Temporary prestress connecting structure and method for assembling prefabricated segmental box girders

Abstract

The invention discloses a temporary prestress connecting structure and method for prefabricated segmental box girder splicing, the temporary prestress connecting structure comprises concrete rib plates arranged on the inner sides of webs on the two sides of a segmental box girder and a plurality of pretightening force applying units, a plurality of preformed holes are symmetrically formed in the two concrete rib plates in the height direction, and the pretightening force applying units are arranged in the preformed holes. The pre-tightening force applying unit comprises a finish rolling deformed steel bar, a pressure bearing plate and a fastening nut; the finish rolling deformed steel bar sequentially penetrates through the preformed holes, located on the same side and at the same height, in the two adjacent sections of box girders, and the two ends of the finish rolling deformed steel bar are fixed through the bearing plates and the fastening nuts respectively. According to the method, temporary holes formed in the top and bottom plates of the segmental box girder can be effectively reduced, the integrity and construction safety of the girder body are guaranteed to the maximum extent while the temporary prestress construction quality is guaranteed, and meanwhile the problems of high-altitude risks and embedded hole plugging water seepage of a traditional steel tooth sill scheme are solved.

Description

Technical Field

[0001] This invention relates to the field of prestressed construction technology for precast segmental box girders. More specifically, this invention relates to a temporary prestressed connection structure and method for assembling precast segmental box girders. Background Technology

[0002] To meet the requirements of construction period and quality, precast beams are often used for the superstructure of highway bridges. Temporary prestressing is required for inter-segment splicing during on-site installation of precast beams. Currently, the traditional method for applying temporary prestress between segmental box girders mostly uses steel toothed brackets. These brackets utilize high-strength bolts to fasten to pre-drilled holes in the bridge's top or bottom slab. Then, a set of corresponding steel toothed brackets on two adjacent segmental beams are connected by long bolts, tensioned at both ends, thus applying temporary compressive stress to the spliced ​​segments, bringing the two segmental beams together tightly, preparing for the subsequent application of permanent prestress. The specific process involves first installing steel toothed supports using pre-drilled holes. After adjacent segments are in place and epoxy resin is applied to the joint surfaces, temporary prestressing tendons are tensioned using the steel toothed supports. During tensioning, the bottom plate is tensioned first, followed by the top plate, with staged tensioning. All oil pumps must apply load consistently and evenly. Before tensioning, check that the threaded steel bars are straight and ensure concentricity of the threaded steel bars, steel toothed supports, and jacks. Check that all bolts are tightened and free from jamming, and that the jacks and steel toothed supports are tightly fitted and free from foreign objects. Afterward, remove the tensioning bolts and dismantle the steel toothed supports. For large-span segmental beams, high beams, and single-box double-cell segmental beams, in addition to steel toothed supports on the top and bottom plates, a certain number of steel toothed supports also need to be installed on the web.

[0003] In the existing method of applying temporary prestress to segmental beams, multiple steel toothed sills are used to temporarily connect the segments. Although this can improve the splicing accuracy of adjacent blocks, it can also lead to some problems: (1) Many holes in the top and bottom plates: 1 steel toothed sill requires 8 reserved holes, and the amount of hole repair is large, which has a significant impact on the later operation of the section; (2) Complex procedures: There are many anchor bolts, washers and nuts, and the workload of installation and disassembly is large; (3) Inconvenient construction: Traditional steel toothed sills need to install fasteners on the other side, and it is not convenient to construct on the outside of the web. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0005] To achieve these objectives and other advantages according to the present invention, a temporary prestressed connection structure and method for assembling precast segmental box girders are provided. The present invention is achieved through the following technical solution: This invention provides a temporary prestressed connection structure for assembling precast segmental box girders, comprising concrete ribs disposed on the inner side of the webs on both sides of the segmental box girder and multiple prestressing force application units. Multiple reserved holes are symmetrically opened on the two concrete ribs along the height direction. Each prestressing force application unit includes a precision-rolled threaded steel bar, a pressure plate, and a fastening nut. The precision-rolled threaded steel bar passes sequentially through the reserved holes located on the same side and at the same height on two adjacent segmental box girders, and its two ends are fixed by the pressure plate and the fastening nut, respectively.

