Fiber-reinforced ultrahigh-strength and ultrahigh-toughness reinforced concrete structure and preparation process thereof

Abstract

The invention belongs to the technical field of reinforced concrete building components, and particularly relates to a fiber-reinforced ultrahigh-strength and ultrahigh-toughness reinforced concrete structure and a preparation process. The reinforced concrete structure comprises a reinforced concrete column, wherein the reinforced concrete column comprises a lower column body and an upper column body; a pair of superposed beams are symmetrically arranged around the center of the central axis of the reinforced concrete column, and each superposed beam comprises a precast beam and a superposed layer post-poured on the precast beam; one end, close to the reinforced concrete column, of the precast beam is sunken inwards to form a key groove, and the section of the key groove is U-shaped; steel strands are arranged in the precast beam, and each steel strand extends out of the corresponding key groove from the inner bottom of the precast beam; the beam-column joint is used for connecting the lower column body, the upper column body and the superposed beam through modified concrete poured on the end face of the top end of the lower column body and in the key groove; one end of the friction damper is fixed on the bottom surface of the precast beam, and the other end of the friction damper is fixed on the side surface of the lower column body.

Description

Technical Field

[0001] The present invention belongs to the technical field of reinforced concrete building components, and in particular relates to a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure and a preparation process thereof. Background Art

[0002] With the rapid development of the construction industry, prefabricated buildings have gradually become a new trend in the industry with their advantages of fast construction speed, controllable quality and low environmental impact. In this context, the application of prefabricated concrete structures is becoming more and more extensive. Among them, the beam-column joint is an important part of the structure. Its connection reliability and construction efficiency have become the key factors restricting the overall performance of prefabricated buildings.

[0003] Traditional cast-in-place concrete beam-column joints are complex to construct, have a poor on-site working environment, and are difficult to ensure the quality of the joint connections. To overcome these shortcomings, prefabricated concrete beam-column joint technology was born. This technology greatly improves construction efficiency and reduces safety risks during construction by prefabricating beams, columns and other components in factories and assembling them quickly on site.

[0004] However, there are still some challenges in the connection mode, node performance and construction technology of prefabricated concrete beam-column nodes. How to ensure the seismic performance, bearing capacity and construction convenience of the nodes has become a hot topic in the current research of prefabricated concrete structures. Summary of the invention

[0005] The present invention overcomes the deficiencies of the prior art and provides a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure and a preparation process.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure, comprising: The reinforced concrete column comprises a lower column body and an upper column body.

[0007] Composite beams: a pair of composite beams are arranged relative to the central axis of the reinforced concrete column. Each composite beam includes a precast beam and a composite layer cast on the precast beam. The end of the precast beam close to the reinforced concrete column is concave inward to form a keyway, and the cross section of the keyway is U-shaped. Steel strands are arranged in the precast beam, and each steel strand extends from the bottom of the precast beam to the outside of the keyway.

[0008] The beam-column joint is made of modified concrete poured on the top end face of the lower column and in the keyway, connecting the lower column, upper column and composite beam.

[0009] The friction damper is arranged on the side of the connection between the prefabricated beam and the lower column, with one end fixed to the bottom surface of the prefabricated beam and the other end fixed to the side of the lower column.

[0010] In a preferred embodiment of the present invention, the friction damper includes a T-shaped steel plate and two L-shaped steel plates respectively arranged on both sides of the T-shaped steel plate. The T-shaped steel plate includes a wing plate fixed to the prefabricated beam by bolts and a web plate perpendicular to the wing plate. The L-shaped steel plate includes a short limb fixed to the lower column by bolts and a long limb perpendicular to the short limb. The long limb of the L-shaped steel plate is slidably connected to the web plate of the T-shaped steel plate by bolts, and a friction damping area is provided on the contact surface between the long limb and the web plate.

[0011] In a preferred embodiment of the present invention, a through slot is provided in the center of the web along the normal direction of the web, and through holes perpendicular to the through slot are provided on the long limbs on both sides of the web. An adjusting bolt matching the inner diameter of the through hole is provided in the through slot, and both ends of the adjusting bolt pass through the through holes on both sides of the through slot and are fixed by nuts.

[0012] In a preferred embodiment of the present invention, the outer end of the steel strand extending out of the keyway is subjected to embossed anchor treatment to form an embossed anchor end.

[0013] In a preferred embodiment of the present invention, the outer end of the steel strand extending out of the keyway is fixed in the keyway of another oppositely arranged composite beam through an anchoring end plate. The anchoring end plate is a rectangular steel plate with an anchoring groove arranged along the width direction, and the width of the anchoring groove matches the width of the steel strand.

