Abstract:
A slotted channel with a supplemental flange as a building member has at least one supplemental flange extending from at least one slot in the member web or primary flanges yielding a building member with increased strength, both compressive (longitudinally) and in shear (transverse). The slotted member presents a reduced area through which heat or sound may be conducted and slots in which insulation is received, both increasing resistance to heat and sound transfer.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to steel trusses and joists comprising parallel flanges extending orthogonally from web sides, and more particularly to a truss or a joist with at least one slot in the web or primary flanges and including supplemental flanges extending from slot sides.  
         [0003]     2. Prior Art  
         [0004]     Interior wall construction using horizontal channel beams as headers and footers and matching vertical studs received into the channel beams is well-known. Commonly, the studs are also channel-shaped and both are made of metal, typically cold formed metal and more typically steel. Similarly, metal buildings employ girts (sidewall bracing) and perlins (roof bracing). Roof rafters, headers, footers, beams, and joists and trusses comprised of a plurality of similar elongate components can also employ channel shaped members. All of these building components have in common that they are elongate and straight, including the truss comprising a plurality of elongate building components. For purposes of simplicity of description, they are collectively referred to as a “beam” unless otherwise indicated in the context. That is, for purposes herein, the description referencing a beam should be deemed to include and apply to each and all elongate building components, specifically including those listed and also including the elongate building components of which a truss is comprised. For purposes herein, reference may be made to metal or steel beam. These terms are not meant to be restrictive or limitations but are meant illustratively and generically to be synonymous and to include all materials from which such studs may be formed.  
         [0005]     Of all modes of failure, buckling (Euler or local) is probably the most common and most catastrophic. That is, a structure may fail to support a load when a member in compression buckles, that is, moves laterally and shortens in length. A steel beam may be described for these purposes as a slender column where its length is much greater than its cross-section. Euler&#39;s equations show that there is a critical load for buckling of a slender column. With a large load exceeding the critical load, the least disturbance causes the column to bend sideways, as shown in the inserted diagram, which increases its bending moment. Because the bending moment increases with distance from a vertical axis, the slight bend quickly increases to an indefinitely large transverse displacement within the column; that is, it would buckle. This means that any buckling encourages further buckling and such failure becomes catastrophic. 
         
 
         [0006]     The traditional steel beam construction comprises a pair of parallel flanges extending orthogonally from a web. Commonly the flange distal end bends inward slightly to increase the compressive stability converting the flat two-dimensional flange into a three dimensional structure. For these purposes, “compressive stability, strength or stress” means a reference value that measures the load a structure can sustain before it buckles or otherwise deforms and loses support for a load.  
         [0007]     Such beams are very poor energy conservers. For example, for internal walls the metal beam acts as a thermal conduit and actually enhances thermal conductivity across the wall over wood and other materials. In metal buildings the beams (girts and perlins) are in direct metal-to-metal contact with the outside material sheeting and become conduits of heat on the outside sheeting to inside the building. Heat passes through the web, so one interested in reducing thermal conductive might consider removing material from the web to create slots in the web. To the extent such slots remove metal and thus reduce the thermal path, the beam is less conductive thermally. Also, such slots may receive insulation that further impede conductivity.  
         [0008]     Similarly, a steel beam is a good acoustic conductor, which is detrimental in many applications. It has long been desired to reduce sound transmission through metal wall beams. As in thermal conductivity, re-shaping of a significant portion of the web or the flanges will reduce the acoustic conductivity of the beam and therefore the wall.  
         [0009]     It is a primary object of the present invention to enhance the compressive stability, strength and bending resistance of a traditional steel beam. It is another object to reduce thermal conductivity and acoustical transmission, of the beam while enhancing the bending resistance and compressive stability and strength. To this end, it is a further object to introduce one or more slots in the beam web that interrupt conductivity across the web in combination with projections from the web at the slots additional to the primary flanges that enhance the load that a beam can support under bending and compression.  
       SUMMARY  
       [0010]     These objects are achieved in a first embodiment in a beam having at least one supplemental flange of a substantial I areal dimension extending from a side of a corresponding slot in the web. These objects are also achieved in a second embodiment in a beam having a plurality of small holes punched in the beam leaving punched web or flange material projecting from the punched hole.  
