US3696573A

US3696573A - Pressure container prestressed concrete or the like

Info

Publication number: US3696573A
Application number: US879798A
Authority: US
Inventors: Wolfgang Zerna; Ludwig Muhe
Original assignee: Philipp Holzmann AG
Current assignee: Philipp Holzmann AG
Priority date: 1968-11-25
Filing date: 1969-11-25
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10
Also published as: FR2024927A1; AT317368B; SE348256B; JPS4946328B1; GB1292292A; NL167791C; BE742116A; DE1810825A1; CH521002A; NL167791B; NL6917706A

Abstract

A pressure container is wound with special bands of wires in superposed groups and the wires are prestressed and clamped to the container by means of superposed axial strips on the container with radial bolts engaging the walls of the container.

Description

1451 Oct. 10,1972

United States Patent Zerna et a1.

2,375,921 5/1945 Hll'Sh ....138/176 3,052,266 9/1962 Huck.........................138/176 1,326,594 12/1919 Hume........................138/172 [54] PRESSURE CONTAINER PRESTRESSED CONCRETE OR THE LIKE [72] Inventors: Wolfgang 7km, Hammer 3 217 451 11/1965 Closner 52/224 Kirchmde; Lmiwig Muhe Obem" 3 404 497 10/1968 Burrow.......::::::..::.::::: sel, Taunus both of Germany Philipp 52/224 3,523,063 8/1970 Zerna..........................52/224' FOREIGN PATENTS OR APPLICATIONS Holzmann Aktien- [73] Assignee:

gesellschaft, Taunus-Anlage, Germany 1,290,306 3/1962 France.........................52/224 152,562 7/1953 Australia...................138/172 120,088 10/1918 Great Britain.................220/3 493,946 6/1953 Canada........................52/224 461,596 3/1949 Italy ...138/172 [22] Filed: Nov. 25, 1969 [21] 'Appl. No.: 879,798

[30] Foreign Application Priority Data Primary Examiner-Frank L. Abbott Nov. 25, 1968 Germany..........P l8 10 825.3 Assistant Examiner-James L. Ridgill, Jr.

Attorney-Waters, Roditi, Schwartz & Nissen [52] US. Cl. 52/248, 138/176 [51] Int. Cl. 3/20, F161 9/04 ABSTRACT [58] Field of Search................52/224, 741, 248, 223;

138/172 175477; 220/3; 264/228 229 A pressure container is wound with special hands of wlres 1n superposed groups and the wires are prestressed and clamped to the container by means of [56] References Cited UNITED STATES PATENTS superposed axial strips on the container with radial bolts engaging the walls of the container.

2,236,108 3/1941 Miller et a1. ...............138/l76 3 Claims, 10 Drawing Figures PATENTEDUBT 10 m2 SHEET 3 [IF 6 Fig.3

PATENTEDnm 10 1912 3.6 96, 57 3 sum 11 0F 6 Fig.5

Fig.6

PRESSURE CONTAINER PRESTRESSED CONCRETE OR THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a pressure container made from prestressed concrete or other prestressed material, for example prefabricated concrete elements having, on the outer surface of the container walls, prestressing members or prestressing bands which extend in the peripheral direction with helical turns and serve for producing an annular tensile pressure in the container wall. The prestressing members are .arranged in a plurality of radially superposed layers and, within the layers, optionally several at a time are juxtaposed and are jammed fast between end anchoring means at a plurality of points on the container wall. The invention relates further to a process for the prestressing of such pressure containers.

2. Description of the Prior Art The development in the field of pressure containers has, in particular in connection with the manufacture of reactors, resulted in the production of containers which have extremely large dimensions and are subjected to extremely high loads for the resistance of which is is necessary to produce in the container walls correspondingly high prestressing forces of the order of magnitude of up to several thousand tons per meter of container height. The material forming the container walls (this material is generally concrete) is able, without difficulty, to satisfy the requirements arising in this connection, in particular with regard to compression or crushing strength. However, it has been found that the problem of prestressing the containers in the peripheral direction with prestressing forces of the order of magnitude indicated involves considerable difficulty.

