DE102018124650A1 - Network arch bridge with hangers made of fiber composite material - Google Patents

Abstract

A network arch bridge is proposed, the hangers of which are made of fiber composite materials. Due to the significantly different mechanical properties of these hangers compared to steel beams, the geometry of the network can be designed differently and more efficiently.

Description

A rod arch bridge with sloping, intersecting hangers is called a network arch bridge. A very popular example of a network arch bridge in Germany bridges the Fehmarnsund and has connected the island of Fehmarn to the mainland for about 50 years.

In the case of network arch bridges, the arch and superstructure, together with the inclined and crossed hangers, form an arch disc with an upper chord, lower chord and infill. The terms "bow" and "top flange", "superstructure" and "bottom flange" are used synonymously in connection with the invention.

In contrast to the rod arch with a few vertical hangers, the network bow has a shear-resistant coupling between the top flange and bottom flange due to the large number of inclined hangers. When the load is affine to the arch shape (load only generates normal forces in the arch and no bending, neither in the arch nor in the superstructure; e.g. uniform distance load in the case of a parabolic arch), the global load-bearing behavior between the network arch and the rod arch differs insignificantly. In the case of a rod arch, depending on the stiffness distribution, the arch and the superstructure are subjected to a proportionate amount of bending in the case of a non-arch-related load (single heavy load or superstructure which is only loaded in sections / areas). The deformations under non-affine load are therefore dependent on the bending stiffness of the arch and superstructure. In the case of the network arch, the push field consisting of crossed, inclined hangers is activated in the case of non-affine loading, whereby individual hangers are additionally loaded and other hangers are relieved. Both the arch and the superstructure are only loaded with normal forces (pressure and tension). As a result, the loads from traffic can be transferred very efficiently with minimal deformation. With the same load, the deformations (deflections) are much smaller than with a normal rod arch due to the stiffening network of crossed hangers. Among other things, this slight deformation makes this type of bridge particularly interesting for railways in the heavy-duty and high-speed sector.

Due to this global carrying behavior of the hangers, configurations with an arched up superstructure (top of a gradient to transfer an obstacle) can also be realized with network arches.

To put it simply, the hangers on the arch bridge only have to transfer the part of the superstructure's load that is near a hanger upwards to the arch. With the network arch bridge, the sloping hangers are also used for global load transfer; For example, in the case of a half-sided load, the hangers falling to the loaded side are also activated in the unloaded half in order to remove the non-affine load portion. At the same time, the hangers rising towards the loaded side are relieved. Therefore, the amplitudes of the load changes (changes in the load on a trailer, e.g. when a train passes over it) are significantly larger than those of arched bridges.

Network arch bridges are currently experiencing a renaissance due to the very positive properties of the overall structure.

Compared to conventional arch bridges with vertical hangers, both the arch and the superstructure can be made much slimmer, since both stiffen each other via the crossed hangers. This leads to considerable material savings and a narrower silhouette.

The aspect of fatigue resistance is dimensionally relevant for the hangers of network arch bridges made of steel. This has resulted in the arrangement of the hangers being optimized in some of the examples mentioned last so that the amplitudes of the load changes are kept as low as possible. On the one hand, this leads to long and very flat hangers. These long hangers have adverse properties in terms of wind-induced vibrations and assembly. In addition, the uniform image of the network hangers is visibly disturbed by these adjustments in the area near the base of the arch.

The flexibility in choosing a suitable hanger layout is significantly restricted by the technical boundary conditions for steel hangers. The maximum achievable spans for this type of bridge are currently limited in the case of steel trailers by the technical challenges associated with the design and design of the trailers.

