US2886857A - Wooden beam constructions - Google Patents

Description

May 19 1959 K. H. BRosENlus 2,886,857

WOODEN BEAM ooNsTRucToNs Filed Dec. 14, 1953 '7 Sheets-Sheet 1 FQ- 1 i w Fig. 2

\f 759/ A( Y X\ 3 Fig. 3

INVENTOR Karl Milling Braseums B May 19, 1959 K. H. BRosENlus 2,886,857

` WOODEN BEAM coNsTRucToNs Filed Dec. 14, 1955 rz sheets-sheet 2 fr/vEA/Tan Karl Hila x3 Brusema s By/IJWMAI ATToRA/Y May l19, 1959 K. H. BRosENlus 2,886,857

Y WOODEN BEAM CONSTRUCTIONS Filed Dec. 14. 1953 `'7 Sheets-Sheet 3 s fm m A "\2& w y gf XYYWw,

INVENTO Karl Hildn grose'nius ATTORNY K. H. BROSENIUS WOODEN BEAM CONSTRUCTIONS May 19, 1959 '7 Sheets-Sheds 4 Filed Dec .I 14,` 1953 Fig. 17

INVENTOR Karl Hlalw Broscmvus By M May 19, 1959 K. H. BRosl-:Nlus 2,886,857

WOODEN BEAM coNsTRUcTroNs Filed Dec. 14, 1955 fr sheets-sheet 5 Fig. 2O

INVENTDF? Karl H (ldv Brosev v5 By ATTom/v MayV 19, 1959 K. H: BRosENlUs 2,886,857

" WOODEN BEAM coNsTRUcToNs Filed Dec. 14, 1953 7 Sheets-Sheet 6 K. H. BRosENlUs 2,886,857

WOODEN BEAM coNsTRucTloNs '7 Sheets-Sheet 7 "May 19, 1959 Filed Dec. 14, 1955 Iwan-ron 'Karl Hhln Bruszmur 5%,

` ATToRNEY altem:

2,886,857 Patented May i9, 1959 hice WOODEN BEAM CONSTRUCTIONS Karl Hilding Brosenins, Stockholm, Sweden, assigner to Hyresgasternas Sparkasse-och Byggnadsforeningars gikscorbund, Stockholm, Sweden, an association of we en Application December 14, 1953, Serial No. 398,150

4 Claims. (Cl.'20.5)

This invention relates to certain constructions of wooden beams which consist of a web of boards crossing each other diagonally and wooden flange laths or strips or frame-bars attached at theedges of this web by nailing.

According to a well-known construction said flange laths consist of ordinary solid timber which is normally to be had on the market in relatively restricted lengths. When using ordinary nails with relatively close nailing, which is often necessary for heavily loaded beams of the type now referred to, there is often the risk of splitting being caused in the rows of nails in the above-mentioned laths, resulting in a considerable reduction of the strength of the beam. This risk is particularly incurred since `in Abeams of greater length the flangelaths must be lengthened by `joining further pieces of lath by means of nailing while using joint-pieces externally of the joint. In this case particularly close nailing and consequently long, and, as a rule also heavy nails or spikes are required.

The main object of the present invention is to eliminate the said drawback by providing means for making large and strong beams in a most simple manner, while at the same time avoiding overlapping unattractive joints for the ange-laths. The invention relates to the type of beams in which each flange is composed of two or more layers of boards (for example of about 1" thickness), which are glued together along vertical planes and in which `these anges are arranged in pairs on both sides of `a web cornposed of at least two layers of boards crossing each other diagonally. According to one feature of the invention the flanges are attached to this web by means of wirenails, the diameter or edgeside of which is small in relation to the length of the nails as compared with nails now in use for corresponding purpose. Preferably, the thickness of the nails does not exceed about Hgo or in extreme cases 1/5 of the length of the nails. The maximum diameter of the nail is for instance 0.25 to 0.30.

The boards in each layer of boards of the llanges are jointed longitudinally by means of glued oblique joints, hook joints, nger joints or such like. These joints are so arranged in the longitudinal direction of the anges in relation to the joints in adjoining layers of boards that all joints in a flange will be distributed with approximate uniformity in the longitudinal direction of the flange. Also the nails by means of which the flanges are attached to the web of the beam are distributed substantially `uni- 'formly inthe longitudinal direction of the flange. `In this manner the nails will function as joint-nailing by `successive transmission of load, and thus they will also serve as an additional safety factor for the individual layersof boards of the flanges, should the gluing between said layers or between the joints fail to function. Finally, the nails will also act to transfer all stresses appearing between the flanges and the web and between the web boards.V

