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78-561: The Diefenbunker , formerly known by its military designation, Canadian Forces Station Carp (CFS Carp) , is a large underground four-storey reinforced concrete bunker and nuclear fallout shelter located in the rural area of Carp, Ontario approximately 30 km (19 mi) west of downtown Ottawa . Between 1957 and 1961, during the Cold War the Government of Canada led by then Prime Minister John Diefenbaker authorized

156-539: A critical understanding of the Cold War, by preserving the Diefenbunker as a national historic site, and operating a Cold War Museum. The Diefenbunker houses a collection of Cold War artifacts, an archive and a library, all of which are made available to researchers upon request, and to the general public through the exhibitions. The Diefenbunker: Canada's Cold War museum is a not-for-profit, charitable museum. It

234-404: A deeply buried bunker. The extra speed provided by a rocket motor enables greater penetration of a missile-mounted bunker buster warhead. To reach maximum penetration ( impact depth ), the warhead may consist of a high-density projectile only. Such a warhead carries more energy than a warhead with chemical explosives (kinetic energy of a projectile at hypervelocity ). The nuclear bunker buster

312-453: A major role in the evolution of concrete construction as a proven and studied science. Without Hyatt's work, more dangerous trial and error methods might have been depended on for the advancement in the technology. Joseph Monier , a 19th-century French gardener, was a pioneer in the development of structural, prefabricated and reinforced concrete, having been dissatisfied with the existing materials available for making durable flowerpots. He

390-428: A movie set on several occasions, including for The Sum of All Fears and Rulers of Darkness . Download coordinates as: Reinforced concrete Reinforced concrete , also called ferroconcrete , is a composite material in which concrete 's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement

468-419: A reduction in its durability. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete. When rebar corrodes, the oxidation products ( rust ) expand and tends to flake, cracking the concrete and unbonding the rebar from the concrete. Typical mechanisms leading to durability problems are discussed below. Cracking of the concrete section is nearly impossible to prevent; however,

546-570: A reported strike accuracy of 7 m (23 ft) CEP . The US has a series of custom made bombs such as the Paveway series of laser-guided bombs to penetrate hardened or deeply buried structures: More recently, the US has developed the 30,000 lb (14,000 kg) GBU-57 . Turkey is another country known to be developing bunker busters, such as the SARB-83 and NEB-84. The traditional fuze

624-423: A standard, air-burst nuclear detonation because they would have relatively low explosive yield . However, because such weapons necessarily come into contact with large amounts of earth-based debris, they may, under certain circumstances, still generate significant fallout. Warhead yield and weapon design have changed periodically throughout the history of the design of such weapons. An underground explosion releases

702-426: A well-chosen concrete mix will provide additional protection for many applications. Uncoated, low carbon/chromium rebar looks similar to standard carbon steel rebar due to its lack of a coating; its highly corrosion-resistant features are inherent in the steel microstructure. It can be identified by the unique ASTM specified mill marking on its smooth, dark charcoal finish. Epoxy-coated rebar can easily be identified by

780-658: Is a mixture of coarse (stone or brick chips) and fine (generally sand and/or crushed stone) aggregates with a paste of binder material (usually Portland cement ) and water. When cement is mixed with a small amount of water, it hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid shape. The aggregates used for making concrete should be free from harmful substances like organic impurities, silt, clay, lignite, etc. Typical concrete mixes have high resistance to compressive stresses (about 4,000 psi (28 MPa)); however, any appreciable tension ( e.g., due to bending ) will break

858-528: Is coating them with zinc phosphate . Zinc phosphate slowly reacts with calcium cations and the hydroxyl anions present in the cement pore water and forms a stable hydroxyapatite layer. Penetrating sealants typically must be applied some time after curing. Sealants include paint, plastic foams, films and aluminum foil , felts or fabric mats sealed with tar, and layers of bentonite clay, sometimes used to seal roadbeds. Corrosion inhibitors , such as calcium nitrite [Ca(NO 2 ) 2 ], can also be added to

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936-972: Is currently open year-round for public tours. Many areas of the bunker, including the PM's Suite, the Emergency Government Situation Centre, the CBC Emergency Broadcasting Studio, the Military Federal Warning Centre, the External Affairs Ministerial Office, the Public Works Minister's Office and the Bank of Canada Vault, are being restored to their operational condition. The rest of the 358 rooms have been converted to exhibits of

