US2288193A - Structural member and building structure - Google Patents

Description

June 30, 1942. E A, HORN Er-AL 4 2,288,193

STRUCTURAL MEMBER AND BUILDING STRUCTURE Filed July 24, 1939 2 Sheets-Sheet 2 Patented June 3Q, 1942 UNITED STATES. PAT

ENTV ori-les STRUCTURAL DIEMBER AND BUILDING STRUCTURE Erwin A. nom, Irving r. Laucks, and P. nothin Attwell, Seattle, Wash., assignors, by mesne assignments, to I. F. Iaucks, Inc., Seattle, Wash.,

a corporation of Washington A i Application July 24, 1939, Serial No. 286,266

5 Claims. (Cl. 20-91) initial bending. We have now discovered that" these diilicultiesI can be avoided and a widely useful and stronger curved laminated beam-[can them to be especially advantageous in the construction of arched frame work forbuildings, two of the members, preferably, being utilized in the formation of each arch. We have found most effective from every point pfview, a frame work consisting essentially of two arches arranged in vertical planes as the diagonals of a'rectangle and secured to other arches arranged as the sides' of the rectangle, said other arches dening openings to wings leading'from the main enclosure f which is framed by the crossed arches. In this construction, a flooring may be provided across .the lower ends of the arches, and the latter -connected by tie rods located below the iiooring. The arches mayV be .directly sheathed, as by plywood panels, to provide a roof and side walls.

For uses such asherein contemplated, wood has the 'important advantages of a high ratio of strength to weight, relatively low cost, and ease of fabrication. However, for curved framing members which are required to carry heavy loads, the forests do not ,provide material having the necessary dimensions and properties, or atleast, material of the right character is not readil available. l 1

In making curved beams of this character,- such as are often required for roof supports and simibe built up at less cost by adopting a, different arrangement of laminae and method of \fabrica tion. b j

' In our method of fabrication we may eliminate bending offthe laminae entirely so that in our beam the edges of the laminaerather than their flat surfaces are opposed to ,the direction of the principal stress. This doesnot have .to be done in the shop but canbe done, ,if desired, on the job and thus save thecost of transporting heavy-1 and cumbersome shapes. We cut out the individual laminae in the fiat, usually with a band saw, and then assemble them with interposed adhesive in flat position using butt o r in some cases scarf joints at the end junctions of individual pieces where -a'plurality of pieces are present in a single laminae. 'The joints of.- ade' jacent laminae are staggered in such manner that these' joints cause a minimum of local weakness.

l lThe parts-are then assembled on any at s'up- 'porting surface with interposed glue which' is with glue of this character, they can in most cases be merely nailed together to hold them in proper relation while the glue is setting. It is',

lar uses, it has been heretofore necessary to use a laminated construction andto bendthe individual laminae to the proper curvature and then hold them together in the bent position with heavy clamps whilev the glue was setting. 'I'his involves undersirable initial stresses onA the parts and also necessitates shop construction and a costly equipment Aof heavy and often special clamps or formsl to' permit making up particular shapes. In the-case of large buildings, requiring longand -heavy beams, this prefabricated construction involves the troublesome feature of transporting along heavy shape from thev shop to the'job. 'There isalso the difiiculty that such` beams have a tendency to spring out of shape Wanddistortwhenethe clamping pressure is released or when moisture changes take place, since the wood laminae remains under stress due to the ,(f

.never necessary to of course, seen that this'methodis restricted to the fabrication of beams having curvature in only a single plane, but this restriction is of nx-` practical importance because it .is practically in more than one plane. .Q A

The material selected for the laminae is gen4 erally wood, although other available materials which can be adhesively united such as artificial l lumber, paper, plastics, etc.,may` also be 4used without departing from the principles of the in to embrace 'both natural wood'and also -such equivalents. When using wood, the elements may consist either of sewn lumber, thickyor thin structiomf We find that plywood is an especially useful material. -In general, it can be usedasif it were a single ply of the same total thickness. notwithstanding the presence of the middle cross ply. 1 g

use beams having curvature` In some instances,

stronger.

cause most of the pieces which are left over after cutting up a sheet or aboard can be matched together with similar pieces to form laminae or portions of laminae. f

While it is, of course, desirable to have theindividual plies as long as is permitted by the available material, nevertheless, unless the plies are comparatively thick, butt joints do not cause any serious local weakness provided the locations of the joints in the respective laminations are well staggered so as not to havetoo many butt joints come close to any given point in the beam. In some instances where the beams are being built up out of .laminations -of sawn lumber and a comparatively small number of laminations is used to make-up the thickness of the beam, it may be desirable to scarf and glue the ends of the pieces instead of using butt joints. Where the raw material is thin and the laminations numerous, this precaution is unnecessary. f

the principal section or core of our beams with laminae on edge, we may supply an additional however, while we make j the fiat side, the ultimate strength averaged 6150 pounds, but the average of duplicate tests with the loadl applied on edge was 8080 pounds.