When timber of limited splitting resistance is used, beams with nailed lianges according tothe invention have practically no disposition to split even with relatively close nailing of the flanges. `They can `therefore be loaded so as to take full advantage of `thestrength of the` Wooden material used. This is due to a cooperation 'of several circumstances. In `the first place theactual flanges acquire in themselves aconsiderable splittingresistance by gluing together several different layers of boards to one another as the fibres in the different layers of boards .are never completely parallel but cross one another at a certain angle so that when they are glued they will block one anothers bres. The flanges thus acquire a consider'A ably greater strength and splitting resistan-ce than ordinary tirnber. Secondly, also the web boards extending-at aniangle to the flanges will contribute to an increased splitting resistance of the flanges. The parts of the web lying between the opposite pairs of flanges are not, however, blocked in the same way as the flanges by combining several layers. Splitting of the web boards can,however, according to the invention, be otherwise counteracted, namely by carefully arranging the boards of the diagonal panelling layers close together without any intervening space between the individual boards, whereupon nailing is effected right through the flange on one side of the web, then through both the diagonal panelling layers and, finally, into the flange on the other side of the web. The flanges extending in the longitudinal direction of the beam whichare glued together by vertical layers of board, will in this way block the boards of the diagonal panelling which are laid close together and thus prevent splitting also in the web boards.

The nails which are thin relative to the length thereof and which are used for the flanges Yalso result ina remarkable increase in the splitting .resistance of those wooden sections which are nailed `through to resist splitting, or vice versa, a considerable increase in the possibilities of performing close nailing will be obtained. This in turn represents a corresponding increase in the bearing capacity and strength of the beam.

Ordinary wire nails of round sectionare usually characterized by the cross dimension increasing with the length of nail, and this cross size is so great with the nail lengths which are suitable for nailing the flanges: that the 'nail is very apt, especially with hard and strong kinds of woods, to cause splitting when `thenailing is close. By way of example, the ordinary round wire nail with a length of'6 has a cross dimension of 0.26, and `8 round ordinary wire nails have a cross size of 0.33, whereas for nailed beams according to the invention the most suitablecross dimension for 6" nails is only about 0.20'Hand the corresponding cross size for 8" nails is about 0.24. I have found that the latter size should not be `increasedmaterially even if still longer nails than 8 be used. If the beam flanges are connected to lthe web with these nails which are thin in proportion to their length, I have found that the risk of splitting is reduced and the bearing capacity increased to a very high degree. In additionl have found that by using nails of one andthe same quantity by weight, and consequently nails of one and the same cost, the bearing capacity of the nailed assembly increases, irrespective of the risk of splitting, according as the cross dimension of the nail decreases. The nailing according to the invention, with specially thin nails in relation to the length of nail, therefore entails decided advantages from several points of View.

One object of the invention is also to provide afurther improvement of the splitting resisting propertyof `the through-nailed beam portionsby arranging the nailing `according Vto `a predetermined pattern. In this embodiment the nailing between flanges and web is arranged in longitudinal rows generally alongr `the grain, the number of which rows may be increased successively in accordance with `the increasing width of the flanges. The nails in each row are staggered at `either side of the theoretical'line of row at a small distance from said line as viewed in the transverse direction of the flange, and the nails in every second row are displaced at a distance approximately corresponding to half the space between the rows longitudinally of the flange in relation to the nails in adjacent rows. This arrangement results in several advantages. On the one hand, the geometrically simple and definitely xed placing of the nails facilitates a rational construction and manufacture of the beam and, on the other hand, there are obtained no splitting releasing rows of adjacent nails in any direction. Finally, in nailing according to this pattern the ange nails are prevented from being located in oblique rows coinciding with the joints between the boards of the web, independently of the magnitude of the spacing of the nails. This is Very important since otherwise a great number of nails could enter the joint between adjacent boards of the web so as to be more or less inoperative, thus resulting in a reduced strength of the beam.

A still further object of the invention is to eiect the nailing by means of so-called grooved wire nails made of a material of a relatively high yield limit. I have found that nails of this kind have a smaller tendency of causing splitting in the wood than ordinary nails of square cross-section having the same edge dimensions. This is also true, to a still higher extent, in respect of round Wire nails of the same bearing capacity. The

' grooves also cause that the nails will be reinforced at the four corners, thus resulting in an increased rigidness in relation to the consumption of material. The same remarks apply to the use of material having a high yield limit. A particularly high strength of beams according to the invention may be obtained if the nails used have small edge dimensions but are as rigid and resistive as possible to deformations when subjected to load perpendicularly to the longitudinal direction of the nail. In this connection a grooved nail made of a hard material or metal has been found to be particularly advantageous.

Some embodiments of the invention are shown in the accompanying drawings in which:

Fig. 1 shows an elevation of a portion of a beam according to the invention.

Fig. 2 is a cross section of this beam on the line II-II in Fig. 1, and

Fig. 3 is a longitudinal section of the beam on the line III-III in Fig. 1.

Fig. 4 shows a favourable pattern of nailing in the beam anges according to Fig. 1 and Fig. 5 shows, by way of comparison, how one type of a joint of the beam flanges has hitherto been made in a known manner with external joint pieces.

Fig. 6 shows, in elevation, a beam with a broken or angular outline composed of two individually straight beam sections, which are shown in detail in Fig. 7 when taken apart.

