64-406: Julius Kahn may refer to: Julius Kahn (inventor) (1874–1942), engineer of reinforced concrete Julius Kahn (congressman) (1861–1924), United States congressman [REDACTED] Topics referred to by the same term This disambiguation page lists articles about people with the same name. If an internal link led you here, you may wish to change
128-453: 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
192-419: 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,
256-725: 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 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
320-426: 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
384-415: 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 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
448-658: 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
512-528: 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
576-504: 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
640-541: 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
704-428: 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
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#1732801020438768-430: 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
832-579: 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
896-446: 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
960-604: The Eastman Kodak Building in Rochester, New York , gave way. Investigations of both accidents found the quality of workmanship seriously at fault. Both queries came to the conclusion that the Kahn system was not to blame for either faulty design or errors; rather, poor construction techniques were responsible. Trussed Concrete Steel Company manufactured a product with a brand name of Hy-Rib starting in 1909. It
1024-644: The Union Bridge Company of New York. He worked as an engineer for both the United States Navy and the U.S. Army Corps of Engineers from 1896 to 1903. Kahn also was employed by C. W. Hunt Company of New York. In 1900, Kahn moved to Japan for two years, laboring in engineering, construction, and maintenance of iron and sulfur mines. Kahn returned to Detroit in 1903, joining Albert Kahn Associates , an architectural firm founded by his brother Albert in 1895. Kahn's first assignment
1088-468: 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
1152-719: 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
1216-565: The Calumet and Hecla Mining Company" in 1889. Kahn experimented and developed reinforced concrete construction materials, with at least 75 patented inventions in the field by 1934. His first patent was "Kahn Trussed Bar", also called "the Kahn Bar" or "Kahn Bar System", patented in 1903. The Kahn bar was a straight steel beam whose edges were slightly bent, resulting in improved stress distribution "wings" that increased tension strength. It
1280-697: 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
1344-607: 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
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#17328010204381408-539: The U.S. Army Corps of Engineers. During the construction of U.S. War College building in Washington, D.C., he initiated methods improving the then existing technology of reinforced concrete by beginning work developing the Kahn system of steel bars. This new concept for reinforced concrete steel bars was the basis of the steel production company he later founded. Kahn understood the structural challenges inherent in
1472-695: 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
1536-461: 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
1600-580: The architectural breakthroughs of the 20th century. Many named the 1905 Packard Motor Car Company’s building No. 10 in Detroit as the first edifice built for the largest and most swiftly growing industry in the early 1900s. Albert Kahn was the designer and architect for this use of the Kahn system in construction devoted entirely to the car. However, the first was actually the Cadillac Motor Car plant in Detroit. Ironically, Julius Kahn supervised
1664-479: 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
1728-543: 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
1792-756: 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
1856-512: The company. For example, employee David H. Morgan was financially rewarded for inventing a new type of airplane hangar door, subsequently manufactured by Truscon. The Kahn system of reinforced concrete was adapted by his brother Albert Kahn , an architect, for design and construction of industrial buildings. By 1939, Kahn's system was used in 134 U.S. cities and was adopted by builders in Africa, Europe, Canada, China, Brazil, and Mexico. The system
1920-422: 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
1984-541: 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
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2048-412: 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
2112-416: 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
2176-403: 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
2240-592: The engineering and construction of both buildings, using his patented system to make essential contributions to the construction and automotive industries in the US. There were two significant construction accidents in buildings using the Kahn system in the early 20th century. The first, in November 1906, occurred in Long Beach, California , when parts of the Bixby Hotel collapsed during construction. Also, that November,
2304-403: 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,
2368-526: The existing method of concrete reinforcement used at the end of the nineteenth century. The main problem was slippage of the steel within the hardened concrete, which weakened the structure. He experimented in his brother's basement, where he developed an improved type of reinforced beam called "the Kahn Bar". Kahn patented his invention in 1903, the first of more than 75 patents awarded to him. The Jordahl (Jordahl GmbH) Company’s founders, Norwegian Anders Jordahl and his Swedish partner Ivar Kreuger , acquired
2432-568: 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
2496-511: 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
2560-707: The ideal location because the city's proximity to steel production in Mahoning County and reduced shipping costs. Kahn served as a director of the Mahoning Bank, the First National Bank, and Dollar Bank. In 1927, he was elected chairman of the Youngstown Chamber of Commerce grade elimination committee, and a director of the street car committee in 1928. He was the president of an eponymous realty firm in Detroit. In 1930, Kahn
