US3565264A

US3565264A - Pallet rack equipped with sheet metal structural member

Info

Publication number: US3565264A
Application number: US726641A
Authority: US
Inventors: William T Guiher
Original assignee: Republic Steel Corp
Current assignee: Republic Storage Systems Co Inc
Priority date: 1968-04-16
Filing date: 1968-04-16
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A pallet rack with cold formed pallet supporting beams constructed such that when pallets are positioned on the rack controlled twisting of the beams occurs until load and reaction forces are in equilibrium. The disclosure also includes an improved nonsymmetrical cold formed beam having a web located according to the load to be supported, whether symmetrically or nonsymmetrically applied, such that the beam does not twist under load, or, as in the pallet rack, may have limited controlled twisting. The beam as used in the pallet rack is constructed such that the shear center of the beam lies along a line in or adjacent the web portion.

Description

United States Patent XXXX ww All% 6/// 112 115 22 k l c N m 8 M a 1 m m M m m w m. m. m d "n "mdm l n u .m J a m m m H%d t H u n .1 n h n m e L a Mn 1. mm admfm mvan CRJH fl w D 3457 P 6666 r 9999 we 1111 N ////.n b 7077 WmO 7439 9. 7 W e an 5 52 at 9593 mbo nmn 3333 PAA n 0 m .L m e 0 m m s 811 Cu 7 0 9$ 9 x 8 4 mm hanm r ovmnnwwk WY7AFRC 0. de m N m m n l n e pwm w m puas l AFPA 11]]. 2 1253 7 2247 l [ill [54] PALLET RACK EQUIPPED WITH SHEET METAL STRUCTURAL MEMBER 16 Claims, 8 Drawing Figs.

ABSTRACT: A pallet rack with cold formed pallet supporting beams constructed such that when F VJ om mu a oa d a m mm r, m m te mm mmm mm mu em fl u d M mu c [u w w u Wm H dl mm nw the rack controlled twisting of the be A47f 5/ reaction forces are in equilibrium.

211/177, The disclosure also includes an improved nonsymmetrical 54 cold formed beam having a web locat 5 731, to be supported, whether symmetric 733; 243/248, 247 applied, such that the beam does not References Cited UNITED STATES PATENTS 2,Q65,378 12/1936 Klin ,NSATA 189.3601

[] Field ol'Search............ 176, 287/l89.36, 189.36 (D) the pallet rack, may have limited controlled twisting. The

beam as used in the pallet rack is constructed such that the shear center of the beam lies along a line in or adjacent the web portion.

PATENT EU FEB23197| SHEET 1 0F 3 INVENTUR. WILLIAM. T. GUIHER BY UfafigHoHmannjFiSMHQinkQ ATTORNEYS.

Pmmmmam 3,565,264

' sum 2 BF 3v INVEN'mR. WILLIAM T. GUIHER PALLET RACK EQUIPPED WITH SHEET METAL STRUCTURAL MEMBER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pallet racks and more particularly relates to a pallet rack equipped with novel and improved structural beams formed of sheet metal material and to such beams.

l-beams constructed of a continuous strip of sheet metal are desirable because of their relatively low cost and, when made according to this invention, high load carrying capacity per unit weight.

2. The Prior Art Proposed cold formed I-beams have been capable of supporting only light loads because their construction was such that extensive, uncontrolled twisting would occur if substantial loads were applied. In an I- or Z-beam configuration such twisting can result in rapid loss of load carrying ability of the beam and sudden failures. Accordingly, one-piece sheet metal beams, such as land Zbeams, have been thought to be limited to supporting relatively light loadings over relatively short spans. Thus proposed uses for l-beams which could be formed by cold forming techniques have been in such applications as supporting drop ceilings. These ceilings normally have relatively light sound proofing material supported by lower flanges of small beams, which material places the webs of the beams in slight tension.

The beam of this invention and certain prior proposed beams formed by cold rolling a continuous strip of sheet metal to produce the desired cross-sectional configuration are not symmetrical. The nonsymmetrical cross sections of such beams are due to the longitudinal folding of the material on itself to fonn the flanges. 1

While prior proposals for l-bearns susceptible to cold formation have not been symmetrical, they have had webs which, like conventional hot formed l-beams, lie in planes that vertically bisect the flanges. Thus while not truly symmetrical they have an overall appearance of symmetry. For reasons which are explained presently such beams have poor load supporting characteristics which tend to cause twisting of the beam under load. Such a beam twists when utilized to support a substantial symmetrical load (a load applied uniformly transversely of the plane of the web across a flange of the beam and producing a resultant force acting parallel to the plane of the web). This twisting is about an axis referred to as the shear axis, or shear center of the beam.

Pallet supporting beams must be capable of supporting widely varying, and often large, loads over substantial spans. Prior pallet rack constructions have utilized channellike or tubular beams to support pallets. Prior cold formed beams were not suitable for pallet racks and accordingly previous pallet racks have not used wide flange, cold formed load supporting beams.