Fig. 8 shows on a larger scale a corner joint of such beam portions after being assembled, and

Fig. 9 shows a view of one of the beam portions on the line IX-IX in Fig. 7.

Fig. 10 is a similar view of the other beam portion, viewed on the line X-X in Fig. 7.

Fig. 11 is a side View of a piece of beam constructed according to the invention and having special web stifteners.

Fig. 12 shows the same beam seen in cross section, on the line XII- XII in Fig. 11.

Fig. 13 shows an elevation, and Fig. 14, a cross section on the line XIV-XIV in Fig. 13, of a further embodiment of such a beam.

Fig. 15 shows an example of a known joint and Fig. 16 a joint according to the invention, between two individually straight assembled beams so as to form a combined beam with great bending strength and with an apex at the joint.

Fig. 17 shows on a larger scale, seen from the side, a joint-piece for this construction of beam, and

Fig. 18 shows a side view of the whole joint on the same scale. V

Fig. 19 shows a plan view of the joint and Fig. 20 is a cross section of the joint according to Fig. 18, viewed along the line XX-XX.

Fig. 21 shows an embodiment illustrating a modified use of the beam corner construction according to the invention.

Fig. 22 illustrates diagrammatically a view of a tool which may be used in the nailing operation.

Fig. 23 shows a side view of an embodiment of a purlin arrangement made according to the invention, and

Fig. 24 shows the same arrangement in top plan view.

ln Figs. l `to 3, 1 and 2 indicate the boards of which the web of the beam is composed and which are arranged in two layers crossing each other diagonally. When constructing and nailing the beam said boards are laid close together without any intervening space in order to ensure greater security against splitting of the web. Flanges 3, 4 and 5, 6 respectively, each consisting of at least two layers of laminated boards, for example a, b, c, mutually glued together are attached to the upper and lower edges of the web of the beam. Each such lamination consists in its turn of a number of boards jointed longitudinally. Fig. 3 shows some oblique joints 6s shaped as hooks for the laminated boards a, b, c of iiange 6. It should be noted that in Fig. 3 the length of said hook joints are shown on a reduced scale in relation to the width of the boards.

The end of the beam is preferably tted with vertical strips or laths. These strips as well as the horizontal anges are attached to the web by means of nails 9, 1.0 driven in alternately from both sides of the beam in such a way that they entirely penetrate the nearest flange (for example flange 5) and both layers 1, of the diagonal panelling web, and partly penetrate mto the other ange (for example flange 6). According to Fig. 1 the nails which are driven in from the front of the beam are indicated by the symbol and those nails which are driven in from the back of the beam are indicated by the symbol Fig. 4 illustrates diagrammatically a favourable pattern of nailing in the flanges. The theoretical row lines are indicated at E, F, G and H. The spacing of the nalls driven in from the same side of the ange is indicated .at t. As shown in Fig. 4 the nails are displaced by the distance from the theoretical row line on either side of this line in the transverse direction of the flange. The distance between adjacent rows is indicated at r and it is seen that the displacement between the nails in the longitudinal direction of the flange in relation to the nails of adjacent rows is about The arrangements according to the invention enable the manufacture of beam constructions which with many kinds of Wood, such as Douglas tir, yellow pine etc. would not be possible to make in any other manner, at least not if the strength of the Wood in the flanges 1s to be utilized to full extent.

Some of the advantages of me invention will be clear by a comparison with Fig. 5 which illustrates a known construction of joining ordinary solid ange strips or laths to stress transferring anges of great length.

In Fig. 5 21, 22 indicate the two layers of diagonal panelling in the web of the beam to which anges 23, 24 of solid timber are joined. The anges 23, 24 are joined in a known way at transverse joints 23s, 24s. External joint- pieces 25, 26 arranged on the outside of these joints, are joined to the ends of the beams to be jointed by means of nails 27, 28 and at the same time transmit the forces which the joints 23s and 24s are un- `able lto take.

`the web boards. `web boards, which merely have to transmit the transversal It `should be lobserved that, in principle, joints 23s, 24s could be made as glued oblique joints in the same way as in the beam in Figs. l to 3, but in practice such a joint does not require anything like thesame strength or reliability as when it is` arrangeduaccording to Figs. l to 3.

The thickness of the anges of the beam is the same in Fig. 5 as in Fig. 3 but yet there is required considerably longer and thus alsoheavier nails in the beam according to Fig. 5 than in thebeam according to Fig. 3. The n creased length of the nails in Fig. 5 and the resulting in crease of the cross-section of the nail causes a considerably increased weight and cost of the nails required and also an increase `of the splitting tendency `of the jointed flanges and thus also a reduced strength of the latter. It should be noted also, that liange joints according to Fig. 3 have a considerably nicer appearance than according to Fig. 5.

