WO2001086089A1

WO2001086089A1 - Prestress-stabilized constructional elements

Info

Publication number: WO2001086089A1
Application number: PCT/CH2000/000254
Authority: WO
Inventors: Josef Peter Kurath-Grollmann
Original assignee: Swissfiber Ag
Priority date: 2000-05-08
Filing date: 2000-05-08
Publication date: 2001-11-15
Also published as: AU2000240966A1; EP1280968A1

Abstract

The invention relates to a constructional element (1) for use as a beam, support or brace, especially for use in structural engineering and bridge building, which is designed for a bending load (F) in at least one transverse direction. The constructional element (1) is composed of at least two longitudinal elements (2) and an interposed bulkhead (3) that are braced with one another via bracing elements (7) disposed in the longitudinal direction at least in the tension area of the construction element (1). The bulkhead (3) is thus pressed against the respective end sections of the longitudinal elements (2) merely by the prestress and stabilizes the shape of the longitudinal elements (2) and receives the shearing forces caused by the bending load. The longitudinal elements (2) are provided with at least one tension (4) and pressure chord (5) and thin-walled web elements (6, 6") linking them. The inventive constructional element (1) is light-weight and has an excellent flexural strength and torsion-proofness.

Description

CONSTRUCTION ELEMENTS WITH PRESERVED STABILIZATION

The present invention relates to a construction element according to the preamble of claim 1.

Such construction elements are used in particular in building and bridge construction as supports, supports or struts and are designed for bending loads at least in a transverse direction and have at least one longitudinal element which consists at least predominantly of a first material. When building bridges, scaffolding, tents, roofs and other load-bearing structures, components are required which are capable of absorbing bending loads in at least one transverse direction to the main longitudinal direction. For safety reasons, this load capacity should be so great that the load actually present in the building only makes up a fraction of the maximum load capacity. It is also important for most applications that the elastic modulus of such elements is as large as possible, i.e. that the elements are only slightly bent under load.

Traditionally, iron or steel beams as well as concrete in combination with reinforcements are used for this purpose. The latter, for example, is such that reinforcing bars are arranged in the tensile zones of the elements caused by bending loads, which reinforcement bars can absorb the resulting tensile load (so-called sleep reinforcement). This is necessary because, despite the relatively large modulus of elasticity, concrete can withstand large compressive loads, but can withstand tensile loads as a result of it

BESTATIGUNGSKOPIE Brittleness is comparatively very vulnerable. Such sleep reinforcement has the disadvantage that, on the one hand, the effectiveness of the reinforcement only occurs when a tensile load has already built up in the component and the concrete has stretched and thus the component has already bent a little, and on the other hand the connection between concrete that occurs during concreting and reinforcement material is usually not optimal and therefore the train cannot be taken over 100% efficiently. So, in particular in bridge construction, so-called prestressed concrete is used in order to enable more elegant constructions, in which pipes are not concreted in, instead of reinforcing bars, into which tensioning cables are pulled. In this way, the concrete can not only be subjected to greater loads with the same cross-section, but it is also possible, when applying a pretension to the cables, that their effectiveness does not start only when the concrete bends significantly, but immediately absorbs any tensile load. However, the insertion of cables does not significantly increase the elastic modulus of concrete, since the cables only make up a very small proportion of the cross-section compared to the concrete, but it is prevented by a suitable pre-tensioning and usually associated "prevention" against the bending load that the concrete already bends due to its own weight in such a way that the limits of the load capacity are reached in the tensile zones.

All of the above materials now have a very high specific weight, which has disadvantages in construction and, as mentioned above, also causes serious problems due to the weight of the components. Especially with concrete in bridge construction, the additional load due to the load when using the bridge is usually almost negligible compared to its own weight. This is also the reason why the prestressing technology is mostly used in bridge construction and often also used to enable elegant constructions, additional visible carrier tension cables from bridge girders are used, which can take on parts of the weight load.

A fundamentally different approach is to use lighter materials. Plastic components made of new, high-quality plastics with their low weight and good environmental resistance have been used more and more recently. Steel girders are replaced by replicating the classic profile structures made of plastic, for example made of glass fiber reinforced plastic (GRP). Unfortunately, most plastics have unfavorable elasticity modules, so that very thick plastic profiles have to be built in order to achieve properties similar to steel beams. A slight reduction in the thickness of such supports can be achieved by embedding very high quality fibers. The effectiveness of such solutions is low, however, and there is still an unmet need for lightweight, bending load-resistant and weather-resistant construction elements.

