GB2328696A

GB2328696A - Module for a space structure

Info

Publication number: GB2328696A
Application number: GB9817785A
Authority: GB
Inventors: Olivier Baverel
Original assignee: Coventry University
Current assignee: Coventry University
Priority date: 1997-08-15
Filing date: 1998-08-17
Publication date: 1999-03-03
Also published as: GB9817785D0

Abstract

A module (10) for a space structure (28) comprises three elongate members (12a, 12b, 12c), each member having a first free end (14a, 14b, 14c) and a second end (16a, 16b, 16c) connected at or adjacent said second end to one other of said members intermediate (18a, 18b, 18c) the ends of said one other member, thereby to form a triangle (26). The external angle formed at each junction between the members may be approximately 120 so that an approximately equilateral triangle (26) is formed. The preferred module is assembled with other similar modules to form a space structure of an equilateral hexagon grid. The grid may define a portion of the surface of a cone (figures 8b, 9b, 10b) and may be assembled with other such cones linked by structural joints formed by a plurality of modules of non-triangular polygonal, preferably parallelogram form. The interconnection of only two members at each joint (18a, 18b, 18c) enables simple joints to be used, in contrast to those used in for example geodesic structures where a large plurality of members may meet at each joint.

Description

Module for a Space Structure and a Space Structure The invention relates to a module for a space structure and to a space structure.

The geometries of the geodesic and tensegrities structures and their behaviour are well known. A problem with a standard geodesic structure is that the joints of the structure connect between six and twelve elements, so that the joints are complex and the jointing of the elements is expensive. Additionally, a variety of lengths of elements is used which results in a complex construction. The weakest part of such geodesic and tensegrities structures occurs at the joints, so that this is a limiting feature of the construction.

The present invention seeks to provide an improved module for a space structure and an improved space structure.

According to a first aspect of the present invention, there is provided a module for a space structure, the module comprising three or more elongate members: wherein each member has a first, free end and a second end connected at or adjacent said second end to one other of said members intermediate the ends of said one other member, thereby to form a triangle.

According to a second aspect of the present invention, there is provided a space structure comprising a plurality of modules as defined in the immediately preceding paragraph wherein the free end of each said member is connected to a furthermember of a like module intermediate the ends of said further member thereby to form said space structure.

According to a third aspect of the present invention, there is provided a module for a space structure, the module comprising at least three elongate members interconnected with one another by way of a plurality ofjoints; and wherein each said joint comprises an interconnection of only two of said members.

According to a fourth aspect of the present invention, there is provided a module for a space structure, the module comprising at least three elongate members interconnected with one another by way of a plurality ofjoints thereby to form a polygonal structure; and wherein each said joint comprises an interconnection of only two of said members.

The polygon formed by the module may be regular or irregular.

According to a fifth aspect of the present invention, there is provided a space structure comprising a plurality of modules as defined according to the fourth aspect of the present invention wherein each said member of each module is connected to a further member of a like module by way of a further said joint.

Further the invention provides a space structure comprising a plurality of elongate members wherein at least one end of each member is connected to another said member intermediate the ends of said other member so that a triangle is formed between the three interconnected members.

Preferably, the elongate members are ofsubstantially equal lengths. This gives the advantage of ease of manufacture and construction of the structure.

The formation of polygons, such as triangles, from the joining of the elongate members ensures that the space structure has a secure, rigid structure.

The external angle formed between members at a joint may be 10 to 1700 or preferably between 90" and 1500.

In a preferred form ofmodule three members are provided and the external angle formed at each junction between the members is approximately 1200 so that an approximately equilateral triangle is formed. For example, where it is desired to produce a space structure of an equilateral hexagon grid, the external angle between two elements will be 1200.