[0014] In a preferred embodiment of the present invention, a pier head steel bar is arranged in the beam-column joint, and two ends of the pier head steel bar are respectively anchored in the keyways of the composite beams on both sides of the beam-column joint.

[0015] In a preferred embodiment of the present invention, the area of ​​the precast beam provided with the keyway is a non-prestressed section, and the remaining part is a prestressed section. The steel strands in the prestressed section are pre-stressed and anchored by pre-tensioning. The steel strands in the non-prestressed section are not prestressed. The spacing of the stirrups in the non-prestressed section is smaller than the spacing of the stirrups in the prestressed section.

[0016] In a preferred embodiment of the present invention, the modified concrete comprises cement, quartz sand, mineral admixtures, polymer modifiers, water reducers, retarders, fibers and water. Among them, the cement is silicate cement; the quartz sand particle size is 0.016-1.25 mm; the mineral admixtures include silica fume, slag and fly ash with a mass fraction of 20-40%, 20-40% and 40-60% respectively; the polymer modifier is polyacrylic acid emulsion; the water reducer is polycarboxyl water reducer with a solid content greater than 20% and a water reduction rate greater than 29%; the retarder is sodium gluconate; the fibers include steel fibers and polypropylene fibers, the steel fibers have a diameter of 0.18-0.23 mm, a length of 12-14 mm and a tensile strength greater than 2850 MPa, and the polypropylene fibers have a diameter of 0.7-0.8 mm and an aspect ratio of 40-45.

[0017] In a preferred embodiment of the present invention, the modified concrete includes 700-800kg of silicate cement, 1000-1200kg of quartz sand, 140-200kg of mineral admixture, 80-120kg of polyacrylic acid emulsion, 30-60kg of polycarboxyl water reducer, 20-40kg of sodium gluconate, 120-150kg of steel fiber, 0.5-1.5kg of polypropylene fiber and 120-150kg of water per cubic meter.

[0018] A fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure preparation process, based on the above-mentioned reinforced concrete structure, comprises the following steps: S1. Prepare the lower column.

[0019] S2. Prepare prefabricated beams.

[0020] S3. Hoist precast beams and install friction dampers.

[0021] S4. Carry out embossed anchor treatment and install anchor end plates and pier head steel bars.

[0022] S5. Cast beam-column joints.

[0023] S6. Cast the superimposed layer.

[0024] S7. Casting the upper column: The present invention solves the defects existing in the background technology and has the following beneficial effects: (1) The present invention provides a fiber-reinforced ultra-high-strength and ultra-tough reinforced concrete structure and a preparation process. On the one hand, the physical structure of the beam-column joint is optimized to improve its bearing capacity and seismic performance. On the other hand, the concrete mix ratio is optimized to improve its strength, toughness and durability and reduce shrinkage.

[0025] (2) In the present invention, the precast beam and the lower column are connected by a U-shaped keyway; prestressed steel strands are arranged in the precast beams, and are anchored by embossed anchors or anchored end plates; modified concrete is poured at the beam-column joints; friction dampers are arranged; and pier head steel bars are arranged. The U-shaped keyway improves the connection strength and stability of the beam-column joints; the prestressed steel strands significantly enhance the bending resistance of the precast beams; the embossed anchors or anchored end plates enhance the anchoring effect of the steel strands, avoiding the bonding slip that is easily generated by the traditional steel strand anchoring method; the friction damper effectively dissipates seismic energy and enhances the seismic performance; and the pier head steel bars provide additional shear bearing capacity. By optimizing the physical structure, the present invention realizes a beam-column joint with high strength and high seismic resistance compared to the prior art. According to the results of the destruction test, the maximum load and cracking load of the structure of the present invention are higher than those of the prior art, especially compared with the embodiment without the friction damper, the maximum load is significantly improved, which proves the effectiveness of optimizing the physical structure.

