DE19823610A1 - Method for producing three dimensional shell sections - Google Patents

Abstract

A method for producing three dimensional shell sections has a support framework which is adjustable to the required contour. The top of the frame is represented by a grid (2) of interlinked struts which flex with the changes in shape. A flexible cover layer (3) separates the framework from the material which is hardened into the required shape. The framework is adjustable in either direction to produce convex and concave profiles on the same section. The required settings of the framework are derived from a simple computer programme.

Description

The invention relates to a device according to the preamble of claim 1 and a method according to the preamble of claim 2.

field of use

Components of any size, preferably flat, freely shaped, thin to moderately thick components should be on a computer-controlled, adjustable and adjustable, elastically flexible, in two directions gene curvilinear and distortable form, hereinafter referred to as formwork be put. For large components, you can proceed element by element Manufactured elements can be put together to form the component and the constructive connection joints in the joints.

In particular, any application of freely shaped, double-curved components in the Construction, such as concrete, reinforced concrete and prestressed concrete components, form-optimized shells structures with complicated geometries, changes in thickness and recesses or Corresponding lost formwork can be built at all. You should be very host can be produced economically and in high quality. Applications in other areas range where flat, free-form elements are required are conceivable.

The goal is a process for integrated computer-aided design, shape optimization, Calculation, construction, production control and element-by-part production of the flächi components on the formwork table with subsequent assembly, installation or assembly.  

State of the art

The prior art can roughly be used in conventionally switched on, pneumatically supported and modeled formwork as well as combinations thereof can be distinguished. One Sanchez-Arcas give good insight into early shell construction and large shell construction (1961) and Joedicke (1962), on the further development especially in the field of pneu Sobek (1987) receives matically supported formwork.

DE 35 00 153 A1 describes a pneumatic formwork with additional options for setting special "pneumatically formed" shapes. DE 38 41 579 A1 describes Possibilities for the construction of simply curved, reusable formwork gene.

In the area of visualization, shape optimization of surfaces and their statically con structural calculation and construction taking into account the most diverse materia Suitable methods and geometries have been developed and are ready for use (form optimization: Ramm (1993), calculation: "Method of finite elements"). they include no manufacturing possibilities.

In the field of mechanical engineering, computer-controlled milling devices are used position any body used.

The prefabrication of components in all areas of technology is known. In construction it is called precast construction.

Disadvantages of the prior art

Double-curved tensile structures are in the field of construction and large construction parts in general, not optimally in any shapes and sizes to the designer can be customized, constructive, static and economic concerns.

There are only certain shapes such as domes, hyperbolic paraboloids and Conoids can be produced. Deviations necessary for structural and structural reasons conditions (e.g. elevations) of easy-to-form surface geometries are not or can only be realized with considerable effort.

The surface geometry is heavily dependent on the manufacturing process. It is very difficult to produce any surface geometry within an economically justifiable framework.

The reusability and adaptability of modified formwork is very low possible to the extent.

Manufacturing on site, particularly using in-situ concrete wise, can lead to many economic, constructive and qualitative disadvantages.

These disadvantages justify the low spread of shell structures and free molded components in our built environment.

The milling techniques common in mechanical engineering are limited to very small components and not suitable for buildings with dimensions of more than a few meters. In addition the material must be easy to work with and can only rarely because of this property  can be used as a construction material in construction. Rather, it can only be as Formwork for the actual, constructive material (e.g. reinforced concrete) who used the.

The precast construction enables the efficient production of concrete components, conditionally but according to the prior art, the production of identically shaped parts in order to economize to be able to find application.

Object of the invention

The unlimited variety of structurally efficient and advantageous in shape ten, freely formed surfaces with a wide variety of applications in the field of construction essens and technology in general, should be inexpensive, quick and accurate become. The goal is an integrated, computer-aided process for the design, for the form optimization, calculation, design, production control and subsequent, esp special element-by-element production of flat components on the formwork table.

The basic procedure should enable as many different types as possible Cover materials that can harden in molds.

Solution of the task

This object is achieved by a device with the features of claim 1 and egg nem method with the features of claim 2 solved.

