US3577862A - Composite precompressed grating structure - Google Patents

Abstract

This invention provides a novel floor system which has outstanding advantages in structures, such as powerhouses, nuclear power plants, chemical plants and other such large structures whereby an adequate floor is provided with a sizeable reduction in deadweight. The deadweight design of these structures exceeds the liveweight capacity designs due to the fact that a minimum number of personnel are involved in the operation os such plants. A grating is provided whereby the weight can be reduced materially and/or the span materially lengthened so that the resulting floor support and columns is also reduced. In addition to the reduction in the weight of members, the number of support members for the new floor design is reduced materially, thereby saving additional weight and cost.

Description

United States Patent [72] Inventor Henry P. Cerutti Mount Lebanon, Pa. [21] Appl. No. 751,663 [22] Filed July 12, 1968 [45] Patented May 11, 1971 [73] Assignee Blaw-Knox Company Pittsburgh, Pa.

[54] COMPOSITE PRECOMPRESSED GRATING STRUCTURE 6 Claim, 2 Drawing Figs.

[52] U.S. Cl 52/223, 52/669 [51] Int. Cl E0lc 9/10, E040 2/42, F'16s 3/08 [50] Field ofSearch 52/666, 640, 222; 52/664, 668, 223, 669

[56] References Cited UNITED STATES PATENTS 2,190,214 2/ 1940 Nagin 52/667 2,437,186 3/1948 Collins 52/667 2,645,985 7/1953 Beebe 52/668 3,101,272 8/1963 Setzer OTHER REFERENCES STRESSED-SKIN PANEL DESIGN, by Nelson et al.,

Agricultural Engineering, Oct. 1960, Copy in Art Unit 356 in Class 52, Subclass 222.

Primary Examiner-Henry C. Sutherland Attorney-Buell, Blenko, Ziesenheim, Beck, Smith & Bogdon ABSTRACT: This invention provides a novel floor system which has outstanding advantages in structures, such as powerhouses, nuclear power plants, chemical plants and other such large structures whereby an adequate floor is provided with a sizeable reduction in deadweight. The deadweight design of these structures exceeds the liveweight capacity designs due to the fact that a minimum number of personnel are involved in the operation us such plants. A grating is provided whereby the weight can be reduced materially and/or the span materially lengthened so that the resulting floor support and columns is also reduced. In addition to the reduction in the weight of members, the number of support members for the new floor design is reduced materially, thereby saving additional weight and cost.

Patented May 11, 1971 INVENTOR.

HENRY P. CERUTTI 6W JKEBM A T TORNE Y COMPOSITE PRECOMPRESSED GRATING STRUCTURE Accordingly, I have invented a grating floor structure with a composite weight of 7.3 pounds per square foot which has the load-carrying capacity of an equivalent present-day grating weighing between 17 and 19 pounds per square foot. The gratings are compared relative to their uniformally distributed load-carrying capacity with resulting deflections which fall within the generally accepted construction classifications. The new composite grating will carry equivalent loads with less deflection rather than equal deflection, thus making it less resilient underfoot and a better product. As a comparison on an 8-foot span, this new grating with a composite weight of 7.3 pounds per square foot will support 475 pounds per square foot with a deflection of 0.272 inches, whereas a grating in accordance with the prior art weighing 17.69 pounds per square foot will carry 405 pounds with a deflection of 0.465 inches. It is obvious that the more rigid grating is desirable as a walking surface. This, in essence, repeats itself in a variety of spans between 2 feet and 8 feet on a direct comparison.

A composite l-beam and floor grating is provided wherein the floor grating itself forms the top portion of the l-beam. Thus, an inverted T-beam has fastened to thetop thereof a latticed network of longitudinal and horizontal bars welded together and welded in turn to the vertical portion of the inverted T-bearn. Thus, an l-beam is produced wherein, instead of having a continuous piece of metal along the length of the lbeam for the top horizontal portion of the l-bearn, there is provided periodic cross rods spaced apart and welded to the top of the vertical section of the inverted T-beam, the cross rods being in turn welded to longitudinal grate members extending parallel to the main axis of the inverted T-beam and being generally in the configuration of flat strips of metal turned on edge so that their larger surface is parallel to the upright portion of the inverted T-beam. In this configuration, the grate members obtain-all of their support through the T-beam and are not supported directly themselves. The result is a much stronger unit of lighter weight than that traditionally employed.

BACKGROUND OF THE INVENTION Gratings in the prior art have generally been constructed of a plurality of flat strips of steel or similar semirigid material, turned on their edges so that their larger surfaces extend in a vertical direction and spaced apart, the spacing depending upon the use of the grating but generally in the range of 1 inch to 2 inches between centers. These flat pieces rest for support at their ends or tips on some solid structure support member which constitutes the support for the grate. Interconnecting the flat strips are a plurality of rods extending laterally across the tops or near the tops of the flat strips in a spaced-apart relationship usually at right angles to the long dimension of the flat strips. The cross rods are generally welded, or similarly secured, to the flat plates at their point .of contact so as to produce a rigid structure. The cross rods are frequently twisted configuration so as to provide a more skid-free surface for the person walking on the grate.