The present invention is further described hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure la is a diagrammatic representation of a first preferred form of module according to the present invention for a space structure; Figure ib is a representation of a part of a space structure comprising a plurality of modules of Figure la; Figure 2a is a perspective view of a practical 3-dimensional form of the module of Figure la according to the present invention for a space structure; Figure 2b is a representation of a part of a space structure comprising a plurality of modules of Figure 2a; Figure 3 is a second form of module for a space structure; Figure 4 is a representation of part of a space structure comprising a plurality of modules of Figure 3; and Figures 5 to 19 show examples of structures according to the invention.

Refening firstly to Figure 1 a, this illustrates a preferred form ofmodule 10 comprising three elongate members 12a, 12b, 12c which are conveniently rigidly connected to one another.

Each of these members has a first, free end 14a, 14b, 14c. Each member has a second end 16a, 16b, 16c which is connected to one of the other members at a position intermediate the ends ofthe other member. It will be appreciated that each member may be connected at a point adjacent to its end (rather than at its end) to one of the other members. The second end ofmember 1 2a connects with member 1 2b at a position 1 8b intermediate the ends of member 12b. The second end of member 1 2b connects with member 1 2c at a position 1 8c intermediate the ends of member 12c. The second end of member 12c connects with member 1 2a at a position 1 8a intermediate the ends of member 1 2a The result is a polygon in the form of a triangle formed by the members 12a, 12b, 12c with the sides of the triangle extended.

Each of the external angles al, a2, a3 formed by the connections of the elongate members is preferably 1200, as a result of which the triangle formed by the connection of the three elongate members is an equilateral triangle 26. It will be appreciated that the external and internal angles may be varied, as illustrated below.

In Figure 1 a L is the length ofeach elongate member and X is the length of the triangle sides.

In Figure ib, a part of a space structure 28 is shown which is composed of plurality of modules of Figure la. The free end of each module is connected to a further member of a like module intermediate the ends of the further member. By connecting a plurality of members in this manner, the space structure is formed, in which the members combine in a plurality of equilateral hexagons 30.

The arrangement shown in Figure 1b will be generally flat where the members 12a, 12b and 1 2c abut one another. However, by arranging the members as shown in Figure 2a with each member lying on top of the adjacent member, a three-dimensional shape can be given to the module. Interconnecting a number ofmodules ofthe form shown in Figure 2a can then result in a structure which has a curved surface such as shown in Figure 2b where the structure is generally of a part cylindrical shape.

Each member lying on top of the adjacent member at the point of connection introduces an eccentricity in the connection which may be added to by the thickness of any connector used.

The eccentricity may also be reduced be suitable shaping of the members at the point of interconnection.

The modules of Figure 2a can be used to generate a relatively flat surface by inverting adjacent modules.

The members shown in Figure 2a are generally of circular cross-section. However, any suitable cross-section or shape may be used. Examples are rectangular, elliptical and oval.

Members of different cross-sectional shapes may be mixed in a module and adjacent modules may have members of different cross-sectional shapes. For example, one module may have members ofa circular cross-sectional shape whilst an adjacent, connected module might have members of oval or rectangular cross-sectional shape.

Figure 3 shows a module 32 similar to that of Figure la comprising three elongate members 34a, 34b, 34c interconnected at positions 38a, 38b, 38c. In the embodiment shown in Figure 3 the external angles ss" ss, p3 between the elongate members are not all equal. The angle ss is 135 , the angle 92 is 90 , and the angle ss3 is 135".

As can be seen from Figure 3, because the external angles ofthe triangle are not all identical, the sides have different lengths Al and 12.

Figure 4 shows a space structure 40 formed from modules as shown in Figure 3. The free end of each elongate member is connected to a further member of a like module intermediate the ends of the further member so that the space structure is formed. The interconnected triangle modules produce a larger structure of octagons 42, and squares 44.

It will be appreciated that the internal and external angles ofthe triangle of each module may be varied to provide different resulting space structures. Each of the external angles of the triangles may have a value in the range 10 to 1700 or 90" to 1500, depending on the ratio of the length L of each elongate member to its diameter D. The range of the external angles a of the module may be proportional to the ratio L/D.