         [0011]     These supplemental flanges are formed by stamping out a flange in the web on three flange sides and then bending the supplemental flange away from the web on the fourth, uncut side, forming a slot in the web. The result then is a supplemental flange extending from the web at the slot edges. Typically, the supplemental flange usually extends normal to the web and parallel to the primary flanges extending from the web edges, although it can be angled from the web other than normal. The slot in the beam web presents a reduced web area through which heat or sound may be conducted.  
         [0012]     The flange is formed as the slot is formed by cutting the web for the slot, dividing the intended slot area of the web into two equal side by side panels in the center and top and then folding the panels out from the plane of the web simultaneously forming the slot and a continuous supplemental flange. Alternatively, the slot area can be cut (stamped) with a U cut at the slot top and an inverted U at the slot bottom joined by a center cut between them. The top and bottom U panels are then folded outward to form horizontal supplemental flanges at the slot top and bottom and the side panels are folded out to form vertical supplemental flanges.  
         [0013]     Rather than weaken the beam at the slot, the beam is in fact strengthened through a few mechanisms. First, the longitudinal extent of the web of a traditional beam presents a large vertical plane susceptible to local shear buckling under load that can lead to Euler bucking. Introducing slots having supplemental flanges into the web reduces that extent. That is, the Supplemental Flange Beam (“SFB”) itself actually stiffens the web plane by creating smaller flat planes in the web plane than are present in standard steel studs thus increasing local shear buckling resistance.  
         [0014]     The calculation discloses that for vertical loading the SFB provides better stability in buckling resistance due to the center of gravity being moved away from the plane of the web toward the opening of the channel section. This effect distributes the vertical load more uniformly over the SFB cross-sectional area; rather than mostly in the web as standard steel studs do; and thus forcing local buckling effects to require a higher vertical loading than standard steel studs can handle. The SFB also enhances resistance to Euler buckling (long column lateral deflection) by the new properties the supplemental flanges provide. In short, for the beam to bend at the slot, both the supplemental and primary flanges orthogonal to the web must also bend, but with the supplemental flanges, there is increased resistance to that bending.  
         [0015]     The supplemental flange can be either continuous (fully encompassing the slot) or discontinuous (not completely encompassing the slot) although the former will provide for greater strength and structural stability than the latter. When all the original material in a traditional metal stud, or other beam, remains in the final SFB product, in the case of supplemental flanges extending from the full length of slot sides the SFB retains more than the total cross-sectional area of the traditional stud, which retains its support for compressive loads and provides additional rigidity that equates to better stability than traditional steel studs (other comparable beams). This is demonstrated in both the x-axis and y-axis bending calculations below.  
         [0016]     Calculations confirm that adding the supplemental flange to the flange at the slot sides and ends not only fully offsets any loss of compressive strength caused by the slot but actually increases it over the unmodified beam without slots or supplemental flangesbeam. That is, the beam can sustain a greater compressive, or longitudinal, or bending load with slots and supplemental flanges than without them. The following calculation is typical: 
 
The following calculation assumes a 16 gauge “C”-Section Channel, 6″×2½” (0.0598″ wall thickness) beam. 
 
         [0017]     The strength of a load-supporting column can be represented by the moment of inertia about the major axis, X-X, where buckling could occur first. When the moment reaches a high enough value, known as the Euler Buckling under load the column will buckle. This value is proportional to the moment of inertia, so the higher the moment of inertia, the more load the column will sustain before buckling.  
         [0018]     The following equation calculates the moment of inertia (in 4 ) about the X-X axis for a channel cross-sectional area. The designated sections are as represented in  FIG. 27 .  
         I     x   -   x       =       2   ⁢     (       A   1     ⁢     d   1   2       )       +     2   ⁢     (       A   2     ⁢     d   2   2       )       +     2   ⁢     (       b   ⁢           ⁢     h   3       12     )       +     2   ⁢     (       A   3     ⁢     d   3   2       )       +     2   ⁢     (       A     4   ⁢               ⁢     d   4   2       )             
 
 where 
    h=0.0598 inch, the thickness of 16-gauge cold formed steel.     b=width of various sections. For the calculation of I x-x , it will be determined from a central axis between the two widths, 2.50 inches, 1.00 inch, and perpendicular to the 0.375 inch dimension. For the calculation of I y-y , it will be determined by an axis transverse to the two width dimensions, 2.50 inches, 1.00 inch, and parallel to 0.375 inch dimension.     d=distance (in) from the neutral axis to each centroid of an area “A”, respectively.    
