A combined single-column pier of UHPC tube - SFRRC - GFRP bars and construction method

Abstract

The present invention discloses a combined single-column pier of UHPC tube - SFRRC - GFRP bars and a construction method thereof, belonging to the technical field of bridge structures. It includes a bearing platform, on which embedded steel bars are provided. A steel reinforcement cage is fixed on the embedded steel bars. A number of coaxial steel pipe columns that are fixedly connected to each other are sleeved on the steel reinforcement cage. Prefabricated UHPC pipe segments are sleeved on the outer sides of the steel pipe columns, and adjacent prefabricated UHPC pipe segments are bonded by epoxy resin; SFRRC concrete is poured inside the steel pipe columns, and ordinary concrete is poured between the steel pipe columns and the prefabricated UHPC pipe segments; both the embedded steel bars and the steel reinforcement cage adopt GFRP bars. The present invention uses steel fiber recycled concrete (SFRRC), glass fiber reinforced polymer (GFRP) bars, and prefabricated UHPC pipe segments to form a brand-new single-column pier, which has excellent bearing capacity, corrosion resistance, durability, economic environmental protection performance.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge structures, and particularly relates to a combined single-column pier of UHPC pipes - SFRRC - GFRP bars and a construction method thereof. Background Technique

[0002] With the development of China's construction industry and urban planning, the quantity of waste concrete generated from the demolition of a large number of old buildings, bridges, etc. is increasing. Recycling and processing waste concrete and crushing it into aggregates with different particle sizes as raw materials for recycled concrete can achieve green recycling and reuse of resources. As early as the 1970s, scholars began to study the utilization of waste concrete. After removing the steel bars from waste concrete and crushing it, coarse aggregates with different particle sizes can be obtained, and part or all of them can replace the coarse aggregates of concrete. However, defects such as naturally occurring cracks in recycled concrete affect its popularization and application in actual projects. Through certain research, scholars found that incorporating steel fibers into recycled concrete can effectively improve its mechanical properties and meet the requirements of engineering applications.

[0003] For reinforced concrete structures, when the concrete cracks, the steel bars are exposed to the environment and are extremely prone to steel bar corrosion and failure, resulting in a decrease in the bearing capacity of the structure. Scholars use continuous fibers as the reinforcement and polymer resin as the matrix, and through a series of processes, a new composite material is prepared to form fiber-reinforced composite bars. Among them, the bars prepared with glass fibers as the reinforcement material have the characteristics of light weight, high strength, high corrosion resistance, high cost performance, etc., and when their performance degrades due to environmental effects, the impact is mild. In contrast, when ordinary steel bars corrode, the volume expansion caused by the corrosion products will cause the concrete to crack and reduce the bearing capacity of the structure. Therefore, it can reasonably replace ordinary concrete.

[0004] As a crucial support structure of a bridge, the safety performance of a single-column pier is self-evident. Therefore, the invention adopts steel fiber recycled concrete (SFRRC), glass fiber reinforced polymer (GFRP) bars, and ultra-high performance concrete (UHPC) precast pipe segments to form a brand-new single-column pier, which has excellent bearing capacity, corrosion resistance, durability, and economic environmental protection. Summary of the Invention

[0005] In view of this, the present invention discloses a combined single-column pier of UHPC tube - SFRRC - GFRP bars and a construction method thereof. Steel fiber recycled concrete SFRRC, glass fiber reinforced composite material GFRP steel bars, and ultra-high performance concrete precast UHPC tube segments are used to form a brand-new single-column pier. This combined single-column pier has excellent bearing capacity, corrosion resistance, durability, economic and environmental friendliness.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A combined single-column pier of UHPC tube - SFRRC - GFRP bars includes a bearing platform. Embedded steel bars are arranged on the bearing platform. A steel cage is fixed on the embedded steel bars. A plurality of coaxial steel pipe columns that are fixedly connected to each other are sleeved in the steel cage. Prefabricated UHPC tube segments are sleeved outside each of the steel pipe columns. Adjacent prefabricated UHPC tube segments are bonded by epoxy resin. SFRRC concrete is poured inside the steel pipe columns. Ordinary concrete is poured between the steel pipe columns and the prefabricated UHPC tube segments. Both the embedded steel bars and the steel cage adopt GFRP steel bars.