The present invention is therefore based on the object of making available a construction element which, with a low weight, is capable of absorbing a large bending load. This object is achieved according to the invention by a construction element with the features of claim 1.

A simple, rigid and light construction element is advantageously provided, which is achieved by the combination of longitudinal elements and bulkheads in between. The bulkheads are not firmly connected to the longitudinal elements, but are pressed against the corresponding end edges of the longitudinal elements by the continuous tensioning elements. It has surprisingly been found that this connection has a very positive influence on the buckling behavior of the hollow body forming the web in such a way that such a structural element can withstand even large bending loads without bulging this hollow body. At the same time, these bulkheads can serve as shear force introduction elements, which predestines their use in bridge construction.

Another great advantage is the reusability of the construction elements, in that after releasing the preload, i.e. the loosening of the tensioning elements, the construction element again simply into its individual parts, i.e. Longitudinal elements, bulkheads and tensioning elements can be dismantled. For example, the creation and dismantling of a mobile transition such as a bridge can advantageously be carried out very easily.

Preferred embodiments of the invention result from the features of further claims 2 to 12. For example, the tensioning elements are advantageously arranged in both the tension and compression straps, which results in a homogeneous pre-tensioning over the entire cross-section of the construction element and a homogeneous pressing of the bulkheads against the longitudinal elements.

The tensioning elements are preferably arranged within the hollow body, which is designed to be continuous in the longitudinal direction, with which they are protected against external influences.

The bulkheads advantageously have outer dimensions and shapes corresponding to the cross section of the longitudinal elements. If they are to be used as force introduction points or support points, however, the dimensions can preferably also be larger, at least in some areas. In this way, for example, connecting webs between two construction elements arranged in parallel can be connected in a simple manner to form a bridge with the bulkheads.

Plastic, in particular fiber-reinforced plastic, is particularly suitable as the material for the construction elements according to the invention. The tension and compression belts can advantageously be formed from closed hollow plastic profiles, for example with a square cross section. In the train area, for example, several such profiles can be connected above or next to one another due to the higher load. The web connecting the tension and compression straps can likewise advantageously be formed from a thin-walled plastic, for example by laterally attaching two curved half-shells to the side side walls of the tension and compression belts. These shells can consist of glass fiber reinforced plastic, possibly in a sandwich construction, in order to meet the requirements in particular with regard to the outer wall.

The individual longitudinal elements can be assembled to the construction element, for example by applying lamellae, preferably CFRP lamellae, to the side walls of the tension or Pressure belts can be pre-tensioned individually.

This is an excellent combination of materials, which is very light, easy to work with and has great stability against weather and corrosion.

It has also been shown that the construction elements according to the invention have, in addition to the desired bending stiffness, a very high torsional stiffness. This even enables the use of a single construction element of this type as a bending beam, for example for bridges or bridges, without the risk of the floor covering attached to it being twisted.

Such construction elements according to the invention are particularly suitable for the simple, inexpensive and rapid creation of transitions such as bridges or bridges. Buildings of this type can not only be built up quickly with the construction elements according to the invention, but can also be dismantled again quickly and, if necessary. reinsert at the same or a different location. Another advantage is that the total costs, for example for small bridges such as pedestrian bridges, are significantly lower compared to conventional steel or wood structures.

Embodiments of the invention are explained in more detail below with reference to drawings. Show it:

1 shows a schematic side view of a construction element according to the invention in the basic form;

2 shows the cross section through the construction element according to FIG. 1;

3 shows a schematic side view of a construction element consisting of a plurality of longitudinal elements and bulkheads;

4 shows the cross section through a longitudinal element of a construction element according to the invention;

5 shows the cross section through the pressure belt area of a longitudinal element with an additional cover;

6 schematically shows the composition of a construction element according to the invention;

7 schematically shows the partial view of a bridge using two construction elements according to the invention arranged in parallel; Fig. 8 shows schematically the cross section through an alternative bridge shape using a single construction element according to the invention.