SUMMARY OF THE INVENTION A plurality of inverted T-beams spaced apart from each other are interconnected by horizontal cross rods which extend through notches in the top of the inverted T-beams and are welded to the T-beams. The cross rods are spaced apart and are of relatively rigid steel. lnterconnecting the cross rods, I provide spaced-apart grate bars which comprise flat strips of metal turned on edge and having grooves in the top edge thereof into which the cross rods fit in a close relationship. The cross rods and the grate bars are also welded together at their intersection. The grate bars have a width which is substantiallyless than the height of the T-beams so that the unit dependsfor its support upon the T-beams which are supported at their ends by resting on other structures. The relative dimensions of the inverted T-shaped support beams, the cross rods, and the grate bars, as well as their relative locations with respect to each other together with their relative strength, are better defined and will be understood more from the following detailed description.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification and, in which:

FIG. 1 is a plan view of the apparatus in accordance with my invention.

FIG. 2 is an elevational showing in cross section of the apparatus shown in FIG. 1, taken along the line 2-2 of FIG. 1.

In accordance with the preferred embodiment of my invention, I provide a grate comprising a plurality of inverted T- beam support pieces 4. The T-beams furnish the support for the system and are supported at their ends, as for example, resting on ledges. At the top of the inverted T-beams 4 and extending through grooves in the top of the T-beams, I provide lateral cross rods 6 which interconnect the successive T- bearns. These rods are preferably of square cross section and are preferably twisted in order to provide better traction for the finished grate. Extending parallel to the T-beams 4 and perpendicular to the cross rods 6, I provide grating bars 8 of rectangular cross section turned on edge so that their larger surfaces extend in a vertical direction. Where the grating bars 8 engage the cross rods 6, the cross rods 6 extend through notches in the grating bars 8 and are welded together at their junctions. The grating bars 8 are substantially narrower in their vertical direction than the height of the T-beams. When the unit is installed in place, the grating 8 bars are not supported except by the cross'rods 6. The grating bars 8 do not rest on other structural members. Thus, the grating bars 8, instead of supporting the cross rods 6 are actually floating free hanging from the cross rods 6 and supported by the cross rods.

In the preferred embodiment of my invention, the T-beams 4, the cross rods 6, and the grating bars 8 should be welded or electroforged together so as to produce a secure junction. However, it is understood that in accordance with other embodiments of my invention, other means of joining could be employed, such as by the use of metal screws, although not as efficiently.

For imparting further stability to the grate unit, a transverse bar 10 of rectangular cross section having its larger surface extending in a vertical direction may be fastened between adjacent T-beams to inhibit twisting or rotation of the T-beams about a longitudinal axis.

The relative dimensions of the various members will be a function of several factors such as the amount of weight which the structure is to support, the distribution of that weight and the tensile strength of the materials employed. However, in accordance with a preferred embodiment, I provide a T-beam 4 of one-eight inch thick metal having a base 2 inches wide and a height of 3 inches. The height is a somewhat flexible dimension and may readily be varied between 2 inches and 4 inches. The cross rods 6 are preferably one-fourth inch to five-sixteenths inch square and are spaced apart between 2 inch and 4 inch centers. The grate bars 8 are preferably one-eighth inch thick by three-fourth inch wide.

The foregoing FIGS. define a desirable grate structure in accordance with my invention. For variations however, the following parameters will serve as a better guide. Thus, the foregoing FIGS. may be varied in accordance with one embodiment of my invention within limits wherein the cross rods 6 are spaced apart a distance less than five times their circumference,wherein the grate bars 8 are spaced apart a distance less than 10 times their average thickness, or wherein the cross rods 6 are spaced apart a distance less than the height of the T- beam 4 plus twice the circumference of the cross rods. it is also desirable in accordance with one embodiment of my invention, that the cross rods 6 be spaced apart a distance less than the product of the sum of the height of the T-b'cam 4 and twice the circumference of the cross rods 6 when multiplied preferably spaced apart by a distance less than the product of times their thickness and the ratio of the tensile strength of the grate pieces to the tensile strength of the T-beam.

In accordance with another embodiment of my invention, the grate may be manufactured in a prestressed condition. This may be accomplished by employing cross rods of a curved configuration before they are fitted into place. It will be noted that from the configuration of the grate, the deformation or buckling of the grate will occur in a vertical direction tending to collapse or bend the top of the T-beams 4. In the theory of a grate in accordance with my invention, the grate bars 8 reinforce or position the cross rods 6 and the cross rods 6, by their resistance to bending, tend to prevent the buckling of the top of the T-beams 4. In addition, the grate will have a tendency to buckle, if at all, in the region near the center of the grate. Therefore, greater static stress would be built into the system near the center and less toward the ends. Thus, each successive cross rod should be successively slightly different in the inherent stress therein; or in accordance with another embodiment of my invention, the cross rods on each half of the grate would be curved between successive T-beams prior to their being fastened into position such that their center of curvature is toward the other end or opposite end of the grate.