• - Hohe Amplitude der Lastwechsel (Schwingbreiten) aus Verkehrslasten beeinflusst das Layout der Hänger und damit das gesamte System,
• - Begrenzung der maximalen Spannweite für welche dieser Brückentypus mit Stahlhängern gegenwärtig technisch möglich und wirtschaftlich sinnvoll eingesetzt werden kann.
• - Durch Wind hervorgerufenen Schwingungen wie wirbelerregte Schwingungen quer zum Wind, Regen-Wind-induzierte Schwingungen oder Gallopping-Schwingungen führen in Überlagerung mit den Ermüdungslasten aus Verkehr zu weiterer Schädigung der Hänger und deren Anschlüssen und in Folge dessen zu einer Verkürzung der Lebensdauer.
• - Insbesondere bei langen flach geneigten Hängern wirken sich Effekte aus der Durchbiegung unter Eigengewicht problematisch aus. Bei der Montage von eingeschweißten Hängern aus Stahl können eingeprägte Eigenspannungszustände zu Problemen führen.

Network arches with hangers made of steel therefore have the following disadvantages:

• - High amplitude of the load changes (swing widths) from traffic loads influences the layout of the trailer and thus the entire system,
• - Limitation of the maximum span for which this type of bridge with steel hangers can currently be used technically and economically.
• - Vibrations caused by wind, such as vortical vibrations across the wind, rain-wind-induced vibrations or gallopping vibrations result in Overlay with the fatigue loads from traffic to further damage the trailers and their connections and, consequently, to shorten the lifespan.
• - Especially with long, flat inclined hangers, effects from bending under their own weight are problematic. When assembling welded steel hangers, impressed residual stresses can lead to problems.

The object of the invention is to provide a network arch bridge which avoids these disadvantages or at least significantly reduces them. In addition, an economically highly optimized trailer layout is to be provided and the areas of application of network arch bridges are to be significantly enlarged. At the same time, it should meet the highest standards of efficiency and aesthetics.

This object is achieved according to the invention in the case of a network arch bridge comprising a lower chord (roadway), one, two or more arch-shaped upper chords, each with several oblique, mutually intersecting hangers, in that the hangers are made of a fiber composite material.

• Hänger aus Faserverbundwerkstoffen, insbesondere Carbon, sind unempfindlich gegen Versagen durch Materialermüdung. Dadurch kann das erfindungsgemäße Layout der Hänger unter dem Gesichtspunkt der maximalen Belastung der Hänger ohne Rücksicht auf deren Amplituden der Lastwechsel (Schwingbreiten) festgelegt werden.

This has the following advantages:

• Hangers made of fiber composite materials, especially carbon, are insensitive to failure due to material fatigue. As a result, the layout of the hangers according to the invention can be determined from the point of view of the maximum load of the hangers regardless of their amplitudes of the load changes (swing widths).

The layout of the network arch according to the invention leads to a significant reduction in the maximum load on the individual hangers. In contrast, the hanger layout of previous network arches is mostly based on how the amplitudes of load changes (swing widths) are kept as low as possible. The result is a different network of hangers: the hangers according to the invention run significantly steeper, cross less frequently, are altogether approx. 20% shorter (since they are less inclined) and can also be arranged much more evenly without individual hangers nearby to place excessive strain on the arch base.

Due to the low weight of the hangers according to the invention, their dynamic properties change. This is particularly noticeable through a significantly higher first natural frequency, a much smaller modal mass and smaller cross-sectional dimensions. Some of the known wind-induced vibration phenomena cannot occur in the hangers according to the invention. The damping of any wind-induced vibrations that may occur can, however, be regarded as an option for the trailers, since no longer life-reducing damage can be expected for the trailers. If damping measures are required or desired in individual cases, a very small damper mass is sufficient due to the low weight of the trailer. In addition, there is in principle the possibility of choosing the cross-sectional shape of the hangers according to aerodynamic aspects.

There is a risk with network arch bridges with steel hangers. that individual hangers fail when the bridge is loaded from one side and that they are now subjected to pressure instead of being pulled. A half-sided load always occurs when e.g. the bridge is loaded from one end to the middle of the bridge. The hangers on the unloaded half of the bridge are relieved, which run downwards from the loaded side to the superstructure (hangers falling away from the loaded area).

