Fe-SMA bar-reinforced UHPC precast formwork shell reinforcement structure and method for pier

Abstract

Disclosed in the present invention are an Fe-SMA bar-reinforced UHPC precast formwork shell reinforcement structure and method for a pier. The reinforcement structure comprises a wedge-shaped steel plate hoop, a shear-resistant precast formwork shell and a bend-resistant precast formwork shell, wherein the wedge-shaped steel plate hoop is fixedly mounted outside a pier body without damage and is located on the top of a pier section to be reinforced of the pier body to be reinforced, and a bearing platform is integrally provided at the bottom end of the pier body. In the present invention, a U-shaped steel plate hoop and a double-slope wedge-shaped steel plate form a self-locking structure under the action of high-strength screws, and the double-slope wedge-shaped steel plate generates a large compressive stress in the concrete at a constraint position, such that an original structure is not damaged while a relatively stable anchoring capability is provided. The pre-stress generated by Fe-SMA bars configured inside the precast formwork shell can effectively improve many aspects of the performance of the precast formwork shell, such as crack resistance, bearing and durability, and can realize rapid repair and reinforcement work for the pier body, thereby greatly improving the reinforcement efficiency of pier members. The on-site construction is simple and convenient, and the reinforcement construction process is significantly improved.

Description

Reinforcement Structure and Method of UHPC Precast Formwork with Fe-SMA Reinforcement for Pier Columns Technical Field

[0001] This invention belongs to the field of prestressed reinforcement technology for concrete structures, specifically relating to the reinforcement structure and method of UHPC precast mold shell reinforced with Fe-SMA reinforcement for pier columns. Background Technology

[0002] Ultra-high performance concrete (UHPC) is a high-performance engineering material with remarkable characteristics such as high strength, high toughness, and low permeability. However, the tensile properties and ductility of UHPC are highly dependent on reinforcing materials such as steel fibers. Without the addition of fibers, its tensile strength and crack resistance will decrease significantly. After UHPC cracks, harmful substances from the outside can penetrate through the cracks, causing corrosion of the internal steel fibers or reinforcing bars, thereby weakening the structural performance.

[0003] Iron-based shape memory alloy (Fe-SMA) is a functional material with superelasticity and shape memory effect. Its inherent shape memory effect allows Fe-SMA, even with residual deformation, to actively recover its original state after high-temperature excitation and cooling. When Fe-SMA is used to create various types of reinforcing bars and installed in concrete components, prestress is generated in the structure during the high-temperature excitation and cooling process, constrained by anchoring devices and concrete.

[0004] Prestressed reinforcement technology, due to its high tensile strength, places high demands on its anchoring devices. For the protection of pier structures (including earthquake-damaged piers and those requiring reinforcement), traditional anchoring typically uses bolts to fix the anchoring devices to the pier components, but this inevitably causes secondary damage to the pier components. Furthermore, traditional prestressed reinforcement technology is difficult to implement on-site and cumbersome, significantly impacting the reinforcement process. Precast formwork formed by the combination of Fe-SMA reinforcement and UHPC can reinforce pier components. However, when Fe-SMA reinforcement is subjected to high tensile force, the requirements for the anchoring ends are high, and the electrical excitation of Fe-SMA on-site is a significant workload.

[0005] Therefore, in view of the limitations of the prior art, the present invention develops a reinforcement structure and method for UHPC precast mold shell reinforced with Fe-SMA reinforcement for pier columns. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a Fe-SMA bar reinforced UHPC precast formwork reinforcement structure and method for pier columns in view of the above deficiencies of the prior art. By utilizing the self-locking structure characteristic of the wedge-shaped steel plate hoop under force, the advantages of UHPC in high crack resistance and excellent durability, and the merit of Fe-SMA in no prestress friction loss, the efficiency during the reinforcement process of pier column members is greatly improved.

[0007] Technical Solution: To achieve the above inventive purpose, the technical solution adopted by the present invention is as follows:

[0008] The Fe-SMA bar reinforced UHPC precast formwork reinforcement structure for pier columns includes a wedge-shaped steel plate hoop, shear-resistant precast formworks and flexural-resistant precast formworks, wherein the wedge-shaped steel plate hoop is fixedly installed on the outer side of the pier column body to be reinforced without damage, and is located at the top of the to-be-reinforced section of the pier column on the pier column body. A bearing platform is integrally arranged at the bottom end of the pier column body, and anchoring holes are opened on the upper surface of the bearing platform at positions corresponding to the to-be-reinforced section of the pier column.

