EP2050887A2 - Lattice girder - Google Patents

Abstract

The girder (1) has walings (4) passing in a longitudinal direction of the girder and a cross stay chain (5) welded at the walings. The chain has upper bends (6) between diagonally bent vertical bars (2, 3). Anchorage elements (7) i.e. round or flat steel bar sections, are attached to the bends of the chain upwardly and/or downwardly in the girder for applying bar forces in a concrete of a cover e.g. flat slab. Free gaps (Z) are formed between the elements in a longitudinal direction of the girder without the walings.

Description

The invention relates to a lattice girder according to the preamble of patent claim 1.

In order to increase the shear force resistance of a plate-shaped ceiling or the puncture resistance with point load transfer, punching reinforcements or shear force reinforcements in different designs are installed in concrete components. A well-known punching reinforcement system consists of individual reinforcement elements, eg. B. double headed bolt. Such punching reinforcements also to increase the transverse force capacity of flat ceilings are easy to install and provide a significant increase in the puncture resistance of the concrete slab. Other known punching reinforcements contain several lattice girders. The anchoring points of the supporting diagonal and / or vertical struts of the diagonal strut coil of the respective lattice girder lie on the component inside of the bending tensile reinforcement, which, however, leads to lower puncture resistances compared to a punching shear with double-head bolts ( Magazine: Concrete and Steel Concrete Construction, Issue 6, 2003, "New punching reinforcement for element ceilings, author Eligehausen et al .). In order to achieve high punching loads, the anchoring of the supporting struts is to be arranged as far as possible outside, ie, as far as possible, especially in the area of the upper bending tensile reinforcement.

At one off EP1070800A Known punching reinforcement anchoring the supporting vertical and diagonal struts of the diagonal strut snake takes place in that the bends as loops over the top flange or the upper girths protrude above. Although this increases the punching resistance, no punching resistance values are achieved on the basis of the anchoring points located further down, as is possible in plates with double-head bolts. In this known punching shear the achievable puncture resistance also results from the continuous belt, which is used in addition to the protruding bend as an anchoring element. This belt can, based on the position of the bending tensile reinforcement of the ceiling, lie only on the inside of the plate of the ceiling, if the upper bending tensile reinforcement of the plate when installing from above should not be laboriously threaded below the continuous straps. The continuous belt as anchoring element for the struts can thus not be optimally far outside or arranged above. Furthermore, the distance between the continuous belt and the top of the protruding over the belt bend must be adapted to the layer thickness of the built-in Biegezugbewehrung to use the optimum possible altitude to be able to. Such adjustments cause costs and complicate the application. Finally, the stack height of the lattice girders inconveniently increases by the projection of the bend over the upper chord.

Out EP-A-0781891 a reinforcement for flat slabs is known, wherein upper and / or lower bending reinforcement mats are provided and incorporated between these helical shear reinforcement elements. Each shear reinforcement element is welded to bends on an inserted mounting bar, which is fixed to rods of the bending reinforcements with anchoring elements designed as wire loops.

Out DE-U-7112799 is known a lattice girder without bottom straps, whose diagonal struts snakes with upper bends over the upper chord and is welded thereto. The lower bends of the diagonal strut coils are deformed into clamping loops in order to be able to suspend rods from reinforcing mats.

Out DE-U-1983738 is a lightweight lattice girder with profiled upper metal strap, lower straps made of round iron, and diagonals made of iron. The lower bends of the diagonals have horizontal parts, to each of which a reinforcement holder is firmly attached. The lower flange can be covered with a concrete foot.

Out WO-A-05/014950 is a lattice girder with upper girth and lower girths and Drahtdiagonalstrebenschlangen known. The lattice girder has at the lattice girder ends down over the lower chords cross-anchoring teeth for support on a vertical panel.

Out US-A-3400508 is a lattice girder with only one upper chord known in which the diagonals of the diagonal strut coil are bent downwards horizontally in order to hold there reinforcing elements pincers. In a middle level of the lattice girder, transverse connecting bars are welded in between the diagonals due to the lack of lower chords.

Out EP-A-1433908 is a lattice girder with two diagonal strut snakes, but without upper girth and with two lower girths. The bends of the diagonal struts snakes are directly welded together at the top or in between with at least the bending curvature einmügte wire hanger, whose ends are bent downwards greatly.

