A prestressed concrete beam and a prefabrication method thereof

Abstract

The present invention relates to the technical field of prestressed structures, and discloses a prestressed concrete beam and a prefabrication method thereof. The prestressed concrete beam includes prestressed tendons, a protection device, and an anti-corrosion material. The prestressed tendons include a prestress failure section and a prestress effective section; the protection device includes a protection sleeve and spiral stirrups. The protection sleeve is sleeved on the prestress failure section, and the spiral stirrups are sleeved on the protection sleeve and a part of the prestress effective section; the anti-corrosion material is filled in the protection sleeve. The prestressed concrete beam prefabrication method is used to prepare the above-mentioned prestressed concrete beam. By separating the prestress failure section from the concrete through the protection sleeve, the function of prestress failure is realized. At the same time, the protection sleeve can also act as ordinary reinforcement and play its crack resistance role. By sleeving the spiral stirrups on the prestress effective section, spanning the prestress failure section and the prestress effective section, the crack resistance performance of the concrete stress mutation interval is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of prestressed structures, and particularly to a prestressed concrete beam and a prefabrication method thereof. Background Art

[0002] During the long-term use process, transverse and diagonal cracks gradually appear on the end part and the lower surface of the beam of the prestressed concrete hollow slab beam, and these cracks just lie in the transition section between the effective prestress area and the failure area of the prestressed tendons. After peeling off the concrete protective layer in this cracking area, it is found that some prestressed tendons are corroded, the concrete bulges and cracks, and more seriously, the prestressed tendons are corroded until they break. The reasons are as follows: the prestress failure measures such as using PVC pipes outside the prestressed tendons in the prestress failure section at the beam end have the following defects:

[0003] (1) When the prestressed tendons are tensioned and then released, there is stress concentration in the transition section between the effective prestress area and the failure area at the end of the prestressed tendons in the bottom slab. Since the prestressed tendons in the prestress failure section are isolated from the concrete by using PVC pipes outside, the reinforcement ratio of the concrete in the prestress failure area is insufficient, and the concrete is pulled and cracked;

[0004] (2) The waterproof measures of the PVC pipes outside the prestressed tendons in the prestress failure section are defective, resulting in the bridge surface water entering the inside of the PVC pipes. The prestressed tendons in the PVC pipes are eroded by the accumulated water for a long time, and finally the prestressed tendons are corroded and broken, and the concrete protective layer bulges and is damaged;

[0005] (3) There are two types of prestressed tendons passing through the prestress failure area at the end of the prestressed concrete hollow slab beam. One type is the prestressed tendons with artificially forced prestress failure, and the other type is the prestressed tendons that must maintain effective prestress. After the prestressed tendons with artificially forced prestress failure are corroded and broken and the concrete protective layer bulges and is damaged due to the defects of the PVC pipes, the concrete wrapped on the surface of the other type of prestressed tendons that must maintain effective prestress in this area is damaged and bulges and peels off by force, and the effectiveness of its prestress is difficult to guarantee. At the same time, large-area cracks appear in the concrete in this area, the durability of the prestressed tendons decreases, and finally both types of prestressed tendons tend to be corroded and broken, and the bearing capacity of the beam body fails, endangering the structural safety.

[0006] For the prestressed concrete hollow slab beams with such defects, it is necessary to demolish and reconstruct them. This is not only a waste of resources, but also requires traffic interruption, with high costs and long construction periods. Especially when such bridges cross special structures, such as railways, military facilities, etc., the difficulty of demolition and reconstruction is greater, the cost is higher, and the construction period is longer.

[0007] Therefore, for newly built prestressed concrete hollow slab bridges, reasonable and effective measures must be taken to improve the durability of the prestressed tendons in the prestress failure section and the crack resistance of the concrete, which has become an urgent problem to be solved at present. Summary of the Invention

[0008] Based on the above problems, the object of the present invention is to provide a prestressed concrete beam and a prefabrication method, which can improve the durability of the prestressed tendons in the prestress failure section and the crack resistance of the concrete.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A prestressed concrete beam, comprising:

[0011] Prestressed tendons, including a prestress failure section and a prestress effective section;

[0012] A protection device, including a protection sleeve and spiral stirrups. The protection sleeve is sleeved on the prestress failure section, and the spiral stirrups are sleeved on the protection sleeve and a part of the prestress effective section;

[0013] An anticorrosive material is filled in the protection sleeve.

