RC column toughness improving device and method based on FRP constraint prefabricated reinforcement UHPC formwork

Abstract

The invention discloses an RC column toughness improving device and method based on an FRP constraint prefabricated reinforcement UHPC formwork. The device comprises a UHPC shell, filler and FRP cloth. The UHPC formwork shell is prefabricated in a factory, the section of an original reinforced concrete column is modified according to needs, and the UHPC formwork shell is used as a permanent formwork. The FRP cloth is wrapped outside the UHPC shell through a binder to fix the UHPC shell, and meanwhile, annular constraint is provided for a reinforced whole body, so that the strength, ductility and durability of the UHPC shell are improved; and the filler is poured into a gap between the UHPC shell and the reinforced concrete column, so that the reinforced concrete column and the FRP-UHPC formwork are connected into a whole and work cooperatively. Prefabricated assembly can be achieved, formworks and supports are not needed during construction, and the strength of the reinforced concrete column can be remarkably improved under the condition that the sectional area and the weight are slightly increased. And the reinforced concrete column can be reinforced, the damaged reinforced concrete column can be rapidly repaired, and toughness improvement of residential buildings and infrastructures is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete column reinforcement, and in particular to a device and method for improving the toughness of an RC column based on an FRP-constrained prefabricated reinforced UHPC formwork. Background Art

[0002] In today's construction industry, existing reinforced concrete (RC) columns face many challenges. Over time, due to factors such as structural aging, changes in usage functions, design and construction defects, and improved seismic standards, as well as long-term service or disasters, RC columns are often partially damaged, which urgently requires reinforcement and repair work to quickly restore their proper functional characteristics.

[0003] The enlarged section method and fiber reinforced polymer (FRP) restraint are the two most common means in RC column reinforcement projects. As for the enlarged section method, the implementation process requires construction formwork and support, and the concrete curing takes a long time, resulting in a long construction period. It will also significantly increase the deadweight and cross-sectional area of ​​the column, occupying a large indoor space. The FRP reinforcement method needs to ensure that the column surface is flat and crack-free, otherwise it is very easy to cause FRP peeling, concrete cracking or local crushing and other common damages, which make the surface treatment of RC columns difficult, and then cause stress concentration of FRP, causing it to break prematurely and unable to give full play to its strength advantages. The strength and durability of the ultra-high performance concrete (UHPC) shell are relatively good, but the existing application method is to support the formwork around the column to be reinforced and then pour it. Compared with the enlarged section method, the use of UHPC effectively reduces the cross-sectional area, but there are also problems such as the need for formwork and long curing period, which cannot meet the needs of rapid repair under the background of toughness. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for improving the toughness of RC columns based on FRP-constrained prefabricated reinforced UHPC formwork, which can realize fast and efficient assembly around the RC square column, quickly repair damaged RC square columns, and improve the toughness of residential buildings and infrastructure.

[0005] The technical solution of the present invention is:

[0006] A RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork comprises: a UHPC shell, which is prefabricated according to the size of a RC square column to be reinforced, and comprises two half shells, the two half shells are butt-jointed and assembled on the periphery of the RC square column, and the space between the inner wall of the UHPC shell and the RC square column is used for pouring filler, and the filler can be one of UHPC, concrete, grouting material, and cement mortar, so that the UHPC shell and the RC square column are connected as a whole and work together to enhance the integrity of the reinforced structure; due to the ultra-high strength of UHPC, compared with the reinforcement method of ordinary concrete, under the same reinforcement effect, the amount of concrete used is reduced, thereby ensuring the use space of the building and reducing the deadweight of the structure; FRP cloth, wrapped around the periphery of the UHPC shell, is used to provide lateral constraints to the reinforced area, thereby improving the strength and ductility of the RC column, and an adhesive is coated between the FRP cloth and the UHPC shell. The adhesive includes epoxy resin adhesive, phenolic resin adhesive or urea-formaldehyde resin adhesive, so that the FRP cloth and the UHPC shell are well connected and the circumferential restraint effect of the FRP cloth is fully exerted. In addition, the adhesive has good durability, which can extend the overall life and reduce maintenance costs.

[0007] Furthermore, the shape of the half shell of the UHPC shell is selected from one of a semi-cylindrical shell and a cylindrical half shell with an outer square and an inner circle chamfered, and the inner wall diameter of the UHPC shell is not less than the diagonal length of the RC square column section, and the height is not less than the height of the plastic hinge at the bottom of the RC square column, and the chamfer radius of the cylindrical half shell with an outer square and an inner circle chamfered is not less than 20 mm.

