Successive mixed tensioning method hollow plate beam construction method and hollow plate beam

Abstract

The invention provides a successive mixed-tensioning method hollow plate girder construction method and a hollow plate girder, and the method comprises the following steps: S1, manufacturing a precast beam by adopting a pre-tensioning method, and reserving a post-tensioning steel beam perforated pipe; s2, hollow slab beams are laid, and hinge joints are reserved; s3, a concrete layer is poured; s4, the post-tensioned steel beam is tensioned; s5, paving asphalt; the precast beam is prefabricated by adopting a pre-tensioning method, and the post-tensioning method steel beam is tensioned at the beam end, so that waste caused by man-made failure of the pre-tensioning method steel beam is reduced; when the hinge joint needs to be poured, the hinge joint serves as a structure and is combined with the precast beam into a whole after being poured, the integrity of the whole plate beam is better, the strength is higher, and the original hinge joint problem is also relieved.

Description

Technical Field

[0001] This invention relates to the field of bridge construction, and in particular to a method for constructing hollow slab beams using a sequential tensioning method and the hollow slab beam itself. Background Technology

[0002] In small and medium spans, hollow slab girders are still the most common structural form used in bridge design. The pre-tensioning method is a common bridge construction method for hollow slab girders with a span of 10-20 meters. Its advantages are significant, mainly reflected in: convenient factory prefabrication, lower requirements for hoisting capacity, fast construction speed, relatively low cost, and wide applicability.

[0003] The main drawback of pre-tensioned hollow slab beams lies in the hinge joints. While the hinge joints are crucial for the lateral connection of the hollow slab beams, accounting for approximately 20% of the total concrete volume, they are not considered part of the structure between adjacent pre-tensioned hollow slab beams and therefore play almost no role in the design of flexural and shear bearing capacity.

[0004] Because pre-tensioned steel strands are difficult to arrange in curves, the control section is generally at the mid-span. Therefore, prestressed active failure measures need to be adopted at the beam end sections, thus wasting some of the actual function of the steel strands.

[0005] In addition, pre-tensioned slab beams cannot have pre-camber, and under the action of prestressed steel strands, upward deflection is often unavoidable, thus limiting the span of the bridge.

[0006] Therefore, there is an urgent need for a new construction method for hollow slab beams to eliminate the drawbacks of the original construction method while retaining the advantages of the original pre-tensioned hollow slab beam method, thereby improving the overall performance of hollow slab beams. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for constructing hollow slab beams using a sequential tensioning method, and a hollow slab beam itself. The technical solution adopted by this invention is as follows: A construction method for hollow slab beams using sequential tensioning includes the following steps. S1. Fabrication of precast beams: This includes fabricating precast edge beams and precast middle beams; If the hollow slab beam does not require hinge joints, the post-tensioned steel strand perforation tubes are reserved in the mold of the middle beam and the side beam of the precast beam respectively. The hollow precast side beam and the middle beam of the precast beam are made by pre-tensioning method. After demolding, the post-tensioned steel strand perforations are formed in the web of the side beam and the web of the middle beam of the precast beam along the length direction respectively. If a hollow slab beam requires a hinge joint, a perforated tube for the post-tensioned steel strand is reserved in the precast side beam mold. The hollow precast side beam and the middle beam of the precast beam are made using the pre-tensioning method. After demolding, the perforated tube for the post-tensioned steel strand is formed along the length of the web of the precast side beam. S2. Laying hollow slab beams: Several precast beams are laid on the bottom formwork at intervals according to the layout of precast beams at both ends and several precast beams in the middle. Hinges are formed between the precast beams at both ends and between the precast beams in the middle. If the hollow slab beam does not require hinge joints, use a hinge joint mold to fill the space at the hinge joint and align the upper surface of the hinge joint mold with the upper surface of the precast beam. If a hinge joint is required for a hollow slab beam, a perforated tube for the post-tensioned steel strands should be reserved in the hinge joint along the length direction. S3. Pouring the concrete layer: Lay the inner steel mesh above the hollow slab beam, lift the bottom formwork, erect the beam, pour the concrete layer, and remove the bottom formwork and cure after the concrete layer reaches its strength. If the hollow slab beam does not require hinge joints, the hinge joint mold will be removed along with the bottom formwork. If a hollow slab beam requires a hinge joint, after the concrete layer is poured, post-tensioned steel strand perforations are formed in the hinge joint along the length direction. S4. Tensioning: Install post-tensioned steel strands through the holes and tension the post-tensioned steel strands. S5. Paving with asphalt: Pave an asphalt layer on the surface of the concrete layer and cure it.

