EP2706194A2 - Formwork girder - Google Patents

Abstract

The frame girder (1a) has two bottom belts (2a,2b) and an upper belt (3) together forming the corner points of a triangle in its cross-section and extending in its longitudinal direction. The two bottom belts are connected with the upper belt by a framework arrangement (4b,4c) made of four different struts inclined to each other. The framework arrangement is connected with the upper belt and the bottom belts by maximum four welded joints. Two of the four struts are fixed commonly to the upper belt and one of the bottom belts by a single welded joint.

Description

The invention relates to a lattice girder for the expansion of tunnel-shaped structures according to the features in the preamble of claim 1.

The vault obtained during excavation in the construction of underground structures requires direct support to secure it. For this purpose, carrier frames adapted to the respective breakout geometry are used. In the course of the subsequent expansion with a concrete shell, the individual support frames remain within the same by the concrete shell is created in Ortbetonweise using shotcrete.

Compared to the use of solid profiles for the support frame, metal lattice girders in the form of a truss structure have proven themselves. Their advantage lies in both the material and weight savings as well as in the prevention of unwanted voids by the otherwise occurring in solid wall profiles spray shadow. The individual lattice girders are only lined up on site to one another in the circumferential direction of the expansion Grid arch composed, which allows thanks to its open structure a homogeneous construction of the concrete shell. The individual lattice girders achieve a high bond quality with the concrete shell, in which they serve as additional reinforcement in addition to the use of welded mesh.

The DE 197 11 627 A1 discloses a lattice girder frame composed of lattice girders for the construction of a tunnel. The individual lattice girders each have a top chord and two bottom chords which extend together in the longitudinal direction of the lattice girder. Here, they form the vertices of a triangle in the cross section of the lattice girder to each other. The upper chord is connected to the individual lower chords via a truss of a variety of struts. Compared to the known in the art formation of the framework of individual struts or a continuous meandering curved rod here the use of several truss assemblies is proposed, which are composed of four mutually different inclined struts. By a juxtaposition of several framework arrangements in the longitudinal direction of the lattice girder, the framework thus formed then extends over the entire length of the lattice girder.

The basic structure of the individual lattice girders of two lower chords and a top chord and between these successive truss arrangements of four struts has already proven itself many times in practice. Despite the use of materials, which is low in itself, the production represents an increased outlay, since the lattice girders are welded constructions. Usually, the struts extending between the top flange and the two bottom straps are joined to the latter by means of end welds. In a framework arrangement of four individual struts thus a total of eight welded joints are necessary. By the arrangement shown in the prior art two V-shaped bent rods for obtaining the necessary four struts a reduction of the required welded joints to a total of six has already been achieved.

Against the background of the most economical production of lattice girders, in particular the arrangement of the struts within the individual truss arrangements and their attachment to the lower chords and the upper chord still leaves room for improvement.

The invention is based on the object to improve a lattice girder for the expansion tunnel-shaped structures to the extent that this is more economical to produce with a minimum number of necessary welds.

The solution to this problem consists according to the invention in a lattice girder with the features of claim 1.

Thereafter, it is provided that the four individual struts having truss assembly is connected via a maximum of four welds with the upper flange and the two lower chords. The inventive reduction of the necessary welded joints to a total of four per truss assembly is achieved in that each of two of the four struts are defined via a single weld together on the upper flange and one of the lower chords.

The advantage here is to be seen in the simplified production, which results in a reduction of the necessary welds to a maximum of four per truss assembly.

If the truss arrangements located one behind the other between the upper belt and the lower belts are placed close together, a further reduction of the necessary welded connections is also conceivable. Thus, the end regions of the truss arrangement, on each of which two of the four struts run towards each other, as close as possible to the end of an immediately adjacent truss arrangement created be set so that the respective end portions of the two truss assemblies with a total of four struts over a single weld. Due to the design, this form of fixing takes place here on the upper flange of the lattice girder.

As remaining in the reinforced concrete shell reinforcement, the lattice girders are made of metal. The lower chords and the upper chord are more closely welded to the trusses connecting them. The opposite in the transverse direction of the lattice girder struts are also connected to the transverse webs connecting them by welding. Advantageously, the individual connections are made in economic point resistance welding.

