US3857218A

US3857218A - Truss joists having edge pin connectors

Info

Publication number: US3857218A
Application number: US00380215A
Authority: US
Inventors: T Gilb
Original assignee: Simpson Manufacturing Co Inc
Current assignee: Simpson Strong Tie Co Inc; Simpson Manufacturing Co Inc
Priority date: 1973-07-18
Filing date: 1973-07-18
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31

Abstract

A truss joist having wood chords, connectors mounted on said chords, sheet metal and a plurality of metal strut members arranged diagonally between said chords joined to said connectors by metal pins which are partially embedded in transverse semicircular channels cut in the inner faces of the chords.

Description

United States Patent [191 Gilb Dec. 31, 1974 TRUSS JOISTS HAVING EDGE PIN 3,268,251 8/1966 Troutner 52/693 CONNECTORS 3,422,591 1/1969 Troutner 3,449,997 6/l969 Couch .f. 85/13 [75] Inventor: Tyrell T. Gllb, Berkeley, Calif.

[73] Assignee: Simpson Manufacturing Co., Inc., Primary Examiner prank Abbott San Leandro, Cahf' Assistant Examiner-Carl D. Friedman [22] Filed; J ly 1 73 Attorney, Agent, or Firm-James P. Cypher [21] Appl. No.: 380,215

I ABSTRACT [52] U.S. Cl. 52/694, 52/692 [51] Int. Cl. E04c 3/18 A mlsslolst havlng Wood chords connectors mounted [58] 'Field or Search 52/693, 694, 692, 690, on said chords, sheet metal and a plurality of metal 52 721 53 9 39. 44 753 E, 751 752 strut members arranged diagonally between said 52/753 85/11, 13 chords joined to said connectors by metal pins which are partially embedded in transverse semi-circular 5 R f r n Cited channels cut in the inner faces-of the chords.

UNITED STATES PATENTS 9 Claims, 19 Drawing Figures 2,764,108 9/1956 Fmdleton 52/642 PATENIH] [1EC3 I I974 FIG.7

PATENIEB I974 3,857. 2 18

sum

3 or 4 BACKGROUND OF THE INVENTION All steel trusses date back well over 100 years. Connections between the chords and webs were located on the center lines of the chords. Except for the generally known light trusses no significant new all-steel truss joists have been forthcoming. The market, particularly in the western states where lumber-based construction is more prevalent, requires cheaper trusses.

About twelve years ago, a composite chord came onto the market having wood chords and steel webs. Like the all-steel truss joists, the composite chord truss followed the established design of placing the web and chord connection at the center line of the chord. The design criteria required boring of holes through the center of the wood chord, usually through the width of the chord, thereby considerably weakening the chord in tension. Moreover, the boring of the holes and encapsulating the joint pin rendered the joint the weakest part of the design and dependent upon the wood grades for strength values.

Rapidly rising prices ofwood and the increasing scar- 3 SUMMARY OF THE INVENTION The goal of the present invention is to substantially increase the spans possible with composite wood chord and steel struts at significantly lower costs in materials and fabrication.

The gist of the present invention is the use of edge pin connectors with rotational restraint design rather than the customary center drilled chord and encapsulated pin design. By encapsulating the joint area of the wood chord with metal, the whole joint area becomes the strongest area of the chords rather than the weakest as inherently true of present systems.

Edge pin connectors were further searched at the Smithsonian with special emphasis onthe l8lO-l850 period when the earliest efforts were made to construct railroad bridges using wood and steel composite trusses. Two days intensive search disclosed no evidence of it although in retrospect, such a connector would have solved some of the serious connector problems they ran into at that time which eventually led to substantially all-wood truss bridges for the bulk of the railroad era. I

An object of the present invention is to provide a single wood to metal connector which can be used in completely assemblying a truss and thereby avoid the numerous bits and pieces" of assorted complex fittings presently used.