 
         [0022]     The neutral axis is located at the centroid or center of gravity, CG, of the beam. It is determined using the equation, 
 
 CG   y-y   i   =yA   i   /A   t  
 
         [0023]     where A i  represents the cross-sectional area of each area that makes up the total cross-sectional area, A t .  
                                             TABLE 1                       Component   A, area (in 2 )   y (in)   yA (in 3 )                                A-1   0.0598)(2.5()2 = 0.2990   1.25   0.374        A-2   (0.0598)(1)2 = 0.1196   0.5   0.0598       A-3   (0.0598)(2)(2) = 0.2392   0.0299   0.0072       A-4   (0.0598)(0.375)2 = 0.0449   2.5   0.1123       Totals   A t  = 0.7027       yA i  = 0.5533                  
 
         [0024]     Using the values in the Table 1 to compute CG, CG y-y =yA/A=(0.5533)/(0.7027)=0.7868 inch from the inside face of web. With this information the values for I x-x  and I y-y  of the supplemental flange beam can be calculated.  
         I     x   -   x       =         2   ⁢     (       A   1     ⁢     d   1   2       )       +     2   ⁢     (       A   2     ⁢     d   2   2       )       +     2   ⁢     (       b   ⁢           ⁢     h   3       12     )       +     2   ⁢     (       A   3     ⁢     d   3   2       )       +     2   ⁢     (       A     4   ⁢               ⁢     d   4   2       )         =         2   ⁢     (   0.0598   )     ⁢     (   2.5   )     ⁢       (   2.9701   )     2       +     2   ⁢     (   0.0598   )     ⁢     (   1.0   )     ⁢       (   1.0   )     2       +     2   ⁢     (         (   0.0598   )     ⁢       (   2.0   )     3       12     )       +     2   ⁢     (   0.1196   )     ⁢       (   2   )     2       +     2   ⁢     (   0.0224   )     ⁢       (   2.8125   )     2         =     4.15   -       inch   4     .               
 
 To determine the percentage increase in load that stud with supplemental flanges can sustain, we next compute the moment of inertia about beammajor X-X axis of a standard steel beam (without the advantage of the supplemental flanges). Substituting the values as before,  
         I     x   -   x       =           (       bh   3     12     )     ss     +     2   ⁢     Ad   ss   2       +     2   ⁢       (       bh   3     12     )     ss       +     2   ⁢     Ad   ss   2         =         (       0.0598   ⁢       (   6.0   )     3       12     )     +     2   ⁢     (   0.0598   )     ⁢     (   2.5   )     ⁢       (   3.0   )     2       +     2   ⁢     (       0.0598   ⁢       (   0.375   )     3       12     )       +     2   ⁢     (   0.0598   )     ⁢     (   0.375   )     ⁢       (   2.8125   )     2         =     3.23   -       inch   4     .               
 
         [0025]     The percentage improvement in the beam with supplemental flanges is [(4.15−3.23)/(4.15)](100), or 22.3% stronger than an equivalent standard steel beam.  
         [0026]     It has also been determined that resistance to local shear deflection of the beam is also enhanced for the slotted beam with supplemental flanges extending from the web at slot sides. That is, the beam with supplemental flanges also supports a greater lateral load, or a load placed intermediate a nonvertical beam directly on the web, on a slotted metal beam with supplemental flanges than on a metal beam without these features.  