[0008] Furthermore, when performing full-height reinforcement, a groove is opened at the top of the UHPC shell, and the grouting pipe is inserted into the groove, and continuous pouring is performed until it overflows from the other end of the groove and fills the gap between the upper end of the UHPC shell and the floor slab, and then maintained at appropriate temperature and humidity.

[0009] Furthermore, the UHPC shell is prepared by a centrifugal process in a factory using a UHPC mixture and a steel cage, wherein the steel cage includes a plurality of longitudinal bars and a plurality of stirrups, and the steel cage is formed by binding the plurality of longitudinal bars and the plurality of stirrups. The steel cage may also use FRP bars, and the longitudinal bars may be prestressed or not according to engineering requirements.

[0010] Furthermore, a method for improving the toughness of reinforced concrete square columns by using an RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork comprises the following steps:

[0011] S1. Determine the size of the UHPC shell: Measure the size of the RC square column to be reinforced. It is recommended that the maximum gap size be controlled within 30mm. Determine the size of the UHPC shell based on the size of the RC square column;

[0012] S2. Prefabricated UHPC shell: Prefabricate the UHPC shell in the factory by centrifugal process according to the determined UHPC shell size;

[0013] S3. Clean the columns to be reinforced: fully roughen the surface of the RC square column, remove the deteriorated concrete such as peeling, looseness, honeycomb, corrosion, etc. to expose the steel bars, and moisten the concrete surface of the RC square column;

[0014] S4. Clean the surface of the UHPC shell: Use tools such as concrete angle grinders and grinding wheels to remove impurities such as slurry and oil stains on the surface of the UHPC shell to ensure that the surface of the UHPC shell is flat;

[0015] S5. Splicing UHPC shell: Splice two UHPC half shells and bond them with adhesive at the joints, and place a support frame on the outside of the butted UHPC shells. The support frame is required when reinforcing the entire height. If only the plastic hinge at the bottom of the column is reinforced, the support frame is not required. The legs of the support frame can be retracted for length adjustment, and a rubber pad is provided at the contact between the support frame and the UHPC shell.

[0016] S6. Apply primer and level: Stir the adhesive until the color is uniform, and use a roller brush or a brush to evenly apply the adhesive on the surface of the UHPC shell, and ensure that there is no leakage, flow, or bubbles. Wait until it is dry to the touch, and use a scraper to repair and fill the uneven parts;

[0017] S7. Paste FRP cloth: Cut the FRP cloth according to the design requirements, press the FRP cloth lightly on the outside of the UHPC shell, paste the FRP cloth from bottom to top, and ensure that the overlap length of the FRP cloth along the fiber stress direction is not less than 100mm. Use a special roller to roll along the column circumference for multiple times and squeeze out bubbles to make the adhesive fully saturate the FRP cloth. Repeat the above steps to paste multiple layers of FRP cloth. The overlap positions of each layer of FRP cloth should be staggered. Apply the adhesive evenly on the outer surface of the last layer of FRP cloth and wait for it to dry. After the UHPC shell is stable, remove the support frame;

[0018] S8, grouting: If the plastic hinge area at the bottom of the column is reinforced, the filler is poured along the upper end of the gap between the UHPC shell and the RC square column, and poured continuously until the filler overflows from the upper edge of the other side, and then cured at appropriate temperature and humidity. If the full height is reinforced, the filler is injected from the groove of the UHPC shell.

[0019] Furthermore, in S1, for RC square columns whose surface concrete has not fallen off, a UHPC shell with the same size as the RC square column can be selected. The size of the RC square column is the length of the cross-section diagonal. No grouting is required, and the UHPC shell and the RC square column are directly bonded with an adhesive.

[0020] Furthermore, in S5, when the RC square column is reinforced at full height, a plurality of the UHPC shells may be used for upper and lower splicing, and the splicing positions of two adjacent UHPC shells are bonded with an adhesive.

[0021] Further, the centrifugal process step comprises:

[0022] Tie up steel cage; formwork and fix;

[0023] Calculate the amount of UHPC mixture and mix the UHPC mixture;

[0024] The tied steel cage is loaded into the steel mold and fixed. The steel mold is filled with UHPC mixture and then closed. The steel mold is centrifuged by a centrifuge and subjected to steam initial curing, demoulding, and steam final curing.