When using especially hard or brittle timber the splitting resistance as a result of close nailing can, according to a further development off the invention, be increased in a high degree by special arrangements. Thus according to one form of construction the flanges are made of hard or high grade timber which is generally also characterized by great strength and is primarily ensured against splitting by gluing together, as described above, several layers of strips with partially crossing grains. The web boards, on the other hand, may be made of low-grade or less hard and less strong timber, full advantage being taken of the good nailing properties of As `a matter of fact the stresses in the forces (shear) in a beam of the present type, have been found to be of a lower magnitude than the axial and bending stresses in the flanges. As a rule such stresses are, at the most, about 1/3 to 1/2 of the stresses in the flanges which are decisive of the dimensions. Several advantages may be `attained by using a combination of lower grade, but softer and tougher timber in the beam web, and highgrade or hard timber which is more inclined to split in the flanges. The advantages include a lower cost for the assembled beam, increased security against splitting for the web of the beam, and also a slightly lighter beam, and this is attained without the bending strength of the assembled beam being `reduced as in rst line this is determined by the high-grade timber in the flanges. It should be observed in this respect that the web boards in the present case have to take the relatively low stress right cut to the upper and lower edges of the beam, and in this respect distinguish considerably from., for example, so called glued laminated beams in which the stresses in the entire beam section increase continuously trom the central section towards its edges.

The web may also be made of boards of different kind of wood but having mutually the same thickness. Boards of wood having high strength, particularly a high strength to the local pressure from the nails, are placed in those portions of the web of the beam (usually in the vicinity of the supports olf the beams) where the transversal forces are great while the remainder of the web of the beam is made of timber having the lower strength. A combination of this kind enables a further increase of the strength and a reduction of the costs for the timber required for the beam, and also a favourable contrast effect, for instance between timbers of different colours.

As an example of suitable embodiments according to the invention I may mention beams having flanges of Douglas iir of higher strength quality and webs of Douglas iir of a lower strength quality, further, beams with flanges of Douglas r and web of spruce, `and also beams with flanges of Douglas tir, web of Douglas tir in the vicinity of the support of the beam and web of `spruce in other parts of the beam. Of course, the beams mayalso be lmade entirely ofthe same kind of timber and also of other timber classes than those nowmentioned, for instance, of hemlock, yellow pine and other timbers :which can be nailed.

In the web of the beam according to the invention I mayuse short pieces of boards (having a length of for instance 48), which often are obtained as: a` kind of inferior by-product in the production of ordinary saw time ber dimensions. In this manner an essential part ofthe ltimber `required for the construction of the beam may be obtained at an extremely low cost which as a rule is not possiblein other types of `supporting wooden constructions of the class now described.

The invention also allows for an arrangementfor connecting two 1beams `of the type in question in a bending resistive manner `at angles to `each other. Such bending resistant beam corners occur in many types of constructions, such as frame constructions, arches, beams with broken `outline etc. It is also possible by meansof the invention to produce simply and cheaply larger frame and arched structures `of such a nature on a factory-scale, such `structures being too bulky to transport fully assembled. They can, however, madein accordance with the invention, be transported as separate, straight and easily transportable parts which on the building site can be assembled to the frame corners etc. which have a good strength to bending stresses and which are requiredfor the stability of the Ibuilt-up supporting units. A remarkable advantage of the invention is that the joint at an angle between two parts of the beam can be carried out on the `building site solely by means of nailing. Then again the bend-resisting bonds according to the invention can be made with the same resistance to bending stresses as both the connected beam sections individually, and this can be 4made without the dimensions of the corner joints being larger than those of the respective beam sections.

A construction of the kind above indicated is illustrated in Figs. 6 to 10 showing -that of the two beams I and'II which are to 'be interconnected in a manner enabling great resistance to `bending stresses one beam I at one end is constructed as a stii plate which is resistant to bending stresses in alldirections of the plane of the 'beam and is i-n the form of a quadri-lateral S. This stiff part is formed by the part of the web of double diagonal panelling 51, 52 of beam I `within the said quadrilateral, also of parts of anges 53, 54 of beam I which are arranged within said quadrilateral, and, iinally, of one or more special transversals 55 and, if desired, S6 arranged lbetween the said iianges 53, 54 and extending in the same direction as the flanges of the second beam II. Then again beam Il is equipped with freely protruding forkshaped flanges 59a, 60a which at the building site are mounted so as to embrace the said transversQs 56 and/ or 55 on 4bothsides of beam I. Flanges 59a, 60a of 'beam `II are then `connected to transversal 55 or transversals 55, 56 of beam I together with the diagonal panelling ofthe latter beam. Simultaneously the transversals for beam I are also connected to the web of diagonal panelling of the same beam `by nailing through the anges, transversals and the web of the beam. This is done with nails the edge-side of which is small, normally about J/30 or in extremecases 1/25 of the length of the nail, similarly to what has been set forth above.

According to Figs. 6 to l() beam I thus consists of a web of diagonal panel boards 51, 52 and flanges 53, 54 which are joined to the web 'by nailing, and extend along the whole length of the web. The transversal `S5 or transversals 55, 56 are also connected to the web. Of these, transversal 55 should have the same thickness as flanges 53, 54, whereas transversal 56 can be thinner or be omitted yby being substituted altogether by flange S9 in Ibeam II. Transversal S5 or transversals 55, 56 in Fig. 7 are appropriately only connected with a relatively few retaining nails to beam section I when the beam sections are being manufactured at a factory.