Hangers made of fiber composite materials, especially carbon ropes, have a lower stiffness due to the higher utilization of the cross section and the comparatively small elasticity module. This means that the elongation in the trailer is greater with the same load. This has the advantage in the arch bridge according to the invention that (with half-sided loading of the bridge) the tensile stress in the hangers decreases with the same shortening of the hanger (due to the relief) than with steel hangers. In cases where the tension on a steel hanger has already been completely reduced (the hanger has "failed"), a correspondingly dimensioned hanger made of a fiber composite material is still under tension. This property, together with the above-mentioned changed geometry (steeper hangers with fewer intersections), enables the optimized, highly efficient and flexibly selectable hanger arrangements according to the invention.
Due to the arrangements of the geometry according to the invention, the maximum forces acting on the hangers can be reduced by approximately 30%. This in turn allows the hangers of fiber composite materials according to the invention to be made even thinner, which in turn has a positive effect with regard to wind-excited vibrations and hanger failure. In addition, the connections of the hangers to the arch and superstructure can be dimensioned for lower forces.

The hangers according to the invention weigh less than 20%, usually only about 10%, of a comparable sized hanger made of steel. This great weight advantage facilitates assembly and, if necessary, installation / removal for maintenance purposes. In addition, the hangers according to the invention are interchangeable, which results in far-reaching simplifications in the manufacture and maintenance of the bridge. For bridges with a span of up to around 100m, it can be assumed that the trailers can be moved and assembled by hand without the aid of lifting equipment.

Fiber composites, especially carbon, are insensitive to atmospheric influences. Corrosion and its consequences (stress corrosion cracking etc.) cannot occur. This in turn increases the durability of the trailer and the bridge and significantly reduces the monitoring and maintenance work for the trailer.

In a first embodiment of the network arch bridge according to the invention, the longitudinal axes of the hangers close a constant angle with a line that is orthogonal to a tangent of the upper chord at the intersection between the upper chord and the hanger α on. In a preferred embodiment it is provided that the constant angle α is less than or equal to 36 °.

As a result, relatively short hangers are realized, which has a positive effect on the rigidity of the network arch. Because the trailers are relatively short, their first natural frequency is also comparatively high, which in turn further reduces the tendency to wind-induced vibrations.

In an advantageous embodiment of the invention, the distance between the intersection points of two adjacent hangers with the upper flange is constant. This has advantages in terms of the stiffening effect of the network of hangers. At the same time, the manufacture of the top chord is simplified.

In a particularly advantageous embodiment according to claim 6, the longitudinal axes of the hangers close different angles with a line that is orthogonal to a tangent of the upper chord at the intersection between the bow and the hanger α one, the angle α become smaller towards the base of the arch for the flatter inclined hangers. This fundamentally contradicts the optimization approach currently used for steel hangers, with the angles currently α towards the base of the arch should be chosen larger for the gently sloping hangers.

In a further advantageous embodiment of the second embodiment, it is provided that a distance B between the intersection of adjacent hangers and the top chord to the arch base ( FP ) is reduced.

This means that the number of hangers in relation to the length of the top flange increases in the area of the base points of the top flange. Depending on the design and rigidity of the connection between the arch and the superstructure, a more even utilization of the hangers can be achieved.

It has proven to be advantageous if the hangers are made from a fiber composite material that contains carbon fibers. Carbon fibers have a number of mechanical properties which have a favorable effect on the network arch bridge according to the invention. A very important property is that the elastic modulus of carbon fibers relative to steel can be chosen to be significantly lower. It can be controlled in a wide range through the selection of carbon fibers.

It has also proven to be advantageous if the elastic modulus of the hanger is less than 150,000 N / mm ² , preferably less than 130,000 N / mm ² . This makes the hangers relatively soft.

In other words: To achieve the desired pretension, the hangers have to be stretched relatively much. As a result, in particular if a bridge is only loaded on one side, the hangers falling away from the loaded area do not fail, but are always under tension.