Both the upper and lower chords may have various cross-sectional shapes, such as square, rectangular, and oval, or combinations of the foregoing. Advantageously, these are circular, to allow easy production. In principle, the lateral surface of the individual straps can also be given a structure, such as, for example, ribbed or profiled reinforcing steel. This increases the composite effect of the lattice girder with the concrete surrounding it.

Advantageous developments of the inventive concept are the subject of the dependent claims 2 to 10.

In principle, the individual truss arrangements can have four struts, which each butt against the upper and lower chords. The struts can be both straight and curved. Even cross-sectional jumps in the course of the individual struts are conceivable in order to meet any static requirements. With a view to the simplest possible handling of the framework arrangement preferably two of the four struts of the framework arrangement are preferably integrally connected to form a single hanger. Here are each two individual struts formed from a common rod, which has a corresponding bend in the region of its central portion. About the bend is then the orientation of the resulting struts.

Depending on the design of the lattice girder, the simple hanger of the truss arrangement thus formed may be joined with its middle portion having the bend with the upper flange or with one of the lower girths. In this arrangement, the free ends of the two struts of the single hanger can be fixed either together on the upper flange, on one of the lower chords or with one of their free ends on one of the two lower chords. The introduced via the bend V-shaped configuration of the single bracket allows due to the necessary connection to the three straps corresponding alignments.

In principle, in each case two free ends of the four struts of the truss arrangement are fixed via a common welded connection to the upper flange or one of the lower chords.

In an alternative embodiment, it is provided that each individual strut has at least one angled end. In the bend is a change in direction of the rod axis of the strut at the free end. Preferably, the bend is formed so that the necessary bending of the strut in the region of the upper belt or one of the lower chords, so that the remaining end portion of the bend extends parallel to the longitudinal direction of a belt.

The advantage of said bending is to be seen in the fact that their parallel course to one of the straps produces a line contact with it, wherein a correspondingly long welded joint can be arranged. In addition to the diameter of the welded joint, in particular its length is decisive for the forces to be transmitted between the strut and one of the straps. In addition to tensile and compressive forces occur especially at this point on shear forces, which over the along the Angled extending weld joint can be safely transferred to the respective belt.

The bend can be arranged so end of the strut that the strut rests with its angled on one of the straps or this at least laterally peripherally touched. In addition to the so deliberately controlled initiation of any forces from the strut in one of the straps, this also affects the opening width of the lattice girder between its lower chords.

The opening width here means the respective distance between two mutually opposite struts of the truss arrangement, which each extend in a wedge shape from the upper flange to the two lower chords. In an arrangement of the bend on one of the opposite outer sides of the lower chords, therefore, the largest possible opening width results, whereas an arrangement on the immediately opposite inner sides of the lower chords causes the smallest possible opening width.

In principle, the opening width can also be correspondingly increased by a bending or bulging of the struts.

In a further advantageous embodiment, it is provided that the respective four struts of a single truss arrangement are integrally connected to form a double bow. In other words, in this case the respective free ends of the two struts of a simple bracket are integrally connected to the ends of two further struts of another simple bracket. Such a double hoop is therefore formed from a multiple bent and self-contained single rod. The free ends of this multiply bent single rod can be stumped, the double bow can also have seamless transitions.

The particular advantage here is to be seen in the simplest possible handling of the individual framework arrangement, which due to the training a single double hanger requires little or even no temporary holding measures during the necessary joining process with the straps.

In addition to the possibility of an obtuse impingement of the individual struts on one of the straps, two of the struts may preferably be integrally connected to one another via a straight intermediate section. Here are the so interconnected struts with the straight intermediate section on one of the straps or have a peripheral contact with this.

Such a configuration corresponds to the formation of a simple bracket, which in addition to a simple bend in the region of its central portion has an additional bend. Said bends are spaced apart such that the respective strut has a straight intermediate section from one bend to the other bend. Particularly preferably, the straight intermediate portion is designed so that its orientation is oriented on the course of the belt, on which the two struts of the single bow to be determined. For the resulting advantages of a straight intermediate section apply the points already mentioned above for bending, the advantage being seen in particular in a sufficient length for the required welded joint.