Out DE-U-9015953 is a lattice girder with a top chord, two bottom chords and two diagonal struts known. In upper bends of the diagonal struts snakes crossbars are welded to the upper flange.

The invention has for its object to provide a lattice girder of the type mentioned, which can achieve a high lateral force and / or puncture resistance while maintaining the advantage of simple installation in a ceiling, no adjustment of the belt height requires, and is low stackable.

The stated object is achieved with the features of claim 1.

The anchoring elements attached to all or only selected bends replace, as it were, a belt that passes through in the longitudinal direction of the lattice girder. Thus, to initiate the strut forces in the concrete large areas and one as far as possible outboard anchoring point are created. Since intermediate spaces are formed between the anchoring elements in the lattice girder longitudinal direction, which can be used for easy installation of the respective Biegezugbewehrung without threading, no adjustment of the altitude of a continuous belt is required more. Since the bends do not survive, the lattice girders can be better stacked. Most effective is the replacement of a continuous belt by the anchoring elements at the location of a top chord, since this area is generally in the tension zone of the concrete slab. However, a plurality of anchoring members could alternatively or additionally be attached to the lower bends or to selected lower bends to achieve the same benefits at the bottom of the component. Thanks to the spaces between the anchoring elements ensures that the upper Biegezugbewehrung can be installed next to and between the anchoring elements from above in the concrete component without having to be threaded under continuous upper straps. The lattice girder can then be stored on special Abstandsabhaltern or other lattice girders. Due to the gaps, the anchoring elements, uninfluenced by the strength of the respective Biegezugbewehrungslage, can be continuously attached to an optimum height for the punching resistance at the bends.

Suitably, the upper side of the anchoring element closes off with the upper side of the bend, or closes off the underside of an anchoring element arranged below in the lattice girder with the underside of the bent strut of the bend. For manufacturing reasons, and to achieve optimally placed welds, the top or the However, bottom of the anchoring element are even within a range bounded by the top and bottom of the bend. To z. B. to achieve even better welding conditions, the top or bottom of the anchoring element (depending on whether anchoring elements are mounted in the lattice girder at the top or bottom as a replacement of a continuous belt) on the top or bottom of the bent strut of the bend maximum up to strength to survive the diagonal strut snake in the bend.

The respective anchoring element is either fixed only positively or only positively or force and form-fitting in the region of the bend, for example, welded and / or latched.

An anchoring element in the form of a round or rectangular steel section is welded to, on or adjacent to the bend or between two bends adjacent in the transverse direction of the lattice girder such that the anchoring element is as high as possible at the anchor point and with its ends approximately in the longitudinal direction of the lattice girder , if necessary, protrudes over the bend. It could also be expedient to provide two or more welds between the anchoring element and the bend per bend. The respective anchoring element increases the anchoring rigidity in this anchoring point.

The length of the anchoring element can correspond to three to eight times the thickness of the anchoring element in order to form a load point anchoring point as strong as possible in the ceiling.

Alternatively, the anchoring element may be a steel or cast molding which, to further stabilize the anchoring point, surrounds one or two bends adjacent to one another in the transverse direction of the lattice girder on a plurality of sides, preferably three to four sides.

Alternatively, the molded part could also be latched and / or welded in place as anchoring element between two bends adjacent in the transverse direction of the lattice girder.

The molding could have widenings at one or more locations to increase the load introduction areas.

The molding could be connected as an anchoring element via a positive connection with one or more bends.

So could the molding, z. B. side, in the bend or bends be introduced so that a central mandrel of the molding engages the bend, and two side parts of the molding are arranged outside the bend and extend with their tops to about the top of the bend.

In another type of molding, it could be inserted into the bends from below, with a center portion of the molding fitted into the bending curve of the bend, and side portions of the molding adjacent the bends extending to at least approximately the level of the top of the bend ,

The absence of a continuous belt in the region of the bends to which anchoring elements are attached may result in longer lattice girders requiring special measures for transport. Therefore, it is expedient to attach at least one additional center belt between the upper and lower bends of the diagonal strut coil on the lattice girder, at least for transport and installation. Such middle straps do not interfere with the installation of the bending tensile reinforcement. As an alternative to a lattice girder that does not require additional center straps, shorter lattice girders are conceivable which have only two to five or more bends of the diagonal strut serpent.

In an expedient embodiment of the lattice girder, vertical and inclined struts or exclusively mutually oppositely inclined struts or exclusively vertical struts or exclusively struts inclined in the same direction are provided in the longitudinal direction in succession in each diagonal strut coil.

