Structural integrity and failure is an aspect ofengineering that deals with the ability of a structure to support a designedstructural load (weight, force, etc.) without breaking and includes the study of past structural failures in order to prevent failures in future designs.

Structural integrity is the ability of an item—either a structural component or a structure consisting of many components—to hold together under a load, including its own weight, without breaking or deforming excessively. It assures that the construction will perform its designed function during reasonable use, for as long as its intended life span. Items are constructed with structural integrity to preventcatastrophic failure, which can result in injuries, severe damage, death, and/or monetary losses.

Structural failure refers to the loss of structural integrity, or the loss ofload-carrying structural capacity in either a structural component or thestructure itself. Structural failure is initiated when amaterial is stressed beyond itsstrength limit, causing fracture or excessivedeformations; onelimit state that must be accounted for in structural design is ultimate failure strength. In a well designed system, a localized failure should not cause immediate or even progressive collapse of the entire structure.

Structural integrity is the ability of a structure to withstand an intended load without failing due to fracture, deformation, or fatigue. It is a concept often used in engineering to produce items that will serve their designed purposes and remain functional for a desiredservice life.

To construct an item with structural integrity, an engineer must first consider a material's mechanical properties, such astoughness,strength, weight,hardness, and elasticity, and then determine the size and shape necessary for the material to withstand the desired load for a long life. Since members can neither break nor bend excessively, they must be both stiff and tough. A very stiff material may resist bending, but unless it is sufficiently tough, it may have to be very large to support a load without breaking. On the other hand, a highly elastic material will bend under a load even if its high toughness prevents fracture.

Furthermore, each component's integrity must correspond to its individual application in any load-bearing structure. Bridge supports need a highyield strength, whereas the bolts that hold them need goodshear andtensile strength. Springs need good elasticity, butlathe tooling needs high rigidity. In addition, the entire structure must be able to support its load without its weakest links failing, as this can put more stress on other structural elements and lead tocascading failures.^[1][2]

The need to build structures with integrity goes back as far as recorded history. Houses needed to be able to support their own weight, plus the weight of the inhabitants. Castles needed to be fortified to withstand assaults from invaders. Tools needed to be strong and tough enough to do their jobs.

In ancient times there were no mathematical formulas to predict the integrity of a structure. Builders, blacksmiths, carpenters, and masons relied on a system of trial and error (learning from past failures), experience, and apprenticeship to make safe and sturdy structures. Historically, safety and longevity were ensured by overcompensating, for example, using 20 tons of concrete when 10 tons would do.Galileo was one of the first to take the strength of materials into account in 1638, in his treatiseDialogues of Two New Sciences. However, mathematical ways to calculate such material properties did not begin to develop until the 19th century.^[3] The science offracture mechanics, as it exists today, was not developed until the 1920s, whenAlan Arnold Griffith studied thebrittle fracture of glass.

Starting in the 1940s, the infamous failures of several new technologies made a more scientific method for analyzing structural failures necessary. During World War II, over 200 welded-steel ships broke in half due to brittle fracture, caused by stresses created from the welding process, temperature changes, and by thestress concentrations at the square corners of the bulkheads. In the 1950s, severalDe Havilland Comets exploded in mid-flight due to stress concentrations at the corners of their squared windows, which caused cracks to form and the pressurized cabins to explode.Boiler explosions, caused by failures in pressurized boiler tanks, were another common problem during this era, and caused severe damage. The growing sizes of bridges and buildings led to even greater catastrophes and loss of life. This need to build constructions with structural integrity led to great advances in the fields of material sciences and fracture mechanics.^[4][5]

Structural failure can occur from many types of problems, most of which are unique to different industries and structural types. However, most can be traced to one of five main causes.

• The first is that the structure is not strong and tough enough to support the load, due to either its size, shape, or choice of material. If the structure or component is not strong enough, catastrophic failure can occur when the structure is stressed beyond its critical stress level.
• The second type of failure is from fatigue or corrosion, caused by instability in the structure's geometry, design or material properties. These failures usually begin when cracks form at stress points, such as squared corners or bolt holes too close to the material's edge. These cracks grow as the material is repeatedly stressed and unloaded (cyclic loading), eventually reaching a critical length and causing the structure to suddenly fail under normal loading conditions.
• The third type of failure is caused by manufacturing errors, including improper selection of materials, incorrect sizing, improperheat treating, failing to adhere to the design, or shoddy workmanship. This type of failure can occur at any time and is usually unpredictable.
• The fourth type of failure is from the use of defective materials. This type of failure is also unpredictable, since the material may have been improperly manufactured or damaged from prior use.
• The fifth cause of failure is from lack of consideration of unexpected problems. This type of failure can be caused by events such as vandalism, sabotage, or natural disasters. It can also occur if those who use and maintain the construction are not properly trained and overstress the structure.^[4][5]