[0008] Furthermore, In step S2, if the hollow slab beam requires a hinge joint, several steel cages are arranged at intervals along the length direction within the hinge joint, and several steel strands are laid within the hinge joint. Any of the steel strands within the hinge joint is laid along the length direction and the edges of the steel cages that intersect with its laying path are tied together. A perforated tube for the post-tensioned steel strand is reserved within the hinge joint, and the precast beam steel bars embedded in the precast beam are bent toward the inside of the hinge joint.

[0009] Furthermore, in step S2, the method of bending the precast beam reinforcement embedded in the precast beam toward the inside of the hinge joint is specifically as follows: Open the precast beam reinforcement bars laterally in the width direction of the precast beam outwards; The precast beam reinforcement bars above the precast beam are bent outwards into a horizontal shape, and the precast beam reinforcement bars above two connected precast beams overlap in the hinge joint.

[0010] A hollow slab beam is constructed using the sequential tensioning method for hollow slab beams.

[0011] Advantages of this invention: The precast beams are pre-tensioned, allowing them to be constructed in the prefabrication yard and then transported to the bridge construction site. This retains the advantages of the original pre-tensioned hollow slab beam manufacturing process while avoiding the disadvantages of the pre-tensioned steel strands being difficult to bend. The post-tensioned steel strands are tensioned at the beam ends, reducing waste caused by human error in the pre-tensioned steel strands. When it is necessary to pour a hinge joint, by pre-reserving the steel strands in the hinge joint and bending the steel strands in the precast beam, the hinge joint is used as a structure so that it can be integrated with the precast beam after pouring, resulting in better overall integrity and higher strength of the entire slab beam, and the original hinge joint problem is also alleviated. Since there is no pre-tensioning construction procedure at the construction site, the problem of camber caused by excessive steel strands in pre-tensioned slab beams is avoided. Attached Figure Description

[0012] Figure 1 This is an elevation view of the hollow slab beam of the present invention.

[0013] Figure 2 This is a cross-sectional view of a precast beam in one embodiment.

[0014] Figure 3 This is a cross-sectional view of a hollow slab beam in one embodiment.

[0015] Figure 4 This is a cross-sectional view of the precast beam in another embodiment.

[0016] Figure 5 This is a diagram showing the bending shape of the precast beam reinforcement in another implementation method.

[0017] Figure 6 This is a cross-sectional view of the hinge in another embodiment.

[0018] Figure 7 This is a cross-sectional view of a hollow slab beam in another embodiment.

[0019] In the diagram: 100-precast beam, 110-bottom slab, 120-web slab, 130-top slab, 140-bottom transverse embedded steel bars, 160-top transverse embedded steel bars, 170-side vertical embedded steel bars, 180-top embedded door bars, 200-pre-tensioned steel strands, 300-post-tensioned steel strand perforated tubes, 400-steel strands within hinge joints, 500-steel cage, 600-inner steel mesh. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] A construction method for hollow slab beams using a sequential tensioning method, characterized by comprising the following steps: S1. Fabrication of precast beam 100: This includes fabrication of precast beam edge beams and precast beam middle beams; If the hollow slab beam does not require hinge joints, 300mm perforated tubes for post-tensioned steel strands are reserved in the molds for the middle beam and the side beam of the precast beam, respectively. The hollow precast side beam and the middle beam of the precast beam are made by pre-tensioning. After demolding, post-tensioned steel strand perforations are formed along the length direction at the web of the side beam and the web of the middle beam of the precast beam, respectively. If a hollow slab beam requires a hinge joint, a 300mm perforated tube for post-tensioned steel strands is reserved in the precast side beam mold. The hollow precast side beam and the middle beam of the precast beam are made using the pre-tensioning method. After demolding, the perforated tube for post-tensioned steel strands is formed along the length of the web of the precast side beam. S2. Laying hollow slab beams: Several precast beams are laid on the bottom formwork at 100-degree intervals, with precast beams at both ends as edge beams and several precast beams in the middle. Hinge joints are formed between the edge beams and the middle beams, and between the middle beams. If the hollow slab beam does not require hinge joints, use a hinge joint mold to fill the space at the hinge joint and align the upper surface of the hinge joint mold with the upper surface of the precast beam 100. If a hinge joint is required for a hollow slab beam, a 300mm perforated tube for post-tensioned steel strands should be reserved in the hinge joint along the length direction. S3. Pouring concrete layer: Lay 600mm inner steel mesh on top of hollow slab beam, lift bottom formwork, erect beam, pour concrete layer, and remove bottom formwork and cure after concrete layer reaches strength. If the hollow slab beam does not require hinge joints, the hinge joint mold will be removed along with the bottom formwork. If a hollow slab beam requires a hinge joint, after the concrete layer is poured, post-tensioned steel strand perforations are formed in the hinge joint along the length direction. S4. Tensioning: Install post-tensioned steel strands through the holes and tension the post-tensioned steel strands. S5. Paving with asphalt: Pave an asphalt layer on the surface of the concrete layer and cure it.