[0025] Furthermore, the steel mold for preparing the UHPC shell in the centrifugal process includes: two half molds, an upper mold and a lower mold; a plurality of running wheels evenly distributed in the circumferential direction are provided on the groove wall of the half mold, which are used to adapt to the rollers of the centrifuge and drive the steel mold to rotate; an annular rib plate evenly distributed in the circumferential direction and longitudinal reinforcing ribs spaced along the axial direction are provided between each adjacent running wheel, which are used to improve the mold strength; a partition plate, which is welded on the symmetry axis of the inner wall of the half mold, and the height is less than the radius of the half mold and greater than the thickness of the UHPC shell; a head plate A through hole is opened in the center, and a head plate is welded to the end of the half mold so that a cavity is formed inside and the position of the steel cage is fixed after the two half molds are buckled together; a flange connecting plate is arranged in the lower mold, and one end is connected to a connecting rod, and the connecting rod is located in the through hole in the center of the head plate and is fixed by a clamping bolt. The longitudinal reinforcement in the steel cage passes through the reserved hole on the flange connecting plate and is fixed by a hexagonal flange bolt, connected to the flange connecting plate and the connecting rod to form a whole, and then inserted into the circular hole of the head plate, and then tightened and fixed with a limit plate and a clamping bolt.

[0026] Furthermore, the edges of the two half molds of the steel mold are provided with a locking structure along the axial direction, and the locking structure includes: a protruding structure on the upper mold; and a groove structure on the lower mold matching the protruding structure. After the mold is closed, a reliable seal is achieved inside the steel mold. After the upper mold and the lower mold are buckled, the mold bolts are passed through the bolt holes to lock the upper and lower molds.

[0027] The process of preparing the UHPC shell by the steel mold comprises the following steps:

[0028] Binding, mold installation and fixation of steel cage: Bind the longitudinal reinforcement and stirrups to form a steel cage, cut the stirrups symmetrically along the symmetry axis except for the two ends of the steel cage, and bend the ends inward along the outer diameter of the longitudinal reinforcement to leave a gap for inserting the partition; place the bound steel cage in the lower mold, and connect it with the flange connection plate and the connecting rod to form a whole through the mold bolts, then insert it into the circular hole of the head plate, and then tighten it with the limit plate and the clamping bolts;

[0029] Measuring and mixing of UHPC mixture: According to the dosage requirements of UHPC shell, accurately measure the premix, water, admixture and steel fiber according to the mix ratio, and add them into the forced mixer in sequence for mixing, ensuring uniform mixing;

[0030] Place UHPC mixture in the steel mold: fill the UHPC mixture evenly along the lower mold;

[0031] Mold closing: Lift the upper mold above the lower mold, gradually lower the upper mold, align and clamp the locking structure, and pass the mold closing bolts through the bolt holes to fix the upper and lower steel molds;

[0032] Centrifugal forming: The steel mold is hoisted above the centrifuge and accelerated step by step according to the low-speed, medium-speed and high-speed centrifugal system. The speed in the low-speed stage is set to 300r / min to make the UHPC mixture dispersed, reasonably distributed and initially formed. This stage lasts for 2 to 3 minutes; the speed in the medium-speed stage is set to 600r / min, and the gradual speed increase is conducive to the redistribution of the uneven sections of the mixture and further forming. This stage lasts for 5 minutes; the speed in the high-speed stage is set to 1100r / min. The huge centrifugal force generated by high-speed rotation fully discharges and squeezes the internal moisture and voids, so that the prefabricated UHPC shell is finally formed densely. This stage lasts for 15 minutes; after the centrifugation is completed, the steel mold is left on the centrifuge for about 2 hours;

[0033] Steam initial curing: The steel mold after centrifugation and static is hoisted into the steam curing tank for initial curing, so that the UHPC shell reaches the demoulding strength, and the initial curing time is set to 12h;

[0034] Demolding: hoist the steel mold after initial steam curing to the demoulding table, remove the mold bolts with a pneumatic wrench, hoist the mold, and then lift the UHPC shell for demoulding, avoiding collision during the hoisting process; remove the flange connecting plate, connecting rod, limit plate and mold tightening bolts, and clean the upper and lower molds;

[0035] Steam final curing: The demoulded UHPC shell is placed in the autoclave for high-temperature steam curing for 48 hours. The strength after final curing can reach the design strength.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The UHPC shell of the present invention, which is spliced ​​with two half-shell structures, is prefabricated and assembled in a factory according to the size of the square column to be reinforced. During construction, the two half-shells are directly buckled around the periphery of the square column to be reinforced, and the UHPC shell is wrapped and reinforced with FRP cloth, so that it can be quickly and efficiently assembled around the periphery of the RC square column, and not only the RC square column can be reinforced, but also the UHPC shell and the RC square column can be connected as a whole by pouring filler between the inner wall of the UHPC shell and the RC square column, thereby enhancing the integrity of the reinforced structure, thereby quickly repairing the damaged RC square column, and improving the toughness of residential buildings and infrastructure.