In a further advantageous embodiment, it is provided that rails for one or more tracks and / or carriageways for cars and trucks are provided on the superstructure.

Further advantages and advantageous embodiments of the invention can be found in the following drawing, its description and the patent claims. All of the features disclosed in the drawing, its description and the patent claims can be essential to the invention both individually and in any combination with one another.

Figure list

• 1 eine Seitenansicht eines ersten Ausführungsbeispiels einer erfindungsgemäßen Netzwerkbogenbrücke,
• 2 das Ausführungsbeispiel gemäß 1, wobei nur eine erste Gruppe von Hängern dargestellt ist,
• 3 das Ausführungsbeispiel gemäß 1, wobei nur die zweite Gruppe von Hängern dargestellt ist,
• 4 ein zweites Ausführungsbeispiel einer erfindungsgemäßen Netzwerkbogenbrücke,
• 5 die Seitenansicht gemäß 4, wobei nur eine erste Gruppe von Hängern dargestellt ist,
• 6 das Ausführungsbeispiel gemäß 4, wobei nur die zweite Gruppe von Hängern dargestellt ist, und
• 7 verschiedene Querschnitte durch die erfindungsgemäßen Netzwerkbogenbrücken gemäß 1 und 4.

Show it:

• 1 2 shows a side view of a first exemplary embodiment of a network arch bridge according to the invention,
• 2nd the embodiment according to 1 , showing only a first group of hangers,
• 3rd the embodiment according to 1 , showing only the second group of hangers,
• 4th a second embodiment of a network arch bridge according to the invention,
• 5 the side view according to 4th , showing only a first group of hangers,
• 6 the embodiment according to 4th , showing only the second group of hangers, and
• 7 different cross sections through the network arch bridges according to the invention 1 and 4th .

Description of the embodiments

Based on 1 to 3rd describes a first embodiment of a network arch bridge according to the invention with hangers made of fiber composite material.

The 1 shows a side view of a first embodiment of a network arch bridge according to the invention. The 2nd and 3rd are reduced representations of the same embodiment in which only one group of hangers is shown for reasons of clarity.

The network arch bridge includes a lower chord 1 and an arched top chord 3rd that at foot points FP _r and FP _l with the lower flange 1 connected is. The top chord 3rd is symmetrical here with respect to a line of symmetry S chosen. The high point of the upper chord is in the middle between the base points FP _r and FP _l , where the line of symmetry S cuts the top chord.

Between the lower flange 1 and the top chord 3rd are two groups of hangers 7 stretched, which according to a first approximation diamond-shaped network in the side view 1 form.

In order to better illustrate the geometric properties of the network, the 2nd and 3rd only one group of 19 followers each 7 drawn. The second group of hangers 7 corresponds to the first group of hangers 7 , but around the axis of symmetry S mirrored.

In the 2nd are some hangers 7 with a running index 1 provided to n. For reasons of clarity, however, not all hangers 7 provided with reference numerals and a running index. All in all in the 1 and 2nd illustrated embodiments 2 x 19 hangers 7 between the top chord 3rd and the lower flange 1 tense. The intersections between the hangers 7 and the top chord are included SP ₁ to SP _n designated.

In the 2nd and 3rd are arrows BR registered. The abbreviation " BR “Stands for line of sight. If a person is at the left foot point FP _l stands and in line of sight BR to the right foot point FP _r look, then those in the 2nd shown hanger 7 referred to as falling hangers.
The in the 3rd shown hanger 7 are accordingly referred to as rising hangers.

If you look at the intersections SP ₁ between the hangers 7 ₁ and the top chord 3rd an orthogonal is built on the tangent of the upper chord, then this orthogonal closes with the longitudinal axis of the first hanger 7 ₁ an angle α on. In the illustrated embodiment, the angle is α 35 °. Examples are at the tenth intersection SP ₁₀ and at the intersection SP _n the angles α ₁₀ respectively. α _n also drawn in to illustrate that in this embodiment of a network arch bridge according to the invention all angles α1 to αn are the same; is in the illustrated embodiment α equal to 35 °.

