Earlier This Year, the Concrete Reinforcing
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arlier this year, the Concrete Reinforcing codification of the newly available material. The Structural Steel Institute (CRSI) published A rise of manufacturing, and the associated need for Comprehensive and Invaluable Treatise on warehousing to accommodate product distribu- all Forms of Steel Reinforcement Employed tion, brought higher floor loads and the desire for Ein the Design and Construction of Reinforced Concrete bigger buildings. Likewise, fire and conflagration ForenSicS of Long Ago. The majority of the book is an exten- drove owners to seek “fireproof” construction, sive catalogue of no less than 47 different types of which concrete was able to provide. steel reinforcing bars (four of which fall under the Now, about 100 years later, many of these build- investigating structures category of “Miscellaneous”), seven types of welded ings are being repurposed and retrofitted for reuse, and their components wire fabric, 22 systems of beam and girder rein- a trend driven in part by state and federal tax cred- forcement, 12 systems of column reinforcement, its for historic rehabilitation. Today’s structural 11 slab systems and six bridge systems. consultants are practicing at the confluence of two The supporting sections of the book, includ- trends, each at opposite ends of the century, which ing a brief history of early concrete mix design converge on a general deficit of understanding and as well as historic ASTM bar specifications, are available information. Students of engineering secondary compared to the bar descriptions and and historic preservation,® as well as researchers images. Appendices are similar compendiums in the small but growing field of construction of reinforcing steel illustrations; for example, history, may also find useful information and Appendix E contains 31 patent drawings, references in the book. extending from Thaddeus Hyatt’s revolutionary pavement reinforcing issued in 1878 to latecomer Researching Reinforced Concrete CopyrightJ.T. Simpson’s visually interesting “deformed Developing enough understanding of an early bar” of 1922. Appendix concrete structure to analyze it for reuse can Introducing and Using F contains images of over require a substantial amount of research, unless CRSI’s New “Treatise” 30 early advertisements. assumptions are made – potentially at the ulti- Appendix G paraphrases mate expense of the project, or loss of historic the “Alphabetical List material. Certainly, knowledge of early reinforced Vintage Steel Reinforcement of the 144 Foreign Systems of Reinforced concrete does not replace investigation, analysis, in Concrete Structures Concrete Construction, with the Addresses of or engineering judgment; but effectively plan- the Inventor or Owner of Each System, and a ning and implementing a search for supporting Concise Description of Its Special Features” and relevant sources of information may result By Meghan Elliott, P.E., from Reinforcedmagazine Concrete in Europe by A. L. in the difference between a cost-effective and a Associate AIA S TColby Rin 1909. U C T Ucost-prohibitive R projectE approach. This new resource for structural engineers fits These sources can very generally be thought of in into, but is distinctly different from, the expand- two categories: primary and secondary. Primary ing collection of reference materials that have sources are those that are typically contempo- been produced by professional organizations. rary to the topic and representative of the query: First, it builds on and replaces CRSI’s earlier patents, advertisements, earlier building codes, Meghan Elliott, P.E., Associate publications: its initial reference, Evaluation of and historic newspaper or trade articles about a AIA ([email protected]), Reinforcing Steel Systems in Old Concrete Structures particular engineer, product, or analytical method is the founder and a principal (1981), and its abridged version as Engineering (Figure 1). Secondary sources are used to establish at Preservation Design Data Report No. 48, Evaluation of Reinforcing the context, and place the question within the Works (PVN), a historic Bars in Old Concrete Structures (2001). These broader research and academic understanding preservation consulting firm focused on summaries of industry trends in of the topic. Secondary sources typically include in Minneapolis, Minnesota. terms of material strength, specifications, and current books, journal articles, literature reviews, general availability of materials. This new pub- or even textbooks. Both types of sources are typi- lication is similar in function and potential use cally needed to understand a building structure. to the American Institute of Steel Construction’s While the CRSI publication might