EP0692574A1 - Road joint - Google Patents

Abstract

The spring elements (13) are formed as thrust springs. They have a parallelogram-shaped longitudinal section, when not under load, and are parallel to each other. When the lamellae (7,9) are in their closest position, the springs engage with their sides on the neighbouring lamellae The spaces between the lamellae are covered at the top by sealing bodies (8). The top end faces of the springs are located directly below the sealing bodies. Each lamella is formed conventionally as a double T-profile.

Description

The invention relates to a roadway transition for expansion joints in bridges or the like, with at least one lamella running parallel to the joint edges and a device for receiving the horizontal loads acting on the at least one lamella in the control direction, the distance of the at least one lamella from an adjacent lamella or a joint edge can be controlled via a compensating element designed as a spring element, the spring elements form a spring chain from one joint edge to the other and each spring element in a space between adjacent slats or between a slat and a joint edge in a position above the lower slat edge or lower slat edges is arranged and protrudes into lateral recesses of the slat (s) or the joint edges and is connected to them there.

In the case of lamella-roadway transitions, the derivation of the horizontal forces acting on the top of the lamellae in the transverse direction of the joint, which e.g. can result from vehicles crossing the carriageway, and securing the slats against tipping as a result of these horizontal forces is one of the greatest problems, since it is difficult to solve because of the required displaceability of the slats in the transverse direction of the joint.

It is known to use the compensation or control elements to secure the slats against tipping. Thus, in DE-PS 35 14 776 a roadway transition is described, the slats of which are slidably mounted on double-T-shaped traverses, in which elastic control bodies are also arranged displaceably on both sides of their vertical webs between the upper and lower flange. Each control body has two shear-deformable elastomeric blocks which are connected to one another by a common plate and are each connected to one of two adjacent lamellae or to one lamella or the adjacent edge of the joint via sliding plates lying on the flanges, so that a spring chain is formed. The control bodies are inserted under pressure preload between the upper flange and the lower flange. Due to the torsional resistance of the Elastomer blocks thus form the control bodies to effectively prevent the slats from tipping over, but the formation of the sliding surfaces and the necessary adjustment of the control bodies are complex and expensive. In addition, the position of the control bodies depends on the position of the crossbeams.

An arrangement of elastic control bodies outside the crossbars is known from DE-PS-35 18 944. Each control body here consists of two elastomeric blocks, each of which is connected to one another by a connecting plate dividing each block in the middle. On its top and on its underside, each control body is provided with rigid tabs which engage in extensions on the underside of the lamellae in order to take them transversely. Characterized in that the tabs of the control body exert horizontal forces on the extensions, these are held in their vertical position, whereby a restoring moment against tilting is exerted on the lamellae. This can be influenced in size by appropriately selecting the point of application of the tabs on the extensions of the slats, i.e. the greater the restoring torque is to be, the further this point of attack must be moved downward away from the slats. This type of arrangement of the control bodies is also complex to manufacture, since additional elements must be attached to the underside of the lamellae, on which the control bodies can act. In addition, the considerably increased overall height of the carriageway transition can lead to space problems in the generally small, available space, especially when, as described in DE-PS 35 18 944, for doubling the controlling thrust forces and the lever arms for the restoring torque against tilting two control bodies must be arranged one above the other.

A roadway crossing, in which the control bodies are arranged above the lower lamella edges, is described in DE-AS 25 12 048. The compensating or control bodies are generally elongated and run horizontally in each case between two lamellae or between a lamella and its adjacent joint edge. Each lamella has a vertical web and a horizontal, plate-shaped foot, the control bodies engaging the web of a lamella above the foot. The control bodies are expressly only intended as a compensating device to ensure uniform distances between the slats or between a slat and a joint edge. The lamellas are secured against tipping by their interaction with trusses designed as a double-T profile, whereby sliding bodies connected to the underside of the base of the lamellas slide on the upper and lower sides of the upper flange of the double-T profile. The cross section of the slat feet must be very wide and protrude above the slat heads Joint transverse direction in order to be able to absorb the tilting moment that occurs. However, this widening of the slat feet reduces the size of the movements that can be absorbed by the roadway crossing, since in its narrowest position there are already considerable distances between the tops of the slats. In addition, due to the formation of wide sliding surfaces, the manufacture of this solution is also relatively complex and, in addition, the possibility of absorbing tilting moments is already limited by the fact that the slat foot cannot be as wide as the slat head.