This applies also to known pressure containers made from prestressed concrete of the type mentioned at the outset, since it is no longer sufficient, in order to produce the high prestressing forces, to wind in only one position about the container walls a single prestressing wire which may be readily secured to the container walls. On the contrary, it is necessary for this purpose to use prestressing members having the form of prestressing wire bundles comprising prestressing wires juxtaposed in many layers and, with these, it is found to be extremely difficult to arrange the prestressing wires of the individual layers with the correct spacing adjacent and in superposition, and to ensure this correct arrangement on tensioning the prestressing wires and in the prestressed condition and also to secure the prestressing member consisting of the prestressing wire bundle or assembly between its end anchoring means on the container wall (cf. Moll Prestressed Concrete, pages 170 to 174 and Leonhardt Prestressed Concrete in Practice, 2nd Edition, pages 527 to 544).

SUMMARY OF THE INVENTION By means of the invention, these difficulties are overcome and it is made possible, using prestressing bands extending in the peripheral direction on the outer side of the wall of a pressure container and which may, if so desired, consist of a plurality of prestressing wires of any desired type and shape, for example, cold drawn or finally tempered prestressing wires or strands and which may be arranged for example in 20 or more superposed layers and, optionally, in any position in a plurality of adjacent lines, to secure these said prestressing bands adjacent eachother and one above the other in a simple manner, while ensuring the correct arrangement of the said prestressing bands, to tension them and to secure them on the container wall both during the securing of the individual layers and also, finally, as anentire prestressing band bundle or assembly. With this arrangement, the securing of the prestressing bands is intended, not only (as in the case of the pressure containers mentioned as known) to serve for preventing the unwinding of a prestressing wire in the event of rupture thereof, but'also, in addition thereto, there are to be provided clamping means which are arranged between the conventional end anchoring means or also without the latter and which ensure the correct mode of extending of the prestressing bands or of the prestressing wires thereof, in predetermined spaced relationship, i.e., both juxtaposed and superposed, and at the same time ensure ordered introduction of the prestressing forces into the container walls. This is of special significance relative to the prestressing process known as the so-called pilaster strip process wherein a prestressing member or a plurality of prestressing members extend, as a surrounding or embracing arrangement, about the container through the agency of ends which cross over each other and pretensioned and anchored against anchoring projections (the so-called pilaster strips) attached on the container. It is true, that with this arrangement, the introduction of large prestressing forces is made possible, but there is also the disadvantage that the prestressing condition of the lateral walls of the container or of the container shell is, apart from the fact that the external shape thereof depends to a considerable extent on the prestressing process and is not directed to the achievement of the statically most advantageous condition, greatly disturbed by the pilaster strips. Furthermore, due to the mutual over-engagement of the prestressing members in the zone of the pilaster strips, which generally have a length ,of one meter and more, a considerably larger quantity of prestressing steel is required. These disadvantages are also overcome by the invention.

In solution of the above problems, the invention consists, in connection with a pressure container designed in the manner discussed at the outset and having peripherally extending prestressing bands arranged in a plurality of layers lying radially one above the other and, within the layers, optionally positioned in a multiplicity of lines in side-by-side relationship, in that the prestressing bands or the prestressing wire bundles or assemblies formed by the prestressing band layers and arranged in adjacent lines, are anchored on the container walls by clamping anchoring means which extend-along substantially the entire wall height, i.e., vertically or substantially vertically peripherally spaced from each other, and each of which is formed by anchoring strips in the form of a base strip arranged on the inner side of the innermost layer, a pressure strip bearing against the outer side of the outermost layer of the prestressing bands, clamping strips arranged between the individual layers of the prestressing bands and clamping bolts or pins made from high-tensile stress steel, arranged between each two adjacent prestressing bands or lines extending through all the anchoring strips and the clamping force of which is directed at right angles to the tensioning force of the prestressing bands and parallel to the bearing force of the associated clamping anchoring means.

Clamping anchoring means for prestressing wire bundles are, it is true, known. In these known clamping anchoring means, however, the bearing force extends parallel to the prestressing force, whereas the bearing force in the case of the clamping anchoring means (anchoring strips) designed according to the invention extends at right angles to the prestressing force. In the event of rupture of individual prestressing bands, the anchoring strips operate furthermore in the same manner as the known clamping anchoring means.