Advantages of the invention

The described design and manufacturing concept offers unprecedented advantages, because surface areas of any shape and shape with the formwork table thanks to its adjustability and flexibility. The result is one Formwork for all surface geometries and therefore high economic efficiency. The design processing and production control by the computer reduce planning effort and allow visualization and calculation. Shape and thickness optimized free Shaped structures are possible and can be used in many areas of construction and technology in general can be used very advantageously. You expand today's Opportunities in terms of inexpensive, high quality tensile structures and other speaking forms. The production of free-form, lost formwork is possible and opens up completely new possibilities in the field of shaping buildings. Etli This technology could open up new applications.

There is no need for complex formwork on the construction site or in the precast plant restrictions on certain pneumatically formable surfaces geometries with specially cut membranes are necessary, the number is still different finished parts limited by the number of dies required for this.  

Rather, each element that the formwork table is supposed to produce can be different because the formwork table can be quickly reset by computer from precast to precast can.

The advantages of prefabricated construction are fully exploited. This includes high quality and quality control, weather independence, higher concrete strengths better Post-treatment and the reduction of the effects of creep and shrinkage in the late older structure together with greatly increased efficiency and accuracy. Assembly on the construction site from prefabricated parts is time-saving, inexpensive and preferable to in-situ concrete. Due to the prefabricated construction, the construction pro time equalized.

The device and method are not limited to the building industry. Especially with us The possible radii of curvature can be formed from very light materials to be molded and distortion angle can be significantly reduced depending on the method.

Description of exemplary embodiments

At the beginning there is the process of finding form, be it experimental, mathematical or with the help of form-finding algorithms in the form of programs. The form finding pro zess already takes place in the computer or results can be in the form of point coordinates and functions or other definitions. The component is analyzed calculated and constructed, taking into account the issues of manufacture, transport, assembly and the finished component are taken into account.

After choosing any surface geometry suitable for the building that is, the component can be programmed into elements according to predetermined criteria divided and determined the setting of the formwork table and the storage for each element become. To do this, the coordinates of the element in the component are rotated so that they open come to rest on the formwork table and the maximum possible concreting tendencies and Distortion of the formlining should not be exceeded. The geometry data are on transfer the computer-controlled formwork and produce finished parts. Here is between the application of the material to the deflected control table and the order of the material towards the undeflected formwork table with subsequent deformation differentiate, which results in production-related advantages. Any movement Stakes and shelves can be attached. After hardening, the Ele elements from the formwork table and installed at their destination.

Several principles for the construction of such a formwork device are conceivable. you will be described below.

Gratings

The computer-controlled formwork can be flexible, in two directions curved formlining in the size of the elements to be built with a subcon structure, which is computer-controlled by adjusting means in the desired surface geo  deformed, exist. Physically, the double-curved deformation is very much difficult to solve with the available materials. The solution is so-called called gratings. The principle is simply based on how a salad strainer works Understand steel wire mesh. These systems have bending deformability in both Main surface directions and the individual meshes behave smoothly in theirs Level. Nevertheless, a statically determined system is created with appropriate storage with the possibility of any given surface geometry by shifting exercise of the nodes of the grid. The shear rigidity in the plane prevents the double-curved deformability of panels in the classic sense noteworthy size (e.g. a sheet of paper), without which the flexural rigidity of the plate is unacceptable is exceptionally low (e.g. rubber membrane). Leave on the principle of the grating a number of different solution approaches are built up in detail.

Hyperbolic paraboloid

A commonly used group of forms is the parabolic Hyperboloid. Most free forms can easily be made out of pieces parabo misch hyparboloid shaped surfaces are approximated. Formwork for these users This uses the straight generatrix of the hyperbolic paraboloid. This Vorge is well known from the shell construction of the middle of the 20th century, but not in the procedure described below.

Bulk goods

Another possibility is to model the formwork from a schüttba material. Material is computer controlled according to the desired shape modeled. After the element has been built, a new shape can be heaped up.

The dimensions of the elements to be built are particularly as follows Limits: the width of 2.00 to 4.00 m and the length preferably 3.00 to 10.00 m.

The radii of curvature and distortion angle can depend on a wide range of the formwork used and the workability of the for material vary.

Embodiments of the invention are shown in the drawings and are in following described in more detail.

Grating

As an example for the use of the grating principle, a formwork table, consisting of a grating made of flexible beams and a scarf made of egg steel wire mesh with a thin membrane.