The prior art proposals have not suggested a one-piece relatively light gauge beam construction susceptible to cold formation and high load carrying capacities. The basic problem encountered in attempts to construct such a beam has resulted from the following considerations: l a one-piece wide flange beam necessarily has nonsymmetrical flanges; (2) the use of light gauge sheet metal in the construction of such beams has therefore resulted in severe twisting of the beams under load; (3) this twisting limits the load carrying capabilities of the beams as well as the spans over which a given load can be supported; (4) the use of extremely heavy gauge or plate material can reduce twisting under relatively light loads, but such a beam would be undesirable because of relatively great weight and limited load carrying ability without twisting.

Further complicating the problem is the fact that relatively small twisting deflections of beams which have a span of feet or more are undesirable from an aesthetic standpoint. Such a beam which is twisted about its neutral axis under load beam is structurally more than capable of maintaining the ap' plied load.

The foregoing considerations have resulted in extensive use of multipart light gauge beam assemblies of the box type, tubes, Zs and channels. A widely held belief has been that box or I-beams constructed of light gauge material must be formed from a plurality of sheet metal members to avoid the problem of twisting excessively under load.

SUMMARY OF THE INVENTION The beam of this invention is a wide flange beam of a single light gauge sheet of material having a higher load carrying capacity per unit weight than conventional cold formed beams. In addition to this favorable load/beam weight relationship, such a beam does not'twist appreciably under load and is less expensive than prior art construction.

A pallet rack constructed in accordance with this invention will support widely varying and often extremely large loadings. The use of these beams also results in a rack which permits greater weights of material to be stored in a given space without exceeding maximum permissible floor loadings and the like than has been possible with prior racks. When utilized as a grit or purlin, a beam constructed in accordance with the invention provides similar advantages.

It has been discovered that wide flange sheet metal beams constructed of a single sheet of relatively light gauge material can be used to support relatively large loads over substantial spans. This is accomplished by providing load supporting flange configurations which produce a shear axis for the beam disposed in or closely adjacent the web. Thus substantial twisting of the beam is prevented. More precisely, such beams are designed to provide a flange configuration which accepts a given loading (symmetrical or nonsymmetrical) and deflects slightly to shift the loading of the beam and produce a stress condition in the beam wherein further twisting of the beam is prevented. The flanges of such a beam shift the center of gravity of the load applied so that the load resultant acts through the shear center and unbalanced shear flows in the beam are ineffective to cause twisting.

While a theoretical discussion of the reasons why beams, such as l-beams, do not twist when the shear center of the beam passes through the web is not necessary to the understanding of the invention, some understanding of these reasons is desirable. The shear center or axis of the beam is the axis about which the beam will twist as a result of unbalanced shear flows in the beam. Where the center of gravity, or resultant, of an applied load passes through the shear center of a given beam, that beam will not twist. This is because the sum of the moments of the shear flows about the shear axis at such a condition are equal to zero.

The location of the shear center of a beam is geometrically fixed with its location detennined by the cross-sectional configuration of the beam. When the center of gravity of the applied load passes through the shear center of a beam, the beam will not twist. But if, because of deflection of the flanges, the resultant of the load moves away from the shear center, twisting ensues. This twisting is a function of the load and the distance between the load and the shear center.

When using light gauge sheet metal in the construction of a wide flange beam (such as an I-beam), flange deflection under any significant load is inescapable. The present invention contemplates the construction of a beam having a shear center located so that flange deflection shifts the center of gravity of the load to a location wherein the load acts through the shear center. Thus by moving the line of action of the load to act through the shear center a one-piece light gauge sheet metal beam is provided which does not twist appreciably under relatively large loads.

Thus beams configured according to the principles of the invention are utilized to accommodate nonsymmetrical loadings which might otherwise result in twisting of a symmetrical hot loolts to the observer as if failure is imminent even when the formed I-beam or a channel of equivalent size. A beam constructed in accordance with the present invention for receiving a nonsymmetrical load possesses a shear center which, with the load applied, is closely adjacent or in the web of the beam so that, at most, only a minimal amount of twisting of the beam is produced.

Further, a beam constructed according to the invention for accommodating a symmetrically applied load does not twist appreciably as do prior art sheet metal beams of the flanged type. This is due to the fact that the applied load is shifted as described.

In a pallet rack constructed in accordance with the invention supports for the beams are spaced from the plane of the web. Thus beam supporting reaction forces applied to the beam are offset from the web and the shear center. These offset reaction forces tend to cause twisting of the beam. The beam is so configured that a slight controlled amount of deflection in the flanges occurs. The noted reaction forces act to promote deflection of the flanges. This shifts the load applied by a supported pallet relative to the plane of the web. The line of action of the load is thus shifted to a location where it passes through the shear center and an equilibrium condition is established.

