US1813118A - Rolled h. section - Google Patents

Description

July 7, 1931. J. H. EDWARDS ET AL 1,813,118

I ROLLED H-SECTION Filed May 15, 1925 5 Sheets-Sheet l I. H-CQ/umn I. Ang/es Jul;I 7 1931. J. H. EDWARDS ET AL ROLLED H-SECTION 5 Sheets-Sheet 2 Filed May 15 1925 rea equa/s 0. 26.9."

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Julyl 7, 1931- J. H. EDWARDS E'r A11.A 1,813,118

' ROLLED H-SECTION Filed May -15, 1925 5 Sheets-snei 5 um m L \\1 greater strength to Patented July 17, 1 931 UNITED STATES PATENT oFElcE JAMES H. EDWARDS, 0F PASSAIO, NEW

JERSEY, AND ROEERT A. MARBLE, OF BEN AVON,

PENNSYLVANIA, ASSIGNORS TO UNITED STATES; STEEL CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF JERSEY ROLLED H SECTION Application mea may 15,

hereinafter referred to.

Our invention aims to provide a solid rolled H-section, having. a mean flange thickness greater thanits web thickness, that will have resist leXure in a direction parallel to its-width when subjected to axial compression, or to combined compression and bending, than any such rolled section of the same weight and width, or of the same weight and depth heretofore proposed or put on the market; or, conversely, the pro'- duction of such a section with less width, .or less depth, than any hitherto offered rolled section of the same weight and with the same strength in the aforesaiddirection. We also aim to provide a section so proportioned that after it is surrounded by covering material a substantially smaller transverse area shall be occupied by thecfini'shed member than if any hitherto offered rolled vsection of the lsame weight and strength were used.

It is a principle accepted in the structural art that the reslstance of a compression member to flexure in any direction is measured by its ratio of slenderne'ss, that is,fby the ratio of its radius of Lgyration in that direction to its unsupported length. It is also well known that in most cases the critical or weakest direction in which lan axially loadedcolumn is liablel to first fail is that parallel `to its width. It is resistance to flexure in this direction that is considered in the embodiments of the invention illustrated and described in connection with Figs. 2 and 3.

Whichever of the purposes (or combination to of purposes) stated above is desired, is ac- 1925., serial No. 30,493.

complished under our invention by making the width of the solid rolled section (as measured across .its flanges) considerably greater than its depth (as measured between the outer faces of its flanges).

To the best of our knowledge and belief there has not heretofore been proposed or placed on the market any solid rolled H-section having this characteristic. We are famillar with solid rolled H-sections Whose width co'l is nominally equal to the depth and which as l a result of mere rolling exigencies are pro.

ducedin certain weights whose width is slightly greater than the depth but in these cases the excess wldth does not exceed -i-g of an inch. Our invention, however, is based on our discovery of the feasibility and advan- Itagev of a substantial, that is. to say, `a con siderable excess of width over depth as explained hereinafter.

The effect of our arrangement is that a greater proportion of metal-is disposed in the flanges where it acts `with greater leverage against flexure and a smaller proportion is left in the `web where its leverage would be of vlittle moment. This disposition of the metal results in a greater radius of .gyration and consequently in greater strength to resist flexure in a direction parallel to the width of the section which as explained above is generally the criterion.

To illustrate, there is nowon the market an H-column 14 inches deep, 14 inches wide, and weighing 100 pounds per linear foot. Its web is .51 inch thick and its flanges haveia 2 percent internal slope and a mean thickness of .8125 inch. Its radius of gyration parallel tothe flanges is 3.504 inches.

In comparison, Fig. 2 represents the crosssection of an H-column covered by our inf vention. It has the -same width, weight, flange slope and web thickness as the column above mentioned but instead of being 14 inches deep we make it, for example, 12 inches deep and transfer the web metal .there` by saved to the flanges to which keep the weight unchanged, we 've a mean thickness of .8503 inch. The e ect of this re-arrangement 1s that the radius of gyration'v in order to j parallel to Z-Z now becomes 3.588 inches', an increase of 2.4 percent.

Again, Fig. 3 represents the cross-section of an H-column also covered by our invention which has the same depth, weight, flange slope and web thickness as Fig. 2 but instead of being 14 inches wide we make it, for example, 13.7 inches wide, and utilize the metal thereby saved to thicken the flanges vstill more, their mean thickness now becoming .8696 inch. The result is a radius of gyration of 3.516 inches which'slightly exceeds that of the old 14 inch by 14`inch section referred to despite a reduction in width of 2.1 percent and a reduction indepth of 14 percent.

In the above calculations we have followed the American practice ofv disregarding the effect of the fillets on the radius of gyration.

If this effect is considered the radius of gyration arallel to Z-Z in all three cases will be slig tly lowered but the .relative results will remain unchanged.

If the inside faces of the flanges arerolled parallel instead of sloping, the radius of ,gyration in all three cases will be increased but the relative results will remain unchanged.

As compared with present sections of` approximately the same weight and depth, the greater strength of our sections is even more marked. Thus, there is now on the market a section of an H-column 12.37 5 inches deep, 12.12 inches wide/and weighing 99.33 pounds r linear foot. Its radius of gyration is` only 3.057 which is 14.8 percent less than that of'l the section shown in Fig. 2 proportioned according to our invention'. v

In addition to the greater resistance to lexure of our H-sections when considered as a whole, it should be noted that our invention results in making the flanges thicker (for the same weight and width of section) than present practice and this characteristic h as the added advantage of affording greater resistance to local crippling of the outstandin Harige metal. This feature is es ecially valuable in short columns which ten to fail by local crippling before their .full resistance to lexure is exercised.'

