US3738690A

US3738690A - Splicable structural member

Info

Publication number: US3738690A
Application number: US00160519A
Authority: US
Inventors: J White
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-07-07
Filing date: 1971-07-07
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12

Abstract

A string of nested, overlapping structural members for supporting strand elements by joining successive members lying in parallel planes. All members are provided with a series of holes for receiving fasteners, each series of holes comprising an outer set and an alternate inner set disposed along laterally spaced centerlines such that the inner holes of an upper member are registrable with the outer holes of an underlying member. In this way, any member may be selected for either disposition to obtain the desired relation within a string.

Description

United States Patent 1 1 White June 12, 1973 SP LI CA BLE STRUCTURAL MEMBER [76] Inventor: James C. White, RC. Box 5496 Station B, Greenville, S.C.

[22] Filed: July 7, 1971 211 App]. No.: 160,519

Related Application Data [63] Continuation of Ser. No. 847,179, Aug. 4, 1969.

' [52] US. CL. 287/l89.3'6 F, 52/732 [51] Int. Cl. Fl6b 7/18 [58] Field of Search 287/189.36'F;

[56] I References Cited UNITED STATES PATENTS 2,990,920 7/1961 Hoffman 287/189.36 F X 3,025,933 3/1962 Comino 287/l89.36 F X 2,632,533 3/1953 MacKenzie 287/189.36 F X 3,003,600 10/1961 MacKenzie 287/189.36 F X 3,025,933 Comino 287/189.36 F

3,250,051 5/1966 Cheris 287/189.36FX

FOREIGN PATENTS OR APPLICATIONS 645,908 3/1964 Belgium 52/633 679,597 2/1964 Canada........ 52/633 1,394,950 11/1965 France 52/633 1,307,721 9/1962 France 52/633 Primary Examiner- David J. Williamowsky Attorney-Newton, Hopkins & Ormsby [57] ABSTRACT A string of nested, overlapping structural members for supporting strand elements by joining successive members lying in parallel planes. All members are provided with a series of holes for receiving fasteners, each series of holes comprising an outer set and an alternate inner set disposed along laterally spaced centerlines such that the inner holes of an upper member are registrable with the outer holes of an underlying member. 1n this way, any member may be selected for either-disposition to obtain the desired relation within a string.

1 Claim, 13 Drawing Figures PAIENIEU BY 77mm, M

ATTORNEY PATTERN X i iZf o INVENTOR- JAMES 0. WHITE BYfl/za/fin,

7/0 7 15 145 flmsby ATTORNEYS SPLICABLE STRUCTURAL MEMBER This application isa continuation of application Ser. No. 847,]79, filed Aug. 4, I969.

BRIEF sUMMARY OF THE INVENTION holes arranged along a centerline offset from the first centerline by an amount such that the first set of holes of one member are registrable with the second set of holes of another member overlapped therewith, and vice versa.

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. 1 is an exploded perspective view showing one form of the invention;

FIG. 2 is a view similar to FIG. 1 but showing the two structural members of the former figure in reverse relat1on;

FIG. 3 is a partial perspective view showing another form of the invention;

FIG. 4 is a view similar to FIG. 3 but showing a modification;

FIG. 5 is an enlarged view illustrating the manner of alignment of the holes in a pair of structural members;

FIG. 6 is an end view illustrating a further embodiment of the invention;

FIG. 7 is an end view showing a still further embodiment of the invention;

FIG. 8 is a further view showing another embodiment of the invention; and

FIG. 9 is an elevational view illustrating a string of structural members.

FIG. 10 is an elevational view similar to FIG. 9 but showing the members disposed in lap strake manner.

FIG. 11 is a fragmentary plan view of a modified form of the present invention.

FIG. 12 is a side elevational view of the angle member shown in FIG. 11.

FIG. 13 is a plan view of still another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION With reference now more particularly to FIGS. 1 and 2, the

reference characters

10 and 12 therein indicate generally a pair of structural members which, in the specific instance shown, are of dissimilar configuration. The member 10 is an angle piece provided with the upstanding leg 14 and a horizontal leg 16 connected together along a common edge 13 and disposed at right angles with respect to each other. Channel member 12 is of a Ushaped configuration, having the

upstanding flanges

18 and 20 interconnected by a web 22.

