US3477189A

US3477189A - Load supporting structure

Info

Publication number: US3477189A
Application number: US617201A
Authority: US
Inventors: Karol J W Merson
Original assignee: Anthes Imperial Ltd
Current assignee: Anthes Imperial Ltd
Priority date: 1967-02-20
Filing date: 1967-02-20
Publication date: 1969-11-11
Anticipated expiration: 1986-11-11
Also published as: GB1175711A

Description

K. J..w. MERSON 3,477,189 1 LOAD SUPPORTING STRUCTURE Nov. ll',.1969

s Sheets-Sheet 1 Filed Feb. 20, 19s".

INVENTOR. KAROL J. w. MERSON ATTORNEYS 1969 K. J- w.' MERSON 3,477,189

} LOAD SUPPORTING STRUCTURE I Filed Feb. 20, 1967 I 3 Sheets-Sheet 2 INVENTOR. KAROL J. W. MERSON ATTORNEYS United States Patent M 3,477,189 LOAD SUPPORTING STRUCTURE Karol J. W. Merson, Toronto, Ontario, Canada, assignor to Anthes Imperial Limited Filed Feb. 20, 1967, Ser. No. 617,201 Int. Cl. E0411 12/10; E04c 3/04; E04!) 5/14 U.S. Cl. 52-648 8 Claims ABSTRACT OF THE DISCLOSURE This invention consists of a load supporting structure primarily intended for ceiling or floor structures. The load supporting structure of the invention is formed of interlocking trusses arranged in two series with the trusses of one series extending at an angle to the trusses in the second series. To provide for interlocking of the trusses, the top chord members of the first series trusses are provided with regularly spaced openings whereby the second series trusses may be dropped through the openings to rest on the bottom chord members of the first series trusses. The top chord of the two series trusses are then connected together.

This invention relates to the manufacture of load supporting structures and is particularly concerned with a two-way system of interlocking trusses for floor or ceiling structures capable of spanning large areas with minimum support.

The two-way truss structure described herein is primarily intended as a supporting structure for ceilings and/ or floors but it should be understood that it is equally adapted to use in other planar structures which require strength to resist forces directed at right angles to the plane of the structure. Thus, for example, the structure of the invention may be used to form a wall which might be subjected to extreme wind forces. For purposes of illustrating the invention, however, it is described in the form of a roof or ceiling supporting structure.

The traditional truss structure for providing floor and ceiling support in buildings employs a series of parallel trusses supported at their ends by columns or walls. Thus, the dimension of unobstructed floor area taken parallel to the trusses is limited to the distance between the walls or columns and can only be increased by using trusses of heavier construction. Many attempts have been made in the past and are still being made to increase the span possible, with one of the more recent attempts employing space frame structures which are characterized by triangular shaped members coupled together as to form a planar structure or a dome. While space frame systems are capable of providing large unobstructed floor areas, they are costly to erect due to the considerable amount of on the site labour costs involved in interconnecting the large number of structural units which make up the final structure. Further, space frame structures suffer the disadvantages that as the individual structural units are essentially three dimensional, they are bulky and, hence, difficult and expensive to store and ship.

It is, therefore, an object of this invention to provide an economic load supporting structure which is capable of covering a large area without intermediate support.

It is a further object of the invention to provide a method of erecting the load supporting structure of the invention which provides economies in time and labour costs and can be carried out in greater safety than those traditional methods of erecting similar structures known heretofore where most of the labour involved is carried out by workmen positioned above floor level.

It is a more specific object of the invention to provide a load supporting structure which is characterized by 3,477,189 Patented Nov. 11, 1969 a system of interconnected trusses which provide mutual support whereby it is possible to cover a larger unobstructed floor area than can be done by using trusses of similar weight and size arranged in one of the conventional ways.

It is a further specific and related object of the invention to provide a method of erecting a ceiling structure which involves interconnection of the trusses forming the structure at floor level with subsequent en masse raising of the structure to ceiling level, which method has the advantage that as construction takes place at floor level, it can be carried out more quickly and efticiently and with greater safety than can the conventional erecting procedures which require most of the work to be carried out by workmen above fioor level.

It is a further specific object of the invention to provide a load supporting structure which is better adapted to support point or concentrated loads such as overhead cranes and the like than are those structures known heretofore which essentially consist of a single series of parallel trusses.

It is a still further object of the invention to provide a load supporting structure which is build up from a plurality of elongated, substantially flat, structural units whereby to avoid the shipping and storing problems associated with the use of three-dimensional structural units such as those employed in constructing space frame structures.

The above and further objects of the invention will be more thoroughly understood by reference to the following detailed description of two preferred embodiments thereof as taken in conjunction with the accompanying drawings.

