Lecture03 - Bridge Disasters

Lecture 03

Bridge Disasters

Natural Events:

- Earthquakes- Wind

Hurricane winds overturned this 19th century railroad truss bridge.

Structural performance:

I-5 & ANTELOPE VALLEY FREEWAY DAMAGE

Aerial view of the collapsed freeway interchange between I-5 and theAntelope Valley Freeway (State 14). (photo: Kerry Sieh)

I-14 South to I-5 South Connector - Newhall Pass

I-5 South to I-14 NorthConnector - NewhallPass.


I10 Freeway Los Angeles


SANTA MONICA FREEWAY DAMAGEPart of Interstate 10 west of downtown Los Angeles collapsed in the

shaking of the Northridge earthquake. This section of the Santa MonicaFreeway had been built across drained wetlands, which is probably whyit experienced seismic failure. The damage here was repaired withinthree months. (photo: Kerry Sieh)


SIMI VALLEY FREEWAY DAMAGE

Buckling of freeway support columns under the Simi Valley Freeway atthe north end of the San Fernando Valley. This buckling shows thestructural failure produced by high vertical acceleration. (photo: Ta-Liang Teng)

Man-induced Disasters

Truck collapses Interstate in Nebraska.

Truck collapses Inter-state in Nebraska.

Tacoma-Narrows Bridge

• Combination of steel plate girder approach spans and a suspension bridge for the main span..

• Total length was 5,939 feet, with 2 towers each 420 feet tall.

• The center span was 2,800 feet.

• Cables secured at both ends, at a distance of 1,100 ft from eachtower.

• The bridge was opened to the public on 1 July, 1940.

Attempts to improve the bridge gallopingbefore its collapse:

• Tie-down cables placed neareach end and attached to thedeck.

• Installation of inclined stayedcables in order to reinforce theconnection of the center span’smain cables to the stiffeninggirders.

• Use of untuned dynamicdamper, consisting of a pistonin a cylinder

• Cables snapped during a windstormon October 4th, 1940.

• Did not work due to installationerrors.

• Did not work due to installationerrors

Procedures: Results:

Causes of Tacoma Failure:

• While it could safely resist all static forces, the wind causedextreme undulations which caused the bridge’s failure.

• No one realized that Tacoma’s exceptional flexibilitycoupled with its inability to absorb dynamic forces wouldmake the wild oscillations which destroyed it possible.

• Initially, vertical oscillations were caused by the force of thewind and caused no structural damage.

• The failure of cable band on the north end, which wasconnected to the center ties, probably started the twistingmotion of the bridge. The twisting motion caused highstresses throughout the bridge, which lead to the failure of the suspenders and collapse of the main span.

This photograph shows the twisting motion of the center span just prior to failure.

Collapse:

The nature and severity of the torsional movement is revealed in thispicture taken from the Tacoma end of the suspension span. Whenthe twisting motion was at the maximum, elevation of the sidewalk atthe right was 28 feet (8.5m) higher than the sidewalk at the left.

Collapse:

This photograph actually caught the first failure shortly before 11 o'clock,as the first concrete dropped out of the roadway. Also note bulges inthe stiffening girder near the far tower and also in the immediateforeground.

Collapse:

A few minutes after the first piece of concrete fell, this 600 foot section broke out of the suspension span, turning upside down as it crashed in Puget Sound. Notehow the floor assembly and the solid girders have been twisted and warped. Thesquare object in mid air (near the centre of the photograph) is a 25 foot (7.6m)section of concrete pavement.

Collapse:

This photograph shows the sag in the east span after the failure. Withthe centre span gone there was nothing to counter balance theweight of the side spans. The sag was 45 feet (13.7m). Also theimmense size of the anchorages is illustrated.

Collapse:

This picture was taken shortly after the failure. Note the nature of thetwists in the dangling remainder of the south stiffening girder and thetangled remains of the north stiffening girder.

Consequences:

a) the center span diagonalties and their connections.

b) the slackening of the tiedue to twisting.

c) the frayed main cableafter failure. About600 (sic) wires are cut.

d) the diagonal ties after the failure.

Consequences:

This picture shows thebuckling of thesuspended floor systemnear the centre of theside spans. The top rightpicture shows thesuspender connectionsand the type of cablesused for this connection.

Consequences:

This picture shows thesize of the towersand the type of construction used. There is a slightbuckling of thetower as a result of the additional straincaused after thecentre spancollapsed. Thetowers were madeout of structuralcarbon steel.

Tay Bridge:

The disaster is one of the most famous bridge failures andto date it is still the worst structural engineering failure inthe British Isles.

Facts on Tay:

• Opened on May 31 1878 and at the time was the longest bridge inthe world.

