A prestressed U-shaped aqueduct and post-cast tie rod connection structure

Abstract

The present invention belongs to the field of prefabrication of prestressed U-shaped aqueducts, and specifically relates to a connection structure between a prestressed U-shaped aqueduct and a post-cast tie rod; a "concave-convex" mortise and tenon structure is adopted at the interface between the reserved joint of the aqueduct top beam and the post-cast tie rod, the reserved joint and the aqueduct main body are cast and formed as one piece, the end of the reserved joint is designed to be "concave", and the end of the post-cast tie rod is designed to be "convex"; the internal reinforcement of the reserved joint is extended outward, and the extended reinforcement is implanted in the post-cast tie rod; in response to the problem that the bonding surface between new and old concrete is too weak caused by the flat section connection method of traditional post-cast concrete, the advantage of the "concave-convex" mortise and tenon design is that the "concave-convex" mortise and tenon design adds two shear sections parallel to the axial direction of the tie rod inside the interface, and fully utilizes the restraining effect of the stirrups on the bonding joint surface, and adopts local widening treatment at the "concave-convex" interface, thereby improving the tensile performance of the concrete when the tie rod end bears the main load.

Description

Technical Field

[0001] The invention belongs to the field of prefabrication of prestressed U-shaped aqueducts, and particularly relates to a connection structure between a prestressed U-shaped aqueduct and a post-cast tie rod. Background Art

[0002] An aqueduct is an overhead water-transportation structure that connects a waterway system, spanning mountains, valleys, and roads. It is commonly used in water conservancy projects such as agricultural irrigation, sediment removal, flood control, and navigation. To ensure the stability of the aqueduct's side walls and improve the lateral load-bearing conditions during operation, tension rods connecting the two side beams are often installed at the top of the aqueduct to share the load.

[0003] However, the existence of tie rods hinders the use of slipforms during aqueduct construction, seriously affecting construction efficiency and significantly increasing construction difficulty. Therefore, if slipform construction is adopted, prefabricated load-bearing tie rods are required. After the main construction of the aqueduct is completed, the tie rods are connected to the aqueduct top beam through the reserved post-cast strips. During the operation of the aqueduct, the ends of the tie rods (i.e., the connection between the tie rods and the prestressed U-shaped aqueduct top beam) are the key load-bearing parts. The post-pouring concrete method significantly increases the risk of cracking at the joints between the new and old concrete, causing the tie rod steel bars to rust, affecting the structural stability and durability. Summary of the Invention

[0004] The purpose of the present invention is to ensure that the slipform construction process of the aqueduct main body is not affected when the tie rods are set, and to effectively improve the mechanical properties of the post-cast concrete at the connection between the aqueduct top beam and the tie rods to maintain structural stability.

[0005] The present invention provides the following technical solution: a prestressed U-shaped aqueduct and a post-cast tie rod connection structure, wherein the reserved joint of the aqueduct top beam and the post-cast tie rod interface adopts a "concave-convex" mortise and tenon structure, the reserved joint and the aqueduct main body are cast as one piece, the end of the reserved joint is designed to be "concave", and the end of the post-cast tie rod is designed to be "convex"; the internal reinforcement of the reserved joint extends outward, and the extended reinforcement is implanted in the post-cast tie rod.

[0006] Furthermore, the "concave" groove on the reserved joint is vertical; a row of longitudinal stress-bearing steel bars are arranged at the top and bottom of the reserved joint, respectively, and frame steel bars and stirrups are arranged in conjunction with them; the frame steel bars are arranged in two rows along the vertical direction, and the two rows of frame steel bars are aligned with the longitudinal stress-bearing steel bars at the head and tail of the row respectively, the stirrups are hooped outside the frame steel bars and the longitudinal stress-bearing steel bars, and there is at least one transverse stress-bearing steel bar in the "concave" groove.

[0007] Furthermore, the combined formwork with reserved joints includes one flat formwork for the recess, two inner wall folding formworks, two end "L" formworks, two side panels and one bottom panel;

[0008] Rebar reserved holes are opened on the flat formwork at the concave part, the inner wall folding formwork and the end "L" formwork;

[0009] The flat template at the concave part and the first folding plates of the inner wall folding templates on both sides together form the "concave" groove bottom template; the second folding plate of the inner wall folding template and the vertical plates of the end "L"-shaped template form the "concave" groove wall template; the horizontal plate of the end "L"-shaped template serves as the end template of the reserved joint; the side plates serve as the side template of the reserved joint; and the bottom plate serves as the bottom template of the reserved joint.

