US 3170198 A
Description (OCR text may contain errors)
Feb. 23, 1965 E. 1. SNIDER WOODEN I-BEAM Filed June 22, 1960 m R Z: i 1. MI N 8 mm 6m 6w 8 w 5 @M United States Patent WOODEN I-BEAM Eliot I. Snider, 80 Dorset Road, Newton, Mass.
Filed June 22, 1960, Ser. No. 37,883
3 Claims. (Cl. 20-.5)
' This invention relates to'wooden structural members and more particularly to a Wooden Lbeam of novel and improved construction. g v
" This invention is concerned primarily with' structural 'load carryingbeams such as arefused in the construction of free spans on the order of 3-0 to IOO'feet. Steel beams 7 be substituted for a steel I-bcam and which will provide a load carrying capacity equivalent to the steel beam while at the same time will not substantially increase the overall height of the structure.
It is a further objectv of this invention to provide a wooden I-bearn of novel and improved construction which will have a strength heretofore unobtainable with wooden beam construction of corresponding size, which is adapted to be prefabricated to provide increased economy of construction and which is pleasing in appearance.
Other objects will be in part obvious, and in part pointed out more in detail hereinafter. J
The invention accordingly consists in the features of construction, combination of elementsv and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.
In the drawing:
FIG. 1 is a side elevational view of a wooden I-beam constructed in accordance with the present invention;
FIG. 2 is anenlarged cross sectional along the line 22 of FIG. 1; I V 7 FIG. 3 is a top plan view of the beam of FIG. '1; and
PEG. 4 is a side elevational Vl6W -Qf theweb of'the I-beam of FIG. 1. 1'
A Wooden beam constructed in accordance with the present invention comprises a pair of flanges'lt) and 12 extending in spaced apart, parallel relationship along the opposite longitudinal edges of an elongated plywood web 14. The flanges and web are rigidly connected by an adhesive, such as casein glue, bonding all contacting.
surfaces of the flanges and web. The beam further comprises a plurality of timbers designated at 16, 18, 2th and" 22. The term timber as used herein defines a Wooden member of a size consistent with the member being 'a.
structural load carrying part; of the beam. i In practice the timbers are preferably of stock sizes such as' commonly referred to as 2 X 3, 2x 4, 2 x 6, etc., the particular size of the timber being dictated by the load to be carried by the beam. It should be emphasized here that the timbers are not merely stiffening membersfor the plywood web butthat they are structural load carrying parts of the beam. The timbers are rigidly connected to the web by a suitable adhesive bond, such as provided by a casein glue, between'all surfaces of the timbers contacting the iew substantially 14 and extending longtiudinally along the longitudinal edge portions of the web. The next adjacent wood members 24 in each of the flanges are adhesively bonded along their contacting surfaces, and as shown in FIG. 2, the longitudinal edge portions of the web 14 are engaged between the members 24 on the opposite sides thereof forming each flange. The flange members 24 next adjacent to. the web are adhesively bonded thereto along the contactingsurfaces thereof. The longtiudinal edges of the web 14am preferable recessed within the flanges 10 and 12 in order to protectthe edge of the plywood. i
In the specific embodiment shown, each flange member 24 is fabricated of a "plurality of; timbers 24a, 24b and 24a. The flange members 24 are preferably fabricated from a plurality of timbers inorder to increase the econonly of'construction'by utilizing commonly stocked lengths of lumber. For example, in a beam of approximately 40 foot length inthe lower most flange member 24, as viewed in FIG. 3 of the drawing, the member 24a may be a 2 x 6 twelve feet long, the member 24b a 2 x 6 fourteen feet long, and the member 24c a 2x 6 eighteen feet long. The members 2411, 2412 and 240 are joined by scarf joints with an adhesive bond at the joints. It is preferred'that the joints be staggered longitudinally and laterally across the flange. Accordingly, the next adjacentflange member 24 may be fabricated from three 2 x 6s fourteemfourteen and sixteen feet long corresponding respectively to the sections 24a, 24b and 240 previously described. The portion of the flange on the opposite side of the web is'sirnilarly constructed but in reverse orientation In the construction of the flanges, the dimensions and number of timbers making up each flange may be varied both to varythe depth and Width of the flange in order to provide the beam with the rigidity to resist vertical bending and with the stability relative to lateral deflection which is necessary for the purpose for which the beam is intended. By means of this construction a rigid strong flange is provided while at the same time economy of constructionis maintained through the use of commonly stocked sizes of lumber. I
' As clearly apparent from FIG. 1, theitimbers 16 extend diagonally of the longitudinal, axis of the web, and as shown in FIG. 2, are disposed on opposite sides of the web. The timbers are engaged between the flanges in supporting relation, and in the specific embodiment shown, the ends of the timbers are mitred. Further, as will be apparent from FIG. 1, the next adjacent diagonal timbers 16 are inclined in opposite directions andare spaced along the beam to connect the flanges in a manner forming a strong structural support therebetween. In the preferred embodiment, the diagonal timbers 16 adjacent the ends of the beam are spaced closer together than. are the diagonal timbers 16 nearer the longitudinal midpoint ofthe beam as defined by the verticaltimber 20 extending at right angles between. the flanges. In this manner greater strength is provided in the portions of the beam where it is necessary. Also the vertical timbers 18 at the ends of the beam and the vertical timbers 22 disposed centrally of the end pair of diagonal timbers 16 contribute to an increase in strength of the-beam adjacent itsends. 'As will be apparent to those skilled in the art, the spacingof the diagonal timbers may be varied as desired and necessary.