[0009] The wedge-shaped steel plate hoop comprises a double-slope wedge-shaped steel plate and two groups of U-shaped steel plate hoops. Each group is provided with two U-shaped steel plate hoops, and the two U-shaped steel plate hoops in the same group are symmetrically distributed and combined into a "mouth"-shaped sleeve member through connecting screw rods. The two "mouth"-shaped sleeve members are respectively sleeved on the two outer ends of the double-slope wedge-shaped steel plate. The U-shaped steel plate hoop is provided with bolt holes for connecting the Fe-SMA bars of the precast formwork, and high-strength screw rods are jointly connected in the corresponding bolt holes on the two "mouth"-shaped sleeve members.

[0010] Both the shear-resistant precast formwork and the flexural-resistant precast formwork comprise Fe-SMA bars and a UHPC formwork. The UHPC formwork wraps the outer side of the overlapped Fe-SMA bars, and both end portions of the Fe-SMA bars extend out of the UHPC formwork and are respectively connected with the bearing platform and the U-shaped steel plate hoop.

[0011] The end portions of two adjacent shear-resistant precast formworks and flexural-resistant precast formworks are attached to each other and distributed perpendicularly. A plurality of shear-resistant precast formworks and flexural-resistant precast formworks are arranged alternately around the outer side of the pier column body, forming a gap outside the to-be-reinforced section of the pier column for grouting filling.

[0012] Preferably, the two "mouth"-shaped sleeve members are symmetrically distributed about the central cross section of the double-slope wedge-shaped steel plate, the inner side surface of the U-shaped steel plate hoop is set as a 30° inclined surface, both outer end surfaces of the double-slope wedge-shaped steel plate are provided with 30° symmetrically distributed slopes, the U-shaped steel plate hoop is closely attached to the outer slope surface of the double-slope wedge-shaped steel plate, and the length of the slope surface is greater than the length of the inner inclined surface of the U-shaped steel plate hoop.

[0013] Two sets of U-shaped steel plate hoops are combined with high-strength screws and connecting screws to form an adjustable structure. When the high-strength screws and connecting screws are tightened, a squeezing effect is generated between the double-slope wedge-shaped steel plate and the "U"-shaped sleeve.

[0014] Preferably, the connecting screw includes a bidirectional screw, and a prism torsion block is fixedly connected to the outer side of the middle part of the bidirectional screw. Both ends of the U-shaped steel plate hoop are provided with internal threaded holes, and the two opposite internal threaded holes of the same set of U-shaped steel plate hoops are respectively threaded to both ends of the bidirectional screw.

[0015] Preferably, the Fe-SMA ribs are stretched into an X-shaped, Y-shaped, or mesh-like cross structure, and the Fe-SMA ribs extend vertically from the ends of the UHPC mold shell, with external thread sections provided at their ends.

[0016] Preferably, the portion of the Fe-SMA rib extending from the top of the UHPC mold shell passes through the corresponding bolt holes on the two "U"-shaped sockets and is locked by the first nut that is threaded on the outer side of the external thread section.

[0017] Each of the high-strength screws has a second nut threaded onto its outer end, and the sum of the number of the first nut and the second nut is equal to the number of bolt holes opened on a "U"-shaped socket. The high-strength screws are spaced apart between multiple external thread segments.

[0018] Preferably, the section of the pier to be reinforced forms a surrounding groove-like structure on the outside of the pier body, and the number of Fe-SMA reinforcements extending out of the bottom end of the UHPC mold shell matches the number of anchor holes, and they are inserted into multiple anchor holes one by one, and fixed to the foundation by rebar adhesive.

[0019] Preferably, the double-slope wedge-shaped steel plate is pre-fixed to the pier body with strong adhesive, and the double-slope wedge-shaped steel plate is installed 100mm above the section of the pier to be reinforced.

[0020] The reinforcement method for UHPC precast formwork reinforced with Fe-SMA reinforcement for pier columns involves the following steps:

[0021] S1. Processing prefabricated components: Based on the design dimensions of the pier to be reinforced and the area of ​​the section to be reinforced, process and manufacture prefabricated components including shear-resistant prefabricated formwork, bending-resistant prefabricated formwork, double-slope wedge steel plates, U-shaped steel plate hoops, high-strength bolts and connecting bolts.

[0022] S2. Treatment of the pier body: The surface area of ​​the section of the pier to be reinforced on the pier body to be reinforced is broken concrete, the damaged concrete layer on the outside is removed and finely repaired to form a surrounding groove structure. A tool is used to drill holes on the outside of the connection between the pier body and the foundation. After cleaning the debris, multiple anchor holes are formed around the pier. The diameter of the Fe-SMA reinforcement is db, and the depth of the anchor hole (8) is ≥15db.