The space structure as shown in Figures Ib and 4 and other space structures formed from other modules which fall within the scope of the present invention may be formed without first forming the modules. A plurality of elongate members may be connected to one another in situ as the structure is constructed so that the triangles of the modules are formed in situ.

When construction is carried out in this manner the angles between elongated members have to be set to the required value.

Using the hexagon grid of Figure 1b or Figure 4, a half cone structure can be created. This is effected by using several different values of 1 with different LID ratios. Only a few different values of 1 with different L/D ratios are needed to generate an exact half cone.

Examples of the basic cone structure that could be generated are shown in Figures 5 and 6 with Figure 5 showing the basic form of a 60 cone and Figure 6 showing the basic structure ofa 1200 cone.

Several cones may be joined together to create a multi-cone structure. The cones intersect along what is termed a hinge formed from the elongate members so that at the intersection, the interconnecting elongate members of the two intersecting cones actually form parallelograms with one another. The shape of the hinge along its length may be parabolic, hyperbolic, elliptical or circular, depending on the number ofcones which are interconnected and their angle of inclination with respect to one another Figure 7 shows one example of a structural hinge whilst Figure 8a shows an example of a structural hinge which joins two 600 cones together. The form of the resulting structure is shown in Figure 8b.

Figures 9a and 9b and Figures 10a and 10b show respectively the interconnection of three 1200 cones and the interconnection of six 60 cones using the above described hinges.

In the structures of Figures 7 to 10 small parallelograms 48 and large parallelograms 50 are used in order to form the hinges.

The strtural hinge arrangement can be utilised to form a wide range of different connections so that cones, arches, open and straight ends can be formed. Figures 11, 12 and 13 show some of the possible arrangements of structural hinges based on the hexagonal arrangement shown in Figure lb. Figure 11 shows a structural arrangement for connecting five cones and two arches, Figure 12 shows a structural hinge arrangement for connecting four cones and two arches, and Figure 13 shows a structural hinge arrangement for connecting four cones and one arch.

Where a half cone shape on its own is generated, the structure is open and may be used to create a door or hole anywhere in a space structure. Figure 14, for example, shows an arrangement of two 1200 cones with a 1200 open end. The cones intersect at a hinge 60 whilst at the open end ofthe structure the elongate members 64 which would otherwise have projecting free ends are connected to additional elongate members 66. As a result, the free ends are not left protruding.

Figure 15 shows part of an open end structure.

Figure 16a shows the detailed structure of a 60 cone with a 60 open end whilst Figure 16b is a diagrammatic representation of the final structure covered with a suitable material.

Figure 17 shows a modified form of elongate member 12' which is formed by two parallel elongate element, 82 which are interconnected by a number of braces 84 to provide rigidity to the member 12'. Although the braces 84 are shown in Fig 17 as extending generally perpendicular to the elements 80, 82 they can extend transversely of the elements at any suitable angle.

Figure 18 is an end elevation of the member of figure 17.

Figure 19 shows how several members 12 are interconnected with the adjacent upper elements of the members being inter-connected and the adjacent lower elements of the members also being inter-connected.

Whilst the modules which are illustrated in Figures 1 a and 2a and described above use three members to form a triangular structure, it will be appreciated that the number of members may be varied in order to form a polygonal structure. Thus, the module may form a square, rectangle, pentagon or hexagon or the like instead ofthe illustrated triangle, using the desired number of members. In addition, whilst the polygon may be a regular polygon, it will also be appreciated that by varying the angles a the polygon which is formed may be an irregular polygon. Thus a module may have two angles a the same and one different or three different angles a.

For a three-dimensional structure as described above, using a single type ofmodule the shape of the ultimate structure is self generating and is in effect defined by four parameters of the module, these being the angle a, the length l, the length L of each member and the crosssectional shape of the members.

The spacing between the longitudinal axes of interconnecting members at their point of interconnection also, with the length L of the members, determines or influences the curvature of the structure.