The sections ofthe diagonal panel boards of beam I enclosed within the quadrilateral 53, 55, 54, 56 should preferably be parallel to both the respective diagonals of the quadrilateral. In the remaining part of beam I, however, the direction of the diagonal boards can be adjusted, if desired, by separate oblique boards so that both layers of the diagonal panelling slope or incline equally to the mean longitudinal direction of the beam.

Beam II also consists of a web of diagonal panel boards 57, S with llanges 59, 60 and preferably with a lath or strip 61 which forms a terminal or termination for the diagonal web 57, 58. This last mentioned web terminates along line a-rz in Fig. 6, corresponding to the other edge of flange 54 in beam I in the assembled structure. The flanges 59 and 60 continue with their outer ends in fork-shaped extensions 59a, 60a (Fig. 7). The lengths of these latter are adjusted so that when the forks are disposed along the respective transversals 56 and 55 at beam I they reach the outer edge of the outer ange 53 of beam I. It must also be taken into consideration in this connection that the mutual free distance (in the transverse direction of the beam) between flanges of the same pair of flanges, for example 60a, shall be so adapted (by a suitable design of the flanges, Fig. 9) that when the flange forks 59a, 60a of beam II are disposed along the transversals 55, 56 of beam I no substantial clearance will arise lbetween connecting parts of beams I and II. When beams I and II have thus been placed together nails (the thickness of which, in similarity with the nailing of the flanges, sha-ll be small in relation to the length of the nail) sha1-l be driven right through ange forks 59a, 60a and into transversals 55, 56 together with the intermediary parts of the diagonal panel webs 51, 52. As a rule the flange portions 54 and 61 of Fig. 8 should also be interconnected for transferring transversal shear which can be effected by connecting a plate of thick plywood or of double diagonal panelling to the parts 54 and 61 by means of nails.

It has been found that if the nailing between the flange forks of beam II and the transversals of beam I is carried out approximately as closely as the nailing between the anges and the web, Ilche connecting arrangement now described lbetween two beam sections which form an angle can transmit bending moments and normal forces which correspond to full utilization of the strength in the beam sections outside the corner joint.

It is also an object of the invention to make possible the production of specially deep, or highly loaded, beams having webs of two layers of diagonal panel boards while using thin boards (for example 1") without the web of the :beam acquiring any tendency to buckle laterally. To this purpose there are arranged on each side of the web of the beam, pairs of laths or strips which are weak in relation to the ilanges. Said strips extend mainly parallel or at right angles to the beam flanges. The strips which are parallel to the lianges are placed so that they divide the free height of web between the inner edges of the flanges into two or more partial heights. Nails are then driven in from both sides of the beam through the said strips, further right through the web of the beam and,

lfinally, through part of the opposite strip. Opposite strips of the same pair will now become mutually anchored to each other so as to resist stresses and this is made possible by interconnecting the strips through the beam web by the nails which are driven in from both sides. It is advisable, however, to prevent the nailing from penetrating to the outer edge of an opposite strip. In this manner every pair of opposite strips hereby will receive a rigidity and strength which is many times greater than the rigidity and strength of the individual lath or strip. At the same time the pairs of strips thus mutually inten connected will join together both layers of the diagonal panelling of the diagonal panel beam eifectively. Of both these layers the boards of one layer are normally exposed to tension stresses throughout their entire length, thereby automatically tending to keep straight, whereas the boards of the other layer are exposed to compression stresses which tend to buckle the last mentioned boards sideways or laterally. It has now been found that the coupling of the boards, subjected to compression stresses, to the boards subjected to` tension stresses, by the medium of, and under cooperation with the interconnected pairs of -strips as described above greatly increases the buckling strength of the diagonal panel boards.

According to a modiiication of the invention the laths or strips nailed together in pairs are arranged in a direction at approximately right angles to the beam anges instead of parallel to them. They are placed between the inner edges of the beam flanges at a mutually free distance which is less than the free height or depth of the beam web (that is the height between the inner edges of the beam flanges). According to still another modification a series of pairs of strips or laths arranged at right angles to the ilanges can alternate with pairs of strips of laths arranged on certain lengths of the beams and parallel to the flanges. In doing so I prefer to use the rst-mentioned type when the transversal force in the beam is relatively great, and the last-mentioned type when the said force is small.

Some embodiments of the invention according to the construction now indicated are shown in Figs. 11-14. The beam shown in Figs. ll and l2 comprises a web of diagonal panel boards 61a, 61b having flanges 62, 63. On account of transversal forces in the beam, for example, the panel boards 61a are compressed and the boards 6111 are tensioned in a certain part of the beam. Laths 64a, 64b are arranged on both sides of the web. They are interconnected in pairs through the web by means of nailing 65 of the character described.