[0023] S3. Laying out shear-resistant precast formwork and bending precast formwork: Multiple shear-resistant precast formwork and bending precast formwork are set up alternately. After injecting anchoring adhesive into the anchoring holes, the extensions of the Fe-SMA bars reserved at the bottom of the shear-resistant precast formwork and bending precast formwork are inserted into the anchoring holes one by one.

[0024] S4. Assemble the wedge-shaped steel plate hoop: Use strong adhesive to temporarily attach the double-slope wedge-shaped steel plate to the outside of the pier body and 100mm above the section of the pier to be reinforced. Combine the two sets of U-shaped steel plate hoops into two "U"-shaped connectors by connecting bolts, and slide them into the double-slope wedge-shaped steel plate from both ends. Insert the extensions of the Fe-SMA reinforcements reserved at the top of the shear precast formwork and the bending precast formwork into the bolt holes on the U-shaped steel plate hoop. Tighten the connecting bolts to make the U-shaped steel plate hoop fit tightly against the double-slope wedge-shaped steel plate. Then use high-strength bolts to connect the two "U"-shaped connectors securely to form the wedge-shaped steel plate hoop. Lock the shear precast formwork and the bending precast formwork to the outside of the section of the pier to be reinforced.

[0025] S5. Applying force: Twist the second nut on the outside of the high-strength screw and tighten it. The two "U"-shaped sockets are brought close to each other and tightened, so that the U-shaped steel plate hoop and the double-slope wedge steel plate are squeezed together. After the anchoring adhesive has solidified and the Fe-SMA bar and the anchor hole have a certain strength, turn the first nut on the external thread section to tighten the Fe-SMA bar and connect it with the wedge steel plate hoop to apply tension.

[0026] S7. Grouting: Multiple shear-resistant precast molds and bending precast molds are tightly fitted together at their edges, and their bottoms are tightly fitted to the pier cap. Side panels are added to the outside of their tops. Grout is injected into the gaps between the shear-resistant precast molds, bending precast molds, and the outer wall of the section of the pier to be reinforced through reserved channels. After the grout solidifies, the grouting section is formed. The side panels are then removed to complete the reinforcement of the pier body.

[0027] Preferably, in S1, during the processing of the double-slope wedge steel plate and the U-shaped steel plate hoop, the 30° slope on the inner side of the U-shaped steel plate hoop and the 30° slope on the outer side of the double-slope wedge steel plate are both laser-cut.

[0028] During the processing of shear-resistant and bending-resistant precast mold shells, the Fe-SMA ribs are stretched to the predetermined strain and threads are machined on the extension section at the top. After bending, they are placed into the precast mold shell of the UHPC mold shell for casting. After natural curing for 1-3 days, they are placed in a high-temperature oven for high-temperature curing for 1-2 days, and then the precast mold shell is taken out.

[0029] Preferably, the self-prestress of the Fe-SMA reinforcement is activated by dry heat curing in a high-temperature oven during the initial stage of UHPC mold curing.

[0030] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0031] 1. By adopting the Fe-SMA-UHPC combined structure, utilizing the self-locking structure formed by the wedge-shaped steel plate hoop under stress, the high crack resistance and excellent durability of UHPC, and the advantage of Fe-SMA without prestress friction loss, the double-slope wedge-shaped steel plate generates large compressive stress in the concrete at the constraint point. While providing relatively stable anchoring capacity, it does not cause damage to the original structure. The prestress generated by the Fe-SMA reinforcement inside the precast formwork can effectively improve the crack resistance, load-bearing capacity, and durability of the precast formwork. It can realize the rapid repair and reinforcement of the pier column body, greatly improving the efficiency of the pier column reinforcement process. In addition, it can also be used for the repair and reinforcement of other building structures.

[0032] 2. By combining prefabricated shear-resistant and bending-resistant prefabricated formwork, the internal Fe-SMA arrangement is a cross-composite structure, which can better limit the generation and propagation of diagonal cracks under cyclic loads; the use of high-temperature curing prefabricated formwork improves the performance of UHPC while stimulating Fe-SMA reinforcement, effectively controlling the recovery stress of Fe-SMA reinforcement and improving the construction efficiency on site.

[0033] 3. By using prefabricated components to treat the pier body; processing the section of the pier to be reinforced and drilling holes at the pier cap; setting up shear-resistant and bending-resistant prefabricated molds; assembling wedge-shaped steel plate hoops; applying force; and grouting, the construction process is simplified by fixing the prefabricated molds with anchoring adhesive while ensuring connection strength. Compared with traditional prestressed reinforcement technology, on-site construction is simple and convenient, significantly promoting the reinforcement process of the pier. Attached Figure Description

[0034] Figure 1 is an overall effect diagram of the UHPC precast shell reinforcement structure for pier columns reinforced with Fe-SMA reinforcement disclosed in this invention.

