Load support structure

The load support structure includes a compression member joined adjacent its ends to the end portions of a tension member. A foam plastic is disposed between said members and bonded to the juxtaposed surfaces of said members so that force applied to one of said members will be resisted by the shear and tension modulus of the foam plastic whereby the load support structure can support increased loads. The support structure may be the floor in a storage housing.

BACKGROUND 
In U.S. Pat. No. 4,030,265, there is disclosed an arch beam comprised of a 
low modulus filler between a compression member and a tension member. 
Thus, the arch beam in said patent bears a superficial resemblance to the 
present invention. In said patent, the resistance of the compression 
member is increased by utilizing the compression strength of the low 
modulus filler. In said patent, the support points 20 and 21 are spaced 
apart by a distance which is smaller than the distance between the focus 
points. In said patent, reaction blocks 18 and 19 are utilized to 
distribute stress concentration from the reaction forces at the support 
points. The present invention is directed to a different class of 
structures from that disclosed in said patent. 
SUMMARY OF THE INVENTION 
The load support structure includes a load bearing face sheet, an opposed 
face sheet functioning as a tension member, and a contoured compression 
member therebetween. Support means are focally joined with the end portion 
of the compression and tension members, whereby they may react to face 
loads with minimum residual bending moments. A foam plastic, filling all 
internal space, is bonded to all surfaces contacted thereby. There are 
thereby established elastic foundations situated above and below the 
compression member which resist bending motions of said member. The upper 
foundation also provides a distributive connection between the loaded face 
sheet and other members. Bonding of the foam at all interfaces enables the 
shear, tension, and compression moduli of the foam, as well as the 
stiffness of the face sheet and tension member, to increase the resistance 
of the foundations to bending motions of the compression member. The 
resulting constraint of bending motions of the compression member allows 
increased loading on the face sheet. 
In an alternate construction the load support structure does not include 
the load bearing face sheet nor the foam plastic filler above the 
compression member. Loads are applied directly to the compression member. 
The elastic foundation below the compression member functions as described 
above. 
An operative embodiment of the present invention incorporates the load 
support structure as the bottom wall of a storage container such as an ice 
bin. The compression member and tension member are preferably provided 
with a rough zinc coating so as to provide a surface to which the foam 
will readily bond. If the foam is not bonded to the juxtaposed surfaces of 
the compression members, tension member and face sheet, only the 
compression modulus of the foam may be utilized. When the foam is bonded 
to the juxtaposed surfaces of the compression and tension members and face 
sheet, the shear, tension and compression moduli of the foam can be 
reliably utilized which in turn provides for an outstanding difference in 
the face loading necessary to produce a failure of the compression member. 
Thus, as compared with the arch beam disclosed in said patent, the present 
invention may sustain greater loads per weight of the compression member. 
It is an object of the present invention to provide a load support 
structure which will withstand greater loads while at the same time is 
structurally interrelated in a manner whereby it may be inexpensively 
constructed. 
It is another object of the present invention to provide a novel load 
support structure wherein a compression member, a tension member, and face 
sheet are joined to foam therebetween in a manner so as to utilize the 
shear, tension and compression modulus for resisting bending loads. 
Other objects will appear hereinafter.