[0006] Preferably, the concrete rib is provided along the entire length of the web height of the segmental box girder, and the concrete rib is provided in the middle of the web along the bridge direction. The width and thickness of the concrete rib are both 20~25cm.

[0007] Preferably, the reserved hole is interference-fitted with the precision-rolled threaded steel bar.

[0008] Preferably, the precision-rolled threaded steel bars connected to the adjacent segmental box girders on both sides of one of the concrete ribs are arranged alternately vertically.

[0009] Preferably, multiple key blocks and keyways are symmetrically arranged on the front and rear end faces of the segmental box girder, and the key blocks are in the shape of a frustum.

[0010] The present invention also provides a method for applying prestress to a temporary prestressed connection structure for assembling precast segmental box girders, comprising the following steps: S1. Precast each segment of the box girder, and integrally cast the concrete ribs on the inner side of the web on both sides of the segment of the box girder. The two concrete ribs are symmetrically provided with multiple reserved holes along the height direction. S2. Hoist the segment box girder to be installed, and gradually move the segment box girder to be installed closer to the installed segment box girder, fine-tune the alignment until it is fully spliced, and symmetrically install multiple prestressing units on the concrete ribs of the two segment box girders. S3. Install the jacks and tension each of the preload application units to the designed preload; S4. Repeat steps S2 to S3 until the permanent internal prestressing of the entire span is applied and grouting is completed.

[0011] Preferably, in step S2, the finely rolled threaded steel bars that connect to the adjacent segmental box girders on both sides of the same concrete rib of the segmental box girder are arranged alternately, and the bearing plate and the fastening nut are installed in sequence at the end of the finely rolled threaded steel bar that extends out of the concrete rib, and are initially tightened in place with a hydraulic wrench.

[0012] Preferably, in step S3, each of the pretensioning force application units applies pretensioning force in a symmetrical and synchronous step-by-step tensioning sequence from top to bottom and left and right sides; after tensioning to the required position, the fastening nut is tightened with a hydraulic wrench, and the load is locked by the mechanical engagement between the fastening nut and the bearing plate.

[0013] Preferably, in step S2, after the segment box girder to be installed is hoisted, adhesive is first applied to the matching end face, and then it is gradually moved closer to the installed segment box girder; in step S3, when the temporary prestressing is applied between two adjacent segment box girders, the matching end face should generate a pressure of not less than 0.3 MPa.

[0014] Preferably, in step S4, after the assembly, joint curing, and tensioning and grouting of the permanent prestressing tendons of each box girder segment are completed, and after the installation of two box girder segments has been delayed, the temporary prestressing structure on that box girder segment can be released. This invention has at least the following beneficial effects: The present invention provides a temporary prestressed connection structure and method for assembling precast segmental box girders. By setting concrete ribs on the web and then drilling reserved holes in the concrete ribs to pass through the temporary prestressing, the assembly of segmental box girders can be achieved. Compared with traditional steel toothed scaffolding, it can effectively reduce the number of temporary openings in the top and bottom plates of the segmental box girder. While ensuring the construction quality of temporary prestressing, it maximizes the integrity of the beam and construction safety, and avoids the high-altitude risks and water seepage problems caused by the sealing of pre-embedded holes in the traditional steel toothed scaffolding scheme.

[0015] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the temporary prestressed connection structure for assembling precast segmental box girders as described in this invention; Figure 2 This is a schematic diagram of the structure when three consecutive box girder segments are connected by the temporary prestressed connection structure according to the present invention; Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0018] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] like Figure 1 and Figure 2 As shown, the present invention provides a temporary prestressed connection structure for assembling precast segmental box girders, including concrete ribs 3 disposed on the inner side of the webs 2 on both sides of the segmental box girder 1 and multiple prestressing force application units. Multiple reserved holes 4 are symmetrically opened on the two concrete ribs 3 along the height direction. The prestressing force application unit includes a finely rolled threaded steel bar 6, a pressure plate 7 and a fastening nut 8. The finely rolled threaded steel bar 6 passes sequentially through the reserved holes 4 located on the same side and at the same height on two adjacent segmental box girders 1, and both ends are fixed by the pressure plate 7 and the fastening nut 8 respectively.