Figs. 13 and 14 show another arrangement of the web stiifeners. Here also 61a, 61b indicate the beam web, and 62, 63 the anges. In this case the web on the left part of the beam, according to Fig. 13, is reinforced or stittened 'by means of vertical laths 66 intercoupled in pairs on both sides of the web by means of nails 67 of the character described. The right hand section of the beam is fitted with web stiffeners 68 of the same type as 64a, 64b in Fig. 11. It can be pointed out here that it is also possible, and often appropriate, to combine web stiieners of the type shown in Fig. 11 with the type shown to the left in Fig. 13 by using the first-mentioned type in beams subjected to relatively small shearing forces and the last mentioned type in beams subjected to large shearing forces.

The invention also has the object of rendering possible interjoining of short beam elements into very long beams at the building place simply by nailing. In this respect the principle of joining ilanges to such beams is in itself known according to the method shown in Fig. 15, that is with superimposed joint-pieces of the same strength as the jointed flange 91. Apart from the fact that such a joint looks clumsy it is not possible either to obtain any great strength as the long, and consequently also heavy, nails 92 which are required for such a joint are inclined With the close nailing to split the timber in the joint pieces 90 and llanges 91. This applies particularly to heavier loading. These drawbacks are eliminated according to one embodiment of the invention by interjoining two beams in a bending resisting manner by connecting their ilanges by means of joint pieces, consisting of interglued boards of mainly the same thickness as the boards in the flanges which are to be jointed, the joint pieces being connected to the corresponding Ibeams by nails of the character described. Said boards are also so arranged as to always be connected to another board by means of gluing, whereby there is obtained a high resistance to splitting in through-nailing.

An embodiment of this kind is illustrated in Figs. 16-20 which show the interjoining of -two individually straight beams A and B to a single beam having good resistance to bending stresses and forming an apex at the joint. By

interjoining two beams in this way (which can be done at the building place), several advantages are gained. Firstly, the transport of large 'beams is considerably facilitated by only necessitating transportation of individually 4straight: and relatively short beam sections A and B. Secondly, the jointing arrangement also makes it possible to produce roof girders with a relatively slight slope on both sides (the arrangement shown in Figs. 640, on the other hand, is most suitable for joining beams With a greater angle between the beams). On the other hand, the necessity of jointing a roof -girder according to Figs. 16-20 in its middle section where the stress is greatest naturally places great demands on the 'strength of the joint.

Beam A consists of a web 71 with anges 72, 73, and beam B consists of a web 74 with flanges 75, 76. Flanges 72 and 75 are jointed by means of joint pieces 77 and the tlanges 73, 76 are jointed by means of joint pieces 78. `Beam webs 7l, 74 are jointed by means of special joint pieces 79. Figs. 17 and `18 show details of joint piece 77 seen from the side, and Fig. 19 the same joint piece seen from above, though only for one half of the beam ange (on one `side of the symmetry line of beam 80). Each of the anges 72 and 75 which are to be jointed consists, for example, of three layers of boards 72a, 72b, 72C and 75a, 75h, 75e respectively. The corresponding joint piece 77 likewise consists of three layers `of boards 77a, 771;, 77e each of the same thickness as the layers of boards in the flanges. The joint piece 77, however, can in addition be provided with still another layer `of boards 77d. This can be considerably less thick than the other layers of the joint piece. All layers a, b, c, d are mutually interglued and thereby block one another against the risk of splitting in close nailing because of the dissimilar libres in the layers. When jointing anges with a Ismaller or larger number of layers of boards than the number shown in Figs. 19 and 20, the number of layers in joint piece 77 is reduced or increased to the same extent as in the flanges.

ln the joint-piece 77 in Fig. 19 the layer '77a can be regarded as joining material for the layers of boards of ilanges 72a and 75a; the layer of the joint piece 77b can be regarded as joining material for the flange layers 72b and 75b, and the `layers 77C, 77d can be regarded as joining material for the ange layers 72C and 75C. The `joint piece 77 is connected to flanges 72 and 75 by means of nailing, if desired in combination with gluing. The lengths ef, fg, gli, in Fig. 19 are adjusted so as to allow space for the number of nails required to transmit the force in ilange section 72a to ange section 77a of the joint piece, and to provide on the distance fg a corresponding space for nailing the joint between flange layer 72b and the layer of the joint piece 77h, etc.

The jointpiece according to the invention has several decided advantages as compared with the known lapping joint shown in Fig. l5. Thus the length of the requisite joint nails, and consequently also their heaviness, is thus considerably reduced. The cost of nailing is hereby reduced, and the risk of splitting is reduced, the strength of the joint thus being increased. Finally, the joining pieces 77, 73 according to the invention (Figs. 17, l) acquire a much more attractive appearance than the superimposed joining piece 90 shown in Fig. l5.

Joining pieces according to the invention `can also be used to interjoin short beam pieces so as to obtain continuous straight beams of great length. irrespective of transport dil'culties beams of practically unlimited length can be produced by nailing at the building place short beams which are factory made but transportable. In such a. case the joint pieces are made of uniform width in contrast to the joint piece with broken outline shown in Fig. 17.