The Dee Bridge was designed byRobert Stephenson, usingcast iron girders reinforced with wrought iron struts. On 24 May 1847, it collapsed as a train passed over it, killing five people. Its collapse was the subject of one of the first formal inquiries into a structural failure. This inquiry concluded that the design of the structure was fundamentally flawed, as thewrought iron did not reinforce the cast iron, and that the casting had failed due to repeated flexing.^[6]

The Dee bridge disaster was followed by a number ofcast iron bridge collapses, including the collapse of the firstTay Rail Bridge on 28 December 1879. Like the Dee bridge, the Tay collapsed when a train passed over it, killing 75 people. The bridge failed because it was constructed from poorly made cast iron, and because designer Thomas Bouch failed to consider wind loading on it. Its collapse resulted in cast iron being replaced by steel construction, and a complete redesign in 1890 of theForth Railway Bridge, which became the first bridge in the world entirely made of steel.^[7]

The 1940 collapse of the original Tacoma Narrows Bridge is sometimes characterized in physics textbooks as a classic 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 asaeroelastic flutter.Robert H. Scanlan, a leading contributor to the understanding of bridge aerodynamics, wrote an article about this misunderstanding.^[8] 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 a dog.^[7]

The I-35W Mississippi River bridge (officially known simply as Bridge 9340) was an eight-lane steeltruss arch bridge that carriedInterstate 35W across theMississippi River inMinneapolis, Minnesota, United States. The bridge was completed in 1967, and its maintenance was performed by theMinnesota Department of Transportation. The bridge was Minnesota's fifth–busiest,^[9][10] carrying 140,000 vehicles daily.^[11] The bridgecatastrophically failed during the eveningrush hour on 1 August 2007, collapsing to the river and riverbanks beneath. Thirteen people were killed and 145 were injured. Following the collapse, theFederal Highway Administration advised states to inspect the 700 U.S. bridges of similar construction^[12] after a possible design flaw in the bridge was discovered, related to large steel sheets calledgusset plates which were used to connectgirders together in the truss structure.^[13][14] 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.^[14]

On 4 April 2013, a building collapsed on tribal land inMumbra, a suburb ofThane inMaharashtra, India.^[15][16] It has been called the worstbuilding collapse in the area^{[17][nb 1]}: 74 people died, including 18 children, 23 women, and 33 men, while more than 100 people survived.^[20][21][22]

The building was under construction and did not have anoccupancy certificate for its 100 to 150 low- to middle-income residents^[23]; its only occupants were the site construction workers and their families. The building was reported to have beenillegally constructed because standard practices were not followed for safe, lawful construction, land acquisition and resident occupancy.

By 11 April, a total of 15 suspects were arrested includingbuilders, engineers, municipal officials, and other responsible parties. Governmental records indicate that there were two orders to manage the number of illegal buildings in the area: a 2005 Maharashtra state order to useremote sensing and a 2010Bombay High Court order. Complaints were also made to state and municipal officials.

On 9 April, theThane Municipal Corporation began a campaign to demolish illegal buildings in the area, focusing on "dangerous" buildings, and set up a call center to accept and track the resolutions of complaints about illegal buildings. The forest department, meanwhile, promised to address encroachment of forest land in the Thane District.

On 24 April 2013,Rana Plaza, an eight-storey commercial building, collapsed inSavar, asub-district in theGreater Dhaka Area, the capital ofBangladesh. The search for the dead ended on 13 May with the death toll of 1,134.^[24] Approximately 2,515 injured people were rescued from the building alive.^[25][26]

It is considered to be the deadliest garment-factory accident in history, as well as the deadliest accidental structural failure in modern human history.^[23][27]

The building contained clothing factories, a bank, apartments, and several other shops. The shops and the bank on the lower floors immediately closed after cracks were discovered in the building.^[28][29][30] Warnings to avoid using the building after cracks appeared the day before had been ignored. Garment workers were ordered to return the following day and the building collapsed during the morning rush-hour.^[31]

On 29 June 1995, the five-storySampoong Department Store in theSeocho District ofSeoul,South Korea collapsed resulting in the deaths of 502 people, with another 1,445 being trapped.

