Prefabricated UHPC beam column joint variable cross-section non-dismantling formwork connecting structure and mounting method

Abstract

The invention discloses a prefabricated UHPC beam-column joint variable cross-section non-dismantling formwork connecting structure and an installation method, mechanical connection between beam-column non-dismantling formworks is provided through a conversion connecting piece, and joint positioning precision and construction efficiency are guaranteed; steel bars in the prefabricated UHPC U-shaped beam non-dismantling formwork and a node area form a continuous force transmission path, the ductility and the anti-seismic property of the node are improved, smooth transition of the column section from a circle to a square outside the node can be achieved, and the adaptability of the formwork is improved; the prefabricated UHPC column non-dismantling formwork and the conversion connecting piece are integrally prefabricated and formed, field processing and reinforcing are reduced, and the construction industrialization level is improved; the whole structure can meet the design requirements of shearing resistance, tensile resistance and bending resistance, and the mechanical property and durability of the beam-column joint of the frame structure are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of high-performance materials and prefabricated structures, specifically to a prefabricated UHPC beam-column joint variable cross-section formwork-free connection structure and installation method, which is suitable for the rapid assembly and integrated construction of prefabricated building frame joints. Background Technology

[0002] Currently, prefabricated concrete structures are increasingly widely used in civil engineering, especially ultra-high performance concrete (UHPC) in beam-column joints, which can significantly improve the load-bearing capacity and durability of structures. However, existing beam-column joint connection methods in prefabricated concrete frame structures mainly rely on wet joint pouring or simple rebar lap splicing and reinforcement. Traditional wet joint joint construction involves many procedures and long cycles, and is prone to shrinkage cracks and weak joints; while simple rebar lap splicing or temporary reinforcements cannot provide sufficient stiffness and positioning accuracy during the assembly stage; moreover, the lack of standardized mechanical connection methods between beam and column formwork makes beam-column joints prone to misalignment or displacement during construction, affecting the quality of subsequent concrete pouring. In addition, the installation and removal of formwork at beam-column joints are difficult, especially when the column cross-section and joint cross-section are inconsistent, often requiring custom-made formwork, increasing construction difficulty and time. Therefore, there is an urgent need for a UHPC beam-column joint formwork-free connection structure that combines the functions of formwork-free installation, reliable load-bearing performance, and ease of assembly to improve joint construction efficiency and overall structural durability. Summary of the Invention

[0003] The purpose of this invention is to provide a precast UHPC beam-column joint variable cross-section formwork-free connection structure and installation method, which solves the problems of unreliable formwork connection, abrupt change in joint cross-section, discontinuous stress path and complex construction in formwork-free joint connections.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A precast UHPC beam-column joint variable cross-section formwork connection structure includes a precast UHPC column formwork that can be removed, a transition connector, a precast UHPC U-shaped beam formwork that can be removed, and an L-shaped formwork assembly component; The prefabricated UHPC column template includes a column clear height area and a node area fixed on the column clear height area. The conversion connector is set on the node area of ​​the prefabricated UHPC column template. The precast UHPC U-shaped beam formwork is installed at the node area of ​​the precast UHPC column formwork; the L-shaped formwork assembly is fixed to the outside of the precast UHPC U-shaped beam formwork.

[0005] Preferably, the node area of ​​the precast UHPC column template is provided with a U-shaped groove matching the shape of the precast UHPC U-shaped beam template at the beam overlap position, and the depth of the U-shaped groove extends to the upper surface of the conversion connector; the inner surface of the node area of ​​the precast UHPC column template is provided with a mesh-like keyway; the outer contour of the conversion connector is a square with a protrusion in the middle on the plane, and the inner contour is a circle with a diameter equal to the inner diameter of the column clear height area of ​​the precast UHPC column template, and the side length of the outer contour square is equal to the outer diameter of the column clear height area.

[0006] Preferably, the conversion connector has reinforcing bars welded downward into the net height area of ​​the precast UHPC column formwork at the middle of its four sides, i.e., at the position where the outer circle and the square are tangent; the conversion connector has reinforcing bars welded upward into the node area of ​​the precast UHPC column formwork at its four corners.