[0020] In this technical solution, concrete ribs 3 are provided on the inner sides of the webs 2 on both sides of the box girder 1 within the box chamber. Temporary prestressing is achieved through pre-drilled holes 4 in the concrete ribs 3, generating pressure on the matching end faces 9 of the box girder 1. This temporary prestressed connection structure for assembling precast box girders avoids openings in the beam structure, improves structural integrity, and, because it operates within the box chamber, carries low safety risks, ensuring both construction safety and quality.

[0021] In another technical solution, the concrete rib 3 is arranged along the height direction of the web 2 of the segmental box girder 1, and is located in the middle of the web 2 along the bridge direction. The width and thickness of the concrete rib 3 are both 20-25 cm. The concrete rib 3 is arranged vertically along its entire length, forming an integral structure with the segmental box girder 1, thereby improving the strength of the concrete rib 3 and ensuring the quality of temporary prestressing construction.

[0022] In another technical solution, the reserved hole 4 is interference-fitted with the fine-rolled threaded steel bar 6 to facilitate smooth temporary prestressing tensioning; and no grouting is applied between the reserved hole 4 and the fine-rolled threaded steel bar 6.

[0023] In another technical solution, the precision-rolled threaded steel bars 6 connected to the adjacent segmental box girders 1 on one of the concrete ribs 3 are arranged in a staggered manner. (Refer to...) Figure 2 In the reserved holes 4 on the middle concrete rib 3, finely rolled threaded steel bars 6 are staggered from top to bottom to connect with the concrete rib 3 on the two side segment box girders. That is, when the segment box girder only needs to be connected to the box girder on one side, there is a reserved hole 4 between two adjacent finely rolled threaded steel bars 6 on the concrete rib 3.

[0024] In another technical solution, multiple key blocks 5 and keyways are symmetrically arranged on the front and rear end faces of the segmental box girder 1, respectively. The key blocks 5 are frustum-shaped. The front and rear end faces of the segmental box girder 1 are the matching end faces 9 for splicing with other box girders, and the shape of the keyway matches the shape of the key block 5. In order to facilitate the transfer of shear force between the key block 5 and the keyway to the stressed reinforcement on the end face of the box girder segment, the inclination angle of the upper and lower mating surfaces of the key block 5 and the keyway is close to 45°.

[0025] The present invention also provides a method for applying prestress to a temporary prestressed connection structure for assembling precast segmental box girders, comprising the following steps: S1. Precast each segment box girder 1, and integrally cast the concrete ribs 3 on the inner side of the webs 2 on both sides of the segment box girder 1. The two concrete ribs 3 are symmetrically provided with multiple reserved holes 4 along the height direction. S2. Hoist the segment box girder 1 to be installed, and gradually move the segment box girder 1 to be installed closer to the installed segment box girder, finely adjust the alignment until it is fully spliced, and symmetrically install multiple pre-tightening force application units on the concrete ribs 3 of the two segment box girders 1. Furthermore, after the segmental box girder to be installed is hoisted, adhesive is first applied to the matching end face, and then it is gradually moved closer to the installed segmental box girder. When installing the preload application unit, the threaded steel bars 6 connected to the adjacent segment box girders on the same concrete rib 3 of the segment box girder 1 are staggered vertically. The bearing plate 7 and the fastening nut 8 are installed sequentially at the end of the threaded steel bar 6 that extends out of the concrete rib 3, and are initially tightened in place with a hydraulic wrench.

[0026] S3. Install the jacks and tension each of the preload application units to the designed preload; so that the matching end face generates a pressure of not less than 0.3MPa.

[0027] Specifically, each of the pretensioning force application units applies pretensioning force in a symmetrical and synchronous step-by-step tensioning sequence from top to bottom and left and right sides; after tensioning to the required position, the fastening nut 8 is tightened with a hydraulic wrench, and the load is locked by the mechanical engagement between the fastening nut 8 and the bearing plate 7.