[0022] Comparing the process of fabricating the hollow precast beam 100 using the pre-tensioning method in this application with the process of fabricating hollow slab beams using the pre-tensioning method in the prior art, the steps are basically the same except for reserving the perforated tube 300 for the post-tensioned steel strands. For example, referring to patent 202411078640.4, and in conjunction with the appendix to the specification... Figure 1 and attached Figure 2 The process of fabricating a hollow precast beam 100 using the pre-tensioning method can be briefly described as follows: pre-tensioned steel strands are tensioned on a platform; PE pipes are fitted onto a portion of the pre-tensioned steel strands to compensate for prestress failure, depending on structural requirements; ordinary steel bars are tied; the formwork is erected and concrete is poured; the formwork is removed after the concrete reaches its strength; the pre-tensioned steel strands are released to apply prestress to the concrete beam.

[0023] The cross-sectional shape of one type of precast beam 100 is shown in the attached figure. Figure 1As shown, the precast beam 100 includes a connected base plate 110, web plates 120 on both sides of the base plate 110, and a top plate 130 at the top of the web plates 120. Pre-tensioned steel strands 200 are spaced apart along the width direction at the base plate 110 of the precast beam 100. Post-tensioned steel strand perforated tubes 300 are located at the web plates 120 on both sides. Specifically, the number of pre-tensioned steel strands 200 is not required and can be arranged as needed according to the size and strength requirements of the precast beam 100. Generally, at least two post-tensioned steel strand perforated tubes 300 are spaced apart along the height direction at the web plates 120. The height difference between the center of the lowest post-tensioned steel strand perforated tube 300 and the center of the pre-tensioned steel strand 200 is calculated based on the size and weight of the precast beam 100, and there are no specific size restrictions.

[0024] The precast beams 100, produced using the pre-tensioning method, can be constructed at the prefabrication yard and then transported to the bridge construction site. This retains the advantages of the original tensioned hollow slab beam manufacturing process while simultaneously embedding the post-tensioned steel strand perforated pipes 300. Since the precast beams 100 are not poured on-site, they can be used as supports and most of the formwork during concrete pouring, reducing the number of supports and manual formwork required and lowering costs compared to on-site casting.

[0025] The concrete pouring and post-tensioning of the steel strands were both carried out on the bridge construction site. Since the pre-tensioning method cannot set the pre-camber of the slab beam, the process of prefabricating the 100mm precast beam first and then using the post-tensioning steel strands after the concrete layer is poured can avoid the problem of reverse camber caused by using only the pre-tensioning method and having too many steel strands.

[0026] Taking the dimensions of a 25-meter precast beam 100 in the prior art as an example, the following table compares the different indicators of the hollow slab beams in the prior art with those in this application:

[0027] Therefore, it can be seen that when 43 steel strands are tensioned at once (15 pre-tensioned and 28 post-tensioned), the camber value during the 60-day beam storage period reaches 63mm. Using the construction method of this invention, 15 pre-tensioned steel strands are tensioned during prefabrication, and the cast-in-place structure is poured after beam erection. The post-tensioned steel strands are then tensioned after the cast-in-place concrete structure reaches 80% strength, resulting in a camber value of only 30mm. Overall, the structure of this application is comparable to cast-in-place beams. 100mm of the prefabricated beam can serve as a support and formwork, facilitating construction. The use of mixed tensioning with some steel strands bending upwards increases shear strength by 32%.

[0028] It should be noted that the placement of the post-tensioned steel strand perforated tube 300 is related to whether a hinge joint needs to be cast. When a hinge joint is not required, the post-tensioned steel strand perforated tube 300 is pre-embedded in the edge beams and middle beams of the precast beam, respectively, and the cross-sectional shape of the formed hollow slab beam is shown in the attached figure. Figure 3As shown; when it is necessary to pour the hinge joint, the post-tensioned steel strand perforated pipe 300 is pre-embedded in the edge beam and hinge joint of the precast beam respectively, so that the hinge joint replaces part of the precast beam structure to realize the tensioning construction. The cross-sectional shape of the formed hollow slab beam is shown in the attached figure. Figure 7 As shown.

