasant River Museum, and there is an archive of literature kept there for public inspection. The museum also has an eyebar assembly from the original bridge on display on the lower ground floor.

The tragedy led to new legislation to ensure that older bridges were regularly inspected and maintained, although it did not prevent the collapse of the Mianus river bridge in 1983 (when 3 drivers died), and the Minneapolis bridge disaster in 2007, when 13 drivers died.
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Christian Kielbasa
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« Reply #40 on: June 05, 2009, 01:36:48 pm »

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« Reply #41 on: June 05, 2009, 01:37:13 pm »

The Silver Bridge In Popular Culture
Ohio University English professor Jack Matthews wrote a novella, Beyond the Bridge, written as the diary of an imaginary survivor of the disaster starting a new life as a dishwasher in a tiny West Virginia town.

Urban Legends About The Silver Bridge
Odd events were purported in the area over several months before the collapse, including appearances of a "Mothman." Originally, the story of Mothman was connected to the disturbance of the grave of Chief Cornstalk when the county courthouse was expanded. Later, a 1975 book The Mothman
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Christian Kielbasa
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« Reply #42 on: June 05, 2009, 01:37:48 pm »

Prophecies by John A. Keel would connect the Mothman to aliens. The 2002 "based on a true story" movie of the same name is not set in the 1960s, but in the present day. Point Pleasant has a Mothman Museum and holds an annual Mothman Festival.

http://www.mothmen.us/silver-bridge.htm
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Christian Kielbasa
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« Reply #43 on: June 05, 2009, 11:34:33 pm »



Silver Bridge when completed in 1928
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Christian Kielbasa
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« Reply #44 on: June 05, 2009, 11:35:08 pm »



As it was
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