[0038] The present invention effectively combines the excellent properties of two high-performance materials, UHPC and FRP. It gives full play to the compressive properties of UHPC and the tensile properties of FRP, effectively improving the bearing capacity and deformation resistance of RC columns with less increase in cross-sectional area and weight; utilizing the high density, impermeability, and frost resistance of UHPC and the excellent corrosion resistance of FRP, it can effectively resist the erosion of external environmental factors such as moisture and chemicals, significantly improve the service life of the reinforced structure, and reduce maintenance costs; and the bonding performance of UHPC and the surface of RC square columns is good, and it can bear force together with the whole, providing a reliable bonding foundation for FRP, avoiding the peeling phenomenon caused by concrete cracking and dislocation when FRP is used alone.

[0039] The longitudinal reinforcement in the UHPC shell of the present invention can bear tensile stress and compressive stress, and the stirrups can effectively resist shear force. The combined effect of the two can significantly improve the bearing capacity and shear resistance of the UHPC shell, enhance the integrity and stability of the reinforced structure, reduce the generation and development of cracks, improve the ductility and durability of the structure, and reduce long-term maintenance costs.

[0040] The size and shape of the UHPC shell of the present invention can be customized according to the cross-sectional size of the RC column. The square cross-section of the original RC column can be modified into a circular cross-section or a square chamfered cross-section as needed, and the UHPC shell can be spliced ​​according to the reinforcement height, and can be flexibly applied to the rapid repair of RC square columns and rectangular columns of various shapes and sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is an overall schematic diagram of the FRP-constrained UHPC formwork for quickly repairing the plastic hinge area of ​​a RC square column according to the present invention;

[0042] Figure 2 It is a cross-sectional schematic diagram of the RC square column reinforced with FRP and semi-cylindrical UHPC formwork according to the present invention;

[0043] Figure 3 This is an overall schematic diagram of the FRP-constrained UHPC formwork for quickly repairing the full-height area of ​​a RC square column according to the present invention;

[0044] Figure 4 It is a schematic cross-sectional view of the RC square column reinforced with the FRP and the cylindrical UHPC formwork with outer square and inner round chamfers according to the present invention;

[0045] Figure 5 A three-dimensional schematic diagram of a centrifugal forming mold for preparing a semi-cylindrical UHPC shell according to the present invention;

[0046] Figure 6 This is a schematic diagram of the centrifugal forming lower mold and the placement of the steel cage for preparing the semi-cylindrical UHPC shell according to the present invention;

[0047] Figure 7 It is a cross-sectional schematic diagram of a centrifugal forming mold for preparing a semi-cylindrical UHPC shell according to the present invention;

[0048] Figure 8 It is a cross-sectional schematic diagram of a centrifugal forming mold for preparing a cylindrical UHPC mold shell with a square outer surface and a round inner surface with chamfers according to the present invention.

[0049] Among them, 1. RC square column; 2. UHPC shell; 3. FRP cloth; 4. filling material; 5. grouting pipe; 6. adhesive; 7. groove; 8. steel cage; 9. longitudinal reinforcement; 10. stirrups; 11. steel mold; 1101. upper mold; 1102. lower mold; 1103. partition; 1104. cavity; 1105. groove wall; 1106. running wheel; 1107. annular rib; 1108. longitudinal reinforcement; 1109. mold bolt; 1110. bolt hole; 1111. locking structure; 1112. flange connecting plate; 1113. connecting rod; 1114. head plate; 1115. limit plate; 1116 mold tightening bolt. DETAILED DESCRIPTION

[0050] Combine the following Figures 1 to 8 , the specific embodiments of the present invention are described in detail. In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0051] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0052] Example

[0053] like Figure 1 As shown, a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork comprises: a UHPC shell 2 and an FRP cloth 3. The UHPC shell 2 is prefabricated according to the size of the RC square column 1 to be reinforced, and comprises two half shells. The two half shells are butt-jointed and assembled on the periphery of the RC square column 1. The space between the inner wall of the UHPC shell 2 and the RC square column 1 is used for pouring a filler 4. The filler 4 can be one of UHPC, concrete, grouting material, and cement mortar, so that the UHPC shell 2 and the RC square column 1 are connected as a whole and work together to enhance the integrity of the reinforced structure. Due to the ultra-high strength of UHPC, compared with the reinforcement method of ordinary concrete, under the same reinforcement effect, the amount of concrete used is reduced, thereby ensuring the use space of the building and reducing the deadweight of the structure. The FRP cloth 3 is wrapped around the periphery of the UHPC shell 2 to provide lateral constraints to the reinforced area, thereby improving the strength and ductility of the RC column, and an adhesive 6 is coated between the FRP cloth 3 and the UHPC shell 2. The adhesive 6 includes epoxy resin adhesive, phenolic resin adhesive or urea-formaldehyde resin adhesive, so that the FRP cloth 3 and the UHPC shell 2 are well connected and the circumferential restraint effect of the FRP cloth 3 is fully exerted. In addition, the adhesive 6 has good durability, which can extend the overall life and reduce maintenance costs.