• Designed by Thomas Bouch who was responsible for itsConstruction and Maintenance.

• Bridge was 2 miles long consisted of 85 spans, where 72 of thesespans were supported on deck spans, which carried a single railtrack.

Facts on the Tay

• The remaining 13navigation spans werecalled high girders. Thereclearance was 88ft abovethe high water mark

• The single track bridgewas a box constructionwith numerous boxsection legs up to 230ftapart.

Causes of Failure:

• The Court of Inquiry concluded that, "The fall of the bridge wasoccasioned by the insufficiency of the cross bracing and itsfastenings to sustain the force of the gale.“

• Train Theory, stated the train came of the track due to a kink inthe rails and uplift of the train attributed to aerodynamic forces.

• Dynamic Theory, stated that the dynamic effects caused thefatigue failure.

• The analysis suggested that the uplift of the windward columnwas a signif icant feature of the collapse mechanism.

• The strongest evidence to the bridge under designed for wind.

Process of Collapse

• When the train reached the highgirders there was a particularlystrong gust.

• This increased the overturningforce enough to cause thewindward column base to lift .

• The diagonal ties begin to fail ina brittle mode starting at thesecond level and possiblyabove (but not at the bottomlevel).

Process of Collapse

• This weakens the second levelcausing failure of the boltedconnections in the columns atthat level. Simultaneously thebracing failure extendsupwards. The column supporton the leeward side becomesineffective. That side starts todrop and the whole pier startsto rotate about the second level.

• As it falls there is a kickback onthe first level causing it to bedemolished but retaining mostof the wreckage on top of thefoundation.

The new Tay railroad bridge has been

built alongside the remains of Bouch's

bridge, providing a grim reminder.

Northridge Earthquake:

I5 South to I14 NorthConnector - Newhall

Pass

I5 North and South -Newhall Pass

I10 Freeway Los Angeles

At 4:30 am, on January17, 1994, residents of the greater Los Angelesarea were rudelyawakened by the strongshaking of theNorthridge earthquake.This was the firstearthquake to strikedirectly under an urbanarea of the UnitedStates since the 1933Long Beach earthquake.

Approaches to improve the seismicresistance of highway bridges:

• Upgrading of Design Guidelines

• Strengthening or Retrofitting of structuresto enhance their the seismic activity.

Reasons for the collapse:

• The strong shaking of the Northridge earthquake.

• It produced the strongest ground motions ever instrumentally

recorded in an urban setting in North America.

• The high accelerations, both vertical and horizontal, lif ted structures

off of their foundations and/or shifted walls laterally.

Collapse of a 116-year old bridge over the DueroRiver in Portugal killed 70 people on 4March 2001. Scour toppled the central 20 m stonework pier, collapsing 50 m two spans.

Government engineers had just inspected the bridge (ENR 12 March ‘01).

The Webbers Falls Bridge Collapse.

Two empty barges were being pushed up the river by a tugboat, when its master lostcontrol and steered them into one of the supporting piers of thebridge. The accidentoccurred during a thunderstorm, and the river was in flood.

Similar Cases:

• In September 2001, a tug boat and barge struck theQueen Isabella Causeway in Port Isabel, Texas, causinga section of the bridge to tumble into the bay below.Eight people died after motorists drove into the hole.

• In May 1980, a freighter sheared a bridge support inFlorida's Tampa Bay, dropping a section of concreteroadway during morning rush hour. Seven vehicles,including a bus with 26 aboard, fell into the water, killing35 people.

The Quebec Bridge:

On December 3, 1917, after almost 20 years of planning andconstruction, the Quebec Bridge opened for traffic. A major engineering feat in its day, it st ill stands as one of the world's greatbridges.

Two major collapses during construction resulted in heavy loss of life.

Collapse:

First CollapseFailure at the Middle

Span.

The Walnut Street Bridge:

The Walnut St. bridge in Harrisburg, PA had two spans wash away

by an enormous flood.

“Lifted off”

The bridge was 'lif ted' off of its foundations due to the high watersand ice buildup.

It literally floated down the river about 100 yards where it wasdramatically swept under another reinforced concrete bridge."

The Koror-Babeldaob Bridge:

The Koror–Babeldaob Bridge was completed in 1977, to connect the twomain islands of the Palau archipelago.

Its main span of 241 meters (790 ft) was the longest span post-tensionedconcrete box girder bridge structure in the world at the time.

Collapse:

It collapsed suddenly one evening in September 1996, after it hadstood for almost 20 years

Surprise collapse of the Bascule Operator’s Cab at the Miami River & Flagler Street Bridge.

Collapse of an un-braced steel stringer at I-70.

Documents

Lecture03 - Bridge Disasters