[0008] The present invention uses steel fiber recycled concrete SFRRC, glass fiber reinforced composite material GFRP steel bars, and ultra-high performance concrete precast UHPC tube segments to form a brand-new single-column pier. This combined single-column pier has excellent bearing capacity, corrosion resistance, durability, economic and environmental friendliness. In addition, the steel pipe columns provide circumferential restraint for the SFRRC concrete in the core area, enhancing the overall bearing capacity of the structure. While the steel pipe columns and the ordinary concrete provide circumferential restraint for the steel pipe columns, they also concentrate the damaged area in this part, which is beneficial for subsequent maintenance and replacement.

[0009] Furthermore, an annular support frame is arranged on the circumferential side of the steel pipe column. The support frame includes a plurality of support components. Adjacent support components are detachably connected by a connection structure. The support component includes a plurality of inner arc bars that fit the outer wall of the steel pipe column. A plurality of connecting rods that deviate from the center of the steel pipe column are fixed on each of the inner arc bars. Horizontally adjacent connecting rods are fixedly connected by an outer arc bar that has the same center as the inner arc bar. The end of the connecting rod is threadedly connected with a coaxial adjusting rod. An arc-shaped pressing block is arranged at the end of the adjusting rod. A plurality of groups of positioning protrusions for clamping the inner arc bars are arranged on the outer wall of the steel pipe column. Vertical rods are fixed between vertically adjacent inner arc bars and between vertically adjacent outer arc bars.

[0010] In this solution, after the steel pipe column is installed, the support components are successively engaged with the positioning protrusions, and the support components are preliminarily installed on the steel pipe column. The adjacent support components are connected by a connecting structure to form an annular support frame. Then, the first precast UHPC pipe segment is hoisted onto the bearing platform. Only by rotating the adjusting rod, the abutting block at the end of the adjusting rod is made to abut against the inner wall of the precast UHPC pipe segment, and the positioning and installation of the precast UHPC pipe segment are completed. There is no need to additionally erect a truss for support, which can effectively shorten the construction process and save construction time.

[0011] Furthermore, the connecting structure includes a hollow support rod. Both sides of the support rod are communicated with arc-shaped and hollow connecting sections that are communicated with the corresponding inner arc rod and outer arc rod. An arc-shaped positioning section is slidably connected in each connecting section. An elastic resetting member is arranged between the positioning section and the connecting section. A chute is opened at one end of the positioning section facing the support rod. A push rod is slidably connected in the chute. One end of the push rod extends into the support rod, and an elastic support member is arranged between the other end of the push rod and the chute. A plurality of through grooves communicated with the chute are opened on the circumferential side of the end of the positioning section away from the support rod. A limiting block is slidably connected in each through groove, and the same elastic resetting member is arranged between the limiting block and the through groove. A plurality of limiting grooves matched with the limiting blocks are opened on the inner walls at both ends of the inner arc rod and the outer arc rod. A coaxial screw rod is rotatably connected in the support rod. Two pushing blocks threadedly connected with the screw rod are slidably connected inside the support rod. The end face of the pushing block facing the center of the steel pipe column is inclined.

[0012] In this solution, after the support components are preliminarily installed on the steel pipe column, the connecting structure is installed at the gap between adjacent support components. By rotating the screw rod, the pushing block is driven to move towards the steel pipe column. The pushing block drives the positioning section to slide into the corresponding inner arc rod and outer arc rod by squeezing the push rod. When the positioning section moves to the limit position, the push rod squeezes the elastic resetting member and continues to move until the push rod squeezes and pushes the limiting block into the limiting groove, locking the connection of adjacent support components. When it is necessary to demolish the ordinary concrete area, the precast UHPC pipe segment of the corresponding section is knocked out to expose the support rod. By reversely rotating the screw rod, the pushing block is driven to reset. The push rod moves reversely under the action of the elastic support member and no longer squeezes the limiting block. The limiting block slides into the positioning section under the action of the elastic resetting member and releases the connection between the positioning section and the corresponding inner arc rod and outer arc rod. The positioning section also slides into the connecting section under the action of the elastic resetting member, releasing the connection between the support components, so as to facilitate the demolition of the ordinary concrete.