Here, the invention is to remedy the situation and improve a roadway transition of the latter type so that the safety of the slats against tilting is improved with a simple and space-saving construction.

According to the invention, this is achieved in a roadway transition of the type mentioned at the outset in that the spring elements are designed as thrust springs and at the same time are used as elements for deriving the horizontal loads acting on the at least one lamella.

In the carriageway transition according to the invention, an improved tipping of the slats is achieved in that the occurrence of large tipping moments is avoided from the outset. Since the spring elements arranged to control the spacing of the lamellas with one another or the distances between a lamella and a joint edge above the lower lamellar edges are used at the same time to derive the horizontal loads acting on the lamellas in the transverse direction of the joint, the horizontal loads are reduced almost where they occur in the Roadway crossing can be initiated, namely close to the top of the slats. This keeps the lever arm of the attacking horizontal load very low up to the point at which it is derived, and thus also the associated tilting moment. This constructive principle leads away from the previously known solutions. Because they all assume a relatively large tilting moment, as occurs when the horizontal force is only absorbed below the slats. With the magnitude of the tilting moment, however, the design effort that must be used to absorb this tilting moment also increases, such as, for example, applying a compressive prestress to the control bodies, shifting their point of attack downwards, widening the lamellar foot or the like. In complete contrast to this In the solution according to the invention, the path was taken not to let large tilting moments arise in the first place, but to keep the occurring tilting moments as small as possible right from the start, by also using the control elements which are present anyway and are arranged above the lower lamella edges at the same time in a very targeted manner to absorb horizontal loads, that directly attack the slats.

Since, according to the invention, the spring elements are also designed as thrust springs, it is possible to absorb large horizontal forces in a confined space, because this type of spring element allows relatively large deformations in relation to the space required. Due to the small space requirement of such spring elements between the lamellae or between a lamella and the edge of the joint, no wide space is required there and the overall width of the carriageway transition is kept small. The shear springs can consist of any suitable material, but shear springs made of an elastomeric material are preferably used, into which reinforcement inserts can also be vulcanized.

In the unloaded state, the spring elements are advantageously formed in the form of a parallelogram in a longitudinal section and are preferably arranged inclined to the control direction. With the narrowest position of the lamellae, the spring elements with their side faces are very particularly preferably in contact with an adjacent lamella or with a joint edge. Such a design and arrangement of the spring elements uses the entire available free space as spring travel and thus enables particularly large deformations in the smallest possible space. At the narrowest position of the carriageway crossing, i.e. at maximum shear deformation of the spring elements, this free space in the unloaded state is completely used up by the shear deformation, so that the spring element and lamellae or joint edge abut each other laterally. The available space is thus optimally used. The thrust spring can advantageously have the shape of a parallelepiped, which over two of its opposing rectangular surfaces e.g. is connected to adjacent slats or to a joint edge by means of suitable fastening plates. However, it can also be advantageous if the thrust spring takes the form of an oblique cylinder with e.g. has circular or elliptical cross section.

In a preferred embodiment of the invention, the spring elements are arranged essentially parallel to one another in the unloaded state. This means that the two spring elements acting on both sides of a lamella are attached to the lamella perpendicular to the control direction and offset from one another. With this design, small local eccentricities are introduced into the lamella by the horizontal forces, but the force components which are introduced by the thrust spring into the lamella and act perpendicular to the control direction cancel each other out and thus prevent corresponding, unwanted movements of the respective lamella.

However, an embodiment of the invention can also be preferred in which the two spring elements acting on both sides of a lamella relative to the longitudinal plane of the lamellae are arranged mirror-symmetrically. This avoids eccentricities in the transmission of the horizontal forces with respect to the plane of symmetry.

In both of the aforementioned embodiments, in a preferred arrangement of the spring elements, their connections to adjacent slats or to a slat and a joint edge can be offset from one another in the vertical direction. With this measure, a relatively high-level removal of the horizontal force is also achieved, since the connection of a spring element to a lamella or a joint edge extends horizontally in the longitudinal direction of the joint at a height level and thus the "resulting bearing force" of a spring element is also at this height level. In conjunction with lamellae designed as a double-T profile and the arrangement of connecting plates on the spring elements, their attachment to a lamella or to a joint edge is possible without great effort. Namely, the bottom connection plate can be attached to the top of the lower flange of a lamella, while the top connection plate of a spring element can be attached to tabs, which in turn are attached to the web of the double-T profile. The tabs can be welded to the web and screwed to the connecting plate, so that a very simple assembly and fastening of the spring elements is possible.