AThe deflection under load was also much less at all loads when the beam Wasplaced on edge.

` This same difference in favor of on edge construction'was found to obtain with curved beams.

Thus our on edge vconstruction'is seen-to provide added strength in additionpto the other advantages.

In many instances owing-.to its general availability in large sheets, three ply Douglas iir plywood is a particularly suitable material for the construction of these curved beams. It would naturally be thoughtthat in this instance the presence of the middle ply having the grain outer reinforcing layer, stress covering, or tire consisting ofv additional laminae bent and adhesively united to a core or main construction made up with lamifiae placed on edge. The ad-4 vantagesof our simple method of building the core are' thus retained and there is the further important gain that the core can then act as its own form for gluing on the edge covering or `coverings at locations calling for increased section. This solves the problem of adding stress coverings to curved beams on the job because this can now be readilydone by providing a smooth surface on -the' edge of the beam requiring "reinforcement, .and then nailing or clamping on the ,covering with interposed adhesive. Reinforcing covering along any curved l portions of the beam are added as required and the surfaces held in contact by means of either nails or hand clamps-until the glue has set.

Thus no special forms are needed even when curved members are being fabricated. In both instances, that is, in the case of beams wholly made of laminae on edge ord-in cases requiring added "tires as stress coverings, we thus eliminate the necessity both for shop construction j and the use of elaborate` glue clamps.-

The use of stress coverings or tires in conjunction. with our. on edge" core construction is particularly advantageous in'building thick beams because special material to form an outer skin to .resist tension is then easily applied where required on a core of coarser or cheaper material, because by our method the core serves as a 'ready-made form.

. As regards strength, We have found that nif two beams are made up to the same section out of a multiplicity'of parallel glued laminations and one is tested as. a beam with the .bending force applied perpendicularly to the surface of the plies and the other with/the beam on edge,:

running in the short direction across the beam would reduce the strength at least one third. In practice, provided the cross grained ply is not -more than one-third of the total thickness, this does not appear to be the case. In fact, we find that a curved beam' made up out of a series of layers of plywood having the outer ply of each piece running lengthwise, when stressed on edge, is almost as strong as a bea of the same size made with all the plies `running lengthwise and also placed on edge. It seems probable that in this instance the middle ply of the `plywood serves to a considerable extent as a tie' to hold the tension bearing lengthwise fibers of the outerplies in proper position to more eifectively resist the load.

The advantage of using plywood in constructing beams of this sort is often important because of its cheapness, large size; ready availability, and the ease with which it can be band sawed to the proper contour for usein constructing of Figure 1.

the on edge" construction is considerably' curved beams, and in the latter case, is due in This is true either with straight or' y Figure 4 shows in perspective a curved structure element appearing in the preceding figures,

and

Figure 5 shows in perspective an end portion of -a structural element involving a laminated core and laminated edge coverings.

Referring to Figures 1'to 4,' reference numerals I lIii and Ii indicategenerally a pair `of arches arranged as the diagonals `of a square and composed, respectively, of identical half arch por- .tions I2I3 and Il, I5, portion I5 being shown alone in Figure 4. l I d This curved member or beam IE has an upright portion IB and a portion I1 upwardly` inclined l away from portion |6, the two portions being joined by a curvedsection i8. The member l5 is made up of a suitable number of laminae and ordinarily, and especially in the case of a memtwo outer plies having the grain running in the same direction, while the grain of the inner ply runs transversely. The pieces are cut so that the grain, or predominate grain, runs generally Alengthwise of the structural member.

at the curve may` be cut from a single piece to the full Width of the beam. Similarly, the end joints of the pieces of the underlying lamina are staggered, as at 30, so as to be lapped. In all cases, the joints whether lateral orend joints, are lapped so that no joints of adjacent laminae are in -registry. These joints are all ordinarily glued.

In the case of the beam' I5, its upper end is brought to a 90 point 3I, which mates withV able footings and the lower ends of the arches are connected by tie rods 32 and 33, Figures 1 .and 3.

