TØNDEVOLD, Tore (Lofthus terrasse 11, Oslo, N-0588, NO)
HEGLUND, Kim (Vestre vei 81 C, Nesøya, N-1397, NO)
TØNDEVOLD, Tore (Lofthus terrasse 11, Oslo, N-0588, NO)
C l a i m s
1. Method for fabrication of a truss girder with a triangular, quadrangular or polygonal cross sectional shape, produced from materials suitable for extrusion and comprising at least an upper chord and a lower chord interconnected by means of inclined braces and with a large distance between the corners of the truss girder, the units forming the truss girder, such as the chords, are fabricated separately and then assembled by fixations at the corners, c h a r a c t e r i z e d i n that a corrugation or zigzag shaped inclined brace is brought in correct position with respect to a chord and attached to said chord at a plurality of positions along the chord and the inclined brace, the inclined brace being attached to the chord at such positions by means of suitable clips or clamps for clamping and/or bolting the inclined brace to the chord.
2. Method according to claim 1, wherein the opposite side of the corrugation or zigzag formed inclined brace are brought into correct position to a second chord and attached to said second chord at a plurality of positions along the inclined brace, at positions where the inclined brace is in contact with said second chord, by means of suitable clips or clamps.
3. Method according to claim 2, wherein a still further corrugation or zigzag shaped inclined brace is brought in correct, second position with respect to a chord with already assembled inclined brace, and is attached to the chord at a plurality of positions along the inclined brace at places where the inclined brace is in contact with the chord, by means of clips or clamps.
4. Method according to one of the claims 1-3, wherein the chord is provided with suitable outwards projecting fins or projections extending in the entire length of the chord, said fins or projections being extruded in the same process as the extrusion of the profile intended to form a corner of the chord, while said inclined brace is formed as a separate extruded profile, where the profile is given a shape facing the chord, which is complimentary with the chord surface for locking or clamping, said shape is complimentary to the shape of the fins or the projections.
5. Method according to claim 1-5, wherein said connection between the inclined brace and the chord in addition is improved by means of locking means, such as rivets, bolts or the like and/or by means of gluing, welding rolling with or without inwards projecting point deformation, surface deformation or the like.
6. Truss girder, particularly adapted to form a transom in a traffic gantry, where the truss girder is formed with triangular, quadrangular or polygonal shaped cross sectional area, produced of a material suitable for extrusion, and comprising at least an upper chord and a lower chord interconnected by means of inclined braces, and where the distances between the corners of the truss work girder are large, the units forming the truss girder, such as the chords, are fabricated separately and thereupon fixed together along their corner edges, c h a r a c t e r i z e d i n that said units forming the chord are provided with parallel, outwards projecting fins or projections extending along the entire length of said unit, and that the inclined brace is extruded, given a shape which is complementary the shape of the space between said fins or projections, and that the inclined brace and said unit is fixed together by means of suitable clips or clamps pressed over the inclined brace and is snapped on to said fins or projections.
7. Truss girder according to claim 6, wherein the fins or projections at their foot on the main body of the chord are provided with one or more recesses intended to cooperate with corresponding outwards projecting bead or lips on the free arms of the clip or clamp.
8. Truss girder according to claim 6 or 7, wherein said recesses and said lips are configured in such way that they prevent movement of the braces in direction outwards away from the chord.
9. Truss girder according to one of the claims 6-8, where the outer end of the fins, at least on the exterior surface, are chamfered in order to ease the snapping on effect or clamping effect of said clips or clamps.
10. Truss girder according to one of the claims 6-9, where the inner surface of the clip or the clamp, and the space between the two parallel fins are configured in such way that said surfaces and spaces in assembled or clamped position correspond to the cross sectional shape of the brace.
11. Truss girder according to claim 10, where said inner surface and said space between the fins or projections, and the corresponding shape of the profile cross section of the brace, are provided with recesses or the like, in order to prevent relative rotational movement of the braces with respect to the chord.