In FIG. 1, the angle member 10 is to be nested within the channel member 12 and in order to secure these parts together in such relation and also in the relationship shown in FIG. 2 wherein the channel member 12 is to be nested within the angle member 10, the leg 16 of the member 10 and the web 22 of the member 12 are 2 each provided with a series of similarly spaced holes or openings.

Angle member 10 is provided with a first primary set of holes 24 through leg 16 longitudinally spaced from each other along a common centerline 61 parallel to leg l4and spaced therefrom by a convenient distance A as shown in FIGS. 1 and 2. Angle member 10 is also provided with an second primary set of holes 30 through leg 16 longitudinally spaced from each other along a common centerline 63 parallel to centerline 61 and spaced outwardly from centerline 61 by a distance equal to one-half of the sum of the thickness T, of leg 14 of member 10, and the thickness T of flange 18 of channel member 12.

Channel member 12 is provided with a first secondary set of holes 42 through web 22 longitudinally spaced along a common centerline 65 parallel to flange 18 so that when angle member 10 is nesting within channel member 12 so that the outside surface leg 14 is contiguous with the inside surface of flange 18, the holes 24 in leg 16 are registrable with holes 42 in web 22 and centerline 61 is in vertical alignment with cen terline 65. Channel member 12 is also provided with a second secondary set of holes 38 through web 22 longitudinally spaced along a common centerline 67 parallel to centerline 65 and spaced inwardly toward flange l8 therefrom by a distance equal to one-half the sum of the thickness T, of leg 14 of member 10 and the thickness T, of flange 18 of member 12. Thus, when channel member 12 is nesting in angle member 10 as seen in FIG. 2, the holes 38 in member 12 are registrable with holes 30 in member 10 and centerline 67 overlies centerline 63. The longitudinal spacing between holes 24 along centerline 61 or the holes 30 along centerline 63, or the holes 38 along centerline 67, or the holes 42 along centerline 65 may be varied as desired as long as the relative transverse spacing between the

centerlines

61, 63, 65, and 67, remain the same as set forth hereinabove.

A partial top plan view of members 10 and 11 is shown in FIG. 5 with the members nested as shown in FIG. 1. It will be noted that centerline 61 overlies centerline 65 so that

holes

24 and 42 are registrable with each other. It will also be noted that

holes

30 and 38 are in misalignment with each other and

centerlines

63 and 67 are laterally spaced from each other by a distance equal to the sum of thickness T, of leg 14, and thickness T of flange 18. From the above, it will be seen that if thickness T, equals thickness T, then the lateral distance between

centerlines

61 and 63 is equal to T, or T and likewise for the lateral distance between

centerline

65 and 67.

The purpose of this relationship is to allow the

structural members

10 and 12 to be disposed as desired to produce an arrangement such as is shown in FIG. 9. FIG. 9 diagrammatically illustrates the provision of a support assembly to support strand-like elements stretching between two

supports

50 and 52, the support assembly being indicated generally by the reference character 54. Support assembly 54 comprises a string of structural members l0, l2, constructed in accordance with the present invention which present substantially level or flat surface extending between

supports

50 and 52, for receiving the strand-like elements. The string of

structural members

10, 12, show three members 10, within which are nested members 12 in alternate overlapping relationship as shown until the string is of a desired length to stretch between the two supports 50 and 52 as desired. Without the relationship of the staggered

holes

24, 30, 38, and 42 shown in FIGS. 1 and 2, for example, the

structural members

10, 12, could not be overlapped and nested with each other.

It is therefore seen that fasteners, such as the bolt 66 and nut 68 shown in FIGS. 1 and 2, may be received through the registered set of holes, such as a hole 24 and a hole 42 in FIG. 1, or a hole 38 and a hole 30 in FIG. 2, to secure the members and 12 together to form the string 54, as is shown in FIG. 9. It is also to be understood that overlapped or nested members l0, 12 may be extended or retracted in increments equal to the spacing between adjacent longitudinally aligned holes in a set.