1014-496: Is funded privately; the main source of revenue for the museum comes from admission sales (approximately 75% of total revenue). The Diefenbunker actively applies for private, municipal, provincial and federal grants. The museum also relies on the generous support of the community through donations and sponsorship. The Diefenbunker offers additional services on top of public tours. The museum has space available to rent both for events and storage. The decommissioned bunker has been used as

1092-478: Is important as an engineering achievement and to the critical path method of planning used in its construction. In addition, the Diefenbunker is symbolic of the Cold War, a strategy of nuclear deterrence and the Canadian people's determination to survive as a nation following a nuclear war. The Historic Sites and Monuments Board of Canada (HSMBC) plaque located at the Diefenbunker states: Irreverently known as

1170-504: Is located across the bay from San Francisco . Two years later, El Campanil survived the 1906 San Francisco earthquake without any damage, which helped build her reputation and launch her prolific career. The 1906 earthquake also changed the public's initial resistance to reinforced concrete as a building material, which had been criticized for its perceived dullness. In 1908, the San Francisco Board of Supervisors changed

1248-541: Is one in which both the compressive and tensile zones reach yielding at the same imposed load on the beam, and the concrete will crush and the tensile steel will yield at the same time. This design criterion is however as risky as over-reinforced concrete, because failure is sudden as the concrete crushes at the same time of the tensile steel yields, which gives a very little warning of distress in tension failure. Steel-reinforced concrete moment-carrying elements should normally be designed to be under-reinforced so that users of

1326-428: Is one in which the concrete element is only reinforced near the tensile face and the reinforcement, called tension steel, is designed to resist the tension. A doubly reinforced beam is the section in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression and take stresses. The latter reinforcement is called compression steel. When

1404-430: Is one in which the tension capacity of the tension steel is greater than the combined compression capacity of the concrete and the compression steel (over-reinforced at tensile face). So the "over-reinforced concrete" beam fails by crushing of the compressive-zone concrete and before the tension zone steel yields, which does not provide any warning before failure as the failure is instantaneous. A balanced-reinforced beam

1482-401: Is the nuclear weapon version of the bunker buster. The non-nuclear component of the weapon is designed to greatly enhance the penetration into soil , rock , or concrete to deliver a nuclear warhead to a target. These weapons would be used to destroy hardened, underground military bunkers deeply buried. In theory, the amount of radioactive nuclear fallout would be reduced from that of

1560-412: Is the same as a classic armor-piercing bomb : a combination of timer and a sturdy dynamic propeller on the rear of the bomb. The fuze is armed when the bomb is released, and detonates when the propeller stops turning and the timer has expired. Modern bunker busters may use a traditional fuze, but some also include a microphone and microcontroller . The microphone listens, and the microcontroller counts

1638-579: Is the theoretical failure point with a certain probability. It is stated under factored loads and factored resistances. Reinforced concrete structures are normally designed according to rules and regulations or recommendation of a code such as ACI-318, CEB, Eurocode 2 or the like. WSD, USD or LRFD methods are used in design of RC structural members. Analysis and design of RC members can be carried out by using linear or non-linear approaches. When applying safety factors, building codes normally propose linear approaches, but for some cases non-linear approaches. To see

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1716-446: Is transferred from the concrete to the bar interface so as to change the tensile stress in the reinforcing bar along its length. This load transfer is achieved by means of bond (anchorage) and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface. The reasons that the two different material components concrete and steel can work together are as follows: (1) Reinforcement can be well bonded to

1794-404: Is usually, though not necessarily, steel reinforcing bars (known as rebar ) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of

1872-850: The Communications and Electronics Branch ). A decentralized transmitter site, the Richardson Detachment , with numerous transmitter antennas, was located further to the west near Perth, Ontario that was supported from a 2-storey underground facility of similar construction to the Carp facility but much smaller. The Perth bunker has seen some recent local controversy, as it still remains on government owned land, surrounded by local development. Radio receiving facilities CFS Carp Almonte Detachment and CFS Carp Dunrobin Detachment , with complete receiving antenna arrays, were also built in

