EP0979332A1 - Method for making prefabricated structural elements, and prestressed structure produced with said elements - Google Patents

Abstract

A process of manufacturing concrete construction elements is provided. A first sheath is placed in a first mold, the first sheath connected at an end to a first sleeve applied against a wall of the mold, the sleeve engaging a positioning boss placed on the wall. Concrete is poured into the first mold and set to obtain the first element. The first element is extracted from the first mold and includes a contact face shaped by the wall. A second sheath is placed in a second mold, the second mold having one side formed by the contact face. The second sheath includes an end connected to a second sleeve held in position relative to the first sleeve by a positioning joint. Concrete is poured into the second mold and set to obtain a second element. The second element is extracted from the second mold by disengaging the positioning joint.

Description

 MANUFACTURING PROCESS

PREFABRICATED CONSTRUCTION ELEMENTS,

AND PRE-CONSTRAINED WORK MADE WITH SUCH ELEMENTS

The present invention relates to the construction of prestressed structures from prefabricated concrete elements combined.

The invention applies in particular, but not exclusively, to bridges constructed by cantilever with prefabricated segments with conjugate joints (see for example the article: "Evolution and recent developments of bridges with prefabricated segments" by Jacques Mathivat, Annales de l 'Technical Institute of Building and Public Works, Supplement to No. 342, September 1976, pages 21-32, or even patent application EP-A-0 462 350).

In this technique, the successively assembled elements (segments) of the bridge are produced one after the other, the front face of the element n serving to delimit the rear side of the mold for manufacturing the element n + 1. This guarantees the conjugation of the adjacent faces of the elements to be assembled. These faces are glued to each other during the installation of the element n + 1 on the site. Complementary reliefs are usually provided on these faces to facilitate their mutual positioning and to help support the element n + 1 before its final fixing.

These structures are frequently subjected to longitudinal prestressing using prestressing cables threaded in sheaths embedded in the concrete of several successive elements.

The realization of this prestressing is a delicate operation.

The positioning of the sheath sections in the elements must be very precise so that the prestressing cables can be threaded without difficulty. 2

The most difficult is to guarantee the tightness of the sheath at the interfaces between elements. This tightness is necessary to ensure the durability of the prestress subjected to the risks of infiltration at the level of the joint between the elements. The joint can be produced according to two methods: "dry joint" when the concrete faces are juxtaposed without interface product; or "glued joint" when an interface adhesive is placed in line with the joint. In this second case, the sealing also meets the need to prevent the epoxy glue or the like placed between the elements from entering the sheaths and hindering the introduction of the cables. On the other hand, the sheaths are generally injected with a filling product (cement slurry, grease wax, resin, etc.) used in particular to protect the cables against corrosion. This product must not escape outside the sheath during injection.

Certain areas of the structure may have a fairly high density of sheaths, and there is no guarantee that the epoxy adhesive will seal between these sheaths. This results in the serious risk that the grout injected under pressure into a sheath will infiltrate into one or more neighboring sheaths, where the injection then becomes very difficult or even impossible. In general, pneumatic tests are carried out to ensure the tightness of the prestressing ducts before installing the cables and injecting the grout. If leaks are detected between certain sheaths, it is necessary to inject the grout very carefully so as to try to have a single advancement front of the grout in these different sheaths. The result is extremely complicated injection procedures that are difficult to master.

The solutions consisting in interposing O-rings around the sheaths between the mating faces of the elements are not reliable in terms of sealing, these seals being able to be moved during the positioning of. 3 the element n + 1.

Patent application FR-A-2 596 439 describes a connection device between sections of prestressing sheath, comprising a cylindrical sleeve engaged between the mouths of two contiguous sections to ensure the continuity of the sheath, and an elastic seal surrounding the sleeve cylindrical for sealing and compensating for irregularities in the positioning of the blocks and their dimensional deviations. It has also been proposed to introduce a sheath pleated longitudinally in the sheath after bonding, this sheath being brought into line with the previously assembled contact surfaces and then expanded using a pneumatic device to be bonded to the internal wall of the sheath using an adhesive placed at the bottom of the folds. This method is very complex to implement, moreover impossible when the sheaths are not straight. In addition, it does not prevent glue infiltration in the sheath during the assembly of the elements.