Thus, I have provided a floor system for large structures where the deadweight design of the structures exceeds the live weight capacity designs due to the fact that a minimum number of personnel are involved in the operation of the plant. A grating has been provided whereby the weight is reduced materially and/or the span materially lengthened so that the resulting floor is much lighter and the resulting steel structure of the floor support and columns is also reduced.

Thus, I have provided a grating floor structure with a composite weight of 7.3 pounds per square foot which has the loadcarrying capacity of an equivalent present-day grating weighing between 17 and 19 pounds per square foot. The gratings are compared relative to their uniformally distributed load-carrying capacity with resulting deflections which fall within the generally accepted construction classifications. The new composite grating described herein will carry equivalent loads with less deflection rather than equal deflection, thus making it less resilient underfoot and a more desirable structure. As a comparison on an 8-foot span, this new grating with a composite weight of 7.3 pounds per square foot will support 475 pounds per square foot with a deflection of 0.272 inches, whereas a grating in accordance with the prior art weighing 17.69 pounds per square foot will carry 405 pounds with a deflection of 0.465 inches. it will be apparent to those skilled in the art that the more rigid grating is desirable as a walking surface in addition to conserving weight and cost.

The term T-beam as used herein refers to beams, the cross section of which comprise a vertical portion and a horizontal portion, the horizontal portion being connected near its center in a preferred embodiment of my invention. However, the term T-beam as used herein is meant to include beams constructed with otfcenter connections or junctions including beamsof the type referred to generally as angle iron.

Also, the term grate as used herein includes grate-type structures, both covered and uncovered and both open grates and grates having material such as insulating material in the interstices between the grate bars or under the grate bars.

lclaim:

l. A precomposed grating comprising at least one inverted T-beam, a plurality of spaced apart generally parallel linear cross rods positioned at an angle and securely connected to the stem of said T-beam, said linear rods, in a relaxed state, being arcuate, the linearization and connection of the arcuate rods creating a precompression toward the center of said structure in the plane defined by the cross rods; and a plurality of spaced-apart grate rods having a height less than said stem and positioned substantially parallel to said T-beam and securely connected to the cross rods, saidconnections being such that the top of all rods and stem lre rn substantially the same plane which comprises the grate surface whereby only the flange of said T-beam rests upon a grate supporting structure.

2. Apparatus as described in claim 1 wherein said cross rods are spaced apart a distance less than five times their circumference.

3. Apparatus as described in claim 1 wherein said grate pieces are spaced apart a distance less than 10 times their average thickness.

4. Apparatus as described in claim 1 wherein said cross rods are spaced apart a distance less than the height of said T-beam plus twice their circumference.

5. Apparatus as described in claim 1 wherein said cross rods are spaced apart a distance less than the product of the sum of the height of said T-beam and twice the circumference of said cross rods multiplied by the ratio of the tensile strength of said cross rods to the tensile strength of said T-beams.

6. Apparatus as described in claim 1 wherein one of said grate pieces is spaced from the vertical portion of said T-beam by a distance less than the product of 10 times its thickness and the ratio of the tensile strength of said grate piece to the tensile strength of said T-beam.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. Dated y 1, 1971 Henry P. Cerutti Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Abstract, line 8, "05" should read of Column 4, line 17, "parallel" should read parallelled line 18, "cross rods" should read cross-rods line 19, "relaxed" should read rerelazed Signed and sealed this 30th day of November 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents FORM FO-IOSO (10-69! USCOMM-DC 60376-P09 w u s GCIVERNMENY Pnmnm: OFFICE n09 O-36S-334

Claims (6)

1. A precomposed grating comprising at least one inverted Tbeam, a plurality of spaced apart generally parallel linear cross rods positioned at an angle and securely connected to the stem of said T-beam, said linear rods, in a relaxed state, being arcuate, the linearization and connection of the arcuate rods creating a precompression toward the center of said structure in the plane defined by the cross rods; and a plurality of spaced-apart grate rods having a height less than said stem and positioned substantially parallel to said T-beam and securely connected to the cross rods, said connections being such that the top of all rods and stem lie in substantially the same plane which comprises the grate surface whereby only the flange of said T-beam rests upon a grate supporting structure.

2. Apparatus as described in claim 1 wherein said cross rods are spaced apart a distance less than five times their circumference.

3. Apparatus as described in claim 1 wherein said grate pieces are spaced apart a distance less than 10 times their average thickness.

4. Apparatus as described in claim 1 wherein said cross rods are spaced apart a distance less than the height of said T-beam plus twice their circumference.

5. Apparatus as described in claim 1 wherein said cross rods are spaced apart a distance less than the product of the sum of the height of said T-beam and twice the circumference of said cross rods multiplied by the ratio of the tensile strength of said cross rods to the tensile strength of said T-beams.

6. Apparatus as described in claim 1 wherein one of said grate pieces is spaced from the vertical portion of said T-beam by a distance less than the product of 10 times its thickness and the ratio of the tensile strength of said grate piece to the tensile strength of said T-beam.

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