Another important geometric characteristic of the first embodiment is that the distance B between the intersections SP two adjacent hangers 7 and the top chord 3rd is constant. That means for example the width B between the intersections SP _n-2 and the intersection SP _n-1 is the same size as the distance between the intersections SP ₁ and SP ₂ .

If you put that in 2nd shown hanger 7 the first group from the 2nd by 180 ° around the line of symmetry S turns, then you get that in the 3rd shown second group of hangers 7 . In other words, the relative location of the in 3rd hanger shown on the right with respect to the line of symmetry S corresponds to that in 2nd Hangers shown on the left 7 ₁ .

In the 1 are both groups of followers 7 , which together form the network according to the invention, are shown together.

Such a network has significant advantages in terms of the maximum load on the hangers of the network. These advantages are explained in detail above in the introduction to the description. In particular, the angles α be relatively small, namely less than 41 °, preferably even less than 36 °. This causes the hangers 7 are shorter, the load distribution is particularly favorable and the susceptibility to wind-induced vibrations is also reduced.

Based on 4th to 6 describes a second embodiment of a network arch bridge according to the invention with hangers made of fiber composite material. Both exemplary embodiments have a large number of similarities, which are shown in FIGS 3rd to 6 not explained again will. Rather, what has been said regarding the first exemplary embodiment applies accordingly.

The 4th shows a side view of the second embodiment of a network arch bridge according to the invention. The 5 and 6 are reduced representations of the same embodiment in which only one group of hangers is shown for reasons of clarity.

Between the lower flange 1 and the top chord 3rd are two groups of hangers 7 stretched, which according to a first approximation diamond-shaped network in the side view 4th form.

In order to better illustrate the geometric properties of the network, the 5 and 6 only one group of 19 followers each 7 drawn. The second group of hangers 7 corresponds to the first group of hangers 7 , but around the axis of symmetry S mirrored.

In the 5 are some hangers 7 with a running index 1 provided to n. For reasons of clarity, however, not all hangers 7 provided with reference numerals and a running index. There are a total of 2 x 19 hangers 7 between the top chord 3rd and the lower flange 1 tense. The intersections between the hangers 7 and the top chord 3rd are with SP ₁ to SP _n designated.

The angle α ₁ between an orthogonal on the tangent of the top chord 3rd at the intersection SP ₁ between the hangers 7 ₁ and the top chord 3rd is again reduced to 16 ° in this embodiment; depending on the stiffness of the arch base point (stiffness of the connection between arch and superstructure and the two components themselves), it can be chosen as small as desired, values between 10 ° and 20 ° being advantageous in many cases.

The angle increases towards the center of the arch α ₁ from hanger to hanger to (α ₂ > α ₁ ; α ₃ > α ₂ , ...). In this embodiment, the angle ( α ₆ of the sixth trailer 7 ₆ equal to 35 °. After that, the angle remains α constant.

The same applies to the second group of hangers, which in 6 is shown.

From the base of the arch ( FP ) the distance to the middle of the arch also increases B between the intersections SP two adjacent hangers 7 and the top chord 3rd marginally. In an advantageous embodiment, the first distance is B between the intersections SP of the first and second hangers 7 and the top chord 3rd between 75% and 85% of the distance B in the middle of the arc, where the distance B is constant in a range from 50% to 70% of the arc length. That means for example the width B between the intersections SP _n-2 and the intersection SP _n-1 is the same size as the distance between the intersections SP ₅ and SP ₆ .

If you put that in 2nd shown hanger 7 the first group from the 2nd by 180 ° around the line of symmetry S turns, then you get that in the 3rd shown second group of hangers 7 .

In the 4th are both groups of followers 7 , which together form the network according to the invention of the second exemplary embodiment.