In an alternative embodiment, in each case two of the struts can be integrally connected to one another via a loop. Under a loop in the context of the invention is a bend to understand, which has a correspondingly large bending radius. In this respect, the loop is not a mere fold, which of course also involves a bending radius, but rather a curved course of a section of a strut, which clearly separates the straight sections of the strut in the form of a single hoop.

In this case, the loop may have a single bending radius or multiple bending radii between the two struts of a simple bracket. In the arrangement of several bending radii, these can also lead to a spatial and thus multi-axially oriented embodiment of the loop.

Advantageously, the loop can embrace either the upper belt or one of the lower straps at least partially. Here, the loop is adapted to the outer contour of the respective belt. The advantage can be seen in a clear positioning of the truss assembly on the respective belt, as this occupies a clear position relative to the belt due to the loop, which has the respective contact to the loop. As a result, the necessary temporary holding measures during the manufacture of a lattice girder can be reduced to a minimum.

The invention further provides that the four struts of a single truss arrangement can also be arranged skewed to each other. Compared to an axisymmetric configuration of the individual truss arrangement, wherein the respective axis of symmetry in the cross section of the lattice girder extends through the upper flange and between the two lower chords, the skewed configuration generates an offset of the opposing struts. In a side view of the lattice girder with a view of the lower chord and the underlying lower chords, the struts extending from the upper chord to the two lower chords are therefore not congruent, but enclose an angle between them.

A skewed embodiment of the individual truss arrangement advantageously results in the formation of at least one loop between two struts, which thereby does not run perpendicular to one of the straps, but obliquely thereto. In this way, the largest possible opening between the individual straps of the lattice girder is possible in spite of the shortest possible development of such a curved single rod, the so obliquely arranged loop a sufficiently long line contact with a has the straps to make a sufficiently long welded joint can.

It is envisaged that between two struts of the truss arrangement, which extend from the top chord to one of the bottom chords, at least one transverse web can be arranged. The individual transverse web extends between two struts and is advantageously arranged at a distance from the upper flange and at a corresponding distance from the lower chords.

The particular advantage lies in the contactless spacing of the transverse webs of the individual straps, whereby the triangular shape formed in the cross section of the lattice girder is reduced. This is achieved by shifting the individual transverse webs as the base of the triangle away from the lower belts and thus towards the upper belt. This results in a free space which extends between the lower chords to below the transverse webs. The cross section of the lattice girder formed by the truss struts and the transverse webs thus substantially resembles an A-shape. Preferably, the distance to the upper flange and the distance to the lower chords have a ratio of 1: 2 to 1: 6 to each other. In an arrangement of the transverse webs within the indicated range, an economic ratio of the bending stiffness of the truss struts achieved by the transverse webs results in the clearance between the lower belts.

In the necessary for the transport or storage stacks of lattice girders dive this each with their upper flange and a portion of the struts of the truss arrangements in the obtained space, thereby reducing the stack height. The legs of the lattice girder formed from the struts are still stiffened over the transverse webs. The remaining unsupported lever arm of the struts is determined by the position of the transverse webs between the upper flange and the lower chords.

In the arrangement of a plurality of transverse webs on the lattice girder, these may have identical or different configurations from one another. In addition to a straight course of the individual cross bar can for example also be bent or folded and have individual formations or cross-sectional jumps. Of course, a combination of the above is conceivable. Preferably, the transverse web has a curved course. Particularly preferably, the curved transverse web is open to the lower chords.

The advantage consists in the joints of the transverse web with the struts which are thus located as close as possible to the lower chords, whereas the middle section of the transverse web is displaced as far as possible to the upper chord. In this way, despite sufficient stiffening of the interconnected struts a sufficiently large space between the legs formed by the struts of the lattice girder is created to achieve a deep immersion of another lattice girder between them. In this way, the stackability of multiple lattice girders is improved, since at the same height of the stacked lattice girders whose number is increased. This leads to a more cost-effective transport, since significantly more lattice girders can be brought to their destination per journey.