[0010] The flat template at the recess, the folding template of the inner wall, the "L" template at the end, the side plates and the bottom plate are detachably connected to form a combined template, and the side plates and the bottom plate are detachably connected to the template of the aqueduct body.

[0011] Furthermore, there is a row of longitudinal steel bar reserved holes at the top and bottom of the flat template at the recess, including semicircular holes at the template joints and circular holes passing through the template; external snap-on bolt holes are arranged on both sides of the flat template at the recess, which can be connected to the inner wall folding template with bolts; external snap-on bolt holes are arranged at the bottom, which can be connected to the base plate with bolts.

[0012] Furthermore, the inner wall folding formwork is composed of two flat formworks connected by a rotating shaft, and both flat formworks can be freely rotated, folded, and unfolded around the shaft; embedded bolt holes are arranged on the first folding plate of the inner wall folding formwork, and external buckle bolt holes are arranged on the second folding plate; the first folding plate is connected to the flat formwork at the recessed part with bolts, and semicircular longitudinal steel bar reserved holes are arranged; the second folding plate is connected to the end "L"-shaped formwork with bolts, and semicircular stirrup reserved holes are arranged.

[0013] Furthermore, circular longitudinal steel bar reserved holes are arranged on the horizontal plate of the end "L"-shaped formwork, and semicircular stirrup reserved holes are arranged on the vertical plate; embedded bolt holes are arranged on the vertical plate, and external buckle bolt holes are arranged on the horizontal plate. The vertical plate and the horizontal plate are respectively connected to the inner wall folding formwork and the side plates with bolts, and the bottom is arranged with external buckle bolt holes, which are connected to the bottom plate with bolts.

[0014] Furthermore, the post-cast tie rod is locally widened at the "concave-convex" interface.

[0015] Furthermore, the extension length of the vertical reinforcement and the longitudinal stress-bearing reinforcement is 220 mm.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] The post-cast tie rod method enables the lifting device of the slipform to move freely in the axial direction during the main construction process, effectively avoiding the obstruction of the tie rod to the slipform, and solving the problems of excessive investment cost and time cost consumption brought about by the traditional formwork construction mode. At the same time, in order to solve the problems of poor mechanical properties of the tie rods at the interface caused by the post-casting of the tie rods, obvious cracks in the concrete under the action of high tensile stress, corrosion of the stressed longitudinal steel bars, resulting in tie rod breakage and instability of the aqueduct side walls, the present invention adopts a "concave-convex" mortise and tenon design at the interface between the aqueduct top beam and the post-cast tie rods. The end of the top beam is designed to be "concave", and the end of the post-cast tie rod is designed to be "convex"; at the same time, a local widening treatment is adopted at the "concave-convex" interface. In response to the problem of the weak interface between the new and old concrete caused by the traditional flat-section connection method of post-cast concrete, the advantage of the "concave-convex" mortise and tenon design is that the main load borne by the connecting rod is the combined force of the axial tensile stress generated by the expansion of the two side walls and the tensile stress generated by the bending moment due to its own weight, as well as the characteristic of concrete with poor tensile performance but relatively good shear performance. The "concave-convex" mortise and tenon design adds two shear sections parallel to the axis of the rod inside the interface, while making full use of the restraining effect of stirrups on the joint surface, and adopts local widening treatment at the "concave-convex" interface, which improves the tensile performance of concrete when the end of the rod bears the main load.

[0018] To accommodate the casting of concave joints at top beam ends and complex reinforcement requirements, the present invention provides a modular formwork for concave joints at top beam ends. The formwork comprises one flat recessed formwork, two folding inner wall forms, two L-shaped end forms, two side panels, and one bottom panel. The modular formwork is bolted together using external and internal bolt holes between adjacent forms, resulting in a tightly assembled, structurally stable formwork that is easily disassembled. Furthermore, by adjusting the formwork's pre-reinforcement holes and the appropriate assembly sequence, the required overlap lengths for transverse and longitudinal reinforcement, and the extension of stirrups, as well as complex layout requirements, can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the interface position between the aqueduct top beam and the post-cast tie rod;