initially be (AISC) Design Guide 15, AISC Rehabilitation considered a secondary source, especially given the and Retrofit Guide: A Reference for Historic Shapes authors’ choice of the word “treatise,” it may be and Specifications. more successfully used as a collection of reprinted The need for this type of reference is a result primary sources. of the convergence of several trends in the his- A small but growing collection of second- tory and contemporary practice of structural ary sources is available to understand early engineering. First, there was an explosive devel- reinforced concrete. Some recent publications opment of reinforced concrete technology in include Donald Friedman’s Historical Building the United States during the approximate time Construction: Design, Materials & Technology period from 1890 to 1920. This proliferation of (2010), Amy Slaton’s Reinforced Concrete and the new products coincided with a rise in demand Modernization of American Building, 1900-1930 for industrial buildings, but preceded the formal (2001), and Andrew Saint’s Architect and Engineer: 10 September 2014 STRUCTURE magazine key factors. First, structural steel had a head start of several decades. For example, wrought- iron use as structural framing began before the 1870s, and the basics of steel framing were in place before 1900. The use of reinforced concrete for buildings, on the other hand, was mostly a post-1900 trend. Not coincidentally, structural engineers as a separate consulting practice and resource for architects were rapidly evolving at the same time: the introduction of reinforced concrete as a building material coincided with a new professional field of structural engineering. According to Friedman, the use of steel fram- ing was not an analytical leap from traditional wood building methods. Builders and archi- ® tects could easily make a rational switch from a stick of wood to a stick of steel: while steel Figure 1. An example of a primary resource was a substantially stronger material, it fol- for researching concrete, the William lowed the same beam theory and acted the B. Hough Company advertisement for same in bending and compression. “M/B Special Open Hearth Bars” lists the Concrete, onCopyright the other hand, required an buildings in which the product was used. analytical shift to integrate the new system Image from Cement Age, December, 1911, into buildings, from a system of pieces to and digitized by Google Books. monolithic construction and the interaction of two distinct materials. Engineers and build- Figure 2. Excerpt of Ernest Ransome’s patent for A Study in Sibling Rivalry (2007). These books ers were thus using the material before it was twisted square reinforcement. The M/B Bar of can be supplemented by earlier analyses of understood. Many of the proprietary products Figure 1 uses a similar method for mechanical concrete history, such as articles and books appear as an attempt to rationalize what was adhesion of the concrete to the steel. Digitized by by Carl W. Condit, a good example of which already being built through experimentation Google Patents. is “The First Reinforced Concrete Skyscraper: and intuition. The Ingalls Building in Cincinnati and Its The evolution of reinforced concrete design strengthen the concrete with steel rods located Place in Structural History” (1968), pub- in themagazine United States was driven by a small to take the tensile stresses. In all cases, the steel lished in the journal TechnologyS and CultureT . Rgroup of Uentrepreneurial C individuals,T U as reinforcement R wasE placed in two directions Other secondary sources are too numerous compared to the relatively consistent and and tied with wires, the rods in one direction to list here, but include journal articles and nationwide acceptance and distribution of designated as carrying rods and those in the trade publications, like the Association for steel framing products. As a result, regional other as distributing rods. For slabs poured Preservation Technology’s (APT) Bulletin and differences occurred, as well as leaps in the continuously over supports, the rods were the journal or proceedings of the American distribution of different products and sys- placed at the top of the slab; i.e., the correct Concrete Institute (ACI). tems. While there were earlier contributions reinforcing pattern for continuity. by William Ward and Thaddeus Hyatt, the In practice, the expansion of the use of Early Reinforced Concrete momentum of innovation in reinforced con- monolithic concrete in the US was substan- crete in the US began with Ernest Ransome. tially instigated by several engineers and The early history of reinforced concrete in From his practice in San Francisco, he intro- builders. In addition to Ransome, other the United States is very different from that