In a second preferred arrangement of the spring elements, their connections on adjacent slats or on a slat and a joint edge can be offset from one another in the longitudinal direction of the slats. With this arrangement of the spring elements, the connections of a spring element on a lamella or on a joint edge run in the vertical direction. The "resulting bearing force" of a spring element is therefore not as high as in the aforementioned solution, but here the horizontal loads at each connection point are derived or forwarded at the same height, since the connection elements of all spring elements are at the same height.

In a preferred development of the invention, the two spring elements acting on both sides of a lamella are fastened to this lamella at the same height. In this way, the horizontal forces absorbed by the spring elements are passed directly through the lamella to the respectively adjacent spring element without vertical offset until finally by a spring element that is attached to the joint edge, for example, be introduced into the abutment or the superstructure of a bridge. The slats are not additionally loaded in the vertical direction by local eccentricities.

Advantageously, in a roadway transition in which the spaces between a lamella and an adjacent lamella or a joint edge are covered at the top by sealing bodies, the spring elements with their upper end faces directly below the sealing bodies in the narrowest position of the lamellae. This arrangement ensures that the spring elements within the gaps between adjacent slats or between a slat and a joint edge are as high as possible under the sealing bodies, which means the distance between the point at which a horizontal force acts (top of the slat) and the point , from which this horizontal force is derived, is extremely low. As a result, the tilting moments that occur remain very small.

It is also advantageous if each lamella is designed in a manner known per se as a double-T profile, the web and the upper and lower flange of which define the lateral recesses. A double-T profile is relatively inexpensive as a standard product, so that its use keeps the manufacturing costs of a roadway crossing according to the invention low. Furthermore, the lateral recesses run through the entire length of a lamella and the arrangement of the spring elements is not subject to any local constraints.

Each spring element is preferably fastened via a connecting plate to adjacent slats or to a slat and a joint edge. A uniform introduction of the horizontal force into the shear spring is ensured by the connecting plates and thus their uniform shear deformation is also ensured.

• Fig. 1 einen Querschnitt durch einen erfindungsgemäßen, mehrlamelligen Fahrbahnübergang längs Linie I-I in Fig. 2, wobei eine Federkette in Nullstellung, d.h. im unbelasteten Zustand, dargestellt ist und die beiden beidseits einer Lamelle angreifenden Federelemente relativ zur Lamellen-Längsmittelebene spiegelsymmetrisch angeordnet sowie die beiden Anschlüsse jedes Federelements zueinander höhenversetzt sind;
• Fig. 2 eine Draufsicht auf einen Ausschnitt des Fahrbahnübergangs aus Fig. 1, wobei aus Gründen der Übersichtlichkeit Dichtungskörper nicht dargestellt wurden;
• Fig. 3 einen Schnitt längs Linie III-III durch den Fahrbahnübergang aus Fig. 1;
• Fig. 4 einen Querschnitt längs Linie IV-IV in Fig. 5 durch eine Ausführungsform eines erfindungsgemäßen Fahrbahnübergangs, die der in Fig. 1 gezeigten ähnlich ist, bei der jedoch die beiden Anschlüsse jedes Federelements in Lamellenlängsrichtung zueinander versetzt sind;
• Fig. 5 eine Draufsicht ähnlich Fig. 2 auf einen Ausschnitt des Fahrbahnübergangs aus Fig. 4,
• Fig. 6 einen Querschnitt ähnlich Fig. 1 oder 2 längs Linie VI-VI in Fig. 7 durch eine weitere Ausführungsform eines erfindungsgemäßen Fahrbahnübergangs, bei der die Federelemente im unbelasteten Zustand im wesentlichen parallel zueinander angeordnet sind;
• Fig. 7 eine Draufsicht ähnlich Fig. 2 oder 5 auf einen Ausschnitt des Fahrbahnübergangs aus Fig. 6.