[0007] Preferably, the conversion connector is provided with several welded steel bars inside and pre-embedded in the prefabricated UHPC column template that does not require disassembly.

[0008] Preferably, the precast UHPC U-shaped beam formwork includes a bottom formwork and a side formwork, and several small-diameter steel bars are respectively arranged in the bottom formwork and the side formwork. The ends of the small-diameter steel bars extend into the beam-column joint and are welded or lapped with the reinforcement in the column.

[0009] Preferably, the spacing between the steel plates formed by the L-shaped template assembly in the vertical and horizontal directions is equal to the thickness of the prefabricated UHPC U-shaped beam template that can be disassembled, and its vertical height is not less than 1 / 2 of the height of the beam side formwork.

[0010] Preferably, the conversion connector has horizontally protruding steel plates and vertically protruding steel plates with holes punched at the bottom and sides of the U-shaped groove, respectively; the width of the horizontally protruding steel plate is equal to the effective width of the bottom formwork of the beam; and the height of the vertically protruding steel plate is equal to the height of the side formwork of the beam.

[0011] Preferably, the horizontal and vertical extended steel plates are provided with through holes at their extended ends, corresponding to the reserved holes of the prefabricated UHPC U-shaped beam template. The through holes are aligned with the corresponding reserved holes of the prefabricated UHPC U-shaped beam template and are connected and fixed by bolts.

[0012] Preferably, the L-shaped template assembly has holes in the vertical and horizontal directions that are compatible with the through holes and reserved holes. The L-shaped template assembly is fixed to the bottom formwork and side formwork of the beam by bolt fasteners, and fixed to the conversion connector at the beam-column joint.

[0013] An installation method for a precast UHPC beam-column joint variable cross-section formwork-free connection structure includes the following steps: The prefabricated UHPC column formwork that does not need to be removed and the pre-embedded conversion connectors are hoisted into place as a whole; Insert the prefabricated UHPC U-shaped beam formwork into the U-shaped groove in the node area, align the reserved holes of the beam formwork with the through holes of the conversion connector, and use bolts to fasten through the holes, and tighten with washers and nuts to achieve mechanical fixation of the beam and column formwork; L-shaped formwork components are installed at the beam ends and mid-span of the beam. The beam formwork assembly is further reinforced with bolts. After assembly, the formwork can be used directly as structural formwork without disassembly.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a prefabricated UHPC beam-column joint variable cross-section formwork connection structure that eliminates the need for formwork removal. A conversion connector provides a mechanical connection between the beam and column formwork, ensuring accurate joint positioning and efficient construction. The internal reinforcement of the prefabricated UHPC U-shaped beam formwork forms a continuous force transmission path with the joint area, improving joint ductility and seismic performance. It also enables a smooth transition from a circular column cross-section to a square outer section, enhancing formwork adaptability. The prefabricated UHPC column formwork and conversion connector are prefabricated as a whole, reducing on-site processing and reinforcement, and improving the level of industrialization in construction. The overall structure meets shear, tensile, and bending design requirements, ensuring the mechanical performance and durability of the beam-column joint in the frame structure. Attached Figure Description

[0015] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a prefabricated UHPC beam-column joint variable cross-section formwork connection structure provided by the present invention.

[0017] Figure 2 This is a schematic diagram of the connection structure of the conversion connector in an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the installation of the conversion connector structure in an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of the conversion connector structure in an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram of the column clear height area structure in an embodiment of the present invention.

[0021] Figure 6 This is a schematic diagram of the L-shaped template assembly structure in an embodiment of the present invention.

[0022] Figure 7 This is a schematic diagram of the prefabricated UHPC U-shaped beam template-free structure in an embodiment of the present invention.

[0023] Figure 8 This is a schematic diagram of the beam side formwork structure in an embodiment of the present invention.

[0024] Figure 9 This is a schematic diagram of the prefabricated UHPC U-shaped beam installation structure without disassembly template in an embodiment of the present invention.

