Group 7

Tay Bridge
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Completed in February 1878
Designed by Thomas Bouch
The Span was 2 miles(3,264 meters )
Longest spanning bridge in the world at time of completion
Took six years to build
Cost in excess of £300,000

Collapse
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In 1879 there was a great storm with gale force winds topping 70mph
The Tay Bridge collapsed in the gale
A train was crossing the bridge at the time resulting in death of 75 people

Mode Of Collapse

Mode Of Collapse

Mode Of Collapse

Mode Of Collapse

Mode Of Collapse

Aftermath
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An inquiry team was set up
They delivered their report in six months

Inquiry Report
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The supervision of the bridge after its completion was unsatisfactory
Trains were frequently run through the high girder at much higher speeds than at the recommended rate of 25 mph

Inquiry Report
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The fall of the bridge was probably due to the giving way of the crossbracing and its fastenings
The imperfections in the columns might also have contributed to the same result
The report blamed Bouch for the collapse

Other Theories
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The train could have come off the rails assisting the bridge to collapse
Dynamic effects and fatigue could have been a contributory factor although they are weakly supported by evidence

Conclusion
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From this information it appears the bridge collapse was due to the fact the cross-bracing wasn’t strong enough to resist the lateral loads from the gale force winds

Lessons Learnt
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Bouch’s bridges were examined and reinforced
Designs using cast iron was barred
Steel was approved for future use in bridge design
A Royal commission on wind pressure on railway structures was set up in 1881

References
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 http://www.open2.net/forensic_engi neering www.bradford.ac.uk/acad/civeng/ marketing/ civeng/failtay1.htm