[0029] In one embodiment, please refer to the appendix. Figure 2 and attached Figure 3 The precast beam 100mm has no protruding reinforcing bars, especially on the sides, or only very short reinforcing bars. When the hinge joint does not need to be filled with concrete, a hinge joint mold is used to fill the space at the hinge joint, aligning the upper surface of the hinge joint mold with the upper surface of the precast beam 100mm. After pouring the concrete layer, the hinge joint mold is removed along with the bottom formwork. The cross-sectional view of the resulting formed hollow slab beam is attached. Figure 3 As shown, at this time, there is no concrete filling at the hinge joint between the two adjacent precast beams 100. In the post-tensioning step, it is only necessary to tension the post-tensioning steel strands on the precast beams 100.

[0030] In another embodiment, please refer to the appendix. Figure 4 Appendix Figure 5 Appendix Figure 6 In step S2, if the hollow slab beam requires a hinge joint, several reinforcing cages are arranged at intervals along the length of the hinge joint, and several steel strands are laid within the hinge joint. Any of the steel strands within the hinge joint is laid along the length of the beam and its edges, intersecting with those of the reinforcing cages along the laying path, are tied together. A perforated tube 300 for the post-tensioned steel strand is pre-installed within the hinge joint, and the precast beam reinforcing bars embedded in the precast beam 100 are bent towards the inside of the hinge joint. When the hinge joint needs to be filled with concrete, using the hinge joint as a structural element to connect the concrete layer and the precast beam 100 at the hinge joint can improve the overall integrity of the bridge and reduce structural weakness and longitudinal cracking at the hinge joint.

[0031] Specifically, the structure of the precast beam 100 is as shown in the attached figure. Figure 4As shown, in addition to the necessary bottom plate 110, web plate 120, and top plate 130, the arrangement of reinforcing bars on the precast beam 100 before pouring needs to be considered. Generally, in the cast-in-place precast beam 100, the bottom transverse embedded steel bars 140 arranged horizontally at the bottom plate 110 protrude from the precast beam 100 at both ends and are partially exposed. After the precast beam 100 is demolded, the protruding parts of the bottom transverse embedded steel bars 140 are close to the surface of the precast beam 100. The bottom oblique embedded steel bars 150 arranged diagonally at the bottom plate 110 protrude from the precast beam 100 at one end and are partially exposed. After the precast beam 100 is demolded, the protruding parts of the bottom oblique embedded steel bars 150 are close to the surface of the precast beam 100. The top transverse embedded steel bars 160 arranged horizontally at the top plate 130 protrude from the precast beam 100 at both ends and are partially exposed. After the precast beam 100 is demolded, the protruding parts of the top transverse embedded steel bars 160 are close to the surface of the precast beam 100. The top of the side vertical embedded steel bars 170 arranged vertically at the web plate 120 protrudes from the precast beam 100 and is partially exposed. In the top embedded door reinforcement bar 180 at the top plate 130, only the foot of the top embedded door reinforcement bar 180 is embedded in the precast beam 100.

[0032] Please refer to the appendix for details. Figure 4 and attached Figure 5 In step S2, the method of bending the precast beam reinforcement embedded in the precast beam 100 toward the inside of the hinge joint is specifically as follows: Open the precast beam reinforcement bars lateral in the 100mm width direction outward; The precast beam reinforcement bars above the precast beam 100 are bent outwards into a horizontal shape, and the precast beam reinforcement bars above the two connected precast beams 100 overlap in the hinge joint.

[0033] Compared to the precast beam 100, the bending process is specifically explained as follows: the bottom transverse embedded steel bars 140 are bent upwards through the precast beam 100; the bottom oblique embedded steel bars 150 are bent downwards through the precast beam 100; the top transverse embedded steel bars 160 are bent upwards through the precast beam 100; and the side vertical embedded steel bars 170 are bent downwards through the precast beam 100. After the steel bars embedded in the precast beam 100 are bent and laid, a steel cage 500 is formed by bending the steel bars into a rectangular or U-shape within the hinge joint. The steel strands 400 are tied and fixed along the left and right rectangular sides of the steel cage 500 and intersecting within the hinge joint. At least two post-tensioned steel strand perforated pipes 300 are embedded at intervals above and below within the steel cage 500. The post-tensioned steel strand perforated pipes 300 at this location and the post-tensioned steel strand perforated pipes 300 at the precast beam 100 should correspond one-to-one in the height direction. After the hinge joint and concrete layer are poured, the concrete layer and the precast beam 100 are integrated with each embedded steel bar, the steel strand 400 in the hinge joint and the steel cage 500 to improve the strength of the hinge joint.

