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Mechanical failure modes
Buckling
Corrosion
Creep
Fatigue
Fracture
Impact
Mechanical overload
Rupture
Thermal shock
Wear
Yielding

Structural failure refers to loss of the load-carrying capacity of a component or member within a structure or of the structure itself. Structural failure is initiated when the material is stressed to its strength limit, thus causing fracture or excessive deformations. The ultimate failure strength of the material, component or system is its maximum load-bearing capacity. When this limit is reached, damage to the material has been done, and its load-bearing capacity is reduced permanently, significantly, and quickly. In a well-designed system, a localized failure should not cause immediate or even progressive collapse of the entire structure. Ultimate failure strength is one of the limit states that must be accounted for in structural engineering and structural design.

Contents

Dee bridge disaster

The Dee bridge after its collapse

On 24 May 1847 the new railway bridge over the river Dee collapsed as a train passed over it, with the loss of 5 lives. It was designed by Robert Stephenson, using cast iron girders reinforced with wrought iron struts. The bridge collapse was the subject of one of the first formal inquiries into a structural failure. The result of the inquiry was that the design of the structure was fundamentally flawed, as the wrought iron did not reinforce the cast iron at all, and due to repeated flexing it suffered a brittle failure due to fatigue.[1]

First Tay Rail Bridge

The Dee bridge disaster was followed by a number of cast iron bridge collapses, including the collapse of the first Tay Rail Bridge on 28 December 1879. Like the Dee bridge, the Tay collapsed when a train passed over it causing 75 people to lose their lives. The bridge failed because of poorly made cast iron, and the failure of the designer Thomas Bouch to consider wind loading on the bridge. The collapse resulted in cast iron largely being replaced by steel construction, and a complete redesign in 1890 of the Forth Railway Bridge. As a result, the Forth Bridge was the first entirely steel bridge in the world.[2]

First Tacoma Narrows Bridge

Tacoma Narrows Bridge collapsing

The 1940 collapse of Tacoma Narrows Bridge (1940), as the original Tacoma Narrows Bridge is known, is sometimes characterized in physics textbooks as a classical example of resonance; although, this description is misleading. The catastrophic vibrations that destroyed the bridge were not due to simple mechanical resonance, but to a more complicated oscillation between the bridge and winds passing through it, known as aeroelastic flutter. Robert H. Scanlan, father of the field of bridge aerodynamics, wrote an article about this misunderstanding[3]. This collapse, and the research that followed, led to an increased understanding of wind/structure interactions. Several bridges were altered following the collapse to prevent a similar event occurring again. The only fatality was 'Tubby' the dog.[2]

A 1964 B-52 Stratofortress test demonstrated the same failure that caused the 1963 Elephant Mountain & 1964 Savage Mountain crashes.

Aircraft crashes

Repeated structural failures of aircraft types occurred in 1954, when 2 de Havilland Comet C1 jet airliners crashed due to decompression caused by metal fatigue, and in 1963-4, when the vertical stabilizer on 4 Boeing B-52 bombers broke off in mid-air.

Ronan Point

On 16 May 1968 the 22 storey residential tower Ronan Point in the London Borough of Newham collapsed when a relatively small gas explosion on the 18th floor caused a structural wall panel to be blown away from the building. The tower was constructed of precast concrete, and the failure of the single panel caused one entire corner of the building to collapse. The panel was able to be blown out because there was insufficient reinforcement steel passing between the panels. This also meant that the loads carried by the panel could not be redistributed to other adjacent panels, because there was no route for the forces to follow. As a result of the collapse, building regulations were overhauled to prevent "disproportionate collapse", and the understanding of precast concrete detailing was greatly advanced. Many similar buildings were altered or demolished as a result of the collapse.[4]

Hyatt Regency walkway

Design change on the Hyatt Regency walkways.

On 17 July 1981, two suspended walkways through the lobby of the Hyatt Regency in Kansas City, Missouri, collapsed, killing 114 people at a tea dance. The collapse was due to a late change in design, altering the method in which the rods supporting the walkways were connected to them, and inadvertently doubling the forces on the connection. The failure highlighted the need for good communication between design engineers and contractors, and rigorous checks on designs and especially on contractor proposed design changes. The failure is a standard case study on engineering courses around the world, and is used to teach the importance of ethics in engineering.[5][6]

Warsaw Radio Mast

On 8 August 1991 at 16:00 UTC Warsaw radio mast, the tallest man-made object ever built before the erection of Burj Khalifa collapsed as consequence of an error in exchanging the guy-wires on the highest stock. The mast first bent and then snapped at roughly half its height. It destroyed at its collapse a small mobile crane of Mostostal Zabrze. As all workers left the mast before the exchange procedures, there were no fatalities, in contrast to the similar collapse of WLBT Tower in 1997.

Oklahoma City bombing

On 19 April 1995, the nine story concrete framed Alfred P. Murrah Federal Building in Oklahoma was struck by a huge car bomb causing partial collapse, resulting in the deaths of 168 people. The bomb, though large, caused a significantly disproportionate collapse of the structure. The bomb blew all the glass off the front of the building and completely shattered a ground floor reinforced concrete column (see brisance). At second story level a wider column spacing existed, and loads from upper story columns were transferred into fewer columns below by girders at second floor level. The removal of one of the lower story columns caused neighbouring columns to fail due to the extra load, eventually leading to the complete collapse of the central portion of the building. The bombing was one of the first to highlight the extreme forces that blast loading from terrorism can exert on buildings, and led to increased consideration of terrorism in structural design of buildings.[7]