Referring to the drawings in detail, wherein like numerals indicate like 
elements, for purposes of illustrating one environment for the present 
invention, there is illustrated a storage container in the form of an ice 
bin designated generally as 10. The ice bin 10 includes a housing 12 
having an access door 14 pivotably secured thereto. The housing 12 is 
mounted on legs 16. 
Referring to FIG. 2, there is illustrated the bottom wall 18 of the housing 
12. Wall 18 is supported by members 20 and 22 which are preferably tubular 
in section. Each of the members 20 and 22 is supported by a separate pair 
of the legs 16. The members 20, 22 may be positioned to support the wall 
18 at a location above or below the elevation of the bottom surface of the 
wall 18. 
A metal hanger strap 24 has its upper end welded to a top surface of the 
member 20. The hanger strap 24 extends downwardly to a horizontally 
disposed flange 26. A similar hanger strap 28 has its upper end welded to 
a top surface on member 22 and extends downwardly to a horizontally 
disposed flange 30. The flanges 26 and 30 extend toward one another. 
A tension member 32 which may be a flat or curved has upturned end portions 
34 and 36. See FIGS. 2 and 5. The wall 18 is defined at its lowermost 
surface by the member 32 and at its uppermost suface by a face sheet 38. 
Sheet 38 may be flat or sloped as shown in FIGS. 2 and 4. One elongated 
compression member or a plurality of discrete compression members 40 are 
disposed between the tension member 32 and the face sheet 38. See FIGS. 4 
and 5. Each of the compression members 40 has an upturned end portion 42 
at each end thereof. The space between adjacent compression members 40 is 
sufficient to allow circulation of a filler when injected into said space. 
A suitable dimension for such space is about one-half the width of the 
compression members 40. Such circulation space may be attained by holes in 
members 40. An elastic, low modulus insulation filler 44 such as foam 
urethane is foamed in situ to fill all internal space. 
In order to obtain a high strength bond between the foam plastic filler 44 
and surfaces in contact therewith, the bottom surface of face sheet 38, 
the opposite surfaces of the compression members 40 and the top surface of 
tension member 32 are suitably prepared. For example, the surface 
preparation may include chemical washing, zinc coating, sand blasting, 
special paints, adhesive coating, or the like. 
The end portions of the compression member 40 and tension member 32 are 
mechanically coupled together in a manner so as to minimize residual 
bending moments. Referring to FIG. 3, one inexpensive manner for joining 
the members 32, 40 is to provide bent end portions. Flange 30 is spot 
welded at point 46 to the tension member 32. Tension member 32 is tack 
welded to the compression member 40 at welds 48. The upper end portions 34 
and 36 are spot welded at their upper ends at 50 to the hangers 24 and 28 
respectively. Hangers 24 and 28 provide elastic hinges at 49 due to the 
right angled construction. 
As shown in FIG. 3, the portions of members 32 and 40 adjacent the weld 48 
have center lines which intersect at focal point 52. The center line of 
the hanger 28 also intersects focal point 52. Since the center lines 
intersect point 52, and force vectors coincide with center lines, there is 
a minimum of residual bending moments. While it is not necessary for the 
center lines to intersect exactly at focal point 52, a minor discrepancy 
is easily accomodated by the strength of the hanger 28. 
The compression members 40 may be arches as shown or may have other 
configurations appropriate to the loading pattern which results in an 
apex. The apex of the compression members 40 is preferably as near the 
face sheet 38 as manufacturing tolerances allow. In an operative 
embodiment of the present invention, zinc coated mild steel members 32 and 
40 had a thickness of 0.030 inch, zinc coated mild steel hangers 24, 28 
had a thickness of 0.060 inch, and chemically washed stainless steel face 
sheet 38 had a thickness of 0.024 inches. The span between the hangers 24, 
28 in the operative embodiment was 43 inches. The compression members 40 
had a width of 3 inches. The space between adjacent compression members 40 
was 1.5 inches. The filler 44 was urethane foam weighing three pounds per 
cubic foot. Members 40 are rectangular in section with a thickness of 
about 1/116 the distance between sheet 38 and member 32 when the rigidity 
of the filler 44 is 1/16,000 the rigidity of members 40. The maximum 
thickness of member 40 which would be applicable is about 1/16th the 
distance from face sheet 38 to tension member 32. This maximum thickness 
relates to the ratio of the rigidity of the filler 44 to the rigidity of 
member 40. The said maximum thickness is linearly proportional to the cube 
root of said ratio. These dimensions and materials may be varied as 
desired. 
While urethane foam is the preferred filler 44, other fillers may be used 
as foam plastic with reinforcing fibers of glass or carbon, wood chips in 
a binding matrix, metal particles in a binding matrix, solid polymeric 
plastics, etc. 
FIGS. 7 and 8 dramatically indicate the unique results of the present 
invention. In FIG. 7, there is plotted a graph of critical loading 
pressure calculated for the design illustrated in FIG. 6 for uniform face 
loading to produce elastic buckling per weight of compression member 
versus thickness of the compression member for the bonded foam filler 44 
of the present invention and for the same structure where the members are 
not bonded to the filler 44. As shown in FIG. 7, there is little 
difference in this example between the bonded and the non-bonded 
interfaces when the compression member has a thickness in excess of about 
1/4 inch. However, as the thickness of the compression member is reduced, 
the bonded interfaces of the present invention resists larger buckling 
loads on the order of a magnitude of 4 to 5 as compared with the 
non-bonded interfaces. 
FIG. 8 is a graph of stability margin (ratio of critical stress to yield 
stress) calculated for uniform face loading versus thickness of the 
compression member in inches. With bonded interfaces, all thickness have a 
stability margin greater than one. With non-bonded interfaces, only 
thickness above 1/8 inch have a stability margin greater than one. 
If the loading pattern in FIG. 6 were changed, the compression member would 
have bending stresses even with the smallest amount of load due to the 
arcuate contour, whereby the concept of elastic instability would not have 
significant meaning. If the loading were at a small zone at midspan, the 
bonded interfaces would reduce bending stress in the compression members 
40 by reducing bending motions. In a non-bonded system, the compression 
member would lose contact with the filler 44 over portions of the span. 
This lack of constraint would result in increased bending stress in the 
compression member. For equal stress in the compression members, the 
bonded interfaces of the present invention cause the load support 
structure to sustain greater face loads as compared to the non-bonded 
surfaces. This is very important since all real structures have bending 
stresses caused by manufacturing tolerances and off-design loading 
patterns. 
Though the above remarks concerning FIGS. 7 and 8 strictly apply only to 
the design example of FIG. 6, it will be understood that this example 
serves to illustrate the properties of a broad family of designs having 
widely varying dimensions and materials. This family is characterized by 
the rigidizing effects of bonding the filler 44 to all surfaces contacted 
as described above, and by the reduction in required bending stiffness of 
the compression member made possibly thereby. This family is also 
characterized by relatively small deflections of the loaded face sheet for 
structures of such cost and weight for the same reasons. FIGS. 7 and 8 
also illustrate that this family does not extend indefinitely, and is 
limited by designs having relatively great bending stiffness of the 
compression member in relation to the resistance to bending motions 
provided by the two elastic foundations. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential attributes thereof and, 
accordingly, reference should be made to the appended claims, rather than 
to the foregoing specification, as indicating the scope of the invention.