In another advantageous embodiment, the lattice girder on two spaced, continuous lower chords and two diagonal struts welded thereto, which form a substantially symmetrical or A-shaped, or due to different lengths or different inclined struts asymmetric cross-section of the lattice girder. With two spaced continuous lower straps and only one diagonal brace, lower bends of the diagonal brace are either mutually offset with respect to the lower straps, or the lower bends are cross-sectioned from the center to one side only and connected to the lower straps in the region of these bends. It can also be two spaced, however positioned close to each other, through bottom straps and two parallel diagonal strut coils welded to the bottom straps. It lacks thus a continuous upper flange, and are attached to all or only to selected bends anchoring elements, between which in the longitudinal direction of the lattice girder gaps for installing the rods of Biegezugbewehrung are formed.

It would be possible in alternative embodiments, provide underlying anchoring elements in place of a longitudinally continuous lower chord and longitudinally between the anchoring elements free spaces to install in a ceiling lower reinforcing layers or their cross bars can comfortably.

Fig. 1 a - c

einen Abschnitt einer ersten Ausführungsform eines Gitterträgers, in einer Seitenansicht mit eingebauter, oberer Biegezugbewehrung, im Querschnitt, und in einer Draufsicht und ohne Biegezugbewehrung,

Fig. 2a, b, c

drei unterschiedliche Ausführungsvarianten eines Gitterträgers in Sei- tenansicht, d. h., quer zur Längsrichtung,

Fig. 3a, b, c, d

Variationen von Querschnitten von Gitterträgern,

Fig. 4a - c

eine weitere Ausführungsform eines Gitterträgers, in Seitenansicht, im Querschnitt, und in Draufsicht,

Fig. 5a - c

eine weitere Ausführungsform eines Gitterträgers in einer Seitenan- sicht, im Schnitt, und in einer Draufsicht,

Fig. 5d, e

zwei Detailvarianten, in Draufsicht auf einen Gitterträger,

Fig. 6a - c

eine weitere Ausführungsform eines Gitterträgers, in Seitenansicht, im Querschnitt, und in Draufsicht, und

Fig. 7a - c

eine weitere Ausführungsform eines Gitterträgers, in Seitenansicht, im Querschnitt, und in Draufsicht.

Embodiments of the subject invention will be explained with reference to the drawing. Show it:

Fig. 1 a - c

a section of a first embodiment of a lattice girder, in a side view with built-in, upper bending tensile reinforcement, in cross-section, and in a plan view and without bending tensile reinforcement,

Fig. 2a, b, c

three different embodiments of a lattice girder in a side view, ie, transversely to the longitudinal direction,

Fig. 3a, b, c, d

Variations of cross sections of lattice girders,

Fig. 4a - c

a further embodiment of a lattice girder, in side view, in cross-section, and in plan view,

Fig. 5a - c

2 shows a further embodiment of a lattice girder in a side view, in section, and in a plan view,

Fig. 5d, e

two detail variants, in plan view of a lattice girder,

Fig. 6a - c

a further embodiment of a lattice girder, in side view, in cross-section, and in plan view, and

Fig. 7a - c

a further embodiment of a lattice girder, in side view, in cross section, and in plan view.

Hereinafter, various embodiments of lattice girders 1 based on Fig. 1 to 7 described for the creation of a punching and / or shear force reinforcement in the Concrete a ceiling to be embedded, especially in a point-based element or flat ceiling, or even in a resting on a wall crown or a wall-supporting ceiling, where locally locally punctiform or linear high loads are to be expected. In such places, multiple lattice girders are always installed as a punching or shear force reinforcement and combined with the usual reinforcements of the ceiling, such. B. with upper and / or lower Biegezugbewehrungen of longitudinal and / or transverse bars.

The embodiment of the lattice girder 1 in the Fig. 1a to 1c has an A-shaped symmetrical cross-section and has two each extending in a plane diagonal struts 5 with successively inclined and vertical struts 2, 3, which are connected to each other via upper bends 6 and lower bends 6 '. The lower bends 6 'are, for example, welded to the inside on outer longitudinally continuous lower straps 4. The two upper bends 6 are adjacent to each other in the transverse direction of the lattice girder 1 with a distance. There is no continuous upper flange in this area. Between the upper bends 6, an anchoring element 7 is welded, for example, a round or flat steel section. The round steel section may be stronger than the struts 2, 3, and have a length, the z. B. three to eight times the thickness of the round steel section, so that the anchoring element 7 protrudes in the longitudinal direction on both sides of the bends 6 and anchors them together.