[0026] (3) The beam-column joints of the present invention are cast with modified concrete, the components of which include cement, quartz sand, mineral admixtures, polyacrylic acid emulsion, polycarboxyl water reducer, sodium gluconate, steel fiber and polypropylene fiber. Among them, silicate cement provides basic strength; quartz sand is used as aggregate; mineral admixtures improve the durability and impermeability of concrete; polyacrylic acid emulsion is used as a polymer modifier to enhance the toughness and crack resistance of concrete and reduce the shrinkage rate; polycarboxyl water reducer improves the workability of concrete; sodium gluconate is used as a retarder to control the cement hydration rate; steel fiber and polypropylene fiber improve the tensile strength and crack resistance of concrete and enhance toughness. The present invention optimizes the mix ratio and uses high-performance admixtures and fiber materials, which significantly improves the comprehensive performance of concrete compared with the prior art. According to the experimental results, the strength and toughness of the embodiment using the modified concrete of the present invention are higher than those of the embodiment using only ordinary concrete, and the shrinkage rate is reduced, thereby improving the durability of the structure. In addition, the experiment also verified the optimal addition amount of polyacrylic acid emulsion and polypropylene fiber, proving the superiority of the mix ratio of the present invention.

[0027] (4) The optimized concrete mix ratio in the present invention improves the strength, toughness and durability of concrete, reduces shrinkage, and thus ensures the effective operation of prestressed steel strands and U-shaped keyways. High-performance concrete reduces the effect of concrete shrinkage on the bonding force of steel strands, further improving the bending strength and seismic resistance of beams. At the same time, high-toughness concrete can better resist cracks caused by earthquake impacts, and in combination with friction dampers, effectively improves the seismic performance and durability of the structure. The synergistic effect of the two ultimately achieves a reinforced concrete structure with high strength, high toughness, high durability and high seismic resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. Figure 1 It is an elevation view of a fiber-reinforced, ultra-high-strength, ultra-tough reinforced concrete structure; Figure 2 It is a structural diagram of precast beams; Figure 3 The friction damper structure is shown in Figure 2. Figure 1 ; Figure 4 The friction damper structure is shown in Figure 2. Figure 2 ; Figure 5 is a schematic diagram of the anchor end plate structure; Figure 6 It is a flow chart of the preparation process of fiber-reinforced ultra-high-strength and ultra-tough reinforced concrete structure; In the figure: 1. reinforced concrete column; 2. composite beam; 3. beam-column joint; 4. friction damper; 11. lower column; 12. upper column; 21. precast beam; 22. composite layer; 23. keyway; 24. steel strand; 25. anchor end plate; 31. pier head steel bar; 41. T-shaped steel plate; 42. L-shaped steel plate; 211. non-prestressed section; 212. prestressed section; 241. embossed anchor end; 251. anchor groove; 411. wing plate; 412. web plate; 413. through groove; 421. short limb; 422. long limb; 423. through hole; 431. friction damping area; 432. adjusting bolt. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0031] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application 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 scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0032] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0033] Application Overview: The assembled steel strand anchored nodes in the prior art use steel strands as force-bearing bars. However, after the steel strands are tensioned and fixed, when the concrete is poured, the concrete will experience water loss and cement hydration during the curing process. Both of these factors may cause the concrete volume to shrink, which is the so-called shrinkage. Since the water evaporation rate and degree of hydration reaction in different areas of the concrete may be different, this uneven shrinkage may cause tiny cracks and voids in the concrete. In addition, in the process of releasing the tension force, the steel strands or steel bars will try to shrink, but due to the constraints of the concrete, they cannot actually shrink completely to their original length. Under the action of both, if these cracks and voids are around the steel strands, this will lead to a decrease in the bonding force between the steel strands and the concrete, and a bonding slip phenomenon will occur when the steel strands and concrete work together, and the prestressing effect of the steel strands will be reduced.

[0034] In order to solve the problem of cracking of beam-column joints in the above-mentioned prior art, the present invention provides a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure and a preparation process.

[0035] Example structure: like Figure 1 , 2 As shown, a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure comprises: The reinforced concrete column 1 comprises a lower column body 11 and an upper column body 12 .

[0036] A pair of composite beams 2 are arranged symmetrically around the central axis of the reinforced concrete column 1, and each composite beam 2 includes a precast beam 21 and a composite layer 22 cast on the precast beam 21. One end of the precast beam 21 close to the reinforced concrete column 1 is recessed inward to form a keyway 23, and the cross section of the keyway 23 is U-shaped. Three steel strands 24 are arranged in the precast beam 21, and each steel strand 24 extends from the bottom of the precast beam 21 to the outside of the keyway 23.

[0037] The beam-column node 3 is a modified concrete cast on the top end surface of the lower column 11 and in the keyway 23 , connecting the lower column 11 , the upper column 12 and the composite beam 2 .

[0038] The friction damper 4 is arranged on the side of the connection between the precast beam 21 and the lower column 11 , with one end fixed to the bottom surface of the precast beam 21 and the other end fixed to the side of the lower column 11 .

[0039] Hereinafter, the fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure will be described in detail.