FIG. 3 shows a modified structural member 10' which may take the form of angle irons having right angularly disposed legs 70 and 72 each having an inner set of holes 74 in each leg 70, 72, and an outer set of holes 76 in each leg 70, 72. The outer sets of openings 76 are disposed along centerlines 78 spaced from the line of intersection 80 between the inner faces of the two legs 70 and 72 by a fixed and predetermined amount whereas the centerlines 82 of the inner sets of holes 74 are laterally spaced inwardly therefrom by an amount equal, in this case, to the thickness of each leg 70 or 72. Thus, two or more members constructed as is shown in FIG. 3 may be overlapped either way with respect to each other while still achieving alignments of the

holes

74, 76 thereof. The member 10' which is nested within the other will always be arranged such that its inner set of holes 74 are alignable or registrable with the outer set of holes 76 of the other member 10 within which it is nested. In FIG. 3 it will be noted that the sets of holes are arranged such that the inner set of holes 74 of one leg is laterally aligned with the outer set of holes 76 of the other leg. When two members 10' are positioned with respect to each other so that holes 74 of the inside member 10' are in registry with holes 76 in the outside member 10', then appropriate fasteners may be positioned in the registered

holes

74 and 76 in each leg 70 and 72 to lock the members 10 together. Since holes 74 in the leg 70 are longitudinally spaced from the holes 74 in the other leg 72, the fasteners positioned in the registered

holes

74 and 76 will be staggered longitudinally from each other in the legs 70 and 72.

FIG. 4 shows a modified member 10" from that shown in FIG. 3. Member 10 has legs 81 and 83 corresponding to legs 70 and 72 in FIG. 3. Each leg 81 and 83 has an inner set of holes 84 corresponding to the holes 74 in member 10' and an outer set of holes 86 corresponding to holes 76 in member 10'. The holes 84 in leg 81 of member 10" are, however, laterally aligned with holes 84 in leg 83. Likewise holes 86 in leg 81 are laterally aligned with holes 86 in leg 83. Thus when using two members 10" so that holes 84 of the inner member 10" are in registry with holes 86 of the outer member 10", the fasteners inserted through the registered holes in leg 81 will be in lateral alignment with the fasteners inserted through the registered holes in the leg 83.

FIG. 6 shows a further embodiment wherein the two structural members indicated generally by the

reference characters

88 and 90 are ofH-shaped configuration, and each with a central web 91 and oppositely extending flanges 97 along each edge thereof at right angles thereto. The flanges 97 have the same thickness t as indicated and the webs 91 each have a first set of holes 89 aligned along a common longitudinally extending centerline parallel to flanges 97 and a second set of holes 93 aligned along a common longitudinally extending centerline parallel to the centerline of holes 89 and spaced therefrom the distance t. Holes 89 correspond to holes 76 in FIG. 3, and holes 93 correspond to holes 74 in FIG. 3 so that holes 89 in member 88 are registrable with holes 93 in member when member 90 is nested in member 88. Likewise holes 89 in member 90 are registrable with holes 93 in member 88 when member 88 is nested in member 90. The holes 93 in member 90 are shown in registration with holes 89 in member 88 in FIG. 6 and a fastener 92 is passed therethrough.

In FIG. 7, a modified Z-shape configuration as compared with FIG. 6 is shown, the two members being indicated by the reference characters 98 and 100. However, in contrast to FIG. 6 wherein the

holes

89 and 93 are'offset by the thickness t of the flanges 97 of the

members

88 and 90, the offset in FIG. 7 between holes 89' and 93' is equal to the distance T shown therein which represents the lateral offset between the lines of the intersection of the nested faces, substantially as shown.

In the configuration shown in FIG. 8, wherein the two

members

102 and 104 are of different thickness dimensions T and t as shown, the offsets between the centerlines of the inner and outer sets of holes 89" and 93" will be equal to one half of the sum of t T as indicated.