The networks according to the invention have considerable advantages with regard to the maximum forces occurring in the hangers and the uniformity of the use of the hangers. These advantages are explained in detail above in the introduction to the description. In particular, the angles α be relatively small, namely less than 41 °, preferably even less than 36 °. This causes the hangers 7 are shorter, the load distribution is particularly favorable and the susceptibility to wind-induced vibrations is also reduced.

As already explained in connection with the introduction to the description, the hangers of the network arch bridge according to the invention are made of a fiber composite material, preferably containing carbon fibers. Because carbon fibers have a very high tensile strength, but at the same time have a relatively small modulus of elasticity, they can be made significantly steeper. They cross less frequently and are about 20% shorter overall. They can also be arranged more evenly without placing individual hangers near the base FP of the bow are overloaded.

To avoid repetition, please refer to the introduction to the description.

In the 1 to 6 are the supports 9 , which carry the arch network, shown schematically.

In the 7 different sections through different possible embodiments of the network arch bridge according to the invention are shown. In the section according to a), the network arch bridge has the shape of a trapezoid. Two vehicle lanes are provided. In the exemplary embodiment according to FIG. B), the two network arches are arranged parallel to one another. The embodiment according to c ) shows a cross section through a network arch bridge with a single-track rail path. In addition, network arch bridges with only one centrally arranged arch or several arch levels are possible.

In the embodiment according to 5d ) the network arches are again arranged parallel to each other and spaced so far apart that two tracks can be arranged next to each other.

Claims (12)

Network arch bridge comprising at least one network arch, consisting of a lower flange (1), at least one arch-shaped upper flange (3) and several inclined hangers (7) which intersect several times, characterized in that the hangers (7) are made of a fiber composite material. Network arch bridge after Claim 1 , characterized in that the longitudinal axes of the hangers (7) form a constant angle (α) with a line orthogonal to a tangent of the upper belt (3) at the intersection (Sp) between the upper belt (3) and the hanger (7) lock in. Network arch bridge after Claim 1 , characterized in that a distance (B) between the intersection points (SP _i , SP _{i + 1} ) of adjacent hangers (7 _i , 7 _{i + 1} ) and top flange (3) are constant. Network arch bridge after Claim 1 , characterized in that the longitudinal axes () of the hangers () with a line that is orthogonal to a tangent () of the upper flange () at the intersection (SP) between the bow (3) and the hanger (7), different angles (α ) include that the angle (α) of the falling hangers begins near a base point (FP) with an angle (α) smaller than the angle (α) in the middle of the arc and increases steadily to a constant angle (α). Network arch bridge according to one of the preceding claims, characterized in that the angle (α) is less than or equal to 41 °. Network arch bridge according to one of the preceding claims, characterized in that the angles (α) are less than or equal to 36 °. Network arch bridge according to one of the Claims 2 , 4th , 5 or 6 , characterized in that the distance (B) between the intersection points (SP _i , SP _{i + 1} ) of adjacent hangers (7 _i , 7 _{i + 1} ) and top flange (3) to the arch base point (FP) becomes smaller. Network arch bridge after Claim 7 , characterized in that the distance (B) between the intersection points (SP _i , SP _{i + 1} ) of adjacent hangers (7 _i , 7 _{i + 1} ) and top flange (3) to the base point of the arch (FP) is reduced, the distance B between the intersection points SP of the last and the penultimate adjacent hanger (7) and the top flange (3) is between 75% and 85% of the distance B in the middle of the arc. Network arch bridge according to one of the preceding claims, characterized in that the hangers (7) are made of a fiber composite material which contains carbon fibers. Network arch bridge according to one of the preceding claims, characterized in that the superstructure is formed with a crest as a gradient. Network arch bridge according to one of the preceding claims, characterized in that the hangers (7) have an elastic modulus less than 150,000 N / mm ² . Network arch bridge according to one of the preceding claims, characterized in that the hangers (7) are manufactured with an aerodynamically favorable cross section.

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