Misplaced Pages

#232767

73-868: The first luge competition took place on February 12, 1883, on a four-kilometer course between Davos and Klosters , Switzerland, with the co-winners from Australia and Switzerland having a time of 9 minutes, 15 seconds. Austria, Germany, and Switzerland founded the Internationaler Schlittensportsverband (ISSV - International Sled Sport Federation (in German) ) in 1913 in Dresden , Germany. The first European Luge Championships took place in Reichenberg , Bohemia (now Liberec , Czech Republic ) in 1914. World War I in Europe caused

146-602: A Winter Olympics competition, following speed skier Nicolas Bochatay , aged 27, who died while preparing for the Albertville 1992 games; and British luger Kazimierz Kay-Skrzypecki and skier Ross Milne , aged 19, who both died in the run-up to the Innsbruck 1964 games. The sport of luge is governed by the Fédération International de Luge de Course (FIL, International Luge Federation). The FIL

219-596: A centripetal acceleration of up to 5g. Men's Singles have their start locations near where the bobsled and skeleton competitors start at most tracks, while both the Doubles and Women's Singles competition have their starthouse located farther down the track. Artificial track luge is the fastest and most agile sledding sport. Natural tracks are adapted from existing mountain roads and paths. Artificially banked curves are not permitted. The track's surface should be horizontal. They are naturally iced. Tracks can get rough from

292-634: A fatal crash during his final practice run for the 2010 Winter Olympics on the Whistler Sliding Centre in Whistler, British Columbia , Canada . Hours later, the International Luge Federation concluded that the accident was caused by a steering error and not a track error; nevertheless, changes to the track were made before the re-opening. Kumaritashvili was the fourth athlete to die while in preparation for

365-445: A flat, aerodynamic position on the sled, keeping their heads low to minimize air resistance. They steer the sled mainly with their calves by applying pressure on the runners—right calf to turn left, left calf to turn right. It takes a precise mix of shifting body weight, applying pressure with calves and rolling the shoulders. There are also handles for minor adjustments. A successful luger maintains complete concentration and relaxation on

438-594: A luger must have strong neck, upper body, abdominal, and thigh muscles. Athletes also use wind tunnels to train. Strength training is essential to withstand the extreme G-forces of tight turns at high speeds. Since lugers have very little protection other than a visor and helmet, they must be able to endure the physical pounding administered by the track when mistakes are made. As with many extreme sports , luging has risks. Though most injuries involve bumps, bruises, broken bones and concussions, fatalities do occasionally occur. Georgian luger Nodar Kumaritashvili suffered

511-453: 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

584-563: A position he held until 2020. In reaction to the 2022 Russian invasion of Ukraine , in March 2022 the FIL banned all Russian athletes, coaches, and officials from its events, suspended all Russian officials appointed to its Commissions and Working Groups, and deemed Russia ineligible to host any of its events. Also in response to the Russian invasion of Ukraine, Russian Luge Federation's Natalia Gart

657-419: 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,

730-426: 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

803-521: Is 360 meters long, and is open to the public through winter. World championships have been held since 1979 while European championships have been held since 1970 . In season 2015/16 FIL started with the Junior Worldcup . There are five luge disciplines. These are further broken into several age classes - multiple youth and junior classes that cover the range of age 7–20, and general class (ages 21 and older). Older competitors may enjoy

SECTION 10

#1732771904233

876-658: 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

949-427: Is a small one- or two-person sled on which one sleds supine (face-up) and feet-first. A luger begins seated, propelling themselves initially from handles on either side of the start ramp, then steers by using the calf muscles to flex the sled's runners or by exerting opposite shoulder pressure to the pod. Racing sleds weigh 21–25 kg (46–55 lb) for singles and 25–30 kg (55–66 lb) for doubles. Luge

1022-503: Is also the name of an Olympic sport that employs that sled and technique. It is not to be confused with skeleton bob, which is also a single person tray-like sled in the Bobsleigh family, and the name of the sport that uses that sled, but which is designed for a running start, steering by shoulders and feet, and to be laid on face down and head first. While skeleton and bobsleigh are part of one international federation and sport, luge

1095-588: Is based in Salzburg , Austria, and includes 53 member nations. It has traditionally had a dominant number of German-speaking representatives. The following persons have been president of the FIL: Up to: 2022 Up to: 2022 Up to: 2022 Up to: 2022 Up to: 2022 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