The invention is explained in more detail below in principle on the basis of the drawing. Show it:

• Fig. 1 shows a cross section through a multi-lamella roadway crossing according to the invention along line II in Fig. 2, wherein a spring chain is shown in the zero position, ie in the unloaded state, and the two spring elements acting on both sides of a lamella are arranged in mirror symmetry relative to the lamella longitudinal center plane and the two Connections of each spring element are offset in height from each other;
• FIG. 2 shows a plan view of a section of the carriageway transition from FIG. 1, sealing bodies not being shown for reasons of clarity;
• 3 shows a section along line III-III through the carriageway transition from FIG. 1;
• 4 shows a cross section along line IV-IV in FIG. 5 through an embodiment of a roadway crossing according to the invention, which is similar to that shown in FIG. 1, but in which the two connections of each spring element are offset with respect to one another in the longitudinal direction of the lamellae;
• 5 is a plan view similar to FIG. 2 of a section of the carriageway crossing from FIG. 4,
• 6 shows a cross section similar to FIG. 1 or 2 along line VI-VI in FIG. 7 through a further embodiment of a roadway crossing according to the invention, in which the spring elements are arranged essentially parallel to one another in the unloaded state;
• 7 is a plan view similar to FIG. 2 or 5 of a section of the carriageway crossing from FIG. 6.

The roadway transitions 1, 2 and 3 shown in the figures each extend between two joint edges e.g. a bridge construction. On both sides of the joint, the top of the superstructure is provided with a suitable seal 4, above which a road surface 5, e.g. Concrete is attached, which forms a surface 6.

The structure of the carriageway transitions 1, 2 and 3 has lamellae 7 running within the expansion joint in the longitudinal direction of the joint and parallel to the joint edges, which are connected to one another via suitable elastic sealing bodies 8, each of which bridges the gap formed between the lamellae 7 in a watertight manner. The edge lamellae are also positively connected to steel profiles 9 attached to the joint edges via such elastic sealing bodies 8.

Each lamella 7 is designed as a double-T profile with an upper flange 10 and a lower flange 11, the flanges 10 and 11 lying horizontally and the upper side of the upper flange 10 being flush with the surface 6 and thus forming part of the driving surface . The dimensions of the upper and lower flange 10, 11 of a lamella 7 are the same in the transverse direction of the joint, that is to say in the horizontal direction, so that the distances 12 in the transverse direction of the joint between the upper and lower flanges 10, 11 of adjacent lamellae 7 are of the same size . The edge profiles 9 of the joint edges have on their side facing the slats 7, except for the absence of a lower flange, essentially the same profile as the slats 7, a console 14 being welded to the edge profile 9 instead of the lower flange for connecting a spring element 13 that are about the same Dimension of the edge profile 9 protrudes like the lower flange 11 of a lamella 7 from its web 15. Thus, even between a lamella 7 and the edge profile 9 of a joint edge, the horizontal distance of the upper flanges 10 is equal to the distance of the lower elements, namely the lower flange 11 the lamella 7 and the bracket 14 welded to the edge profile 9. Slightly below the underside of the upper flange 10, L-shaped angle profiles 16 opposite each other are fastened on both sides of the web 15 of a lamella 7 with their long legs, the angle profiles 16 extend in the transverse direction of the joint somewhat less than the flanges 10, 11 so that they are set back somewhat towards the inside of the profile. Correspondingly, the edge profiles 9 of the joint edges are also provided with such angle profiles 16. One leg of a sealing body 8 is clamped between the angle profile 16 and the upper flange 10 and covers the space underneath in a watertight manner. Below the sealing body 8, a spring element 13 is arranged in the space between two adjacent slats 7 or an edge slat and a joint edge above the top of the lower flanges 11 of the slats 7, which is designed as a shear spring and a spring chain from one joint edge to the other form. The spring elements 13 consist of an elastomeric material and, in the unloaded state, have the shape of a parallelepiped, ie in the unloaded state they run inclined to the control direction. A parallelepiped is relatively easy to manufacture and also extremely compact. Large deformation paths can be realized in the tightest of spaces and the flat surfaces of a parallelepiped offer easy access for connection to a lamella 7 or a joint edge. Thus, in the exemplary embodiments shown, each parallelepiped is provided on two of its opposite rectangular sides with a connecting plate 17, 18; 17a, 18a. The two other mutually opposite rectangular side faces 27 of the parallelepiped face the adjacent lamellae 7 or a lamella 7 and a joint edge, the edge 27a of such a side surface 27 closest to a lamella 7 or a joint edge and running perpendicular to the control direction directly on the opposite side thereof Lateral surface 26 of the lamella 7 or of the joint edge lies and the other edge 27b of the side surface 27 of the parallelepiped, which runs parallel to the edge 27a, is arranged at a distance from the side surface 26 of the lamella 7 or of the joint edge which is equal to the maximum shear deformation of the spring element is. At the connection point of a spring element 13 to a joint edge, an anchoring 19 is provided in the surrounding concrete 20 to absorb horizontal forces.