[0040] like Figure 3 , 4 As shown, the friction damper 4 includes a T-shaped steel plate 41 and two L-shaped steel plates 42 respectively arranged on both sides of the T-shaped steel plate 41. The T-shaped steel plate 41 includes a wing plate 411 fixed to the prefabricated beam 21 by bolts and a web plate 412 perpendicular to the wing plate 411. The L-shaped steel plate 42 includes a short limb 421 fixed to the lower column 11 by bolts and a long limb 422 perpendicular to the short limb 421. The long limb 422 of the L-shaped steel plate 42 is slidably connected to the web plate 412 of the T-shaped steel plate 41 by bolts, and a friction damping area 431 is arranged on the contact surface between the long limb 422 and the web plate 412.

[0041] like Figure 3 , 4 As shown, a through slot 413 is provided at the center of the web 412 along the normal direction of the web 412, and three through holes 423 perpendicular to the through slot 413 are provided on the long limbs 422 on both sides of the web 412. Three adjusting bolts 432 matching the inner diameter of the through holes 423 are provided in the through slot 413, and the two ends of the adjusting bolts 432 pass through the through holes 423 on both sides of the through slot 413 and are fixed by nuts. The contact pressure between the T-shaped steel plate 41 and the L-shaped steel plate 42 is changed by adjusting the bolts 432 to adjust the friction force.

[0042] In a specific embodiment, a 2 mm thick PTFE (polytetrafluoroethylene) reinforced high friction composite material is provided on the friction damping area 431, the static friction coefficient of the material is greater than 0.4, and the dynamic friction coefficient is greater than 0.35, and the material is adhered to the contact surface between the long limb 422 and the web 412 by an adhesive. The composite material has excellent wear resistance and aging resistance, and can ensure that the friction damper 4 maintains stable friction performance during long-term use.

[0043] like Figure 2 As shown, the outer end of the steel strand 24 extending out of the keyway 23 is subjected to embossing anchor treatment to form an embossed anchor end 241. By embossing the end of the steel strand 24, the contact area and friction between the steel strand 24 and the concrete are increased.

[0044] like Figure 5As shown, the anchoring end plate 25 is a rectangular steel plate, and three equally spaced anchoring grooves 251 are arranged along the width direction of the anchoring end plate 25, and the width of the anchoring groove 251 matches the width of the steel strand 24. The anchoring end plate 25 is used to fix the three steel strands 24 in the three anchoring grooves 251 respectively to achieve anchoring and enhance the bonding performance between the steel strands and concrete. When assembling beams and columns, the flexibility of the steel strands is used within the keyway range to achieve free bending to avoid collision of the reinforcement bars at the beam-column node.

[0045] In a specific embodiment, the outer end of the steel strand 24 extending out of the keyway 23 is fixed in the keyway 23 of another oppositely arranged composite beam 2 through an anchoring end plate 25 .

[0046] like Figure 1 As shown, two pier head steel bars 31 are arranged in the beam-column joint 3. The two ends of the pier head steel bars 31 are respectively fixed by bolts in the key slots 23 of the composite beam 2 symmetrically arranged on both sides of the beam-column joint 3. The pier head steel bars 31 are combined with the beam-column joint 3 and the key slots 23 of the precast beam 21 to realize the plastic hinge transfer of the beam end. In a specific embodiment, the pier head steel bars 31 are steel bars with a diameter of mm.

[0047] like Figure 2 As shown, the area of ​​the precast beam 21 provided with the keyway 23 is the non-prestressed section 211, and the remaining part is the prestressed section 212. The steel strand 24 in the prestressed section 212 is pre-stressed and anchored in advance by the pre-tensioning method. The steel strand 24 in the non-prestressed section 211 is not prestressed. The stirrup spacing of the non-prestressed section 211 is smaller than the stirrup spacing of the prestressed section 212.

[0048] The modified concrete includes cement, quartz sand, mineral admixtures, polymer modifiers, water reducers, retarders, fibers and water. Among them, the cement is silicate cement; the quartz sand particle size is 0.016-1.25mm; the mineral admixtures include 20-40% silica fume, 20-40% slag and 40-60% fly ash by mass; the polymer modifier is polyacrylic acid emulsion; the water reducer is polycarboxyl water reducer, with a solid content greater than 20% and a water reduction rate greater than 29%; the retarder is sodium gluconate; the fibers include steel fibers and polypropylene fibers, the steel fibers have a diameter of 0.18-0.23mm, a length of 12-14mm, and a tensile strength greater than 2850Mpa; the polypropylene fibers have a diameter of 0.7-0.8mm and an aspect ratio of 40-45.

