US3471984A

US3471984A - Building panel structure

Info

Publication number: US3471984A
Application number: US611503A
Authority: US
Inventors: Robert E Hayes
Original assignee: STRESS PLUS Inc
Current assignee: STRESS PLUS Inc
Priority date: 1966-12-08
Filing date: 1966-12-08
Publication date: 1969-10-14
Anticipated expiration: 1986-10-14

Description

Oct. 14, 1969 R. E. HAYES BUILDING PANEL STRUCTURE Filed Dec. 8. 1966 2 Sheets-Sheet 1 INVENTOR.

5 HAY GS We ATTD 5Y5 fig-2a ZMRRWUMDMW Oct. 14, 1969 R. E. HAYES 3,471,984

BUILDING PANEL STRUCTURE Filed Dec. 8. 1966 2 Sheets-Sheet 2 Fig.3

48 3 INVENTOR.

17086797 5. HAVE-5 United States Patent 3,471,984 BUlLDlNG PANEL STRUCTURE Robert E. Hayes, Rome, Ga., assignor to Stress-Plus, Inc., Rome, Ga., a corporation of Georgia Continuation-impart of application Ser. No. 469,087, July 2, 1965. This application Dec. 8, 1966, Ser. No. 611,503

Int. Cl. E04b 2/56, 2/06; E04c 2/02 U.S. Cl. 52309 9 Claims ABSTRACT OF THE DISCLOSURE A prefabricated building panel structure of the sandwich-type having a filler core interposed between two skin elements and in which at least one shear block member is additionally secured between the skin elements at an intermediate transverse position to develop unusual strength in the panel structure without any need for or dependence on perimeter framing of any sort.

Cross-reference to related application This application is a continuation-in-part of my copending application Ser. No. 469,087, filed July 2, 1965, now abandoned.

Background of the invention The invention is concerned with prefabricated building panel structures of the sandwich-type that ditfer over the prior art by incorporating at least one transversely ar ranged shear block member positioned intermediate the panel ends and serving to invest the panel structure with exceptional strength, while being proportioned to remain clear of any side edge jointing means employed in or with the panel for installation purposes.

No comparable proposal has been found in the prior art, the state of which is believed to be fairly illustrated for present purposes by: Kloote, 2,199,938, May 7, 1940; Boyer, 2,376,653, May 22, 1945; Keller, 3,161,267, Dec. 15, 1964.

The Kloote disclosure is concerned with a panel structure in which the emphasis is on the integration of intermediate ribbing with perimeter framing, and in which the intermediate ribbing is closely spaced to provide aggregate strength from the ribbing, rather than attempting to develop the full strength potential of the skin elements with a minim-um of framing. Additionally, the panels contemplated by Kloote, which are intended for aircraft flooring, are notably of relatively limited size both as to thickness and as to length and breadth.

The Boyer disclosure describes a laminated board having a thickness in the order of A inch in which stiffening spacers may be used, but in which the spacers are apparently, as in Kloote, closely spaced when they are used. Also, Boyer describes his skin elements as sheets without any indication that they are intended to have significant strength of their own.

Finally, the Keller disclosure shows a building panel structure in which a stiifening core frame, that includes perimeter framing, is provided for fitting with skin elements at one or both faces. When skin elements are used at both faces, they are not connected other than through the framing, and the framing is purposely depended on for strength so that thinner, and consequently less expensive, skin elements may be used.

The present invention renders any special stiffener framing unnecessary and makes it possible instead to increase substantially the utility of conventional sandwich-type panels through the addition of at least one transversely arranged shear block member.

3,471,984 Patented Oct. 14, 1969 Summary of the invention Building panels of the sort dealt with by the present invention characteristically comprise a pair of skin elements having a filler core interposed in sandwich fashion. The filler core is employed essentially as a spacing means between the skin elements. The filler may be additionally selected for thermal insulation purposes, but the filler core materials commonly used are all of low density to maintain their cost within reason, and of consequently limited physical strength. All of these materials have sufficient compressive strength to serve their filling or spacing function when used properly, but none of them have any appreciable strength in tension or shear.

As a result, the skin elements must be depended on to provide the strength required in the panel structure, and the advantage at which the skin elements can be employed for this purpose determines not only the utility of the paenel structure but the reasonableness of its cost as well, for a favorable cost balance is promoted by maintaining the relatively expensive skin elements as thin as possible. As a general rule, a favorable cost balance cannot be obtained unless the skin elements represent no more than about 10% to 25% of the mass or volume of the panel structure.