[0020] Figure 2 This is a schematic diagram of the connection between the reserved joint and the post-cast tie rod;

[0021] Figure 3 Schematic diagram of internal reinforcement of reserved joints;

[0022] Figure 4 Schematic diagram of internal reinforcement of reserved joint (cross-section);

[0023] Figure 5 A schematic diagram of the structure of a modular template with reserved joints;

[0024] Figure 6 It is a structural diagram of the flat template at the concave part;

[0025] Figure 7 It is a structural diagram of the inner wall folding template;

[0026] Figure 8 It is a structural diagram of the end "L" type template;

[0027] Figure 9 It is a schematic diagram of the folding of the inner wall folding template;

[0028] Figure 10 This is a schematic diagram of the connection between the reserved joint and the post-cast tie rod (stereoscopic view);

[0029] In the figure: 1-aqueduct top beam; 2-reserved joint; 3-post-cast tie rod; 4-longitudinal stress-bearing steel bars; 5-standing steel bars; 6-stirrups; 7-flat formwork for recessed areas; 8-folding formwork for inner walls; 9-end "L"-type formwork; 10-side panels; 11-bottom panels. DETAILED DESCRIPTION

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] like Figure 2 As shown: a prestressed U-shaped aqueduct and post-cast tie rod connection structure, the reserved joint 2 of the aqueduct top beam 1 and the post-cast tie rod 3 adopt a "concave-convex" mortise and tenon structure at the interface, the reserved joint 2 and the aqueduct main body are cast as one piece, the end of the reserved joint 2 is designed to be "concave", and the end of the post-cast tie rod 3 is designed to be "convex"; the first cast part is the "concave" interface of the reserved joint 2 at the end of the top beam, and the post-cast part is the "convex" interface of the tie rod end; the post-cast tie rod 3 is locally widened at the "concave-convex" interface; the internal reinforcement of the reserved joint 2 extends outward, and the extended reinforcement is implanted into the post-cast tie rod 3.

[0032] like Figure 3 、 Figure 4 As shown: the "concave" groove on the reserved joint 2 is vertical; a row of longitudinal stress-bearing steel bars 4 are arranged at the top and bottom of the reserved joint 2, respectively, and frame steel bars 5 and stirrups 6 are arranged in conjunction with them; the frame steel bars 5 are arranged in two rows along the vertical direction, and the two rows of frame steel bars 5 are aligned with the longitudinal stress-bearing steel bars 4 at the head and tail of the row respectively, and the stirrups 6 are hooped around the frame steel bars 5 and the longitudinal stress-bearing steel bars 4, and there is at least one transverse stress-bearing steel bar in the "concave" groove.

[0033] Considering that the main load borne by the tie rod is the combined force of the axial tensile stress generated by the expansion of the two side walls of the aqueduct and the tensile stress generated by the bending moment due to its own weight, and the characteristics of concrete with poor tensile performance but relatively good shear performance, the "concave-convex" mortise and tenon design adds two shear sections parallel to the axis of the tie rod and transverse stress-bearing steel bars inside the interface, which significantly improves the tensile performance of concrete when the end of the tie rod bears the main load.

[0034] like Figure 3 、 Figure 4 As shown: Take the "concave-convex" type interface designed with the dimensions in the figure as an example (the interface dimensions and steel bar selection and layout methods here are only examples, and the design should be based on actual conditions in the project): the cross-section of the tie rod is a rectangle of 500×500mm, the interface recess depth of the reserved joint 2 is 500mm, and the width of the recess is 300mm. The concrete 301 used during pouring is grade C30; the longitudinal stress reinforcement 4, model HRB400, diameter 22mm, the longitudinal stress reinforcement 4 overhanging lap length is 220mm; the erection reinforcement 5 is arranged in 2 rows in the vertical direction (2 bars per row), model HRB335, diameter 12mm; stirrups 6, model HRB335, diameter 8mm. Based on the above design parameters, the improvement in the tie rod's resistance to axial cracking brought about by the change in interface type is calculated using the following formula:

[0035]

[0036] Where: K - improvement coefficient of anti-cracking performance of tie rod concrete;

[0037] f t ——Design value of concrete tensile strength, N / mm 2 ;

[0038] A——tensile cross-sectional area, mm 2 ;

[0039] f v ——Design value of concrete shear strength, N / mm 2 ;

[0040] S——shear cross-sectional area, mm 2 .