1950-598: The Valentin U-Boat pens at Farge , two Grand Slams went through the 15 ft (4.5 m) reinforced concrete hardening —equalling or exceeding the best current penetration specifications. The British Disney bomb (officially "4500 lb [2,000 kg] Concrete piercing/Rocket Assisted Bomb", also known as the "Crab") was a World War II device designed to be used against U-boat pens and other super-hardened targets. Devised by Captain Edward Terrell RNVR of

2028-420: The bouncing bomb , designed two bombs that would become the conceptual predecessors of modern bunker busters: the five tonne Tallboy and the ten tonne Grand Slam . These were "Earthquake" bombs —a concept he had first proposed in 1939. The designs were very aerodynamic, allowing them to exceed the speed of sound as they fell from 22,000 ft (6,700 m). The tails were designed with offset fins causing

2106-740: The strikes that killed Hezbollah leader Hassan Nasrallah in Beirut on 27 September 2024. During Operation Desert Storm (1991), there was a need for a deep penetration bomb similar to the British weapons of World War II, but none of the NATO air forces had such a weapon. As a stop-gap, some were developed over a period of 28 days, using old 8 inch (203 mm) artillery barrels as casings. These bombs weighed over two tons but carried only 647 lb (293 kg) of high explosive. They were laser-guided and were designated "Guided Bomb Unit-28 ( GBU-28 )". It

2184-468: The tensile strength of concrete was improved by the reinforcing. Before the 1870s, the use of concrete construction, though dating back to the Roman Empire , and having been reintroduced in the early 19th century, was not yet a proven scientific technology. Ernest L. Ransome , an English-born engineer, was an early innovator of reinforced concrete techniques at the end of the 19th century. Using

2262-566: The "Diefenbunker," this structure is a powerful symbol of Canada's response to the Cold War. Designed in the 1950s to withstand all but a direct hit by a nuclear weapon, it was intended to shelter key political and military personnel during a nuclear attack. Fortunately, it never served its intended purpose, although the Diefenbaker government made plans to retreat to its protection during the Cuban missile crisis of 1962. The bunker functioned as

2340-719: The 1890s, Wayss and his firm greatly contributed to the advancement of Monier's system of reinforcing, established it as a well-developed scientific technology. One of the first skyscrapers made with reinforced concrete was the 16-story Ingalls Building in Cincinnati, constructed in 1904. The first reinforced concrete building in Southern California was the Laughlin Annex in downtown Los Angeles , constructed in 1905. In 1906, 16 building permits were reportedly issued for reinforced concrete buildings in

2418-415: The 2000s. Close to 15,000 visitors passed through the Diefenbunker in 2000. Additional part-time staff were hired throughout the year to keep up with museum maintenance and upkeep. As of 2008, the Diefenbunker averages approximately 25,000 visitors each year. Four full-time staff, nine part-time staff and numerous volunteers work to keep the museum running smoothly. In 2012, the museum had 45,280 visitors. This

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2496-518: The Admiralty's Directorate of Miscellaneous Weapons Development , it had a streamlined hardened case and weighed about 4,500 lb (2,000 kg) including the rocket assembly. The actual explosive content was about 500 lb (230 kg). For accuracy, the bombs had to be dropped precisely from a pre-determined height (usually 20,000 ft (6,100 m)). They would free-fall for around 30 seconds until, at 5,000 ft (1,500 m),

2574-697: The City of Los Angeles, including the Temple Auditorium and 8-story Hayward Hotel. In 1906, a partial collapse of the Bixby Hotel in Long Beach killed 10 workers during construction when shoring was removed prematurely. That event spurred a scrutiny of concrete erection practices and building inspections. The structure was constructed of reinforced concrete frames with hollow clay tile ribbed flooring and hollow clay tile infill walls. That practice

2652-406: The Cold War era. Upon its opening in 1998, the museum was run entirely by volunteers. However, the 5,000 visitors received by the museum that year was too much to be handled solely by volunteers. In 1999, the museum's second year of operation, a curator was hired along with some students. The museum's visitation doubled to 10,000 people that year. The museum continued to grow in popularity during