1168-528: 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

1241-504: 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

1314-541: 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

1387-428: 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

1460-430: 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

1533-466: Is organised separately by the International Luge Federation, FIL . Lugers can reach speeds of over 140 km/h (87 mph), and is the fastest of the three 'sliding' sports. Austrian Manuel Pfister reached a top speed of 154 km/h (96 mph) on a track in Whistler , Canada , prior to the 2010 Winter Olympics . Lugers compete against a timer in one of the most precisely timed sports in

SECTION 20

#1732771904233

1606-579: 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

1679-446: 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

1752-544: The Sliding Center Sanki , will be in use for the 2014 Winter Olympics , had construction started in May 2009 following controversies at a previous location over track start heights and it being near World Heritage Site , including near an endangered species of brown bear . Natural tracks are tracks adapted from existing mountain roads and paths, including a horizontal track surface and natural track icing. Most of

1825-431: The bobsleigh , originated in the health-spa town of St Moritz , Switzerland , in the mid-to-late 19th century, through the endeavours of hotel entrepreneur Caspar Badrutt . Badrutt successfully sold the idea of winter resorting, as well as rooms with food, drink, and activities. His more adventurous English guests began adapting delivery boys' sleds for recreation, which led to collisions with pedestrians as they sped down

1898-468: 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

1971-719: 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

2044-697: 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

2117-607: 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

2190-718: The ISSV operations to be suspended and prevented any additional competitions until 1927. In 1927, the ISSV was reestablished with the second European Luge Championships taking place in Schreiberhau , Germany (now Szklarska Poręba , Poland) the following year with a women's competition included. The ISSV was absorbed into the Fédération Internationale de Bobsleigh et de Tobogganing (FIBT - International Bobsleigh and Tobagganing Federation (in French) ) in 1935 and

2263-649: The United States. The Upper Peninsula Luge Club in Negaunee, Michigan , is the only natural luge track in the United States. The over 800 meter (half-mile) track features 10 full corners along its 88-meter (289 ft) vertical drop. Canada has tracks in Camrose , Hinton Luge , Alberta , Calgary and Ontario Luge Club. The track in Naseby, New Zealand is the only one in the southern hemisphere . The track

International Luge Federation - Misplaced Pages Continue

2336-695: 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

2409-461: 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

2482-539: The alkalinity of 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

2555-564: The athlete's body weight). Men's singles on most tracks have their start house close to the bobsleigh and skeleton start locations while both the men's doubles and women's singles have their start house located further down the track. As of 2009, there are sixteen bobsleigh, luge, and skeleton artificial tracks worldwide with a 17th track near Moscow that will host Junior World Cup events in November 2009. Another track in Russia near Sochi ,

2628-479: 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

2701-636: The braking and steering action. Athletes use a steering rein, put out their hands and use their legs in order to drive around the tight corners. Braking is often required in front of curves and is accomplished by the use of spikes built on the bottom of the shoes. Tracks have a slope of not more than 15%. Most of the tracks are situated in Austria and Italy, with others in Germany, Poland, Russia, Slovenia, Switzerland, Croatia, Liechtenstein, France, Turkey, Sweden, Norway, Romania, Slovakia, New Zealand, Canada and

2774-543: 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

2847-756: 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

2920-422: 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

2993-541: 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

International Luge Federation - Misplaced Pages Continue

3066-412: 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

3139-416: 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

3212-403: 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

3285-403: 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,

3358-714: The first World Luge Championships were held at Holmenkollen near Oslo , Norway . The FIL was established in Switzerland in 1957 with membership granted into the IOC at their congress in Sofia , Bulgaria that same year. Bert Isatitsch of Austria was elected President of the FIL. At the 1959 IOC meeting in Munich , West Germany , luge was approved for inclusion into the 1964 Winter Olympics in Innsbruck with competitions taking place in neighboring Igls . 12 nations took part in

3431-529: The first natural track World Championships took place in Inzing , Austria in 1979. The first Junior World Championships on artificial track took place at Lake Placid, New York , United States three years later. Isatitich died suddenly on February 8, 1994, and then Vice-President for Sport Josef Fendt took over as Acting President. Fendt would be named president at the FIL congress in Rome, Italy later that year,

3504-548: The first Winter Olympic luge competitions with timing taking place in 1/100ths of a second. Following a tie in the men's doubles competition between East Germany and Italy at the 1972 Winter Olympics in Sapporo , Japan, the FIL began timing all of their competition in 1/1000ths of a second, a practice that continues as of 2009. The first natural track European championships took place in Kapfenberg , Austria in 1970 while

3577-505: 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

3650-511: 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

3723-480: The inclusion of reinforcement having higher tensile strength or ductility. The reinforcement 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,