These considerations have heretofore severely limited the uses to which prefabricated building panels might be put. For example, exterior wall panels are commonly subject to design specifications requiring a degree of stifiness for withstanding wind loading that could not be met by the sandwich-type panel structures previously available. The same thing is true with respect to the load capability normally specified for roof panels.

The present invention makes it possible to comply with such design specifications readily by additionally including at least one shear block member secured between the skin elements at an intermediate, transverse position with respect to the span closing dimension of the panel structure; that is, the panel structure dimension which is proportioned for installation across the span at which deflection loading must be borne. The transversely positioned shear block member is interposed between the skin elements together with the filler core, and Whether more than one shear block member is used depends on the extent of span to be closed and the degree of deflection loading to be borne. If the span to be closed exceeds 8 feet, or if the panel structure is required to withstand deflection loading of 30 pounds per square foot or more, there should be more than one shear block member provided. The number of shear block members to be provided is determined by the aggregate shear block width required to prevent slipping of the skin elements with respect thereto under the forces resulting from deflection loading normal to the exterior face of either of the skin elements, while limiting the individual shear block width to about three-fifths of the shear block depth. The shear block depth, of course, corresponds with the filler core depth, and is determined by the size of panel section needed for the purpose at hand.

It has already been noted that at least one shear block member is always used. As many as five might be employed advantageously in exceptionally large panels, but no more than three are needed under usual circumstances. When only one shear block member is used, it should be located transversely at the longitudinal center of the panel. Absolute centering is not essential, for a lessened but still material strengthening is obtained at locations considerably off-center, but the best advantage results when a practical centering of the shear block member is maintained. If the length of the panel structure indicates that more than one shear block member is needed, two such members equally spaced lengthwise of the panel may be used, as

in the illustrated embodiment that is described further below, when the panel structure involved has a margin of ultimate strength so that resistance to deflection is the determining design factor. That is, when the object is simply to make certain that maximum deflection will remain below a certain limit under a specified loading. On the other hand, when maximum ultimate strength is needed or desired in a given panel structure, a centrally located shear block member should be used with supplementing additional shear block members spaced to each side as needed for maintaining deflection strength Within specified or acceptable limits when the length of the panel of the expected loading requires such supplementing. In such a case, the additional shear block members are equally or symmetrically spaced to each side of the central one so as to have a related transverse location at which they serve to supplement the strengthening action of the central member as determined by stress analysis of the particular panel structure at hand. The symmetrical spacing of the additional shear block members to each side of the central one will always be substantial, but it will vary from one panel design to another, and it will not necessarily coincide with the midpoint between the central member and the panel ends. A practical guide for location of the additional shear block members under usual design conditions is given by the formula:

where X is the spacing from the longitudinal center of the panel at which the additional members should be located, S is the thickness of one skin element, A is half the panel length, and B is the aggregate thickness of the core and one skin element; all in inches. Thus, in 4 x 8' panels employing a 2" core, the X spacing should be about 28" with Ms" skin elements; about 34" with 7 skin elements; and about 38% with A" skin elements. Such spacing is not precisely critical, but the formula indication points to the best results and there is advantage in following it, when the indicated X dimension is within onehalf of panel length.

The shear block members are suitably formed of wood and are proportioned in cross-section so that their width is neither less than the previously noted three-fifths relation to depth nor greatly in excess of this relation. A crosssection of 2 /2" x 1%" has been used to good advantage in panel structures formed of A" skin elements on a 2 /2 filler core. The shear block members are proportioned in length so that they extend transversely for at least 75 percent of the transverse panel structure dimension but terminate short of the skin element side edges and also short of any panel jointing means disposed thereat, and they are secured between the skin elements by an adhesive developing a bond at the inner skin element faces of greater strength than the skin elements or the shear block member.