[0035] Figure 2 is a diagram showing the processing effect of the section of the pier to be reinforced in this invention.

[0036] Figure 3 is a perspective view of the wedge-shaped steel plate hoop structure in this invention.

[0037] Figure 4 is a schematic diagram of the shear-resistant precast mold shell or bending-resistant precast mold shell structure in this invention.

[0038] Figure 5 is a schematic diagram of the stress on the double-slope wedge steel plate and U-shaped steel plate hoop structure in this invention.

[0039] In the picture:

[0040] 1. Pier body; 2. Pier cap; 3. Wedge-shaped steel plate hoop; 4. Shear-resistant precast formwork; 5. Bending-resistant precast formwork; 6. Grouting section; 7. Pier section to be reinforced; 8. Anchor hole; 9. Double-slope wedge-shaped steel plate; 10. U-shaped steel plate hoop; 11. High-strength bolt; 12. Connecting bolt; 13. Bolt hole; 14. UHPC formwork; 15. Fe-SMA reinforcement. Detailed Implementation

[0041] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., 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. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0043] As shown in Figures 1-5, the pier column is reinforced with Fe-SMA reinforcement UHPC precast mold shell, which includes wedge-shaped steel plate hoop 3, shear-resistant precast mold shell 4 and bending-resistant precast mold shell 5. The wedge-shaped steel plate hoop 3 is fixedly installed on the outside of the pier column body 1 to be reinforced without damage, and is located at the top of the pier column body 1 to be reinforced section 7. The bottom end of the pier column body 1 is integrally provided with a bearing platform 2, and the upper surface of the bearing platform 2 is provided with anchoring holes 8 at the position corresponding to the pier column to be reinforced section 7.

[0044] Shear-resistant precast formwork 4 and bending-resistant precast formwork 5 adopt ultra-high performance concrete (UHPC) formwork with built-in iron-based shape memory alloy (Fe-SMA) reinforcement.

[0045] The wedge-shaped steel plate hoop 3 comprises a double-slope wedge-shaped steel plate 9 and two sets of U-shaped steel plate hoops 10. Each set of U-shaped steel plate hoops 10 is provided with two pieces, and the two U-shaped steel plate hoops 10 in the same set are axially symmetrically distributed and combined into a "mouth"-shaped socket piece through the connecting screw member 12. The two "mouth"-shaped socket pieces are respectively sleeved on the two outer ends of the double-slope wedge-shaped steel plate 9. The U-shaped steel plate hoop 10 is provided with bolt holes 13 for connecting the Fe-SMA rebars 15 of the prefabricated formwork, and the corresponding bolt holes 13 on the two "mouth"-shaped socket pieces are jointly connected with a high-strength screw 11.

[0046] Under the action of the high-strength screw 11, the U-shaped steel plate hoop 10 and the double-slope wedge-shaped steel plate 9 form a self-locking structure, and the double-slope wedge-shaped steel plate 9 generates a large compressive stress on the concrete at the restraint position, which provides relatively stable anchoring capacity without causing damage to the original structure.

[0047] Both the shear-resistant prefabricated formwork 4 and the bending-resistant prefabricated formwork 5 comprise Fe-SMA rebars 15 and a UHPC formwork 14. The UHPC formwork 14 wraps the outer side of the overlapped Fe-SMA rebars 15, and both end portions on two sides of the Fe-SMA rebar 15 extend out of the UHPC formwork 14 and are connected with the bearing platform 2 and the U-shaped steel plate hoop 10 respectively.

[0048] The end portions of two adjacent shear-resistant prefabricated formworks 4 and bending-resistant prefabricated formworks 5 are attached to each other and distributed perpendicularly. A plurality of shear-resistant prefabricated formworks 4 and bending-resistant prefabricated formworks 5 are alternately arranged around the outer side of the pier column body 1, forming a gap on the outer side of the to-be-reinforced section 7 of the pier column for grouting filling.

[0049] Further, in the above technical solution, the two "mouth"-shaped socket pieces are axially symmetrically distributed about the central cross section of the double-slope wedge-shaped steel plate 9, the inner side surface of the U-shaped steel plate hoop 10 is set as a 30° inclined surface, both ends of the outer side surface of the double-slope wedge-shaped steel plate 9 are provided with 30° inclined slopes distributed axially symmetrically, the U-shaped steel plate hoop 10 is tightly attached to the outer inclined slope surface of the double-slope wedge-shaped steel plate 9, and the length of the inclined slope surface is greater than the length of the inner inclined surface of the U-shaped steel plate hoop 10.