2730-659: The Diefenbunker to be designed and built as the Central Emergency Government Headquarters (CEGHQ Carp) in an attempt to ensure the continuity of government subsequent to a nuclear weapons attack by the Soviet Union . In 1994, CFS Carp was decommissioned and closed. In 1994, the Diefenbunker was designated a National Historic Site of Canada because it is considered the most important surviving Cold War site in Canada. The bunker

2808-607: The English counties of Norfolk and Suffolk. In 1877, Thaddeus Hyatt , published a report entitled An Account of Some Experiments with Portland-Cement-Concrete Combined with Iron as a Building Material, with Reference to Economy of Metal in Construction and for Security against Fire in the Making of Roofs, Floors, and Walking Surfaces , in which he reported his experiments on the behaviour of reinforced concrete. His work played

2886-607: The German engineer August Coenders , based on the theory of increasing sectional density to improve penetration. They were tested in 1942 and 1943 against the Belgian Fort d'Aubin-Neufchâteau . In World War II the Luftwaffe developed a series of unguided rocket-propelled armor-piercing bombs for use against shipping and fortifications. In World War II , the British designer Barnes Wallis , already famous for inventing

2964-571: The US added a form of remote guidance to the Tallboy to create the Tarzon , a 12,000 lb (5,400 kg) bomb deployed in the Korean War against an underground command center near Kanggye . The BLU-109 bomb is intended to penetrate concrete shelters and other hardened structures before exploding. It entered service in 1985. Israeli F-15I fighter jets are believed to have used BLU-109s in

3042-695: The actual available length is inadequate for full development, special anchorages must be provided, such as cogs or hooks or mechanical end plates. The same concept applies to lap splice length mentioned in the codes where splices (overlapping) provided between two adjacent bars in order to maintain the required continuity of stress in the splice zone. In wet and cold climates, reinforced concrete for roads, bridges, parking structures and other structures that may be exposed to deicing salt may benefit from use of corrosion-resistant reinforcement such as uncoated, low carbon/chromium (micro composite), epoxy-coated, hot dip galvanized or stainless steel rebar. Good design and

3120-461: The actual bond stress varies along the length of a bar anchored in a zone of tension, current international codes of specifications use the concept of development length rather than bond stress. The main requirement for safety against bond failure is to provide a sufficient extension of the length of the bar beyond the point where the steel is required to develop its yield stress and this length must be at least equal to its development length. However, if

3198-479: The behavior of the final structure under working loads. In the United States , the most common methods of doing this are known as pre-tensioning and post-tensioning . For a strong, ductile and durable construction the reinforcement needs to have the following properties at least: François Coignet used iron-reinforced concrete as a technique for constructing building structures. In 1853, Coignet built

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3276-403: The bombs to spin as they fell. Using the same principle as a spinning top , this enabled them to resist being deflected, thereby improving accuracy. They had casings of high grade steel, much stronger than the typical World War II bomb so that they would survive hitting a hardened surface, or penetrate deep into the ground. Though these bombs might be thought of as "bunker busters" today, in fact

3354-543: The chief reasons for the failure of reinforcement bars in concrete. The relative cross-sectional area of steel required for typical reinforced concrete is usually quite small and varies from 1% for most beams and slabs to 6% for some columns. Reinforcing bars are normally round in cross-section and vary in diameter. Reinforced concrete structures sometimes have provisions such as ventilated hollow cores to control their moisture & humidity. Distribution of concrete (in spite of reinforcement) strength characteristics along

3432-756: The city's building codes to allow wider use of reinforced concrete. In 1906, the National Association of Cement Users (NACU) published Standard No. 1 and, in 1910, the Standard Building Regulations for the Use of Reinforced Concrete . Many different types of structures and components of structures can be built using reinforced concrete elements including slabs , walls , beams , columns , foundations , frames and more. Reinforced concrete can be classified as precast or cast-in-place concrete . Designing and implementing

3510-422: The compression zone of a concrete is inadequate to resist the compressive moment (positive moment), extra reinforcement has to be provided if the architect limits the dimensions of the section. An under-reinforced beam is one in which the tension capacity of the tensile reinforcement is smaller than the combined compression capacity of the concrete and the compression steel (under-reinforced at tensile face). When