9/11

In the September 11 attacks, two commercial airliners were deliberately crashed into the Twin Towers of the World Trade Center in New York City. The impact and resulting fires caused both towers to collapse within two hours. After the impacts had severed exterior columns and damaged core columns, the loads on these columns were redistributed. The hat trusses at the top of each building played a significant role in this redistribution of the loads in the structure.[8] The impacts dislodged some of the fireproofing from the steel, increasing its exposure to the heat of the fires. Temperatures became high enough to weaken the core columns to the point of creep and plastic deformation under the weight of higher floors. Perimeter columns and floors were also weakened by the heat of the fires, causing the floors to sag and exerting an inward force on exterior walls of the building.[9][10]

I-35W Bridge Collapse

The I-35W Mississippi River bridge (officially known simply as Bridge 9340) was an eight-lane steel truss arch bridge that carried Interstate 35W across the Mississippi River in Minneapolis, Minnesota, United States. The bridge was completed in 1967, and its maintenance was performed by the Minnesota Department of Transportation. The bridge was Minnesota's fifth–busiest,[11][12] carrying 140,000 vehicles daily.[13] The bridge catastrophically failed during the evening rush hour on 1 August 2007, collapsing to the river and riverbanks beneath. Thirteen people were killed and 145 were injured. Following the collapse The Federal Highway Administration (FHWA)advised states to inspect the 700 U.S. bridges of similar construction[14] after a possible design flaw in the bridge was discovered, related to large steel sheets called gusset plates which were used to connect girders together in the truss structure.[15][16] Officials expressed concern about many other bridges in the United States sharing the same design and raised questions as to why such a flaw would not have been discovered in over 40 years of inspections.[16]

See also

References

  1. ^ Petroski, H. (1994) p.81
  2. ^ a b Scott, Richard (2001). In the Wake of Tacoma: Suspension Bridges and the Quest for Aerodynamic Stabilitya. ASCE Publications. pp. 139. ISBN 0784405425. 
  3. ^ K. Billah and R. Scanlan (1991), Resonance, Tacoma Narrows Bridge Failure, and Undergraduate Physics Textbooks, American Journal of Physics, 59(2), 118--124 (PDF)
  4. ^ Feld, Jacob; Carper, Kenneth L. (1997). Construction Failure. John Wiley & Sons. pp. 8. ISBN 0471574775. 
  5. ^ Feld, J.; Carper, K.L. (1997) p.214
  6. ^ Whitbeck, C. (1998) p.115
  7. ^ Virdi, K.S. (2000). Abnormal Loading on Structures: Experimental and Numerical Modelling. Taylor & Francis. pp. 108. ISBN 0419259600. 
  8. ^ "NIST's Responsibilities Under the National Construction Safety Team Act". http://www.nist.gov/public_affairs/factsheet/constructionact.htm. Retrieved 23 April 2008. 
  9. ^ Bažant, Zdeněk P.; Jia-Liang Le, Frank R. Greening and David B. Benson (27 May 2007) (PDF). Collapse of World Trade Center Towers: What Did and Did Not Cause It?. 22 June 2007. Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208, USA. Structural Engineering Report No. 07-05/C605c (page 12). http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20did%20%26%20Did%20Not%20Cause%20It%20-%20Revised%206-22-07.pdf. Retrieved 17 September 2007. 
  10. ^ Bažant, Zdeněk P.; Yong Zhou (1 January 2002). "Why Did the World Trade Center Collapse?—Simple Analysis" (PDF). Journal of Engineering Mechanics 128 (1): 2–6. doi:10.1061/(ASCE)0733-9399(2002)128:1(2). http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/405.pdf. Retrieved 23 August 2007. 
  11. ^ "2006 Metro Area Traffic Volume Index Map" (pdf). Mn/DOT. 2006. http://www.dot.state.mn.us/traffic/data/maps/indexmaps/2006/metroindex.pdf. Retrieved 9 August 2007.  Index map for Mn/DOT's 2006 traffic volumes; relevant maps showing the highest river bridge traffic volumes are Maps 2E, 3E, and 3F.
  12. ^ Weeks, John A. III (2007). "I-35W Bridge Collapse Myths And Conspiracies". John A. Weeks III. http://www.johnweeks.com/i35w/i35wmyths.html. Retrieved 6 August 2007. 
  13. ^ "2006 Downtown Minneapolis Traffic Volumes" (PDF). Minnesota Department of Transportation. 2006. http://www.dot.state.mn.us/traffic/data/maps/indexmaps/2006/mplsin.pdf. Retrieved 7 August 2007.  This map shows average daily traffic volumes for downtown Minneapolis. Trunk highway and Interstate volumes are from 2006.
  14. ^ "U.S. Secretary of Transportation Mary E. Peters Calls on States to Immediately Inspect All Steel Arch Truss Bridges". Press release. http://www.fhwa.dot.gov/pressroom/fhwa0712.htm/. 
  15. ^ National Transportation Safety Board (8 August 2007). "Update on NTSB Investigation of Collapse of I-35W Bride in Minneapolis". Press release. http://www.ntsb.gov/Pressrel/2007/070808.htm. Retrieved 1 December 2007. 
  16. ^ a b Davey, Monica; Wald, Matthew L. (8 August 2007), Potential Flaw Is Found in Design of Fallen Bridge, The New York Times, http://www.nytimes.com/2007/08/08/us/09cnd-bridge.html?hp, retrieved 9 August 2007 
  • Feld, Jacob; Carper, Kenneth L. (1997). Construction Failure. John Wiley & Sons. ISBN 0471574775.
  • Lewis, Peter R. (2007). Disaster on the Dee. Tempus.
  • Petroski, Henry (1994). Design Paradigms: Case Histories of Error and Judgment in Engineering. Cambridge University Press. ISBN 0521466490.
  • Scott, Richard (2001). In the Wake of Tacoma: Suspension Bridges and the Quest for Aerodynamic Stability. ASCE Publications. ISBN 0784405425.

External links

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