In the drawings,

FIGURE 1 is an overall perspective view of a load supporting structure in accord with a first embodiment of the invention as it might be employed in a ceiling;

FIGURE 2 is an enlarged perspective view of a portion of the load supporting structure shown in FIGURE 1 and illustrating in greater detail the manner in which the trusses forming the structure are interconnected;

FIGURE 3 is a perspective view of portions of the trusses at one connecting point and illustrating the manner in which they are moved into position for connection;

FIGURE 4 is a vertical cross-sectional view taken along the line 44 of FIGURE 2 but illustrating an alternative form of connection;

FIGURES 5, 6 and 7 are side elevation views of a modified form of truss for forming a load supporting structure in accord with a second embodiment of the invention and further showing the manner in which a second transverse truss is received therein when forming the structures; and

FIGURE 8 is a perspective view, similar to FIGURE 2, and showing a portion of the load supporting structure in accord with the second embodiment thereof.

Referring to FIGURE 1, the structure 10 of the invention is made up of two series of trusses arranged at right angles to one another as to form a grid. The structure is supported only about its side edges by vertical post members 12 and there are no intermediate supports interfering with the space covered by the grid. While the illustrated grid has trusses arranged at right angles, it should be understood that the angle between the two series may be other than without departing from the scope of the invention.

The trusses making up a grid in accordance with the first embodiment of the invention are illustrated in greater detail in FIGURE 2. They consist of a pair of spaced chords interconnected by a web. In the illustrated case, the web is of the open type but it should be understood that the structure of the invention can be formed of closed web trusses such as standard I beams. Further, the particular trusses shown in the drawings employ chords which are formed of sheet steel by hot or cold roll forming while the web members are formed of tubular steel but again, the invention need not be limited to trusses of this specific construction. In all cases, however, one of the chords of the trusses of one series is a continuous member while the trusses of the other series are manufactured in the original instance with one of the chords having regularly spaced openings. In constructing the grid the latter trusses, i.e. the type having openings in one of their chords, are placed in position first and for this reason they are referred to hereinafter as the primary trusses while the other type are referred to as the secondary trusses. In FIGURE 2, there is shown two primary trusses and one secondary truss. The illustrated secondary truss includes an upper chord 14 and a lower chord 16 and an interconnecting web 18. The overall vertical height of the secondary truss is somewhat less than the height of the primary trusses so that when its lower chord 16 is laid on the bottom chord 19 of the primary trusses, as is explained hereinafter, the top chords in both series are aligned.

As previously mentioned, the primary trusses are characterized by the feature wherein one of the chords has regularly spaced openings as they are originally manufactured whereby the secondary trusses may be dropped down into the primary trusses as to interlock therewith. The primary trusses of the first embodiment are also characterized by additional vertically extending web members 22 arranged one on either side of the vertical planes in which the secondary trusses are eventually arranged.

At the points of interlock, the top chords of both types of trusses are provided with suitable joining elements which can best be seen in FIGURE 3. The particular joining elements illustrated consist of plates 24 welded to the top chords 20 of the primary trusses on either side of the openings and mating plates 26 welded to the side edges of the top chords 14 of the secondary trusses. As a preferred expedient, the latter two plates are connected by a transverse plate 28 welded to them and to the bottom surface of the top chord member 14. With the addition of the transverse plate 28, the portions of the webs which would normally be welded to the under side of the top chords themselves are welded to the plates 28. Both the

plates

24 and 26 are provided with

mating holes

30 and 32, respectively, through which interconnecting bolts 34 may be passed as to hold the structure together. When the top chords are in compression, as would most often be the case, and is the case in the particular grid shown in FIGURE 1, these bolts do not actually carry a load and need not be of particularly heavy construction. On the other hand, where the top chords are in tension such as would be the case in the extended portions of the grid if the grid of FIG- URE 1, for example, was dimensioned to over-hand the support posts 12, the bolts 34 must be capable of withstanding the design tension stresses.

An alternative joining arrangement is illustrated in FIGURE 4. This particular arrangement differs from the arrangement shown in FIGURES 2 and 3 in that the

plates

26 and 28 are combined in a single cast or forged item. Further, an extra plate 36 is arranged on the upper side of the top chords 14 and eventually welded to the plate 24 as to provide additional compression resisting strength to the top chords 20 of the primary trusses.

One of the great advantages of the grid structure of the invention is the manner in which it can be easily and quickly assembled. Thus, the procedure in placing the grid structure of the first embodiment of the invention is to first lay the first series of primary trusses on the floor of the space which is eventually to be covered by the grid. These trusses are placed parallel to one another and regularly spaced with the openings in the top chords 20 facing upwardly. Then the secondary trusses are simply dropped into the primary trusses through these openings until the bottom chords of the secondary trusses rest upon the bottom chords of the primary trusses. Then the bolts 34 and associated nuts are slipped into position and the complete grid structure can then be raised en masse onto the supporting posts 12. In placing a conventional grid consisting solely of trusses running in one direction, it is necessary to mount each truss indivdually and in this case the workmen are working at a height whereas in assembling the grid structure of the invention, the workmen do the assembly on the floor. This procedure has advantages in time-saving, thoroughness of the assembly and safety.