[0050] The two sets of U-shaped steel plate hoops 10 are combined to form an adjustable structure through the high-strength screw 11 and the connecting screw member 12. When the high-strength screw 11 and the connecting screw member 12 are tightened, an extrusion effect is generated between the double-slope wedge-shaped steel plate 9 and the "mouth"-shaped socket piece, that is, an extrusion force is generated between the double-slope wedge-shaped steel plate 9 and the U-shaped steel plate hoop 10 by tightening the high-strength screw 11, and the force mechanism is shown in Figure 5.

[0051] Further, in the above technical solution, the connecting screw member 12 includes a bidirectional screw rod, the outer side of the middle portion of the bidirectional screw rod is fixedly connected with a prismatic torsion block, both ends of the U-shaped steel plate hoop 10 are provided with inner threaded holes, and the two opposite inner threaded holes of the U-shaped steel plate hoops 10 in the same set are respectively in threaded fit with both ends of the bidirectional screw rod.

[0052] Furthermore, in the above technical solution, the Fe-SMA reinforcement 15 is stretched into a cross structure. In specific embodiments, the cross structure can be set as an X-shape, Y-shape, or mesh structure. Specifically, its arrangement direction is approximately perpendicular to the direction of the diagonal crack in the pier body 1, which can better reduce the width of the initial diagonal crack. This arrangement of the cross structure increases the contact area between the Fe-SMA reinforcement 15 and the UHPC mold shell 14, resulting in higher strength after casting. It can withstand lateral shear force while providing bending bearing capacity. The Fe-SMA reinforcement 15 extends vertically from the ends of the UHPC mold shell 14, and its ends are provided with external threaded sections.

[0053] Furthermore, in the above technical solution, the portion of the Fe-SMA rib 15 extending out of the top of the UHPC mold shell 14 passes through the corresponding bolt holes 13 on the two "U"-shaped sockets and is locked by the first nut that is threaded on the outer side of the external thread section.

[0054] Each high-strength screw 11 has a second nut threaded onto its outer end, and the sum of the number of the first nut and the second nut is equal to the number of bolt holes 13 opened on a "U"-shaped socket. Multiple high-strength screws 11 are spaced apart between multiple external thread sections.

[0055] Furthermore, in the above technical solution, the section 7 to be reinforced of the pier column forms a surrounding groove-like structure on the outside of the pier column body 1. The number of Fe-SMA reinforcements 15 extending out of the bottom end of the UHPC mold shell 14 matches the number of anchor holes 8, and they are inserted into multiple anchor holes 8 one by one, and fixed to the foundation 2 by rebar adhesive.

[0056] Furthermore, in the above technical solution, the double-slope wedge steel plate 9 is pre-fixed to the pier body 1 with strong adhesive, and the double-slope wedge steel plate 9 is installed 100mm above the section 7 of the pier to be reinforced, to prevent the concrete from being crushed under the large pressure of the wedge steel plate hoop 3.

[0057] The reinforcement method for UHPC precast formwork reinforced with Fe-SMA reinforcement for pier columns involves the following steps:

[0058] S1. Processing prefabricated components: Based on the design dimensions of the pier body 1 to be reinforced and the area of ​​the section 7 to be reinforced, process and manufacture prefabricated components including shear-resistant prefabricated mold shell 4, bending-resistant prefabricated mold shell 5, double-slope wedge steel plate 9, U-shaped steel plate hoop 10, high-strength bolt 11 and connecting bolt 12.

[0059] Specifically, during the processing of the double-slope wedge steel plate 9 and the U-shaped steel plate hoop 10, the 30° slope on the inner side of the U-shaped steel plate hoop 10 and the 30° slope on the outer side of the double-slope wedge steel plate 9 are both laser-cut.

[0060] During the processing of the shear-resistant precast mold shell 4 and the bending-resistant precast mold shell 5, the Fe-SMA rib 15 is stretched to the predetermined strain and threads are machined on the extension section at its top. After bending, it is placed into the precast mold shell of the UHPC mold shell 14 for casting. The casting material is UHPC material with good fluidity.

[0061] After natural curing for 1-3 days, place it in a high-temperature oven for high-temperature curing for 1-2 days, and then remove the precast mold shell.

[0062] Specifically, the curing temperature is related to the prestressing design of Fe-SMA rib 15 and should be set according to the specific engineering application.

[0063] The self-prestress of Fe-SMA rib 15 is activated by dry heat curing in a high-temperature oven during the early stage of curing UHPC mold shell 14. The dry heat curing process activates the built-in Fe-SMA rib to generate recovery stress, thereby applying prestress to the UHPC mold shell.