A reasonable compromise must be found between the spacing of the adjustment structures 1 , the deflection of the beams 2 under the weight of the material 5 to be molded (e.g. fresh concrete) and the flexibility of the beams. The minimum permissible radius of curvature with elastic deformation of the carrier 2 can be calculated from the yield stress, the modulus of elasticity and the cross-sectional height. The radius of curvature becomes smaller as the cross-sectional height decreases. In contrast, the stiffness of the girders increases with increasing cross-sectional height and undesirable deformations due to the fresh concrete dead weight decrease. Since the yield point has a decisive influence on the flexibility of the bars with constant rigidity (EI), the flexibility of the designed formwork table can be increased by steels with a higher yield point. The grating consists of round steel sections 2 , 9 , 10 to ensure the same rigidity in all directions.

The connection 8 of the bars at the hinge should avoid jumps in rigidity and ensure a connection in one plane if possible. At the node 8 of the grate, the computer-controlled vertical adjustment devices 1 , 11 are BEFE Stigt. Each adjustment device (e.g. spindle) is controlled by the control software and precisely implements the deflections resulting from the desired geometry.

A fine steel grid 13 is attached to the supports. It serves as part of the scarf skin and is intended to ensure sufficient distortion and flexural strength to achieve the desired surface shape between the grating beams. Because of the small mesh size, a thin and stretchable membrane 14 can form the final formwork skin on the fine steel mesh. Due to the fresh concrete weight, it is pressed so strongly on the grid that it cannot slide between the fresh concrete and the grid, other possibilities for fixing (e.g. gluing) are conceivable.

On the formwork skin 3 (in the flat neutral position 6 ), the positions 4 that can be arranged and deformed are fastened and the material (eg fresh concrete) 5 is introduced into the plane. Thereafter, the adjustment structures 1 are adjusted from the neutral position 6 to the desired position and thus deform the table structure, shutdowns and the material which can still be formed. The material then hardens. The process can be repeated any number of times.

Various constructions are conceivable for the parking positions 4 , for example soft, heavy rubber profiles, which can follow the deformations of the membrane and are held in place by their own weight.

With this configuration, a reasonable compromise can be achieved between the surface quality and the necessary flexibility of the formwork table. With minor post-treatment, the surface quality can be further increased if necessary. If the formwork lies in the neutral position 6 on the floor 7 , the formwork can be walked on and a simple, efficient concreting process can be carried out using methods comparable to those of black-roof construction.

In the articulated connection of the grating supports, the weakening of the bars by the screw connection 15 must be taken into account. At this point, undesirable plastic phenomena can arise when overstressed. In the worst case, this weak point reduces the permissible radius of curvature. It should be constructed very carefully from these greens. A connection possibility is shown as an example in FIG. 2.

The distances between the nodes 8 always remain constant, regardless of the geometry set. The nodes form an "equidistant network" on the surface. This must be taken into account when calculating the deflections of the nodes. This results in inclined positions of the adjustment structures. For the formlining, this means that only distortions occur, no longitudinal strains.

The grid 13 is literally sewn up with thin steel wire on the grating supports, which ensures the free rotation without weakening the cross-sections involved. In addition, the formlining can be attached to the substructure very continuously.

It is more difficult to implement the storage conditions in order to provide kinematics for the spindle Avoid formwork construction. It is proposed to move bearing axes along the Fasten rectangle bisectors. This is to ensure that adjusting device lines along these axes are not perpendicular to these axes. At the Crossing point of the bearing axes results in a horizontal fixation in all directions the spindle located there. With this storage a kinematics of Ge entire system, consisting of the adjustment structures designed as pendulum supports and the grating, avoided.

As an example, it is proposed to install steel strips that are held at their ends and are attached to the relevant spindles. It lies in all directions horizontally held point in the middle of the table surface, is the summation of the flat distortion towards the corners is minimized.

Support frame with membrane

On a frame of four rigid, articulated mitein other connected beams 16 , a membrane 17 is stretched. If adjustment structures 18 are arranged under the corner points of the frame, controlled and the supports are twisted against one another, the membrane 17 forms an arbitrarily adjustable hy perbolic paraboloid. If the beams 16 are stiff enough, adjustment devices 18 at the corners of the beams are sufficient. The frame 16 can be distorted to increase the variety of shapes, but then the membrane must be elastic enough to remain taut or it must be re-tensioned.

On the membrane 17 (in the flat neutral position), the positions 18 which can be arranged and deformed are fastened and the material (e.g. fresh concrete) 21 is introduced into the plane. The adjustment constructions are then moved from the neutral position 22 into the desired position and thus deform the membrane, supports and the material which can still be formed. The material then hardens. The process can be repeated any number of times.