The invention shows a very economically producible lattice girder, which in terms of its static properties requires only a small amount of material and at the same time manages with a minimum of required welded joints. The targeted arrangement of the four struts within the individual truss arrangements, it is now possible to define such a spatial structure, each with a total of four individual welds on the upper flange and the lower chords.

By reducing the necessary joints in particular a shorter production time per lattice girder is achieved, whereby at the same expense, the number of units to be reached is increased. This also applies to the necessary verification of individual welds, thanks to a lower number of joints significantly simpler and thus made more economical.

Figur 1

einen erfindungsgemäßen Gitterträger in perspektivischer Darstellungsweise;

Figur 2

eine alternative Ausgestaltung des Gitterträgers aus Figur 1 in selber Darstellungsweise;

Figur 3

eine weitere vorteilhafte Ausgestaltung des erfindungsgemäßen Gitterträgers in ebenfalls perspektivischer Darstellungsweise;

Figur 4

eine alternative Ausgestaltungsform des Gitterträgers aus Figur 3 in selber Darstellungsweise;

Figur 5

eine weitere Ausgestaltungsmöglichkeit des erfindungsgemäßen Gitterträgers in perspektivischer Darstellungsweise;

Figur 6

eine alternative Ausgestaltungsform des Gitterträgers aus Figur 5 in selber Darstellungsweise;

Figur 7

eine weitere vorteilhafte Ausgestaltungsform der Gitterträger aus den Figuren 5 und 6 in selber Darstellungsweise;

Figur 8

den erfindungsgemäßen Gitterträger in einer weiterentwickelten Ausgestaltungsform zu den Gitterträgern aus den Figuren 5 bis 7 in selber Darstellungsweise;

Figur 9

der Gitterträger aus Figur 8 in einer Untersicht sowie

Figur 10

den Gitterträger aus den Figuren 8 und 9 mit Blick in dessen Längsrichtung.

The invention is explained in more detail with reference to some schematic drawings shown in the drawings. Show it:

FIG. 1

a lattice girder according to the invention in a perspective representation;

FIG. 2

an alternative embodiment of the lattice girder FIG. 1 in self-presentation;

FIG. 3

a further advantageous embodiment of the lattice girder according to the invention in a likewise perspective representation;

FIG. 4

an alternative embodiment of the lattice girder FIG. 3 in self-presentation;

FIG. 5

a further embodiment possibility of the lattice girder according to the invention in a perspective representation;

FIG. 6

an alternative embodiment of the lattice girder FIG. 5 in self-presentation;

FIG. 7

a further advantageous embodiment of the lattice girder from the FIGS. 5 and 6 in self-presentation;

FIG. 8

the lattice girder according to the invention in a further developed embodiment of the lattice girders of the FIGS. 5 to 7 in self-presentation;

FIG. 9

the lattice girder FIG. 8 in a soffit as well

FIG. 10

the lattice girder from the FIGS. 8 and 9 with a view in the longitudinal direction.

Out FIG. 1 is an inventive lattice girder 1 shows how he, for example, for the expansion of tunnel-shaped structures use. The lattice girder 1 is composed primarily of three straps running in its longitudinal direction in the form of two lower straps 2 a, 2 b and one upper girth 3. In the cross section of the lattice girder 1, the two lower chords 2a, 2b and the upper chord 3 form the vertices of a triangle to each other.

To the individual straps 2a, 2b; 3 spaced from each other and to fix with each other, the lower chords 2a, 2b in the present case via two truss assemblies 4a, 4b connected to the upper flange 3. In the FIG. 1 on the right individual truss arrangement 4a sits like those adjacent to it and in FIG. 1 shown truss assembly 4b from four different mutually inclined struts 5a - 5d together.

Usually, such lattice girders 1 are installed with the two lower chords 2 a, 2 b for the rock jacket not shown here. In order to ensure a corresponding adaptation to the respective breakout geometry, the lattice girders 1 can be arcuately curved in a manner not shown here. According to the invention, the truss arrangements 4a, 4b shown here are each connected to the upper flange 3 and the two lower chords 2a, 2b via a maximum of four welded connections 6a-6d which are not shown in detail. Such a reduced number of necessary welded joints 6a-6d is achieved in that in each case two of the four struts 5a-5d are fixed to the upper run 3 and one of the lower chords 2a, 2b via a single welded joint 6a-6d.