[0054] In some embodiments, Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the shape of the half shell of the UHPC shell 2 is selected from one of a semi-cylindrical shell and a cylindrical half shell with an outer square and an inner circle with chamfers, and the inner wall diameter of the UHPC shell 2 is not less than the diagonal length of the cross section of the RC square column 1, and the height is not less than the height of the plastic hinge at the bottom of the RC square column 1, and the chamfer radius of the cylindrical half shell with an outer square and an inner circle with chamfers is not less than 20 mm.

[0055] In some embodiments, Figure 3As shown, a groove 7 is provided at the top of the UHPC shell 2, and the groove 7 is used to clamp the grouting pipe 5. When performing full-height reinforcement, a groove 7 is provided at the upper end of the UHPC shell 2, and the grouting pipe 5 is clamped into the groove 7, and continuous pouring is performed until the groove 7 overflows from the other end and fills the gap between the upper end of the UHPC shell 2 and the floor slab, and then curing is performed at appropriate temperature and humidity.

[0056] In some embodiments, Figure 5 and Figure 6 As shown, the UHPC shell 2 is prepared by using a centrifugal process in a factory using a UHPC mixture and a steel cage 8. The steel cage 8 includes a plurality of longitudinal bars 9 and a plurality of stirrups 10. The steel cage 8 is formed by binding the plurality of longitudinal bars 9 and the plurality of stirrups 10. Figure 7 It is a schematic cross-sectional view of the centrifugal forming mold (after buckling) of the cylindrical UHPC shell 2. Figure 8 It is a schematic diagram of the cross-section of the centrifugal forming mold (after buckling) of the UHPC shell 2 with an outer circle and an inner square with chamfers. The two types of UHPC shells 2 prepared by the corresponding centrifugal forming molds can reinforce the plastic hinge at the bottom of the column and the full height reinforcement. The steel cage 8 can also use FRP bars, and the longitudinal bars 9 can be selected to be prestressed according to engineering requirements.

[0057] The method for improving the toughness of reinforced concrete square columns by using a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork in this embodiment includes the following steps:

[0058] S1. Determine the size of the UHPC shell: Measure the size of the RC square column 1 to be reinforced. It is recommended that the maximum gap size be controlled within 30 mm. Determine the size of the UHPC shell 2 based on the size of the RC square column 1;

[0059] S2. Prefabricate the UHPC shell: prefabricate the UHPC shell 2 in the factory by a centrifugal process according to the determined size of the UHPC shell 2;

[0060] S3. Cleaning the column to be reinforced: roughen the surface of the RC square column 1, remove the deteriorated concrete to expose the steel bars, and moisten the concrete surface of the RC square column 1;

[0061] S4. Clean the surface of the UHPC shell: Use tools such as a concrete angle grinder, grinding wheel and sandpaper to remove impurities such as slurry and oil stains on the surface of the UHPC shell 2 to ensure that the surface of the UHPC shell 2 is flat;

[0062] S5. Splicing UHPC shell: Splice two UHPC half shells and bond them with adhesive 6 at the splicing point, and place a support frame on the outside of the butted UHPC shell 2; it is worth noting that the installation of the support frame is required when reinforcing the entire height. If only the plastic hinge at the bottom of the column is reinforced, the support frame is not required to assist. The legs of the support frame can be retracted for length adjustment, and a rubber pad is provided at the contact between the support frame and the UHPC shell 2;

[0063] S6, apply primer and level: stir the adhesive 6 until the color is uniform, use a roller brush or a brush to evenly apply the adhesive 6 on the surface of the UHPC shell 2, and ensure that there is no leakage, flow or bubbles, wait until it is dry to the touch, and use a scraper to repair and fill the uneven parts;

