CN210916983U

CN210916983U - Prestressed concrete beam

Info

Publication number: CN210916983U
Application number: CN201921717879.6U
Authority: CN
Inventors: 刘其伟; 罗文林; 王成明; 葛万光
Original assignee: Nanjing Brgtec Engineering Technology Ltd
Current assignee: Nanjing Brgtec Engineering Technology Ltd
Priority date: 2019-10-14
Filing date: 2019-10-14
Publication date: 2020-07-03
Anticipated expiration: 2029-10-14

Abstract

The utility model relates to a prestressed structure technical field discloses a prestressed concrete roof beam. The prestressed concrete beam comprises a prestressed tendon, a protective device and an anticorrosive material, wherein the prestressed tendon comprises a prestressed failure section and a prestressed effective section; the protection device comprises a closed section and an open section, the closed section is sleeved on the prestress failure section, and the open section is sleeved on the prestress effective section; the anticorrosive material is filled in the closed section. The utility model discloses install protector on the prestressing tendons that needs force prestressing force inefficacy, this protector keeps apart prestressing tendons's prestressing force inefficacy section and concrete to realize prestressing force inefficacy's function, can also act as ordinary reinforcing bar, and exert its anti crack effect, pack anticorrosive material to the protector in, and wrap up prestressing tendons, in order to realize the anticorrosive mesh of prestressing tendons, promote prestressing tendons durability and then the crack resistance of concrete.

Description

Prestressed concrete beam

Technical Field

The utility model relates to a prestressed structure technical field especially relates to a prestressed concrete roof beam.

Background

In the long-term use process, transverse and oblique cracks gradually appear at the end part of the prestressed concrete hollow slab beam and the lower surface of the beam bottom, and the cracks are just positioned in the prestressed effective area and the failure area transition section of the prestressed rib. After the concrete protective layer in the cracking area is stripped, the corrosion of part of the prestressed tendons and the concrete spalling are discovered, and the corrosion of the prestressed tendons to the fracture is discovered more seriously. The reason is that the prestress failure measures of the prestress rib adopting the method of sleeving a PVC pipe on the prestress failure section at the end part of the beam have the following defects:

(1) after the prestressed tendons are tensioned, when the prestressed tendons are tensioned, stress concentration exists in the prestressed tendons in the bottom plate at the transition sections of the end prestressed effective area and the failure area, and the prestressed tendons in the prestressed failure area are isolated from the concrete by the outer sleeve PVC pipe, so that the concrete reinforcement ratio in the prestressed failure area is insufficient, and the concrete is pulled to crack;

(2) the waterproof measure of the PVC pipe sleeved outside the prestressed tendon at the prestressed failure section has defects, so that accumulated water on the bridge deck enters the PVC pipe, the prestressed tendon in the PVC pipe is corroded by the accumulated water for a long time, and finally the prestressed tendon is corroded and broken, and the concrete protective layer is cracked and damaged;

(3) the prestressed concrete hollow slab beam has two types of prestressed tendons penetrating through the end prestressed failure area, one type is artificially forced prestressed failure prestressed tendons, the other type is prestressed tendons which must keep effective prestress, after the prestressed tendons are corroded and broken due to the defects of PVC pipes and the concrete protective layer is cracked, the concrete which must keep the surface of the prestressed tendons with effective prestress is damaged and forced to crack and peel, the effectiveness of the prestress is hard to guarantee, meanwhile, the concrete in the area has cracks in large area, the durability of the prestressed tendons is reduced, finally, the two types of prestressed tendons tend to be corroded and broken, the bearing capacity of the beam body fails, and the safety of the structure is threatened.

For prestressed concrete hollow slab beams with such defects, dismantling and reconstruction are required. The method is not only a waste of resources, but also needs to interrupt traffic, and has high cost and long construction period. Particularly, if the bridge spans special structures such as railways and military facilities, the bridge is more difficult to dismantle and rebuild, higher in cost and longer in construction period.