With reference to in FIG. 1 The truss assembly 4 a shown on the right is thus in the present case the struts 5 a, 5 b lying in the foreground and extending from the upper belt 3 to the front lower belt 2 a via the individual welded connection 6 d to the front lower belt 2 a. In contrast, said struts 5a, 5b each having one of in FIG. 1 in the background and from the rear lower flange 2b to the Upper flange 3 extending struts 5c, 5d, each with a single welded joint 6a, 6b fixed to the upper flange 3.

Due to their design, the individual truss arrangements 4a, 4b have a rhomboidal shape in a plan view which is not detailed here. The furthest apart corner points of the truss assemblies 4a, 4b run on the top flange 3 and are joined with this over the individual welds 6a, 6b. In contrast, the shorter spaced apart vertices of the respective truss assembly 4a, 4b respectively at the lower chords 2a, 2b and are on the remaining individual welds 6c, 6d, each with one of the lower chords 2a, 2b joined.

As can be seen, the two illustrated truss arrangements 4a, 4b initially differ in that their struts 5a-5d extending away from the upper flange 3 abut either on an inner side 7 or on an outer side 8 of the two lower chords 2a, 2b. The inner side 7 of the two lower straps 2a, 2b defined by the fact that they are directly opposite. In contrast, the two outer sides 8 of the lower chords 2a, 2b facing away from each other.

The different arrangement of the struts 5a-5d of the two shown truss arrangements 4a, 4b is to be understood here as an alternative embodiment. In principle, the lattice girder 1 can have only one of the two variants of a truss arrangement 4a, 4b shown. Of course, a mixture of both variants of the truss assemblies 4a, 4b shown within a lattice girder 1 is conceivable.

Furthermore, both truss arrangements 4a, 4b shown comprise an embodiment such that in each case two of the four struts 5a-5d of the respective truss arrangement 4a, 4b are integrally connected to one another to form a single hoop 9a, 9b. For this purpose, the respective single hoop 9a, 9b formed from a continuous rod, which in his Central portion has a corresponding bend 10. As a result of the bend 10, the sections adjoining the middle section of the bar experience a deviation from one another, as a result of which the respective struts 5a, 5b; 5c, 5d training.

In the present case, the respective single hoop 9a, 9b is fixed in the region of its bend 10 via a respective individual welded connection 6c, 6d to one of the lower chords 2a, 2b. In contrast, the free ends of the struts 5a - 5d butt against the upper flange 3 and are joined via individual welds 6a, 6b with this.

It is also conceivable here an orientation of the respective single hoop 9a, 9b such that it is fixed in the region of its bend 10 via one of the individual welded joints 6a, 6b on the upper flange 3, while its struts 5a, 5d; 5b, 5c extend to one of the lower chords 2a, 2b, respectively.

In particular, with regard to the presentation of the FIG. 1 On the left truss arrangement 4b shown, a straight intermediate section 11 can be seen in the region of the bend 10. In the present case, such a straight intermediate section 11 is also present in the adjacent truss arrangement 4a, with the straight intermediate section 11 not resting on the outside 8, but on the inside 7 of the two bottom straps 2a, 2b. In this way, two of the struts 5a, 5b; 5c, 5d integrally connected via the straight intermediate portion 11.

With regard to the truss arrangements 4a, 4b shown, it becomes clear that in addition to their struts 5a-5d, they additionally have individual transverse webs 12a, 12b. The respective transverse webs 12a, 12b are in this case between two of the struts 5a, 5b extending from the upper belt 3 to one of the lower belts 2a, 2b; 5c, 5d of the respective framework arrangement 4a, 4b.

From the in FIG. 1 The truss arrangement 4a shown on the right can be seen that its individual transverse web 12a is displaced so far toward the lower belts 2a, 2b that it is arranged in the region of the bends 10 of the two single bars 9a, 9b. In an advantageous manner, the transverse web 12a extends beyond the two bends 10, so that the two lower webs 2a, 2b have peripheral contact with the transverse web 12a. This results in manufacturing advantages, since the prefabricated with the cross bar 12a truss assembly 4a can be placed with the projecting end portions of the crosspiece 12a on the two lower chords 2a, 2b, whereupon in the subsequent joining process, the two individual welds 6c, 6d created.