12. Truss girder according to one of the claims 6-11, where the profile forming said chord and/or said brace are provided with an opening extending in axial direction through the entire profile.
13. Truss girder according to one of the claims 6-12, wherein the chord and the brace are fixed together by means of clips or are clamped together at a plurality of attachment points between the chord and the brace in the longitudinal direction of said units.
14. Truss girder according to one of the claims 6-13, where said clamps are formed of two separate elements which are hinged together at one end and designed for locking to the chord at the opposite end, using bolts or the like. |
TRUSS GIRDER AND METHOD FOR CONSTRUCTING THE SAME
Technical Field
The present invention relates to a method for production of a truss girder having a triangular, quadrangle or a polygonal cross sectional shape, produced of extruded material and comprising at least an upper chord and a lower chord which are interconnected by means of braces and with a large distance between the corners edges of the truss girder; where the unit forming the truss girder, such as the chords, are produced separately and subsequently assembled and fixed together at the corners .
The invention relates also to a truss girder, for example produced by means of a method described above.
Background for the Invention
For traffic gantries of such type it is from a traffic point of view desired that the gantries shall be designed in such way that they cause as little damages to humans and the vehicle as possible during a possible collision.
Since the motorways become wider and improved, and due to the need and the requirements for improved and additional traffic information, there exists an increasing need for larger and larger gantries, both with respect to length and load carrying capacities. Such increasing dimensions of the gantries require larger and larger girders crossing the motorway in order to carry its own weight. In addition, the gantries have to be dimensions for carrying larger payload to be supported by the gantries. Hence, it is also a need for making the gantries as light as possible and still maintain the structural integrity, strength and load carrying capacities.
Further, there is a need for robust structures which may be able to carry the loads and to resist the moments acting on the structure at any time, without causing the gantry to collapse when exposed to such forces. As an example it should be appreciated that the traffic signs and the traffic auxiliaries supported by the gantry may be very heavy and having a large wind exposed area. Further, said signs and/or auxiliaries may be eccentrically positioned and the maximum wind forces acting on the gantry may be formidable. The signs will thus impose formidable moments on the load carrying truss girder, produced by the wind loads acting on such equipment.
WO 2006/031126, belonging to the applicant, describes a collision safe frame for large traffic gantries, the frame comprising a plurality of legs, each supported at their lower end by a foundation, while at their upper end, each leg supports one or more transverse transoms, girders or the like, intended to carry traffic signs and/or lights, or the like. The transom used is in the form of a truss girder made of extruded aluminium, for example of the type sold under the trademark Lattix®.
When designing and fabricating such truss girders of extruded aluminium, the moment capacity limits the height and/or width of the truss girder. Such type of truss girder has a moment capacity of approximately 150 kN and a maximum possible height of 380 mm. One of the reasons for these limitations resides in that the blank from which each element of the gantry is made, is an extruded profile comprising a cross sectional area which is uniform along the entire length of the profile and where the connection between two parallel profile cross sections is in the form of a very thin area and cross section, partly slotted, the two edge profiles being pulled laterally apart in order to form the grating pattern required. For such type of solu-
tions, it is limited how far apart the two side profiles may be laterally pulled away from each other without causing yield in the node material.
Summary of the invention
An object of the invention is to provide a traffic gantry which will be able to carry and resist all forces and bending moments appearing in the gantry, caused by weather, wind and the bending moment acting on the gantry and other means and auxiliaries supported by the gantry.
Another object of the invention is to provide a traffic gantry having increase load carrying capacity and structurally strength without the need of increasing the weight of the gantry to the same extent. A still further object is to provide a method for simple and rationally assembling of such traffic gantries.
A still further object of the invention is to provide a truss girder produced from extruded materials, where the height of the distance between two adjacent chords may be increased substantially without a corresponding increase of the weight of the truss girder.
An even further object of the present invention is to provide a traffic gantry which may be transported and delivered in a flat packed state, for example to be assem- bled in situ where the gantry is to be erected or in the vicinity of such installation site.