[0013] Furthermore, it also includes a precast replacement section made of UHPC. The precast replacement section is an arc-shaped structure symmetrically arranged left and right. Adjacent precast replacement sections are bonded by epoxy resin. Through holes facing the connecting rod are arranged on the precast replacement section.

[0014] Further, a plugging block is detachably connected to the end of the support rod, and the connection part is treated without bonding.

[0015] Further, the mass mix proportion of the SFRRC concrete is 75 parts of recycled concrete, 20 parts of Class I fly ash, 0.5 part of FN-H high-range water reducer, 1 part of shear-end hooked steel fiber, and 28.5 parts of P.O42.5 ordinary Portland cement; the mass mix proportion of the recycled concrete is 50% of recycled coarse aggregate and 50% of natural sand and gravel, and the recycled coarse aggregate is formed by crushing, cleaning, grading, and mixing waste concrete blocks.

[0016] A construction method for a combined single-column pier of UHPC pipe - SFRRC - GFRP bars, characterized by comprising the following steps:

[0017] Step 1: Clean the top surface of the bearing platform, level it according to the design elevation, clean the embedded steel bars made of GFRP and weld and fix the GFRP steel bar cage to the embedded steel bars according to the specification requirements; hoist the bottom steel pipe column and weld it to the steel bar cage; sequentially engage the support components with the positioning protrusions, initially install the support components on the steel pipe column, and then install the connection structure at the gap between adjacent support components; drive the pushing block to move towards the steel pipe column by rotating the screw rod, the pushing block drives the positioning section to slide into the corresponding inner arc rod and outer arc rod through the extrusion push rod, when the positioning section moves to the limit position, the push rod extrudes the elastic resetting member and continues to move until the push rod extrudes and pushes the limiting block into the limiting groove to connect and lock the adjacent support components to form a support frame, and the connection structure is treated without bonding;

[0018] Step 2: Hoist the first - stage precast UHPC pipe segment onto the bearing platform, and by rotating the adjusting rod, make the abutting block at the end of the adjusting rod abut against the inner wall of the precast UHPC pipe segment to complete the positioning and installation of the precast UHPC pipe segment, and use UHPC mortar to connect the bearing platform and the first - stage precast UHPC pipe segment, and then pour SFRRC concrete into the steel pipe column; then pour ordinary concrete between the steel pipe column and the precast UHPC pipe segment;

[0019] Step 3: After waiting for the SFRRC concrete and the ordinary concrete at the bottom segment to reach final setting and a certain strength, weld the steel bar cage of the second segment and the second - stage steel pipe column; then install the support frame, and position and hoist the second - stage precast UHPC pipe segment, and use epoxy resin mortar for bonding to prevent corrosion and leakage of slurry;

[0020] Step 4: For the installation of the third and subsequent segments, repeat Step 3 for installation;

[0021] Step 5: Pour ordinary concrete in one go from the topmost steel pipe column, and pour SFRRC concrete in one go from the topmost precast UHPC pipe segment. Each pouring cycle needs to be carried out in three segments; the pouring height in the final stage should be controlled according to the elevation of the bottom surface of the pier cap, and the surface should be roughened before the SFRRC concrete and ordinary concrete in the core set.

[0022] Step 6: When the precast UHPC pipe segment and the ordinary concrete area in a certain segment are damaged or cracked, knock out the precast UHPC pipe segment of the corresponding segment to expose the support rod. Drive the pushing block to reset by rotating the screw in the reverse direction. The ejector rod moves in the reverse direction under the action of the elastic support member and no longer presses the limiting block. The limiting block slides into the positioning section under the action of the elastic resetting member and releases the connection between the positioning section and the corresponding inner arc rod and outer arc rod. The positioning section also slides into the connection section under the action of the elastic resetting member to release the connection between the support components, so as to facilitate the removal of the ordinary concrete.

