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'''Reinforced concrete''', also called '''ferroconcrete''', is a [[composite material]] in which [[concrete]]'s relatively low [[ultimate tensile strength|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 bars ([[rebar]]) and is usually embedded passively in the concrete before the concrete sets. However, [[
==Description==
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[[File:Expo58 building Philips.jpg|thumb|The novel shape of the [[Philips Pavilion]] built in [[Brussels]] for [[Expo 58]] was achieved using reinforced concrete]]
[[Leaning Tower of Nevyansk]] in the town of [[Nevyansk]] in [[Sverdlovsk Oblast]], [[Russia]] is the first building known to use reinforced concrete as a construction method.{{
François Coignet used iron-reinforced concrete as a technique for constructing building structures.<ref name="britannia">{{cite encyclopedia |url=https://www.britannica.com/technology/building-construction/Early-steel-frame-high-rises#ref105155 |title=Building construction: The invention of reinforced concrete |url-access=subscription |encyclopedia=Encyclopedia Britannica |access-date=2018-09-27 |archive-date=2018-09-28 |archive-url=https://web.archive.org/web/20180928005354/https://www.britannica.com/technology/building-construction/Early-steel-frame-high-rises#ref105155 |url-status=live }}</ref> In 1853, Coignet built the first iron reinforced concrete structure, a four-story house at 72 [[rue Charles Michels]] in the suburbs of Paris.<ref name="britannia" /> 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.<ref name="Condit">{{cite journal |last=Condit |first=Carl W. |journal=Technology and Culture |title=The First Reinforced-Concrete Skyscraper: The Ingalls Building in Cincinnati and Its Place in Structural History |date=January 1968 |volume=9 |issue=1 |pages=1–33 |doi=10.2307/3102041 |jstor=3102041|s2cid=113019875 }}</ref> The Pippen building in [[New York and Long Island Coignet Stone Company Building|Brooklyn]] stands as a testament to his technique. In 1854, English builder William B. Wilkinson reinforced 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.<ref>{{cite web | url =http://www.theconcreteproducer.com/Images/The%20History%20of%20Concrete%2C%20Part%202_tcm77-1306954.pdf | title =History of Concrete | year =1995 | author =Richard W. S | publisher =The Aberdeen Group | access-date =25 April 2015 | archive-url =https://web.archive.org/web/20150528183822/http://www.theconcreteproducer.com/Images/The%20History%20of%20Concrete%2C%20Part%202_tcm77-1306954.pdf | archive-date =28 May 2015 | url-status =dead | df =dmy-all }}</ref><ref>{{cite web| url = http://www.jfccivilengineer.com/reinforced_concrete.htm| title = Reinforced Concrete| work = The Elements of Structure| year = 1995| author = W. Morgan| via = John F. Claydon's website| access-date = 25 April 2015| archive-date = 12 October 2018| archive-url = https://web.archive.org/web/20181012133730/http://www.jfccivilengineer.com/reinforced_concrete.htm| url-status = live}}</ref><ref name="CIVL1101">{{cite web |url= http://www.ce.memphis.edu/1101/notes/concrete/section_2_history.html |title= History of Concrete Building Construction |year= 2015 |website= CIVL 1101 – History of Concrete |author= Department of Civil Engineering |publisher= University of Memphis |access-date= 25 April 2015 |archive-date= 27 February 2017 |archive-url= https://web.archive.org/web/20170227213256/http://www.ce.memphis.edu/1101/notes/concrete/section_2_history.html |url-status= live }}</ref>
[[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.<ref>{{cite book |last=Day |first=Lance |title=Biographical Dictionary of the History of Technology |url=https://archive.org/details/isbn_9780415060424 |url-access=registration |page=[https://archive.org/details/isbn_9780415060424/page/284 284] |publisher=Routledge |year=2003 |isbn=0-203-02829-5}}</ref> He 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 the [[Ultimate tensile strength|tensile strength]] of concrete was improved by the reinforcing.<ref name=Mörsch>{{cite book |last=Mörsch |first=Emil |title=Concrete-steel Construction: (Der Eisenbetonbau) |year=1909 |publisher=The Engineering News Publishing Company |pages=
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. [[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 behavior of reinforced concrete. His work played 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.<ref name="Condit"/><ref>{{cite book| last=Collins| first=Peter| title=Concrete: The Vision of a New Architecture| date=