A still further object of the invention is to provide a traffic gantry which in a cost saving manner may be transported from the production plant to the assembly site or installation site on conventional trucks, lorries or vessels .
The objects according to the present invention may be achieved by a truss girder and a method for manufacturing such truss girder as further defined by the independent
patent claims .
Alternative embodiments and preferred solutions according to the invention are defined by the dependent claims . An essential advantage of the solution according to the present invention is that the solution makes it possible to manufacture a truss girder which no longer is dependent on the inherent limitations in chord height or girder dimensions which, otherwise implied in the more conventional truss girders produced by extruding.
Another essential advantage is that the truss girder may be fabricated as separate units, suitable for flat packing and hence may be assembled at the site where the gantry is to be erected, or in close vicinity of such site. In such way the cost of transportation is reduced while it will be far less expensive and much simpler, both to manufacture and assemble such structure. In spite of the increased dimensions of the gantry the weight will not increase correspondingly, making it possible to use the conventional crane capacity as previously used for prior art gantries.
Due to the new design, greater flexibility with respect to the size of the traffic mean to be supported by the gantry, is also achieved.
Short Description -of the Drawings
An embodiments of the present inventions shall now be described in more detail referring to the drawings, where:
Figure 1 shows a view of a gantry, e.g. intended to be used in conjunction with traffic information on a motorway;
Figure 2a shows a side view of a truss girder forming part of the gantry shown in Figure 1;
Figure 2b shows an end view of an assembled truss
girder according to one embodiment of the invention, seen perpendicularly in the longitudinal direction of the truss girder;
Figure 2c shows an end view of an alternative cross sectional shape of a truss girder; said girder having a trapezoidal shape;
Figure 3a shows a side view of a second embodiment of an element forming part of a truss girder according to the invention; Figure 3b shows a corresponding end view of an assembled truss girder, showing an assembly of two elements as shown in Figure 2a and two elements as shown in Figure 3a;
Figure 3c shows a variant of the alternative embodiment shown in Figure 3a; Figure 4 shows a vertical section through the corner of an upper chord in a truss girder shown in Figure 2a or 3a;
Figure 5 shows a vertical section ' through the corner of the upper chord in a truss girder prior to attachment of the intermediate inclined braces;
Figure 6 shows a vertical section through a clip according to the invention, used to rigidly attach the intermediate inclined braces to an upper chord;
Figure 7 shows a vertical section through the braces according to the invention;
Figure 8 shows a section through a joint plate for joining of two profiles of the truss girders in longitudinal direction;
Figures 9-11 show a preferred method for securing a proper locking of the inclined braces to an upper chord or a lower chord, the element forming a corner or an element of the chord, having a some what different design compared to the design shown in the Figures 4 and 5;
Figure 12 shows a section seen along the line A-A in
Figure 3a;
Figure 13 shows a side view of a node according to the invention;
Figure 14 shows in perspective a section through the node shown in Figure 13, seen along the line 13-13;
Figure 15 shows a section through a second embodiment of the node according to the present invention, seen along the line 13-13 in Figure 13;
Figure 16 shows schematically a first stage in the process of assembling, using a third embodiment of a clip according to the present invention, seen along the line 13-13 in Figure 13;
Figure 17 shows schematically a section through the clip shown in Figure 16, after the clip is attached to the corner section by means of a bolt; and
Figure 18 shows an even further embodiment of a clip or a clamp according to the present invention.
Detailed Description of an Embodiment of the Invention Figure 1 shows a view of a gantry 10, for example used in connection with traffic information, extending across and above a motorway. The gantry 10 comprises for example inclined, supporting legs 11, arranged in pairs, at least on each side of the motorway and preferably also in the mid shoulder (s). A truss girder 12 extends across the motorway, supported by pairs of legs 11. The middle pair 11 is inclined outwards and downwards from the truss girders 12, while the pairs of legs 11 at the end also are inclined in the longitudinal direction of the gantry 10. The gantry 10 shown in Figure 1 may for example be of a type as described in WO 2006/031126, belonging to the applicant, the content of which hereby being included by the reference. The traffic information may for example be large illuminated information signs or the like.