In contrast, the transverse web 12a can be fixed to the two lower straps 2a, 2b even in the loose state relative to the two simple straps 9a, 9b only together with the latter via the two individual welded connections 6c, 6d.

From the in FIG. 1 The truss arrangement 4b shown on the left can be seen to include not just one, but two transverse webs 12b. The two transverse webs 12b are spaced both to the lower chords 2a, 2b and to the upper flange 3 and have a curved course. The individual transverse web 12d is aligned with respect to its bending so that it opens to the lower chords 2a, 2b out.

In particular, the position spaced from the lower belts 2a, 2b in combination with the curved profile of the transverse webs 12b offers an advantage when stacking a plurality of lattice girders. As a result, the top flange 3 of another lattice girder 1, not illustrated here, can penetrate deeper between the two bottom straps 2 a, 2 b before it comes to rest on the bent transverse webs 12 b. Opposite the in FIG. 1 The embodiment of the truss arrangement 4a shown on the right thus results in a design-related lower stack height.

Out FIG. 2 shows an alternative embodiment of a lattice girder 1a according to the invention. Opposite the lattice girder 1 off FIG. 1 the present lattice girder 1a differs in that one with respect to the representation of FIG. 2 Right truss assembly 4c shown opposite the truss assembly 4a FIG. 1 a total of two straight transverse webs 12a includes. Analogous to in FIG. 2 shown on the left and already off FIG. 1 known truss assembly 4b are the straight transverse webs 12a of the right truss assembly 4c spaced both to the lower chords 2a, 2b and to the upper flange 3 out. This results in the same as already in relation to the left in the Figures 1 and 2 illustrated truss assembly 4b executed positive effect with respect to the stackability of the lattice girders 1, 1a.

FIG. 3 shows a further embodiment of the lattice girders 1, 1 a from the Figures 1 and 2 , In the form of a further lattice girder 1b according to the invention, its two alternative embodiments of truss arrangements 4d, 4e largely correspond to the truss arrangements 4a, 4b FIG. 1 , As a difference compared to the framework arrangements 4a, 4b FIG. 1 In the present case, end-side angled portions 13 are to be named, which are arranged at the free ends of the struts 5a-5d of the two single hoops 9a, 9b.

The end bends 13 of the struts 5a - 5d are designed so that its orientation is parallel to the longitudinal direction of the upper belt 3. Furthermore, the two single hoops 9a, 9b are arranged close to each other with their rectified bends 13 on the upper belt, so that the respective struts 5a, 5d; 5b, 5c can be fixed on the upper belt 3 via a single welded connection 6a, 6b.

FIG. 4 shows a further embodiment of a lattice girder 1c according to the invention, which in terms of the arrangement of bends 13 on the struts 5a - 5d as far as possible from the lattice girder 1 b FIG. 3 equivalent. Opposite the lattice girder 1 b FIG. 3 differs the present Lattice girder 1 c to the effect that this in turn has two rectilinear transverse webs 12a, which extends between the struts 5a, 5d; 5b, 5c of the opposed single bow 9a, 9b extend. Said transverse webs 12a are analogous to the embodiment in FIG FIG. 2 arranged on the struts 5a - 5d, resulting in a further variant of a truss arrangement 4f according to the invention.

As already in FIG. 2 clarifies, are present also the transverse webs 12a of FIG. 4 Truss assembly 4f shown on the right both to the lower chords 2a, 2b and to the upper flange 3 spaced. In contrast, the in FIG. 4 Left illustrated truss assembly 4e of the already known truss assembly FIG. 3 ,

FIG. 5 shows a further alternative embodiment of a lattice girder 1d according to the invention. In contrast to the previous lattice girders 1, 1a - 1 c of FIGS. 1 to 4 those are the lower belts 2a, 2b executed with the upper flange 3 truss arrangements 4g, 4h executed differently. With a view of the in FIG. 5 Truss assembly 4g shown to the right corresponds to the arrangement of the transverse web 12a with respect to the number and location of the in the FIGS. 1 and 3 shown lattice girders 1, 1 b. The same applies to the in FIG. 5 Left half-timbered arrangement 4h and their arrangement of their curved transverse webs 12b, which in their spacing to the two lower chords 2a, 2b and the upper flange 3, the embodiments in the previous FIGS. 1 to 4 correspond.