[0064] S2. Treatment of pier body 1: On the surface area of ​​the section 7 of the pier body 1 to be reinforced, the concrete is broken, the damaged concrete layer on the outside is removed and finely repaired to form a surrounding groove structure. At the connection between the pier body 1 and the abutment 2, a hole is drilled on the outside, and after cleaning the debris, multiple anchoring holes 8 are formed in a surrounding distribution. The diameter of the Fe-SMA reinforcement 15 is db, and the depth of the anchoring hole 8 is ≥15db.

[0065] S3. Install shear precast formwork 4 and bending precast formwork 5: Multiple shear precast formwork 4 and bending precast formwork 5 are set alternately. After injecting anchoring adhesive into the anchoring hole 8, the extensions of the Fe-SMA reinforcement 15 reserved at the bottom of the shear precast formwork 4 and bending precast formwork 5 are inserted into the anchoring hole 8 one by one.

[0066] S4. Assemble the wedge-shaped steel plate hoop 3: Use strong adhesive to temporarily attach the double-slope wedge-shaped steel plate 9 to the outside of the pier body 1 and 100mm above the section 7 to be reinforced. Combine the two sets of U-shaped steel plate hoops 10 into two "U"-shaped connectors through the connecting screws 12, and slide them into the double-slope wedge-shaped steel plate 9 from both ends. Insert the extensions of the Fe-SMA reinforcement 15 reserved at the top of the shear precast formwork 4 and the bending precast formwork 5 into the bolt holes 13 on the U-shaped steel plate hoop 10 one by one. Tighten the connecting screws 12 to make the U-shaped steel plate hoop 10 fit tightly against the double-slope wedge-shaped steel plate 9. Then use high-strength screws 11 to connect the two "U"-shaped connectors securely to form the wedge-shaped steel plate hoop 3, and lock the shear precast formwork 4 and the bending precast formwork 5 to the outside of the section 7 to be reinforced.

[0067] S5. Applying force: Twist the second nut on the outside of the high-strength screw 11 and tighten it. The two "U"-shaped sockets approach each other and tighten, so that the U-shaped steel plate hoop 10 and the double-slope wedge steel plate 9 are squeezed together. After the anchoring adhesive has solidified and the Fe-SMA bar 15 and the anchoring hole 8 have a certain strength, turn the first nut on the external thread section to tighten the Fe-SMA bar 15 and connect it with the wedge steel plate hoop 3 to apply tension.

[0068] S7. Grouting: Multiple shear-resistant precast molds 4 and bending-resistant precast molds 5 are tightly fitted together at their edges, and their bottoms are tightly fitted to the foundation 2. Side panels are added to the outer side of their tops. Grout is injected into the gaps between the shear-resistant precast molds 4, bending-resistant precast molds 5, and the outer wall of the pier column to be reinforced 7 through reserved channels. After solidification, the grouting section 6 is formed. The side panels are then removed to complete the reinforcement of the pier column.

[0069] The Fe-SMA self-prestressing technology fully utilizes the self-locking mechanism of the wedge structure and the advantages of UHPC's high strength, high crack resistance, and high durability to form an ultra-thin UHPC-Fe-SMA composite precast shell. Compared with traditional reinforcement methods, the precast shell formed by this technology has a certain strength itself, and the presence of the precast shell avoids the need for internal grouting template support.

[0070] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A Fe-SMA tendon reinforced UHPC precast formwork for strengthening structures of columns, characterized in that: comprising a wedge-shaped steel plate hoop (3), a shear-resistant prefabricated formwork shell (4) and a bending-resistant prefabricated formwork shell (5), wherein the wedge-shaped steel plate hoop (3) is fixedly installed on the outer side of the pier column body (1) to be reinforced without damage, and is located at the top of the pier column section (7) to be reinforced on the pier column body (1); the bottom end of the pier column body (1) is integrally provided with a bearing platform (2), and an anchorage hole (8) is opened on the upper surface of the bearing platform (2) at the position corresponding to the pier column section (7) to be reinforced; the wedge-shaped steel plate hoop (3) comprises a double-slope wedge-shaped steel plate (9) and two sets of U-shaped steel plate hoops (10); each set of U-shaped steel plate hoops (10) is provided with two pieces, and the two U-shaped steel plate hoops (10) in the same set are symmetrically distributed in an axisymmetric manner, and are combined into a "mouth"-shaped socket piece through a connecting screw rod piece (12); the two "mouth"-shaped socket pieces are respectively sleeved on the two outer ends of the double-slope wedge-shaped steel plate (9); the U-shaped steel plate hoop (10) is provided with bolt holes (13) for connecting the Fe-SMA rebars (15) of the prefabricated formwork shell, and high-strength screws (11) are jointly connected in the corresponding bolt holes (13) on the two "mouth"-shaped socket pieces; both the shear-resistant prefabricated formwork shell (4) and the bending-resistant prefabricated formwork shell (5) comprise Fe-SMA rebars (15) and a UHPC formwork shell (14); the UHPC formwork shell (14) wraps the outer side of the overlapped Fe-SMA rebars (15), and both end portions of the Fe-SMA rebars (15) extend out of the UHPC formwork shell (14), and are connected with the bearing platform (2) and the U-shaped steel plate hoop (10) respectively; the end portions of two adjacent shear-resistant prefabricated formwork shells (4) and bending-resistant prefabricated formwork shells (5) are attached to each other and distributed perpendicularly; a plurality of shear-resistant prefabricated formwork shells (4) and bending-resistant prefabricated formwork shells (5) are arranged alternately around the outer side of the pier column body (1), forming a gap outside the pier column section (7) to be reinforced for grouting filling.