An anchoring means has furthermore been proposed wherein the wires of a bundle are retained, layerwise, between clamping plates, under the clamping pressure of a high-tensile stress clamping member and the clamping plates and also pressure plates are prolonged beyond the end of the wires. This anchoring means, however, constitutes a clamping member stack whose retaining force extends parallel to the tensioning or prestressing force. A bearing force which, as in the case of the anchoring strips on the pressure container according to the invention, extends parallel to the clamping force of the clamping member is, in this case, not provided.

According to a further feature of the present invention, the construction may be such that the number of layers of the prestressing bands or prestressing band bundles extending in the peripheral direction decreases upwardly on the container and the outer pressure strip and also the clamping strips of each clamping anchoring means consist of strip sections adjoining each other in the longitudinal direction, the length of which corresponds in each specific case to that height of the container wall in which the number of prestressing band layers remains uniform, and which, at their upper end in each specific case at which said end they engage somewhat over the lower end of the strip section following in the upward direction, are pressed on this strip section by one of the clamping bolts or pins.

The anchoring strips are arranged, at least once per turn of the prestressing strips but preferably several times, for example with angular spacing of 90.

In the case of a pressure container designed in accordance with the invention, the prestressing bands are, with predetermined spacing, layerwise between the substantially vertically extending anchoring strips, jammed or secured on the container walls under the pressure of high-tensile stress clamping bolts or pins. The length of the strip sections of the anchoring strips may, with this arrangement, be selected to correspond to the requirements prevailing in each specific case and may for example have the convenient measurement of one and a half meters. With this arrangement, the length of the strip sections may, however, be so selected that a form of graduation of the prestressing bands is achieved which corresponds to requirements, for example, graduation from below upwardly. The spacing of the high-tensile stress clamping pins depends on the width of the prestressing bands, whereas the length of the clamping pins depends on the number of clamping band layers arranged radially one above the other. Due to the anchoring strips, it is made possible to arrange the prestressing bands extending in the peripheral direction of the container between the individual anchoring strips, with or without contact with the container walls. Furthermore, due to the use of the anchoring strips on the pressure container according to the invention, it becomes easier to achieve the result that the basic or cross-sectional shape of the pressure container may, to correspond to the conditions obtaining in every specific case, have a shape deviating from cylindrical shape and be designed, for example, in the form of a polygon. The container walls may, furthermore, be tied around" with prestressing bands or prestressing band bundles over their entire height or over component zones of their height if, for example, it is necessary that space should remain free for pipe passages in the container walls. In all these cases, due to the anchoring strips according to the invention, ordered introduction of the prestressing forces into the container walls is assured.

In the case of a further form of embodiment of the invention, it is possible to arrange between the anchoring strips, deflecting members which again are substantially vertical and which may be designed to correspond to the anchoring strips but serve merely for securing the portions of the prestressing bands or prestressing band bundles located between the anchoring strips relatively to the container walls. These deflecting strips assist in the order introduction of the prestressing forces into the container walls, since they transmit the prestressing forces between the anchoring strips, again in a manner which is capable of being accurately determined, in the radial direction on to the container walls. Since the deflecting strips are not required to take up any substantial anchoring forces, the pins or bolts securing them to the container walls do not require to be designed as clamping bolts having tightening nuts, but merely as spacer bolts or pins for securing the position of the lines disposed in juxtaposition in a prestressing band bundle. No special demands as to quality are made on spacer pins or bolts of this kind. The deflecting strips guide the prestressing band bundles into the zones located in each specific case between two anchoring strips and may also be used for preventing these zones from bearing directly on the container walls. Thus, as seen in plan view, for example in the case of a container of circular cross-section, the prestressing band extent does not require forming a circular ring but may for example be a uniform polygon. The basic strips of the anchoring strips and of the deflecting strips may bear on pressure distributing plates in order that, on introducing the prestressing forces into the container walls, no local overstressing of the container material may take place.