. The advantage of greater strength without n increase in weight is self-evident. The alternative advantage of equal strength and weight with an actual decrease in external dimensions is greater than is expressed by the percentage given above for' Fig. 3, es-

pecially when the sections in uestion are intended for use in a fireproo building for herethe customary methods of ,covering the column ,sections result in a percentage of space saved greater than the reduction in t e width ofthe rolled section. l

It is standard practice to make the covering of columns either circular or square and the saving in available nished iloor space then becdmes a function of the square-of the When it is considered that owners of build- I ings in congested city districts, where land values are high and sunlight at a premium, are willing to pay extra for unusual forms and greater tonnages of steel in order to reduce by even a small percentage the area at each floor occupied by columns, it will be realized that the areas savable by our invention are a valuable factor in the construction of building, especially asthey are accompanied by no greater weight of rolled column sections. l

It is well known in the structural art that .many important structures require the use of stron beamer girder sections whose depth shall ea minimum.- For example tier buildings in cities where the height of building is restricted by municipal regulation can be designed as indicated in Fig. 1 with the aid of our shallow'beam and girder sections b and so as .to secure extra tiers or floors as com-` pared with the number 'of iloors securable if deeper beams were used. This, as illustrated in Fig. 1, is due to the consequent decrease in the net thickness t of each iioor from ceiling of one story to finished Liloor surface of the next storv above. This results in a decrease in the distance-D from iioor to floor while maintaining the clear distance D1 from floor to ceiling. In other casesthe use of shallower sections eliminates ythe need of girders dropping below the ceiling line thereby making feasible the adjustability of partitions in any location without marring the architectural effect and decreasing the quantity of -ireproong, plastering, or other finishing material required. c l l A similar advanta e occurs in the floors of railroad or other-bridge construction where the Afrequent-need of a minimum difference between the over and under road grades combined with fixed headroom makes strong but shallow sections of iloor beams a desideratum.

In cases similar to the above when the clear span of a beam is properly braced laterally, its' strength to resist vertical flexure is determined by its section modulus about a horizontal axis. v

We will now show how our invention permits an equal or greater section modulus per pound of beam combined with a shallower de th than any existing rolled section.

ere is an old H-section now on the market 12.375 inches deep, 12.12 inches wide, weighing 99.33 pounds per linear foot whichhas a section modulus of 129.6 which is 1.3047

'01.3537 lper pound. vThus, our section although slightly vshallovver is 3.76 percent stronger than the old one last referred to.

Fig. 5 shows another H-section embodying our invention. This section is 14.154 inches deep, 15.145 inches Wide, it weighs 115 pounds per foot 4and has a least radius of gyration of 3.89.

It will be noted that the additional width of our sections when used as floor beams occupies no more useful s ace than the lnarrower sections now on t e market for the reason that the width is buried in the oor itself.- We shall now show that this additional width is actually of further advan tage.

As stated above, braced laterally its section modulus is the criterion of its strength to resist flexure. If, f

however, it is 4not feasible to provide adef uate lateral bracing all-standard specifications stipulate that the working unit stress, F

bv which the section modulus isto be multiplied in order to ascertain the resistance of increased but .the relative results the beam to flexure, shall be reduced by an amount that varies with the ratio of the unbraced length of beam to its width. In

l such cases it is evident the reduction inallowable working stress for our section isless than in the case of the narrower sections now when a beaml is properly'A i vention as 'pointed out.A in the appended claims.,

What we claim is: 1. A rolled steel section of substantlazlly or a proximately H-shape in cross-section Weig mg 115 pounds per linear foot and having the following dimensions, depth 14.154 inches, width. 15.145 inches, web .551 inch thickeach of the""langes having a slight slope and a mean thickness of .882 inch. v

` 2. A .rolled steel section of substantially or opproximately H-shape in cross-section,

weighing 115 pounds per linear foot and having the following dimensions, depth 14.154 inches, width 15.145 inches web .551 inch ticll, each of the flanges being .882 inch t ic v3. A rolledmetal section of.v substantially Y or approximately H-shape in erom-'sectionwhose ratio of least radlus of gyration di` vided by the depth of the section exceeds 0.27.

jr In witness whereof, we have hereunto v signed our names. JAMES H. EDWARDS.

`ROBERT A. MARBLE.-

in use and consequently its availablestrength l is still greater;

In the above calculations We have followed the American practice of disregarding the el'ect of the fillets on the section modulus. If this effect is considered the section moduli in 'question in all five figures will be slightly will remain unchanged.

The term structural section used in the claimsis intended ,to cover either column, glrder orbeam sections particularly adapt-I ed for use in the construction of buildings,

bridges and the like as distinguished from comparatively smaller sections of somewhat similar contour but not having vthe same .properties and used chiefly for small machine elements such as axles, connecting rods and the like found in artsoutsideof th building trade.

we are limited thereto as certain ranges'of ya-riation can be resorted to `by those skilled, inthe art without departing from the in-

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