In April 1995, cracks began to appear in the ceiling of the fifth floor of the store's south wing due to the presence of an air-conditioning unit on the weakened roof of the poorly built structure. On the morning of 29 June, as the number of cracks in the ceiling increased dramatically, store managers closed the top floor and shut off the air conditioning, but failed to shut the building down or issue formal evacuation orders as the executives themselves left the premises as a precaution.

Five hours before the collapse, the first of several loud bangs was heard emanating from the top floors, as the vibration of the air conditioning caused the cracks in the slabs to widen further. Amid customer reports of vibration in the building, the air conditioning was turned off but, the cracks in the floors had already grown to 10 cm wide. At about 5:00 p.m. local time, the fifth-floor ceiling began to sink, and at 5:57 p.m., the roof gave way, sending the air conditioning unit crashing through into the already-overloaded fifth floor.

On 16 May 1968, the 22-story residential tower Ronan Point in theLondon 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 ofprecast 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 preventdisproportionate collapse and the understanding of precast concrete detailing was greatly advanced. Many similar buildings were altered or demolished as a result of the collapse.^[32]

On 19 April 1995, the nine-story concrete framedAlfred P. Murrah Federal Building inOklahoma was struck by atruck 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 floorreinforced concrete column (seebrisance). 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.^[33]

The Versailles wedding hall (Hebrew:אולמי ורסאי), located inTalpiot,Jerusalem, is the site of the worst civil disaster inIsrael's history. At 22:43 on Thursday night, 24 May 2001 during the wedding of Keren and Asaf Dror, a large portion of the third floor of the four-story building collapsed, killing 23 people. The bride and the groom survived.

In theSeptember 11 attacks, two commercial airliners were deliberately crashed into the Twin Towers of theWorld Trade Center in New York City. The impact, explosion and resulting fires caused both towers to collapse within less than two hours. The impacts severed exterior columns and damaged core columns, redistributing the loads that these columns had carried. This redistribution of loads was greatly influenced by the hat trusses at the top of each building.^[34] 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 ofcreep andplastic deformation under the weight of higher floors. The heat of the fires also weakened the perimeter columns and floors, causing the floors to sag and exerting an inward force on exterior walls of the building. WTC Building 7 also collapsed later that day; the 47-story skyscraper collapsed within seconds due to a combination of a large fire inside the building and heavy structural damage from the collapse of the North Tower.^[35][36]

On 24 June 2021, Champlain Towers South, a 12-story condominium building inSurfside, Florida partially collapsed, causing dozens of injuries and 98 deaths.^[37] The collapse was captured on video.^[38] One person was rescued from the rubble,^[39] and about 35 people were rescued on 24 June from the uncollapsed portion of the building. Long-term degradation of reinforced concrete-support structures in the underground parking garage, due to water penetration and corrosion of the reinforcing steel, has been considered as a factor in—or the cause of—the collapse. The issues had been reported in 2018 and noted as "much worse" in April 2021. A $15 million program of remedial works had been approved at the time of the collapse.

On 24 January, 2024, the spire of this Gothic-revival stone church collapsed, bringing down the roof and irretrievably damaging the structure.^[40]

Repeat structural failures on the same type of aircraft occurred in 1954, when twode Havilland Comet C1 jet airliners crashed due to decompression caused bymetal fatigue, and in 1963–64, when thevertical stabilizer on fourBoeing B-52 bombers broke off in mid-air.

On 8 August 1991 at 16:00 UTC Warsaw radio mast, the tallest man-made object ever built before the erection ofBurj Khalifa, collapsed as a 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 had left the mast before the exchange procedures, there were no fatalities, in contrast to the similar collapse of theWLBT Tower in 1997.

On 17 July 1981, two suspended walkways through the lobby of theHyatt Regency inKansas City, Missouri, collapsed, killing 114 and injuring more than 200 people^[41] 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 ofethics in engineering.^[42][43]

• Structural analysis
• Structural robustness
• Catastrophic failure
• Earthquake engineering
• Porch collapse
• Forensic engineering
• Progressive collapse
• Seismic performance
• Serviceability failure
• Structural fracture mechanics
• Collapse zone
• Engineering disasters
• Tofu-dreg project
• Urban search and rescue
• List of structural failures and collapses

Notes

Citations

Bibliography

• Feld, Jacob; Carper, Kenneth L. (1997).Construction Failure. John Wiley & Sons.ISBN 0-471-57477-5.
• 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 0-521-46649-0.
• Scott, Richard (2001).In the Wake of Tacoma: Suspension Bridges and the Quest for Aerodynamic Stability. ASCE Publications.ISBN 0-7844-0542-5.