Because of differing user requirements a number of beam sizes must be made available. Accordingly families of beams embodying the invention are provided. Beams in a family have the same flange constructions and web heights which differ from beam to beam over a given range of heights. Beams having small web dimensions and beams having large web dimensions may have shear centers located slightly out of the web. Preferably the location of these centers is no farther away from the web centerline than will result in a 2 twisting of the beam about the neutral axis over a length of to 12 feet.

Accordingly, a principal object of the present invention is the provision of a new and improved wide flange beam constructed of a single cold formed sheet of metal wherein the flanges and web of the beam are so related that when a load is applied to the beam the load shifts until the load resultant acts through the shear center or axis of the beam and twisting of the beam is controlled to a minimal amount or eliminated. The preferred form of the invention is a one-piece I-beam wherein the web of the beam is spaced from the centerline of the load engaging flange and the shear center is in or very close to the web.

Other novel and advantageous features of the present invention will become apparent from the following detailed description thereof made with reference to the accompanying drawings which form a part of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a pallet rack employing wide flange beams constructed according to the present invention;

FIG. 2A is an enlarged fragmentary view of a portion of a pallet rack of FIG. 1;

FIG. 2 is an enlarged fragmentary sectional view of a portion of the pallet rack of FIG. 1;

FIG. 3 is a sectional view of a pallet rack beam constructed in accordance with the invention with a fragmentary portion of one of the verticals shown and schematically showing a pallet and supported load; and

FIGS. 4-6 are sectional views of beams constructed in accordance with the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 illustrates a pallet rack 10. As is conventional the rack 10 is susceptible to modular construction so that any selected number of such racks may be interconnected to cover a given area. The rack 10 includes four vertical support columns 11l4. The rack 10 has

pallet supporting beams

15, 16 connected to the columns l1, l2 and

pallet supporting beams

20, 21 connected to the columns 13, 14. The

pallet supporting beams

15, 20, and 16, 21, respectively are removably secured to their respective support columns so that the upper surface of the

beams

15, 20 as viewed in FIG. I, are each disposed substantially in a horizontal plane for receiving and supporting pallets. The

beams

16, 21 are likewise disposed with their upper surfaces in substantially a common horizontal plane and positioned to support pallets beneath the

beams

15, 20.

The vertical support columns 11, 13 are supported relative to each other by laterals 22-26 which are suitably secured at their ends to the columns 11, 13. The vertical columns l2, 14 are similarly interconnected by laterals 30-34 which are identical to the laterals 22-26. Additional lateral support for the pallet rack 10 is provided by

members

35, 36 which are removably secured between the

load supporting beams

15, 20 and 16,21 respectively.

The columns 11--l4 are identical in construction and each includes a base or foot 36, formed by a plate of suitable material such as steel, and a generally tubular vertical 37. The verticals 37 are generally square in cross section and are formed of a single sheet of steel having edges spaced to define vertically extending end gaps 40 for receiving ends of the laterals.

The verticals 37 have outwardly oriented walls 41 each opposite the end gap 40 of the same column. Each wall 41 is perforated to define a series of regularly spaced apertures 42 along its vertical extent, only a few of which apertures are illustrated in FIG. 1. The

beams

15, 20 and 16, 21 are connected to the columns ll-l4 by clips 43 which are preferably welded to ends of these beams. The clips are removably secured to the verticals and fixed in place by interconnection with the apertures 42.

One of the clips 43 associated with the beam 20 is illustrated in FIG. 2A. The clip 43 includes a plate portion 44 in a plane transverse to the longitudinal axis of the beam 20. The clip 43 also includes a flange 45 which is bent at substantially a right angle to the plate 44, and

tabs

46, 47 formed continuously with the flange 45.

The tabs 46 are bent to extend from the end of the flange 45 generally parallel to the plane of the plate 44 and are spaced apart a distance which corresponds to the spacing between adjacent apertures 42 in the verticals 37. Each of the tabs 46 includes a downwardly extending finger S0 and a lower support surface 51. The tabs 46 are adapted to extend through an associated aperture 42 with the support surface 51 in supporting engagement with the vertical 37 at the bottom of an aperture 42. The fingers 50 engage the walls 41 to secure the clips 43 in place. The fingers 50 therefore provide a lock between the clips 43 and the verticals 37 so that the pallet supporting beams must be raised relative to the verticals 37 for disengagement.

The tabs 47 extend away from the plate 44 in the plane of the flange 45. When the pallet supporting beam members are fastened to the verticals 37, the tabs 47 engage the walls 41 and assist in maintaining proper alignment between the verticals 37 and the associated pallet supporting beam members.

FIG. 2 illustrates a vertical 37 which is associated with two pallet supporting beam members extending in opposite directions from

sides

55, 56 of the vertical 37. The tabs 46 extend through the openings 42 defined in the wall 41 with the fingers 50 hooked over the bottoms 57 of the apertures to lock the clips 43 in place.