         [0027]     Though the beam is structurally enhanced by the supplemental flanges as discussed above, perhaps the most advantageous contribution of the supplemental flanges is that the web can be slotted without diminishing the structural integrity of the beam, and in fact providing an enhanced structure. The slots interrupt heat (and acoustical) flow through the web across the wall employing the beam. Prior to the described slotted beam with supplemental flanges, metal beams were disfavored because they are a poor insulator; in fact, they are a good conductor, defeating efforts for energy conservation and noise containment. Wood remained the preferred material because of the low conductivity of wood. For example, the “R” factor for wood (fir, pine, and spruce) for a 2″×6″ stud is 361 K/w. [1 W/mK=0.578 BTU/Hr−ft−° F.]. The “R” factor for a steel same-sized slotted stud is 846 K/W. The rate of heat loss through the wood stud is 0.055 W and through the slotted steel stud is 0.024 K/W, or less than half. The steel stud immediately becomes competitive and even advantageous. In addition, instead of air in the slot, which conveys heat by convection, insulation can be added. The slotted beam enhanced structurally by the supplemental flanges and thermally by the slots and insulation in the slots thus becomes an attractive wall construction alternative. It is clear that the open slot left in the SFB that is created by the supplemental flange manufacturing process can vary in width and length depending on the requirements needed from the SFB. Changes in this width and length will affect the various geometric properties 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a perspective view of slots longitudinal in the web of joists and trusses and supplemental flanges extending from the slot sides, shown in a building structure.  
         [0029]      FIG. 2  is a front view of metal beam (stud, joist or truss component) with a web with a slot aligned vertically in the web with a supplemental flange continuous around the slot perimeter.  
         [0030]      FIG. 3  is a back view of the beam of  FIG. 2 .  
         [0031]      FIG. 4  is a front view of metal beam (stud, joist or truss component) with a web with a plurality of slots aligned vertically in the web with a supplemental flange extending from each slot side.  
         [0032]      FIG. 5  is a back view of the beam of  FIG. 4 .  
         [0033]      FIG. 6  is a rear perspective view of a beam showing a plurality of circular slots with supplemental flanges circumferential about the slots.  
         [0034]      FIG. 7  is a front perspective view of the beam of  FIG. 6 .  
         [0035]      FIG. 8  is a top planar view of the beam of  FIG. 6 .  
         [0036]      FIG. 9  is a rear perspective view of a beam with a slotted web having supplemental flanges extending inward from primary flanges.  
         [0037]      FIG. 10  is a front perspective view of a beam of  FIG. 9 .  
         [0038]      FIG. 11  is a top planar view of the metal beam of  FIG. 9 .  
         [0039]      FIG. 12  is a front perspective view of beam showing a plurality of slots with a supplemental flange extending from a first side of a slot and from the other side of a next adjacent slot.  
         [0040]      FIG. 13  is a rear perspective view of a beam showing a plurality of slots each with a supplemental flange continuous around the perimeter of each slot, the slots arrayed in two columns longitudinal in the web with a slot of one column adjacent a slot of the other columns.  
         [0041]      FIG. 14  is a rear perspective view of the beam of  FIG. 13 .  
         [0042]      FIG. 15  is a perspective view of a metal beam shown with an array of slots, each slot having a supplemental flange continuous around the slot perimeter, the slots arranged in a plurality of columns longitudinal with the beam with slots of one column staggered from slots of an adjacent slot.  
         [0043]      FIG. 16  is a perspective view of the beam of  FIG. 3  with primary flanges inset from bridge sides.  
         [0044]      FIG. 17  is a perspective view of a truss comprising a plurality of slotted beams with supplemental flanges.  
         [0045]      FIG. 18  is a plan view of many truss configurations existing in the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0046]     The slotted metal beam  10  is intended for use in conventional building construction, such as a stud in a wall, building joists and trusses. In the conventional manner of wall and building construction, a plurality of studs is spaced apart vertically in parallel between horizontal floor joists and ceiling joists  100 . Typically, a channel stud header  102  connected to the ceiling joists  100  and opening downward receives upper ends  11  of the studs  10 . Similarly, a channel stud footer  104  connected to the floor joists  100  and opening upward receives lower stud ends  13 . Because the joists  100  are required to support a lateral, or transverse load, they may be larger and stronger than the studs  10 , which support a compressive, or longitudinal load.  