3588-521: The concrete protects the steel rebar from corrosion . Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed (concrete in compression, reinforcement in tension), so as to improve

3666-541: The concrete resists compression and reinforcement " rebar " resists tension can be made into almost any shape and size for the construction industry. Three physical characteristics give reinforced concrete its special properties: As a rule of thumb, only to give an idea on orders of magnitude, steel is protected at pH above ~11 but starts to corrode below ~10 depending on steel characteristics and local physico-chemical conditions when concrete becomes carbonated. Carbonation of concrete along with chloride ingress are amongst

3744-412: The concrete roof and floors in the two-story house he was constructing. His positioning of the reinforcement demonstrated that, unlike his predecessors, he had knowledge of tensile stresses. Between 1869 and 1870, Henry Eton would design, and Messrs W & T Phillips of London construct the wrought iron reinforced Homersfield Bridge bridge, with a 50' (15.25 meter) span, over the river Waveney, between

3822-416: The concrete, thus they can jointly resist external loads and deform. (2) The thermal expansion coefficients of concrete and steel are so close ( 1.0 × 10 to 1.5 × 10 for concrete and 1.2 × 10 for steel) that the thermal stress-induced damage to the bond between the two components can be prevented. (3) Concrete can protect the embedded steel from corrosion and high-temperature induced softening. Because

3900-500: The concrete, which occurs when compressive stresses exceed its strength, by yielding or failure of the rebar when bending or shear stresses exceed the strength of the reinforcement, or by bond failure between the concrete and the rebar. Carbonation, or neutralisation, is a chemical reaction between carbon dioxide in the air and calcium hydroxide and hydrated calcium silicate in the concrete. Bunker buster Röchling shells were bunker-busting artillery shells, developed by

3978-601: The creation of close to 50 Emergency Government Headquarters (nicknamed "Diefenbunkers" by opposition parties) across Canada. These shelters were part of what came to be known as the Continuity of Government plan, which was meant to protect various members of government in the event of a nuclear attack. The original site, some 9.7 km (6.0 mi) east of Almonte ( 45°15′06.66″N 076°19′31.05″W  /  45.2518500°N 76.3252917°W  / 45.2518500; -76.3252917  ( Almonte, Ontario ) ),

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4056-403: The cross-section of vertical reinforced concrete elements is inhomogeneous. The reinforcement in a RC structure, such as a steel bar, has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity, slip or separation of the two materials under load. Maintaining composite action requires transfer of load between the concrete and steel. The direct stress

4134-403: The examples of a non-linear numerical simulation and calculation visit the references: Prestressing concrete is a technique that greatly increases the load-bearing strength of concrete beams. The reinforcing steel in the bottom part of the beam, which will be subjected to tensile forces when in service, is placed in tension before the concrete is poured around it. Once the concrete has hardened,

4212-601: The facility. The local municipality took control of the facility and a group of local volunteers, recognizing the heritage and tourism value of the Carp Diefenbunker, undertook to open the facility as a cold war museum and conduct public tours. It was purchased by the Diefenbunker Development Group in 1998, and officially opened as a museum. The name of the facility was changed to "Diefenbunker, Canada's Cold War Museum" shortly thereafter. It

4290-515: The first concrete buildings constructed in the United States was a private home designed by William Ward , completed in 1876. The home was particularly designed to be fireproof. G. A. Wayss was a German civil engineer and a pioneer of the iron and steel concrete construction. In 1879, Wayss bought the German rights to Monier's patents and, in 1884, his firm, Wayss & Freytag , made the first commercial use of reinforced concrete. Up until

4368-511: The first iron reinforced concrete structure, a four-story house at 72 rue Charles Michels in the suburbs of Paris. Coignet's descriptions of reinforcing concrete suggests that he did not do it for means of adding strength to the concrete but for keeping walls in monolithic construction from overturning. The, 1872–1873, Pippen building in Brooklyn stands as a testament to his technique. In 1854, English builder William B. Wilkinson reinforced

4446-427: The hub of a communications network and civil defence system until it closed in 1994. In 1998, the facility was re-opened as a museum called the " Diefenbunker: Canada's Cold War Museum " allowing the general public year-round access to tour the facility. In 1958, at the height of the Cold War and the infancy of the intercontinental ballistic missile (ICBM) threat, Prime Minister John Diefenbaker authorized