[0014] As a preferred solution of the prestressed concrete beam of the present invention, limiting plugs are provided at both ends of the protection sleeve. The limiting plugs and the protection sleeve form a closed chamber for isolating the prestress failure section from the concrete.

[0015] As a preferred solution of the prestressed concrete beam of the present invention, the limiting plugs are detachably connected to the protection sleeve.

[0016] As a preferred solution of the prestressed concrete beam of the present invention, the cross section of the protection sleeve includes an annular shape, an elliptical annular shape or a polygonal shape.

[0017] As a preferred solution of the prestressed concrete beam of the present invention, the length of the protection sleeve is the same as the designed length of the prestress failure section.

[0018] As a preferred solution of the prestressed concrete beam of the present invention, the length of the spiral stirrups sleeved on the prestress effective section is 50 cm - 100 cm.

[0019] As a preferred solution of the prestressed concrete beam of the present invention, the anticorrosive material includes cement-based grouting material, cement slurry or polyurethane foam material.

[0020] A prefabrication method for a prestressed concrete beam, used to prepare the prestressed concrete beam as described above, comprising the following steps:

[0021] S1. Install a protection device on the prestressed tendons that need to be forced to have prestress failure. The protection sleeve of the protection device is used to isolate the prestress failure section of the prestressed tendons from the concrete;

[0022] S2. Release the tensile force of the prestressed tendon;

[0023] S3. Fill the anticorrosive material into the protective sleeve and wrap the prestress failure section;

[0024] S4. Seal the ends of the truncated prestress failure section.

[0025] As a preferred solution of the prefabrication method of the prestressed concrete beam of the present invention, before step S1, the following steps are further included: laying out and cutting the prestressed tendon, and determining the length and position of the prestress failure section.

[0026] As a preferred solution of the prefabrication method of the prestressed concrete beam of the present invention, after step S1 and before step S2, the following steps are further included: completing the pouring and curing of the concrete, and making the strength index of the concrete meet the design requirements.

[0027] The beneficial effects of the present invention are as follows:

[0028] For the prestressed concrete beam provided by the present invention, by completely wrapping the prestress failure section in the protective sleeve, during the subsequent concrete pouring process, the protective sleeve isolates the prestress failure section from the concrete to achieve the function of prestress failure. At the same time, the protective sleeve can also act as ordinary steel bars and play its crack resistance role; by sleeving the spiral stirrups on the prestressed effective section, this part is open, which does not affect the grip of the subsequent poured concrete on the prestressed effective section, and is connected to the protective sleeve as a whole, spanning the prestress failure section and the prestressed effective section, enhancing the crack resistance performance of the concrete stress mutation interval; completely wrapping the prestress failure section inside the anticorrosive material to achieve the purpose of preventing corrosion of the prestressed tendon. The prestressed concrete beam provided by the present invention does not need to change the structural dimensions of the current prestressed hollow slab beam, does not change the shape of the hollow slab beam, does not change the clearance under the bridge, does not change the bridge structure force system, does not change and does not interfere with the current construction process and flow of the prestressed hollow slab beam, and completely solves the problems of insufficient concrete reinforcement ratio and crack resistance failure in the junction area between the prestress failure section and the effective section of the hollow slab beam, completely solves the durability problem of corrosion and fracture of the prestressed tendon in the prestress failure section of the hollow slab beam, and effectively improves the durability performance and service life of the prestressed hollow slab beam, having great economic benefits.

[0029] The prefabrication method of prestressed concrete beams provided by the present invention can be used for prefabricating prestressed concrete hollow slab beams. First, a protection device is installed on the prestressed tendons that need to be forced to lose prestress. The protection sleeve of the protection device isolates the prestress loss section of the prestressed tendons from the concrete to achieve the function of prestress loss, and can also act as ordinary steel bars and play its crack resistance role. Secondly, the tension of the prestressed tendons is released. After the prestressed tendons are relaxed, the prestress loss section of the prestressed tendons is in a stress-free state and does not participate in the structural force completely. Then, an anti-corrosion material is filled into the protection sleeve to wrap the prestress loss section to achieve the purpose of anti-corrosion of the prestress loss section. Finally, the ends of the truncated prestress loss section are sealed to improve the durability of the prestressed tendons and the crack resistance of the concrete. The prefabrication method of prestressed concrete beams provided by the present invention does not need to change the structural dimensions of the existing prestressed hollow slab beams, does not change the shape of the hollow slab beams, does not change the clearance under the bridge, does not change the bridge structural force system, does not change or interfere with the existing construction technology and process of prestressed hollow slab beams, and completely solves the problems of insufficient concrete reinforcement ratio and crack resistance failure in the junction area between the prestress loss section and the effective section of the hollow slab beams, and completely solves the durability problem of corrosion and fracture of the prestressed tendons in the prestress loss section of the hollow slab beams, and effectively improves the durability and service life of the prestressed hollow slab beams, having great economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0031] Figure 1 It is a schematic diagram of the arrangement of prestressed tendons on a hollow slab beam provided by the specific embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of the prestressed tendons provided by the specific embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of the structure of the prestressed tendons and the protection device provided by the specific embodiment of the present invention;