In FIG. 10, it will be seen that, if desired, the structural members may be arranged in lapstrake manner. Specifically, assuming that the left hand of a member, in FIG. 10, which is identified by numeral 200, were considered the proximal end and its other end the distal end, each of the

structural members

200, 201, 202, and 203, would have its distal end overlapping the proximal end of the left adjacent structural member. In other words, the proximal end of structural element 201 would overlap the distal end of structural element 200, etc. The overlapping would be sufficient, of course, to align the registering holes so that they could receive a fastening member (not shown).

In FIGS. 11 and 12, the structural element, denoted by numeral 210 includes angularly

related leg portions

214 and 216. A pattern of two

holes

224 and 230 is established at spaced intervals along the length of leg portion of flange 216. The pitch P of each pattern is, of course, different from the longitudinal distance between

adjacent holes

224 and 230 within the pattern. In like manner, the

holes

274 and 276 are established. These

holes

274 and 276, preferably, but not necessarily, have the same pitch P as the

holes

224, and 230. The lateral spacing t of centerline 261 from centerline 263 of such holes is, as in the preceding embodiments, equal to the thickness of the leg portion 214. Also, the lateral distance between

centerline

278 and 282 is equal to t, i.e., the thickness of leg member 216. It will be noted that the pitch P or the longitudinal distance between

holes

224, 230, 274, and 276, may be varied in any desired manner without departing from the inventive concept.

It is also frequently necessary that the strand-like elements supported in the structural members be attached thereto by known fasteners and clamps which require fastening holes through the structural members. In order to prevent these fastening holes from being blocked when the structural members are overlapped, these fastening holes must be arranged in a pattern with respect to the sets of holes provided in the structural members used to fasten the structural members together. FIG. 13 shows such an arrangement for an angle member 310 having a leg 314. Two patterns X and Y of holes are provided in leg 314. The holes in pattern X are referenced 324a, 324b, and 324C, and the holes in pattern Y are referenced 330a, 330b, and 330C.

Holes

330a and 324a correspond to

holes

30 and 24 in member and are arranged along centerlines spaced laterally apart by the distance t which is the thickness of leg 316. Holes 324b and 3240 are fastening holes and can be arranged with respect to hole 324a in any desired manner. The particular arrangement selected, however, must remain the same in each repeated pattern X. Likewise, holes 330b and 330c have a fixed relationship with each hole 330 a in each pattern Y corresponding to the relationship between holes 3241; and 324c and hole 324a. Specifically, pattern X is repeated 3 times, then pattern Y repeated 3 times, and then pattern X repeated 3 more times. It will be noted that the number of times patterns X and Y are repeated between alternations or the spacing between each pattern can be varied as desired as long as the relationship in each pattern is unchanged and the lateral spacing t between

holes

324a and 330a is unchanged and still have

holes

324a, 324b and 3240 of one member in registry with holes 330a, 330b, and 3300 respectively of the other member to make a support assembly. It is therefore seen, if desired, a group or pattern of holes may replace a single hole depicted in FIGS. 1 4 for example.

From the foregoing description and, particularly with reference to FIGS. 1 and 2, it will be understood that by the provision of the registering holes, such as

holes

24 and 42 in FIG. 1, or holes 30 and 38 in FIG. 2, a cylindrical bolt, such as bolt 66 provided with a bearing surface of approximately 360 for the shank may be placed through such holes. Furthermore the inner surface of the head of bolt 66 and the inner surface of the nut 68 are provided with 360 of peripheral bearing surface on the

structural members

10 and 12 for clamping the

structural members

10 and 12 together.

What is claimed is:

1. An assembly of structural members comprising at least a pair of members each having adjacent leg portions disposed in angular relation,

said leg portions of each member presenting intersecting inner faces and one member being nestable within the other member and vice versa whereby the outer face of one leg of said one member is in contiguous relation to the inner face of a leg of the other member,

at least the one leg of said one member and the underlying leg of the other member being provided with a series of longitudinally spaced holes comprised of a first set of holes and an alternate second like set of holes, the holes of the first set in each member being identical in size and shape with those of the second set in the other member, the two sets of holes being spaced along centerlines parallel to said other face of the corresponding member and which centerlines are spaced laterally by an amount such that the first set of holes of said one member are registrable with and superposed with respect to the second set of holes of said other member when said one member is nested within said other member and the second set of holes of said one member is registrable with and superposed with respect to the first set of holes of said other member when said other member is nested within said one member.