[0064] S7, pasting FRP cloth: cut FRP cloth 3 according to the design requirements, press FRP cloth 3 lightly by hand to paste it on the outside of UHPC shell 2, paste FRP cloth 3 from bottom to top, and ensure that the overlap length of FRP cloth 3 along the fiber stress direction is not less than 100mm, use a special roller to roll it several times along the column circumference direction and squeeze out bubbles, so that the adhesive 6 can fully penetrate FRP cloth 3, repeat the above steps to paste FRP cloth 3 in multiple layers, the overlap positions of each layer of FRP cloth 3 should be staggered, evenly apply adhesive 6 on the outer surface of the last layer of FRP cloth 3 and wait for drying, and remove the support frame after the UHPC shell 2 is stable;

[0065] S8, grouting: If the plastic hinge area at the bottom of the column is reinforced, the filler 4 is poured along the upper end of the gap between the UHPC shell 2 and the RC square column 1, and poured continuously until the filler 4 overflows from the upper edge of the other side, and then cured at appropriate temperature and humidity. If the full height is reinforced, the filler 4 is injected from the groove 7 of the UHPC shell 2.

[0066] In S1, for the RC square column 1 whose surface concrete has not fallen off, a UHPC shell 2 with the same size as the RC square column 1 can be selected. The size of the RC square column 1 is the length of the cross-section diagonal. No grouting is required, and the UHPC shell 2 and the RC square column 1 are directly bonded with an adhesive 6.

[0067] In S5, when the RC square column 1 is fully reinforced, multiple UHPC shells 2 can be used for upper and lower splicing, and the splicing points of two adjacent UHPC shells 2 are bonded with an adhesive 6.

[0068] The centrifugation process steps include:

[0069] Tie up the steel cage 8; formwork and fix;

[0070] Calculate the amount of UHPC mixture and mix the UHPC mixture;

[0071] The tied steel cage 8 is loaded into the steel mold 11 and fixed, and the steel mold 11 is closed after the UHPC mixture is filled in the steel mold 11. After centrifugal molding by a centrifuge, the steel cage 8 is subjected to steam initial curing, demoulding, and steam final curing.

[0072] like Figure 5-Figure 8 As shown, the steel mold 11 used for preparing the UHPC shell in the centrifugal process includes: two half molds, a partition plate 1103, a head plate 1114 and a flange connection plate 1112. Figure 7 As shown, the upper mold 1101 and the lower mold 1102 have semi-cylindrical cross sections. Figure 8 As shown, the two half-mold sections are an upper mold 1101 and a lower mold 1102 with an outer circle and an inner square; a plurality of running wheels 1106 evenly distributed in the circumferential direction are provided on the groove wall 1105 of the half mold, which are used to adapt to the rollers of the centrifuge and drive the steel mold 11 to rotate; an annular rib plate 1107 evenly distributed in the circumferential direction and longitudinal reinforcing ribs 1108 spaced apart in the axial direction are provided between each adjacent running wheel 1106, which are used to improve the strength of the mold; the partition plate 1103 is welded on the symmetry axis of the inner wall of the half mold, and its height is less than the radius of the half mold and greater than the thickness of the UHPC shell 2; the head plate 1114 is a semicircular plate body with a through hole in the center, and the head plate The plate 1114 is welded to the end of the half mold so that the cavity 1104 is formed inside after the two half molds are buckled; the flange connection plate 1112 is arranged in the lower mold 1102, and one end is connected to the connecting rod 1113, and the connecting rod 1113 is located in the through hole in the center of the head plate 1114 and is fixed by the clamping bolt 1116. The longitudinal reinforcement 9 in the steel cage 8 passes through the reserved hole on the flange connection plate 1112 and is fixed by the hexagonal flange bolt, and is connected with the flange connection plate 1112 and the connecting rod 1113 to form a whole, and then is inserted into the circular hole of the head plate 1114, and then is tightened and fixed by the limit plate 1115 and the clamping bolt 1116;

[0073] The edges of the two half molds of the steel mold 11 are both provided with a locking structure 1111 along the axial direction, and the locking structure 1111 includes: a protruding structure on the upper mold 1101; and a groove structure matching the protruding structure on the lower mold 1102. After the mold is closed, the inner part of the steel mold 11 is reliably sealed. After the upper mold 1101 and the lower mold 1102 are buckled together, the mold bolts 1109 are passed through the bolt holes 1110 to lock the upper and lower molds.