Therefore, for newly-built prestressed concrete hollow slab bridges, reasonable and effective measures must be taken to improve the durability of prestressed tendons and the crack resistance of concrete at a prestressed failure section, and the urgent problem to be solved at present is formed.

SUMMERY OF THE UTILITY MODEL

Based on the above problem, an object of the utility model is to provide a prestressed concrete roof beam can improve the durability of prestressing force inefficacy section prestressing tendons, the anti crack performance of concrete.

In order to achieve the purpose, the utility model adopts the following technical proposal:

a prestressed concrete girder comprising:

the prestressed tendon comprises a prestressed failure section and a prestressed effective section;

the protective device comprises a closed section and an open section, the closed section is sleeved on the prestress failure section, and the open section is sleeved on the prestress effective section;

and the anticorrosive material is filled in the closed section.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, the both ends of the section of remaining silent are provided with spacing end cap.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, the cross-section of closed section includes ring shape, oval ring shape, square or polygon.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, the cross-section of opening section includes ring shape, oval ring shape, square or polygon.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, the length of closed section with the design length of prestressing force inefficacy section is the same.

As the preferred scheme of the prestressed concrete beam of the utility model, the length of the opening section is 50cm-100 cm.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, the breach of opening section is vertical upwards to be set up.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, anticorrosive material includes cement base grouting material, grout or polyurethane foam.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, protector is formed by the multistage concatenation.

As the utility model discloses a preferred scheme of prestressed concrete roof beam, protector is formed by steel or aluminum alloy preparation.

The utility model has the advantages that:

the utility model provides a prestressed concrete beam, through wrap up the prestressing force inefficacy section in the section of remaining silent section completely, in the follow-up concreting process, the section of remaining silent section keeps apart prestressing force inefficacy section and concrete to realize the function that the prestressing force became invalid, the section of remaining silent section can also act as ordinary reinforcing bar simultaneously, and play its anti crack effect; the opening section is sleeved on the prestress effective section, the opening section is open, the wrapping effect of the concrete poured subsequently on the prestress effective section is not influenced, the opening section and the closed section are connected into a whole, the prestress failure section and the prestress effective section are spanned, and the crack resistance of a concrete stress mutation section is enhanced; and completely wrapping the prestressed failure section in the anticorrosive material to fulfill the aim of corrosion prevention of the prestressed tendon. The utility model provides a prestressed concrete roof beam, need not to change existing prestressing force hollow slab girder structure size, do not change the hollow slab girder appearance, do not change the clearance under the bridge, do not change bridge structures atress system, do not change, do not disturb existing prestressing force hollow slab girder construction process and flow, thoroughly solve hollow slab girder prestressing force inefficacy section and effective segment junctional zone concrete reinforcement rate not enough, the problem of anti-crack inefficacy, thoroughly solve hollow slab girder prestressing force inefficacy section prestressing force muscle corrosion cracked durability problem, thoroughly improved prestressing force hollow slab girder durability and life effectively, very big economic benefits has.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments of the present invention will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the contents of the embodiments of the present invention and the drawings without creative efforts.

Fig. 1 is a flowchart illustrating a method for prefabricating a prestressed concrete girder according to an embodiment of the present invention;

fig. 2 is a schematic view of the prestressed tendons arranged on the hollow slab beam according to the embodiment of the present invention;

fig. 3 is a schematic structural view of a tendon according to an embodiment of the present invention;

fig. 4 is a schematic structural view of a tendon and a protector according to an embodiment of the present invention;

fig. 5 is a schematic structural view of a prestressed tendon, a protective device and a limiting plug according to an embodiment of the present invention;

fig. 6 is a schematic structural view of a prestressed concrete girder according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a protection device and a limiting plug according to an embodiment of the present invention;

fig. 8 is a schematic cross-sectional view of a closed cross-section according to an embodiment of the present invention;

fig. 9 is a schematic cross-sectional view of an open cross-sectional section according to an embodiment of the present invention;

FIG. 10 is a schematic view of a guard and fastener according to an embodiment of the present invention;