[0023] Step 7: Weld or repair the positioning protrusions, reinstall the self-supporting frame, and screw out the adjusting rod on the support frame. Lift and install the precast replacement segment so that the through holes on the precast replacement segment are aligned with the connecting rods. Bond the adjacent precast replacement segments with epoxy resin; then screw the adjusting rod into the through hole so that the pressing block fits against the outer wall of the precast replacement segment to play a role in positioning, supporting and fixing; then re-pour the ordinary concrete.

[0024] Other advantages, objectives and features of the present invention will be described in the subsequent specification, and to some extent will be obvious to those skilled in the art, or those skilled in the art can obtain teachings from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the objectives, technical solutions and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0026] Figure 1 It is a schematic structural diagram of the installation of the precast UHPC pipe segment in the embodiment of the present invention;

[0027] Figure 2 It is Figure 1 a horizontal cross-sectional view of

[0028] Figure 3 It is Figure 2 an enlarged schematic view of part A in

[0029] Figure 4 It is a schematic structural diagram of the installation of the precast replacement pipe segment in the embodiment of the present invention.

[0030] The markings in the accompanying drawings are as follows: cap 1, steel cage 2, steel pipe column 3, prefabricated UHPC pipe segment 4, inner arc rod 5, outer arc rod 6, vertical rod 7, connecting rod 8, tightening block 9, adjusting rod 10, positioning protrusion 11, support rod 12, connecting section 13, positioning section 14, top rod 15, elastic support member 16, limit block 17, elastic reset member 18, screw 19, push block 20, prefabricated replacement section 21. DETAILED DESCRIPTION

[0031] like Figures 1 to 4 As shown: a combined single-column pier of UHPC tube-SFRRC-GFRP bars, comprising a cap 1, on which embedded steel bars are arranged, on which a steel cage 2 is fixed, and on which a plurality of mutually fixed and coaxial steel pipe columns 3 are sleeved, on the outer sides of the steel pipe columns 3, prefabricated UHPC tube segments 4 are sleeved, and adjacent prefabricated UHPC tube segments 4 are bonded by epoxy resin; SFRRC concrete is poured inside the steel pipe column 3, and ordinary concrete is poured between the steel pipe column 3 and the prefabricated UHPC tube segments 4; the embedded steel bars and the steel cage 2 are both made of GFRP steel bars.

[0032] The present invention adopts steel fiber recycled concrete SFRRC, glass fiber reinforced composite material GFRP steel bars, and ultra-high performance concrete prefabricated UHPC pipe segments 4 to form a new single-column pier. The combined single-column pier has excellent bearing capacity, corrosion resistance, durability, economy and environmental protection. In addition, the steel pipe column 3 provides annular constraint for the SFRRC concrete in the core area, thereby enhancing the overall bearing capacity of the structure. The steel pipe column 3 and ordinary concrete not only provide annular constraint for the steel pipe column 3, but also concentrate the damage area in this part of the area, which is conducive to subsequent maintenance and replacement.

[0033] In this embodiment, an annular support frame is arranged on the periphery of the steel pipe column 3, and the support frame includes a plurality of support components, and adjacent support components are detachably connected through a connecting structure; the support components include a plurality of inner arc rods 5 that are in contact with the outer wall of the steel pipe column 3, and a plurality of connecting rods 8 that are away from the center of the steel pipe column 3 are fixed on the inner arc rods 5, and the horizontally adjacent connecting rods 8 are fixedly connected by outer arc rods 6 that are concentric with the inner arc rods 5, and the ends of the connecting rods 8 are threadedly connected with coaxial adjusting rods 10, and the ends of the adjusting rods 10 are provided with arc-shaped clamping blocks 9; a plurality of groups of positioning protrusions 11 for engaging the inner arc rods 5 are welded on the outer wall of the steel pipe column 3, and in order to strengthen the fixation of the positioning protrusions 11 to the inner arc rods 5, the positioning protrusions 11 are detachably connected with bolts (conventional technical means, so not drawn in the figure), and the bolts are removed after the connecting structure is installed; vertical rods 7 are fixed between vertically adjacent inner arc rods 5 and between vertically adjacent outer arc rods 6.