As will appear more fully below, exterior wall panels of the foregoing section dimensions have been successfully prepared according to the present invention to comply with a design specification for withstanding a uniform wind load of 45 p.s.f. with a deflection limited to the span divided by 240, which is considerably beyond the capability of prefabricated sandwich-type panels otherwise available. It is not understood exactly why the use of shear block members in the manner indicated above produces the marked increase in panel strength that has been observed. It appears possible that the shear block members cause the skin elements to act as a composite beam and thereby develop the full strength of the skin element that is tensioned by the deflection loading imposed. This possibility is suggested by the fact that under deflection test loading to destruction the tensioned skin element of panel structures embodying the present invention has been observed to fail ultimately in tension, without any evidence of appreciable bending strain. In any event, the marked increase in strength has been confirmed in actual use.

The panel structure arrangement of the present invention may be readily arranged for jointing in a variety of ways upon installation, and the present invention also provides for facing such panels to unique advantage, as is noted further below in describing the invention at greater length in connection with the accompanying drawing.

Brief description of the drawing FIG. 1 is a section of an installed panel structure embodying the invention;

FIG. 2 is an elevation as seen from the right in FIG. 1;

FIG. 2a is a fragmentary side elevation of an alternative form of panel structure in which shear blocking is employed centrally and supplementally to each side;

FIG. 3 is an enlarged fragmentary section showing the head installation details substantially at the line 33 in FIG. 2;

FIG. 4 is a further fragmentary section, illustrating a suitabe side edge jointing arrangement for the panels, as taken substantially at the line 44 in FIG. 1; and

FIG. 5 is a final fragmentary section showing the foot installation details substantially at the line 55 in FIG. 2.

Description of the preferred embodiments Referring now in detail to the drawing, and more particularly at first to FIG. 1, the reference numeral 10 indicates generally the disposition of a representative panel structure embodying the present invention installed as an exterior wall member closing the span between a floor slab 12 and a deck structure 14, with a ceiling means 16 supporting insulation 18 hung below the deck structure 14 and the panel structure 10 being arranged with a sufiicient upward extent for fitting with a super-structure at 20 to form a balcony railing in relation to the upper surface of the deck structure 14.

For an installation such as is illustrated in FIG. 1, the panel structure 10 needs to be about 12 in length (not including the superstructure 20), and as the skin element materials are commonly available in a commercially standard 4 running width the resulting unit size of panels 10 is 4' x 12', with the direction of greater tensile strength inherently extending with the span closing length. Comparing FIGS. 1 and 2, these panel units 10 are seen to comprise outer and

inner skin elements

22 and 24 assembled on an interposed filler core (indicated fragmentarily in FIG. 1 at 26) together with the previously mentioned shear block members arranged, as at 28 in FIGS. 1 and 2, intermediately and transversely of the length.

The

skin elements

22 and 24 are suitably, and even preferably in this instance, formed of steam cured asbestos-cement sheets. Uncured sheet material of this sort is commercially available as Johns-Manville Flexboard" to meet Federal Specification SS-B-755, Type F; and ASTM Specification C220-61 Type F. Steam curing of this sheet material improves its physical strength appreciably and adapts it for use to excellent advantage according to the present invention. For the illustrated exterior wall use, the steam cured asbestos-cement sheets are provided in Mt thickness, while /8 thickness would be sufficient for interior wall use. The

A skin elements

22 and 24 are assembled on a 2 /2" filler core 26 to form a composite panel thickness of 3", and extruded bead expanded cellular polystyrene is employed as the core material to afford adequate exterior wall thermal insulation. A core of this sort is capable of providing an air to air (U) value of .095, and has the further advantage of a suitably low flame spread rating (i.e., not more than 25 based on ASTM Specification E84-61).

The shear block members 28 are conveniently and suitably formed of wood and are used in the illustrated panel 10 at the previously mentioned cross-section dimensions of 2 /2" x 1%", with two such members being used in view of the relatively long span to be closed between the floor slab 12 and deck structure 14, as well as the relatively high deflection loading to be borne. It is not necessary that wood be used for the shear blocking, for any other material of comparable physical strength would serve as well, but wood will usually have the cost advantage for this purpose and will usually be the easiest to handle. In using wood for the shear blocking, it should be pressure treated for flame-proofing.

The panel unit assembly is secured with adhesive, the entire inner faces of the

skin elements

22 and 24 being coated with adhesive for bonding to the filler core 26 as well as the shear blocking 28. The adhesive used should be highly Water and mould resistant and capable of meeting all commercial standards for Type 2 glue lines and, in particular, Federal Specification MMM-A-l25. A resorcinol adhesive has been found suitable.