Each of the

sides

55, 56 of the verticals 37 includes a plurality of elongated openings 60 formed at regularly spaced locations. A detent pin 61 is carried on a spring arm 62. The spring arm 62 is supported by the plate 44 of the clip 43. The detent pin 61 extends through a suitable opening in the plate 44 into an aligned one of the apertures 60. Coaction of the pin 61 with the walls of the selected aperture 60 prevents accidental disconnection of a clip 43 from its vertical 37, and also provides a visual indication of proper assembly of the pallet rack.

The clips 43 form the sole support for the

pallet supporting beams

15, 20; 16, 21. Thus, reactions to loads applied to the beams are in the plane of the walls 41 laterally outwardly of the beams proper. As a result of the relationship between the clips 43 and the pallet supporting beams, the application of the load to the beams causes a twisting supporting force to be applied to the beams at their ends in the direction of the arrow in FIG. 2.

FIG. 3 schematically illustrates a pallet 65 and load 66 supported by the

beam members

15, 20. The

beam members

15, 20 are preferably composed of cold formed sheet steel material and each includes a web 70 extending in a generally vertical plane and upper and

lower flanges

71, 72 respectively. The upper and

lower flanges

71, 72 are each identical and each includes double and single

thickness flange parts

73, 74, respectively, disposed along the longitudinal extent of the web 70 and projecting in opposite directions from the web. The double thickness flange part 73 includes a portion 73a formed continuously with the web 70 and extending generally transversely from the plane of the web. The flange part 73 is folded on itself to define a portion 73b continuous with the flange portion 73a and bent back upon the portion 73a along a radiused bend 75. The flange portion 73b extends from the bend 75 generally transversely of the plane of the web 70 to the flange part 74.

The single thickness flange part 74 includes a portion 740 formed continuously with, and in the plane of, the portion 73b. The flange part 74 also has a longitudinally extending bend 76 formed along the part and an elongated reinforcing lip portion 77. The flange portions 73b, 74a defined a continuous upper surface 78 of the flange 71, FIG. 2.

The load 66 and pallet 65 are disposed upon the upper surface 78 of the flange 71. As indicated previously the flanges 71 of the

beams

15, 20 are substantially in a common horizontal plane so that the pallet loads are applied across the surfaces 78. The pallet load is illustrated by the arrow F L in FIG. 3 and as it is applied to the

beams

15, 20 they tend to twist slightly in clockwise and counterclockwise directions respectively. The twisting referred to is accompanied by shifting of the application of the load on the beams until an equilibrium condition of the beam is reached as is described in considerably greater detail presently.

The clips 43 tend to exert a twisting reaction to load forces applied to the beams. This reaction is illustrated by the arrow F S in FIG. 3. The supporting force F s exerted by the clips 43 tends torotate the beam in a clockwise direction (FIG. 3) and accordingly the coextending portions of the flange part 73 are urged toward engagement with the pallet 65. The flange part 73 therefore is caused to support a greater proportion of the applied load. Said another way, the applied load is shifted along the flange 71 of the beam 15 to the left as viewed in FIG. 3.. When the moment of the supporting forces F about the beam is equaled by the moment of the load force supported by the beam, the beam is in equilibrium with the shear center of the beam being disposed within the web 70. In test, beams of the type described have reached equilibrium conditions upon an angular deflection of the plane of the web 70 away from vertical through an angle of less than 1. The previously described beam twisting continues until the beam twisting force of the load shifts, in the beam 15, to the left toward the bend 75 until it is equal to the counter twist of the reaction force F and an equilibrium is reached.

In a beam of the character described the web 70 and top and bottom flange parts 73 may be thought of as a channel which under load tends to deflect about the shear axis e located on the opposite side of the plane of the web 70 between the flange parts 74. The top and bottom flange parts 74 and web 70 may also be thought of as a channel which tends to twist about a shear axis e located on the opposite side of the web 70 between the flange parts 73. The first mentioned channel tends to twist counterclockwise about the axis e while the second tends to twist clockwise about the axis e Accordingly, the channels act in opposition to each other under load and thus tend to minimize twisting deflection of the beam under load.

It will be appreciated that the above described channel analogy is not accompanied by twisting of the web since the web is included in each channel. The flange parts actually deflect slightly under the applied load and shift the location of the center of gravity or resultant of the load. The flange deflection occurs as a result of the relatively light gauge of the beam material with respect to the supported load. For example a beam constructed from l3-gauge sheet steel and according to the invention operated successfully in a pallet rack.

Furthermore, the supporting forces F (FIG. 3) applied to the beam by the clips 43 tend to urge the upper flange part 73 toward engagement with the pallet so that the upper flange part 73 supports a greater proportion of the load than would otherwise be supported in the absence of the forces F Similarly, the flange part 74 tends to be twisted away from engagement with the pallet as a result of the support force F The effect of the slight deflection of the flanges and the application of the support forces F upon the beam is to change the relationship between the load and the beam so that under a load, each

beam

15, 20 reacts to shift or redistribute the applied load. The geometry of the

beams

15, 20 in FIG. 3 produces a resultant shear axis e of each beam which lies on a line extending through the web or closely adjacent the web when the beam is not loaded. As a result the

beams

15, 20 undergo only minimal twisting under the applied load in reaching equilibrium.