An object of the present invention is to propose a simple and effective solution to the problems encountered in carrying out the prestressing of structures constructed from conjugated prefabricated elements. The invention thus provides a method of manufacturing concrete building elements comprising at least a first and a second conjugate elements. This method comprises the following steps: placing in a mold at least a first section of prestressing sheath having one end connected to a first sleeve applied against a wall of the mold, the first sleeve having an internal shape engaging on a positioning stud disposed on said wall; - pouring concrete into said mold so as to obtain the first element after setting of the concrete;

- extract the first element from the mold, including one contact face has been shaped by said wall;

- constitute a second mold, one side of which is formed by said contact face of the first element;

- have in the second mold at least a second section of prestressing sheath having one end connected to a second sleeve held in position relative to the first sleeve by means of a positioning connector retained elastically in at least one of the first and second sleeves; - pour concrete into the second mold so as to obtain the second element after setting of the concrete; and

- Extract the second element from the second mold, by disengaging the positioning fitting from at least one of the first and second sleeves. The positioning fitting can be the same part as the fitting which will seal between the sleeves after the final assembly of the elements. In this case, the fitting can be left in place in one or other of the two sleeves during the storage of the elements.

The sleeves and the connector ensure precise and correct positioning of each section of sheath in each element, as well as the correct alignment of the successive sections. The dimensional differences to be compensated are thus minimized.

During the assembly of two consecutive elements, the sealing connections, which are provided with the sleeves terminating the sheath sections on the face of one of the elements, engage in the sleeves terminating the corresponding sheath sections of the other element. This engagement seals the sheath with respect to the adhesive, one of the complementary faces of which is generally coated. It also ensures the absence of communication with the outside or between neighboring sheaths when injecting the cement grout or other filling product into the sheaths.

The seal fitting can be a single 5 piece with one of the two sleeves. But it is preferably removably attached to one of the two sleeves, for example by screwing or by elastic interlocking. In preferred embodiments, the method of manufacturing concrete building elements according to the invention has one or the other of the following characteristics:

- The positioning pad can be provided with elastic hooking means which cooperate with an annular groove which has the internal shape of the first sleeve to hold it removably in the mold;

- The sleeve in which the positioning connector is elastically retained may have an angular opening of at least 30 degrees;

- The positioning connector can be retained elastically in each of the first and second sleeves;

- The positioning fitting can be screwed into one of the first and second sleeves;

- when a feature according to one of the two preceding paragraphs is provided, the positioning connector can be crossed by an orifice coaxial with the sleeves, of section at least equal to the internal section of the first and second sheath sections, and in this in this case, the positioning fitting is left in place in the first or second sleeve after the extraction of the second element.

The invention also relates to a construction work, comprising an assembly of prefabricated elements from a series of elements as defined above, the contact faces of the conjugate elements being applied against each other so that the sections of sheaths are arranged in the extension of each other to form complete sheaths, with fittings engaged in the sleeves to seal the adjacent sections of sheath, and in which 6 of the prestressing cables and a filling product occupy the interior of the sheaths.

Other features and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:

- Figure 1 is a perspective view of a prefabricated segment to which the present invention can be applied; - Figure 1A is a partial side view illustrating the assembly of two consecutive segments;

- Figure 2 is a sectional view illustrating the establishment of a sheath section in a mold for manufacturing a first element; - Figure 3 is a partial sectional view of the first manufactured element;

- Figure 4 is a sectional view illustrating the establishment of a second sheath section in a mold for manufacturing a second element; - Figure 5 is a partial sectional view of the second manufactured element;

- Figure 6 is a sectional view showing two alternative embodiments of the means for joining two sections of prestressing sheath; and - Figure 7 is a sectional view showing another alternative embodiment of these means.

The invention is described below in its application to bridges with prefabricated segments with conjugate joints. Such a segment 1 is shown in FIG. 1.