FIG. 11 is a schematic cross-sectional view of a guard and fastener provided in accordance with an embodiment of the present invention;

fig. 12 is a first structural schematic diagram of a protective device according to an embodiment of the present invention;

fig. 13 is a second structural schematic diagram of a protection device according to an embodiment of the present invention;

fig. 14 is a schematic view of a third structure of the protection device according to the embodiment of the present invention;

FIG. 15 is a schematic cross-sectional view of a closed cross-sectional section of a shield apparatus according to an embodiment of the present invention;

FIG. 16 is a schematic cross-sectional view of a section of an opening in a shield apparatus according to an embodiment of the present invention;

fig. 17 is a fourth structural schematic diagram of a protection device according to an embodiment of the present invention;

fig. 18 is a fifth structural schematic diagram of the protection device according to the embodiment of the present invention.

In the figure:

1-prestressed tendons; 2-a guard device; 3-anticorrosive material; 4-limiting plugs; 5-concrete; 6-a fastener;

11-a prestressed failure section; 12-a pre-stressed active section;

21-a closed section; 22-open cross-sectional section.

Detailed Description

In order to make the technical problems, technical solutions and technical effects achieved by the present invention more clear, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings, and obviously, the described embodiments are only some embodiments, not all embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Wherein the terms "first position" and "second position" are two different positions.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection or a removable connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The embodiment provides a method for prefabricating a prestressed concrete beam, which can be used for prefabricating a prestressed concrete hollow slab beam. As shown in fig. 1, the method for prefabricating a prestressed concrete beam includes:

s1, mounting a protection device 2 on the prestressed tendon 1 needing forced prestressing failure, wherein the protection device 2 is used for isolating the prestressing failure section 11 of the prestressed tendon 1 from the concrete 5;

s2, releasing the tension force of the prestressed tendon 1;

s3, filling an anticorrosive material 3 into the protection device 2, and wrapping the prestressed tendon 1;

and S4, plugging the end part of the cut prestressed tendon 1.

As shown in fig. 2-6, firstly, a protector 2 is installed on a prestressed tendon 1 which needs to be forced to fail by prestress, and the protector 2 isolates a prestressed failure section 11 of the prestressed tendon 1 from concrete 5 so as to realize the function of prestressed failure and also can serve as a common steel bar and play a role of cracking resistance; secondly, releasing the tension force of the prestressed tendon 1, and after the prestressed tendon 1 is completely released, keeping the prestressed failure section 11 of the prestressed tendon 1 in an unstressed state and completely not participating in structural stress; then, filling an anticorrosive material 3 into the protective device 2, and wrapping the prestressed tendon 1 to realize the purpose of corrosion prevention of the prestressed tendon 1; and finally, plugging the end part of the cut prestressed tendon 1 to improve the durability of the prestressed tendon 1 and the crack resistance of the concrete 5.

Optionally, before step S1, the method further includes: and (3) lofting and blanking the prestressed tendon 1, and determining the length and the position of the prestressed failure section 11 of the prestressed tendon 1. Firstly, lofting and blanking of the prestressed reinforcement 1 are carried out according to a construction drawing of the prestressed concrete hollow slab beam, and the length and the position of a prestressed failure section 11 of the prestressed reinforcement 1 are determined according to data in the construction drawing. Fig. 2 is a cross-sectional view of a typical hollow slab beam, and the tendons 1 may be numbered N1, N2, and N3 from top to bottom. Fig. 3 is a plan view of the tendon 1, in which the broken line indicates the prestressed failure section 11 of the tendon 1 at the end of the hollow plate girder and the solid line indicates the prestressed effective section 12 of the tendon 1. The N2 full length tendons 1 are all prestressed active sections 12 (solid line parts). Each of the N1 and N3 tendons 1 is divided into a prestressed failure section 11 (dotted line section) and a prestressed active section 12 (solid line section). The N1 and N3 tendons 1 are divided into a prestressed failure section 11 and a prestressed effective section 12, but each tendon 1 is a full-length and complete tendon. The design parameters of the prestressed failure section 11 and the prestressed effective section 12 of the N1 and N3 prestressed tendons 1 are determined by specific construction drawings, and the embodiment is only used as an example.