[0034] In this solution, after the steel pipe column 3 is installed, the support components are successively engaged with the positioning protrusions 11, and the support components are preliminarily installed on the steel pipe column 3. The adjacent support components are connected by a connection structure to form an annular support frame. Then, the first section of the precast UHPC pipe segment 4 is hoisted onto the bearing platform 1. Only by rotating the adjusting rod 10, the abutting block 9 at the end of the adjusting rod 10 is abutted against the inner wall of the precast UHPC pipe segment 4, and the positioning and installation of the precast UHPC pipe segment 4 are completed. There is no need to additionally set up a truss for support, which can effectively shorten the construction process and save construction time.

[0035] In this embodiment, the connection structure includes a hollow support rod 12. Arc-shaped and hollow connection segments 13 communicating with the corresponding inner arc rods 5 and outer arc rods 6 are welded on both sides of the support rod 12. Arc-shaped positioning segments 14 are slidably connected in the connection segments 13. An elastic reset member 18 is arranged between the positioning segment 14 and the connection segment 13. A limiting protrusion (not shown in the figure) for limiting the positioning segment 14 from sliding out of the connection segment 13 is integrally formed on the positioning segment 14. A chute is opened at one end of the positioning segment 14 facing the support rod 12. A push rod 15 is slidably connected in the chute. One end of the push rod 15 extends into the support rod 12, and an elastic support member 16 is arranged between the other end of the push rod 15 and the chute. A number of through grooves communicating with the chute are opened on the circumferential side of the end of the positioning segment 14 away from the support rod 12. Limit blocks 17 are slidably connected in the through grooves. The same elastic reset member 18 is arranged between each limit block 17 and the through groove. A number of limit grooves for cooperating with the limit blocks 17 are opened on the inner walls at both ends of the inner arc rod 5 and the outer arc rod 6. A coaxial screw rod 19 is rotatably connected in the support rod 12. Two pushing blocks 20 threadedly connected with the screw rod 19 are slidably connected inside the support rod 12. The end face of the pushing block 20 facing the center of the steel pipe column 3 is inclined.

[0036] In this solution, after the supporting component is initially installed on the steel pipe column 3, the connecting structure is installed at the gap between adjacent supporting components; by rotating the screw 19, the pushing block 20 is driven to move towards the steel pipe column 3, and the pushing block 20 drives the positioning section 14 to slide into the corresponding inner arc rod 5 and outer arc rod 6 through the extrusion of the ejector rod 15. When the positioning section 14 moves to the limit position, the ejector rod 15 squeezes the elastic resetting member 18 and continues to move until the ejector rod 15 squeezes and pushes the limiting block 17 into the limiting groove to connect and lock the adjacent supporting components; when the ordinary concrete area needs to be demolished, the precast UHPC pipe segment 4 of the corresponding segment is knocked out to expose the support rod 12, and the pushing block 20 is driven to reset by reversely rotating the screw 19. The ejector rod 15 moves reversely under the action of the elastic support member 16 and no longer squeezes the limiting block 17. The limiting block 17 slides into the positioning section 14 under the action of the elastic resetting member 18 to release the connection between the positioning section 14 and the corresponding inner arc rod 5 and outer arc rod 6, and the positioning section 14 also slides into the connecting section 13 under the action of the elastic resetting member 18 to release the connection between the supporting components, so as to facilitate the demolition of the ordinary concrete.

[0037] In this embodiment, it further includes a precast replacement segment 21 made of UHPC. The precast replacement segment 21 is an arc-shaped structure symmetrically arranged left and right. Adjacent precast replacement segments 21 are bonded by epoxy resin. A through hole facing the connecting rod 8 is provided on the precast replacement segment 21.