The invention also comprises an arrangement for joining the web when interjoining two beams to form a single beam, which shows great resistance to bending stresses. According tothis `arrangement the web 'of both beams is provided, at the joint, with laths extending in the longitudinal direction of the joint. These laths are united with corresponding laths in the associated beam by means of joining plates of thick plywood, for example or by double layers of boards mutually interglued temporarily and crossing one another diagonally. Such joining plates are fixed by nailing to the aforesaid laths and the internal webs.

An embodiment of this kind is shown in. Figs. 18 and 20. Each beam lweb 7l and 74 of the beams the webs of which are to be interjointed consists of two layers of boards 71a, 71h and 74a, 741) respectively, arranged diagonally. Close to the joint each web is terminated by laths 81a, 8117 and 82a, S21) respectively, which are provisionally fixed to one another and to the respective beam Webs by spaced nailing S3, S4 of the character described. Said laths are finished before the joining, for example when the beams are made at the factory.

For the joint I use joint plates which if desired can be made of thick plywood though l prefer to make them, for example, of two layers of diagonal boards 85a, dn and 851?, 86h, respectively, which are provisionally glued together. The joining plates are connected at the point of assembly to joining laths S1 and S2 of both beams by nailing. This is done with nails of the character described. The intergluing between both layers of the diagonal panelling of the joining plates cannot be eirpected to hold in the long run because the ber directions of the glued, relatively thick layers of boards cross one another at right angles, or almost right angles. The gluing in question has therefore been indicated here as being provisional. Nevertheless the gluing is of great importance since when the joining plates are carefully stored until they are ready for assembly the gluing causes both layers of boards to interlock in the close nailing made on assembling by means of the plates. As a result of this interlocking effect such close nailing can be carried out without any risk of splitting of the individual boards of the joining plates. lt is: true that this gluing loses its strength after some time, but the joining plate is nevertheless found to retain its anti-splitting capacity. This appears to be due to the wood of the plate adjusting itself plastically to the nailing in time, but such adjustment cannot take place already whenthe momentary assembling nailing is made.

`Fig. 2l shows an embodiment of the invention in which the `quadrilateral S according to Fig. 7 is arranged at the joint between a lattice-girder 9i) and a beam 91. In the beam 99 the web is substituted by separate diagonals or laths `92, 93 connected to the wooden anges `of the beam. The `quadrilateral S is made of two layers of diagonal boards with nailing substantially as described with reference to Figs. 6 to l8. Beam 91 may or may not have any diagonal panel web between its Wooden anges.

lIn many cases it is not-economical to elfect the nailing according tothe invention manually but by means of a tool, for instance by means of a percussion tool operated by compressed air or by other means. A special tool hasbeen developed to this purpose and is shown diagrammatically in longitudinal section in Fig. 22. It cornprises a percussion tool 94 of ordinary type having a cylindrical pin or bolt 95 which 4is operated by compressed air in `known manner so as to perform a percussion movement. The pin 95 has an enlarged head or ange 96 serving as an abutment for a sleeve v97 of rubber, plastic or other elastic but not too soft material. The sleeve 97 is extended slightly at 97a beyond the free end 98 or the bolt 95which is adapted to engagethe head of the vnail 99 so `as to drive the latter into the wooden pieces 100, for instance the ang'e strips of the beam described, `on operating the percussion `bolt 95. One function of the rubber sleeve 97 is to guide the bolt 95 so as to prevent it from sliding `off the head ofthe nail 99 during the percussion operation. Another remarkable effect of the rubber sleeve 97 is due to its extension 97a which for instance has a length of about 10 mm. When the tool is caused to engage the head of the nail and the compressed air is supplied the said extension 97a will be compressed according as the percussion tool is acting to drive the head of the nail into the wood so that this sleeve will protect the wood around the head of the nail from being damaged by the tool, yet Without preventing said head from being driven in close to the wooden surface.

The invention also includes a favourable construction of a purlin or joist of a roof with the use of nailing of the character described. Figs. 23 and 24 illustrate an embodiment of this kind. In these gures 110, 111 indicate two roof beams or trusses, for instance constructed in accordance with any of the embodiments now described. On the top of said trusses the purlins which carry the roofing (boards, sheet metal etc.) extend transversely to the longitudinal direction of trusses. In many cases the purlins now in use are made in the form of separate beams of solid timber or lumber having sub stantially the same length as `the space between the trusses, and freely supported by said trusses, but the purlins may also be made continuous, for instance by causing the purlins to overlap one another on the trusses. However, this last mentioned construction necessitates the use of purlin beams having a greater length than the space between the trusses and the consequence of this is that rather great timber lengths are required for the purlins. It is often diicult to obtain timber of suiiciently great lengths if the space between the trusses is great and in any case the costs will increase with increasing lengths of the timber. This disadvantage is very serious since for other reasons it is desired to arrange the trusses at so great a distance as possible from one another so as to reduce the number of trusses for a given roof area. On the other hand continuous purlins or joists have the advantage of providing a more favourable distribution of the moments and a reduced bending than freely supported purlins having a span equal to the space between the trusses.