[0034] Figure 4 It is a schematic diagram of the structure of the prestressed tendons, the protection device and the limit plug provided by the specific embodiment of the present invention;

[0035] Figure 5 It is a schematic diagram of the structure of the prestressed concrete beam provided by the specific embodiment of the present invention;

[0036] Figure 6It is a flowchart of the precast method of the prestressed concrete beam provided by the specific embodiment of the present invention.

[0037] In the figure:

[0038] 1 - Prestressing tendon; 2 - Protection device; 3 - Anticorrosion material; 4 - Limit plug; 5 - Concrete;

[0039] 11 - Prestress failure section; 12 - Prestress effective section;

[0040] 21 - Protection sleeve; 22 - Helical stirrup. Specific embodiment

[0041] To make the technical problems solved by the present invention, the technical solutions adopted and the achieved technical effects clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0043] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0044] This embodiment provides a prestressed concrete beam, as Figures 1 - 5 shown, the prestressed concrete beam includes a prestressing tendon 1, a protection device 2, and an anticorrosion material 3.

[0045] Specifically, the prestressed tendon 1 includes a prestress failure section 11 and a prestress effective section 12; the protection device 2 includes a protection sleeve 21 and spiral stirrups 22. The protection sleeve 21 is sleeved on the prestress failure section 11, and the spiral stirrups 22 are sleeved on the protection sleeve 21 and a part of the prestress effective section 12; the anti-corrosion material 3 is filled in the protection sleeve 21.

[0046] By completely wrapping the prestress failure section 11 in the protection sleeve 21, during the subsequent pouring of the concrete 5, the protection sleeve 21 isolates the prestress failure section 11 from the concrete 5 to achieve the function of prestress failure. At the same time, the protection sleeve 21 can also act as ordinary steel bars and play its crack resistance role; by sleeving the spiral stirrups 22 on the prestress effective section 12, this part is open and does not affect the grip of the subsequent poured concrete 5 on the prestress effective section 12, and is connected to the protection sleeve 21 as a whole, spanning the prestress failure section 11 and the prestress effective section 12, enhancing the crack resistance performance of the stress mutation section of the concrete 5; completely wrapping the prestress failure section 11 inside the anti-corrosion material 3 to achieve the anti-corrosion purpose of the prestressed tendon 1.

[0047] Optionally, limit plugs 4 are provided at both ends of the protection sleeve 21. The limit plugs 4 and the protection sleeve 21 form a closed chamber for isolating the prestress failure section 11 from the concrete 5. The limit plugs 4 and the protection sleeve 21 form a closed chamber to ensure that the subsequent poured concrete 5 does not enter this closed chamber, so as to isolate the prestress failure section 11 from the concrete 5 and achieve the function of prestress failure. At the same time, the prestress failure section 11 can also be restricted and fixed in the center of the closed chamber. In this way, after the anti-corrosion material 3 is injected into the closed chamber subsequently, the outer surface of the prestress failure section 11 can be evenly wrapped therein, strengthening the anti-corrosion performance of the prestress failure section 11.

[0048] For the convenience of later maintenance and repair, optionally, the limit plugs 4 and the protection sleeve 21 are detachably connected. To adapt to application scenarios with different requirements, optionally, the cross-section of the protection sleeve 21 includes a circular ring, an elliptical ring or a polygon. In this embodiment, the length of the protection sleeve 21 is the same as the designed length of the prestress failure section 11. The length of the spiral stirrups 22 sleeved on the prestress effective section 12 is 50 cm - 100 cm. The anti-corrosion material 3 includes cement-based grouting material, cement slurry or polyurethane foam material. The material of the protection sleeve 21 can be a metal material or a non-metal material. The material of the spiral stirrups 22 can be a metal material, and special structures (such as but not limited to notches, threads, shear keys, etc.) can be adopted on its outer surface to enhance the bonding performance between the spiral stirrups 22 and the concrete 5.