Archesv 34, 35, 36 and`31, preferably formed of identical half arch portions made up as previ- .ously described, are arranged as the sides of the square .and their upright portions are bolted through Jthe upright portions of the main arches, as indicated, for example, at 38 and 39, Figure 2. 'I 'he half portions of arches 34 to 31 -are securely connected together in any suitable manner attheir upper ends, and their lower ends are connected by tie rods as at 40 and 4l, Figure 2,.so that a very rigid framework is provided.

Arches 34 to 31-may be utilized as defining openings to wings whose framework is completed by similar arches 42, 43 in faced parallel relation with respect to arch 34, arches 44 and'45 similarly disposed 'with respect to arch 35,' arches 46, 41 with-respect to arch 36, and arches 48, 49 with respect to arch 31. The lower ends of each of the arches are preferably connected by a tie rod. As here shown, the apices of all of the arches arel of the same height so as to providey four horizontal ridge lines. These lines may be carried -out by rafter assemblies 5B, 5|, 52 and 53, secured in rectangular relation. between the crossed arches I0 and I l, and providing a slope the same as the top slope of the wing arches. which slope is also carried out by the upper portions of ythe crossed arches. That is to say, the top edges of vbeing arranged inthe wings.

arches sa, 42 and as. or reiter assembly sa, and

of arch portions l2 and l5, for example, lie in the same two angularly related planes.

According to the most economical practice,- the arches are not connected by any permanent horizontal framing, but are merely temporarily braced, while sheathing, which may be in the form of plywood panels, is applied and secured in place.

As shown in Figure 3, sills, as at 54, may be provided, these supporting joists 55 on which is laid a floor 56 above the tie rods.

A structure asabove described may be very economically produced and provides a maximum amount of free interior space and has great strength. As one example, we have erected in' a northern climate, where heavy snow falls are encountered, a building in accordance with the present invention with crossed main arches, each with a spanof sixty-one feet, and wing arches with a spanof forty-three feet. In this case, the main enclosure dened by the cross arches was designed as an auditorium, tiers of benches The built up beams may be made of any desired size and i strength and for additional strength one or both of the edges of the on-edge laminae lmay be provided with anY adhesively applied bent stressed covering of one or more laminations. In Figure 5, a core portion is shown as made up of a multiplicity of laminae 51, which have staggered lateral and end joints and which are arranged parallel to the plane of the curve. Two laminae 5.8 and 59 are applied to the inside of the'beam and four laminae 60, 6I, 62 and 63 are applied to the outside of the beam. Superposed laminae have staggered lateral joints as at 64 and 65, and staggered end joints, as at 66 and 61.

From the above, it will be seen that the makeup of the curved structural members can be considerably varied, as can also their curvature, in

order to take -care of the situation in hand. Changes mayalso be made in the arrangement and relation of the arches in a building structure. Accordingly, we do not limit ourselves with respect to these matters except as in the followingclaims.

We claim: 1. A laminated structural member having curvature in a single plane and consisting of adhesively united -flat plywood laminae which are substantially parallel with 'the plane of curvature of the member, the laminae being each composed of a plurality of contiguous pieces iin longitudirunning transversely with respect to the grain oftheouterplies and the pieces being disposed with the grain of the outer plies running gener- -ally longitudinally of the member.

2. A. laminated adhesively bonded structural member having curvature ina singleplane, said memberincluding laminaecom'posed of a plurality of contiguous pieces in longitudinally extending relation substantially parallel with the plane of curvature of the member, said pieces each comprising outer plies with ,the grain running in the same direction and -an'inner` ply with the grain running transversely with respect to the grain of the outer plies and the pieces being disposed vwith the grain of the outer plies running generally longitudinally of the member,A

3. A structural member as set forth in claim 2.

covering of wood isadhesively applied t'o at least one edge of the member.

4. A laminated adhesively bonded structural member having a zone of relatively sharp curvature in a single plane, the laminae of said mem- 2,283,193 with the added feature that a benttraaie 1` ber in -said zone ofcurvature being composed of plywood pieces substantially parallel with the plane of curvature of the membensaid pieces :each comprising outer plies with the grain running in the same direction and an inner ply with the grain running transversely with respect to the grain of the outer plies, and the pieces being disposed with the grain of the outer plies running generally lengthwise of said zone.

5. A laminated adhesively bonded structural 4member comprising generally straight end por- .tions and a relatively sharply: curved portion vjoining said end portions, the laminae through-

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