Element 1 has the general shape of a box delimited internally by a base 2, laterally by two walls 3 symmetrically inclined, and above by an apron 4 extended laterally beyond the walls 3 to define the width of the bridge.

In the longitudinal direction, the element 1 is delimited by a rear face 6 and a front face 7 7 substantially parallel. The rear face 6 is intended to come into contact against the front face, of complementary shape, of the previous element installed on the structure under construction (in the case of the first element installed on a pier of the bridge, the complementary face belongs to this stack). Similarly, the front face 7 of the element 1 is intended to receive the rear face of the next element which will be put in place.

The contact faces of complementary shapes of the adjacent elements are provided with reliefs 8a, 8b ensuring good relative positioning of the elements when they are brought together. In the particular example shown in FIGS. 1 and 1A, these reliefs are located on the end faces of the side walls 3 of the elements, and have the shape of a part of bosses with trapezoidal profile 8a produced during molding on the front face 7a of the element la, and on the other hand of recesses with a complementary trapezoidal profile 8.8j made during molding on the rear face 6, 6b of the element 1, 1b. When an assembly adhesive is used, it is for example an epoxy resin with which one or the other of the two complementary faces is coated before assembly. After its installation, the element 1,1 £> is clamped against the preceding element 1a, so that the recesses 8,8jb with trapezoidal profile formed on its rear face 6, 6b provide support on the complementary bosses 8a of the front face 7a of the preceding element 1a to support it before setting the glue. After setting the glue, the reliefs at least partially resume the shearing force exerted at the joint by the load of the work

The element 1 comprises a number of longitudinal sheath sections 10, intended to receive prestressing cables. These cables are anchored to the structure at their ends by means of suitable anchoring devices. Some of these anchors 11 8 may possibly be arranged on bosses 12 provided inside the box shape of the element. The sheath sections 10 open onto the rear face 6 and / or onto the front face 7 of the element. It is important to ensure the continuity and tightness of each prestressing sheath at the level of the faces in contact with the adjacent elements. For this, use is made, according to the invention, of connection pieces (sleeves and fittings) which are described below. After the element has been put in place, it is pressed against the previous element, at least until the assembly adhesive has taken hold. This tightening can be carried out by installing certain prestressing cables if anchoring devices 11 oriented towards the rear are provided on the element. Otherwise, or in addition, external actuators are used to clamp the elements together.

Once the successive sections of a complete sheath have been assembled, the tightness of this sheath is checked using a pneumatic device. We can then thread the strands of the prestressing cable into the sheath, tension them, anchor them at their ends, then inject a filling product such as a cement grout into the sheath to fill the voids and protect the cables against corrosion.

The successive elements 1 are prefabricated in molded concrete. Figures 2 to 5 illustrate the prefabrication of two consecutive elements la, lb.

To manufacture the first element 1a, a mold having the required shape is used. On the front side of the element, the mold is delimited by a metal wall 15 (FIG. 2) of generally planar shape, having complementary recesses of the bosses 8a at the prescribed locations. Positioning pads 16 are fixed on the inside of the wall 15, for example by welding. These studs 16, of generally cylindrical shape, serve to 9 install in the mold the sheath sections 10a of the first element la.

The front end of each sheath section 10a is engaged in a sleeve 18a up to an internal stop 19a provided in this sleeve. The seal between the sheath section 10a and the sleeve 18a is produced in a conventional manner using a heat-shrinkable sheath or an adhesive tape 20.

The sleeve 18a is made of a sufficiently rigid material so as not to deform when the concrete is poured into the mold, for example a plastic material such as a high density polyethylene.

Beyond the stop 19a, the sleeve 18a has an enlarged portion 21a of a shape adapted to come into engagement on the positioning stud 16. The sleeve 18a connected to the sheath section 10a is engaged on the stud 16 by an operator. The sleeve 18a is thus precisely positioned against the wall 15 of the mold, and retained in this place by elastic hooking means provided on the positioning pad 16. These means may comprise an elastic member 22 housed in an annular groove 23 provided outside the cylindrical shape of the positioning pad 16, and cooperating with another annular groove 24a provided in the inside shape of the enlarged portion 21a of the sleeve 18a. The member 22 consists for example of an O-ring spring with flat turns which can be crushed when it is compressed radially.