1 to 3, the connection plates 17, 18 protrude beyond the spring element 13 in the longitudinal direction of the joint. The lower connection plate 17 lies on the top of the lower flange 11 of a lamella 7 or the bracket 14 of an edge profile 9 and is connected to this or this, for example, by a screw connection. On the underside of the lower connecting plates 17, a recess 21 is provided on the side facing the lower flange 11 of the adjacent lamella 7, so that when the carriageway transition 1 is pushed together, ie when the distances 12 in the transverse direction of the joint between the lamellae 7 or one Edge lamella 7 and a joint edge become smaller, the underside of a lower connecting plate 17 can slide over the top of the lower flange 11 of the adjacent lamella 7 with sufficient safety clearance. In this way, an unimpeded pushing together of the carriageway 1 is ensured up to its narrowest position. To connect the upper connecting plate 18 of a spring element 13 to a lamella 7, two tabs 22 are welded to its web 15, which are aligned horizontally in the transverse direction of the joint and spaced apart from one another in the longitudinal direction of the joint. (Figs. 1 and 3). The upper connection plate 18 lies on the tabs 22 and is screwed to them, for example. The spring element 13 is located between the tabs 22. In a similar way, such tabs 22 can be attached to the edge profile 9 of a joint edge if an upper connecting plate 18 has to be fastened there (see FIG. 6). The distances in the control direction between a connecting plate 17, 18 and also between the mentioned tabs 22 and the opposite web 15 of the adjacent lamella 7 or the adjacent joint edge are at least as large as the maximum shear deformations of the spring element 13, so that the narrowest joint position is reached the carriageway crossing 1 is guaranteed.

The two spring elements 13, which act on both sides of a lamella 7, are arranged in mirror symmetry relative to the longitudinal plane of the lamellae, that is to say their angles of inclination to the control direction are of equal magnitude, but are oriented in opposite directions. The lower or upper connecting plates 17, 18 engaging the same lamella 7, each of two adjacent spring elements 13, lie opposite one another in the longitudinal direction of the joint and also at the same height, ie in the vertical direction, on the web 15 of the lamella 7. With this arrangement, no local eccentricities are introduced into the slats 7, but rather the shear forces present in the spring elements 13 during shear deformation via the connecting plates 17, 18 as pure pressure or tensile forces through the web 15 or the lower flange 11 of the respective slat 7 passed through and released into the edge profiles 9 at the joint edges. Since the upper connection plates 18 can be arranged as high as possible, that is, in the extreme case so high that their upper end surfaces just touch the downwardly deformed sealing body 8 when the carriageway transition 1 is pushed together, the horizontal force which can be exerted, for example, into the upper side the upper flanges 10 of the slats 7 induced braking forces caused by motor vehicles, is removed at a short distance from the top will. In this way, the occurrence of larger tilting moments is avoided by absorbing horizontal forces occurring on the top of the slats 7 with a small lever arm and dissipating them into the edge structures of the carriageway transition 1. It can also a tilting moment via a rigid connection of the upper connection plate 18 to the web 15 or to the edge profile 9 and via a likewise rigid connection of the lower connection plate 17 to the lower flange 11 of the lamella 7 or to the bracket 14 fastened to the edge profile 9 are recorded, depending on the degree of torsional rigidity of the spring elements 13.