In a pallet rack a variety of loads may be supported by the beams, and it is not possible to design the beam for any particular constant load as might be applied, for example, in a building structure. Nonetheless, under any given pallet load, the beams react in the manner described until the moments of the supporting forces on the beams are counteracted by the shifting load on the top flanges of the beams. The beams thus reach an equilibrium upon deflection of an amount determined by the load itself. Regardless of the load supported by the beams, the beams react to accommodate the load and reach a condition wherein the moments or twists of the load about the shear axis of the beam become balanced or equal to zero after which further deflection is prevented.

THE BEAM CONFIGURATION OF FIG. 4.

The beam 15' of FIG. 4 is of substantially the same geometry as

beam

15, 20 referred to in reference to FIGS. 1- 3 and accordingly the same reference characters are utilized, with primes added, in the description of the various portions of the beam 15'.

The beam 15' is adapted for a structural installation such as a purlin or grit in a building structure. Accordingly the load to be applied to the beam, such as that of FIG. 4, is substantially constant as distinguished from the wide variations in loading of the

beams

15, 20 of the pallet rack 10. Thus the beam 15' is rigidly supported at its ends and need not be associated with the clips 43. Since the loads to be applied to the beam 15' are known and relatively constant, the geometry of such a beam to accommodate the load to be applied can be calculated.

The location x of the shear center of the beam 15' can be determined by summation of moments of the shear forces acting within the beam. More particularly, a beam which is loaded and twisted to an equilibrium condition is subjected to twisting moments having an algebraic sum of zero. Such a relationship is as follows:

V is the internal shear force acting in a particular portion of the beam; and

y is the perpendicular distance from the line of action of the force V through the centroid of the portion of the beam to the X axis (see FIG. 4).

The shear force V is determined according to the relation Vi= f rdA where:

T is the shear stress; and

dA is an incremental area over which the shear stress is distributed. The shear stress 1- is determined according to the relation:

T T W where:

V is the total vertical shear;

Q is the first moment of area about the neutral axis or center of gravity;

1 is the moment of inertia of the beam about the Z axis (see FIG. 4);

and t is the section thickness of the beam material.

The first moment of area Q about the Z axis, is determined according to the relation:

Q= 7 where:

A is the cross-sectional area of a particular portion of the beam; and

Fis the moment arm from that portion of the beam to the Z axis.

For the purposes of illustration the shear force V, in the flange portions 73'b, 74'a will be generally determined. Since the thickness of the material from which the flange is made is uniform, the cross-sectional area of the top horizontal flange (i.e. portions 73b, 74a taken as a unit) is the product of the thickness t of the material and the extent x of the flange along the X axis. The moment arm 12', to the centroid of the top horizontal flange is the distance between the Z axis and a point half way through the thickness of the top flange. Since the distance from the Z axis to the surface 78' is a constant (C,) and the thickness t is a constant, the moment arm 17, is determined according to the relation:

and since:

a t it accordingly:

and, substituting into the formula for determining V,:

L V f dA I t L2 The differential area dA is expressed in terms of X as:

d A t d x H and accordingly:

L V t 1 Yl (inftf where:

the limits L and L are the points on the X axis between which the upper horizontal flange extends.

For any given beam, the shear force V, is determined in terms of the total shear force V by choosing the appropriate limits and solving the above equation. Hence the shear force V, can be defined in terms of the total shear force V by the relation:

VI 1 where:

K, is a constant determined by solution of the general equation for determining V,-with a given beam.

In order to simplify the summation of moments X and Y origins are chosen at a point on the beam at which the shear forces V V (FIG. 4) intersect so that the moment of these forces about that point is essentially zero and the only moments about that point are produced by the shear forces V,,

V and the total shear force V acting through the shear center e It should be noted that even though the shear force V does not act through the X-Y origin the line of action of this force is extremely close to the origin and the moment of V about the origin is negligible.

The shear force V is determined according to the relations set forth above in respect to V,, appropriately modified to take into account the difference in shape and location of the flange portion 73a through which the shear force V acts.

Since the summation of moments acting on the beam is equal to zero, the location of the resultant shear center x, can then be determined from the moment equation:

V is the resultant shear force; and

x is the distance from the Y axis to the shear center; and

E and 3 are the distances from the X axis to the point at which the shear forces V,, V act respectively. Substituting into this relationship:

The quantities K,, K and and are all constant for a particular beam configuration and accordingly the distance from the X axis to the shear center is determinable for a given beam. Since the shear center lies on the plane of the neutral or z axis the location of the shear center is known when x, is determined.

It is further apparent from the foregoing that the distance along the X axis for the shear center can be controlled by varying the extent of the flanges along the X axis, the thickness of the material, the vertical height of the web, etc.; and that a beam can be constructed so that the distance along the X axis for the shear center is such that the shear center lies within or closely adjacent the web of the beam.