[0041] Calculations show that after adopting the "concave-convex" type interface, the crack resistance of the tie rod concrete is improved by nearly 4 times compared with the flat section connection.

[0042] like Figure 5As shown, in order to cooperate with the casting of the reserved joints at the ends of the top beams and the requirements of complex reinforcement, this embodiment provides a combined formwork for the reserved joints 2, which includes a flat formwork 7 for the recessed area, two folding inner wall formworks 8, two "L"-type end formworks 9, two side panels 10 and a bottom plate 11. The formworks are connected with bolts through reserved bolt holes; the side panels 10 and the bottom plate 11 are connected to the formwork of the aqueduct body with bolts.

[0043] In order to meet the complex reinforcement requirements, the following steps must be followed when installing the formwork and laying out the steel bars: ① Fix the bottom plate 11 and tie the longitudinal stress-bearing steel bars 4; ② Fix the inner wall folding formwork 8 at the corresponding position of the bottom plate 11; ③ Fix the recessed flat formwork 7 at the corresponding position of the bottom plate 11, and connect it to the inner wall folding formwork 8 with bolts; ④ Tie and fix the transverse stress-bearing steel bars; ⑤ Fix the end "L"-type formwork 9 at the corresponding position of the bottom plate 11, and connect it to the inner wall folding formwork 8 with bolts; ⑥ Install the side panel 10, and connect the side panel 10 to the bottom plate 11 and the end "L"-type formwork 9 with bolts.

[0044] The order for removing the formwork is as follows: ① Remove the flat formwork 7 at the recessed area; ② Remove the "L"-shaped formwork 9 at the end; ③ Fold the inner wall folding formwork 8 and remove it from the gap between the steel bars; ④ Remove the side panels 10 and the bottom panel 11.

[0045] like Figure 6 As shown, the top and bottom of the recessed flat formwork 7 each have a row of holes reserved for longitudinal reinforcement, including semicircular holes at the formwork joints and circular holes that pass through the formwork. Each side of the recessed flat formwork 7 has an external bolt hole (located on two protruding connecting lugs) for bolt connection to the inner wall folding formwork 8; the bottom has an external bolt hole (located on the protruding connecting lug) for bolt connection to the base plate 11.

[0046] like Figure 7 As shown: the inner wall folding formwork 8 is composed of two flat formworks connected by a rotating shaft, and the two flat formworks can be freely rotated, folded and unfolded around the shaft; the first folding plate of the inner wall folding formwork 8 is arranged with embedded bolt holes, and the second folding plate is arranged with external buckle bolt holes, the first folding plate is connected to the recessed flat formwork 7 with bolts, and semicircular longitudinal steel bar reserved holes are arranged; the second folding plate is connected to the end "L" type formwork 9 with bolts, and semicircular stirrup reserved holes are arranged; that is, the corresponding external buckle bolt holes and embedded bolt holes between the plates are connected by bolts.

[0047] like Figure 9 As shown: the inner wall foldable formwork 8 rotates around the axis. In order to prevent the foldable formwork from being difficult to rotate after the concrete solidifies, the outer wall of the formwork is designed to be flat and the inner wall is designed to be arc-shaped to ensure the folding function of the inner wall foldable formwork when the formwork is removed.

[0048] like Figure 8 As shown: the horizontal plate of the end "L"-shaped template 9 is arranged with circular longitudinal steel bar reserved holes, and the vertical plate is arranged with semicircular stirrup reserved holes; the vertical plate is arranged with embedded bolt holes, and the horizontal plate is arranged with external buckle bolt holes. The vertical plate and the horizontal plate are respectively connected to the inner wall folding template 8 and the side plate 10 with bolts, and the bottom is arranged with external buckle bolt holes, which are connected to the bottom plate 11 with bolts.

[0049] The modular formwork is split into several small formworks. The joints between the formworks are not completely aligned with the edges of the "concave" structure, which makes it easy to assemble the formworks in a complex reinforcement space. After the formworks are assembled, no external formwork structure is required and the formworks are easy to dismantle.

[0050] like Figure 10 As shown, after the top beam interface is cast, the solidified concrete can be used as the outer formwork for the post-cast tie rod part, and the post-cast tie rod part can be constructed using conventional steel formwork.