[0038] After the precast UHPC pipe segment 4 and the ordinary concrete are demolished, the adjusting rod 10 on the support frame is screwed out, and the precast replacement segment 21 is hoisted so that the through hole on the precast replacement segment 21 faces the connecting rod 8. Adjacent precast replacement segments 21 are bonded by epoxy resin; then the adjusting rod 10 is screwed in through the through hole so that the abutting block 9 fits against the outer wall of the precast replacement segment 21 to play a role in positioning, supporting and fixing; then ordinary concrete is re-poured to complete the repair.

[0039] In this embodiment, a sealing block made of rubber is clamped at the end of the support rod 12, and the connection part is made non-bonded to prevent concrete from entering the support rod 12 and causing the screw 19 to be fixed and unable to rotate.

[0040] In this embodiment, the mass mix ratio of the SFRRC concrete is 75 parts of recycled concrete, 20 parts of class I fly ash, 0.5 part of FN-H high-range water reducer, 1 part of shear-end hooked steel fiber, and 28.5 parts of P.O42.5 ordinary Portland cement; the mass mix ratio of the recycled concrete is 50% recycled coarse aggregate and 50% natural sand and gravel. The recycled coarse aggregate is formed by crushing, washing, grading and mixing waste concrete blocks.

[0041] A construction method for a combined single-column pier of UHPC pipe - SFRRC - GFRP bars, characterized by including the following steps:

[0042] Step 1: clean the top surface of the platform 1, level it according to the design elevation, clean the embedded steel bars of GFRP material and weld the steel cage 2 of GFRP material to the embedded steel bars according to the specification requirements; hoist the steel pipe column 3 at the bottom and weld it to the steel cage 2; engage the supporting components with the positioning protrusions 11 in turn, preliminarily install the supporting components on the steel pipe column 3, and then install the connecting structure in the gap between the adjacent supporting components; drive the pushing block 20 to move toward the steel pipe column 3 by rotating the screw 19, and the pushing block 20 drives the positioning section 14 to slide into the corresponding inner arc rod 5 and outer arc rod 6 by squeezing the push rod 15. When the positioning section 14 moves to the limit position, the push rod 15 squeezes the elastic reset member 18 and continues to move until the push rod 15 squeezes and pushes the limit block 17 to insert into the limit groove, connects and locks the adjacent supporting components to form a support frame, and performs a non-bonding treatment on the connecting structure;

[0043] Step 2: hoist the first section of the prefabricated UHPC pipe segment 4 onto the cap 1, rotate the adjusting rod 10 so that the abutment block 9 at the end of the adjusting rod 10 abuts against the inner wall of the prefabricated UHPC pipe segment 4, complete the positioning and installation of the prefabricated UHPC pipe segment 4, and use UHPC mortar to connect the cap 1 with the first section of the prefabricated UHPC pipe segment 4, and then pour SFRRC concrete into the steel pipe column 3; and then pour ordinary concrete between the steel pipe column 3 and the prefabricated UHPC pipe segment 4;

[0044] Step 3: After the SFRRC concrete and ordinary concrete of the bottom segment have finally set and reached a certain strength, weld the second segment of the steel cage 2 and the second segment of the steel pipe column 3; then install the support frame, and position and hoist the second segment of the prefabricated UHPC pipe segment 4, and use epoxy resin mortar for bonding to prevent corrosion and leakage;

[0045] Step 4: Repeat step 3 for the third and subsequent installations;

[0046] Step 5: Pour ordinary concrete from the top steel pipe column 3 at one time, and pour SFRRC concrete from the top prefabricated UHPC pipe segment 4 at one time. Each pouring cycle needs to be divided into three segments. The pouring height in the final stage should be controlled according to the bottom elevation of the pier cap, and the surface should be roughened before the inner core SFRRC concrete and ordinary concrete are finally set.