The prestressing bands may consist in each case of only one prestressing wire or of a plurality of juxtaposed prestressing wires. They may be wound, layerwise, using machines which are known per se or specially designed for this purpose, about the container walls and, at the same time be so tensioned that no friction losses are caused. The prestressing bands may furthermore be preferably so arranged that they are tensioned or prestressed in every case from one anchoring strip to another. Before the commencement of the winding work, first of all the inner basic strips of the anchoring strips and, where appropriate, the basic strips of the deflecting strips are attached to the outer face of the container wall, for example, in such thickness and with such spacing that the prestressing wires of the first layer do not at any point contact the circular-cylindrical or polygonal container walls. The prestressing band may then first of all, be anchored at its commencement portion between two anchoring strips, with the aid of a conventional end anchoring means, to the container walls and guided between the first and second clamping pins of the first anchoring strip and, subsequently, between the clamping pins of all the remaining anchoring strips and, where appropriate, the spacer pins of the deflecting strips, as far as the anchoring strip located, in the winding direction, before the first anchoring strip. Since, at the position of the first anchoring strip, the intermediate space between the first and the second clamping pins is already occupied by the initial zone of the prestressing band, the prestressing band is then guided at the first anchoring strip between the second and third clamping pins of the first anchoring strip. For example, winding is meanwhile effected from below upwardly. This procedure is repeated sufficiently often until the entire basic strip is occupied by the prestressing band over its entire height. Then, when what is concerned is a prestressing strip of limited length for only one layer over the entire container height or only a portion thereof, the free end of the prestressing band may be anchored to the container walls by means of a conventional end anchoring means and, in the case of all the anchoring strips and where appropriate deflecting strips, it is possible to fit the clamping or intermediate strips determining the radial spacing between the individual layers of the prestressing bands of each bundle of prestressing bands. The second prestressing band layer is then wound in the same manner on the clamping or intermediate strips, during which procedure the prestressing band may, when winding one turn, be tensioned or prestressed again continuously or from one anchoring strip to another. The clamping strips are, with this arrangement, so designed at the anchoring strip points that they exert an influence on the prestressing bands under the action of the clamping pins, whereas the spacer pins of the deflecting strips or the deflecting points formed thereby require to be suitable only for correct guiding or deflection of the prestressing band. if, however, the prestressing strip is of greater length and it is possible to wind from it, for example, two or more layers over a component zone of the height of the container walls or also over the entire height thereof, then the prestressing strip may, after winding has been effected from below upwardly, also be further extended, endlessly, into the second and where appropriate from the latter into a following layer, after, following the attachment of the first or innermost layer, at all anchoring strip points, the corresponding clamping strips and where appropriate, at the deflecting points, also the intermediate strips have been attached. In every case, the individual prestressing band layers may extend about the container walls helically in the manner of a single-pitch or multiple-pitch screw, the prestressing band (as explained) either ending after the formation of only one layer in each case and being anchored by means of a conventional end anchoring arrangement, or traveling further, endlessly, into the next layer or layers.

When applying the invention, the prestressing bands may, by means of the anchoring strips, already be jammed fast or secured temporarily, during the winding work, as an interim anchoring arrangement. After conclusion of the entire winding, they are then finally jammed fast by the outer pressure strips of the anchoring strips. The pressure strips are so dimensioned in respect of their thickness that they are able to laterally transfer the screw pressure of the clamping pins to all lines of the prestressing band or bands.