2624-660: 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
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2688-824: 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
2752-436: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Julius_Kahn&oldid=932924131 " Category : Human name disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Julius Kahn (inventor) Julius Kahn (March 8, 1874 – November 4, 1942)
2816-552: The marketing rights to the Kahn system in Europe in 1907. Today, the company attributes the “… seeds of its founding …” to Albert and Julius Kahn’s passion for concrete. Kahn formed Trussed Concrete Steel Company (Truscon) to manufacture his beams. He was the president, but spent much of his time in the design room. The company was headquartered in Detroit, with manufacturing in Youngstown, Ohio . Kahn chose Youngstown in 1907 as
2880-438: 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
2944-656: 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
3008-448: 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
3072-433: 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
3136-581: 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
3200-474: 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
3264-454: 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
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#17328010204383328-403: 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
3392-655: Was a steel meshed sheathing with deep stiffening ribs. It was filled with cement or plaster and used for floors, walls, and ceilings of houses, factories, and commercial buildings. It was a product derived from the Kahn Trussed Bar for beams and columns of reinforced concrete. Hy-Rib products were also used in the construction of tunnels , conduits , flumes , culverts , silos , cisterns , chimneys , and water tanks . Its technology cut down on labor time in construction. Kahn married Margaret K. Kohut, daughter of rabbi Alexander Kohut , on December 23, 1903. Margaret
3456-443: Was an American engineer, industrialist, and manufacturer. He was the inventor of the Kahn system , a reinforced concrete engineering technique for building construction. The Kahn system, which he patented in 1903, was used worldwide for housing, factories, offices and industrial buildings. He formed his own company, Trussed Concrete Steel Company , as a manufacturing source for his inventions. He also founded United Steel Company and
3520-650: Was born in Hungary in 1876; later, her family immigrated to the US. The Kahns had three children: Gisela Kahn Gresser (1906–2000), Katherine Kay (1909–1954), and Julius Kahn Jr. (1912–2009), all born in Detroit. Kahn enjoyed a one-year retirement "to private life" in 1939. In 1940, he exited retirement and became an executive of another steel fabricating company. Kahn died at the age of 68 of pneumonia on November 4, 1942, in Cleveland , Ohio. Reinforced concrete Reinforced concrete , also called ferroconcrete ,
3584-526: Was chairman of Truscon Laboratories . Kahn was born in Münstereifel, Germany , March 8, 1874. He immigrated to the United States with his family in 1880, entering at the port of Baltimore , Maryland, where they briefly lived. They continued to Detroit , Michigan, where he was raised, along with five brothers and two sisters. Their father Joseph (1860–1924) was a rabbi and ran a restaurant where Julius worked; he also sold newspapers. Mother Rosalie
3648-530: Was collaborating with key architect Ernest Wilby in Ann Arbor on the University of Michigan's new College of Engineering building. Kahn's focus was testing specific materials for sufficient strength in supporting the new building. Kahn and Wilby wanted to use reinforced concrete for the building's floors, in place of traditional wood supports. Kahn had previous experience in reinforced concrete with
3712-404: 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
3776-588: Was honorary chairman of the Allied Jewish financial campaign. He was also a member of several committees in metal-related industries as well as a member of the proxy committee that opposed the merger of Youngstown Sheet & Tube Company with Bethlehem Steel. Kahn was the founder of United Steel Company in Wooster, Ohio , and chairman of Truscon Laboratories in Detroit. He was president of Truscon Steel Company from its inception in 1905 until 1935, when it
3840-663: Was skilled in music and art. Kahn's elementary education was in Detroit Public Schools . He completed the normal four-year high school curriculum in three years. Kahn, assisted financially by his older brother, architect Albert , attended the University of Michigan . He received a Bachelor of Science and a degree in Civil Engineering in 1896. After graduating from the University of Michigan, Kahn began his career as an engineering draftsman for
3904-422: 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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#17328010204383968-488: Was taken over by Republic Steel Corporation . He then became a vice president for Republic, serving until 1939. Kahn wrote several published articles on engineering and on the steel business. One article titled "Confidence and cooperation", discussed the ills of industry. Kahn was also a member of the American Society of Civil Engineers , which awarded him The Collingwood Prize for his paper "The Coal Hoists of
4032-549: Was the principal product of the Trussed Concrete Steel Company, although the company manufactured many prefabricated steel products, as well as complete buildings — all used in construction around the world. Kahn's co-workers noted that he would stop whatever he was doing to write down an idea immediately, no matter what else was engaging him. Additionally he encouraged Truscon employees with financial incentives to develop new and improved ideas to benefit
4096-455: Was used in the first two automobile factories in the U.S., Packard and Cadillac , progenitors of the most prodigious industry of the 20th century. His unique engineering and construction method was also found in airplane plants, warehouses, docks, foundries, creameries, filtration plants, rubber factories, steel plants, silos, distilleries, smelters, and textile mills. The steel-reinforced concrete automobile factory has been heralded as one of
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