[0028] S4. Repeat steps S2 to S3 until the permanent internal prestressing of the entire span is applied and grouting is completed.

[0029] After the assembly, joint curing, tensioning and grouting of the permanent prestressed tendons of each box girder segment are completed, and after the installation of two box girder segments is delayed, the temporary prestressed structure on that box girder segment can be released.

[0030] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A temporary prestressed connection structure for assembling precast segmental box girders, characterized in that, It includes concrete ribs set on the inner side of the webs on both sides of the segmental box girder and multiple pre-tensioning units. Multiple reserved holes are symmetrically opened on the two concrete ribs along the height direction. The pre-tensioning unit includes a finely rolled threaded steel bar, a pressure plate and a fastening nut. The finely rolled threaded steel bar passes through the reserved holes on the same side and at the same height on two adjacent segmental box girders in sequence, and its two ends are fixed by the pressure plate and the fastening nut, respectively.

2. The temporary prestressed connection structure for assembling precast segmental box girders according to claim 1, characterized in that, The concrete ribs are installed along the length of the web of the segmental box girder, and are located in the middle of the web along the bridge direction. The width and thickness of the concrete ribs are both 20-25 cm.

3. A temporary prestressed connection structure for assembling precast segmental box girders according to claim 1, characterized in that, The reserved hole is interference-fitted with the precision-rolled threaded steel bar.

4. A temporary prestressed connection structure for assembling precast segmental box girders according to claim 1, characterized in that, The precision-rolled threaded steel bars on one of the concrete ribs are staggered vertically to connect with the adjacent segmental box girders on both sides.

5. A temporary prestressed connection structure for assembling precast segmental box girders according to claim 1, characterized in that, Multiple key blocks and keyways are symmetrically arranged on the front and rear end faces of the segmental box girder, and the key blocks are in the shape of a frustum.

6. A method for applying prestress to a temporary prestressed connection structure for assembling precast segmental box girders as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Precast each segment of the box girder, and integrally cast the concrete ribs on the inner side of the web on both sides of the segment of the box girder. The two concrete ribs are symmetrically provided with multiple reserved holes along the height direction. S2. Hoist the segment box girder to be installed, and gradually move the segment box girder to be installed closer to the installed segment box girder, fine-tune the alignment until it is fully spliced, and symmetrically install multiple prestressing units on the concrete ribs of the two segment box girders. S3. Install the jacks and tension each of the preload application units to the designed preload; S4. Repeat steps S2 to S3 until the permanent internal prestressing of the entire span is applied and grouting is completed.

7. The prestressing application method as described in claim 6, characterized in that, In step S2, the finely rolled threaded steel bars that connect to the adjacent segmental box girders on both sides of the same concrete rib of the segmental box girder are staggered vertically. The bearing plate and the fastening nut are installed sequentially at the end of the finely rolled threaded steel bar that extends out of the concrete rib, and are initially tightened in place with a hydraulic wrench.

8. The prestressing application method as described in claim 6, characterized in that, In step S3, each of the pretensioning force application units applies pretensioning force in a symmetrical and synchronous step-by-step tensioning sequence from top to bottom and left and right sides; after tensioning to the required position, the fastening nut is tightened with a hydraulic wrench, and the load is locked by the mechanical engagement between the fastening nut and the bearing plate.

9. The prestressing application method as described in claim 6, characterized in that, In step S2, after the segment box girder to be installed is hoisted, adhesive is first applied to the matching end face, and then it is gradually moved closer to the installed segment box girder; in step S3, when the temporary prestressing is applied between two adjacent segment box girders, the matching end face should generate a pressure of not less than 0.3MPa.

10. The prestressing application method as described in claim 6, characterized in that, In step S4, after each segment of the box girder is assembled, the adhesive joint is cured, the permanent internal prestressing tendons are tensioned and grouted, and the installation of two segments of the box girder is delayed, the temporary prestressing structure on that segment of the box girder can be released.

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