The special advantage of the invention consists in that the number of prestressing band layers is practically unlimited. Thus, any necessary tensioning or prestressing force which may be required in the peripheral direction of the container may be produced, whereby, in contradistinction to known processes, one prestressing band position after another may be produced without it being necessary to allow for example a guniting (cement gun) layer to set, as an intermediate layer. The anchoring strips, with their base and clamping strips, and also the clamping pins and, where appropriate, the deflecting strips with their base and intermediate strips and the spacer pins thereof, guarantee meanwhile accurately determined arrangement of the prestressing bands in predetermined spaced relationship, i.e., juxtaposed and superposed, and also introduction of the prestressing forces into the container walls at predetermined introduction points, the result being a satisfactorily ordered form of introduction. Where necessary, furthermore, subsequent bonding may be effected or an inspection may at any timebe made, for the purpose of supplementing the anti-rust treatment. The prestressing bands according to the invention are furthermore free from pilaster strip anchoring arrangements and constitute an annulus which, from the viewpoint of forces, is closed in itself, or a corresponding polygon, within which the replacement or post-tensioning or prestressing bands or elements thereof is possible. For the application of measures tending to diminish friction, all the prestressing band points are readily accessible. Apart from the end anchoring means of the prestressing band or bands, there is provided between the latter, due to the action of the anchoring strips or the strip sections thereof, at least one once-only" clamping anchoring arrangement which, in the case of prestressing strips wherein the number of layers decreases from below upwardly, due to the sections of the anchoring strips engagingover at their ends, forms a species of coupling-clamping anchoring arrangement or nodal clamping anchoring arrangement. With this arrangement, the base, clamping and pressure strips of the anchoring strips may also be ribbed or grooved, if so required they may also be designed to be subdivided and may be used not only for prestressing irons having a smooth surface, for example smooth round or flat wires, but also for ribbed prestressing wires, for example profiled round wires, corrugated round wires and ribbed or profiled flat wires of rectangular or oval cross-section, and furthermore also for strands and cables. lf ribbed prestressing wires are used, the base, clamping and pressure strips of the anchoring strips and, where appropriate, the base and intermediate strips of the deflecting strips may be provided with simple, plane clamping faces, whereas, when use is made of prestressing irons having a smooth surface, they are preferably grooved, in order to increase friction.

As already mentioned, the prestressing bands may be constituted by prestressing or spiral prestressing bands arranged individually one over the other in the direction of the container height and each being closed in itself from the viewpoint of forces, or by single-pitch or multiple-pitch spirals (possibly of the progressiveratio type) continuous over predetermined height zones or over the entire height of the container. In the case of small cross-sectional dimensions of the prestressing bands or of the prestressing irons arranged in them, in parallel juxtaposition and where appropriate in a plurality of layers one above the other, extremely high annular prestressing force concentrations are possible. For example, a prestressing band bundle may comprise layers of prestressing wires obtainable under the commercial designation Sigma Oval 40 and, at the same time, in respect of the immediate spaces or the clamping or intermediate strips between the layers, have a radial thickness of only 1.15 m. With this arrangement, a breaking load of 36,000 Mp per stg. meter of the container may be taken up. The prestressing bands arranged side-by-side or one above the other in the direction of the container height are, by means of the anchoring strips and the clamping anchoring effect thereof and possibly also by the deflecting strips, non-positively connected together within themselves, i.e., with reference to their prestressing wires, and also one to another. This constitutes a considerable advantage since, for example in the case of the rupture of a prestressing wire or prestressing band, the prestressing forces previously resisted by the latter are distributed to the adjacent prestressing wires or prestressing bands. At the same time, the spacing of the prestressing bands permits accurate monitoring and, where necessary, entirely satisfactory subsequent bonding.

According to the invention, the clamping force is not applied on the clamping pins, for the final securing of the anchoring strips, until all the prestressing bands engaged by one clamping strip have been fitted and tensioned or prestressed. With this arrangement, it may, before applying the final forces, be advantageous to subject the individual prestressing bands or the prestressing band assemblies formed by them, by prestressing in the radial direction, to increased clamping pressure. Due to the relative ductility of the upper pressure strip in each case and of the clamping strips, the prestressing may be effected for example by means of a hydraulic press acting in each case only on one prestressing band bundle and which is arranged for example on two bolts secured in the container walls in the zone of the particular clamping anchoring means and, first of all without the influence of the clamping bolts or with the clamping bolts only loosely inserted, radially compresses the prestressing band bundle. Only after this pre-pressing has been effected are the clamping bolts tightened, the latter serving therefore not for the compression of the prestressing band bundle or for the embedding of the profiling on the prestressing wires or the clamping strips, but merely for retaining a compressed bundle, in the compressed condition, with the large shearing bond produced by the prepressing.

In the case of a further form of embodiment of the invention, the clamping strips of the anchoring strips and, where required, also the intermediate strips of the deflecting strips, may be formed on both sides with grooves which, in cross-section, are substantially smaller than the pre-stressing irons or wires of the prestressing bands. Such grooves facilitate, on compressing the prestressing band bundle, the deformation of the clamping or intermediate strips which are made from a softer material, for example steel or plastics, so that the harder prestressing irons are pressed into these strips and the friction and retaining force between the strips and the prestressing irons is increased.