Figure 2a shows a side view of a truss girder 12 designed to extend across the motorway. As shown in the Figure, the truss girder 12 comprises an upper chord 13 and a lower chord 14. The truss girder 12 according to the embodiment shown has a quadrangular cross sectional shape, where the upper chord 13 comprises two upper corner sections 15 and inclined braces 16 extending between said upper two corner sections 15. Correspondingly, the lower chord 14 comprises two corner sections 15' and inclined braces arranged between said lower corner sections 15' . Corresponding inclined braces 16 extend also between the upper chord 13 an the lower chord 14 at each corner section 15,15'. Each corner section 15,15' is formed of extruded metal, such as for example aluminium, and has preferably uniform cross sectional area along its entire length. One embodiment of the corner section 15,15' is shown in more details in Figures 4 and 5 and will described in further details below.
Each inclined brace 16 is also formed of an extruded metal, such as for example aluminium, also having uniform cross sectional shape along its entire length. The blank intended to form the inclined braces 16 is also extruded in straight lengths, and then bent or formed into a more or less zigzag shaped or a more or less undulated form. The shape of the inclined braces will be described in further details below in connection with Figures 4 and 7. The clips 17 fix the undulated or zigzag shaped braces to the corner sections 15,15' at points where the parts 18 of the braces 16 are in contact with the corner sections. Figure 2b shows a view of the end of a truss girder 12 comprising four corner profiles 14 and four inclined braces 16. The cross section shown has a quadrangle, equal-sided shape.
Figure 2c shows a vertical section through a corre-
sponding truss girder 12, where the cross sectional shape is trapezoidal.
Figure 3a a shows an alternative embodiment of an element forming part of the truss girder 12. The essential difference compared to the solution shown in Figure 2a is that two different bracing elements 16 are used, these being interconnected by nodes 29 by means of a modified clip solution 27.
Figure 3b shows a view of the end of a truss girder 12, formed of four corner profiles 15, for example corresponding to the ones shown in connection to Figure 2a and which will be described in further details below. Two opposite sides are further formed of single inclined braces 16, corresponding to the one shown in Figure 2a, while two other opposite sides are formed of two inclined braces 16, fixed and rigidly connected in nodes 29, for example by means of modified clips. A second alternative of such assembled inclined braces may be formed by strings of straight profiles which are partly split and where the zigzag shaped is achieved by pulling the straight profiles outwards in lateral direction.
Figure 3c shows an alternative embodiment of the solution shown in Figure 3a, where the difference being the design of the node 29. The nodes 29 are formed by extruding the two strings, intended to form the inclined bracings 16, and then by slotting, punching or milling away material so that there only is a metal connections between the two strings where the nodes 29 are designed to be, whereupon the strings are pulled apart laterally outwards, thereby creating the double zigzag pattern.
Figure 4 shows a section through a corner section 15,15', seen along the line 3-3 in Figure 2a. As shown, the corner section 15,15' is formed of an elongated, hollow profile which preferably is made of extruded
aluminium. Along two of sides, the corner section 15,15' is provided with two outwards projecting fins 19 spaced apart. The fins 19 extend along the entire longitudinal direction of the corner sections 15,15'. The outer end of the fins 19 are along their outer edges preferably- chamfered. Further, at their attachment line along the corner sections 15,15', the fins 19 are provided with a recess 20. As indicted in the Figure, the corners etc. of the corner sections 15,15' are rounded in order to reduce possible stress concentrations and the possibilities of cracking at the corners .