[0025] In the diagram: 1. Precast UHPC column formwork (no removal required); 2. Transition connector; 3. Precast UHPC U-beam formwork (no removal required); 4. L-shaped formwork assembly; 5. Bolt fasteners; 111. Column clear height area; 12. Node area; 121. U-shaped groove; 122. Mesh keyway; 21. Horizontal protruding steel plate; 22. Vertical protruding steel plate; 23. Through hole; 31. Reserved hole; 32. Beam bottom formwork; 33. Beam side formwork; 34. Small diameter reinforcing bar. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] like Figures 1-9As shown, a prefabricated UHPC beam-column joint variable cross-section formwork connection structure includes a prefabricated UHPC column formwork 1, a conversion connector 2, a prefabricated UHPC U-shaped beam formwork 3, an L-shaped formwork assembly 4, and bolt fasteners 5. The prefabricated UHPC column formwork 1 includes a column clear height area 11 and a joint area 12. The column clear height area 11 of the prefabricated UHPC column formwork 1 is annular, and the joint area 12 is an inner circle and an outer square, and the inner diameters of the column clear height area 11 and the joint area 12 are the same. The conversion connector 2 is located at the boundary between the column clear height area 11 and the joint area 12. The prefabricated UHPC U-shaped beam formwork 3 has a U-shaped cross-section and is connected to the joint area 12 of the prefabricated UHPC column formwork 1. The L-shaped formwork assembly 4 has an open L-shaped cross-section and is located on the outside of the prefabricated UHPC U-shaped beam formwork 3.

[0029] The node area 12 of the precast UHPC column template 1, at the overlap position with the beam, has a U-shaped groove 121 that matches the shape of the precast UHPC U-shaped beam template 3. The depth of the U-shaped groove 121 extends to the upper surface of the conversion connector 2. The inner surface of the node area 12 of the precast UHPC column template 1 has a textured keyway 122, forming a rough surface. Figure 2 As shown, the conversion connector 2 is made of steel plate. The outer contour of the conversion connector 2 is an outer square with a protrusion in the middle on the plane. The inner contour is a circle with a diameter equal to the inner diameter of the net height area 11 of the prefabricated UHPC column template 1. The side length of the outer square is equal to the outer diameter of the net height area 11 of the column. The conversion connector 2 has reinforcing bars welded downwards into the column clear height area 11 of the precast UHPC column template 1 at the middle of its four sides, i.e., at the position where the outer circle is tangent to the square. The conversion connector 2 also has reinforcing bars welded upwards into the node area 12 of the precast UHPC column template 1 at its four corners. The conversion connector 2 and the precast UHPC column template 1 are integrally formed as a precast unit and pre-embedded inside the precast UHPC column template 1, maintaining a fixed relative position between them.

[0030] The material of the conversion connector 2 can be a conventional steel plate, and several welded steel bars inside are pre-embedded in the prefabricated UHPC column template 1. After the template is poured, it is wrapped by UHPC to achieve overall operation.

[0031] The precast UHPC U-shaped beam formwork 3 includes a bottom formwork 32 and a side formwork 33. Several small-diameter steel bars 34 are respectively arranged in the bottom formwork 32 and the side formwork 33. The ends of the small-diameter steel bars 34 extend into the beam-column joint and are welded or lapped with the reinforcement in the column.

[0032] The conversion connector 2 has a horizontally protruding steel plate 21 and a vertically protruding steel plate 22 with holes punched at the bottom and sides of the U-shaped slot 121, respectively; the width of the horizontally protruding steel plate 21 is equal to the effective width of the bottom formwork 32 of the beam; the height of the vertically protruding steel plate 22 is equal to the height of the side formwork 33 of the beam.

[0033] The L-shaped template assembly 4 is welded from conventional steel plates and is used for assembling the bottom formwork 32 and the side formwork 33 of the beam. It is arranged at the beam end and the middle of the beam span. The spacing formed by the steel plates of the L-shaped template assembly 4 in the vertical and horizontal directions is the thickness of the prefabricated UHPC U-shaped beam non-removable template 3, and its vertical height is not less than 1 / 2 of the height of the side formwork 33 of the beam.

