 It is a cold December evening in 1967 and rush hour traffic is making its way across a bridge over the Ohio River. The bridge has been here for 39 years and has served the area as it carries US Route 35. At 1700 hours the bridge catastrophically failed sending traffic into the river below. The event would cast doubt on bridges in the country and show the vital need for regular inspections. Today we're looking at the Silver Bridge Collapse and I'll give you my rating at the end of the video. Let's see what you think. America in the 1920s was feeling like it was getting smaller as more families purchased cars for traveling around the country. As such many different infrastructure projects are begun to make the nations roads more convenient for people and goods to transport across the country. One of these projects was approved in 1926 to join up Ohio and West Virginia. Construction would begin on a new bridge across the Ohio River in May 1927 and will welcome its first vehicles just one year later. The bridge would gain the nickname The Gateway to the South and its shiny aluminium paint lent the point pleasant bridge its other name the Silver Bridge. The bridge's total length was 1,750 feet and this included the main span and its two approaches either end. The main suspended portion of the bridge was 700 foot long with two intermediate spans one at each end at 380 feet each. The bridge was designed by J.E. Greener Company and was built by Gallia County Ohio River Bridge Company but the finished bridge was not the same as the original plans. Originally when the bridge was envisioned it was to have a more conventional wire cable arrangement but a cheaper I bar chain setup was employed instead. The bridge used a methodology of no redundancy but high strength in its chain links. Instead of having multiple weaker steel links the Silver Bridge would have only a two link bar setup. In a multi link setup there are several redundancies so if one link breaks the others will take up the stress but if one of the links fail in a two bar setup the whole section is reliant on the other link holding the entire load. This is all very well as it reduces weight in comparison to a conventional I bar chain bridge and should work if the links are properly fabricated and the maximum load on the bridge is not exceeded. Which must have felt unlikely in the fairly clear roads of the 1920s inhabited by Model T Ford's and small truck but this wouldn't always be the story as the USA embraced the automobile. The I bars were around 2 inches thick and 12 inches wide. These varied in length around 45 to 55 feet depending on where they were employed on the bridge. To connect the bars 11 inch diameter pins connected the links for the eyes at the ends. These chains would make up the upper cord to a Warren type stiffening truss in the seven panels of each side span and the 12 panels of the main center span. The towers employed were a 313 foot tall rocker type which was designed to move with the various loads on the bridge. The towers required the two link chains on both sides for their support. Failure in any link on either side of the towers in any of the three chain spans would result in complete failure of the entire bridge. When completed the bridge had a deck consisting of wood planking covered by rock asphalt but in the 1940s was replaced by concrete filled metal grid. In 1941 the privately owned silver bridge was bought by the state for $1.04 million. Between its original opening and 1941 a number of inspections were undertaken on the structure and after state ownership the bridge was checked over in 1959, 63, 64, 65 and 67. Some repairs during the 1965 inspection were highlighted at a cost of $30,000. But these inspections were only visible and the design of the bridge having no redundancy meant that no part of the essential chain could be dismantled for inspection. So basically if you couldn't see any defects in your line of sight then you couldn't repair them and at the time there wasn't really any non-destructive forms of inspection available and this leads us to December the 15th 1967. Rochelle traffic mounts up on the silver bridge on the evening of the 15th of December 1967. This is not unique as it forms part of a vital arterial route in the area. Few minutes before 5 p.m a groaning could be heard coming from the bridge shortly after a loud gunshot like sound shot out across the structure. Within seconds the entire bridge plunged into the Ohio River as described by one eyewitness as folding like a deck of cards. 32 cars disappeared from the bridge and along with them 64 people. Many witnesses from both sides of the bridge rushed to try and assist the victims. Several were pulled from the horrifically cold Ohio River but many more were not and a few of the cars now floating on the river were pushed downstream by the flow of water. Emergency workers arrived on the scene shortly after the collapse and along with passersby continued to rescue efforts. 46 of the people sent into the river would die with two never to be recovered. At around 4 p.m the next day recovery barges reached the fallen bridge began to try and retrieve the wreckage of vehicles and with the assistance of divers find the bodies of the victims. After as many victims were discovered as possible the next stage of recovery was the bridge itself. The recovered portions of the failed bridge were placed on the left bank of the river at Henderson West Virginia about one and a half miles below the bridge site on property leased by the state road commission. The removal of the wreckage was completed on the evening of the 31st of December but did not include an estimated amount of 154 tons from the Ohio span which rested on dry ground. With the bridge now recovered investigators set out to find the cause of the collapse as it was seemingly a healthy structure. Well the results would reveal a horrifyingly simple flaw of just a few millimeters. Due to lack of an obvious sign of failure various leads were pursued and one of them was the risk of a low flying fighter plane. You see multiple reports from residents nearby had claimed hearing a boom shortly before the collapse however after investigators checked nearby buildings for over-pressure damage this theory was soon ruled out. It was also confirmed by the government that no nearby military installations had such type of aircraft. Hello this is John from the future from when I originally recorded this script at this point I need to address the other theory Mothman. In his 1970 book Operation Trojan Horse and in his 1975 book The Mothman Prophecies author John Kill linked the silver bridge collapse to alleged sightings of the Mothman but again like the aircraft theory this is rather unlikely and the actual cause would be in my opinion far more worrying a microscopic crack. Needless to say investigators focus back on the bridge itself after extensive studying of the wreckage and the i-bar links a likely cause was discovered but this theory wouldn't be confirmed until a 1971 safety board determination and after extensive laboratory testing the culprit was pinpointed. I-bar 330 at Joint C13N of the North I-bar Dispension Chain was discovered to have a crack but looked to have progressively increased it was thought that the crack was present during manufacture albeit minute and practically undetectable to the naked eye. Over time this cracks have come to stress corrosion this is the formation of brittle cracks in a normally sound material through the simultaneous action of tensile stress and a corrosive environment. Over the near 40 year life of the bridge this crack continued until a point of no return. The defect was further hindered from being discovered due to the setup of the non-redundant I-bar which meant that dismantling for inspection was unfeasible. At the time of the bridge's construction West Virginia law prohibited the operation of any vehicle gross weight including its load more than 20,000 pounds. Over the years this law would change resulting in this weight almost tripling. The bridge's deterioration was sped up by these increased loads the legacy of the bridge resulted in more stringent inspections and a reevaluation of bridge design and the risks of stress corrosion. Lyndon B Johnson funded an investigation into the nation's bridges and it was discovered that around 1100 were designed for model T Ford size traffic. Bridge designers would factor in future predicted loads in newer constructions and a move away from non-redundant designs hoped to improve design safety. The bridge would be temporarily replaced by a ferry service but would eventually be rebuilt and named the Silver Memorial Bridge in 1969. And now for my disaster rating. I'm going to put the Silver Bridge here 7 on my scale and 8 on my legacy scale. Do you agree? Let me know in the comments below. This video is a plain difficult production. All videos on the channel are creative commons attribution share like licensed. Plain difficult videos are produced by me John and they're currently sunny southeast in Corn of London UK. Help the channel grow by liking commenting and subscribing and check out my Twitter for all sorts of odds and sods. 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