Assembly of the illustrated panel unit 10 also includes securing one side edge jointing block 30 in place (compare FIGS. 2 and 4), as well as an upper anchor bolt block 32 and leg portion 34 of the superstructure together with a stringer 36 reaching therebetween (compare FIGS. 2 and 3). It will be noted that the shear blocking 28 extends transversely short of the jointing block 30 and of the opposite panel side so as to remain clear as the panels 10 are jointed during installation (see FIG. 4).

FIG. 2a illustrates an alternative panel unit assembly of the previously noted 4 x 8' size in which transverse shear blocking 28' is installed at the longitudinal center of the panel structure and at two supplementing locations spaced substantially and equally toward the panel ends at each side. As in the FIG. 2 embodiment, a side edge jointing block 30' is secured between the skin elements (only the outer of which, 22, is shown), while the shear blocking 28 terminates short of the jointing block 30 in each instance, and the panel structure is completed by interposed filler core material as indicated at 26'.

FIGS. 3 and 4 indicate the ease with which the panel units 10 can be erected and fixed in place. FIG. 5 shows the floor slab 12 fitted by means of anchor studs, as at 38, with a perimeter framing block 40 over which the lower open edge of the panel unit 10 is simply set in place without needing any fastening thereat whatever. The only fastening employed is at the previously mentioned anchor bolt block 32 at which an anchor bolt 42 is employed for connection with an attaching plate 44 anchored in turn, as shown, in the deck structure 14.

As each panel unit 10 is erected in this manner, it is jointed with the previously erected one by nesting its side edge jointing block 30 within the open side edge of the adjacent panel, or vice versa, to form a side edge joint as illustrated in FIG. 4. If the resulting joint must be made waterproof in the course of formation, a suitable adhesive is used in securing the joint. Otherwise, the simplest procedure is simply to fasten the joint preliminarily with nails as indicated at 46.

Panel units 10 embodying the present invention have been prepared and arranged in the foregoing manner for exterior wall use to meet the previously noted design requirements of withstanding a uniform wind load of 45 p.s.f, with deflection limited to the span divided by 240, and additionally providing a safety factor of three to one at design load, while also affording an exceedingly attractive cost balance both from the standpoint of first cost and erection handling.

The panel arrangement illustrated has also been uniquely provided, according to the present invention, with a decorative aggregate facing as indicated at 48 in FIGS. 3, 4 and 5. The facing used in this instance was formed with a size #2 quartz aggregate; although the same thing might be done with a marble aggregate, a variety of gravels, or any other material of this sort. Application of the aggregate 48 is accomplished with an epoxy adhesive matrix having a thickness of about /8" to and most of the application is done during prefabrication of the panel units 10 with a self-leveling formulation suitably comprising (by volume):

Parts Epoxy resin (H.B. Fuller #7377) 13 Catalyst for the epoxy resin l #4 silica sand l3 #8 marble dust 4 After suitable catalyst activation and blending of the silica sand and marble dust extenders, the epoxy matrix may be applied with a hand trowel or any other convenient spreading means. Once the matrix is in place, aggregate facing is simply sprinkled thereon at a proper facing distribution and then tamped to a secure seating in the matrix with a rubber-faced float or the like. During such facing of the panels 10 in the course of prefabrication, side edge portions of the treated panel surface are left clear for joint covering, in a width of the order indicated at 48 in FIG. 4, after the panels 10 have been erected. For the joint covering aggregate application after erection, the epoxy matrix formulation should be modified sufiiciently to stand properly on a vertical surface, An epoxy resin of the type of HE. Fuller #167 is suitable for such modification.

Use of the epoxy matrix for application of the aggregate facing 48 provides the unusual result, when the

skin elements

22 and 24 are asbestos-cement sheet, of leaving the balance of the panel structure undisturbed despite addition of the facing 48 at the exterior surface thereof. That is, the

respective skin elements

22 and 24 are allowed to function normally as the paired surface components that give the panel unit 10 its structure strength without hindrance from the facing 48. Such a result is not usually possible because a facing addition commonly tends to modify substantially the response of a skin element on which it is applied to the physical conditions that the skin element must bear. For example, a facing addition will ordinarily impose a buckling tendency on a skin element during thermal expansion or contraction, and it may change materially the flexibility or stiffness of the skin element, so that the structural action of the faced skin element is no longer paired with its partner.