[0074] The process of preparing the UHPC shell 2 by the steel mold 11 includes the following steps:

[0075] Binding, mold installation and fixing of the steel cage: bind the longitudinal reinforcement 9 and the stirrups 10 to form the steel cage 8, cut the stirrups 10 symmetrically along the symmetry axis except for the two ends of the steel cage 8, and bend the ends inward along the outer diameter of the longitudinal reinforcement 9, so as to leave a gap for inserting the partition 1103; place the bound steel cage 8 in the lower mold 1102, and connect it with the flange connection plate 1112 and the connecting rod 1113 through the mold bolts 1109, and then insert it into the circular hole of the head plate 1114, and then tighten it with the limit plate 1115 and the clamping bolts 1116;

[0076] Measuring and mixing of UHPC mixture: according to the dosage requirements of UHPC shell 2, accurately measure the premix, water, admixture and steel fiber according to the mix ratio, and add them into the forced mixer in sequence for mixing, ensuring that the mixing is uniform;

[0077] Distribute the UHPC mixture in the steel mold: fill the UHPC mixture evenly along the lower mold 1102;

[0078] Mold closing: lift the upper mold 1101 above the lower mold 1102, gradually lower the upper mold 1101, align and clamp the locking structure 1111, and pass the mold closing bolts 1109 through the bolt holes 1110 to fix the upper and lower steel molds;

[0079] Centrifugal forming: The steel mold 11 is hoisted above the centrifuge and accelerated step by step according to the low-speed, medium-speed and high-speed centrifugal system. The speed in the low-speed stage is set to 300r / min to make the UHPC mixture dispersed, reasonably distributed and initially formed. This stage lasts for 2 to 3 minutes; the speed in the medium-speed stage is set to 600r / min, and the gradual speed increase is conducive to the redistribution of the uneven sections of the mixture and further forming. This stage lasts for 5 minutes; the speed in the high-speed stage is set to 1100r / min, and the huge centrifugal force generated by the high-speed rotation is used to fully discharge and squeeze the internal moisture and voids, so that the prefabricated UHPC shell is finally formed densely. This stage lasts for 15 minutes; after the centrifugation is completed, the steel mold 11 is left to stand on the centrifuge for about 2 hours;

[0080] Steam initial curing: the steel mold 11 after centrifugation and standing is hoisted into the steam curing tank for initial curing, so that the UHPC shell 2 reaches the demoulding strength, and the initial curing time is set to 12 hours;

[0081] Demolding: hoist the steel mold 11 after initial steam curing onto the demoulding platform, remove the mold bolts 1109 with a pneumatic wrench, hoist the upper mold 1101, and then hoist the UHPC shell 2 for demoulding, avoiding collision during the hoisting process; remove the flange connecting plate 1112, the connecting rod 1113, the limit plate 1115 and the mold tightening bolts 1116, and clean the upper and lower molds;

[0082] Steam final curing: The demoulded UHPC shell 2 is placed in an autoclave for high-temperature steam curing for 48 hours. The strength after final curing can reach the design strength.

[0083] The above disclosures are only several preferred specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork, characterized in that: include: The UHPC shell (2) is prefabricated according to the size of the RC square column (1) to be reinforced, and comprises two half shells, the two half shells are butt-jointed and assembled on the periphery of the RC square column (1), and the space between the inner wall of the UHPC shell (2) and the RC square column (1) is used for pouring the filling material (4), so that the UHPC shell (2) and the RC square column (1) are connected as a whole; The FRP cloth (3) is wrapped around the periphery of the UHPC shell (2) and is used to provide lateral constraints to the reinforcement area, and an adhesive (6) is applied between the FRP cloth (3) and the UHPC shell (2).

2. The RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork according to claim 1 is characterized in that: The shape of the half shell of the UHPC shell (2) is selected from one of a semi-cylindrical shell and a cylindrical half shell with a chamfered outer square and inner circle, and the inner wall diameter of the UHPC shell (2) is not less than the diagonal length of the cross section of the RC square column (1), and the height is not less than the height of the plastic hinge at the bottom of the RC square column (1).

3. According to the device for improving the toughness of reinforced concrete square columns based on FRP-constrained reinforced UHPC prefabricated formwork according to claim 1, a groove (7) is provided at the top of the UHPC shell (2), and the groove (7) is used to clamp the grouting pipe (5).

4. The RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork according to claim 1 is characterized in that: The UHPC shell (2) is prepared in a factory by using a centrifugal process from a UHPC mixture and a steel cage (8); the steel cage (8) comprises a plurality of longitudinal bars (9) and a plurality of stirrups (10); and the steel cage (8) is formed by binding the plurality of longitudinal bars (9) and the plurality of stirrups (10).