Once the different sheath sections 10a of the element 1a have been installed in this way, the concrete is poured into the mold. After setting, the element 1a can be extracted from the mold, the wall 15 being removed by tearing off the positioning pads 16 from the sleeves 18a. This wall 15 releases the front face 7a of the element. The front end 25a of the sleeve 18a, which was applied against the wall 15, lies in the plane of the front face 7a. The constitution of the element la at 10 in the vicinity of the front end of a section of sheath 10a is shown in FIG. 3.

The front face 7a of the element 1a serves to delimit the rear side of the mold for manufacturing the next element 1b (FIG. 4).

For mounting the sheath sections 10 £> of the element lb, a positioning connector 30 is engaged in the enlarged portion 21a of each sleeve 18a appearing on the front face 7a of the first element la. This connection 30 can be made of a more flexible material than the sleeve 18a, for example of a low density polyethylene having a modulus of elasticity of the order of 500 N / mm ² .

A rear part of the connector 30 has an external shape corresponding to the internal shape of the enlarged portion 21a of the sleeve 18a, in particular with an annular bead 31 complementary to the annular groove 24a of the sleeve 18a. This rear part of the connector 30 is pressed into the enlarged portion 21a of the sleeve 18a, where it is held in place by the cooperation of the bead 31 with the annular groove 24a.

The other part (front) of the connector 30 protrudes beyond the front face 7a of the element la. This front part may have an outer contour of generally frustoconical shape provided with another annular bead 32. Preferably, this frustoconical shape, which converges away from the element, has a half-angle at the top β less than l 'angle θ formed by the sides of the trapezoidal profile of the reliefs 8a, 8b with the perpendicular direction of the end surfaces la, 6b, which ensures that the part 30 is not damaged during the handling of the element lj.

Each sheath section 10 & of the second element lb is engaged in another sleeve 18j up to an internal stop 19b, with a heat-shrinkable sheath or a 1 1 adhesive tape 20 for sealing between the sheath and the sleeve. Opposite the sheath section 10-, the sleeve 18 £> has an enlarged portion 21b whose internal shape is complementary to the external shape of the projecting front part of the positioning connector 30. In particular, this enlarged portion 21 £> has an internal annular groove 24i> which cooperates with the annular bead 32 of the positioning connector to hold the sleeve 18b against the sleeve 18a in the mold for manufacturing the second element (FIG. 4).

Once all the sheath sections 10jb of the second element have been put into place in the mold using the fittings 30 and the sleeves 18b, concrete is poured into this mold to produce the second element. After setting the concrete and extracting the mold, by tearing off the fittings 30 out of the enlarged portions 21 £> from the sleeves 18b, the second element lb has the configuration shown in FIG. 5 near the rear end of the sheath section 10 £ >, the sleeve 18 £> having its rear end 25 £> in the plane of the rear face 6b of the element.

The fact that the positioning connector 30 remains in place on the first element 1a rather than on the second element 1b results from the angular opening of the enlarged portion 21 £> of the sleeve 18j, which is larger than the angular opening of the enlarged portion 21a of the other sleeve 18a.

The positioning connector 30 remaining on the first element will serve as a sealing connection between the corresponding sheath sections 10a, 10b during the assembly of the elements on the site. This connector 30 is thus provided with an orifice coaxial with the sheath sections 10a, 10b, the section of which is preferably at least equal to the interior section of these sheath sections. Due to its complementary external shape of the housing defined between the enlarged portions 21a, 21b of the sleeves, the relative elasticity of its material and of its 12 constant and relatively small thickness, the connector 30 undergoes a certain radial compression which seals the sheath at the interface between the elements la, lb. The angular opening of the enlarged portion 21b of the sleeve 18b, which corresponds substantially to the angle at the top 2β of the frustoconical front part of the connector 30 is preferably greater than 30 degrees. Thanks to this arrangement, the connector 30 can easily penetrate into its housing when the second element 1b is close to the first element 1a.