Figures 1 and 2 show schematic representations of a simple embodiment of the present invention. Figure 1 shows a side view of a construction element 1, which comprises two longitudinal elements 2 and an intermediate bulkhead 3. The longitudinal element 10 consists, for example, of a tensile and compression straps 4 each formed as an elongated, box-shaped hollow body and two half-shells 6, 6 'forming the connecting web. Preferably, the hollow body of the train or Pressure belts 4.5 made of glass fiber reinforced plastic (GRP) extruded or extruded. The construction element 1 is designed to absorb a bending load F, which is marked with an arrow.

If a bending load F is applied, the structural element 1 deforms, and on the side facing the bending load F a pressure zone is formed where the material is compressed, and on the side facing away from the bending load F a tension zone is formed in which the material pulls apart becomes. A so-called neutral zone is located between the compression and tensile zones, in which essentially no or only small compressive or tensile stresses occur during the deflection process. So that the above tensions not only from the material of the corresponding tensile or Pressure belts have to be picked up, tension elements 7 are now drawn in in the tension zone and in the pressure zone, preferably parallel to the tension zone Longitudinal direction of the structural element 1 in the cavity of the corresponding train or. Pressure belt 4.5. Alternatively, the tensioning elements 7 could of course also be arranged outside the cavity.

The clamping elements 7 consist of a material which has a much greater modulus of elasticity in the longitudinal direction than the material of the tensile 5 or. Pressure belts 4. Steel cables or carbon fiber reinforced plastic (CFRP) have proven suitable. While GRP parts have elasticity modules in the range of 5-45 GPa in the longitudinal direction, elasticity modules of 100-300 GPa can be achieved with CFRP cables. The elastic module of the structural element 1 as a whole is significantly increased as a result of the suitable choice and arrangement of the clamping elements 7 as well as the punctiform or linear fixing of the clamping elements 7 on the longitudinal element 2.

The tensioning elements 7 can only be fixed in the end region near the bulkhead 3 in the longitudinal elements 2 or in each case can be fixed on the free ends of the longitudinal elements 2, for example on plates attached there. In the former case, the prestress is only applied in the area of the bulkheads 3 of the construction element 1, in the latter case the prestress is applied along the entire length of the construction element 1.

The use of the material combination GFK and CFK enables construction elements 1 of great fatigue safety, of very good chemical resistance, of light weight and with large tension reserves. The GRP parts can have wall thicknesses of 1-100 mm and preferably 2-20 mm, and it has been shown that a cross-sectional ratio of GRP to CKF of 5: 1 to 20: 1, in particular 10: 1, is advantageous.

The tensioning elements 7 are prestressed by, for example, at the ends of the tension 5 or. Pressure belts 4 are held in brackets 8 and tightened. The tensioning elements 7 in the compression and in the tension zones are advantageously up to 30% of the compressive strength of the material of the tension 4 or. Pressure belts 5 pretensioned. This has the advantage that the effectiveness of the tensioning elements 7 does not begin until the longitudinal elements 2 have already been deformed, but already from the beginning of the load F.

In order to intensify this effect, one can even proceed, for example, in such a way that the tensioning elements 7 in the hollow body of the pull 4 or. Pressure belt 5 are guided in a tube or through guide eyelets so that when

Tightening and stretching the clamping elements 7 slightly bent the longitudinal element 1 of the expected bending load F, i.e. is preformed. The bending load F is thus optimally anticipated and essentially entirely taken over by the tensioning elements 7 arranged in the tension zones, while in the pressure zones the pressure in the longitudinal element 2 increases and the tensioning cables 7 arranged there are slightly relieved.

It is now also possible to insert the clamping elements 7 into the longitudinal elements 2 in the form of strips, strips or lamellae 9 to move in, to glue in, to fix, or to install directly into the wall during the manufacturing process.

The pretensioning by means of such lamellae 9 can be generated in a variety of ways, a simple way of pretensioning when gluing or gluing the clamping lamellae 9 is, for example, the following manufacturing process: the longitudinal element 2 is bent against the expected bending load F with a counterforce. This creates a pressure zone where a tensile zone is created when the actual bending load F is applied. In this momentary pressure zone, the lamella 9 is now glued on and the counterforce on the longitudinal element 2 is relieved as soon as the adhesive is dry. This procedure can be carried out in all possible load directions.