In contrast to the previous truss arrangements 4a-4e, in the present case their respective four struts 5a-5d are in each case integrally connected to one another with the formation of a double hoop 14a, 14b. As a result, the respective truss assembly 4g, 4h each formed from a self-contained and multiply bent rod.

As can be seen, two of the four struts 5a, 5d; 5b, 5c of the two alternative truss arrangements 4g, 4h via a respective loop 15 integrally connected. In this case, the respective double bow 14a, 14b lies over its loops 15 on the top flange 3 and is joined thereto via the individual welded connections 6a, 6b.

FIG. 6 shows an embodiment of a lattice girder 1e according to the invention, which largely the embodiments of the lattice girder 1d in FIG. 5 equivalent. In contrast to the lattice girder 1d FIG. 5 In the present case, those loops 15 connecting the respective double bars 14a, 14b to the upper chord 3 are visibly more pronounced. As a result, in the present case, the upper flange 3 is encompassed by the loops 15 at least in regions in its circumference.

In an alternative embodiment, not shown here, the loops could also be arranged in the region of the lower chords 2a, 2b, as a result of which they would also be encompassed circumferentially at least in some areas.

FIG. 7 that already shows FIG. 6 known embodiment of the truss assemblies 4g, 4h FIG. 6 , Wherein the arrangement of the straight transverse web 12a on the embodiments of the previous lattice girders 1a, 1 c from the Figures 2 and 4 oriented. As a result, a further alternative embodiment of a truss arrangement 4i is shown. In this case, the cross bar 12a is spaced in an already known form from the two lower straps 2a, 2b and the upper flange 3.

Out FIG. 8 shows a further alternative embodiment of a lattice girder 1g according to the invention. In contrast to the previous symmetrical embodiments of the individual truss arrangements 4a-4i, a further variant of truss arrangements 4j, 4k is shown in the present case. Initially, the two truss arrangements 4j 4k are double bars 14a, 14b, as already described in FIGS FIGS. 5 to 7 known. In contrast to the previous truss arrangements 4a-4i, however, the four struts of the individual truss arrangements 4j, 4k are arranged skewed relative to one another here.

As a result, the longitudinal axes of the struts 5a, 5d running towards each other form; 5b, 5c mentally no common point of intersection. In addition, that is, in each case two of the struts 5a, 5d; 5b, 5c integrally connected to each other loop 15 inclined to the otherwise past each other passing struts 5a, 5d; 5b, 5c to connect with each other.

As a result of said skewed configuration of the respective four struts 5a-5d of the individual truss arrangement 4j, 4k, they do not extend congruently in a side view of the truss girder 1g which is not shown in detail. On the contrary, the struts 5a, 5d extending from the lower chords 2a, 2b to the upper chord 3 close; 5b, 5c each have an angle between them. Both the in FIG. 8 The truss arrangement 4j on the right as well as the framework arrangement 4k shown on the left each have a single straight transverse web 12a, which analogously to the representations of the truss arrangements 4a, 4d and 4g of FIGS. 1 . 3 . 5 and 6 each in the region of the bends 10 and thus in the region of the lower chords 2a, 2b are arranged. Of course, even with the skewed configuration of the truss arrangements 4j, 4k present here, the transverse webs 12a can be spaced apart in a manner not shown both towards the lower belts 2a, 2b and towards the upper belts 3 or even have a curved course, as with the transverse web 12b the truss assemblies 4b, 4e and 4h in the FIGS. 1 to 7 shown.

FIG. 9 clarifies the embodiment of the lattice girder 1g according to the invention FIG. 8 , In the present case, a bottom view of the lattice girder 1 g is shown, in which the view through the two lower straps 2 a, 2 b passes through the upper girth 3. In this illustration, it is clear that the configuration of the loops 15 requires an additional bend 16 in order to connect the struts 5a-5d of the two truss arrangements 4j, 4k, which run askew to one another, in one piece.