Optionally, after step S1 and before step S2, the method further includes: and finishing the pouring and maintenance of the concrete 5, and enabling the strength index to meet the design requirement. After the concrete 5 is poured and the maintenance is finished, and the strength index meets the design requirement, the tensile force of the prestressed tendon 1 is released.

Alternatively, as shown in fig. 4 to 6, the protection device 2 includes a closed section 21 and an open section 22, the closed section 21 is sleeved on the prestress failure section 11 of the tendon 1, and the open section 22 is sleeved on the prestress effective section 12 of the tendon 1. The closed section 21 is sleeved on the prestress failure section 11 of the prestress rib 1, the length of the closed section 21 is completely consistent with the design length of the prestress failure section 11, the prestress failure section 11 is completely wrapped inside the protective device 2, and in the subsequent concrete casting process of the concrete 5, the closed section 21 isolates the prestress failure section 11 from the concrete 5 so as to achieve the function of prestress failure, and meanwhile, the closed section 21 can also serve as a common reinforcing steel bar and play a role in cracking resistance. The opening section 22 is sleeved on the prestress effective section 12 of the prestress rib 1, the length of the opening section is 50-100 cm, the opening section is open, the bond wrapping effect of the concrete 5 poured subsequently on the prestress effective section 12 is not influenced, the opening section and the closed section 21 are connected into a whole, the opening section spans the prestress failure section 11 and the prestress effective section 12, and the crack resistance of the stress mutation section of the concrete 5 is enhanced.

Optionally, the anti-corrosion material 3 is filled in the closed section 21, and the anti-corrosion material 3 includes cement-based grouting material, cement paste or polyurethane foam material. After the common steel bars are bound and the prestressed tendons 1 are tensioned in place, the protection devices 2 are completely fixed on the surfaces of the prestressed tendons 1 according to the position parameters of the construction drawing. Meanwhile, the limiting plugs 4 are arranged at two ends of the closed section 21, the closed section 21 and the limiting plugs 4 form a closed cavity, it is ensured that the subsequently poured concrete 5 cannot enter the cavity, and the prestress failure section 11 is isolated from the concrete 5, so that the function of prestress failure is realized. Meanwhile, the prestressed tendon 1 can be limited and fixed in the center of the cavity, so that after the anticorrosive material 3 is injected into the cavity in the follow-up process, the outer surface of the prestressed tendon 1 can be uniformly wrapped in the cavity, and the anticorrosive performance of the prestressed tendon 1 is enhanced.

And after the concrete 5 of the hollow slab beam is poured and cured, and the strength index meets the design requirement, carrying out the releasing construction of the prestressed tendon 1. After the prestressed tendon 1 is completely tensioned, filling a micro-expansion anticorrosive material 3 (the anticorrosive material 3 can include but is not limited to cement-based grouting material, cement paste, polyurethane foam material and the like) into a cavity formed by the protective device 2 and the prestressed failure section 11, and completely wrapping the prestressed failure section 11 in the anticorrosive material 3 to fulfill the aim of corrosion prevention of the prestressed tendon 1. And finally, the end part of the cut prestressed tendon 1 is closed, so that the durability of the prestressed tendon 1 is thoroughly improved.

The method for prefabricating the prestressed concrete beam provided by the embodiment does not need to change the structural size of the existing prestressed hollow slab beam, does not change the appearance of the hollow slab beam, does not change the clearance below the bridge, does not change the stress system of the bridge structure, and does not change or interfere with the existing construction process and flow of the prestressed hollow slab beam, thereby thoroughly solving the problems of insufficient reinforcement ratio and crack resistance failure of the concrete 5 in the boundary area of the prestressed failure section 11 and the effective section of the hollow slab beam, thoroughly solving the problem of durability of corrosion and fracture of the prestressed ribs 1 of the prestressed failure section 11 of the hollow slab beam, thoroughly and effectively improving the durability and service life of the prestressed hollow slab beam, and having great economic benefit.