Depending on the expected load case 6 anchoring elements 7 may be attached to all upper bends, or only at selected upper bends 6. In the longitudinal direction of the lattice girder 1 7 free spaces Z are formed between the anchoring elements, which in Fig. 1 a for convenient insertion of transverse bars 8 an upper bending tensile reinforcement can be used on which longitudinal bars 9 of the bending tensile reinforcement are placed. The longitudinal bars 9 are located between anchoring elements 7 adjacent lattice girder 1. The arrangement of this Biegezugbewehrung could also be reversed, ie the longitudinal bars 9 could be arranged below and then the cross bars 8. Likewise, multi-layered bending tensile reinforcement would be installable. Regardless of the thickness of the respective reinforcement layer, the anchoring elements 7 in this embodiment are arranged such that they terminate approximately at their upper side with the upper side of the bend 6. However, the top of the anchoring element 7 may generally be placed in an area extending between the top and the bottom of the bent strut of the bend 6. It is even possible positioning in which the top of the Anchoring element 7 is within a range which extends up to each of the thickness of the bend 6 on the top and bottom of the bent strut of the bend 6.

Fig. 1c illustrates in plan view how the anchoring element 7 is inserted between two transversely adjacent (possibly welded) bends 6 and welded to both. Incidentally, could also be in Fig. 1 or Fig. 2 more than one anchoring element may be mounted per bend or bend pair.

Although z. B. Fig. 1 the attachment of the anchoring elements 7 to the upper bends 6 of the diagonal strut coils 5, an embodiment would be possible, provided at the anchoring points on one or both lower sides of the lattice girder in an analogous manner by means of anchoring elements 7 to the lower bends 6 'omitting a continuous lower chord are.

In the embodiment in FIG Fig. 2a the or each diagonal strut coil 5 in opposite directions sloping or rising and falling struts 10, 11 and arranged on or between upper bends 6 anchoring elements 7 with recessed in the longitudinal direction intermediate spaces Z on. The upper side of the anchoring element 7, which is oriented at least approximately in the longitudinal direction, terminates approximately with the upper side of the bend 6.

In the embodiment in FIG Fig. 2b Contains the or each strut coil 5 only parallel to each other and the lower chords 4 vertically extending struts 12, at their trained in the manner of a rounded flat bow bends 6 anchoring elements 7 are attached.

In the embodiment in FIG Fig. 2c are, much like in Fig. 2b , mutually parallel struts 13 in the or each diagonal strut coil 5 are provided, which, however, extend obliquely relative to the lower chords 4 in the same direction. In the Fig. 2b and 2c are the struts 12, on the bend 6, the anchoring element 7 is arranged closer to each other in the longitudinal direction of the lattice girder than the struts 12, which are connected to each other via the lower bends 6 '.

The lattice beam embodiment chosen for the particular application depends on the desired optimization for the application. With regard to a high puncture resistance, diagonal struts which increase the load point of the flat ceiling must be aimed at. If the exact location of the load application point is not known or can vary, the embodiments of the Fig. 2a and 2b especially in question. A very high puncture resistance is in the embodiments of Fig. 2c or in the Fig. 1a to 1c given.

Fig. 3a to 3d illustrates different useful cross-sectional shapes of lattice girders 1, each at all or selected upper bends 6 with attached anchoring elements 7 approximately analogous to those of Fig. 1 are equipped.

In the Fig. 3a and 3b in each case only one diagonal strut coil 5 is associated with two transversely spaced, longitudinally extending lower chords 4. In Fig. 3a The diagonal strut coil initially extends in cross-section approximately in the center plane of the lattice girder down before it alternately bent to the left and to the right outside and fixed with the lower bends 6 'at the lower chords 4. In Fig. 3b At first, the diagonal strut coil 5 extends approximately vertically to the base of the lattice girder, where it is attached to a central longitudinally extending lower chord 4, from where the bends 6 'extend only to one side and the other lower chord 4. In the Fig. 3a and 3b are welded to the upper bends 6 on the outside each two approximately oriented in the longitudinal direction anchoring elements 7. As a result, despite only one diagonal strut coil 5, the anchoring rigidity is increased. However, with a correspondingly large anchoring element 7, one alone would suffice.