As further shown in Figure 4, the zigzag shaped inclined brace 16 is attached to the fins 19 of the corner sections 15,15' by means of a clip or a clamp 17 according to the present invention. The clip 17 is given a more or less U-shaped form having an inner surface adjusted to the external surface of the inclined brace 16. The clip 17 is configured in such way that it is suited for being snapped on to the outwards projecting arms 19 of the corner section 15,15' . The two arms on the clip 17 have a length which corresponds to the height of the profile of the braces 16 plus an additional sufficient length for enabling the ends of the U-shaped arms to extend past the recesses 20 at the foot of the outwards projecting fins 19. For this purpose the end of each of the two arms of the U-shaped clip 17 is provided with inwards projecting lips 22. The lips 22 are configured to cooperate with the recesses at the foot of the fins 19, so that the clip 17 may be snapped on for locking of the braces 16. The arms of the clip 17 has for this purpose a certain inherent elasticity, thereby securing that the outer end of each arm of the clip 17 and the lips may slide past the thickened outer end of the fins 19 and slip into the recess 20, locking the brace 16 to the corner section. In
order to ease the snapping, the outer end surfaces of the fins 19 are chamfered.
As shown in Figure 4, also the adjoining sides of the corner section 15,15' are formed with a corresponding profile as described above for locking the horizontal braces of the truss girder 11 to the corner section.
The fins 19, the cross section of the inclined braces 16 and the clip 17 are given such dimensions and shape that a narrow space between the surface facing the surface of the inclined brace 16 and the surface of the corner section between the fins 19 is formed, when these elements are assembled. As further shown in Figure 4 also the inner surface of the fins 19 may be slightly chamfered, so that the cross sectional area of the opening between the two fins is reduced in inwards direction towards the corner sections 15,15' . The purpose of such chamfering is to establish a cooperation with the corresponding inclined surfaces on the adjoining surface of the inclined braces 16, so that these are locked even further by a pressure inwards towards the centre of the corner section 15,15' . Also the opposite side of the inclined brace has a corresponding chamfered shape, cooperating with the shape of the inner surface of the U-shaped clip 17.
Further, the transition from the fins 19 in towards the main body of the corner section may be slanted by an angle corresponding to the internal shape of the outer end of the two arms of the clip 17. Such solution, where the two opposite surfaces of the brace 16 and the cooperating surfaces of the corner section 15,15' and the U-shaped clip 17 respectively lock the inclined brace 16 to the corner section 15,15', prevents rotation of the units.
Figure 5 shows a section through the corner section 15,15' according to the invention. As specified above, the corner section is extruded as a continuous length having a
uniform cross section. The corner section 15,15' may for example be made in length of 15 meters and may be joined by means of joining plates 23, which will be described in further details below. According to the embodiment shown in Figure 4, the corner section 15.15' may be provided with attachment means 24 for attachment for example of information carrying signs. Since the corner section 15,15' is extruded, both the fins 19 and the attachment means 24 extend along the entire length of the profile. Figure 6 show a vertical section through the clip 17 according to the present invention. Also the clip 17 may preferably be made by extrusion of a material suitable for extrusion in hole lengths and thereupon cut into smaller units having a length adapted to the length of that part of the inclined brace 16 which is intended to be fixed to the corner section 15,15' .
Figure 7 shows a section through the profile forming basis for the inclined brace. It should be appreciated that also the inclined bracing 16 is extruded in straight lengths having a uniform cross sectional area, and the bent for formation of the required zigzag shape. As shown in the Figure the profile is further provided with an opening 25 extending through the entire profile. The inclined bracing profile may for example be provided with a straight length of 7 metres. After the bending, and dependent upon the sideways extension, the end product of the inclined bracing may have a length of 5 metres.
Figure 8 shows a section through a joining plate 23. The Joining plate 23 is also formed of a material suitable for extrusion, such as for example aluminium. The joining plate 23 is also provided with a opening 24 extending lengthwise through the element may for example be extruded in large length with a uniform cross section and thereupon cut into pieces with a length sufficient to establish a
proper and secure joint between two corner section units 15,15' . The joining plate 23 has external dimensions and shape adapted to the internal dimensions and internal shape of the corner sections 145,15'. When joining, one end of a joining plate 23 is firstly inserted into the opening 26 in the corner profile to the required depth, whereupon an adjacent corner section 15,15' is threaded on to the free end of the joining plate 26, preferably till the two ends of the adjoining corner sections 15,15' are in an end to end position.