If the projecting front part of the connector 30 is damaged during storage of the elements, this connector 30 can be torn off from the sleeve 18a in which it is retained elastically, and replaced by another connector.

As a variant, the positioning connector 30 used during the prefabrication of the elements 1a, 1b could be distinct from the sealing connector installed for the final assembly of the elements, provided that this connector 30 correctly positions the sleeve 18b in the mold for manufacturing the second element.

In another alternative embodiment, the positioning and sealing connection could be in one piece with one of the two sleeves. For example, the first element could be manufactured in the manner illustrated with reference to Figures 2 and 3 (but preferably with sleeves 18a whose enlarged portion 21a would have a larger angular opening), and the second sleeves connected to the rear ends of the sheath sections 10j could be extended by a more flexible rear part whose external contour would be complementary to the internal shape of the enlarged portion 21a. So that this rear part is made more flexible, its thickness can be reduced compared to the rest of the sleeve, and / or make this sleeve from two materials having different elastic moduli. 13

With such an embodiment, the number of parts required to make the seal is minimized.

In other variants (FIG. 6), the positioning and / or sealing fitting is screwed into one or the other of the two sleeves.

In the embodiment illustrated in FIG. 6, the positioning and sealing fitting 50 has a cylindrical rear part engaged in the sleeve 38a to which the sheath section 10a of the first element is connected, and a frustoconical front part provided with an outer annular bead 52. Between these two parts, the connector 50 has a transverse shoulder 54 which abuts against the front end 45a of the sleeve 38a and against the front face of the first element. The cylindrical part of the connector 50 is provided with a female thread 53 complementary to a male thread 46a provided inside the sleeve 18a. Thus, the connector 50 can be screwed into the first sleeve 38a, the threads contributing to the seal. In the frustoconical part of the connector 50, the seal results from the engagement of the bead 52 in the groove 44b provided inside the enlarged portion 4.1b of the second sleeve 38b.

In the example shown in the lower part of FIG. 6, the seal is further reinforced by the fact that the two ends of the connector 50 have thinned lips 55a, 55i> which flex elastically inwards when the connector 50 is installed in sleeves 38a, 38.b. This sag can be caused by curved internal surfaces provided in the sleeves 38a, 38b, on the back of the stops 39a, 39 £> respectively receiving the ends of the sheath sections.

In the alternative embodiment shown in the upper part of FIG. 6, an annular housing 47a, 47 £>, open towards the front side, is provided in the internal shape of the sleeve 38a, 38b, on the back of the stop 1 4

39a, 39b. The two ends of the positioning and sealing fitting then compress flat seals 48a, 48 & placed in the housings 47a, 41b. In the embodiment illustrated by the figure

1, the two sleeves 58a, 58b are parts having the same shape:

- A cylindrical part 59 for receiving the end of the sheath sections 10a, 10b; - An internal shoulder 60 at the end of the cylindrical portion 59, against which abuts the end of the sheath section;

- A constriction 61 for attaching the sleeve to the positioning stud 16 on the wall 15 delimiting the front side of the mold, the toric spring 22 of the stud 16 engaging in the annular groove formed behind the constriction 61;

- A frustoconical part 62 flaring outwards and extending from the constriction 61 towards the front end of the sleeve 58a, 58b;

- In the frustoconical part 62, a cylindrical recess 63 provided with an internal thread 64 towards the front end of the sleeve, and an annular groove 65, and the bottom of which comprises an annular rim 66 directed towards the front end.

The positioning and sealing fitting 70 has a general shape complementary to that of the frustoconical parts 62 and of the cylindrical recesses 63 of the two facing sleeves, with a central cylindrical bore having approximately the internal section of the sheath sections. To optimize sealing, the connector 70 is provided with a series of radial notches 71 in the frustoconical part of its outer surface which make it more flexible, with two annular beads 72 which engage in the corresponding grooves 65 of the two sleeves and, on its two end faces, two 1 5 respective annular grooves 73 which allow bending of the portions having the beads 72 so that they engage elastically in the grooves 65 of the sleeves, and which define, towards the inside of the fitting, annular lips 74 coming s' apply tightly against the annular flanges 66 of the sleeves.

