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Thaddeus Hyatt Biography · Prof. Charles M. Spofford · February 19, 1913
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By Prof. Charles M. Spofford, Member Boston Society Of Civil Engineers.
[Read before the Society, February 19, 1913.]

It is the purpose of this paper to give a brief description of an American, Mr. Thaddeus Hyatt, who was one of the earliest users of reinforced concrete, and who has not received as yet the credit to which the writer believes him entitled.
Mr. Hyatt was a lawyer by education but an inventor by nature. He was born in New Jersey in 1816, but lived most of his life in New York City and London. One of his early inventions was an illuminated sidewalk grating, the use of which first made it possible to light the basement areas under the sidewalks of New York City, thereby adding materially to property values. The Hyatt grating is still made. The manufacture of these gratings soon proved sufficiently profitable to enable Mr. Hyatt to leave the conduct of this business in the hands of his managers and devote his own time and considerable money to experiments and study along other lines. Among many subjects which had long interested him was fireproof construction, he having early recognized that the unprotected iron then employed in so-called fireproof buildings was by no means fireproof. His use of Portland cement in conjunction with iron in the manufacture of gratings convinced him of the value of a combination of these materials both with respect to strength and resistance to fire, and he was led to experiment very extensively with such a combination.

Thaddeus Hyatt
Thaddeus Hyatt

In 1877 he published privately a book giving his views upon fireproof construction, together with results of tests of various combinations of iron and concrete. The title of this book is "An Account of Some Experiments with Portland Cement Concrete Combined with Iron as a Building Material with Reference to Economy in Construction and for Security against Fire in the Making of Roofs, Floors and Walking Surfaces."
Among the subjects which he investigated were the following:
The fireproof qualities of floors made of Portland cement and iron. The heat conduction power of concrete. The coefficient of elasticity of concrete. The strength of concrete beams with iron rods and bars embedded therein. The effect of quenching red hot concrete in cold water. The relative economy of solid floors of concrete with tension steel embedded therein as compared with floors composed of concrete and rolled beams.
The beam tests were made by Kirkaldy, the well-known testing engineer, and are very interesting. The figures accompanying this paper show some of many different combinations which he tested, and serve to indicate the wide scope of his experiments.

Specimens of Reinforced Concrete Beams Tested for Thaddeus Hyatt
Specimens of Reinforced Concrete Beams Tested for Thaddeus Hyatt