The invention may be applied to pressure containers of the most widely varying types. The following are examples of possible fields of application: pressure containers for nuclear reactors, where appropriate, including heat exchangers, pressure containers for receiving turbines, pressure containers for hydrogenation plant (conventional reactors for the chemical process technique) and protective containers, made from prestressed concrete, for reactor installations.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic elevation of a pressure container according to the invention, having a multiplepitch spiral prestressing band,

FIG. 2 is a detail from FIG. 1, the pitch of the spiral prestressing band being replaced by a stepped arrangement (so-called progressive-ratio winding),

FIG. 3 is a vertical section through a container wall having prestressing band bundles arranged on its outer surface,

FIG. 4 is an enlarged vertical section through an anchoring strip in the zone of a pressure container, wherein 10 layers of prestressing bands are arranged radially one above the other and in five lines side-byside,

FIG. 5 is an elevational view of the clamping arrangement according to FIG. 3,

FIG. 6 shows the anchoring of a clamping bolt or pin foot nut in the shuttering or fonnwork for a concrete container (condition before concreting),

FIG. 7 shows in elevation a tensioning or prestressing apparatus for the section-wise tensioning or prestressing of the individual layers of the prestressing bands,

FIG. 8 shows the prestressing apparatus according to FIG. 6, in an external elevational view,

FIG. 9 is an elevation view from the outside of a portion of a plurality of anchoring strips, according to the invention, and

FIG. 10 shows a vertical section of the prestressing reinforcement diagrammatically illustrating such anchoring strips as contain various, strong layers of prestressing bands.

DETAILED DESCRIPTION Whereas, as mentioned hereinabove, FIG. 1 relates to a spiral winding and FIG. 2 to a progressive-ratio winding, FIGS. 3 to 10 apply both to the spiral and also to the progressive-ratio winding.

The prestressing bands in the pressure container according to the invention belong to the type of prestressing members arranged on the external surface of the container which helically wind around the pressure container 10 which is, in plan view, for example circular or polygonal. In the case of the form of embodiment according to FIGS. 1 to 6, there are used multiple-pitch prestressing bands 11 each of which consists of four prestressing irons or

prestressing wires

1, 2, 3 and 4 extending one above the other in the direction of the height of the container walls 5. As shown in FIG. 3, the prestressing bands are arranged in the form of prestressing band bundles or assemblies consisting, in the lower portion of the pressure container and in the radial direction, of ten layers of prestressing bands 11 and fewer prestressing band layers decreasing upwardly in accordance with specific requirements. The arrangement of the

prestressing wires

1, 2, 3, 4 in juxtaposition and superposition will be clear, individually, from the section according to FIG. 3. In FIG. 1, in order to make the illustration clearer, there is shown only a single layer of prestressing bands 11 which, however, together with further prestressing bands of the same type, may be arranged, for example as an endless prestressing band or provided with butt joints over the entire height of the container walls 5 or over only a partial zone thereof. The multiple-pitch design of the prestressing band or bands 11 having, for example, four

prestressing wires

1, 2, 3, 4, is not critical. Instead of this, the prestressing band or bands 11 could consist in each of the layers, of only one single prestressing wire in each case.

FIG. 4 shows, by way of example, an anchoring strip according to the invention for prestressing band bundles or assemblies 11, each of which constitutes a socalled prestressing band line. Each line contains, with this arrangement, 10 layers or prestressing bands 11 eaCh of which consists of four prestressing irons l, 2, 3, 4 of the Sigma Oval 40 St 145/60" type. The prestressing bands or strips according to the invention become progressively more economical in proportion as the number of prestressing band layers increases. For example, the height of a prestressing band bundle, in the case of 100 layers, is approximately 1.15 m. The width of each prestressing band bundle or assembly, or of the prestressing band line formed thereby, of the type shown in the Figure, occupies about 7.5 cm., including the necessary clear spacing from the adjacent prestressing band line. With a permissible prestressing tension of 66 percent of the breaking strength (lower than the technical creep limit) it is possible, with 100 layers per meter of container height, to accommodate approximately 22,400 Mp of prestressing force. By suitable graduation of the number of prestressing band layers in the prestressing band lines, for example, in accordance with FIG. 3, the prestressing force may readily be adapted to local requirements.