4524-660: The knowledge of reinforced concrete developed during the previous 50 years, Ransome improved nearly all the styles and techniques of the earlier inventors of reinforced concrete. Ransome's key innovation was to twist the reinforcing steel bar, thereby improving its bond with the concrete. Gaining increasing fame from his concrete constructed buildings, Ransome was able to build two of the first reinforced concrete bridges in North America. One of his bridges still stands on Shelter Island in New Yorks East End, One of

4602-824: The light green color of its epoxy coating. Hot dip galvanized rebar may be bright or dull gray depending on length of exposure, and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbon steel reinforcing bar. Reference ASTM standard specifications A1035/A1035M Standard Specification for Deformed and Plain Low-carbon, Chromium, Steel Bars for Concrete Reinforcement, A767 Standard Specification for Hot Dip Galvanized Reinforcing Bars, A775 Standard Specification for Epoxy Coated Steel Reinforcing Bars and A955 Standard Specification for Deformed and Plain Stainless Bars for Concrete Reinforcement. Another, cheaper way of protecting rebars

4680-438: The microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension. If a material with high strength in tension, such as steel , is placed in concrete, then the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A composite section where

4758-656: The most efficient floor system is key to creating optimal building structures. Small changes in the design of a floor system can have significant impact on material costs, construction schedule, ultimate strength, operating costs, occupancy levels and end use of a building. Without reinforcement, constructing modern structures with concrete material would not be possible. When reinforced concrete elements are used in construction, these reinforced concrete elements exhibit basic behavior when subjected to external loads . Reinforced concrete elements may be subject to tension , compression , bending , shear , and/or torsion . Concrete

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4836-576: The number of floors until the bomb breaks through the desired numbers of floors. Northrop Grumman is working on the Hard Target Void Sensing Fuze (HTVSF), an electronic, cockpit programmable, fuze capable of destroying deeply buried and targets. It provides multiple delay arming and detonation times, as well as a void-sensing capability, which allows for precision activation of the fuze for 2,000-and-5,000-pound (910 and 2,270 kg) weapons to explode when they reach an open space in

4914-609: The original "earthquake" theory was more complex and subtle than simply penetrating a hardened surface. The earthquake bombs were designed not to strike a target directly, but to impact beside it, penetrate under it, and create a ' camouflet ', or large buried cavern, at the same time as delivering a shock wave through the target's foundations. The target then collapses into the hole, no matter how hardened it may be. The bombs had strong casings because they needed to travel through rock rather than reinforced concrete, though they could perform equally well against hardened surfaces. In an attack on

4992-448: The passivation of steel at the anodic oxidation sites. Nitrite is a much more active corrosion inhibitor than nitrate , which is a less powerful oxidizer of the divalent iron. A beam bends under bending moment , resulting in a small curvature. At the outer face (tensile face) of the curvature the concrete experiences tensile stress, while at the inner face (compressive face) it experiences compressive stress. A singly reinforced beam

5070-523: The region, however, all of those buildings were above ground. CFS Carp was decommissioned in 1994 following the reduction of the ICBM threat. From 1959 to 1994, the site was owned and operated by the Canadian Department of National Defence. After the local municipality took control of the facility in 1994, the community took a great interest in the bunker, requesting access to public tours of

5148-433: The reinforced concrete element is subject to increasing bending moment, the tension steel yields while the concrete does not reach its ultimate failure condition. As the tension steel yields and stretches, an "under-reinforced" concrete also yields in a ductile manner, exhibiting a large deformation and warning before its ultimate failure. In this case the yield stress of the steel governs the design. An over-reinforced beam

5226-515: The rockets were ignited, causing the tail section to be expelled. The rocket burn lasted for three seconds and added 300 ft/s (91 m/s) to the bomb's speed, giving a final impact speed of 1,450 ft/s (440 m/s; 990 mph), approximately Mach 1.29. Post-war tests demonstrated that the bombs were able to penetrate a 14-foot-8-inch (4.47 m) thick concrete roof, with the predicted (but untested) ability to penetrate 16 feet 8 inches (5.08 m) of concrete. Post war,