Despite the skewed configuration of the two truss arrangements 4j, 4k, it can be seen that the two transverse webs 12a are at right angles to the upper flange 3 run. If these are spaced in a manner not shown both to the lower chords 2a, 2b and to the upper flange 3 out, they can assume a corresponding inclination to each other due to the skewed orientation of the individual struts 5a - 5d.

FIG. 10 again shows the already from the FIGS. 8 and 9 Known lattice girder 1g with a view in the longitudinal direction. In the foreground, the framework arrangement 4j is shown, which is arranged with its struts 5a-5d in the region of the bends 10 on the inner sides 7 of the two lower chords 2a, 2b. Due to the skewed configuration of the framework arrangement 4j, the loop 15 is laterally offset on the upper flange 3, about the respective struts 5a, 5d; 5b, 5c integrally connect with each other.

Reference numerals:

1 -

girder

1a -

girder

1b -

girder

1c -

girder

1d -

girder

1e -

girder

1f -

girder

1g -

girder

2a -

lower chord

2 B -

lower chord

3 -

upper chord

4a -

Truss arrangement

4b -

Truss arrangement

4c -

Truss arrangement

4d -

Truss arrangement

4e -

Truss arrangement

4f -

Truss arrangement

4g -

Truss arrangement

4h -

Truss arrangement

4i -

Truss arrangement

4y -

Truss arrangement

4k -

Truss arrangement

5a -

strut

5b -

strut

5c -

strut

5d -

strut

6a -

welded joint

6b -

welded joint

6c -

welded joint

6d -

welded joint

7 -

Inside of 2a, 2b

8th -

Outside of 2a, 2b

9a -

easy Ironing

9b -

easy Ironing

10 -

bend

11 -

straight intermediate section

12a -

crosspiece

12b -

crosspiece

13 -

angling

14a -

double handle

14b -

double handle

15 -

loop

16 -

bend

Claims (10)

Lattice girder for the construction of tunnel-shaped structures, which comprises in its longitudinal direction and in its cross section the vertices of a triangle forming two lower chords (2a, 2b) and a top chord (3), wherein the two bottom chords (2a, 2b) by at least one Truss assembly (4a - 4k) of four mutually different inclined struts (5a - 5d) are connected to the top flange (3), characterized in that the truss assembly (4a - 4k) via a maximum of four welds (6a - 6d) with the top chord ( 3) and the lower chords (2a, 2b), wherein each two of the four struts (5a - 5d) via a single welded joint (6a - 6d) together on the upper flange (3) and one of the lower chords (2a, 2b) set are. Lattice girder according to claim 1, characterized in that in each case two of the four struts (5a-5d) of the truss arrangement (4a-4k) are integrally connected to one another to form a single stirrup (9a, 9b). Lattice girder according to claim 1 or 2, characterized in that each of the struts (5a - 5d) has at least one end-side bend (13). Lattice girder according to Claim 1, characterized in that the four struts (5a-5d) of the truss arrangement (4a-4k) are integrally connected to one another to form a double strap (14a, 14b). Lattice girder according to one of Claims 2 to 4, characterized in that the single bow (9a, 9b) and / or the double bow (14a, 14b) are / is formed from a bent bar. Lattice girder according to one of claims 2 to 5, characterized in that each two of the struts (5a - 5d) via a straight intermediate portion (11) or a loop (15) are integrally connected together. Lattice girder according to claim 6, characterized in that the loop (15) either the upper flange (3) or one of the lower chords (2a, 2b) at least partially surrounds. Lattice girder according to one of claims 1 to 7, characterized in that the four struts (5a - 5d) of the truss arrangement (4a - 4k) are skewed to each other. Lattice girder according to one of claims 1 to 8, characterized in that between two of the upper flange (3) to each one of the lower chords (2a, 2b) extending struts (5a - 5d) of the truss assembly (4a - 4k) a transverse web (12a , 12b) is arranged. Lattice girder according to claim 9, characterized in that the transverse web (12b) has a curved course, wherein the transverse web (12b) opens to the lower chords (2a, 2b).

Images