[0049] The prestressed concrete beam provided in this embodiment realizes the function of prestress failure by completely wrapping the prestress failure section 11 within the protective sleeve 21. During the subsequent pouring of concrete 5, the protective sleeve 21 isolates the prestress failure section 11 from the concrete 5. Meanwhile, the protective sleeve 21 can also act as ordinary reinforcement and play its anti-cracking role. The spiral stirrup 22 is sleeved on the prestress effective section 12. This part is open and does not affect the grip of the subsequently poured concrete 5 on the prestress effective section 12, and is connected to the protective sleeve 21 as a whole, spanning across the prestress failure section 11 and the prestress effective section 12 to enhance the anti-cracking performance of the stress mutation interval of the concrete 5. The prestress failure section 11 is completely wrapped within the anti-corrosion material 3 to achieve the purpose of anti-corrosion of the prestressing tendon 1.

[0050] The prestressed concrete beam provided in this embodiment does not require changing the structural dimensions of the existing prestressed hollow slab beam, does not change the external shape of the hollow slab beam, does not change the under-bridge clearance, does not change the bridge structure force system, and does not change or interfere with the existing construction technology and process of the prestressed hollow slab beam. It completely solves the problems of insufficient concrete reinforcement ratio and anti-cracking failure in the junction area between the prestress failure section and the effective section of the hollow slab beam, completely solves the durability problem of corrosion and fracture of the prestressing tendon 1 in the prestress failure section of the hollow slab beam, and effectively improves the durability and service life of the prestressed hollow slab beam, with great economic benefits.

[0051] This embodiment also provides a method for prefabricating a prestressed concrete beam for preparing the above-mentioned prestressed concrete beam. As Figure 6 shown, the method for prefabricating the prestressed concrete beam includes the following steps:

[0052] S1. Install a protection device 2 on the prestressing tendon 1 that requires forced prestress failure. The protective sleeve 21 of the protection device 2 is used to isolate the prestress failure section 11 of the prestressing tendon 1 from the concrete 5;

[0053] S2. Release the tensile force of the prestressing tendon 1;

[0054] S3. Fill the anti-corrosion material 3 into the protective sleeve 21 and wrap the prestress failure section 11;

[0055] S4. Seal the end of the truncated prestress failure section 11.

[0056] First, install a protection device 2 on the prestressed tendon 1 that requires forced prestress failure. The protective sleeve 21 of the protection device 2 isolates the prestress failure section 11 of the prestressed tendon 1 from the concrete 5 to achieve the function of prestress failure, and can also act as ordinary reinforcement and play its crack resistance role. Secondly, release the tensile force of the prestressed tendon 1. After the prestressed tendon 1 is relaxed, the prestress failure section 11 of the prestressed tendon 1 is in a stress-free state and does not participate in the structural force at all. Then, fill the anticorrosive material 3 into the protective sleeve 21 and wrap the prestress failure section 11 to achieve the purpose of anti-corrosion of the prestress failure section 11. Finally, seal the end of the truncated prestress failure section 11 to improve the durability of the prestressed tendon 1 and the crack resistance of the concrete 5.

[0057] Optionally, before step S1, the following steps are also included: lofting and cutting the prestressed tendon 1, and determining the length and position of the prestress failure section 11. First, loft and cut the prestressed tendon 1 according to the construction drawing of the prestressed concrete hollow slab beam, and determine the length and position of the prestress failure section 11 of the prestressed tendon 1 according to the data in the construction drawing. Figure 1 is a typical cross-sectional view of a hollow slab beam. Figure 2 is a top view of the prestressed tendon 1. The prestressed tendon 1 can be numbered as N1, N2, N3 from top to bottom. Figure 2 The dotted line in [Figure] represents the prestress failure section 11 of the prestressed tendon 1 located at the end of the hollow slab beam, and the solid line represents the prestress effective section 12 of the prestressed tendon 1. The entire length of the N2 prestressed tendon 1 is the prestress effective section 12 (solid line part). The N1 and N3 prestressed tendons 1 are each divided into a prestress failure section 11 (dotted line part) and a prestress effective section 12 (solid line part). Although the N1 and N3 prestressed tendons 1 are divided into a prestress failure section 11 and a prestress effective section 12, each is a continuous and complete prestressed tendon 1. The design parameters of the prestress failure section 11 and the prestress effective section 12 of the N1 and N3 prestressed tendons 1 are determined by the specific construction drawing, and only examples are given in this embodiment.