5304-581: The size and location of cracks can be limited and controlled by appropriate reinforcement, control joints, curing methodology and concrete mix design. Cracking can allow moisture to penetrate and corrode the reinforcement. This is a serviceability failure in limit state design . Cracking is normally the result of an inadequate quantity of rebar, or rebar spaced at too great a distance. The concrete cracks either under excess loading, or due to internal effects such as early thermal shrinkage while it cures. Ultimate failure leading to collapse can be caused by crushing

5382-474: The structure will receive warning of impending collapse. The characteristic strength is the strength of a material where less than 5% of the specimen shows lower strength. The design strength or nominal strength is the strength of a material, including a material-safety factor. The value of the safety factor generally ranges from 0.75 to 0.85 in Permissible stress design . The ultimate limit state

5460-454: The tension on the reinforcing steel is released, placing a built-in compressive force on the concrete. When loads are applied, the reinforcing steel takes on more stress and the compressive force in the concrete is reduced, but does not become a tensile force. Since the concrete is always under compression, it is less subject to cracking and failure. Reinforced concrete can fail due to inadequate strength, leading to mechanical failure, or due to

5538-403: The water mix before pouring concrete. Generally, 1–2 wt. % of [Ca(NO 2 ) 2 ] with respect to cement weight is needed to prevent corrosion of the rebars. The nitrite anion is a mild oxidizer that oxidizes the soluble and mobile ferrous ions (Fe ) present at the surface of the corroding steel and causes them to precipitate as an insoluble ferric hydroxide (Fe(OH) 3 ). This causes

5616-444: Was abandoned when ground water proved impossible to remove. An abandoned gravel pit outside Carp was selected instead, where construction soon began in 1959 and was completed by 1962. The Carp shelter would be the largest of such facilities (over 9,300 m (100,000 sq ft)) and the only one in the immediate Ottawa area. The underground 4-storey bunker required 32,000 tonnes of concrete and 5,000 tonnes of steel. The structure

5694-646: Was built for food, fuel, fresh water, and other supplies. The bunker was built to accommodate 565 people for up to one month without receiving additional supplies from the outside. It included an emergency broadcast studio for the Canadian Broadcasting Corporation and a vault on the lowest level to hold the gold reserves of the Bank of Canada . These facilities were administered by the Royal Canadian Corps of Signals (later

5772-527: Was capable of withstanding a nuclear blast of up to 5 megatons from 1.8 km (1.1 mi) away. It had massive blast doors at the surface, as well as extensive air filters to prevent radiation infiltration. Although supposedly effective against surface nuclear detonations, the facility was later found to be vulnerable to conventional Bunker buster bombs developed after its construction, as these bombs had time delay fuses that would detonate after they had penetrated deeply enough underground. Underground storage

5850-404: Was granted a patent for reinforcing concrete flowerpots by means of mixing a wire mesh and a mortar shell. In 1877, Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders, using iron rods placed in a grid pattern. Though Monier undoubtedly knew that reinforcing concrete would improve its inner cohesion, it is not clear whether he even knew how much

5928-468: Was one of the highest increases in attendance other than the opening year of the Bunker. In 2017, Canada's sesquicentennial, the Diefenbunker welcomed 88,000 visitors through its blast doors. Since March 2016, the museum has also hosted an escape room that they state is the world's largest. The mandate of Diefenbunker, Canada's Cold War museum is "to increase throughout Canada and the world, interest in and

6006-571: Was proven effective for the intended role. An example of a Russian bunker buster is the KAB-1500L-Pr. It is delivered with the Su-24M and the Su-34 aircraft. It is stated to be able to penetrate 10–20 m of earth or 2 m of reinforced concrete. The bomb weighs 1,500 kg (3,300 lb), with 1,100 kg (2,400 lb) being the high explosive penetrating warhead. It is laser guided and has

6084-422: Was strongly questioned by experts and recommendations for "pure" concrete construction were made, using reinforced concrete for the floors and walls as well as the frames. In April 1904, Julia Morgan , an American architect and engineer, who pioneered the aesthetic use of reinforced concrete, completed her first reinforced concrete structure, El Campanil, a 72-foot (22 m) bell tower at Mills College , which

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