         [0047]     The beam  10  comprises a conventional C-shaped channel  12  including a pair of parallel primary flanges  14  extending a same extent orthogonally from and separated by a web  16 . In the preferred embodiment, at least one and preferably a plurality of slots  18  are stamped in the web  16  such that at least one and preferably two supplemental flanges  20  bend out of the slot  18  from first and second slot sides  22 ,  23  bounding the slot  18  to extend inward, between and parallel to the primary flanges  14 . In this manner, the supplemental flanges  14  comprise a substantial areal portion, and typically a third, of the web  16  bending from the web to form the slot. The slots  18  may be arrayed in one or more columns  19 . Two or more columns  19  may be configured with slots  18  side by side in adjacent slot columns as shown in  FIGS. 13, 14 , and  15  or with slots  18 ′ of one column  19 ′ staggered between or overlapping slots  18 ″ of an adjacent column  19 ″.  
         [0048]     Preferably, the supplemental flanges  20  are similar, symmetrically extending inward from the web  16  from said slot sides  22 ,  24 . Thus, each supplemental flange  20  will be in length between its proximal end at the web to its distal end a distance equal to half of the width of the slot  18 . (In a minor variation, the web  16  is stamped to form a slot  18  with a single supplemental flange  20 ′ that bends inward from a slot side  22 ,  24 , in which case the length of the supplemental flange  20 ′ is the width of the slot  18 .) Though the supplemental flange preferably extends orthogonally from the web, it can also extend from the web at any angle other than perpendicular to the web, as shown in  FIG. 26 .  
         [0049]     Typically, the supplemental flanges  20  comprise a major portion, and even most of the web  16  bending inward between the primary flanges  14  forming the slot  18  and the supplemental flanges  20  therein substantially moving the beam  10  cross sectional center of gravity away from the web  16  therein substantially transferring load support from the web  16  to the primary flanges  14 . In the preferred embodiment shown in  FIG. 12 , a supplemental flange  20  extends from each side  22 ,  24  of a plurality of slots  18  aligned vertically in the web  16  maintaining symmetry in the beam  10  for uniform load support through the beam  10 . In an alternative embodiment, a first supplemental flange  20 ′ extends from the web  16  at a first slot side  22  of a first slot  18   a,  a second supplemental flange  21 ′ extends inward from the web  16  at a second slot side  24  of a second slot  18   b,  the second slot  18   b  being adjacent said first slot  18   a,  a third supplemental flange  20 ″ extends from the web at the first slot side  22  of a third slot  18   c,  the third slot  18   c  being adjacent the second slot  18   b,  and a fourth supplemental flange  21 ″ extends inward from the web  16  at the second slot side  22  of a fourth slot  18   d  adjacent the third slot  18   c,  the fourth slot  18   d  being adjacent the third slot  18   c  such that the supplemental flanges  20 ′,  21 ′,  20 ″,  21  ″ for successive adjacent slots alternate between extension from first and second slot sides  22 ,  24 . The alternating pattern continues through the web  16  such that there are the same number of supplemental flanges  20 ,  21  on each of the slots&#39; first and second sides  22 ,  24 . Thus configured, the supplemental flanges  20 , which are all similar and all between the primary flanges  14 , extend further away from the web  16 , therein further moving the beam cross sectional center of gravity away from the web  16  more effectively transferring load support from the web  16  to the primary flanges  14 .  
         [0050]     Although the preferred embodiment is for the supplemental flanges  20  to extend inward such that the beam center of gravity is moved inward the beam and away from the web  16 , thereby transferring more of the beam support from the web  16  and onto the primary flanges  14 , the supplemental flanges  20  may also bend outward, away from the beam  10 . As discussed, there is a structural advantage to moving the center of gravity inward in that the load on the beam is better distributed to the flanges instead of mostly on the web. Similarly, there is also a structural advantage in having the supplementary flanges  20  outward from the web. As given above the primary component in the beam moment of inertia of primary consequence is the term, I=b h 3 /12 where b is the beam base (web dimensional direction), and h is the height (flange directional direction). It is seen that increasing the height even a small amount dramatically increases the beam strength. Thus for a beam beginning with a 2-inch flange and increasing it by 2 inches by extending a supplemental flange outward from the web, the beam strength increases by a factor of 4 3 /2 3 , or 64/8=8. It may also be advantageous for some supplemental flanges to bend inward and some outward.  