Another object is to provide identical connectors at all the joints whether they be end or intermediate joints Still another object is to provide a connector which will pennit the use of lower grade woods for the chords, such as F-IOOO or F-l450 common lumber as opposed to F-240O machine graded lumber as used in drilled pin trusses.

Another object is to provide a connector which can be used in light, medium" and heavy" type trusses.

An object is to provide a connector method which will provide high strength and reliability yet is relatively easyand inexpensive to fabricate without highly precise joint-control with consequent high costs and undesirable unique product controls required for specific jobs.

Another object is to increase ultimate tested load values by not less than one-third above pin nonencapsulated trusses, and to eleminate explosive total failure" by chord splitting at the pin under ultimate load.

An object is to provide a system without splitting tendency so that certain species of wood with otherwise good characteristics for chords, but split-prone, can be used with the new system, and it is unnecessary to block the sides of the chords at the ends.

A further object is to provide a connector which is attached to the wood chord without nails.

Still another object is to avoid the hazard of knots and other wood imperfections far more effectively than drilled pin connections where imperfections in the wood must be kept well-away from any proximity to the drilled hole area.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of portions of a truss constructed in accordance with the present invention.

FIG. 2 is an enlarged detail of the connector taken at line 2-2 on FIG. 1.

FIG. 3 is an enlarged detail of the portion of the wood chord which accepts the connector.

FIG. 4 is a cross section of the chord portion taken along line 4-4 of FIG. 3.

FIG. 5 is a top plan view of the chord shown in FIG. 3.

FIG. 6 is a top plan view of the connector mounted on the chord.

FIG. 7 is a bottom plan view of the connector mounted on the chord.

FIG. 8 is a cross sectional view taken along line 8-8 of FIG. 6.

FIG. 9 is a cross section taken along line 9-9 of FIG. 8.

FIG. 10 is a plan view of the connector cut from a flat metal sheet before bending.

FIG. 11 is a side view of the connector shown in FIG. 10.

FIG. 12 is a front elevation view of the connector shown in FIG. 10..

FIG. 13 is atop plan view of the connector as viewed along line 13-13 of FIG. 12.

FIG. 14 is a perspective view of a pair of connectors shown in side by side relation as they would appear when assembled on the chord.

FIG. 15 is a side elelvation view of the end connector of the present invention shown in place on a bearing plate.

FIG. 16 is a side elevation view of the end connector of the present inventionshown in an alternate end type bearing.

FIG. 17 is a side elevation view of the end connector of the present invention shown in another alternate end type bearingarrangement.

FIG. 18 is a perspective view of the connector of the present invention shown in a double truss arrangement.

FIG. 19 is a perspective view of the connector of the present invention shown in an alternate form connection with a chord wider than the connector.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The present invention consists briefly of a truss joist having an upper chord 1, a lower chord 2 and a plurality of identical connectors mounted on the chords and shown in FIG. 1 as connectors 3-8. A plurality of strut members 9-14 are arranged diagonally between the chords and means pivotally secure the ends of the struts to the connectors at pivot points 16-21 located inwardly of the center lines.

The heart of the present invention is the sheet metal connector which is shown in detail in FIGS. -14. The

preferred form of the invention consists of a seat 23 with an upstanding leg 24 connected at a fold line 26 to one side of the seat and an upstanding arm 27 connected at a fold line 28 to the other end of the seat. An opening 29 is formed in the leg and an opening 31 is formed in the arm for receipt of a pin 32 which is mounted transversely of the chords.

The arms and legs of the U-shaped connector are formed so as to make approximately an angle of 30 with a line 33 perpendicular to the axis 34 of the chord. Notethat perpendicular line 36 falls approximately at the outside edge 37 of the seat and an outside edge of the opening 31 as shown in FIG. 11.

The form of the invention shown in FIGS. 10-14 has a flange 38 on the leading edge of the arm and a flange 39 on the trailing edge of the arm. Also shown is a cutting tooth 41 formed in leading relationship to the flange 38 and a tooth 42 formed in leading relationship to the flange 39. I i The skewed U-shaped connectors are used in pairs as shown in FIG. 14 with the mirror image connector designated by the same numbers but differentiated by prime marks after each number.