[[Ernest L. Ransome]], an English-born engineer, was an early innovator of reinforced concrete techniques at the end of the 19th century. Using 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.<ref>{{cite web| last1=Mars| first1=Roman| title=Episode 81: Rebar and the Alvord Lake Bridge| url=http://99percentinvisible.org/episode/episode-81-rebar-and-the-alvord-lake-bridge/| publisher=99% Invisible|date=7 June 2013 |access-date=6 August 2014|archive-date=8 August 2014|archive-url=https://web.archive.org/web/20140808074102/http://99percentinvisible.org/episode/episode-81-rebar-and-the-alvord-lake-bridge/| url-status=live}}</ref> Gaining increasing fame from his concrete constructed buildings, Ransome was able to build two of the first reinforced concrete bridges in North America.<ref>{{cite book| last=Collins| first=Peter| title=Concrete: The Vision of a New Architecture| date=1920–1981| publisher=McGill-Queen's University Press| isbn=0773525645| pages=
[[:de:Gustav Adolf Wayss|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, [[:de:Wayss & Freytag|Wayss & Freytag]], made the first commercial use of reinforced concrete. Up until 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.<ref name=Mörsch/>
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One of the first [[skyscraper]]s made with reinforced concrete was the 16-story [[Ingalls Building]] in Cincinnati, constructed in 1904.<ref name=CIVL1101/>
The first reinforced concrete building in Southern California was the [[Homer Laughlin Building|Laughlin Annex]] in downtown [[Los Angeles]], constructed in 1905.<ref>{{Cite book |title=Los Angeles from the Mountains to the Sea |volume=2 |last=McGroarty |first=John Steven |publisher=American Historical Society |year=1921 |location=Los Angeles, CA |page=176 |access-date=2017-11-29 |archive-date=2016-08-09 |archive-url=https://web.archive.org/web/20160809190406/https://books.google.com/books?id=YmUUAAAAYAAJ |url-status=live }}</ref><ref>{{Cite book |title=Annual Report of the City Auditor, City of Los Angeles, California for the Year Ending June 30 |publisher=Los Angeles City Auditor |year=1905 |location=Los Angeles, CA |pages=
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 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.<ref>{{Cite magazine |author1=Austin, J. C. |author2=Neher, O. H. |author3=Hicks, L. A. |author4=Whittlesey, C. F. |author5=Leonard, J. B. |date=November 1906 |title=Partial Collapse of the Bixby Hotel at Long Beach |url=https://books.google.com/books?id=17dCAQAAMAAJ&pg=PA44 |magazine=Architect and Engineer of California |volume=VII |issue=1 |pages=44–48 |access-date=2018-05-29 |archive-date=2020-09-20 |archive-url=https://web.archive.org/web/20200920184843/https://books.google.com/books?id=17dCAQAAMAAJ&pg=PA44 |url-status=live }}</ref>
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{{Main|Prestressed concrete}}
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, 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.<ref>{{Cite book|url=https://www.worldcat.org/oclc/20693897|title=Structural materials|
== Common failure modes of steel reinforced concrete ==
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Fiber reinforcement is mainly used in [[shotcrete]], but can also be used in normal concrete. Fiber-reinforced normal concrete is mostly used for on-ground floors and pavements, but can also be considered for a wide range of construction parts (beams, pillars, foundations, etc.), either alone or with hand-tied rebars.
Concrete reinforced with fibers (which are usually steel, [[glass]], [[Fiber-reinforced plastic|plastic fibers]]) or cellulose polymer fiber is less expensive than hand-tied rebar.{{Citation needed|date=December 2017}} The shape, dimension, and length of the fiber are important. A thin and short fiber, for example short, hair-shaped glass fiber, is only effective during the first hours after pouring the concrete (its function is to reduce cracking while the concrete is stiffening), but it will not increase the concrete tensile strength. A normal-size fiber for European shotcrete (1 mm diameter, 45 mm length—steel or plastic) will increase the concrete's tensile strength. Fiber reinforcement is most often used to supplement or partially replace primary rebar, and in some cases it can be designed to fully replace rebar.<ref>
Steel is the strongest commonly available fiber,{{Citation needed|reason=I thought Aramid fibers were stronger, need a reliable source for this statement as it may not be fact based or is out-of-date.|date=December 2017}} and comes in different lengths (30 to 80 mm in Europe) and shapes (end-hooks). Steel fibers can only be used on surfaces that can tolerate or avoid corrosion and rust stains. In some cases, a steel-fiber surface is faced with other materials.
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