[0047] Step Six: When the precast UHPC pipe segment 4 and the normal concrete area of a certain segment are damaged or cracked, knock out the precast UHPC pipe segment 4 of the corresponding segment to expose the support rod 12. Drive the push block 20 to reset by rotating the screw 19 in the reverse direction. The ejector rod 15 moves in the reverse direction under the action of the elastic support member 16 and no longer presses the limit block 17. The limit block 17 slides into the positioning section 14 under the action of the elastic reset member 18 and releases the connection between the positioning section 14 and the corresponding inner arc rod 5 and outer arc rod 6. The positioning section 14 also slides into the connection section 13 under the action of the elastic reset member 18 to release the connection between the support components, so as to facilitate the removal of the normal concrete;

[0048] Step Seven: Weld or repair the positioning protrusion 11, reinstall the self-supporting frame, and screw out the adjusting rod 10 on the support frame. Lift and install the precast replacement segment 21 so that the through hole on the precast replacement segment 21 is aligned with the connecting rod 8. Bond the adjacent precast replacement segments 21 with epoxy resin; then screw the adjusting rod 10 into the through hole so that the pressing block 9 fits against the outer wall of the precast replacement segment 21 to play a role in positioning, supporting and fixing; then re-pour the normal concrete.

[0049] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A combined single-column pier of UHPC tube - SFRRC - GFRP bars, characterized in that: It includes a bearing platform, on which embedded steel bars are arranged. A steel reinforcement cage is fixed on the embedded steel bars. A number of mutually fixed and coaxial steel pipe columns are sleeved on the steel reinforcement cage. Prefabricated UHPC pipe segments are sleeved on the outer sides of the steel pipe columns, and adjacent prefabricated UHPC pipe segments are bonded by epoxy resin; SFRRC concrete is poured inside the steel pipe columns, and ordinary concrete is poured between the steel pipe columns and the prefabricated UHPC pipe segments; both the embedded steel bars and the steel reinforcement cage are made of GFRP steel bars; an annular support frame is arranged on the circumference of the steel pipe column, and the support frame includes a number of support components, and adjacent support components are detachably connected by a connection structure; the support component includes a number of inner arc bars that fit the outer wall of the steel pipe column, and a number of connecting rods deviating from the center of the steel pipe column are fixed on the inner arc bars. Horizontally adjacent connecting rods are fixedly connected by outer arc bars concentric with the inner arc bars. The end of the connecting rod is threadedly connected with a coaxial adjusting rod, and an arc-shaped pressing block is arranged at the end of the adjusting rod; a number of positioning protrusions for clamping the inner arc bars are arranged on the outer wall of the steel pipe column; vertical rods are fixed between vertically adjacent inner arc bars and between vertically adjacent outer arc bars.

2. The combined single-column pier of UHPC tube - SFRRC - GFRP bars according to claim 1, characterized in that: The connection structure includes a hollow support rod. Arc-shaped and hollow connection sections communicating with the corresponding inner arc bars and outer arc bars are arranged on both sides of the support rod. Arc-shaped positioning sections are slidably connected in the connection sections. An elastic resetting member is arranged between the positioning section and the connection section. A chute is opened at one end of the positioning section facing the support rod. A push rod is slidably connected in the chute. One end of the push rod extends into the support rod, and an elastic support member is arranged between the other end of the push rod and the chute; a number of through grooves communicating with the chute are opened on the circumference of the end of the positioning section away from the support rod. Limit blocks are slidably connected in the through grooves, and the same elastic resetting members are arranged between the limit blocks and the through grooves. A number of limit grooves cooperating with the limit blocks are opened on the inner walls at both ends of the inner arc bars and the outer arc bars; a coaxial screw rod is rotatably connected in the support rod, and two pushing blocks threadedly connected with the screw rod are slidably connected inside the support rod. The end face of the pushing block facing the center of the steel pipe column is inclined.

3. The combined single-column pier of UHPC tube - SFRRC - GFRP bars according to claim 2, characterized in that: It also includes a prefabricated replacement section made of UHPC. The prefabricated replacement section is an arc-shaped structure symmetrically arranged left and right. Adjacent prefabricated replacement sections are bonded by epoxy resin, and through holes facing the connecting rods are arranged on the prefabricated replacement section.