Figures 9-11 show various stages in the process of providing additional locking effect of the clip to the corner profiles 15. The inclined braces 16 are according to this embodiment formed as described above, while the corner profile in addition to the previously described form, also is provided with outwards projecting fins 30, for example extending along the entire length of the corner profile 15. Figure 9 shows a stage where the inclined braces 16 are fixed to the corner profile 15 by means of the clip 21 according to the invention, but where the fins 30 still is not pressed against the outer surface of the clip 21. Figure 10 and 11 show a stage in the assembly process where the fins are bent down against the outer part and outer end of the legs of the U-shaped clip 21. Figure 10 shows a section where the fins 30 are pressed in towards the clip, while Figure 11 shows a section through the assembled unit, indicating that the fins are bent down on each side of the clip, both in front of and behind said clip 21. Such rolled locking will produce a wave shaped joint in the longitudinal direction of the elements, providing an add-on effect to the locking effect.
Figure 12 shows an alternative node connection 29. The blank for the node 29 may be in the form of an inte-
grated body 31 having two parallel ducts 32 provided with openings extending through the body, formed and dimensioned for receiving the string forming the braces 16. Such integrated body 31 may also be extruded into a long body intended to be cut into shorted lengths, adjusted to the required length of the node 29. The two ducts 32 may be interconnected by means of an intermediate, integrated element 33. For such solution the body 31 is pressed onto the two blanks intended to form the inclined braces 16 and placed in desired position, preferably prior to bending of the braces 16 to its required zigzag shape. If there is a need for locking the node 29 with respect to the braces 16, the material in the node may for example be riveted or pressed together in points, so that a locking effect is produced.
Although the intermediate connection is shown having two plates, it should be appreciated that such connection in stead may be in the form of a centrally arranged plate. Figure 13 shows a view of a node between a corner section 15 and a brace 16 where a clip 21 according to the invention is used, while Figure 14 shows in perspective a section through the node shown in Figure 13, seen along the line 13-13 in Figure 13. As indicated in the Figures the clip 21 is sideways prolonged and chamfered. Such shape enables use of nails 35 or bolts for locking the clip 21 and the bracing 16 to the corner profile. Further, the Figures indicate use of glue in the form of glue strings 34, alternatively glued surfaces, gluing the clip 21 to the bracing 16 and to the corner profile 15. Due to the prolonged side walls of the clip 21, it is possible to gain access to the unit with a riveting tool or a tool for nailing together the clip 21 and the chord/bracing in a simple manner.
Even though the Figures 13 and 14 show a clip having
chamfered end surfaces, it should be appreciated that that the clip may have any other shape. In this connection it should be appreciated that the clip may be configured and shaped in such way that it will be practical to get access for tools for clamping, nailing or riveting, bolting or the like of the brace to the chord.
Figure 15 shows a section through the corner profile 15, provided with two outwards projecting fins 21, and that a clamp is used. According to this embodiment, the clamp is formed of to separate arms 21 which are rotatably hinged by means of a hinge 36. The free end of the arms 21 and the fins 19 are dimensioned and configured in such manner that the ends of the arms 21 may be inserted into a space between the two fins 19 and then clamped, deformed or locked in any manner, for example by means of bolts or nails (not shown) .