         [0051]     In one of the embodiments, the slot is rectangular and supplemental flanges  20  extend from the slot  18  either vertically, parallel with the primary flanges, or horizontal, orthogonally to the primary flanges  14 . However, other variations in slot shape are deemed included in the invention. For example, the slot ends (top and/or bottom) may be of triangular shape each with two supplemental flanges bent and extending from the legs of the. Similarly, the slot top and/or bottom may be curvilinear, such as a semicircle, with a plurality of relatively small supplemental flanges extending from the slot ends. Alternatively, the slot may be punched out from its center to produce a continuous and uninterrupted supplemental flange around an oval. In a further embodiment, the beam (stud, or truss, etc.)  10  may comprise one or more slots  18  in one or both primary flanges  14  with one or more supplemental flanges  20  extending into the beam  10  as shown in  FIGS. 9-11 . The illustration shows a circular supplemental flange  20 , representative of the various alternative configurations of flanges extending from a slot in a primary flange as described above for web based supplemental flanges, all of which are deemed included in this invention.  
         [0052]     With the supplemental flanges  20  formed out of the web  16  from web material removed and folded from the web  14  to form the slots  18 , the amount of beam material remains unchanged from a traditional metal beam. Thus, the dimensions of the supplemental flanges in the various configurations described above are defined by the dimensions of the slot from which it bends. That is, two supplemental flanges extending from the two slot sides may each be half the width of the slot. If there are flanges extending from respective ends of a rectangular slot, the side supplemental flanges are reduced in length equal to the sum of the extent of the top and bottom supplemental flanges. In maintaining the same amount of material in the beam, the beam does not reduce in support strength but in fact increases in support strength as calculated above.  
         [0053]     A pair of slots  10  in the web  16  are separated by a bridge  70 . The insulation properties of the beam  10  are improved with a bridge hole  72  in the web  16  outside of the slots  10  on respective bridge ends  74 , precluding a straight heat path across the bridge  70  between web sides  11 . A similar bridge hole  72  is advantageous at the top or bottom, or both top and bottom, of the beam respectively above and below the slot. The bridge hole  72  is advantageously diamond shape for structural enhancement with diamond diagonals horizontal and vertical, typically. A supplemental hole  76  similar to the bridge hole  72  is advantageously placed in the supplemental flange  20 , which reduces the weight of the beam without losing beam structural integrity. (The term “bridge” refers generally to a bridge between two longitudinally slots and likewise the “bridge hole” refers generally to a hole at one or more bridge ends, all of which may be located in fact in the web, a primary flange, or a supplemental flange.)  
         [0054]     It is to be understood that the beams described hereinabove as beams are in fact straight building components that can be employed in other building capacities, such as joists and as beams of a truss  80 . The figures provide a number of examples of trusses but that are provided as illustrative only of the many configurations that can be designed from a plurality of beams.  
         [0055]     A truss  80  is constructed from a plurality of beams  10 . For purposes herein, the truss  80  includes any and all structural frames based on the geometric rigidity of the triangle and comprising beams subject to longitudinal compression, tension, or both and so configured to make the frame rigid under loads.  
         [0056]     Several figures have been provided as illustrative of various embodiments of the invention. The figures are for illustrative purposes only and not as limitations of the invention. A feature illustrated on one figure can be implemented in another configuration or in combination with another configuration. For example, an array of circular slots are deemed to include all possible shapes of slots in an array configuration and not limited to circular slots. Similarly, a figure may show a slot shape with a supplemental flange extending inward from the web or a primary flange and another slot shape or supplemental flange in the same or an alternative configuration extending outward from the web. It should be understood that any slot or supplemental flange shape may be configured to extend inward or outward or in any configuration represented as a feature in another figure by another shape.  
         [0057]     In another embodiment the beam primary flanges  14  bend inward from web sides  11  and then bend again away from the web such that the primary flanges are offset inward from web sides  11 . The primary flanges then bend outward at primary flange ends  15  to a plane  200  orthogonal to respective web sides  11  providing a gap  82  between each primary flange  14  and the respective plane  200  as shown in  FIG. 16 . Thus, when a planar panel (not shown) is installed against a beam side  13 , air gap  82  is created between the panel and the primary flange  14  with the only contact with the beam being between web sides  11  and the end of the primary flange  15 , thus reducing heat transfer from the panel to the beam  10 . Advantageously the gap  82  may also be filled with insulation to further reduce heat transfer.