4. The combined single-column pier of UHPC tube - SFRRC - GFRP bars according to claim 3, characterized in that: A plugging block is detachably connected to the end of the support rod, and no bonding treatment is done at the connection.

5. The combined single-column pier of UHPC tube - SFRRC - GFRP bars according to claim 4, wherein: The mass mix ratio of the SFRRC concrete is 75 parts of recycled concrete, 20 parts of class I fly ash, 0.5 part of FN-H high-range water reducer, 1 part of shear-end hooked steel fiber, and 28.5 parts of P.O42.5 ordinary Portland cement; the mass mix ratio of the recycled concrete is 50% of recycled coarse aggregate and 50% of natural sand and gravel. The recycled coarse aggregate is formed by crushing, cleaning, grading, and mixing waste concrete blocks.

6. The construction method of a combined single-column pier of UHPC tube - SFRRC - GFRP bars according to claim 5, characterized in that, It includes the following steps: Step 1: Clean the top surface of the pedestal, level it according to the design elevation, clean the embedded steel bars of GFRP material and weld the steel cage of GFRP material to the embedded steel bars according to the specification requirements; hoist the steel pipe column at the bottom and weld it to the steel cage; engage the support components with the positioning protrusions in turn, preliminarily install the support components on the steel pipe column, and then install the connecting structure in the gap between adjacent support components; drive the push block to move toward the steel pipe column by rotating the screw rod, and the push block drives the positioning section to slide into the corresponding inner arc rod and outer arc rod by squeezing the push rod. When the positioning section moves to the limit position, the push rod squeezes the elastic reset part and continues to move until the push rod squeezes and pushes the limit block to insert into the limit groove, connects and locks the adjacent support components to form a support frame, and performs non-bonding treatment on the connecting structure; Step 2: hoist the first section of the prefabricated UHPC pipe segment onto the pedestal, rotate the adjusting rod so that the abutment block at the end of the adjusting rod abuts against the inner wall of the prefabricated UHPC pipe segment, complete the positioning and installation of the prefabricated UHPC pipe segment, and use UHPC mortar to connect the pedestal with the first section of the prefabricated UHPC pipe segment, and then pour SFRRC concrete into the steel pipe column; and then pour ordinary concrete between the steel pipe column and the prefabricated UHPC pipe segment; Step 3: After the SFRRC concrete and ordinary concrete of the bottom section have finally set and reached a certain strength, weld the second section of the steel cage and the second section of the steel pipe column; then install the support frame, and position and hoist the second section of the prefabricated UHPC pipe segment, and use epoxy resin mortar for bonding to prevent corrosion and leakage; Step 4: Repeat step 3 for the third and subsequent installations; Step 5: Pour ordinary concrete from the top steel pipe column at one time, and pour SFRRC concrete from the top prefabricated UHPC pipe segment at one time. Each pouring cycle needs to be divided into three segments; the pouring height in the final stage should be controlled according to the bottom elevation of the pier cap, and the surface should be roughened before the inner core SFRRC concrete and ordinary concrete are finally set; Step 6: When the prefabricated UHPC pipe segment and the ordinary concrete area of a certain section are damaged or cracked, the prefabricated UHPC pipe segment of the corresponding section is knocked out to expose the support rod, and the push block is reset by rotating the screw rod in the opposite direction. The push rod moves in the opposite direction under the action of the elastic support member and no longer squeezes the limit block. The limit block slides down into the positioning section under the action of the elastic reset member and releases the connection between the positioning section and the corresponding inner arc rod and outer arc rod. The positioning section also slides down into the connecting section under the action of the elastic reset member to release the connection between the support components, so as to facilitate the removal of the ordinary concrete. Step 7: Weld or repair the positioning protrusions, reinstall the self-supporting frame, unscrew the adjusting rod on the supporting frame, hoist the prefabricated replacement section, make the through hole on the prefabricated replacement section face the connecting rod, and bond adjacent prefabricated replacement sections with epoxy resin; then screw the adjusting rod through the through hole to make the tightening block fit against the outer wall of the prefabricated replacement section to play a role in positioning, supporting and fixing; then re-pour ordinary concrete.

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