[0034] The horizontally extending steel plate 21 and the vertically extending steel plate 22 are provided with through holes 23 at their extended ends, corresponding to the reserved holes 31 of the prefabricated UHPC U-shaped beam template 3. The through holes 23 are aligned with the corresponding reserved holes 31 of the prefabricated UHPC U-shaped beam template 3 and are connected and fixed by bolts and fasteners 5, so that the prefabricated UHPC U-shaped beam template 3 is reliably fixed to the conversion connector 2 in the overlapping state.

[0035] The L-shaped template assembly 4 has holes in the vertical and horizontal directions that are compatible with the through hole 23 and the reserved hole 31. The L-shaped template assembly 4 is fixed to the bottom formwork 32 and the side formwork 33 of the beam by bolt fasteners 5, and fixed to the conversion connector 2 at the beam-column joint.

[0036] The bolt fastener 5 is a high-strength bolt, and washers and nuts are provided at the connection to achieve clamping. The hole positions and bolt specifications are configured according to the load-bearing requirements, so that the connection has certain mechanical properties.

[0037] The arrangement of the slot 121 on the side of the node area 12 of the precast UHPC column template 1 allows the precast UHPC U-beam template 3 to be accurately positioned, and the geometric dimensions of the slot 121 are matched with the protruding part of the conversion connector 2 to ensure the accuracy of the assembly position.

[0038] The through holes 23 at the protruding parts of the horizontal steel plate 21 and the vertical steel plate 22 of the conversion connector 2 can be arranged as a group of multiple holes so that multiple bolts can be used to connect or adjust the connection position according to different beam widths or beam heights.

[0039] The prefabricated UHPC column formwork 1 with its variable cross-section in the node area 11 allows the outer part of the node area 11 to be square so that the beams can overlap laterally, while the column clear height area 12 returns to a circular cross-section. This achieves the variable cross-section requirement of the column at the node and takes into account the convenience of formwork processing and installation.

[0040] like Figures 2-4 As shown, the precast UHPC column formwork 1 is made of ultra-high performance concrete (UHPC), possessing excellent forming accuracy and durability. Its column clear height area 11 has a circular cross-section, while the node area 12 has a square outer cross-section with an inner circle, the same inner diameter as the column clear height area 11, and a square outer edge to facilitate beam overlap. A U-shaped slot 121 is provided on the side of the node area 12, extending to the upper surface of the transition connector 2, its dimensions designed to properly accommodate the precast UHPC U-shaped beam formwork 3. The inner surface of the node area 12 has a textured keyway 122, forming a rough surface to enhance bonding performance with the core concrete. The circular cross-section of the column clear height area meets the column's appearance and load-bearing requirements; the square outer cross-section of the beam-column node area ensures effective integration with the column's main reinforcement and concrete core area, while providing the square outer edge required for beam overlap, thus achieving a natural transition of the column cross-section.

[0041] like Figure 3 As shown, the conversion connector 2 is made of conventional steel plate and serves as the core component for node connection. Its internal outline is circular, with a diameter equal to the inner diameter of the column clear height zone 11; its external outline is square, with a side length equal to the outer diameter of the column clear height zone 11, and it has a protruding portion at the beam overlap position. The conversion connector 2 is pre-embedded inside the precast UHPC column formwork 1, integrally formed with the column formwork. At the center of the four sides of the conversion connector 2, i.e., where the outer circle and square are tangent, reinforcing bars extending downwards into the column clear height zone 11 are welded; reinforcing bars extending upwards into the node area 12 are welded at the four corners to ensure the continuity of force transmission. The conversion connector 2 has a horizontally extending steel plate 21 at the bottom of the U-shaped groove 121 and vertically extending steel plates 22 on both sides. The width of the horizontally extending steel plate 21 is equal to the effective width of the beam bottom formwork 32, and the height of the vertically extending steel plate 22 is equal to the height of the beam side formwork 33. Through holes 23 are provided at the ends of the extending steel plates for bolt connection. By welding downward reinforcing bars to the center of the four sides of the conversion connector and upward reinforcing bars to the four corners, it can be reliably anchored to the net height area of ​​the precast UHPC column formwork and the node area, respectively, ensuring the continuity of force transmission.