Beams constructed in accordance with the foregoing design considerations have a web which is off center with respect to the flanges of the beam. That is, the plane of the web does not bisect the flanges of the beam. Generally speaking the amount the web is off center with respect to the flanges is determined by the nature of the load to be initially applied to the beam; i.e. symmetrical or nonsymmetrical and the magnitude of such load. The beam illustrated in FIG. 4 is designed to receive a load symmetrically applied across the surface 78 of the flanges.

FIG. 4a illustrates the applied nearly symmetrical load L in broken lines with the line of action of the resultant force acting along a line parallel to and spaced slightly to the right of the web. Since the

flanges

73, 74 of the beam 15 are not extremely rigid (due to their relatively light gauge construction), these flanges deflect somewhat under the applied symmetrical load. The flange deflection shifts the applied load to the loaded condition illustrated in full lines in FIG. 4a. The load L, thus shifted, provides a resultant L,, which acts through the web 70'. Since the shear center is located in the web 70' the beam 15' does not twist under the load L.

FIGS. 5 and 6 illustrate modified beams constructed in accordance with the invention wherein the load to be applied to such beams is nonsymmetrical. The beam of FIG. 5 is adapted to support the load on its upper horizontal flange 91, with the load being such that it tends to be distributed as shown by the arrows in FIG. 5. The beam 90 is constructed in substantially the same manner as described in reference to FIG. 4 except for the configurations of the flange portions and the location of the web. The beam 90 includes a top flange 91, a similarly constructed bottom flange 92, having

flange parts

93, 94, respectively. The

flange parts

93, 94 extend from opposite sides of the web 95, with the flange part 93 including portions 93a, 93b and the part 94 including a portion 94a and a bent terminal portion 96.

When subjected to the nonsymmetrical load L (broken lines) the flange portions 93a, 93b, and the web 95 approximate a channel structure having a shear center or axis a,

located on the side of the web 95, from which the parts 94 extend. Under the load L the noted channel tends to twist about the shear axis e in a counterclockwise direction (FIG. The flange parts 9d and the web 95 approximate a second channel which tends to twist clockwise under the load L about a shear center or axis e located on the side of the web 95 between the parts 93. Thus when subjected to the load L' the channel structures tend to twist in opposition to each other about their respective shear axis and accordingly effect one another to prevent twisting of the beam.

The twisting tendency referred to is exhibited by deflection of the flanges under the load so that the load L is shifted and redistributed as indicated in solid lines. The center of gravity of the redistributed load is located so that the resultant of the load acts through the shear center a of the beam which, as above, is located in the web.

FIG. 6 illustrates a beam 100 having a top flange horizontal flange 1011 supported a load L" originally distributed nonsymmetrically (broken lines) over the top flange of the beam as shown by the arrows in FIG. 6. The'beam 100 also includes a web 102 and lower horizontal flange 103. The

flanges

101, 103 are integral with the web 102 and each includes

flange parts

104, 105 respectively. When the nonsymmetrical load L" is applied the flange parts 1.04, 105 deflect under the load to redistribute the load (solid lines). This shifts the line of action of the load resultant to act through the shear center e located in the web 102. As noted previously when the load resultant acts through the shear center the beam does not twist.

The beams of FIGS. 5 and 6 are designed for structural installations rather than a pallet rack'as described in reference to FIGS. 1-3. These beams are usable in buildings or other structures where loadings of the beam are relatively constant as opposed to the variable loads which might be applied to the beams of a pallet rack. The configurations of these beams are determined according to the formula discussed above in connection with the beam of FIG. 4.

METHOD OF CONSTRUCTION OF THE BEAMS Wide flange sheet metal beams according to the invention are preferably constructed by rolling a continuous strip of the sheet material as it is fed through a rolling mill. After determining the necessary material thickness, vertical beam height and flange dimensions to produce a shear center within or adjacent the web of the given beam, the rolling equipment is set up to produce a beam having the desired configuration.

In producing, for example, the beam of FIG. 4, the material thickness, vertical beam height and flange dimensions are determined to provide a shear axis or'center which is within the web of the beam. The rolling equipment is set up to receive the sheet steel strip and roll the material adjacent the upper and lower edges of the web to produce the flange por tions 93a. The flange forming material is then rolled to provide the radiused bend at the outermost extremity of the portion 030, and is bent back upon the portion 930 adjacent the web to define the portion 93b of the flange part 93.

The sheet material forming the flange portion 94a is continuous with the portion 93b and is formed to extend from the portion 93b in the opposite direction from the flange part 93, transversely of the web. The flange part 94 is then deformed at its terminus to define a stiffening bend which is disposed a greater distance from the web than the radiused bend interconnection the portions 93a, 93b of the flange part 93.

Because of differing requirements 'of users of such beams it is necessary to produce a number of beam sizes. The most desirable method of producing beamshaving differing sizes is by changing the vertical dimension of the web. Thus families of beams constructed in accordance with the invention can be produced. Each beam in a family will have the same flange construction and the same relationship between flanges and web with the difference between members of the family residing in differing vertical web dimensions.