Various constructions are conceivable for the stops 20 , for example white, heavy rubber profiles which can follow the deformations of the membrane and are held in place by their own weight.

The deflection of the membrane due to the material's own weight may not be neglected. Because it is in any case a translatory surface with straight generators (control surface), 16 struts 19 can be drawn in parallel to the frame supports. The membrane can be protected by the grid of struts 19 connected to the frame in an articulated manner. It can also be relieved by a slight internal pressure (air pressure, liquids) in the amount of the material's own weight, smaller material thicknesses or higher preload. Because only slight distortions occur, stiff membranes made of thicker rubber with high preload can be used.

With high preload, the edge girders are highly stressed in their plane on bending. The struts 19 can significantly reduce the bending stress on the edge beams 16 by short-circuiting the forces.

Sand hill

Sand or similar bulk material with an internal angle of friction is heaped up in a loading area 23 of the size of the elements to be concreted and then removed by means of a computer-controlled bendable screed 25 . A screed with 26 height-adjustable bending beams with computer-controlled stamps is used. The Bal ken is movably mounted in guide rails 28 and pulls the sand in the direction 30 of the guide rails with dimensional accuracy. In addition, the bulk material can also be compacted. While the screed is being driven, its shape changes depending on the position on the crossing route and any surface shapes can be modeled. It makes sense to cover the resulting formed sand hill with a film or similar, provide a shelf and then the element can be concreted. The screed, previously used to remove the sand, removes the concrete in a further transition and thus adjusts the thickness precisely at every point. The simple reuse of the bulk material is advantageous, which is not influenced by the concreting and does not wear out.

With moistened sands, the shape could take advantage of the resulting cohesion are further stabilized in the sand or greater inclinations are reached. Too beach ten is that relatively small radii of curvature can be formed.

An advantage that should not be underestimated is that the technical equipment is kept to a minimum can be reduced, because actually only a puller or a vibrating plank for one position of the geometry is necessary. This device can be designed to be portable, to be able to manufacture the finished parts on site at the construction site. At the construction sites Manufacturing is independent of the limitations of the component size because it is transported  over public roads and long transport routes.

drawings

In the following, sketchy drawings are used to better understand the device device and the procedure briefly described and enclosed.

Fig. 1: Schematic representation of a formwork table according to the grating principle. It should be noted that the distances between the nodes 8 of the grating girders are not constant for drawing reasons and therefore the spindles 1 are shown vertically. This is not the reality. Nevertheless, the sketch gives a good impression of the structure and functioning of such formwork tables. The neutral position 6 of the formwork table is shown in dashed lines.

Fig. 2: This sketch shows an exemplary grating node as a detail. The schematic construction of the formwork skin comprising a steel wire mesh 13 and a rubber membrane 14 fastened thereon can be seen.

Fig. 3: A formwork table based on the principle of the hyperbolic paraboloid.

Fig. 4: Bulk hill 23 formed with a computer-controlled deformable in dependence on the feed pile 25th The shaped surface 24 is shown with dashed lines.

literature

Joedicke, J. (1962): Shell construction documents of modern architecture, Karl Krämer Verlag Stuttgart, Stuttgart 1962.
Ramm, E., et al. (1993): Shape Optimization of Shell Structures. IASS Bulletin of the international Association for Shell and Spatial Structures Vol. 34 (1993).
Sanchez-Arcas, M. (1961): Shape and construction of the shells. German Building Academy, VEB Verlag für Bauwesen, Berlin 1961.
Sobek, W. (1987): Concrete formwork made on pneumatically supported formwork. From the work of the Institute for Concrete Structures, Verlag Ursula Sobek, Stuttgart 1987.