Now, according to the invention there is provided an arrangement which enables obtaining a favourable distribution of moments simultaneously with the great economy of material inherent with the continuous purlins, yet without necessitating great length of the timber or lumber, and which, in addition, enables an adjustment of the cross-sectional area of the purlin to the bending moment. A combination of these advantages results in a very remarkable economy of material in relation to the ordinary itype of purlins which are laid freely between the trusses. The saving of the volume of material is theoretically about 50%, and since it is possible to utilize rather short lengths of timber the costs per unit of volume will be low.

As illustrated in Figs. 23 and 24 these advantages are gained, according to the invention, by using wooden purlin elements 112 of shorter length than the distance between the trusses or beams 110, 111, such short elements being lengthened by a pair of double wooden pieces 113, 114. The single wood piece 112 is arranged in the central part of the eld between the supporting trusses 110, 111 and the double wooden pieces 113, 114 are arranged on the top of the supporting trusses. Each pair of wooden pieces 113, 114 is adapted to receive the respective end of the purlin element 112 in a fork-like manner between the individual wooden pieces of each pair as shown in Fig. 24, so that the end of the element 112 will overlap the ends of the pieces 113, 114. To this purpose the wooden pieces in each pair are spaced at a distance corresponding to the width of the intermediary element 112. If desired, spacers 11S may be arranged between the wooden pieces 113, 114 and fixed thereto by means of nails. The purlin element 112 is 12 joined to the double wooden pieces 113, 114 by nailing 116 which is to be dimensioned so as Ito bear the moment stresses and thus render the joint resistive to bending stresses. The nailing joints 116 should preferably be placed at such a distance from the supporting means or 111, that thebending moments at the place of the joint will be as small as possible. As shown at 11611, the nailing for every second purlin 112, can be made in a more simple manner so as to bear the shear stresses only. In this case the joints will be made as articulations. lt is easily 4seen that this arrangement renders it possible to adjust the distance of the joints 116, 116a from the support on the trusses 110, 111 and to adjust the distribution of lthe moments on and between said supports so as to utilize the strength of the wooden pieces 112-114 in an extremely advantageous manner.

It a tendency of splitting should arise at the places of nailing 116, 116er metal sheets may be interposed between the overlapping wooden parts and the nails are driven through these sheets and into the wooden parts.

The pairs of wooden pieces 113, 114 may be attached to the trusses 110, 111 by means of oblique nailing, for instance.

At the ends of the roof the free ends of the purlin elements 112 may rest on suitable supports without any lengthening arrangement 113, 114, if desired.

What I claim is:

l. A wooden beam construction comprising a web of at least two layers of boards disposed in each layer in edge to edge relation to each other and with their lengths in angular relation to the lengths of the boards in the other layer, said lengths in each layer extending diagonally with respect to the length of the beam, flange members of wood disposed with the lengths thereof generally parallel to the grain extending along the respective opposite lengthwise edge portions of the beam at opposite faces of said web, each llange member comprising at least two boards in laminated face-to-face relation to each other and to said web at the adjacent face of the web, and nails driven through the boards of the respective ange members into said web, said nails being disposed in a plurality of rows lengthwise of said ange members and staggered in each row with respect to the general line of the grain of the wood of said flange members, said nails being disposed in groups along said rows with the nails that are disposed in adjacent rows staggered in relation to each other along respective lines transverse to said rows, said lines being spaced along said rows, the spacing in each group between the nails staggered along the transverse line of said group being approximately V2 the spacing between said adjacent rows of nails.

2. A wooden beam construction as defined in claim 1 in which all of the nails of a given group are at the same side of the respective lines of the rows, the nails of two adjacent groups along the ange member being disposed at opposite sides of the respective lines of the rows.

3. A wooden beam construction as delined in claim l which comprises wooden strips disposed in face-to-face relation to the respective faces of said web and extending with their lengths in registering relation to each other over a portion of the extent of said web between said iiange members and generally parallel to said ange members so as to divide the space between said ange members into at least two portions extending longitudinally of the beam.

4. A wooden beam construction as dened in claim 3 in which additional strips in face-to-face relation to the respective faces of said web extend transversely of said ange members so as to divide the space between said flange members into portions spaced longitudinally along the beam.

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS -Nutt Dec. 22, 1936 Prosnack Mar. 11, 1941 Lank Sept. 18, 1945 Winkel Nov. 27, 1945 Sahlherg Dec. 4, 1945 'Thomas Dec. 30, 1947 14 Shannon Feb. 13, 1951 Brosenius Aug. 26, 1952 FOREIGN PATENTS Sweden Aug. 17, 1943 Sweden Aug. 15, 1944 Sweden Sept. 5, 1944 Sweden July 10, 1945 Sweden Mar. 10, 1949

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