As has been noted previously the shear center for a beam is determined from the cross-sectional geometry of the beam. Accordingly a family of beams might include two or more beams having a shear center spaced slightly from the web. For example beams constructed according to the invention from 13 gauge sheet steel (0.090 inch thickness) have been constructed through a range of vertical heights in which the shear center was located 0.10 inch from the web centerline at the extremes of the range. Such beams exhibited a maximum of 2 twist about the neutral axis under a load applied over a 10 foot span.

Although the invention has been described in its preferred form with a certain degree of particularlity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim: 1

l. A unitary wide flange sheet metal beam comprising:

a. an asymmetrical flange structure including a load engaging flange portion;

b. a web disposed transversely to said load engaging flange portion; 1

c. a second flange portion continuous with both said web and said load engaging flange portion and extending generally transversely from said web to a terminus of said load engaging flange portion;

d. said load engaging flange portion extending from said one terminus to another terminus beyond said web;

e. said web disposed along a plane intersecting said load engaging flange portion along a line which is closer to one of said load engaging flange termini than to said other load engaging flange terminus thereby positioning the shear axis of the beam parallel to said web plane;

f. said first and second flange portions engaged adjacent said web plane to transmit load forces to said web;

g. said flange structure reacting to an applied load to tend to twist said beam slightly thus redistributing said lead on said load engaging flange portion; and,

h. the twisting tendency of said beam terminating when the resultant of said redistributed load acts through said shear axis. I

2. A beam as defined in claim 1 wherein the location of said shear axis relative to said web centerline is such that said web twists a maximum of 2 from the plane of its relaxed condition.

3. A beam as defined in claim 1 and further including a radiused bend connecting said flange portion and said flange, said radiused bend located at said first mentioned terminus.

4. A beam as defined in claim 1 wherein said radiused bend is located a substantially lesser distance from said web than the other terminus of said flange.

5. A beam as defined in claim 4 wherein said flange deflects slightly under an applied nonsymmetrical load to shift said load to increase the proportion of said load supported by said flange adjacent said radiused bend.

6. A beam as defined in claim 3 wherein said radiused bend is located a substantially greater distance from said web than said other terminus.

7. A beam as defined in claim 3 and further including support structure for said beam operative to apply a twisting moment to said beam when loaded, said support structure being effective to urge one terminus of said flange toward engagement with the load to increase the proportion of said load supported by said flange adjacent said terminus.

8. a beam as defined in claim 7 wherein a symmetrical load applied to said beam is shifted to a nonsymmetrical load in response to said support structure twisting said beam.

9. A pallet supporting rack comprising:

a. a plurality of vertically disposed support members;

b. wide flange sheet metal pallet supporting beams extending horizontally between said members;

c. said beams each formed from a single sheet of metal and including a web and flanges extending transversely of the plane of said web;

. said flanges each being asymmetrical about the plane of said web and each including;

l. a first flange part comprising a folded section of said sheet metal formed by a connecting flange portion extending from said web and a load engaging flange portion folded back upon said connecting flange portion and extending transverse to the plane of said web,

2. a second flange part extending beyond said web plane oppositely from said first flange part, said second flange part continuous with said load engaging flange portion of said first flange part, and

3. said connecting flange portion and said load engaging flange portion engaged adjacent said web plane for transmitting load forces to said web from said flange;

e. means for supporting each of said beams on said members including at least a part operative to exert a twisting moment on the associated beam when said beam supports a pallet;

. said part engaging a vertically disposed support member at a location spaced laterally from said web whereby to exert said twisting moment on said beam; and

g. said beam defining a shear axis extending along said web remote from said flanges and said first and second flange parts being flexible under load whereby when a pallet is supported on the flange parts of one of said flanges said beam tends to twist slightly and the resultant of said load acts through said shear axis to terminate the twisting tendency of said beam.

10. A pallet rack as defined in claim 9 wherein said part is a clip member attached to said beam and removably secured a respective vertical support member.

11. A pallet rack as defined in claim 10 wherein said clip includes support surfaces engaged with said members at locations spaced laterally from said plane of said web.

12. A pallet rack as defined in claim 11 wherein said surfaces form the sole supporting connections between said beams and said members.

13. A one-piece sheet metal l-beam comprising:

a. top and bottom flange constructions one of which is a load engaging flange;

b. a web extending between said flange constructions;

c. structure for transmitting load forces between said load engaging flange construction and said web, said structure including engaged force transmitting surfaces on said load engaging flange, said surfaces located adjacent said web and spaced from opposite lateral sides of said load engaging flange;

d. said top .and bottom flanges each being asymmetrical about the plane of said web;

e. said beam having a shear axis located adjacent said web;

f. said sheet metal being of relatively light gauge; and

g. said load engaging flange construction of said beam deflectible under load to shift the load and thereby cause the line of action of the resultant load force to extend through said shear axis.