In the embodiment in FIG Fig. 3c two diagonal strut coils 5 extend approximately parallel to one another, which are fixed to the lower belts 4, which run relatively close to one another, while an anchoring element 7 is inserted between the upper bends 6. This embodiment may be advantageous if the load application point can lie to the left or right of the lattice girder and then both diagonal strut coils 5 are to take effect.

In the embodiment in FIG Fig. 3d the two diagonal strut coils 5 form an asymmetrical cross section, wherein an anchoring element 7 is installed between the upper bends 6. The asymmetrical cross-sectional shape results from the fact that the struts of the two diagonal strut coils 5 are inclined at different lengths or different obliquely. This embodiment may be advantageous if the position of the load application point is predetermined on one side of the lattice girder. There is then an approximately vertical diagonal strut coil and inclined to the load application point in the ceiling Diagonal strut coil, which are anchored above the anchoring element 7 together.

In the embodiment in FIG Fig. 4a to 4c the adjacent, possibly welded together, upper bends 6 of the two diagonal struts 5 are anchored by an anchoring element 15 which surrounds the bends 6 on three sides and z. B. is bent U-shaped from round steel. The anchoring element 15 may be welded at several points with the bends 6. The anchoring element 15 could also be a closed oval, which then encloses the two bends 6 on a total of four sides, for. Example, a closed oval of round steel similar to a chain link, or a flat squashed on both sides of a steel pipe.

In the embodiment of the lattice girder in the Fig. 5a to 5c is between the transverse to the longitudinal direction of the lattice girder adjacent to an intermediate distance, the upper bends 6 of the diagonal struts 5 each a wider anchoring element 16 is welded, which extends in the longitudinal direction of the lattice girder on both sides beyond the bend 6, and in the Fig. 5a to 5c the shape of a plate or a cuboid 17 has. As a result, a very large load introduction area is created, which may be in the size of five to ten times the rod cross-section to be anchored.

In the embodiments of the Fig. 5d and 5e is the respective anchoring element 18 and 19 in a side view similar to the anchoring element 16 in Fig. 5a or 5b formed, but with lateral extensions 18a and recesses 18b, so that there can nestle the upper bends 6, the top of the anchoring element 18 and 19 is at the level of the top of the bends 6, and yet a large load introduction area is offered. In the anchoring element 19, however, a widening 19a is formed on each side only at one end, and then a recess 19b on each side for nestling between the upper bends 6. The spacers 19a are suitably arranged on the side at which the struts 2 obliquely rise while the struts 3 fall relatively steep.

In the embodiments in the Fig. 4a to 4c and Fig. 5e is the respective anchoring element 15 and 19 in the longitudinal direction of the lattice girder substantially only on one side over the upper bend 6, whereby the installation of the upper Biegezugbewehrung is even less hindered.

In the embodiments of the Fig. 6a to 6c and Fig. 7a to 7c is the respective anchoring element 20 and 23 formed as a molded part made of steel or cast iron. In the Fig. 6a to 6c the molding is formed in plan view in the manner of a C-clamp with two side parts 22 and a lower central mandrel 21. The molding is transversely to the longitudinal direction of the lattice girder, ie laterally inserted into the bends 6 so that the central mandrel 21 is fitted in the bending of the bends 6 and the side members 22 abut the top adjacent to the apex of the bend 6. The top of the molding 20 terminates approximately at the top of the bend 6. The molding can only by positive engagement, z. B. be determined pressing, and / or secured by welding. The molded part 20 can be attached already at the factory lattice girder manufacture, or even later in an intermediate storage, in a precast plant, or even on the construction site.

For example, a standard lattice girder of its upper girth is discarded, and instead of the upper girth, moldings 20 can be attached to the bends 6 to make the lattice girder suitable for punching and / or shear force reinforcement or even only portions of the upper girth (s) are removed to form the gaps Z and the anchoring elements 7.

In the embodiment of the Fig. 7a to 7c is the anchoring element 23 z. B. according to Fig. 1 a molding, the z. B., alone by positive engagement, can transmit forces to the diagonal struts snakes 5, however, z. B. for security reasons, could also be welded firmly. The molded part has two spaced-apart side parts 25, between which a thinner middle part 24 extends below a recess 24a. The two diagonal struts 5 are inclined to each other above, so that the bends 6 abut each other or can be welded. The anchoring element 23 is inserted from below into the bends 6, so that the recess 24 a lies in the bending of the bends 6. The side parts 25 are brought next to the bends 6 to the top of the bends 6. Ends 25 'of the side parts 25 can be latched to the struts 3, for example.