2. A preformed member for use in the construction of structural framework comprising: a predetermined shaped structural member, said member having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line, there being provided at least two openings defined in at least one of said portions, and one of said openings being located a predetermined distance measured from one of said intersec tion lines and said other opening being located a distance from said other intersection line equal to said predetermined distance, whereby said preformed member can be operatively connected in longitudinally aligned relationship to a similar preformed member by overlapping said surface portions in nested relationship and to an extent to selectively align said one opening of said preformed member with said other opening of said similar member when said similar member is nested within said preformed member and to align said other opening of said preformed member with said one opening of said similar member when said preformed member is nested in said similar member, each of said angularly oriented portions being provided with at least two openings with each of said openings being detailed in location a measured distance from said intersecting lines respectively; said two openings in each of said angularly oriented portions being longitudinally spaced along said angular portions with said openings in each of said angular portions being in transverse aligned relationship, and said transversely aligned opening being equally spaced relative to said intersecting lines.

3. A preformed structural member as defined in claim 2 wherein said transversely aligned opening of one angular portion is located a predetermined measured distance from one of said intersection lines and wherein said other transversely aligned opening is located an equal measured distance from said other intersecting line.

4. A preformed member for use in the construction of structural framework comprising: a predetermined shaped structural member, said member having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line, there being provided atleast two openings defined in at least one of said portions, and wherein one of said openings is located a predetermined distance measured from one of said intersection lines and said other opening is located a distance from said other intersection line equal to said predetermined distance, whereby said preformed member can be operatively connected in longitudinally aligned relationship to a similar preformed member by overlapping said surface portions in nested relationship to an extent to selectively align said one opening of said preformed member with said other opening of said similar member when said similar member is nested within said preformed member and to align said other opening of said preformed member with said one opening of said similar member when said preformed member is nested in said similar member, said angularly oriented member being provided with at least two patterns of longitudinally spaced openings, each pattern of longitudinally spaced openings including a series of openings with the openings of each pattern detailed in a measured location from said intersecting lines and said series of openings in said second pattern being transversely spaced relative to the openings of said first pattern.

5. A preformed member for use in the construction of structural framework comprising: a predetermined shaped structural member said member having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line there being provided at least two longitudinally spaced openings defined in at least one of said portions, each of said openings having a central axis and being symmetrical in shape with respect to said axis, one of said openings being located a predetermined distance from one of said intersection lines and the other said openings being located a distance from said other intersection line equal to said predetermined distance, whereby said preformed member can be operatively connected in longitudinally aligned relationship to a similar preformed member by overlapping said surface portions in nested relationship to an extent to selectively align said one opening of said preformed member with said other opening of said similar member when said similar member is nested within said preformed member and to align said other opening of said preformed member with said one opening of said similar member when said preformed member is nested in said similar member.

6. A preformed member as in claim wherein said openings are circular in shape.

7. In a preformed member as described in claim 5 further characterized in that each of said angular oriented portions is provided with at least two openings, with each of said openings being detailed in location a measured distance from said intersecting lines, respectively. I

8. In a preformed member as described in claim 5 further characterized in that at least one of said angular oriented portions is provided with at least two patterns of openings, with each pattern of said opening including a series of longitudinally spaced openings, with each opening of said pattern detailed in location said measured distance from one of said intersecting lines and wherein said series of openings of said second pattern is longitudinally spaced relative to said first pattern along said angular oriented portion and with each opening of said second pattern detailed in a measured distance from said intersecting line, corresponding to the measured distances of said first pattern.