On only one of its sides, the connector 70 has a thread 75 intended to be screwed onto the thread 64 of one of the sleeves. This screwing is carried out on the sleeve of the element produced first, after it is removed from the mold. On the opposite side of the connector 70, there is no thread 75, to allow easy assembly of the elements. The advantage of the embodiment of Figure 7 is its lower cost taking into account the identity of the two sleeves 58a, 58b used.

Claims

1 6RE VENDICATIONS 1. A method of manufacturing concrete building elements comprising at least a first and a second conjugate element (la, lb), the method comprising the following steps: placing in a mold at least a first section of prestressing sheath (10a ) having one end connected to a first sleeve (18a; 38a; 58a) applied against a wall (15) of the mold, the first sleeve having an internal shape engaging on a positioning stud (16) disposed on said wall; - pour concrete into said mold so as to obtain the first element (la) after setting of the concrete; - extracting from the mold the first element, one contact face (7a) of which has been shaped by said wall; - constitute a second mold, one side of which is formed by said contact face of the first element; - have in the second mold at least a second section of prestressing sheath (10 £>) having one end connected to a second sleeve (18.b; 38 £>; 58-) held in position relative to the first sleeve by means a positioning connector (30; 50; 70) elastically retained in at least one of the first and second sleeves; - pour concrete into the second mold so as to obtain the second element (lb) after setting of the concrete; and - Extract the second element from the second mold, by disengaging the positioning fitting from at least one of the first and second sleeves. 2. Method according to claim 1, wherein the internal shape of at least one of the first and second sleeves (18a, 18 £>;38b; 58a, 58 £>) comprises an annular groove [24a, 24b; 44b; 65) to receive a bead 17 complementary annular (31,32; 52; 72) of the fitting (30; 50; 70). 3. Method according to claim 1 or 2, wherein the positioning pad (16) is provided with elastic hooking means (22) which cooperate with an annular groove (24a; 44a) that has the internal shape of the first sleeve ( 18a; 38a; 58a) to detachably hold it in the mold. 4. Method according to any one of claims 1 to 3, wherein the sleeve (182 ?; 382 ?; 582?) In which the positioning connector (30; 50; 70) is elastically retained has an angular opening of at least 30 degrees. 5. Method according to any one of claims 1 to 4, wherein the positioning connector (30) is retained elastically in each of the first and second sleeves (18a, 182?). 6. Method according to any one of claims 1 to 4, wherein the positioning connector (50; 70) is screwed into one of the first and second sleeves (38a; 58a). 7. The method of claim 5 or 6, wherein the positioning fitting (30; 50; 70) is crossed by an orifice coaxial with the sleeves (18a, 182 ?; 38a, 382 ?; 58a, 582?), Of section at least equal to the internal section of the first and second sheath sections (10a, 102?), And in which the positioning fitting (30; 50; 70) is left in place in the first or second sleeve after the extraction of the second element (12?). 8. Method according to any one of claims 1 to 7, wherein the first and second sleeves (58a, 582?) Are parts having the same shape. 9. Method according to any one of claims 1 to 4, wherein the positioning connector is in one piece with the first or the second sleeve, and is crossed by an orifice coaxial with the sleeves, of section at least equal to the inner section of the first and second sheath sections. 10. Construction work, comprising an assembly of prefabricated elements produced by means of a method according to any one of claims 1 to 9 and comprising at least one pair of conjugated concrete elements (la, 12?) Having two respective contact faces of complementary shapes (7a, 6b) and comprising at least one pair of respective prestressing sheath sections (10a, 102?), The contact faces (7,6) of the conjugate elements (1) being applied one against the other so that the sheath sections (10) are arranged in the extension of each other to form complete sheaths, with fittings (30; 50; 70) engaged in the sleeves (18a, 182 ?; 38a, 382 ?; 58a, 582?) to seal the adjacent sheath sections, and in which cables prestressing and a filling product occupy the interior of the ducts. 11. The structure as claimed in claim 10, in which an assembly adhesive is located at the interface of two conjugate elements, said sleeves and fittings preventing this adhesive from entering the sheaths.