Structural integrity and failure is an aspect of

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

that deals with the ability of a structure to support a designed

structural load A structural load or structural action is a mechanical load (more generally a force) applied to Structural engineering#Structural elements, structural elements. A load causes stress (physics), stress, deformation (engineering), deformation, displa ...

(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 prevent

catastrophic failure A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many ot ...

, which can result in injuries, severe damage, death, and/or monetary losses. ''Structural failure'' refers to the loss of structural integrity, or the loss of load-carrying structural capacity in either a structural component or the

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

itself. Structural failure is initiated when a

material A material is a matter, substance or mixture of substances that constitutes an Physical object, object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical property, physical ...

is stressed beyond its strength limit, causing fracture or excessive deformations; one limit 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.

Introduction

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 desired service life. To construct an item with structural integrity, an engineer must first consider a material's mechanical properties, such as

toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.strength, weight,

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

, 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 high

yield strength In materials science and engineering, the yield point is the point on a stress–strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and w ...

, whereas the bolts that hold them need good shear and

tensile strength Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or F_\text in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate ...

. Springs need good elasticity, but

lathe A lathe () is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, threading and turning, with tools that are applied to the w ...

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 to

cascading failure A cascading failure is a failure in a system of interconnection, interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a singl ...

History

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 Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

was one of the first to take the strength of materials into account in 1638, in his treatise ''Dialogues of Two New Sciences''. However, mathematical ways to calculate such material properties did not begin to develop until the 19th century. The science of

fracture mechanics Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics t ...

, as it exists today, was not developed until the 1920s, when Alan Arnold Griffith studied the brittle 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 the stress concentrations at the square corners of the bulkheads. In the 1950s, several

De Havilland Comet The de Havilland DH.106 Comet is the world's first commercial jet airliner. Developed and manufactured by de Havilland in the United Kingdom, the Comet 1 prototype first flew in 1949. It features an aerodynamically clean design with four ...

s 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 explosion A boiler explosion is a catastrophic failure of a boiler. There are two types of boiler explosions. One type is a failure of the pressure parts of the steam and water sides. There can be many different causes, such as failure of the safety val ...

s, 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.''Assuring structural integrity in army systems'' By National Research Council (U.S.). National Materials Advisory Board, National Research Council (U.S.). Commission on Engineering and Technical Systems, National Research Council (U.S.). Committee on Assurance of Structural Integrity – 1985 Page 1—19''Structural Integrity Monitoring'' By R.A. Collacott – Chapman and Hall 1985 Page 1—5

Types of failure

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, improper

heat treating Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are al ...

, 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.

Notable failures

Bridges

Dee bridge

The Dee Bridge was designed by

Robert Stephenson Robert Stephenson , (honoris causa, Hon. causa) (16 October 1803 – 12 October 1859) was an English civil engineer and designer of locomotives. The only son of George Stephenson, the "Father of Railways", he built on the achievements of hi ...

, using

cast iron Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its car ...

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 the

wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.05%) in contrast to that of cast iron (2.1% to 4.5%), or 0.25 for low carbon "mild" steel. Wrought iron is manufactured by heating and melting high carbon cast iron in an ...

did not reinforce the cast iron, and that the casting had failed due to repeated flexing.

First Tay Rail Bridge

The Dee bridge disaster was followed by a number of

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, 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 the Forth Railway Bridge, which became the first bridge in the world entirely made of steel.

First Tacoma Narrows Bridge

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 as aeroelastic flutter. Robert H. Scanlan, a leading contributor to the understanding of bridge aerodynamics, wrote an article about this misunderstanding. 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.

I-35W Bridge

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 The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

Minneapolis Minneapolis is a city in Hennepin County, Minnesota, United States, and its county seat. With a population of 429,954 as of the 2020 United States census, 2020 census, it is the state's List of cities in Minnesota, most populous city. Locat ...

, Minnesota, United States. The bridge was completed in 1967, and its maintenance was performed by the

Minnesota Department of Transportation The Minnesota Department of Transportation (MnDOT, ) oversees Transportation in Minnesota, transportation by all modes including land, water, air, rail, walking and bicycling in the U.S. state of Minnesota. The Cabinet (government), cabinet-lev ...

. The bridge was Minnesota's fifth–busiest, Index map for Mn/DOT's 2006 traffic volumes; relevant maps showing the highest river bridge traffic volumes are Maps 2E, 3E, and 3F. carrying 140,000 vehicles daily. This map shows average daily traffic volumes for downtown Minneapolis. Trunk highway and Interstate volumes are from 2006. 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 The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two programs, the Federal-aid Highway Program a ...

advised states to inspect the 700 U.S. bridges of similar construction after a possible design flaw in the bridge was discovered, related to large steel sheets called

gusset plate In structural engineering and construction, a gusset plate is a plate for connecting Beam (structure), beams and girders to columns. A gusset plate can be fastened to a permanent member either by Bolted joint, bolts, rivets or welding or a combi ...

s which were used to connect

girder A girder () is a Beam (structure), beam used in construction. It is the main horizontal support of a structure which supports smaller beams. Girders often have an I-beam cross section composed of two load-bearing ''flanges'' separated by a sta ...

s together in the truss structure. 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.

Buildings

Thane building collapse

On 4 April 2013, a building collapsed on tribal land in Mumbra, a suburb of

Thane Thane (; previously known as Thana, List of renamed Indian cities and states#Maharashtra, the official name until 1996) is a metropolitan city located on the northwestern side of the list of Indian states, state of Maharashtra in India and on ...