5. According to claim 1, a method for improving the toughness of reinforced concrete square columns using a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork, characterized in that: The following steps are involved: S1, measuring the size of the RC square column (1) to be reinforced, and determining the size of the UHPC shell (2) according to the size of the RC square column (1); S2. Prefabricate the UHPC shell (2) in a factory by a centrifugal process according to the determined size of the UHPC shell (2); S3, roughening the surface of the RC square column (1), removing the deteriorated concrete to expose the steel bars, and moistening the concrete surface of the RC square column (1); S4, removing impurities on the surface of the UHPC shell (2) to ensure that the surface of the UHPC shell (2) is smooth; S5, splicing the two UHPC half shells, bonding them at the splicing point with an adhesive (6), and placing a support frame on the outside of the butted UHPC shell (2); S6, applying primer and leveling: stirring the adhesive (6) until the color is uniform, and applying it evenly on the surface of the UHPC shell (2); S7, pasting FRP cloth: cut the FRP cloth (3) according to the design requirements, press the FRP cloth (3) lightly on the outside of the UHPC shell (2) by hand, paste the FRP cloth (3) from bottom to top, and ensure that the overlap length of the FRP cloth (3) along the fiber stress direction is not less than 100 mm, use a roller to roll it several times along the column circumference direction and squeeze out the bubbles, so that the adhesive (6) can fully penetrate the FRP cloth (3), repeat the above steps to paste multiple layers of FRP cloth (3), the overlap positions of each layer of FRP cloth (3) should be staggered, evenly apply the adhesive (6) on the outer surface of the last layer of FRP cloth (3) and wait for it to dry, and remove the support frame after the UHPC shell (2) is stable; S8, grouting: pour the filling material (4) along the upper end of the gap between the UHPC shell (2) and the RC square column (1) or the upper end groove (7) of the UHPC shell, and continue pouring until the filling material (4) overflows from the upper edge of the other side, and then cure at appropriate temperature and humidity.

6. The method for improving the toughness of reinforced concrete square columns by using a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork according to claim 5, characterized in that: In the above S1, for the RC square column (1) whose surface concrete has not fallen off, a UHPC shell (2) having the same size as the RC square column (1) is selected. The size of the RC square column (1) is the length of the cross-section diagonal. No grouting is required, and the UHPC shell (2) and the RC square column (1) are directly bonded using an adhesive (6).

7. The method for improving the toughness of reinforced concrete square columns by using a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork according to claim 1, characterized in that: In S5, when the RC square column (1) is reinforced at full height, a plurality of the UHPC shells (2) are used for upper and lower splicing, and the splicing points of two adjacent UHPC shells (2) are bonded with an adhesive (6).

8. The method for improving the toughness of reinforced concrete square columns by using a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork according to claim 5, characterized in that: The centrifugation process comprises: Tie up the steel cage (8); formwork and fix; Calculate the amount of UHPC mixture and mix the UHPC mixture; The tied steel cage (8) is placed in a steel mold (11) and fixed, and the steel mold (11) is filled with UHPC mixture and then closed. The steel mold (11) is centrifugally molded and then cured and demoulded.

9. The method for improving the toughness of reinforced concrete square columns by using a RC column toughness improvement device based on FRP-constrained prefabricated reinforced UHPC formwork according to claim 8, characterized in that: The steel mold (11) used for preparing the UHPC shell in the centrifugal process comprises: Two half molds, an upper mold (1101) and a lower mold (1102); a plurality of running wheels (1106) evenly distributed in the circumferential direction are provided on the groove wall (1105) of the half mold, which are used to adapt to the rollers of the centrifuge and drive the steel mold (11) to rotate; an annular rib plate (1107) evenly distributed in the circumferential direction and longitudinal reinforcing ribs (1108) spaced apart in the axial direction are provided between each adjacent running wheel (1106), which are used to improve the mold strength; A partition (1103) is welded on the symmetry axis of the inner wall of the half mold, and has a height less than the radius of the half mold and greater than the thickness of the UHPC shell (2); A head plate (1114) is provided with a through hole at the center, and the head plate (1114) is welded to the end of the half mold, so that after the two half molds are buckled together, a cavity (1104) is formed inside and the position of the steel cage (8) is fixed; A flange connecting plate (1112) is arranged in the lower mold (1102), one end of which is connected to a connecting rod (1113). The connecting rod (1113) is located in a through hole in the center of the head plate (1114) and is fixed by a clamping bolt (1116). The longitudinal reinforcement (9) in the steel cage (8) passes through the reserved hole on the flange connecting plate (1112) and is fixed.

10. The method for improving the toughness of reinforced concrete square columns by using a reinforced concrete square column toughness improvement device based on FRP-constrained reinforced UHPC prefabricated formwork according to claim 9, characterized in that: The edges of the two half molds of the steel mold (11) are both provided with a locking structure (1111) along the axial direction, and the locking structure (1111) comprises: a protruding structure on the upper mold (1101); and a groove structure on the lower mold (1102) matching the protruding structure.

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