Failure of Tay Bridge

7/27/2019 Failure of Tay Bridge

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TECHNICAL INFORMATION • The original Tay Rail Bridge was

constructed in the 19th century by railway engineer Thomas Bouch at Dundee.

• Thomas Bouch completed the bridge in

February of 1878

• The Tay bridge was nearly two miles long,at the time was the longest bridge in the

world.

• Tay bridge was supported on cast iron columnsstrengthened with wrought iron struts and ties.

It carried a single rail track.

http://en.wikipedia.org/wiki/Railway

http://en.wikipedia.org/wiki/Engineer

http://en.wikipedia.org/wiki/Thomas_Bouch

http://en.wikipedia.org/wiki/Thomas_Bouch

http://en.wikipedia.org/wiki/Engineer

http://en.wikipedia.org/wiki/Railway



• The bridge was 85 spans wide with 13

navigation spans which were higher and largerthan the others.

• Of the 13 navigation spans, eleven were 245

feet and two were 227 feet.

• 72 of these spans were supported on deckspans,

the remaining 13 navigation spans were through

girders. These " high gir ders" were 27 feet high

with an 88 ft clearance above the high water

mark.





http://en.wikipedia.org/wiki/Image:Tayrailbridge.jpg



However, as there were no codes of practice at the

time, structural design was often based onexperience rather than accurate calculation.

Therefore " the br idge was bui l t with only two things in mind - Speed of construction and cost. This meant

that aspects such as safety and durabil i ty were not

considered as carefully." .





The High Girders section were mounted with the

box between the piers containing the track within to

provide clearance for vessels on the Tay.

A combination of the high pressure of wind on that

section containing the train and the poor quality of

the design and materials used were blamed in a

enquiry.

REASONS FOR FAILURE

At 7:15 p.m. on the stormy night of 28 December 1879, the

central spans of the Tay bridge collapsed into the Firth of Tay

at Dundee. A train including six carriages and 75 people fell

into the cold water below. At the time, a gale estimated at

force 10 to 11 was blowing down the Tay estuary at right

angles to the bridge.



Lateral oscillations were induced in the highgirders section of the bridge by trains passing

over a slight misalignment in the track.

The amplitude of these oscillations grew with

time, because joints holding the bridge together

were defective, and this in turn resulted in

fatigue cracks being induced in the cast iron

lugs, which reached criticality on the night of

Some of the Iron from this foundry was very poor quality.

Also during its construction one high girder on a barge

was lost to storms for a night and another was droppedonto the sea-bed whilst being lifted into place. These

sections were still used.



Figure shows the northern end of thecollapsed section, the two rails wrenched

towards the east in the direction of fall.



This view demonstrates the collapse duringthe great storm of 1879, which removed 13

spans of 245 feet each from thesuperstructure of the Tay Rail Bridge.



The stresses imposed by the falling columns have wrenchedtwo substantial courses of masonry from the underlying pier.Flanged joints on the columns have failed and the decking of the bridge, together with other parts of the structure, hasdisappeared into the icy waters of the Tay.



The inherent weaknesses of the flanged joints areclearly illustrated by the clean break above thesecond line of columns on the pier in the middledistance.

















Collapse Mechanism

1. When the train reached the high girders there was a

particularly strong gust.2. This increased the overturning force enough to

cause the windward column base to lift.

3. The diagonal ties begin to fail in a brittle mode

starting at the second level and possibly above (but

not at the bottom level).



4.This weakens the second level causing failure of

the bolted connections in the columns at that level.Simultaneously the bracing failure extends upwards.

The column support on the leeward side becomes

ineffective. That side starts to drop and the whole pier

starts to rotate about the second level.

5.As it falls there is a kickback on the first level

causing it to be demolished but retaining most of the

wreckage on top of the foundation.





TAY BRIDGE TODAY



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Failure of Tay Bridge