The embodiment of the invention shown in Figures 4 and 5 corresponds with respect to the arrangement of the spring elements 13 to each other the road transition, as shown in Figs. 1 and 2, but the spring elements 13 are tilted by 90 ° so that the connecting plates 17a , 18a of the spring elements 13 are offset from one another in the longitudinal direction of the joint. Both connection plates 17a, 18a of a spring element 13 lie with a horizontal narrow side 23 on the lower flanges 11 of the slats 7 or on the brackets 14 fastened to the edge profiles 9 and are mainly with a vertically extending narrow side 24, e.g. attached to the web 15 of the corresponding lamella 7 or the corresponding edge profile 9 via a weld seam. In this exemplary embodiment, the spring elements 13 themselves can also be offset from one another in the longitudinal direction of the joint. It is only important that the connection plates 17a, 18a, each engaging the same lamella 7, are directly opposite one another in the control direction with respect to this lamella 7.

The spring elements 13 can also be arranged essentially parallel to one another in the unloaded state, as is shown in the case of vertically offset connecting plates 17, 18 (see FIGS. 1 and 2) in FIGS. 6 and 7. Such a "sawtooth arrangement" is also conceivable, however, for connection plates 17a, 18a which are offset with respect to one another in the longitudinal direction of the joint (cf. FIGS. 5 and 6). The disadvantage of introducing local eccentricities into the lamellae is offset by the mutual cancellation perpendicular to the control direction in the lamellae 7 by force components introduced by the spring elements 13.

It is also provided that the spring elements of immediately successive spring chains are arranged in opposite directions to one another, so that, for example in an arrangement according to FIGS. 1 and 2, the height positions of the connections of the spring elements acting on the same lamella of adjacent spring chains alternate in the longitudinal direction of the lamellae. It is also intended, in the case of spring elements arranged parallel to one another in the spring chains (FIGS. 6 and 7), to reverse the inclination of the spring elements of immediately adjacent spring chains choose. This measure ensures that forces introduced by the spring elements into the lamellae and directed perpendicular to the control direction balance out over the lamella length, so that the lamellae are held securely in their desired position.

In all of the exemplary embodiments described, the spring elements rest with their side surfaces on adjacent slats or a slat and a joint edge when the slats are in the narrowest position. The space between the slats or between a slat and a joint edge is thus optimally used for the shear deformation, which makes the overall width of the carriageway transition particularly small.

Claims (10)

Roadway transition for expansion joints in bridges or the like, with at least one lamella running parallel to the joint edges and a device for absorbing the horizontal loads acting on the at least one lamella in the control direction, the distance of the at least one lamella to an adjacent lamella or a joint edge over one a compensating element designed as a spring element is controllable, the spring elements form a spring chain from one joint edge to the other and each spring element is arranged in a space between adjacent slats or between a slat and a joint edge in a position above the lower slat edge or the lower slat edges and in lateral recesses of the lamella (s) or the joint edges protrude and are connected there, characterized in that the spring elements (13) are designed as thrust springs and at the same time as elements for deriving the at least one lamella e (7) attacking horizontal loads are used. Roadway crossing according to claim 1, characterized in that the spring elements (13) are formed in the longitudinal section in the unloaded state in the form of a parallelogram. Roadway crossing according to claim 2, characterized in that the spring elements (13) are arranged inclined to the control direction in the unloaded state. Roadway crossing according to one of claims 1 to 3, characterized in that when the slats (7) are in the narrowest position, the spring elements (13) each rest with their side faces on an adjacent slat (7) or on a joint edge. Roadway crossing according to one of claims 2 to 4, characterized in that the spring elements (13) are arranged essentially parallel to one another in the unloaded state. Roadway crossing according to one of claims 2 to 4, characterized in that the two spring elements (13) acting on both sides of a lamella (7) are arranged mirror-symmetrically relative to the longitudinal plane of the lamella. Roadway crossing according to one of claims 1 to 6, characterized in that the two spring elements (13) acting on both sides of a lamella (7) are fastened to this lamella (7) at the same height. Roadway crossing according to one of Claims 1 to 7, in which the spaces between a lamella and an adjacent lamella or a joint edge are covered at the top by sealing bodies, characterized in that the spring elements (13) with their upper positions when the lamellae (7) are in the narrowest position End surfaces are located immediately below the sealing body (8). Roadway crossing according to one of claims 1 to 8, characterized in that each lamella (7) is designed in a manner known per se as a double-T profile, the web (15) and the upper and lower flange (10, 11) of which define lateral recesses. Roadway crossing according to one of claims 1 to 9, characterized in that each spring element (13) is in each case attached to adjacent slats (7) or to a slat (7) and a joint edge via a connecting plate (17, 18; 17a, 18a) .

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