9. An improved structural framework comprising: a. a series of preformed structural members, each of said members having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line, there being provided at least two longitudinally spaced openings defined in one of said portions, each of said openings having a central axis and being symmetrical with respect to said axis, one of said openings being located a predetermined distance from one of said intersection lines and the other opening being located a distance from said other intersection line equal to said predetermined distance, and b. means connecting said series of preformed structural members in nested and longitudinally aligned relationship said preformed members being selectively connectable with the inner surface of a first preformed member nested in juxtaposition with the outer surface of a second preformed member and with the outer surface of said second preformed member nested in juxtaposition with the inner surface of a third preformed member, and wherein said connecting means extends through aligned openings in said nested preformed members. 7

10. A structural framework as in claim 9 wherein said openings are circular in shape.

Claims

1. An assembly of structural members comprising at least a pair of members each having adjacent leg portions disposed in angular relation, said leg portions of each member presenting intersecting inner faces and one member being nestable within the other member and vice versa whereby the outer face of one leg of said one member is in contiguous relation to the inner face of a leg of the other member, at least the one leg of said one member and the underlying leg of the other member being provided with a series of longitudinally spaced holes comprised of a first set of holes and an alternate second like set of holes, the holes of the first set in each member being identical in size and shape with those of the second set in the other member, the two sets of holes being spaced along centerlines parallel to said other face of the corresponding member and which centerlines are spaced laterally by an amount such that the first set of holes of said one member are registrable with and superposed with respect to the second set of holes of said other member when said one member is nested within said other member and the second set of holes of said one member is registrable with and superposed with respect to the first set of holes of said other member when said other member is nested within said one member.

2. A preformed member for use in the construction of structural framework comprising: a predetermined shaped structural member, said member having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line, there being provided at least two openings defined in at least one of said portions, and one of said openings being located a predetermined distance measured from one of said intersection lines and said other opening being located a distance from said other intersection line equal to said predetermined distance, whereby said preformed member can be operatively connected in longitudinally aligned relationship to a similar preformed member by overlapping said surface portions in nested relationship and to an extent to selectively align said one opening of said preformed member with said other opening of said similar member when said similar member is nested within said preformed member and to align said other opening of said preformed member with said one opEning of said similar member when said preformed member is nested in said similar member, each of said angularly oriented portions being provided with at least two openings with each of said openings being detailed in location a measured distance from said intersecting lines respectively; said two openings in each of said angularly oriented portions being longitudinally spaced along said angular portions with said openings in each of said angular portions being in transverse aligned relationship, and said transversely aligned opening being equally spaced relative to said intersecting lines.

4. A preformed member for use in the construction of structural framework comprising: a predetermined shaped structural member, said member having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line, there being provided at least two openings defined in at least one of said portions, and wherein one of said openings is located a predetermined distance measured from one of said intersection lines and said other opening is located a distance from said other intersection line equal to said predetermined distance, whereby said preformed member can be operatively connected in longitudinally aligned relationship to a similar preformed member by overlapping said surface portions in nested relationship to an extent to selectively align said one opening of said preformed member with said other opening of said similar member when said similar member is nested within said preformed member and to align said other opening of said preformed member with said one opening of said similar member when said preformed member is nested in said similar member, said angularly oriented member being provided with at least two patterns of longitudinally spaced openings, each pattern of longitudinally spaced openings including a series of openings with the openings of each pattern detailed in a measured location from said intersecting lines and said series of openings in said second pattern being transversely spaced relative to the openings of said first pattern.

6. A preformed member as in claim 5 wherein said openings are ciRcular in shape.

7. In a preformed member as described in claim 5 further characterized in that each of said angular oriented portions is provided with at least two openings, with each of said openings being detailed in location a measured distance from said intersecting lines, respectively.

9. An improved structural framework comprising: a. a series of preformed structural members, each of said members having first and second portions angularly oriented relative to each other, each of said portions including inner and outer surfaces with the planes of said inner surfaces intersecting at a first line and with the planes of said outer surfaces intersecting at a second line, there being provided at least two longitudinally spaced openings defined in one of said portions, each of said openings having a central axis and being symmetrical with respect to said axis, one of said openings being located a predetermined distance from one of said intersection lines and the other opening being located a distance from said other intersection line equal to said predetermined distance, and b. means connecting said series of preformed structural members in nested and longitudinally aligned relationship said preformed members being selectively connectable with the inner surface of a first preformed member nested in juxtaposition with the outer surface of a second preformed member and with the outer surface of said second preformed member nested in juxtaposition with the inner surface of a third preformed member, and wherein said connecting means extends through aligned openings in said nested preformed members.