In addition to the advantages gained by ease of assembly, the structure itself has a very great advantage in that it is capable of spanning a much larger area than are conventional truss structures characterized by trusses of equivalent size running in one direction only. Further, due to the use of trusses running in two directions, the structure is better adapted to support concentrated loads. This advantage is particularly apparent when a travelling crane is supported by the structure. The constantly changing locale of the concentrated load can be easily accommodated and should it be desired to relocate the general locale of the crane, no modification of the structure is required.

It was previously mentioned that any type of truss might be modified to adapt same to use in a grid structure of the invention. From the foregoing specification, it will be appreciated that the modifications required are (1) the manufacture of a plurality of secondary trusses which are smaller in height relative to the primary trusses by the depth of the bottom chords of the latter; (2) the provision of openings in the top chords in the primary trusses; and (3) the provision of means for interlocking the top chord of the two series of trusses after the secondary trusses have been dropped into the primary trusses. A modification which may or may not be required, depending upon the particular type of truss used, is the further provision of web strengthening elements in the primary trusses adjacent the points where they are interlocked with the secondary trusses. In the illustrated form of the first embodiment of the invention, these latter auxiliary web strengthening members are the items 22.

The load supporting structure of the second embodiment of the invention does not differ from the first in any major respect but only in certain structural details in the individual trusses. These modifications dictate a somewhat different grid assembly technique but have certain advantages with respect to handling of the individual trusses during shipping.

In handling the primary trusses of the first embodiment, it has been found that the openings in the top chords tend to make these trusses somewhat too flexible as the only continuous longitudinal members are the bottom chords. In accord with the second embodiment of the invention, this problem is overcome by rearranging the web components in the primary trusses in the manner shown in FIGURE 5. Here, the upper ends of the diagonal web components are welded to the undersides of the transverse plates 28 while the lower ends of these diagonals are merely tack-welded to the bottom chords 19. Further, the plates 28 are welded to the plates 26 as to form U-shaped elements which are temporarily bolted to the plates 24. It will be appreciated, therefore, that the plates 26 are not, in the first instance, fixed to the top chords of the secondary trusses, as is done in the case of the first embodiment. With the relocation of the diagonal web components, as above mentioned, the primary trusses of the second embodiment are further modified by relocating the vertical components to positions half-way between the vertical planes in which the secondary trusses are eventually positioned.

The primary trusses of the second embodiment, as above described, and as shown in FIGURE 5 can be better handled than the first embodiment trusses as both the top and bottom chords are continuous members during storage and shipping. In building up the grid with these modified trusses, they are first laid parallel to and spaced from one another as is done in the case of the first embodiment. Then, the web units fixed to the underside of the U-shaped elements formed of

plates

26 and 28 are broken away from the secondary trusses by removing bolts 34 and breaking the tack-welds holding the diagonal web components to the bottom chords. The resultant appearance of the primary trusses is shown in FIGURE 6. The same web units are removed from each of the primary trusses so as to provide aligned openings in all the primary trusses sufficient to receive one secondary truss at a time. After each secondary truss is dropped into position, as shown in FIGURE 7, the removed web units are refitted in the primary trusses so that there is no more than one web unit removed from any primary truss at any one time.

In refitting the web units, it is only required to manipulate them to a position where the plates 26 can he slipped into the space between the plates 24 and the top chord of the received primary truss. Then the bolts 34 are permanently fixed in place and the lower ends of'the diagonal web members of the primary trusses are permanently welded to the bottom chords thereof.

Certain modifications to the secondary trusses are also required in employing the construction technique of the second embodiment of the invention. These modifications can be seen in FIGURE 8 and consist to relocating the diagonal web components so that they will not interfere with the reinstallation of the web units of the primary trusses. This relocation simply comprises in shifting these diagonals so that their upper ends meet the undersides of the top chords half-way between the points of interlock with the primary trusses. This, in turn, requires welding these upper ends of the diagonals to the top chords themselves rather than to the underside of the plates 28 as is done in the case of the first embodiment.

It should also be noted that following the dropping of a secondary truss into the primary trusses and replacement of web units in the latter, it is preferable to {weld the top chord to the plates 26 and as a further preferred expedient, the bottom chords of the secondary trusses are welded to the top surfaces of the bottom chords of the primary trusses. Further, the alternative of using the extra plates 36 fixed to the top surfaces of the top chords of the secondary trusses, as mentioned in the description of the first embodiment, is also possible in the case of the second embodiment.