Claims (25)

1. Formwork table for the production of components made of materials that harden in molds, with a formwork skin and a substructure for supporting the formwork skin, characterized by at least one adjusting device that is assigned to the formwork skin and a reversible deformation of the curvature, particularly in two directions , Formwork skin enables. 2. Process for the production of components from materials that harden in molds with the steps: placing the material on a formlining and shaping the formlining via at least one adjustment device in order to specify any desired To get shape. 3. Formwork table according to claim 1 for large-format elements and components made of material fen that harden in molds, characterized in that at least partial areas the formlining and substructure are at least simply curved, but in particular the other double-curved, with computer-controlled adjustable adjustment devices ela are stisch and or reversibly deformable and that basic structure, substructure Formwork skin and adjustment means together with the desired free-form set Form a stable formwork surface without major physical changes components are very often adapted to new surface geometries and can be reused. 4. Formwork according to claim 1 and 2, characterized in that the finding and Monitoring the setting of the formwork table and the manufacturing process in total together with an integrated computer-controlled design, form finding, Calculation, construction, control, control and manufacturing process takes place. 5. Formwork according to claim 1 and 2, characterized in that the manufacturing pro This is done element by element and the assembly of the elements separately, in particular which takes place on the construction site, to the component. 6. Formwork according to claim 1 and 2, characterized in that a control pro from the given surface geometry, a division into elements takes, this processed by geometric transformations so that the setting of the formwork table, taking into account the process-related inclination gen, warping and distortion, especially by rotation, translation and variation of the surface geometry in the element area.   7. Formwork according to claim 1, 2 and 6, characterized in that a control program from the given surface geometry for the adjustment of the Circuit relevant data (by the process, system or other conditions criteria and a special kind of networking of the surface, ins special equidistant networks, taking into account the existing in the formwork table kinematics for adjusting and storing the adjustment devices. 8. Formwork according to claim 1, characterized in that special constructive Measures are taken to ensure the free deformability of the formwork table ensure, but to avoid kinematics of the device. 9. Formwork according to claim 1, characterized in that the material to be molded applied in the neutral position of the formwork table and then together with the Formically deformed. 10. Formwork according to claim 1, characterized in that the formwork in the new central location for maintenance purposes and to support the concreting process on a document. 11. Formwork according to claim 1, characterized in that flexible on the formwork skin Parking positions are computer controlled positioned and attached to the conclusion of the elements according to freely selectable geometries and the accuracy of fit ensure under the elements. 12. Formwork according to claim 1 and 11, characterized in that the stops be formed in such a way that the non-positive connection of the elements te to each other to the component, in particular by reinforcements of all kinds light becomes. 13. Formwork according to claim 1 and 2, characterized in that any reinforcements type before and during the entire manufacturing process can. 14. Formwork according to claim 1 and 2, characterized in that by a suitable nete concreting method computer controlled changes in thickness in the element and thus in Areas of the component are possible.   15. Formwork according to claim 1 and 2, characterized in that to deform the materials are applied in layers on the formwork to pass through the part cure the individual layers before applying the following layer To stiffen the formwork. 16. Formwork according to claim 1 and 15, characterized in that different Materials to be deformed are applied to the formwork in layers assign special physical properties to the individual layers (Sandwich construction). 17. Formwork according to claim 1 and 2, characterized in that the formwork con is structurally designed so that post-treatment to improve the physica mical element properties of the hardening material is made possible. these are For example, tempering and / or keeping the moisture in concrete. 18. Formwork according to claim 1 and 2, characterized in that the substructure tion and the formlining consists of systems of bending beams, which in particular in the crossing points are specially held and stored to the stretch free double-curved deformation of the formwork table, especially the bending and distortion, to ensure (gratings that can be distorted in their plane after the Salad screen principle, grids). 19. Formwork according to claim 1 and 2, characterized in that the formwork skin bendable and distortable, fine grids are made by special dimensions were sealed and the favorable properties of the grid keep, especially by covering with an elastic membrane or Installation of a distortable, sealing substance in the grid to create a smooth, to create accurate and dense surface. 20. Formwork according to claim 1 and 2, characterized in that a system of several interconnected layers of grids as a substructure (Main beam layer), secondary beam layer and formlining are used to make a even distribution of loads from the material to be deformed and low To achieve deformation of the formwork. 21. Formwork according to claim 1 and 2, characterized in that the desired Surface geometry by peeling off a loose material, in particular Sand, by means of a computer-controlled, shape-generating device.   The resulting shape can possibly be covered, fastened and then concreted the. 22. Formwork according to claim 1 and 2, characterized in that a membrane an adjustable frame is tensioned and the membrane through the Adjustment of the frame is deformed to in particular surface geometries with the properties of the hyperbolic paraboloid. 23. Formwork according to claim 1 and 2, characterized in that to increase the Shape accuracy internal pressures, especially air pressure drop, can be used. 24. Formwork according to claim 1 and 2, characterized in that a mobile con receipt of the formwork table is used to manufacture elements on site.