[0058] Optionally, after step S1 and before step S2, the following steps are also included: complete the pouring and curing of the concrete 5 and make the strength index of the concrete 5 meet the design requirements. After the concrete 5 is poured, cured, and the strength index meets the design requirements, then release the tensile force of the prestressed tendon 1.

[0059] The prefabrication method of prestressed concrete beams provided in this embodiment can be used for prefabricating prestressed concrete hollow slab beams. First, install a protection device 2 on the prestressed tendon 1 that needs to be forced to lose prestress. The protection sleeve 21 of the protection device 2 isolates the prestress loss section 11 of the prestressed tendon 1 from the concrete 5 to achieve the function of prestress loss, and can also act as ordinary steel bars and play its crack resistance role. Secondly, release the tensile force of the prestressed tendon 1. After the prestressed tendon 1 is relaxed, the prestress loss section 11 of the prestressed tendon 1 is in a stress-free state and does not participate in the structural force completely. Then, fill the anticorrosion material 3 into the protection sleeve 21 and wrap the prestress loss section 11 to achieve the purpose of anti-corrosion of the prestress loss section 11. Finally, seal the end of the truncated prestress loss section 11 to improve the durability of the prestressed tendon 1 and the crack resistance of the concrete 5.

[0060] The prefabrication method of prestressed concrete beams provided in this embodiment does not need to change the structural dimensions of the current prestressed hollow slab beam, does not change the shape of the hollow slab beam, does not change the clearance under the bridge, does not change the bridge structure force system, does not change or interfere with the current construction process and flow of the prestressed hollow slab beam, and completely solves the problems of insufficient concrete reinforcement ratio and crack resistance failure in the junction area between the prestress loss section and the effective section of the hollow slab beam, and completely solves the durability problem of the corrosion and fracture of the prestressed tendon 1 in the prestress loss section of the hollow slab beam, and effectively improves the durability and service life of the prestressed hollow slab beam, with great economic benefits.

[0061] Note that the above is only the preferred embodiment of the present invention and the applied technical principle. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A prestressed concrete beam, characterized in that, Comprising: A prestressed tendon (1), including a prestress failure section (11) and a prestress effective section (12); A protection device (2), including a protection sleeve (21) and spiral stirrups (22), the protection sleeve (21) is sleeved on the prestress failure section (11), and the spiral stirrups (22) are sleeved on the protection sleeve (21) and part of the prestress effective section (12); An anticorrosive material (3), filled in the protection sleeve (21); Both ends of the protection sleeve (21) are provided with limit plugs (4), and the limit plugs (4) and the protection sleeve (21) form a closed chamber for isolating the prestress failure section (11) from the concrete (5); The length of the protection sleeve (21) is the same as the designed length of the prestress failure section (11).

2. The prestressed concrete beam according to claim 1, wherein The limit plug (4) is detachably connected to the protection sleeve (21).

3. The prestressed concrete beam according to claim 1, characterized in that, The cross-section of the protection sleeve (21) includes a circular ring, an elliptical ring or a polygon.

4. The prestressed concrete beam according to claim 1, wherein The length of the spiral stirrups (22) sleeved on the prestress effective section (12) is 50 cm - 100 cm.

5. The prestressed concrete beam according to claim 1, characterized in that, The anticorrosive material (3) includes cement-based grouting material, cement slurry or polyurethane foam material.

6. A precast method for prestressed concrete beams, characterized in that, For preparing a prestressed concrete beam as described in any one of claims 1 - 5, comprising the following steps: S1. Install a protection device (2) on the prestressed tendon (1) that needs to be forced to have prestress failure, and the protection sleeve (21) of the protection device (2) is used to isolate the prestress failure section (11) of the prestressed tendon (1) from the concrete (5); S2. Release the tensile force of the prestressed tendon (1); S3. Fill the anticorrosive material (3) into the protection sleeve (21) and wrap the prestress failure section (11); S4. Seal the ends of the truncated prestress failure section (11).

7. The prefabrication method of the prestressed concrete beam according to claim 6, characterized in that, Before step S1, the following steps are further included: laying out and cutting the prestressed tendon (1), and determining the length and position of the prestress failure section (11).

8. The prefabrication method of the prestressed concrete beam according to claim 6, characterized in that, After step S1 and before step S2, the following steps are further included: completing the pouring and curing of the concrete (5), and making the strength index of the concrete (5) meet the design requirements.

Images