In small chord members such as 2 X 4's, it has been found that 16 ga. metal having a hardness of about RB 50 seems the most qualified. In some applications where the hardness of the metal is R-B 7O, 18 ga. may be satisfactory.

In the present design, a tube or a pin will work. Since the pin or tube is placed on the outside of the chord rather than encapsulating it within the chord, various size pins are possible, even for the small 2 X 4 chords. It is no longer necessary to make the pin small enough so that there will be a sufficient amount of wood between the pin and the outside edge of the chord. Further, the limiting factor on an embedded pin is actually one-half the compressive value resolved as a splitting force, limited only by the members resistance to split.

In standard truss design, the pins are designed as cylindrical beams to resist both bending and shear; Bending usually determines size. In the present design, since the pins are in metal to metal contact with the connectors at their ends and in the middle, a V2-inch pin shows good over-all characteristics. Pins of %-inch and /:s-inch size may be used even for small chord 2 X 4s.

The pins should be hardened or heat-treated rod or bolt material of approximately commercial drillrod grade-45,000 psi. The force-reactions of the connector impose onlynominal forces along the axis of the pin. The retention force beteeen the pin and the outboard legs of the connectors is therefore only nominal. One means of retaining the pins is to make them about Aainch longer than the face of the outboard leg. Each pin end has a l/l6 inch taper 45 and a l/l6 X l/l6 inch maximum retainer ring. A clip-retainer is snapped into this ringed insert slot upon assembly.

Referring to FIGS. 3-9, the preparation of the wood chord at each joint and the interrelationship of the connector to the chord may be seen.

A major advantage of the present system over pin embedded truss systems is the fact that wood removal.

is much less than the wood removed by the pinembedded pin systems. This, of course, results in increased tension value for the wood chord (bottom chord). The savings in cutting is attributable to the fact that a slot is made in the face of the chord for only one half of the diameter of the pin. Further, since the pin is at the'face of the chord instead of the center line, the strut ends do not go as far into the wood to make the connection to the pin. Thus the slot required in the wood is limited to a one-half circle as opposed to the full circle slot required by embedded pins.

Referring to FIGS. 3-5, a transverse semi-circular channel 44 is cut in the face of the chord. For a /z-inch diameter pin, the groove is Ai-inch deep. A half segment recess 46 of a l inch circle, /2 inch wide, is then cut in the chord for receiving the ends of the struts and to permit some pivoting movement of the struts about the pin.

A slot 47 is formed through the chord as shown in FIG. 4 from the top face 48 to the bottom face 49 with the edges of the

slot

51 and 52 forming an angle of about 30 degrees with a line perpendicular to the axis of the chord. The slot is about 19/ 16 inches long by 3/16 inch wide and is within the recess and intersects the pin groove. Using the above cuts, in a chord of 1 /2 inches X 3 /2 inches and a /z-inch pin, there is approximately 4.00 sq. inches net chord section left for tension valueas opposed to about 3.25 sq. inches in the standard embedded pin system; a 23 percent increase.

The struts 9-14 which correspond to the web members of standard trusses are shorter because their ends are connected to pins mounted at the edges of the chords rather than to pins mounted at the center of the chords. The struts may be l-inch pipe with flattened ends 54 and 55 as shown in FIG. 8 with round openings 56 and 57 for receiving the pin 32. As in normal construction there is a /2 inch edge distance from the whole opening to the edges of the strut.

