Reinforced concrete: Difference between revisions

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 [[New York and Long Island Coignet Stone Company Building|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>

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”"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>

Because 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 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 <ref>{{Cite journal|title=Monotonic and Cyclic Seismic Analyses of Old-Type RC Columns with Short Lap Splices|journal=Construction Materials|date=31 March 2024|volume=4|issue=2|pages=329–341|last1=Megalooikonomou|first1=Konstantinos G.|doi=10.3390/constrmater4020018 |doi-access=free }}</ref> 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 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 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.<!-- [[American Concrete Institute|ACI]] 440 provides information about properties and design of FRP reinforced concrete structures. The Canadian [[Canadian Standards Association|CSA]] 806 and 807 providing the same information in form of a real standard. In addition the Canadian Highway Design Code is the first standard allowing for composites in bridge construction. -->

{{Main|Fiber -reinforced concrete}}

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&nbsp;mm diameter, 45&nbsp;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>Fiber Concrete in Construction , Wietek B. , Springer 2021 , pages 268 ; ISBN 978-3-658-34480-1</ref>

* [[Cover Metermeter]]

* [[Interfacial Transitiontransition Zonezone]]