The embodiment also provides a prestressed concrete beam, which is prepared by adopting the method for prefabricating the prestressed concrete beam, as shown in fig. 2-6, and comprises a prestressed tendon 1, a protective device 2 and an anticorrosive material 3.

Specifically, the prestressed tendon 1 comprises a prestressed failure section 11 and a prestressed effective section 12; the protection device 2 comprises a closed section 21 and an open section 22, the closed section 21 is sleeved on the prestress failure section 11, and the open section 22 is sleeved on the prestress effective section 12; the anticorrosive material 3 is filled in the closed section 21.

The prestress failure section 11 is completely wrapped in the closed cross section 21, in the subsequent concrete 5 pouring process, the closed cross section 21 isolates the prestress failure section 11 from the concrete 5, so that the prestress failure function is realized, and meanwhile, the closed cross section 21 can also serve as a common steel bar and play a role in cracking resistance; the opening section 22 is sleeved on the prestress effective section 12, the part is open, the gripping action of the concrete 5 poured subsequently on the prestress effective section 12 is not influenced, and the opening section 22 and the closed section 21 are connected into a whole to span the prestress failure section 11 and the prestress effective section 12, so that the crack resistance of the stress mutation section of the concrete 5 is enhanced; and completely wrapping the prestress failure section 11 in the anticorrosive material 3 to realize the purpose of corrosion prevention of the prestressed tendon 1.

Optionally, two ends of the closed section 21 are provided with limiting plugs 4. The limiting plugs 4 are arranged at two ends of the closed section 21, the closed section 21 and the limiting plugs 4 form a closed cavity, it is ensured that the concrete 5 poured subsequently cannot enter the cavity, and the prestress failure section 11 is isolated from the concrete 5, so that the function of prestress failure is realized. Meanwhile, the prestressed tendon 1 can be limited and fixed in the center of the cavity, so that after the anticorrosive material 3 is injected into the cavity in the follow-up process, the outer surface of the prestressed tendon 1 can be uniformly wrapped in the cavity, and the anticorrosive performance of the prestressed tendon 1 is enhanced.

Optionally, the cross-section of the closed cross-section 21 comprises a circular ring, an elliptical ring, a square or a polygon. Of course, the cross-section of the open cross-section 22 includes a circular, elliptical, square or polygonal shape. Optionally, the length of the closed section 21 is the same as the designed length of the prestressed failure section 11, and the length of the open section 22 is 50cm-100 cm. Alternatively, the gap of the open section 22 is arranged vertically upwards. During installation, the gap of the opening section 22 is vertically arranged upwards, namely the opening section 22 must be arranged right below the prestressed tendon 1 and serves as a common reinforcing steel bar.

As shown in fig. 7-18, in the present embodiment, the material of the protection device 2 may be steel, and the outer surface thereof may be specially configured (including but not limited to, indentations, threads, shear keys, etc.) to enhance the adhesion between the protection device 2 and the concrete 5. Of course, in other embodiments, the material of the protection device 2 may also be an aluminum alloy, and the like, which is not limited herein.

For the convenience of construction, the protection device 2 can be cut into an upper part and a lower part along the axial direction in fig. 10, when in construction and installation, the upper part and the lower part are buckled outside the prestressed tendon 1 in an opposite way, and then the upper part and the lower part are connected into a whole through a fastener 6 (a screw). The connection of the upper part and the lower part includes but is not limited to a screw connection mode, and in addition, other connection modes such as a tongue-and-groove mode, a snap ring mode and the like can also be adopted.

For convenient construction, can be with protector 2 along the horizontal standard section of cutting into in figure 12, set up internal thread and external screw thread at standard section one end tail, connect standard section for the whole of full length through the screw socket during construction installation. The standard longitudinal connection of the segments includes but is not limited to a screw connection, and other connection methods such as tongue-and-groove connection and the like can be adopted. Of course, for ease of construction, the axial and transverse cuts may be combined as shown in FIG. 13.