The connector may be either a single member or a pair of U-shaped members as shown. The early designs of the connector were a single member and were concentric with the leg and arm members rising at angles from the seat. Since in the edge mounted pin design, the forces impose rotational forces on the connector, the seat area forwardly of the pin is not resisting the forces and therefore the skewed U-shaped design resulted with a savings in metal and weight of the connector. It is this rotational force that is one of the major v and the pin thereby resisting sliding of the connector axially along the chord. Tests of the connectors without the

flanges

38 and 39 or the

teeth

41 and 42 were very successful and gave satisfactory results for some trusses, I

The

flange elements

38 and 39 sometimes referred to as the grip-groove members provide additional reinforcement to the ability of the connector to withstand rotational and axial forces and provide a means for holding the connector to the chord during fabrication. Grooves may be routed from the chord to receive the flanges in a force fit, but preferably, the flanges are preceeded with teeth so that by rapid light pounding with a soft head, such as hard rubber the teeth cut their own way into the wood. A pressure system, while workable, tends to push and distort the wood grain rather than provide a clean cutting action. Assembly could also be by a light reciprocatingair gun to drive-the flanges into the wood. I

As shown in FIG. 13, the seat area 23 is not rectangular but along the fold line 26, his shorter than along fold line 28 so that

sides

61 and 62 are at an angle. This construction permits the connectors to be cutfrom a metal strip at a substantial savings in wasted metal.

A major advantage of the present system is the fact that no special hardware is required for the end joint connectors where the loads are greatest. FIG. shows a close up of the chord bearing upon plate member 64. The opposite end of the chord is carried in a like manner on plate 65 as shown in FIG. 1. Since the identical connector is used at the end joint, no further description is required. For purposes of identification, like parts in FIG. 15 carry the additional identification of the letter a with each number. Note that the seat 23 'a overlaps the plate 64 by a considerable amount between the edge face 67 and a point 68. Thus no special end fittings for the chord are required nor is notching of the plate required. I

Where additional end bearing or lateral restraint is required, the end of the truss may be positioned as shown in FIG. 16. Again, the same connector is used as before and like parts are identified by adding theletter b to the numbers. Suitable notches can be made in the plate 70. to accommodate the strut 14, the pin 32b and the portions of the connector that protrude below the face 71 of the chord. Note that the entire seat area 23 'b is projected upon the plate member 70.

' Still another end bearing design is shown in FIG. 17

using the identical type connector previously de- 5 ously described connectors. The connector on the truss chord is identified by numbers followed by the letter 0 and the additional connector is described by numbers followed by the letter d. Note that pin 32c serves to connect all of the U-shaped connectors together. The only additional modification of the chord 1c required is the addition of slits to accommodate the ends of the legs and arms of the additional connector which protrude beyond the face 75 of the short member 73. Ad ditionally slits are made in the short member 73 to accomodate the ends of the connectors which protrude beyond face 71 of the chord.

The connector of the present invention can be used without dimensional change in chords which are wider than the connector such as in 2 X 6's. in FIG. 19, the connector is shown in a 2 X 6 numbered 77. A connector constructed in identical manner to the connectors described above is used and the parts are identified only by adding the letter e to each number. The only modification is in the chord in which end recesses and 86 are cut for receiving the ends of the connector legs, 242 and 24'e.

Still another design using the identical connectors as above describedis shown in F 1G. 18. The truss of FIG. 18 contains a second upper and lower wood chord disposed in side by side relationship with an identical chord as previously described. The first chord 78f and connector is numbered in like manner to the previously described components and is followed by the letter f. The second cord' 79f is fitted with an identical connector which is distinguished by the letter g after each similar part. The only modification is the fact that a single pin 81 is common to both connectors. Thus pin 81 is inserted through opening 29f in leg 24f and through the opening in arm 27f. The pin then passes through the opening in arm 27 'f and then through opening 29f in leg 24f. The same pin then passes through the opening in leg 24g and then through the opening in arm 27g. Finally, the pin 81 passes through the opening in arm 27g and then through opening 29'g in leg 24'g. The connectors throughout the truss'are identical to the connectors as shown in FIG. 18.

Struts

11f, 12f, 11g and 12g are illustrative of the type of strut used and are connected in thesame manner as previously described.