2. The Fe-SMA tendon reinforced UHPC prefabricated formwork structure for columns according to claim 1, characterized in that: the two "mouth"-shaped socket pieces are distributed axisymmetrically about the central cross section of the double-slope wedge-shaped steel plate (9); the inner side surface of the U-shaped steel plate hoop (10) is set as a 30° inclined surface, and both outer end faces of the double-slope wedge-shaped steel plate (9) are provided with 30° inclined slopes distributed axisymmetrically; the U-shaped steel plate hoop (10) is closely attached to the outer slope surface of the double-slope wedge-shaped steel plate (9), and the length of the slope surface is greater than the length of the inner inclined surface of the U-shaped steel plate hoop (10); the two sets of U-shaped steel plate hoops (10) are combined into an adjustable structure through the high-strength screws (11) and the connecting screw rod pieces (12); when the high-strength screws (11) and the connecting screw rod pieces (12) are tightened, a squeezing effect is generated between the double-slope wedge-shaped steel plate (9) and the "mouth"-shaped socket pieces.

3. The Fe-SMA tendon reinforced UHPC prefabricated formwork structure for column according to claim 1, characterized in that: the connecting screw rod piece (12) comprises a bidirectional screw rod; the outer side of the middle part of the bidirectional screw rod is fixedly connected with a prismatic torsion block; both ends of the U-shaped steel plate hoop (10) are provided with inner threaded holes, and the two opposite inner threaded holes of the U-shaped steel plate hoops (10) in the same set are respectively in threaded fit with the two ends of the bidirectional screw rod.

4. The Fe-SMA tendon reinforced UHPC prefabricated formwork structure for columns according to claim 1, characterized in that: the Fe-SMA rebars (15) are stretched into an X-shaped, Y-shaped or meshed cross structure; the end portions of the Fe-SMA rebars (15) extending out of the UHPC formwork shell (14) are distributed vertically, and the end portions thereof are provided with external thread sections.

5. The Fe-SMA tendon-reinforced UHPC prefabricated formwork structure for columns according to claim 4, characterized in that: The portion of the Fe-SMA rib (15) extending beyond the top end of the UHPC formwork (14) passes through the corresponding bolt holes (13) on two "mouth"-shaped sockets, and is locked by the first nut threadedly sleeved on the outer side of the external thread section; The outer end of each high-strength screw rod (11) is threadedly sleeved with a second nut, and the sum of the number of the first nuts and the second nuts is equal to the number of bolt holes (13) opened on one "mouth"-shaped socket. A plurality of the high-strength screw rods (11) are arranged at intervals between the plurality of external thread sections.

6. The Fe-SMA tendon reinforced UHPC prefabricated formwork structure for columns according to claim 4, characterized in that: The to-be-strengthened section (7) of the pier column forms a surrounding groove-like structure on the outer side of the pier column body (1). The number of portions of the Fe-SMA rib (15) extending beyond the bottom end of the UHPC formwork (14) matches the number of the anchorage holes (8), and they are inserted into the plurality of anchorage holes (8) in one-to-one correspondence, and are fixed to the bearing platform (2) by means of rebar planting adhesive.

7. The Fe-SMA tendon reinforced UHPC prefabricated formwork structure for columns according to claim 1, characterized in that: The double-slope wedge-shaped steel plate (9) and the pier column body (1) are pre-fixed by strong adhesive, and the double-slope wedge-shaped steel plate (9) is installed at a position 100mm above the to-be-strengthened section (7) of the pier column.