Within the prestressing band lines 11, the spacing of the individual prestressing band layers is obtained by intermediate layers 12 of steel or plastic material which serve for transmission of the stressing forces to the concrete container and simultaneously constitute clamping strips for anchoring strips 13 used in accordance with the invention. These anchoring strips are arranged, at least once per turn, but preferably more frequently, with an angular spacing of for example FIG.-l shows, on the forward side of the container, for example, three anchoring

strips

13a, 13b and 13c for the prestressing bands arranged with spiral winding. Each turn or winding is engaged by one of the anchoring strips at least at the commencing and end portions and in this way joined together to constitute a ring or annulus which is closed from the viewpoint of forces.

The build-up of an anchoring strip 13 is shown by way of example in FIGS. 4 and 5. According to these Figures, each anchoring strip 13 consists of a base strip 14 arranged on the inner side of the innermost layer of the

prestressing wires

1, 2, 3, 4 of the prestressing bands 11, of a pressure strip 15 bearing against the outer side of the outermost layer of the prestressing wires and also of the clamping strips 12 arranged between the individual layers of the prestressing wires and the clamping bolts or pins 16 extending through corresponding bores formed in the

strips

12, 14, 15. The said clamping bolts are, in the embodiment illustrated, screwed into threaded members 17 which, as shown in FIG. 6, are secured to the shuttering or formwork 18, serving for pouring the concrete of the container walls, with the aid of an adjusting strip and a short screw and are provided with anchoring members 1? which are embedded in the concrete of the container walls. After the removal of the shuttering, the threaded members 17 remain, with the adjusting strips serving as a support member for the inner base strip 14 and simultaneously as a pressure distribution plate 30, on the structure. Instead of the final clamping bolts 16, it is also possible to use short clamping screws which are only temporarily required and are screwed into the threaded member 17, if the final clamping bolts should initially, excessively hinder the assembly work, due to their length.

In the case of the anchoring strips designed in accordance with the invention, the clamping force of the clamping bolts 16 is directed at right angles to the pretensioning force of the prestressing bands 1 1 and parallel to the bearing force at the anchoring points. In the example illustrated, for one prestressing band 11, the four prestressing irons or

wires

1, 2, 3, 4 are simultaneously introduced starting from four winding-off devices. The initial portion of the first layer of the prestressing band is anchored in any desired manner by the first clamping anchoring means 13a. There may then be applied to the second clamping anchoring means 13b a tensioning or prestressing apparatus 20 (as shown for example in FIGS. 7 and 8) and by means thereof the first or innermost layer of the prestressing wires of the prestressing band may be prestressed as far as the second anchoring strip 13b and anchored thereto by means of an interim clamping anchoring arrangement 22. The interim clamping anchoring arrangements comprise, save for the upper interim pressure plate, the clamping strips of the final anchoring strip itself and are used only for temporarily anchoring the layerwise applied prestressing force, on introducing the individual layers of a prestressing band at the introduction point. The upper interim pressure plate is formed with two bores for the adjacent clamping bolts, but exerts pressure on only one prestressing band assembly.

The individual layers of the prestressing bands may, alternatively, also be wound, under tension, endlessly about the container walls, in accordance with any one of the known processes.

The prestressing or tensioning apparatus shown in FIGS. 7 and 8 has a capacity of approximately 20 Mp. For the prestressing or tensioning of one prestressing band between two successive clamping anchoring arrangements, for example, for the prestressing or tensioning of the prestressing band 11a, the band is secured by a prestressed screw connection 21 to the clamping bolts 16 of the two adjacent prestressing bands. In the first layer, the force of the anchoring arrangements of the concreted-in threaded members (FIG. 7) is taken up, in all further layers that of the already introduced and prestressed layers of the adjacent prestressing bands. Under the prestressing apparatus, a slight degree of (lubricated) deflection of the prestressing band layer to be prestressed takes place, so that the tensioned anchoring arrangement (FIGS. 7 and 8) may readily be secured. The two hydraulic (doubleacting) presses in tandem arrangement now tension the prestressing band layer (intended pretensioning force 16.8 Mp). If the, the clamping anchoring arrangement 22 is attached inthe recess of the prestressing apparatus (FIG. 8), the tension anchoring arrangement is released, the prestressing apparatus is moved back, the lower pressure plate of the tension anchoring arrangement is removed and the prestressing apparatus is detached.