In a beam constructed in accordance with this invention, the combination of the diagonal timbers, plywood web and wooden flanges, with the timbers and. weband with the web and flanges, adhesively bonded along their contacting surfaces, provides a bearnj-having a strength which-is greater than that obtained in a similar construc tion in which a plywood web and similarly arranged timbers act separately but at the same time;
The strength of the beam andparticularly its resistance to bending is, in the preferred embodiment, further improved by orienting the grain of the plywood web so that the grain extends diagonally of the longitudinal axis of the web. As shown by the arrows in FIGS. 1 and 4, it is preferred that the grain of corresponding plys. at one side of the longitudinal midpoint of the beam be inclined opposite to the grain of the corresponding plys at the other side of the longitudinal midpoint of the beam. The inclining of the grain of the plys of the plywood web may be achieved by cutting plywood sheets to a configuration whereby when the web is assembled with the flanges the grain of the face layers of the plywood will extend diagonally of the web. As the grain of each ply in a plywood sheet is normally at right angles to the grain of a next adjacent ply, it will be apparent that the grain of all the plys will extend diagonally of the web. Further, as shown in FIGS. 1 and 4, in the preferred embodiment, the web is formed from a plurality of sections 26 arranged in end-to-end alignment and engagement to provide a plurality of next adjacent pairs of web sections. In the specific embodiment shown, the two portions of the web on the opposite sides of the longitudinal midpoint of the web are similarly constructed although these portions are arranged in reverse orientation. Each of these portions of the web comprises a trapezoidal section 26a at one end as an end section or panel of the web followed by a plurality of sections 26b having the shape of parallelograms and finally a second trapezoidal section 26c in reversed orientation relative to the end section 260. Thus substantially all of the next adjacent pairs of web sections have next adjacent ends extending diagonally of the web. As will be apparent from the arrows in FIGS. 1 and 4, the face grain on each web section preferably extends approximately 45 to the longitudinal axis of the web.
In a specific embodiment of a beam approximately 40 feet long, it was possible to provide an end web section 26a and next adjacent web section 26b from a single 4 x 8 sheet of plywood. This, of course, provides increased economy of construction inasmuch as the plywood which is preferably of exterior grade and good quality is the most expensive material of the beam. It is realizcd that in providing a plurality of web sections from a single sheet of plywood it may not always be possible to obtain web sections in which the grain of the plys will extend at 45 degrees to the web axis. However, to the extent possible, the grain of the plys should be oriented at angles diagonally of the web axis as to improve the beam shear strength.
In the preferred embodiment shown, each of the joints between next adjacent ends of the web sections is covered by a pair of timbers adhesively bonded to the web sections on opposite sides respectively of the web. For example, each of the diagonal joints between next adjacent web sections is covered by a pair of diagonal timbers 16 while the squared joint between the two center web sections is covered on both sides of the web by a pair of vertical timbers 20 adhesively bonded thereto. In the construction'of a beam of this invention it is preferred that an adhesive, such as casein glue, which does not require heating, be used throughout in order to facilitate ad provide economy of construction. In the gluing up of the beams suitable pressure must be applied to the joints for a suificient period in order to obtain uniform rigid bonds at the joints. All lumber should, of course, be of good grade and relatively free from defects which would inany way reduce its gluing properties.