[0042] like Figures 6-9As shown, the precast UHPC U-shaped beam formwork 3 is made of UHPC with a U-shaped cross-section, including a bottom formwork 32 and a side formwork 33. Several small-diameter steel bars 35 are arranged inside the beam formwork, with the ends of the bars extending into the beam-column joint and welded or lapped with the column reinforcement to form a continuous stress path. The beam formwork has pre-reserved holes 31, aligned with the through holes 23 of the conversion connector 2, and fixed by bolts 5. The precast UHPC U-shaped beam formwork is equipped with steel bars, the ends of which extend into the joint area, forming a continuous stress path with the column reinforcement, thereby improving the joint ductility and overall load-bearing capacity. The number, spacing, and anchorage length of the small-diameter steel bars inside the precast UHPC U-shaped beam formwork should be set according to the stress conditions of the joint, serving to strengthen the joint without changing the original mechanical design.

[0043] The L-shaped formwork assembly has different holes depending on its installation position. Precast UHPC U-shaped beam formwork is assembled using bolts and fasteners. At the beam ends, i.e., beam-column joints, some holes align with the through holes of the transition connectors, enhancing the connection between the precast UHPC U-shaped beam formwork and the transition connectors. The L-shaped formwork assembly changes the typical method of integral molding for rectangular cross-section beam formwork, modularizing the precast components. By prefabricating plates of specific dimensions for the beam bottom and side molds, precast UHPC U-shaped beam formwork of different sizes can be formed, meeting various structural designs and achieving standardization and modularization of component prefabrication.

[0044] The U-shaped slots on the sides of the node area mate with the conversion connectors. The conversion connectors have horizontally extending steel plates at the bottom of the U-shaped slot and vertically extending steel plates on both sides of the U-shaped slot. Through holes are formed at the ends of both, aligning with pre-drilled holes on the precast UHPC U-shaped beam formwork. Bolts are then tightened to secure the connection, enabling mechanized and rapid connection of the beam-column formwork. This design ensures accurate positioning of the precast UHPC U-shaped beam formwork and provides reliable shear and tensile strength.

[0045] The thickness of the steel plate, the welding method, and the diameter and anchorage length of the welded reinforcing bars of the conversion connector should be determined according to the design internal forces of the node in accordance with the specifications and engineering requirements to meet the strength and deformation requirements for shear, tension and bending resistance.

[0046] This invention creates a continuous stress path through a step-by-step transition from "circular column clear height area—inner circle and outer square node area—transition connector—prefabricated UHPC U-shaped beam formwork that does not require removal," thus avoiding problems such as stress concentration at the nodes. Simultaneously, the bolted connection method and the fact that the formwork does not need to be removed after pouring standardize and mechanize the beam and column assembly process, significantly improving construction efficiency.

[0047] The following is the assembly process of the prefabricated UHPC beam-column joint variable cross-section formwork connection structure of the present invention: First, the prefabricated UHPC column formwork 1 and the pre-embedded conversion connector 2 are hoisted into place as a whole; then, the prefabricated UHPC U-shaped beam formwork 3 is inserted into the U-shaped groove 121 of the joint area 12, aligning the reserved hole 31 of the beam formwork with the through hole 23 of the conversion connector 2, and high-strength bolts 5 are passed through the holes and tightened with washers and nuts to achieve mechanical fixation of the beam-column formwork; finally, L-shaped formwork assembly parts 4 are installed at the beam ends and mid-span of the beam, and the beam formwork assembly is further reinforced with bolts. After assembly, the formwork can be used directly as structural formwork and does not need to be removed after concrete pouring, forming an integral structure.

[0048] The above embodiments are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A precast UHPC beam-column joint variable cross-section formwork-free connection structure, characterized in that, Includes precast UHPC column formwork (1), conversion connector (2), precast UHPC U-beam formwork (3) and L-shaped formwork assembly (4); The prefabricated UHPC column template (1) includes a column clear height area (11) and a node area (12) fixed on the column clear height area (11). The conversion connector (2) is set on the node area (12) of the prefabricated UHPC column template (1). The precast UHPC U-beam formwork (3) is set at the node area (12) of the precast UHPC column formwork (1); the L-shaped formwork assembly (4) is fixed to the outside of the precast UHPC U-beam formwork (3).

