1. Group 7

2.  Designed by Sir Thomas Bouch  Completed in February 1878  Longest spanning bridge in the world at the time ( 2 miles)  Built to span the Firth of Tay (Scotland)  Cost over £300,000  Construction took 6 years

4.  On the 28 th December 1879 – strong gale force storm.  Bridge collapsed while carrying a train  75 lives lost.  Worst structural collapse in British history (excluding war actions).  There are 3 theories to the cause of the collapse.

5.  Strong, gusty wind – force 10/11 on the Beaufort scale.  Wind blew at right angles to the line of the bridge.  Wind caused windward bolts to lift, putting extra pressure on ties.  Ties in piers snapped resulting in the lateral stiffness of the piers to reduced by a factor of 3.

6.  Bridge and train began to sway violently.  Columns on upwind side failed in tension.  Columns on downwind side failed in compression.

8.  Workers on bridge reported oscillating of piers when trains passed.  Photos show crack lines on iron lugs  Implication that lugs failed by fatigue rather than overstressing  Storm only served to “tip over the edge”  Structure would have failed soon either way

9.  Train hit a kink in the track  Crashed into the structure of the bridge  Force strong enough to shatter iron lugs  lugs were connecting main structural  Bridge left defenceless to oncoming winds  lugs were not to required strength standard  Trains exceeding speed limits by 15mph  A girder was dropped & reused causing the kink

10. Inquiry Report  Inquiry report set up after collapse  Found the maintenance & supervision of the bridge after construction was unsatisfactory  Report Blamed Bouch for the collapse ( wind loading was not taken into consideration )  Strong winds and bad cross bracing was the most likely cause of collapse

11.  Cast Iron members changed to steel  Lugs were to tight, some only burnt on (better design of connections)  Never reuse steel which has been bent badly  Always consult standards for wind loading requirements Solutions and lessons learnt

12.  We concluded that the collapse could have been caused by a combination of all 3 theories.  The lateral restrained members were never designed to resist high winds.  Fatigue of structure was unsatisfactory ( only lasted a year)