Figures 16 and 17 show an alternative embodiment where the clamp 21 is provided with two free arms 21 which at one end is rotatably connected to each other by means of a hinged connection 36, while the free ends of the arms 21 are intended to be arranged outside a profile on the corner profile 15 and then to be clamped to the corner profile by means of clamping means such as for example bolts or rivets. Figure 18 shows an even further embodiment of the present invention, where the corner profile 16 is provided with fins in the form of a closed channel 40, such as also shown in the Figures 16 and 17, where the channel 40 at its free end is provided with sideways and outwards projecting flanges 41 configured to cooperate with recesses in the profile of the brace 16. Further, each element of the clamp 21 is at its free end provided with sideways and outwards projecting flanges 38 configured to be inserted into a recess in the corner profile 15, so
that a stopping edge is formed, for example arranged at each corner. Due to said recess in the corner profile, the stopping edge 39 and the sideways and outwards projecting flanges 38, it is possible to attach the clamp, possibly without use of locking means, such as rivets, bolts, glue, etc. Further, the clamp 21 is provided with fins or edges 42 shaped to cooperate with corresponding surfaces or edges on the profile of the brace 16.
Even though the above described embodiment is based on clips, it should be appreciated that, in lieu or in addition, clamps which completely or partly may extend around the brace and be attached to the chord by means of mechanical means, such as bolts or the like, may be used. Alternatively, or in addition, gluing may also be used for improving the locking or fixing of the brace to the chord.
Further, it should be appreciated that the clip and the fin or the projection may be configured in such way that the arms of the clip are pressed inn between the two fins and produces an outwards force against the inner surface of fins, in stead of pressing inwards against the outer surface of the fins as shown in Figures 2-13.
The connection between the clip or the clamp may be improved by gluing adequate surfaces .
For manufacturing and assembling a truss girder according to the present invention, the following method may be applied:
Firstly the various profiles, i.e. the corner profiles 15,15', the profiles intended to be the basis for the clipsl7, the profiles intended to form the joining plates 23, and also the profiles forming the inclined brace 16, are extruded. The profile for the clips and the joining plates are cut into shorter lengths, adjusted to the intended purpose, while the profiles intended to form the braces 16 are bent to the required wave or zigzag
shape .
If the truss girder is intended to have a quadrangular cross sectional shape, the upper chord and the lower chord are firstly manufactured separately, the upper chord and the lower chord each comprising two parallel corner sections 15, 15' with an intermediate bracing. A chord is formed by bringing a brace profile into correct position in relation to a corner section profile 15,15', whereupon the clips 17 are positioned around the intended area on the brace, pressed on to the fins projecting outwards from the corner section 15,15' and snapped on to these. This operation is performed for each contact area between the brace 16 and the corner section. When both the upper and lower chord in this way is assembled as separate units, said two different units are assembled by bringing a further brace profile in position between said two chords on each side and fixed to the free fin profile in a corresponding manner as described above.
In use a completed, assembled truss girder is exposed to forces which tend to pull the corner profiles away from the inclined braces. In addition to the hooks and possible tight fit between the various parts and/or surface deformation and adhesion, it may be an additional need of securing that not all joints are positioned in the same cross section. In order to secure a proper attachment between the braces and the corner section, the clip may in addition therefore be fixed to the fins, for example by means of welding, pressing, point deformations, gluing, riveting, for example by point pressing, or other known ways to secure proper adhesion between two surfaces.
In order to secure as high structurally integrity as possible in the joints between to adjoining profiles, the corner sections may for example be given different length, so that the joints are sideways displaced with respect to
each other .
Even though the assembled truss girder shown has a square or rectangular cross sectional shape, it should be appreciated that the cross sectional shape may have a trapezoidal, triangular or polygonal shape. The only essential modification will in such case be the design of the corner profile used for tying the braces together.
Even if the invention is described in respect to large truss girders used for manufacturing large traffic gantries, it should be appreciated that the invention also may be used in respect to other functions. Such other functions may for example be girders used in building construction or industry, as elements forming part of scaffolding, or similar types of areas obvious for a person skilled in the art.
Even though Figure 12 shows a solution where the node is in the form of one piece where the inclined braces are threaded through the central hole, it should be appreciated that the node in stead may be formed as two ϋ-Shaped bodies, facing away from each others and interconnected at their bottoms and where the braces placed between the legs of each U-shaped body and locked by means of clips as described above.
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