1. Milford Haven Bridge Collapse Cathal Kennedy Terence Meade Sara Farivarz Padraig O’Rourke

2. Contents  Introduction  Milford Haven Bridge  The Collapse  Results  Conclusion

3. Introduction  Box Girders: used for large 2 nd moment of area & torsional resistance used for large 2 nd moment of area & torsional resistance  Hard to analyse, however  One of 4 similar bridges that failed from 1969 - 1971

4. Milford Haven Bridge  Box Girder design  Consisted of 7 separate spans from 77m to 312m in length  Built by being cantilevered out from piers  Sections then welded or bolted to end

5. The Collapse  Occurred when launching deck section across  Stresses during construction are very different and often larger than when the bridge is completed

6. Continued  occurred during launching a pre- assembled deck section towards the second pier.  subjected to bending moments and vertical shear forces.  buckling of diaphragm lead to buckling of lower flange.  Load before failure 9700kN

7. Results  Committee of Inquiry concluded that BS153 was inadequate  Merrison committee sets rules which become the basis for BS5400  West Gate Bridge strengthened but collapsed 2 months after killing 32.

8. Conclusion  Ultimately caused by human error – failure to anticipate effects during construction  Highlights need for engineers to fully understand principles behind construction