An epoxy matrix obviates any such difliculty, apparently by such physical compatibility with asbestos-cement sheet as to allow such sheet to function as a skin element substantially as if it were not faced and thereby preserve the structural balance of the panel unit. The epoxy matrix also affords the characteristic adhesive strength of such materials for durable application of the aggregate facing 48, and additionally serves effectively for waterproofing the panel joints upon joint covering application at 48.

FIG. 3 further indicates the manner in which the aggregate facing 48 may be carried over the upper exposed end portion of the pnaels 10 with additional abbreviated asbestos-

cement pieces

24 and 24" laminated on the inner skin element 24 to provide a sheltering cavity in which a sealing cover 50 for the deck structure '14 may be terminated. It should also be noticed in FIG. 5 that the lower edge of the outer skin element 22 may suitably be extended slightly to provide for sheltered caulking as at 52 in relation to the floor slab 12.

Finally, it should be mentioned that panel structures embodying the present invention may be formed with a great variety of materials other than those that have been specifically noted. For example, when roof panels are to be formed, it will usually be desirable to use plywood skin elements. Other exemplary skin element materials that may be used are gypsum board, gypsum form board, laminated paperboard (vinyl coated, if desired), and the like. A wide choice of other core materials is likewise available, such as expanded bead polystyrene, urethane foam, and paper honeycomb materials.

The present invention has been described in detail above for purposes of illustration only and is not intended to be 7 limited by this description or otherwise except as defined in the appended claims.

Iclaim:

1. In a structure having members defining a structural span at which deflection loading must be borne by closing means thereat, the combination with said members of: an improved panel structure for closing said span which consists essentially of a pair of skin elements; and a filler core interposed between said skin elements together with at least one shear block member; all such shear block members being secured against slippage to the respective inner faces of said skin elements at an intermediate, transverse position With respect to the span closing dimension of said panel structure that is related to the midpoint of said dimension, extending transversely and continuously for at least 75 percent of the transverse dimension of said panel structure but terminating short of the skin element side edges and of any panel jointing means thereat, and having in sum the physical strength to withstand the shear stresses generated parallel to said skin elements and perpendicular to the longitudinal axis of said shear block members by the deflection loading that must be home at said span.

2. The combination as defined in claim 1 and further characterized in that all such shear block members have a depth corresponding to the depth of said filler core and a width not less than and not greatly exceeding three-fifths of said depth.

3. The combination as defined in claim 1 and further characterized in that all such shear block members are adhesively secured to the respective inner faces of said skin elements, and the number of shear block members provided is determined by the aggregate shear block width required to prevent slipping of the skin elements with respect thereto under the stresses resulting from deflection loading normal to the exterior face of either of said skin elements.

4. The combination as defined in claim 3 and further characterized in that the transverse positioning of all shear block members provided is equally spaced intermediatelly of said span closing dimension.

5. The combination as defined in claim 3 and further characterized in that three shear block members are provided with one transversely located at the longitudinal center of the panel structure and the other two spaced substantially and equally to each side of said longitudinal center at supplementing transverse locations.

6. The combination as defined in claim 1 and further characterized in that said skin elements are formed of steam cured asbestos-cement sheets.

7. The combination as defined in claim 1 and further charzgterized in that said filler core is formed of expanded cellular polystyrene.

8. The combination as defined in claim 1 and further characterized in that all such shear block members are formed of wood.

9. The combination as defined in claim 1 and further characterized in that the exterior face of at least one of said skin elements has an aggregate facing applied thereto with an epoxy matrix.

References Cited UNITED STATES PATENTS 2,376,653 5/1945 Boyer 52-309 X 3,363,378 1/1968 Palfey 52-615 2,660,766 12/1953 Petterson 52-615 2,725,604 12/1955 Loetscher 52-615 2,791,809 5/1957 Lincoln 52-615 X 2,858,580 11/1958 Thompson 52-309 X 2,872,710 2/1959 Cox 52-615 X 3,226,902 1/1966 Elmendorf 52-615 FOREIGN PATENTS 25,221 1952 Finland. 680,240 1964 Canada. 236,934 1961 Australia.

OTHER REFERENCES House & Home, vol. XVII, No. 1, January 1960, p. 156.

Architectural Record, vol. 133, No. 5, May 1963, p. 325.

American Builder, October 1950, p. 60.

JOHN E. MURTAGH, Primary Examiner U.S. Cl. X.R.