From the results of his studies and tests, Mr. Hyatt drew the following conclusions:
  1. That fireproof construction requires that all iron beams shall be absolutely surrounded by fireproof material.
  2. That Portland cement concrete is fireproof.
  3. That the bond between concrete and iron bars or rods is sufficient to develop the strength of the iron, and that such a combination is much more economical than one consisting of concrete and rolled beams.
  4. That the coefficients of expansion of iron and concrete are practically identical.
  5. That the ratio between the moduli of elasticity of concrete and wrought iron is about I to 20.
  6. That high concrete chimneys reinforced with metal extending upward and threaded upon wire hoops should be lighter, cheaper and stronger than unprotected chimneys.
  7. That concrete combined with tension iron may not only be used satisfactorily for buildings, but that this material should also be satisfactory for bridge construction, since such a bridge should be weather-proof, need no paint, and probably cost less for repairs.
Hyatt was so firmly convinced by these studies of the desirable qualities of reinforced concrete that he constructed a building on Farrington Road, London, in which he used much of this material. To convince others of its fireproof character, he built a fire in it without causing material damage. The building is still in use and has been visited by the writer.
A search through the records of the United States Patent Office shows that he was granted one patent of broad character covering the use of combinations of concrete and metal. This patent, No. 206112, was described as follows by the United States Patent Office Gazette of July 16, 1878.
Composition floors, roofs, pavements, etc.
"Brief.—Hydraulic cements and concretes are combined with metal bars and rods so as to form slabs, beams and arches. The tensile strength of the metal only is utilized by the position in which it is placed in the slabs, beams, etc.
"Claim.—The manufacture, use and application of the aforesaid materials, and the modes, means and processes connected therewith when the same are employed for the purposes and in the manner substantially as hereinbefore set forth and illustrated by my drawings."
The following portion of the original claim made by Hyatt is of particular interest as indicating the origin of the modern deformed bar, and in showing his knowledge of the importance of the shearing stresses in a reinforced concrete beam.
"Be it known that I, Thaddeus Hyatt, of No. 25 Waverly Place, in the City of New York, a citizen of the United States, have invented certain new and useful improvements in the use and application of hydraulic cements and concretes in combination with metal as a building material and in building constructions made therefrom, and in means, modes and processes connected therewith, the same being in part applicable to pavements and other walking and load bearing surfaces and structures.
"That iron or steel may be combined with concrete or with bricks as tie metal, capable of furnishing all tensile strength needed to balance the compressive resistance of the other materials when the beam or structure is subjected to bending stress, that all metal may be dispensed with save the tie only, and that both baked bricks and concrete possess in themselves cohesive power and strength sufficient to perform the functions ordinarily performed by the metallic web, are the discoveries made by me through many experiments and years of study, upon which I now base my application for a patent.
"In applying my invention to the construction of floors and other walking surfaces, and low-bearing structures, and to roofs, to the making of beams, joists, girders and supports, and to the making of pavement slabs not liable to crack from their own weight by the giving way of imperfect foundations underneath them, and to the construction of 'roof-pavements,' for extending the basements of buildings under the footways of public streets, my improvement consists in the use and application of iron or steel as tie metal, combined with the concrete or bricks, to give tensile power to the same; my invention, with respect to the tie metals, consisting in so preparing or making them as to prevent the possibility of any sliding or slipping of the materials one over the other when the beam or structure is under strain.
"For resisting thrust, as, for example, in the 'bow-string girder,' a tie may be made dependent upon the two end fastenings only; but a beam proper must be qualified to resist cross-strains, and equally well at any part. The tie must of necessity, therefore, be attached to the web practically throughout its entire length, and as firmly at one point as at another, the object of such fastenings not being to prevent the tie from bursting out or breaking away from the web in a downward direction, because no such tendency exists, but to counteract the tendency of the tie to slide or slip because of the force of the shearing strains got up in the beam when under bending-stress; this discovery of the true relation existing between a tie and its web also demonstrating the sufficiency of the cohesive power of the web itself to hold the tie to the top of the beam, whether such web be concrete or metal, the difference of thickness necessary for this purpose, where the web is concrete instead of being metal, being proportionate to the difference between the cohesive strength or power of metal and concrete. Basing my improvements in the ties and the manner of connecting them with the concrete upon the theory above set forth as to shearing strains, I find it important to make use of ties having the greatest friction surface. Flat thin ties are hence preferable to other shapes. To prevent slipping, these ties require also a roughened surface. This roughened or nonslipping surface may be made in many ways. For some purposes a mere sanded tarred surface may possibly suffice; but I prefer to use metal specially rolled for the purpose, with bosses or raised portions formed upon the flat faces of the metal.
"Non-slipping ties made substantially as herein described and illustrated, I propose to make and put upon the market as a new manufacture, and as a substitute for the metal in beam form."
This brief sketch would be incomplete were no mention to be made of Mr. Hyatt's notable activity in lines distinct from those we have described. During the years preceding the Civil War he was active upon the anti-slavery side, and spent time and money with great liberality to prevent the extension of slavery into Kansas. During the heated contest which arose over this question he was continually engaged in planning public meetings and in traveling back and forth between Kansas and New York. He himself made but few public speeches, but was content with the organization of these meetings and the defraying of the expenses. His interest in this subject brought him into intimate relationship with John Brown, and after the Harper's Ferry incident he was called before the United States Senate to testify. This he absolutely refused to do; consequently he was imprisoned for thirteen and one-half weeks in the Old Capitol Prison in Washington. Undisturbed by this, he made himself as comfortable as possible, invited his friends to visit him, and continued his campaign against the extension of slavery by the organization of more meetings and by vigorous newspaper articles. His imprisonment was not long continued, as the pro-slavery senators found it of little avail.
At a later date, soon after Lincoln's election, the famine in Kansas gave him another opportunity to show his public-spirited nature. The state was nearly exhausted, but through his personal efforts a relief committee was appointed, through whom a fund of $1,000,000 cash was raised, in addition to many other gifts, the proper distribution of which he directed personally, and so wisely that the state was soon in a prosperous condition again. His unselfish devotion to the welfare of the state was widely recognized, and it is related that a prominent lawyer, upon meeting him for the first time, exclaimed, " Mr. Hyatt, the people of Kansas should erect a statue of gold to your memory!"
His death occurred in 1901, at the age of eighty-five. More fortunate than many, he lived to see the widespread adoption of his system of fireproof construction, the complete extinction of slavery and the rise of Kansas to a high position among the other states in wealth and importance.

[NOTE.—Discussion of this paper is invited, to be received by Fred. Brooks, Secretary, 31 Milk Street, Boston, by June 15, 1913, for publication in a subsequent number of the JOURNAL.]

Journal of the Association of Engineering Societies, Volume 50