[0051] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A prestressed U-shaped aqueduct and post-cast tie rod connection structure, characterized by: The interface between the reserved joint (2) of the aqueduct top beam (1) and the post-cast tie rod (3) adopts a "concave-convex" mortise and tenon structure. The reserved joint (2) and the aqueduct body are integrally cast and formed. The end of the reserved joint (2) is designed to be "concave", and the end of the post-cast tie rod (3) is designed to be "convex". The internal reinforcement of the reserved joint (2) is extended outward, and the extended reinforcement is embedded in the post-cast tie rod (3); The modular template of the reserved joint (2) comprises a recessed flat template (7), two inner wall folding templates (8), two end "L" templates (9), two side panels (10) and a bottom panel (11); Rebar reserved holes are provided on the concave flat template (7), the inner wall folding template (8) and the end "L" template (9); The concave flat template (7) and the first folding plates of the inner wall folding templates (8) on both sides together form a "concave" shaped groove bottom template; the second folding plate of the inner wall folding template (8) and the vertical plate of the end "L"-shaped template (9) form a "concave" shaped groove wall template; the horizontal plate of the end "L"-shaped template (9) serves as the end template of the reserved joint (2); the side plate (10) serves as the side template of the reserved joint (2); and the bottom plate (11) serves as the bottom template of the reserved joint (2); The recessed flat template (7), the inner wall folding template (8), the end "L" template (9), the side panels (10) and the bottom panel (11) are detachably connected to form a combined template. The side panels (10) and the bottom panel (11) are detachably connected to the template of the aqueduct body.

2. The prestressed U-shaped aqueduct and post-cast tie rod connection structure according to claim 1, characterized in that: The "concave" groove on the reserved joint (2) is vertical; a row of longitudinal stress-bearing steel bars (4) are arranged at the top and bottom of the reserved joint (2), respectively, and frame steel bars (5) and stirrups (6) are arranged in coordination; the frame steel bars (5) are arranged in two rows along the vertical direction, and the two rows of frame steel bars (5) are aligned with the longitudinal stress-bearing steel bars (4) at the head and tail of the row, respectively, and the stirrups (6) are circumferentially clamped outside the frame steel bars (5) and the longitudinal stress-bearing steel bars (4), and at least one transverse stress-bearing steel bar is arranged in the "concave" groove.

3. The prestressed U-shaped aqueduct and post-cast tie rod connection structure according to claim 1, characterized in that: The top and bottom of the recessed flat template (7) each have a row of longitudinal reinforcement holes, including semicircular holes at the template joints and circular holes passing through the template; External buckle bolt holes are arranged on both sides of the recessed flat template (7), which can be connected to the inner wall folding template (8) using bolts; and external buckle bolt holes are arranged on the bottom, which can be connected to the bottom plate (11) using bolts.

4. The prestressed U-shaped aqueduct and post-cast tie rod connection structure according to claim 3, characterized in that: The inner wall folding template (8) is composed of two flat templates connected by a rotating shaft. Both flat templates can be freely rotated, folded, and unfolded around the shaft. The first folding plate of the inner wall folding template (8) is provided with embedded bolt holes, and the second folding plate is provided with external buckle bolt holes. The first folding plate is connected to the flat template (7) at the recessed portion by bolts, and semicircular longitudinal reinforcement holes are arranged. The second folding plate is connected to the end "L"-shaped template (9) by bolts, and semicircular stirrup reinforcement holes are arranged.

5. The prestressed U-shaped aqueduct and post-cast tie rod connection structure according to claim 4, characterized in that: The horizontal plate of the end "L" type template (9) is provided with circular longitudinal reinforcement holes, and the vertical plate is provided with semicircular stirrup reinforcement holes; the vertical plate is provided with embedded bolt holes, and the horizontal plate is provided with external buckle bolt holes. The vertical plate and the horizontal plate are respectively connected to the inner wall folding template (8) and the side plate (10) using bolts, and the bottom is provided with external buckle bolt holes, which are connected to the bottom plate (11) using bolts.

6. The prestressed U-shaped aqueduct and post-cast tie rod connection structure according to claim 1, characterized in that: The post-casting tie rod (3) is locally widened at the "concave-convex" interface.

7. The prestressed U-shaped aqueduct and post-cast tie rod connection structure according to claim 2, characterized in that: The extension length of the erection steel bars (5) and the longitudinal stress-bearing steel bars (4) is 220 mm.

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