4a6-1 disaster case study group 9 milford haven: steel box girder collapse alan hunt danielle...
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4A6-1 Disaster Case StudyGroup 9
Milford Haven: Steel Box Girder Collapse
Alan HuntAlan Hunt
Danielle PickettDanielle Pickett
Ed LawlorEd Lawlor
Michael CirilloMichael Cirillo
Milford Haven Bridge• Spans 820m across River Cleddau between Neyland
& Pembroke Dock, Wales.• Joint Consulting Engineers: Sir Alexander Gibb &
Partners and Freeman Cox & Partners• Contractor: A.E. Farr Ltd.• Construction began beginning 1969.• During 1970, steel box girder failed during placement
of final girder piece of 4th span.• 4 workers were killed and 5 others were seriously
injured.• Redesign carried out and was completed in 1975.
Bridge Design
• Primary structural members are steel box section girders.
• Greater 2nd Moment of Area than standard I-Beam ⇒better resistance to bending.
• Particularly important near a costal span (such as Milford Haven) with wind loadings.
• Girder of choice for large spans.
Bridge Construction• Consists of 48 box girder sections welded and bolted
together.• These box girders form a continuous section that behaves like
a beam.• During construction the welded box girders behave as a
cantilever until the pier opposite is reached.• Huge bending moments exist in termination of box section at
pier.
Collapse & Failure
• Collapse occurred due to buckling of the support diaphragm.
• Consequently, the distance between flanges decreased buckling of lower flange⇒
• Design Load = 5kN, Load at Failure = 9.7kN
Results and Effects
• BS153 were inadequate for construction of Steel Box Girders at that time.
• IDWR were created by the Merrison Committee, creating new rules for Steel Box Girder Design and Analysis.
• Foundation for the New British Standards, BS5400
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