Thus, it can be seen that there has been provided a wooden structural beam of novel and improved construction which may be used in place of steel beams to provide a correspondingly strong load supporting structure while at the same time not undesirably increasing the overall height of the construction. The overall depth of a beam constructed in accordance with this invention is approximately one-half of thatwhich would normally be expected from conventional wood engineering, while,
on the other hand, it will provide a rigidity approximately two times that which would normally be expected. It has been found, for example, that over the long spans contemplated by this invention a wooden I-beam constructed in accordance with thisinvention is fully satisfactory to hold a plastered ceiling without cracking of the ceiling whereas conventional wood construction would be in question for even maintaining the ceiling. Thus, it is apparent that rigidity against deflection under load, which is the normal limiting factor in wood construction, is one of the distinguishing features of a beam constructed in accordance with this invention. Further, a beam constructed in accordance with this invention may be. fabricated at a cost substantially less than that of wooden beams of conventional construction and comparable strength and, of course, at a very substantially less expense than a steel I-beam of corresponding strength.
Inasmuch as many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the language in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
1. A structural truss comprising an elongated web member of sheet plywood, said web member comprising a plurality of sheets with abutting edges and lying in the same plane, each sheet having alternate layers in mutually perpendicular arrangement, the layers of said sheets having their grains extending diagonally of the principal dimension of the web member, flange members extending at right angles to the web member from its lateral edges, each of said flange members consisting of a plurality of elongated structural wood members of uniform cross section adhesively bonded together and to the web in stacked relation, and a plurality of relatively stiff struc-- tural truss timbers of uniform cross section each extending diagonally of the principal dimension of the web member substantially its full width between the flange members and overlying the abutting edges of the sheets forming the web, said truss members being bonded to the web member throughout the mutually contacting surfaces thereof and varying in mutual spacing with distance from the ends of the web to provide stiffness against lateral bending of the web and the beam.
2. A structural truss comprising an elongated web member of sheet plywood, said web member comprising a plurality of sheets with abutting edges, each sheet having alternate layers in mutually perpendicular arrangement, the layers of said sheets having their grains extending diagonally of the principal dimension of the web member, four flange members extending at right angles to the web member from its lateral edges to form an I-section therewith, each of said flange members consisting of a plurality of elongated structural wood members of uniform cross section adhesively bonded together and to the web in stacked relation, and a plurality of relatively stiff structural truss timbers of uniform cross section each extending diagonally of the principal dimension of the web member substantially its full width between the flange members and overlying the abutting edges of the sheets forming the web, said truss members being bonded to the web member throughout the mutually contacting surfaces thereof and varying in mutual spacing with distance from the ends of the web to provide stiffness against lateral bending of the beam.
3. A wooden structural beam comprising an elongated plywood web divided longitudinally in a plurality of sections abutting along diagonal joints, a pair of wooden flanges extending in parallel along the opposite longitudinal edge portions of the web, said flanges being rigidly Y adhesively bonded to the web along the contacting surfaces therebetween, and a plurality of 'wooden timbers extending diagonally of the web and covering said diagonal joints with next adjacent diagonally extending timbers on the same side of the web being inclined in opposite directions, said timbers varying intheir mutual spacing with distance from the ends of the web, being adhesively bonded to the web and being engaged between said flanges, the grain of the-plies of each section of the web extending in substantially the same direction as the covering timbers.
v References Cited bythe Examiner UNITED STATES PATENTS 2,118,048 5/38' Landsem Q. 20-91 5/21" Knight 20-65 1/22 Turner 20 WILLIAM I. MUSHAKE, Examiner.
. V 6 2,230,628 2/41 Sahlberg 20 0.5 2,252,956 8/41 Adler 20-0.5 X 2,382,201 8/45 Burke 200.5' 2,886,857 5/59 Brosenius 20-05 FOREIGN PATENTS 984,7 92 2/51 France. 1,119,188 4/56 France.
903,373 2/54 Germany.
58,440 9/46 Netherlands. 73,087 2/ 48 Norway.
324,576 1l/57 Switzerland.
OTHER REFERENCES Plywood-what it is-'-what is does, by Book Co. Inc., pp. 36 and 37.
V Harbor Plywood Corp., Detailed Super-harbord Construction Applications, publication, pageflO.
JACOB L. NACKENOFF, Primary Examiner.