The mold parts 23 and 20 are also suitable for use on only selected bends 6 z. B. in the immediate vicinity of the load introduction surface of a concrete slab.

Claims (12)

Lattice girder (1) for a transverse force and / or punching reinforcement of a ceiling, in particular a point-supported element or flat ceiling, wherein the lattice girder (1) at least one longitudinally continuous belt (4, 4a) and at least one on the at least one belt (4 , 4a) welded diagonal strut coil (5) with bends (6) between struts (2, 3, 10, 11, 12, 13), characterized in that in the lattice girder (1) at least one bend (6) of the respective diagonal strut coil ( 5) at least one anchoring element (7, 14, 15, 16, 17, 18, 19, 20, 23) designed as a shaped part with a limited dimension in lattice girder longitudinal direction is mounted such that anchoring elements succeeding one another in the longitudinal direction of the lattice girder (1) in each case a gurtfreier space (Z) provided and the anchoring element for introducing strut forces in the ceiling in the concrete of the ceiling is embeddable. Lattice girder according to claim 1, characterized in that in the lattice girder (1) above anchoring element whose top and placed in the lattice girder bottom anchoring element whose bottom is placed within a height range, either between the bottom and the top of the bent strut at the respective Bend (6) extends or maximally with the extent of the strength of the bent strut at the bend (6) over the top of the bend upwards and extends over the bottom of the bent strut at the bend down. Lattice girder according to claim 1, characterized in that the anchoring element is fixed non-positively on the bend, preferably by welding and / or latching. Lattice girder according to claim 1, characterized in that the anchoring element (7, 14, 16) an elongated round or flat steel section and at least substantially in the longitudinal direction of the lattice girder (1), preferably approximately parallel to a lattice girder base on or at least one Bend or welded between two bends. Lattice girder according to claim 4, characterized in that the length of the round or flat steel section corresponds approximately to three to eight times the seen in the vertical direction of the lattice girder strength of the round and flat steel section. Lattice girder according to claim 1, characterized in that the anchoring element (15, 16, 18, 19, 20, 23) is a cast steel or cast part which is associated with one or two bends (6) adjacent in the transverse direction of the lattice girder (1) is, preferably this bend or bends (6) on three to four sides surrounds. Lattice girder according to claim 6, characterized in that the molding for widening the load introduction surface at one or more locations widenings (18a, 19a). A lattice girder according to claim 3, characterized in that the anchoring element (29) formed as a shaped part is inserted in one or two adjacent bends (6) in the transverse direction of the lattice girder such that a middle mandrel (21) of the molding lies in the bending bend and two side parts (22) of the molding on outer sides of the bends (6) are arranged and terminate with their tops at least approximately at the top of the bends. A lattice girder according to claim 3, characterized in that the anchoring element (23) formed as a molded part is introduced from below into two adjacent bends (6) in their bends and fitted with a middle part (24, 24a) in the bending curve, and that side parts (25 ) of the molded part are positioned next to the bends (6) and extend with their tops at least approximately up to the height of the top of the bends (6). Lattice girder according to claim 1, characterized in that between the upper and lower bends (6, 6 ') of a diagonal strut coil (5) at least one in the longitudinal direction of the lattice girder (1) continuous center belt (4a) is arranged. Lattice girder according to claim 1, characterized in that in the longitudinal direction of the lattice girder (1) either vertical and inclined struts (2, 3) or exclusively vertical struts (12) or exclusively in the same direction and substantially mutually parallel struts (13) or only mutually oppositely inclined struts (10, 11) follow one another. A lattice girder according to claim 1, characterized in that the lattice girder (1) comprises either two spaced continuous lower chords (4) and a diagonal strut coil (5) whose upper bends (6) are aligned in the longitudinal direction of the lattice girder and whose lower bends (6 ') are either mutually connected to the lower chords (4), or whose lower bends (6') in the cross section of the lattice girder (1) are bent to only one side and connected to the lower chords (4), or the two spaced continuous lower chords ( 4) and two in cross section of the lattice girder (1) arranged approximately parallel diagonal struts snakes (5).

Images