[0034] It is understandable that the bottom edge of the 500mm rebar cage is close to the 200mm pre-tensioned steel strands, and the top edge is close to the 600mm inner rebar mesh.

[0035] After the precast beam 100 is laid, the bottom transverse embedded steel bars 140, the bottom diagonal embedded steel bars 150, the top transverse embedded steel bars 160, and the side vertical embedded steel bars 170 all extend into the hinge joint. As the concrete in the hinge joint is poured, the adjacent precast beam 110 is combined with the concrete into a whole.

[0036] Preferably, the bent section of the bottom transverse pre-embedded steel bar 140 extends into the steel cage 500, the bent sections of the bottom oblique pre-embedded steel bar 150 and the top transverse pre-embedded steel bar 160 are close to the lateral edge of the steel cage 500, and the horizontal section of the top transverse pre-embedded steel bar 150 after bending completely covers the width of the hinge joint. Without affecting the overall structural stability, the length of each steel bar extending into the hinge joint is increased, the angle of the bottom oblique pre-embedded steel bar 150 extending into the hinge joint is controlled, and the overall integrity of the bridge structure after casting is improved.

[0037] Secondly, this invention also proposes a hollow slab beam, characterized by being constructed using a sequential tensioning method. This method retains the advantages of the original pre-tensioned hollow slab beam construction, eliminates its drawbacks, and improves the overall performance of the hollow slab beam.

[0038] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A construction method for hollow slab beams using sequential tensioning, characterized in that, Includes the following steps, S1. Fabrication of precast beams: This includes fabricating precast edge beams and precast middle beams; If the hollow slab beam does not require hinge joints, the post-tensioned steel strand perforation tubes are reserved in the mold of the middle beam and the side beam of the precast beam respectively. The hollow precast side beam and the middle beam of the precast beam are made by pre-tensioning method. After demolding, the post-tensioned steel strand perforations are formed in the web of the side beam and the web of the middle beam of the precast beam along the length direction respectively. If a hollow slab beam requires a hinge joint, a perforated tube for the post-tensioned steel strand is reserved in the precast side beam mold. The hollow precast side beam and the middle beam of the precast beam are made using the pre-tensioning method. After demolding, the perforated tube for the post-tensioned steel strand is formed along the length of the web of the precast side beam. S2. Laying hollow slab beams: Several precast beams are laid on the bottom formwork at intervals according to the layout of precast beams at both ends and several precast beams in the middle. Hinges are formed between the precast beams at both ends and between the precast beams in the middle. If the hollow slab beam does not require hinge joints, use a hinge joint mold to fill the space at the hinge joint and align the upper surface of the hinge joint mold with the upper surface of the precast beam. If a hinge joint is required for a hollow slab beam, a perforated tube for the post-tensioned steel strands should be reserved in the hinge joint along the length direction. S3. Pouring the concrete layer: Lay the inner steel mesh above the hollow slab beam, lift the bottom formwork, erect the beam, pour the concrete layer, and remove the bottom formwork and cure after the concrete layer reaches its strength. If the hollow slab beam does not require hinge joints, the hinge joint mold will be removed along with the bottom formwork. If a hollow slab beam requires a hinge joint, after the concrete layer is poured, post-tensioned steel strand perforations are formed in the hinge joint along the length direction. S4. Tensioning: Install post-tensioned steel strands through the holes and tension the post-tensioned steel strands. S5. Paving with asphalt: Pave an asphalt layer on the surface of the concrete layer and cure it.

2. The construction method for hollow slab beams using the sequential tensioning method as described in claim 1, characterized in that: In step S2, if the hollow slab beam requires a hinge joint, several steel cages are arranged at intervals along the length direction within the hinge joint, and several steel strands are laid within the hinge joint. Any of the steel strands within the hinge joint is laid along the length direction and the edges of the steel cages that intersect with its laying path are tied together. A perforated tube for the post-tensioned steel strand is reserved within the hinge joint, and the precast beam steel bars embedded in the precast beam are bent toward the inside of the hinge joint.

3. The construction method for hollow slab beams using the sequential tensioning method as described in claim 2, characterized in that, In step S2, the method of bending the precast beam reinforcement embedded in the precast beam toward the inside of the hinge joint is specifically as follows: Open the precast beam reinforcement bars laterally in the width direction of the precast beam outwards; The precast beam reinforcement bars above the precast beam are bent outwards into a horizontal shape, and the precast beam reinforcement bars above two connected precast beams overlap in the hinge joint.

4. A hollow slab beam, characterized in that, It was constructed using the sequential tensioning method for hollow slab beams.

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