SECTION 50

#1732771904233

3796-660: 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

3869-638: The lanes and alleys of the village. The first organized meeting of the sport took place in 1883 in Switzerland . In 1913, the Internationale Schlittensportverband or International Sled Sports Federation was founded in Dresden , Germany . This body governed the sport until 1935, when it was incorporated in the Fédération Internationale de Bobsleigh et de Tobogganing (FIBT, International Bobsleigh and Tobogganing Federation). After it had been decided that luge would replace

3942-824: 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

4015-438: 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

4088-656: 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

4161-680: The over 60 tracks are located in Austria, Italy, Germany, Poland, Canada, the United States, Liechtenstein, Switzerland, Croatia, Russia, Norway, Sweden, Finland, Turkey, Romania, Bulgaria, New Zealand and Slovenia . In 2004, the FIL established a Hall of Fame for the greatest competitors in luge. As of 2008, there have been a total of six inductees. Since its founding in 1957, FIL has had three presidents, Bert Isatitsch from Austria (1957–94), Josef Fendt from Germany (1994–2020), and Einars Fogelis (2020-current) from Latvia. 53 nations in June 2021: Results: Luge A luge / l uː ʒ /

4234-448: 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

4307-433: 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

4380-581: 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

4453-407: The sled while travelling at high speeds. Fastest times result from following the perfect "line" down the track. Any slight error, such as brushing against the wall, costs time. Track conditions are also important. Softer ice tends to slow speeds, while harder ice tends to lead to faster times. Lugers race at speeds averaging 120–145 km/h (75–90 mph) around high banked curves while experiencing

SECTION 60

#1732771904233

4526-413: The sport in masters (age 30–50), and senior masters (age 51+) classes. In a team relay competition, one man, one woman, and a doubles pair form a team. A touchpad at the bottom of the run is touched by a competitor signaling a teammate at the top of the run to start. Rules and procedures for races are very precise: The sport of luge requires an athlete to balance mental and physical fitness. Physically,

4599-585: The sport of skeleton at the Olympic Games , the first World Championships in the sport were held in 1955 in Oslo ( Norway ). In 1957, the Fédération Internationale de Luge de Course (FIL, International Luge Federation) was founded. Luge events were first included in the Olympic Winter Games in 1964 . Americans were slow to adopt the sport of luge. The first luge run in North America

4672-474: 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

4745-454: 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

4818-403: 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

4891-560: The world—to one millisecond on artificial tracks. The first recorded use of the term "luge" dates to 1905 and derives from the Savoy / Swiss dialect of the French word luge , meaning "small coasting sled". The practical use of sleds is ancient and widespread. The first recorded sled races took place in Norway sometime during the 15th century. The sport of luge, like the skeleton and

4964-531: Was built at Lolo Hot Springs, Montana , in 1965. Although the United States competed in every Olympic luge event from 1964 through 1976, it was not until 1979 that the United States Luge Association was founded. The first artificial American track was completed in that year for use in the 1980 XIII Winter Olympic Games at Lake Placid, New York. Since that time the United States luge program has greatly improved. A second artificial track

5037-638: Was constructed near Park City, Utah , for the 2002 XIX Olympic Winter Games at Salt Lake City. Caitlin Nash and Natalie Corless, both of Canada, became the first all-female team to compete in a Senior World Cup doubles race in luge in 2019. Artificial luge tracks have specially designed and constructed banked curves plus walled-in straights. Most tracks are artificially refrigerated, but artificial tracks without artificial cooling also exist (for example, in St. Moritz ). Tracks tend to be very smooth. The athletes ride in

5110-948: Was expelled from the FIL Executive Board. The FIL governs competitions on artificial tracks and natural tracks at both the European and World Championship levels. At the Winter Olympics, only artificial track competitions are contested. The events at the European and World Championships are men's singles, men's doubles, women's singles, and a team event consisting of one run each from men's singles, men's doubles, and women's singles. Artificial tracks are tracks that have their curves specifically designed and banked with walled-in straightaways. Made of reinforced concrete and cooled with ammonia refrigeration , these tracks are smooth and have g-forces of up to 4g (Four times

5183-404: 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

5256-518: Was part of the "Section de Luge" until the early 1950s. At a 1954 International Olympic Committee (IOC) meeting in Athens, Greece, it was determined that luge would replace skeleton as a Winter Olympic discipline. Skeleton, which had been a sport both at the 1928 and 1948 Winter Olympics , would not return as an Olympic sport until the 2002 Winter Olympics in Salt Lake City . In 1955,

5329-422: 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

#232767