The longitudinal element 2 can also be compressed in the longitudinal direction before the slats 9 are fixed. If the longitudinal element 2 is relieved again after the lamellae 9 have been fixed, the compression decreases elastically and the lamellae 9 are placed under a prestress.

In Figure 3, a construction element 1 is shown, which consists of three longitudinal elements 2 and two bulkheads 3. The longitudinal elements 2 are simply attached to one another in a modular manner, and the tensioning elements 7 are drawn in here, for example, through the entire length of the structural element 1 and fastened to brackets 8 on the outside. The ends of the longitudinal elements 2 abut the bulkheads 3, which are thereby simply pressed on by the pretension and enter into a frictional connection. It is with it no further connection of the individual longitudinal elements 2 and the bulkheads 3 to one another is necessary. A bending load F can thus be optimally distributed over the entire length of the construction element 1. The pretension proves to be a special additional advantage here, since the individual elements, ie the longitudinal elements 2 and the bulkheads 3, do not have to be screwed or glued together. The former usually leads to a considerable weakening of the material as a result of the recesses required for the screw connection and is complex, and the latter can only be carried out efficiently to a limited extent on the construction site because the liability must be extremely good.

FIG. 4 shows the cross section through a longitudinal element 2 of a construction element 1 according to the invention. Two tension belts 5 and a single pressure belt 4 are now preferably formed here. This train- 5 sp. Pressure belts 4 are formed by essentially a square cross section on iron hollow body profiles. A single tensioning element 7 in the form of a round cable is arranged within these profiles, for example in the pressure area; also in the respective profile of the tension belts 5. With this arrangement, the tensile load resulting from the bending load F in use can be taken into account, while in the pressure area only the pretension has to be applied, while under the bending load F there is a relief.

The curved shape of the two half-shells 6, respectively. 6 'is by the respectively between the ends of the longitudinal elements 2 arranged bulkheads 3 fixed by the tensioning elements 7 after the prestressing.

The train 5 resp. Pressure belts 4 can of course also be designed in other cross-sectional shapes and in particular also vary in number according to the needs. For example, instead of the tensioning elements 7, any installations such as cables or tubes can be guided in such cavities.

FIG. 5 also shows a section of a cross section through a longitudinal element 2 of an alternative construction element 1 according to the invention in the region of the pressure belt 4. The pressure belt 4 here consists of two superimposed profiles with a rectangular cross-section. The shells 6, respectively. 6 'are formed here connected to their side walls over the entire height of these two profiles. On the outside of these shells 6, respectively. 6 'in the region of the pressure belt 4 there are now slats 9 made of carbon fiber reinforced plastic which absorb the pretension applied to the pressure belt 4 in the manufacturing process, as already described above.

A U-shaped cover rail 10 is now arranged over this upper section of the construction element 1, which covers the entire area with the slats 9 and the upper edge of the upper profile of the pressure belt 4. On the one hand, this serves to protect this area both from weather influences and from damage to these areas by external influences, for example by people or by vehicles. At the same time, Cover rail 10, for example, posts 11 of railings or the like can be attached.

Finally, FIG. 6 schematically shows the successive, resolved arrangement of the individual elements of the basic shape of a construction element 1 according to the invention for a better overview. This consists of a first longitudinal element 2, a subsequent bulkhead 3 and a further longitudinal element 2. These elements 2 and 3 are connected to one another in a tensioned manner only by attaching the tensioning elements 7 arranged in the tension and compression area of the construction element 1. Advantageously, no further connecting elements are required, which also enables simple and easy disassembly of a construction element 1 formed thereby. It is obvious that by arranging any number of such longitudinal elements 2 and bulkheads 3 on the one hand, construction elements 1 can be created in practically any length, but on the other hand the shape and rigidity due to the tensioning by the tensioning elements 7 and possibly also within certain limits , the application of different prestressing by the slats 9 acting as additional prestressing elements can be adjusted according to requirements.

An example of use of the construction elements 1 described above is shown in FIG. It is a simple bridge 12, such as is used for bridging a river or a road. The bridge 12 consists of two construction elements arranged laterally parallel to one another. elements 1 and 1 ', as well as from a bridge surface 13 that can be entered or driven on between them. This bridge surface 13 is formed here, for example, by two parallel plate elements arranged one above the other, each of which is connected to the bulkheads 3, 3' of the two construction elements 1, 1 ¹ are.

