1.  Point Pleasant Bridge

2.   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. Introduction

3.   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 Design

4.   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 Failure

5.   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 Failure

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7.   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 safety- national bridge inspection standards introduced  Quality assurance-quality level of bridge – how its designed for loading Aftermath

8.   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 Aftermath

9.   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 Lessons Learnt

10.   Thank you