14. A beam as defined in claim 13 wherein said shear center is spaced from said centerline of said web portion a maximum distance approximately equal to the sectional thickness of said sheet metal.

15. A one-piece sheet metal l-beam comprising:

a. a substantially planar web;

b. a flange extending transverse to the plane of said web and defining a first flange part extending from one side of said web plane and a second flange part extending oppositely of said first flange part from aid web plane;

c. said first flange part comprising a folded section of said sheet metal including;

l. a connecting flange portion connected to said web along a first bend line extending along said web and extendin substantially normal to said web plane, l 2. a loa engaging flange portion continuous with said connecting flange portion and folded back upon said connecting flange portion to extend transversely of said web plane,

3. a second radiused bend interconnecting said load engaging flange portion and said connecting flange portion and defining a terminus of said first flange part, and

4. said connecting flange portion and said load engaging flange portion engaged between said first and second bends for transmitting load forces to said web;

d. said second flange part comprising a single thickness of the sheet metal material continuous with said load engaging flange portion and which extends beyond said web plane from said first flange part;

e. said second flange part defining a second terminus of said flange remote from said web plane; and

f. one of said flange parts flexing more than the other flange part in response to the application of a load on said beam whereby the applied load is redistributed on said flange to prevent substantial twisting of said beam under said load.

16. An l-beam as claimed in claim 15 and further including a stiffening lip extending from said second terminus parallel to said web.

Claims

1. A unitary wide flange sheet metal beam comprising: a. an asymmetrical flange structure including a load engaging flange portion; b. a web disposed transversely to said load engaging flange portion; c. a second flange portion continuous with both said web and said load engaging flange portion and extending generally transversely from said web to a terminus of said load engaging flange portion; d. said load engaging flange portion extending from said one terminus to another terminus beyond said web; e. said web disposed along a plane intersecting said load engaging flange portion along a line which is closer to one of said load engaging flange termini than to said other load engaging flange terminus thereby positioning the shear axis of the beam parallel to said web plane; f. said first and second flange portions engaged adjacent said web plane to transmit load forces to said web; g. said flange structure reacting to an applied load to tend to twist said beam slightly thus redistributing said load on said load engaging flange portion; and, h. the twisting tendency of said beam terminating when the resultant of said redistributed load acts through said shear axis.

2. A beam as defined in claim 1 whErein the location of said shear axis relative to said web centerline is such that said web twists a maximum of 2* from the plane of its relaxed condition.

2. a load engaging flange portion continuous with said connecting flange portion and folded back upon said connecting flange portion to extend transversely of said web plane,

3. said connecting flange portion and said load engaging flange portion engaged adjacent said web plane for transmitting load forces to said web from said flange; e. means for supporting each of said beams on said members including at least a part operative to exert a twisting moment on the associated beam when said beam supports a pallet; f. said part engaging a vertically disposed support member at a location spaced laterally from said web whereby to exert said twisting moment on said beam; and g. said beam defining a shear axis extending along said web remote from said flanges and said first and second flange parts being flexible under load whereby when a pallet is supported on the flange parts of one of said flanges said beam tends to twist slightly and the resultant of said load acts through said shear axis to terminate the twisting tendency of said beam.

4. said connecting flange portion and said load engaging flange portion engaged between said first and second bends for transmitting load forces to said web; d. said second flange part comprising a single thickness of the sheet metal material continuous with said load engaging flange portion and which extends beyond said web plane from said first flange part; e. said second flange part defining a second terminus of said flange remote from said web plane; and f. one of said flange parts flexing more than the other flange part in response to the application of a load on said beam whereby the applied load is redistributed on said flange to prevent substantial twisting of said beam under said load.

9. A pallet supporting rack comprising: a. a plurality of vertically disposed support members; b. wide flange sheet metal pallet supporting beams extending horizontally between said members; c. said beams each formed from a single sheet of metal and including a web and flanges extending transversely of the plane of said web; d. said flanges each being asymmetrical about the plane of said web and each including;

13. A one-piece sheet metal I-beam comprising: a. top and bottom flange constructions one of which is a load engaging flange; b. a web extending between said flange constructions; c. structure for transmitting load forces between said load engaging flange construction and said web, said structure incLuding engaged force transmitting surfaces on said load engaging flange, said surfaces located adjacent said web and spaced from opposite lateral sides of said load engaging flange; d. said top and bottom flanges each being asymmetrical about the plane of said web; e. said beam having a shear axis located adjacent said web; f. said sheet metal being of relatively light gauge; and g. said load engaging flange construction of said beam deflectible under load to shift the load and thereby cause the line of action of the resultant load force to extend through said shear axis.

15. A one-piece sheet metal I-beam comprising: a. a substantially planar web; b. a flange extending transverse to the plane of said web and defining a first flange part extending from one side of said web plane and a second flange part extending oppositely of said first flange part from aid web plane; c. said first flange part comprising a folded section of said sheet metal including;

16. An I-beam as claimed in claim 15 and further including a stiffening lip extending from said second terminus parallel to said web.