FIG. 8 shows the cross section through an alternative embodiment of a bridge 12. In this example, the very high torsional rigidity of the construction elements 1 according to the invention is used, and only one such construction element 1 is arranged in the longitudinal axis of the bridge 12. The bulkheads 3 are preferably designed here directly as widely projecting frames, on the upper edge of which the bridge surface 13 can be attached directly. Especially for smaller bridges 12 with limited loads, this embodiment enables a particularly cost-effective implementation of a transition.

Further uses of the construction elements described arise wherever beams, supports, struts or flat constructions with a load-bearing function are required, which should have a high bending strength with little weight and must have a high chemical resistance. Applications in scaffolding, tent construction, but also in the construction of roofs, retaining walls, furniture, and in aircraft and shipbuilding are also conceivable.

Claims

PATENT CLAIMS

1. As a support, support or strut, in particular in building and bridge construction, usable construction element (1) which is designed for a bending load (F) at least in a transverse direction and has at least one longitudinal element (2) which consists at least predominantly of a first material , and is pretensioned with at least one tensioning element (7) with regard to its length, the tensioning element (7) consisting at least predominantly of a second material, and wherein at least one tensioning element (7) with respect to the bending load (F) in the in the Structural element (1) occurring tensile zone, characterized in that at least two longitudinal elements (2) and a bulkhead (3) arranged between the respective facing end edges of the longitudinal elements (2) and lying against these end edges, the longitudinal elements (2 ) each have at least one tension (5) and a compression belt (4) designed as a hollow body and a tension and compression belt v connecting web (6, 6 '^' ), the web also being designed as a thin-walled hollow body (6, 6 '), and that each tensioning element (7) in each case at least in the mutually facing end regions of the one separated by a bulkhead (3) Longitudinal elements (2) is fixed and thereby press the corresponding end edges on the respective bulkhead (3).

2. Construction element (1) according to one of claim 1, characterized in that at least one further clamping element (7) with respect to the bending load (F) in the is arranged in the pressure zone occurring in the construction element (1).

3. Construction element (1) according to claim 1 or 2, characterized in that the clamping elements (7) within the train (5) or. Pressure belts (4) are arranged.

4. Construction element (1) according to one of claims 1 to 3, characterized in that the bulkheads (3) each lie over the entire surface of the corresponding edges of the longitudinal elements (2), and that these edges of the longitudinal elements lie in one plane.

5. Construction element (1) according to any one of claims 1 to 4, characterized in that the bulkheads (3) extend at least to the outer cross section of the longitudinal elements (2) and preferably protrude at least in places.

6. Construction element (1) according to one of claims 1 to 5, characterized in that the bulkheads (3) consist of plastic, preferably fiber-reinforced plastic.

7. Construction element (1) according to one of claims 1 to 6, characterized in that the tensioning elements (7) are connected at least in regions in the longitudinal direction to the longitudinal elements (2), preferably glued.

8. Construction element (1) according to claim 7, characterized in that the clamping elements (7) made of fiber reinforced tem, preferably carbon fiber reinforced plastic, preferably in the form of a lamella (9).

9. Construction element (1) according to claim 8, characterized in that the tension (5) and / or compression straps (4) of the longitudinal elements (2) on the outside with at least one lamella (9) acting as a tensioning element (7). are connected, preferably glued.

10. Construction element (1) according to one of claims 1 to 9, characterized in that the first material of the longitudinal elements (2) is a plastic, preferably a fiber-reinforced plastic, preferably a glass fiber-reinforced plastic with a modulus of elasticity in the longitudinal direction in a range of 5,000 up to 45,000 MPa.

11. Construction element (1) according to one of claims 1 to 10, characterized in that a carbon fiber reinforced plastic or a steel is used as the second material for the tensioning element (7), preferably with a modulus of elasticity in the longitudinal direction in a range of 100 ' OOO to 300O00 MPa.

12. Construction element (1) according to one of claims 1 to 11, characterized in that the bias of

Clamping elements (7) and / or the slats (9) is 5 to 40%, particularly preferably 10 to 25%, in relation to the compressive strength of the first material of the longitudinal elements (2).