In this manner, each spiral prestressing band may be built in layer-wise and prestressed from one anchoring strip to another. Any prestressing band stacks which it may be necessary to provide, are provided for example with the aid of squeezer sleeves. Even in the case of, for example, I layers, the prestressing procedure involves no difficulty, since the adjacent prestressing bands are always used for taking up the counter force. Due to the provision of the interim anchoring arrangements migrating after the prestressing apparatus, a high degree of reliability is achieved when, in the case of multiple-pitch spiral prestressing bands, which are mutually offset, a plurality of laying and prestressing columns is simultaneously employed.

The frictional losses taking place between two clamping anchoring arrangements may be eliminated by known measures, since the prestressing band layer to be tensioned or prestressed is freely accessible over the entire length.

The finished prestressing reinforcement may either be treated (or post-treated) with an anti-corrosion medium or may be enveloped in concrete.

As can be seen in particular from FIGS. 9 and 10, depending on the special requirements prevailing, the number of layers of the prestressing bands of each prestressing band bundle or assembly 1 1 may be graduated to decrease in the upward direction. In the embodiment shown in FIG. 10, for example, there are arranged in the lower container zone layers followed by 18 layers, etc. With this arrangement, the outer pressure strips are built up from strip sections 25a to 25k, the length of which corresponds in each case to approximately that height of the container walls within the zone or range of which the number of prestressing band layers of the prestressing band bundle 11 remains uniform. The strip sections engage, through the agency of their upper end in each particular case, over the lower end of the strip section which follows in the upward direction and are firmly pressed on the latter by, in each case, one clamping screw. The clamping strips 12 arranged between the individual prestressing band layers have, in the corresponding height zones of the container walls, in the radial direction as seen from the exterior toward the interior, a length exceeding the length of the particular outer strip section by the amount of the height zone which follows in the upward direction, in which the number of prestressing bands remains uniform. For example, the clamping strip 12k following the outermost pressure strip 25k in the inward direction, has a length corresponding substantially to the length of the outer clamping strip 25k plus 25i.

What is claimed is:

1. In combination, a pressure container of generally cylindrical shape, prestressing bands peripherally wound on the container on the outer surface thereof in a plurality of turns for producing annular prestressing pressure in the container, said prestressing bands being arranged in a plurality of layers superposed radially one above the other, and anchoring means secured at a plurality of positions on the container for engaging said bands to clamp the same with radial bearing force against the container and for grouping said bands in rows running side by side around the container, said anchoring means comprising clamping and anchoring members extending transversely of said rows of bands and substantially axially along the entire length of the container on the outer surface thereof in circumferentially spaced relation, said clamping and anchoring members each being constituted by anchoring strips including a base strip arranged inwardly of the innermost layer, a pressure strip bearing against the outermost layer of the prestressing bands, clamping strips arranged between the individual layers of the prestressing bands, and clamping bolts attached to said container and extending radially between two adjacent rows of prestressing bands and passing through all the anchoring strips to produce a clamping force directed substantially at right angles to the prestressing force of the prestressing bands and parallel to the bearing force of the particular clamping and anchoring member, the number of layers of the prestressing bands extending in the peripheral direction decreasing in the direction of the height of the container, the outer pressure strip of each clamping and anchoring member comprising strip sections which are adjacent each other in the longitudinal direction and the length of which corresponds to that height of the container wall in which the number of prestressing band layers remains unchanged, and which are, at their upper end, at which they engage somewhat over the lower end of the strip section following in the upward direction, pressed on the said strip section by one of the clamping bolts.

2. The combination according the claim 1, wherein the clamping members are so peripherally spaced from each other, depending on the cross-sectional shape of the container, and the inner base strip of each of the clamping and anchoring members has a thickness such that the prestressing bands do not contact the container wall at any point and constitute as seen in plan view, a polygon which approximates a circle.

3. The combination according to claim 1, wherein said clamping bolts have inner ends anchored in the container and outer ends engaging the layers of outer pressure strips to press the prestressing bands and the anchoring strips of the clamping and anchoring members while forming a friction and shearing force bond.