8. A method for reinforcing a UHPC prefabricated formwork for piers with Fe-SMA bars, based on the structure for reinforcing a UHPC prefabricated formwork for piers with Fe-SMA bars according to any one of claims 1 to 7, characterized in that: Specifically comprising the following steps: S1. Processing and prefabricating assembly parts: According to the design dimension of the pier column body (1) to be strengthened and the regional area of the to-be-strengthened section (7) of the pier column, prefabricated parts including a shear-resistant prefabricated formwork (4), a bending-resistant prefabricated formwork (5), a double-slope wedge-shaped steel plate (9), a U-shaped steel plate hoop (10), a high-strength screw rod (11) and a connecting screw member (12) are processed and manufactured; S2. Treatment of the pier body (1): On the surface area of ​​the section (7) of the pier body (1) to be reinforced, the concrete is broken, the damaged concrete layer on the outside is removed and finely repaired to form a surrounding groove structure. At the connection between the pier body (1) and the abutment (2), a hole is drilled on the outside. After cleaning the debris, multiple anchor holes (8) are formed around the pier body. The diameter of the Fe-SMA reinforcement (15) is d. b Anchor hole (8) depth ≥ 15d b ; S3. Arranging the shear-resistant prefabricated formwork (4) and the bending-resistant prefabricated formwork (5): A plurality of the shear-resistant prefabricated formworks (4) and the bending-resistant prefabricated formworks (5) are arranged alternately. After the rebar planting adhesive is injected into the anchorage holes (8), the extended sections of the Fe-SMA ribs (15) reserved at the bottoms of the shear-resistant prefabricated formworks (4) and the bending-resistant prefabricated formworks (5) are inserted into the anchorage holes (8) in one-to-one correspondence; S4. Assembling the wedge-shaped steel plate hoop (3): The double-slope wedge-shaped steel plate (9) is temporarily adhered to the outer side of the pier column body (1) at a position 100mm above the to-be-strengthened section (7) of the pier column by using strong adhesive. Two sets of U-shaped steel plate hoops (10) are combined into two "mouth"-shaped sockets via the connecting screw members (12), and are correspondingly slid in from both ends of the double-slope wedge-shaped steel plate (9), so that the extended sections of the Fe-SMA ribs (15) reserved at the tops of the shear-resistant prefabricated formworks (4) and the bending-resistant prefabricated formworks (5) are inserted into the bolt holes (13) on the U-shaped steel plate hoops (10) in one-to-one correspondence. The connecting screw members (12) are tightened to make the U-shaped steel plate hoops (10) closely fit the double-slope wedge-shaped steel plate (9). Then the two "mouth"-shaped sockets are firmly connected by the high-strength screw rods (11) to form the wedge-shaped steel plate hoop (3), and the shear-resistant prefabricated formworks (4) and the bending-resistant prefabricated formworks (5) are locked outside the to-be-strengthened section (7) of the pier column; S5. Applying force: Twist the second nut on the outside of the high-strength screw (11) and tighten it. The two "U"-shaped sockets approach each other and tighten, so that the U-shaped steel plate hoop (10) and the double-slope wedge steel plate (9) are squeezed together. After the anchoring adhesive has solidified and the Fe-SMA bar (15) and the anchor hole (8) have a certain strength, rotate the first nut on the external thread section to tighten the Fe-SMA bar (15) and connect it with the wedge steel plate hoop (3) to apply tension. S7. Grouting: The edges of multiple shear precast molds (4) and bending precast molds (5) are tightly fitted together, and their bottoms are tightly fitted with the foundation (2). Side panels are added to the outside of their tops. Grout is injected into the gap between the shear precast molds (4), bending precast molds (5) and the outer wall of the section to be reinforced (7) of the pier column through the reserved holes. After solidification, the grouting section (6) is formed. The side panels are removed to complete the reinforcement of the pier column body.

9. The method of reinforcing a UHPC precast formwork with Fe-SMA tendon for a pier column according to claim 8, characterized in that: In S1, when processing the double-slope wedge steel plate (9) and the U-shaped steel plate hoop (10), the 30° slope on the inner side of the U-shaped steel plate hoop (10) and the 30° slope on the outer side of the double-slope wedge steel plate (9) are both laser-cut. During the processing of the shear-resistant precast mold (4) and the bending precast mold (5), the Fe-SMA rib (15) is stretched to the predetermined strain and threaded on the extension section at its top. After bending, it is placed into the precast mold of the UHPC mold (14) for casting. After natural curing for 1-3 days, it is placed in a high-temperature oven for high-temperature curing for 1-2 days, and then the precast mold is taken out.

10. The method of reinforcing a UHPC precast formwork with Fe-SMA tendon for a pier column according to claim 9, characterized in that: The self-prestress of the Fe-SMA rib (15) is activated by dry heat curing in a high-temperature oven during the initial curing stage of the UHPC mold shell (14).

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