The assembly of the connectors on the chords is generally shown in FIG. 1. The identical connectors are used on the top and bottom chords. Where skewed U-shape connectors are used it is only necessary to angle the connectors so that the seat will restrain the rotational forces imposed at the offset pin. In a Warren truss as shown, the connectors on the top chord should be placed as shown with the angle of the connector legs pointing toward the center of the truss. On the other hand, the connectors on the bottom chord are oriented just the opposite with the connector legs angled toward the outside ends of the truss.

It has been found that for purposes of calculation it may be assumed that the pin is at the center of the chord.

I claim:

1. A truss joist comprising:

a. upper and lower wood chords, each having flat inner and outer faces and said chords having a width greater than their depth;

b. a plurality of sheet metal connectors mounted on said chords;

c. a plurality of strut members having openings f. said chords being formed with slots joining said inner and outer faces at the approximate center lines of said chords;

g. each of said connectors including a pair of seats engaging the outside faces of said chords, each connector having a pair of legs disposed in close fitting relation to the outside edges of said chords and connecting said seats and opposite ends of said pin and each of said connectors having an arm mounted in said slot connecting said seats and the mid portion of said pin;

h. said seats and legs of said connector and pin completely encapsulating said chords at their inner and outer faces and edges;

i. said connector arm being formed with an edge flange extending a substantial portion therealong and extending transversely of said chord for close fitting engagement therewith for transmitting forces from said strut members to the mid portions of said chords; and

j. said chords being formed with channels extending from their outer faces toward their inner faces at the approximate center line of said chords for force fit receipt of said flange of said connector.

2. 'A truss joist as described in claim 1 comprising:

a. said sheet metal connectors comprising a pair of U-shaped members, each having a seat, an upstanding leg formed with an opening for receipt of said pin, an upstanding arm formed with an opening for receipt of said pin and said arms having at least one edge formed with a flange extending a substantial portion therealong and extending transversely of said chord for close fitting engagement therewith.

3. A truss joist as described in claim 2 comprising:

a. the leading and trailing edges of said arms being formed with flanges extending a substantial portion thereof and extending transversely of said chord for close fitting engagement therewith.

4. A truss joist as described in claim 1 comprising:

a. a cutting tooth formed in leading relationship to each of said flanges for forming a channel in said chord upon being driven into said chord for force fitting occupany by said flange.

5. A truss joist as described in claim 1 comprising:

a. said arms and said legs being angularly related to the plane of said seat offsetting said pin from the center line of said seat.

6. A truss joist as described in claim 5 comprising:

a. said angle formed between said arms and legs of said connector with said connector seat being about 30.

7. A truss joist as described in claim 1 comprising:

a. a short wood bearing member having substantially thesame width and thickness of said upper chord and being similarly slotted and placed beneath the end of said upper chord;

b. a second set of said connectors each including a pair of Ushaped members having a seat engaging the outside face of said wood bearing member and said arms and legs connecting said seat and pin.

8. A truss joist as described in claim 1 comprising:

a. a second upper and lower wood chords disposed in side by side relationship with said upper and lower wood chords;

b. a plurality of second connectors mounted on said second chords;

c. a plurality of second strut members arranged diagonally between said second chords;

d. an elongated pin pivotally securing the ends of both sets of said struts to said connectors.

9. A truss joist comprising:

a. upper and lower wood chords;

b. a plurality of metal connectors mounted on said chords;

c. a plurality of strut members arranged diagonally between said chords;

d. means pivotally securing the ends of said struts to said connectors wherein the pivot points are located inwardly of the center lines of each of said chords;

e. said means includes a pin mounted transversely of said chords and partially outside the inner surfaces of said chords;

f. said chords being formed with a transverse groove for receiving said partially embedded pins.

g. said connectors include a seat engaging the outside face of said chords and a pair of legs connecting said seat and said pins and a retaining arm disposed from said legs connecting said seat and said pins; and

h. said chords having a width greater than the width of said connectors and being formed with recesses for receiving the ends of said struts, slots for receiving said retaining arms, and end recesses for receiving said connector legs.