A structure using the above-described modules has many degrees of freedom and will find its own shape which tends to be a shape with minimum potential energy. The interconnections between the modules may be made flexible or may include some damping provision which renders the structure to some extent flexible and therefore resistant to earthquake damage.

The invention has many different applications and a structure built using modules according to the present invention could be used as a temporary or permanent shelter.

Geometrical structures such as arches, inclined arches, cones, flat surfaces, domes, polyhedra and free shapes could be constructed with, for example, plastics sheeting used to cover the structure.

The interconnections of the modules and/or of the individual members of a module may be chosen to suit a particular structure and may be flexible or allow pivoting or relative rotation to a desired extent of the modules and/or of the members.

Claims

1. A module for a space structure, the module comprising three elongate members: wherein each member has a first, free end and a second end connected at or adjacent said second end to one other of said members intermediate the ends of said one other member, thereby to form a triangle.

2. A module for a space structure, the module comprising at least three elongate members interconnected with one another by way of a plurality ofjoints thereby to form a polygonal structure; and wherein each said joint comprises an interconnection of only two of said members.

3. A module according to claim 2 wherein the polygon formed by the module is regular.

4. A module according to claim 2 wherein the polygon formed by the module is irregular.

5. A module according to any one of claims 2 to 4 wherein the polygon is a triangle.

6. A space structure comprising a plurality of modules as claimed in claim 1 wherein the free end of each said member is connected to a further member of a like module intermediate the ends of said further member thereby to form said space structure.

7. A space structure comprising a plurality of modules as claimed in any one of claims 2 to 5 wherein each said member of each module is connected to a further member of a like module by way ofa further saidjoint comprising an interconnection ofonly said member and said further member.

8. A space structure comprising a plurality of elongate members wherein at least one end of each member is connected to another said member intermediate the ends of said other member so that a triangle is formed between the three interconnected members.

9. A space structure according to claim 8 wherein the elongate members are of substantially equal lengths.

10. A space structure according to any one of claims 6 to 9 wherein the external angle formed between members at ajoint is between 100 and 1700.

11. A space structure according to claim 10 wherein the external angle formed between members at ajoint is between 900 and 1500.

12. A module according to claim 1 wherein the external angle formed at each junction between the members is approximately 1200 to form an equilateral triangle.

13. A space structure according to claim 11 wherein the external angle formed at each junction between the members is approximately 1200 to form an equilateral hexagonal grid.

14. A space structure according to any one of claims 6 to 11 and defining aportionofthe surface of a cone.

15. A space structure according to claim 14 and comprising portions of the surface of a plurality of cones, intersecting on structural hinges.

16. A space structure according to claim 15 wherein said structural hinges each comprise a plurality of modules of non-triangular polygonal form.

17. A space structure according to claim 16 wherein said non-triangular polygonal modules are of parallelogram form.

18 A module according to any one of claims 1 to 5 and 12 wherein the longitudinal axes of at least two interconnected members are spaced apart at the interconnection of the two members.

19 A module according to claim 18 wherein the longitudinal axes of each pair of interconnected members are spaced apart at the interconnection of the members thereby to create a three dimensional module.

20 A space structure according to any of claims 6 to 11 and 13 to 17 having a plurality of modules according to claim 18 or 19.

21 A space structure according to any of claims 6 to 11 and 13 to 17 having a minimum potential energy configuration.

22 A space structure according to any of claims 6 to 11, 13 to 17 and 20 wherein the shape of the structure is determined by the following parameters of the modules: the external angle a formed between two interconnected elongate members of each module; the length X of each side of the polygon formed by each module; the length L of each elongate member; and the cross-sectional shape of the elongate members.

23 A module according to any one of claims 1 to 5, 12, 18 and 19 wherein each elongate member is formed by two parallel elements.

24 A space structure according having a plurality of modules according to claim 23.

25. A module for a space structure substantially as hereinbefore described with reference to, and as illustrated in any Figure of the accompanying drawings.

26. A space structure substantially as hereinbefore described with reference to, and as illustrated in any Figure of the accompanying drawings.