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 Nicknamed the silver bridge due to the aluminium paint used
 Eye bar suspension bridge – relatively new concept
 On the 5 /12/1967 the bridge collapsed during rush hour traffic
 Bridge “disappeared”- only took one minute to fall
 46 killed and 9 injured
 Memorial bridge built…… as a cantilever structure.

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 Eye-bar chain suspension bridge
 Eye bars were not redundant-unusual –links only composed of two bars each
 Heat rolled carbon steel used – twice tensile strength of common mild steel
 Suspension bridge supported by two rocker towers
 Rocker towers supported by eye-bar connection

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 Catastrophic failure-one minor flaw
 Combination of stress-cracking-corrosion
 Subjected to tensile stress in a corrosive environment
 Metal parts with severe SCC can appear bright and shiny – filled with microscopic cracks – undetected prior to failure
 Freezing conditions-member susceptible to brittle fracture
 Combination of high loading + reduced toughness of steel caused brittle failure

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 Failure of eye-bar – separation from pin-asymmetric load on pin caused twist-single eye-bar vibrated off pin
 Rocker tower now destabilised-toppled
 Bridge deck twisted- pulling other rocker tower down
 Complete structural collapse

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 Attention focused on older bridges built in same fashion
 One upstream of silver bridge and one in Brazil – built by same company-both immediately closed
 Point Pleasant disaster jumpstarted bridge safetynational bridge inspection standards introduced
 Quality assurance-quality level of bridge – how its designed for loading

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 Every bridge now inspected every 2 years
 Over 1,000,000 bridges in America- all checked in accordance to new guidelines
 Similarly designed bridges –replaced with new modern bridges
 Quality control- quality of inspection and loading-
2 nd check

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 ALWAYS include some type of redundancy- safety net for underestimated loads
 All structures should be designed so that all members can be easily inspected + maintained
 Designed with future in mind
 Increase in weight of car – new models
 Increase in traffic – threefold

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 Thank you