Claims

1. A truss joist comprising: a. upper and lower wood chords, each having flat inner and outer faces and said chords having a width greater than their depth; b. a plurality of sheet metal connectors mounted on said chords; c. a plurality of strut members having openings formed in their ends and extending between said chords; d. a plurality of pins mounted transversely of said chords pivotally securing the ends of said struts at the midpoint of said pins to said connectors wherein the pivot points are located at said inner faces of each of said chords; e. said chords being formed with transverse semi-circular grooves having a depth approximately one-half the diameter of said pin for receiving said partially embedded pins; f. said chords being formed with slots joining said inner and outer faces at the approximate center lines of said chords; g. each of said connectors including a pair of seats engaging the outside faces of said chords, each connector having a pair of legs disposed in close fitting relation to the outside edges of said chords and connecting said seats and opposite ends of said pin and each of said connectors having an arm mounted in said slot connecting said seats and the mid portion of said pin; h. said seats and legs of said connector and pin completely encapsulating said chords at their inner and outer faces and edges; i. said connector arm being formed with an edge flange extending a substantial portion therealong and extending transversely of said chord for close fitting engagement therewith for transmitting forces from said strut members to the mid portions of said chords; and j. said chords being formed with channels extending from their outer faces toward their inner faces at the approximate center line of said chords for force fit receipt of said flange of said connector.

2. A truss joist as described in claim 1 comprising: a. said sheet metal connectors comprising a pair of U-shaped members, each having a seat, an upstanding leg formed with an opening for receipt of said pin, an upstanding arm formed with an opening for receipt of said pin and said arms having at least one edge formed with a flange extending a substantial portion therealong and extending transversely of said chord for close fitting engagement therewith.

3. A truss joist as described in claim 2 comprising: a. the leading and trailing edges of said arms being formed with flanges extending a substantial portion thereof and extending transversely of said chord for close fitting engagement therewith.

4. A truss joist as described in claim 1 comprising: a. a cutting tooth formed in leading relationship to each of said flanges for forming a channel in said chord upon being driven into said chord for force fitting occupany by said flange.

5. A truss joist as described in claim 1 comprising: a. said arms and said legs being angularly related to the plane of said seat offsetting said pin from the center line of said seat.

6. A truss joist as described in claim 5 comprising: a. said angle formed between said arms and legs of said connector with said connector seat being about 30*.

7. A truss joist as described in claim 1 comprising: a. a short wood bearing member having substantially the same width and thickness of said upper chord and being similarly slotted and placed beneath the end of said upper chord; b. a second set of said connectors each including a pair of Ushaped members having a seat engaging the outside face of said wood bearing member and said arms and legs connecting said seat and pin.

8. A truss joist as described in claim 1 comprising: a. a second upper and lower wood chords dispOsed in side by side relationship with said upper and lower wood chords; b. a plurality of second connectors mounted on said second chords; c. a plurality of second strut members arranged diagonally between said second chords; d. an elongated pin pivotally securing the ends of both sets of said struts to said connectors.

9. A truss joist comprising: a. upper and lower wood chords; b. a plurality of metal connectors mounted on said chords; c. a plurality of strut members arranged diagonally between said chords; d. means pivotally securing the ends of said struts to said connectors wherein the pivot points are located inwardly of the center lines of each of said chords; e. said means includes a pin mounted transversely of said chords and partially outside the inner surfaces of said chords; f. said chords being formed with a transverse groove for receiving said partially embedded pins. g. said connectors include a seat engaging the outside face of said chords and a pair of legs connecting said seat and said pins and a retaining arm disposed from said legs connecting said seat and said pins; and h. said chords having a width greater than the width of said connectors and being formed with recesses for receiving the ends of said struts, slots for receiving said retaining arms, and end recesses for receiving said connector legs.