As shown in fig. 14 to 18, the present embodiment further provides a shielding device 2 in another structural form, which is different from the shielding device 2 in the first structural form described above in that another structural implementation manner of the open section 22 is that the notches of the open section 22 are arranged on both sides of the shielding device 2, and the structure of the closed section 21 is identical. During installation, the notches of the opening section sections 22 are arranged towards the two transverse sides of the prestressed tendon 1, namely, the semicircular parts are required to be arranged right above and right below the prestressed tendon 1 to serve as the function of common reinforcing steel bars.

In the prestressed concrete beam provided by the embodiment, the prestressed failure section 11 is completely wrapped in the closed cross section 21, and in the subsequent concrete 5 pouring process, the closed cross section 21 isolates the prestressed failure section 11 from the concrete 5, so that the prestressed failure function is realized, and meanwhile, the closed cross section 21 can also serve as a common steel bar and play a role in cracking resistance; the opening section 22 is sleeved on the prestress effective section 12, the part is open, the gripping action of the concrete 5 poured subsequently on the prestress effective section 12 is not influenced, and the opening section 22 and the closed section 21 are connected into a whole to span the prestress failure section 11 and the prestress effective section 12, so that the crack resistance of the stress mutation section of the concrete 5 is enhanced; and completely wrapping the prestress failure section 11 in the anticorrosive material 3 to realize the purpose of corrosion prevention of the prestressed tendon 1.

The prestressed concrete beam provided by the embodiment does not need to change the structural size of the existing prestressed hollow slab beam, does not change the appearance of the hollow slab beam, does not change the clearance below the bridge, does not change the stress system of the bridge structure, and does not change or interfere with the existing construction process and flow of the prestressed hollow slab beam, thereby thoroughly solving the problems of insufficient reinforcement ratio and crack resistance failure of the concrete 5 in the boundary area of the prestressed failure section 11 and the effective section of the hollow slab beam, thoroughly solving the durability problem of corrosion and fracture of the prestressed ribs 1 in the prestressed failure section 11 of the hollow slab beam, thoroughly and effectively improving the durability and service life of the prestressed hollow slab beam, and having great economic benefit.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments illustrated herein, but is capable of various obvious modifications, rearrangements and substitutions without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims

1. A prestressed concrete girder, comprising:

the prestressed tendon (1) comprises a prestressed failure section (11) and a prestressed effective section (12);

the protection device (2) comprises a closed section (21) and an open section (22), the closed section (21) is sleeved on the prestress failure section (11), and the open section (22) is sleeved on the prestress effective section (12);

and the anticorrosive material (3) is filled in the closed section (21).

2. Prestressed concrete beam according to claim 1, characterized in that both ends of said closed section (21) are provided with a limiting plug (4).

3. Prestressed concrete beam according to claim 1, characterized in that the cross-section of said closed section (21) comprises a circular, elliptical, circular, square or polygonal shape.

4. Prestressed concrete beam according to claim 1, characterized in that the cross-section of said open section (22) comprises a circular, elliptical or polygonal shape.

5. Prestressed concrete beam according to claim 1, characterized in that the length of the closed section (21) is the same as the designed length of the prestressed failure section (11).

6. The prestressed concrete beam according to claim 1, wherein the length of the open section (22) is 50cm to 100 cm.

7. Prestressed concrete beam according to claim 1, characterized in that the gap of the open section (22) is arranged vertically upwards or the gap of the open section (22) is arranged on both sides of the shielding means (2).

8. Prestressed concrete beam according to claim 1, characterized in that said anti-corrosive material (3) comprises a cement-based grouting material, a cement paste or a polyurethane foam.

9. Prestressed concrete beam according to claim 1, characterized in that said protection means (2) are made of several segments spliced together.

10. Prestressed concrete beam according to any one of claims 1 to 9, characterized in that said shielding means (2) are made of steel or aluminium alloy.