2. The precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 1, characterized in that, The node area (12) of the prefabricated UHPC column template (1) is provided with a U-shaped groove (121) that matches the shape of the prefabricated UHPC U-shaped beam template (3) at the beam overlap position. The depth of the U-shaped groove (121) extends to the upper surface of the conversion connector (2). The inner surface of the node area (12) of the prefabricated UHPC column template (1) is provided with a mesh-like keyway (122). The outer contour of the conversion connector (2) is an outer square with a protrusion in the middle on the plane. The inner contour is a circle with a diameter equal to the inner diameter of the column clear height area (11) of the prefabricated UHPC column template (1). The side length of the outer contour square is equal to the outer diameter of the column clear height area (11).

3. The precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 1, characterized in that, The conversion connector (2) has steel bars welded to the middle of its four sides, i.e., at the position where the outer circle and the square are tangent, respectively, the column clear height area (11) of the precast UHPC column template (1) extending downward; the conversion connector (2) has steel bars welded to the four corners, respectively, the node area (12) of the precast UHPC column template (1) extending upward.

4. The precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 1, characterized in that, The conversion connector (2) has several welded steel bars inside and is embedded in the precast UHPC column template (1).

5. A precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 4, characterized in that, The precast UHPC U-shaped beam formwork (3) includes a bottom formwork (32) and a side formwork (33), and several small-diameter steel bars (34) are respectively arranged in the bottom formwork (32) and the side formwork (33). The ends of the small-diameter steel bars (34) extend into the beam-column joint and are welded or lapped with the reinforcement in the column.

6. A precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 5, characterized in that, The spacing between the steel plates formed by the L-shaped template assembly (4) in the vertical and horizontal directions is the thickness of the prefabricated UHPC U-shaped beam template (3) without disassembly, and its height in the vertical direction is not less than (1) / (2) of the height of the beam side formwork (33).

7. The precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 1, characterized in that, The conversion connector (2) has a horizontally extending steel plate (21) and a vertically extending steel plate (22) with holes punched at the bottom and sides of the U-shaped slot (121), respectively; the width of the horizontally extending steel plate (21) is equal to the effective width of the bottom formwork (32) of the beam; the height of the vertically extending steel plate (22) is equal to the height of the side formwork (33) of the beam.

8. A precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 1, characterized in that, The horizontally extending steel plate (21) and the vertically extending steel plate (22) are provided with through holes (23) at their extended ends, which correspond to the reserved holes (31) of the prefabricated UHPC U-shaped beam template (3). The through holes (23) are aligned with the corresponding reserved holes (31) of the prefabricated UHPC U-shaped beam template (3) and are connected and fixed by bolt fasteners (5).

9. A precast UHPC beam-column joint variable cross-section formwork-free connection structure according to claim 1, characterized in that, The L-shaped template assembly (4) has holes in the vertical and horizontal directions that are compatible with the through hole (23) and the reserved hole (31). The L-shaped template assembly (4) is fixed to the bottom formwork (32) and the side formwork (33) of the beam by bolt fasteners (5), and fixed to the conversion connector (2) at the beam-column node.

10. An installation method for a precast UHPC beam-column joint variable cross-section formwork-free connection structure, characterized in that, Includes the following steps: The prefabricated UHPC column formwork (1) and the pre-embedded conversion connector (2) are hoisted into place as a whole; Insert the prefabricated UHPC U-shaped beam template (3) into the U-shaped groove (121) of the node area (12), so that the reserved hole (31) of the beam template is aligned with the through hole (23) of the conversion connector (2), and use bolt fasteners (5) to pass through the hole and tighten with washers and nuts to achieve mechanical fixation of the beam and column template; L-shaped formwork assembly (4) is installed at the beam end and mid-span of the beam. The beam formwork assembly is further reinforced by bolts. After assembly, the formwork can be used directly as structural formwork without disassembly.

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