As will be appreciated from the foregoing, While the load supoprting structure of the second embodiment differs from the first in details of construction of the individual trusses, and in the technique of interlocking the trusses, the same basic principles are found in both embodiments, i.e., the principle of providing openings in the top chords of the primary trusses and forming the secondary trusses of a height which differs from the height of the primary trusses by the depth of the bottom chords of the latter. It is these principles which permit the formation of two-way load supporting structures in a practical and economic manner.

What I claim as my invention is:

1. A load supporting structure comprising a grid of interconnected trusses in which each of said trusses includes a pair of vertically spaced chords and an intervening web, said structure including a first series of primary trusses arranged parallel to and spaced from one another, the bottom chords of said primary trusses being continuous members, the top chords of said primary trusses having a plurality of longitudinally and regularly spaced openings, and a second series of secondary trusses arranged parallel to and spaced from one another but extending at an angle to the trusses in said first series, both chords of said secondary trusses being continuous members, said secondary trusses having a height which is less than the height of said primary trusses by an amount equal to the depth of the bottom chords of said primary trusses; the webs of said primary trusses having openings which are vertically aligned with the openings in the top chords of said primary trusses, said chord and web openings of said primary trusses having received thereon said secondary trusses, and means interconnecting the top chords of said primary and secondary trusses where the latter are received in the openings of the former, the bot tom chords of said secondary trusses resting on the bottom chords of said primary trusses.

2. A load supporting structure as claimed in claim 1 wherein said means interconnecting said opening containing chords and said chords received therein comprise plate elements fixed to said primary truss chords and extending transverse thereto on either side of said openings and plate elements fixed to either side of said secondary truss chords and extending parallel thereto whereby the secondary truss plate elements abut the primary truss plate elements, and further including aligned apertures in said plate elements having fastening members received therein and holding said plate elements in abutting relationship.

3. A load supporting structure as claimed in claim 2 further including additional plate elements fixed to the web side of the chords of said secondary trusses, said additional plate elements also being fixed to extended portions of the plate elements fixed to either side of the chords of said secondary trusses.

4. A load supporting structure as claimed in claim 3 wherein the webs of said secondary trusses include diagonal elements fixed to said additional plate elements.

5. A load supporting structure as claimed in claim 1 wherein said trusses are of the open web type and said means interconnecting said opening containing chords and said chords received therein comprise U-shaped elements having the undersides of the bases thereof fixed to diagonal members of the webs of said primary trusses and the arms thereof fixed to plate elements fixed to said primary truss top chords and extending transverse thereto on either side of said openings, the chords of said secondary trusses being positioned between the arms of said U-shaped elements.

*6. A load supporting structure as claimed in claim 3 wherein said additional plate elements and the plate elements fixed to either side of the chords of the secondary trusses are formed as an integral unit.

7. A load supporting structure as claimed in claim 6 including further additional plate elements fixed to the faces of said secondary truss chords directed away from the web thereof and also fixed to extended portions of the plate elements carried by the chords of said primary trusses.

8. A method of prefabricating, transporting and finally constructing a grid of interconnected trusses comprising the steps of forming a plurality of primary trusses, each having a top chord, a bottom chord and an intervening open web, providing longitudinally and regularly spaced openings in the top chords of said primary trusses, fixing bolting plates to said primary truss top chords and extending transverse thereto on either side of said openings, temporarily bolting U-shaped brackets to and between said bolting plates, said brackets carrying diagonal web elements, tack welding the lower ends of said web elements to the top surface of the bottom chords of said primary trusses, forming a plurality of secondary trusses each having a continuous top chord, a continuous bottom chord and an intervening open web, and a dimension taken parallel to the plane of the web thereof and transverse to said chords which is shorter than the like dimension in said primary trusses by the depth of the bottom chord of said primary trusses; transporting said trusses to a job site, laying said primary trusses on a floor parallel to but spaced from one another, removing said U-shaped brackets while simultaneously breaking said tack Welds, dropping said secondary trusses through the openings in the top chords of said primary trusses until the bottom chords of the secondary trusses rest on the bottom chords of the primary trusses, rebolting said U-shaped brackets to and between said bolting plates, permanently welding the diagonal web members carried by said U-shaped brackets to the bottom chords of said primary trusses, and welding said U-shaped brackets to the top chords of said secondary trusses.

References Cited UNITED STATES PATENTS 2,384,409 9/1945 Watter 52650 3,175,650 3/1955 Hartford et a1 52646 3,296,767 1/1967 Lebowitz 52-648 XR FOREIGN PATENTS 617,745 2/1961 Italy.

10 FRANK L. ABBOTT, Primary Examiner JAMES L. RIDGILL, JR., Assistant Examiner US. Cl. X.R. 29155, 469; 52-665, 692, 745