Maharashtra Maharashtra () is a state in the western peninsular region of India occupying a substantial portion of the Deccan Plateau. It is bordered by the Arabian Sea to the west, the Indian states of Karnataka and Goa to the south, Telangana to th ...

, India."Is Municipality as much to blame as builders for Thane building collapse?"
''IBN''. 4 April 2013. Retrieved 5 April 2013. It has been called the worst building collapse in the area: 74 people died, including 18 children, 23 women, and 33 men, while more than 100 people survived. The building was under construction and did not have an occupancy certificate for its 100 to 150 low- to middle-income residents; its only occupants were the site construction workers and their families. The building was reported to have been illegally 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 including builders, 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 use

remote sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...

and a 2010

Bombay High Court The High Court of Bombay is the High courts of India, high court of the States and union territories of India, states of Maharashtra and Goa in India, and the union territory of Dadra and Nagar Haveli and Daman and Diu. It is seated primarily ...

order. Complaints were also made to state and municipal officials. On 9 April, the Thane 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.

Savar building collapse

On 24 April 2013, ''Rana Plaza'', an eight-storey commercial building, collapsed in Savar, a sub-district in the

Greater Dhaka Area Greater Dhaka (''Bengali'': বৃহত্তর ঢাকা) is the Megalopolis including and surrounding the Bangladeshi capital city of Dhaka, which has grown into one of the world's largest megacities, and shows a very rapid rate of expans ...

, the capital of

Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...

. The search for the dead ended on 13 May with the death toll of 1,134. Approximately 2,515 injured people were rescued from the building alive. It is considered to be the deadliest garment-factory accident in history, as well as the deadliest accidental structural failure in modern human history. 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. 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.

Sampoong Department Store collapse

On 29 June 1995, the five-story Sampoong Department Store in the Seocho District of

Seoul Seoul, officially Seoul Special Metropolitan City, is the capital city, capital and largest city of South Korea. The broader Seoul Metropolitan Area, encompassing Seoul, Gyeonggi Province and Incheon, emerged as the world's List of cities b ...

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

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.

Ronan Point

On 16 May 1968, the 22-story residential tower Ronan Point in the

London Borough of Newham The London Borough of Newham () is a London borough created in 1965 by the London Government Act 1963. It covers an area previously administered by the Essex county boroughs of West Ham and East Ham, authorities that were both abolished by ...

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.

Oklahoma City bombing

On 19 April 1995, the nine-story concrete framed Alfred P. Murrah Federal Building in

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

was struck by a truck 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 Brisance (; ) is the shattering capability of a high explosive, determined mainly by its detonation pressure. Application Brisance is of practical importance in explosives engineering for determining the effectiveness of an explosion in blasti ...

). 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.

Versailles wedding hall

The Versailles wedding hall (), located in Talpiot,

Jerusalem Jerusalem is a city in the Southern Levant, on a plateau in the Judaean Mountains between the Mediterranean Sea, Mediterranean and the Dead Sea. It is one of the List of oldest continuously inhabited cities, oldest cities in the world, and ...

, is the site of the worst civil disaster in

Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

'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.

World Trade Center Towers 1, 2, and 7

In the

September 11 attacks The September 11 attacks, also known as 9/11, were four coordinated Islamist terrorist suicide attacks by al-Qaeda against the United States in 2001. Nineteen terrorists hijacked four commercial airliners, crashing the first two into ...

, two commercial airliners were deliberately crashed into the Twin Towers of the World 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. 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. 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.

Champlain Towers

On 24 June 2021, Champlain Towers South, a 12-story condominium building in Surfside, Florida partially collapsed, causing dozens of injuries and 98 deaths. The collapse was captured on video. One person was rescued from the rubble, 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.

First Congregational Church, New London, Connecticut

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

Aircraft

Repeat structural failures on the same type of aircraft occurred in 1954, when two de Havilland Comet C1 jet airliners crashed due to decompression caused by

metal fatigue In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striation (fatigue), striati ...

, and in 1963–64, when the

vertical stabilizer A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, sta ...

on four Boeing B-52 bombers broke off in mid-air.

Other

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 The Burj Khalifa (known as the Burj Dubai prior to its inauguration) is a megatall skyscraper in Dubai, United Arab Emirates. With a total height of 829.8 m (2,722 ft, or just over half a mile) and a roof height (excluding the antenna, but inc ...

, 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 the WLBT Tower in 1997.

Hyatt Regency walkway

On 17 July 1981, two suspended walkways through the lobby of the Hyatt Regency in

Kansas City, Missouri Kansas City, Missouri, abbreviated KC or KCMO, is the largest city in the U.S. state of Missouri by List of cities in Missouri, population and area. The city lies within Jackson County, Missouri, Jackson, Clay County, Missouri, Clay, and Pl ...

, collapsed, killing 114 and injuring more than 200 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.Whitbeck, C. (1998) p.115

References

;Notes ;Citations ;Bibliography * Feld, Jacob; Carper, Kenneth L. (1997). ''Construction Failure''. John Wiley & Sons. . * 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. . * Scott, Richard (2001). ''In the Wake of Tacoma: Suspension Bridges and the Quest for Aerodynamic Stability''. ASCE Publications. . {{DEFAULTSORT:Structural Failure Solid mechanics Materials science Building engineering Mechanical engineering Building defects Structural engineering Engineering failures