[0049] In a specific embodiment, the cement is PO 52.5 grade silicate cement; the quartz sand includes coarse-grained sand of 1.25-0.63 mm, medium-grained sand of 0.63-0.315 mm and fine-grained sand of 0.315-0.016 mm; the mineral admixtures include 400 mesh silica fume, S95 grade slag and grade II fly ash; the polycarboxyl water reducer has a solid content of 21% and a water reduction rate of 31%; the steel fiber has a diameter of 0.20 mm, a length of 12 mm and a tensile strength of 2880 MPa; the polypropylene fiber has a diameter of 0.7 mm and an aspect ratio of 40-45.

[0050] Each cubic meter of modified concrete includes 700-800kg of silicate cement, 1000-1200kg of quartz sand, 140-200kg of mineral admixtures, 80-120kg of polyacrylic acid emulsion, 30-60kg of polycarboxyl water reducer, 20-40kg of sodium gluconate, 120-150kg of steel fiber, 0.5-1.5kg of polypropylene fiber and 120-150kg of water.

[0051] Exemplary Process: like Figure 6 As shown, a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure preparation process is used to prepare the above-mentioned reinforced concrete structure, comprising the following steps: S1. Prepare the lower column: according to the design drawings, tie the steel bars into the lower column skeleton; install the formwork according to the size and shape of the lower column; pour the concrete in layers, vibrate and compact it, and remove bubbles; after the concrete has initially set, maintain it and keep it moist until it reaches the designed strength.

[0052] S2. Preparation of precast beams: according to the design dimensions of the precast beams, a precast beam mould is made, and a steel skeleton and steel strands are placed in the mould according to the design requirements, with keyway positions reserved; for the steel strands in the prestressed section, prestress is applied by the pre-tensioning method; concrete is poured in layers, vibrated to compact it, and air bubbles are removed; after pouring, it is cured, and the concrete strength is removed from the mould after reaching the design standard to obtain the precast beam.

[0053] S3. Hoist the precast beam and install the friction damper: Use the lifting equipment to hoist the precast beam to the designated position, and ensure that the precast beam is accurately docked with the lower column; install the friction damper at the connection between the precast beam and the lower column, ensure that the T-shaped steel plate and the L-shaped steel plate are tightly fixed, and adjust the damping of the friction damper by adjusting the bolts.

[0054] S4. Perform embossed anchor treatment and install anchor end plates and pier head reinforcement: perform embossed anchor treatment on the outer end of the steel strand extending out of the keyway to form an embossed anchor end; fix the embossed steel strand in the anchor groove of the anchor end plate; fix the two ends of the pier head reinforcement in the keyways of the composite beams on both sides respectively.

[0055] S5. Casting beam-column joints: Install formwork at the top of the lower column and the connection between the precast beams, prepare modified concrete materials according to the mix ratio of modified concrete; use modified concrete to fill the internal space of the formwork, vibrate during the pouring process to ensure that the concrete is dense and free of voids; after pouring, perform maintenance until the concrete reaches the designed strength.

[0056] S6. Casting the superimposed layer: Use concrete to cast the superimposed layer, ensuring that the concrete covers the stirrups in the superimposed layer of the precast beam; after casting, the superimposed layer is cured.

[0057] S7. Casting of the upper column: Tie up the structural reinforcement according to the design drawings, and install the formwork according to the size and shape of the upper column; cast the concrete in layers, vibrate and compact it, and remove air bubbles; after the concrete has initially set, cure it and keep it moist until it reaches the designed strength.

[0058] Comparative Example 1 A modified concrete, the mix ratio is shown in Table 1 below: Table 1 Mix ratio selection table (kg / m³)

[0059] The concrete with the above mix ratio was tested with reference to the "Concrete Engineering Construction Quality Acceptance Code" (GB 50204-2015) and the "Standard for Test Methods for Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), and the results are shown in Table 2: Table 2 Concrete performance strength

[0060] As shown in Table 1 and Table 2, with the increase of the amount of polyacrylic acid emulsion added (from 0 to 120kg / m³, represented by numbers 1 to 4), the slump and air content gradually increase; when the amount of polyacrylic acid emulsion added increases from 0 to 80kg / m³ (numbers 1 to 3), the compressive strength gradually increases; but when the amount of addition continues to increase to 120kg / m³ (number 4), the compressive strength decreases instead; the change trend of flexural strength is similar to that of compressive strength, which increases first and then decreases. This is because polyacrylic acid emulsion can improve the workability of concrete and make it more fluid. At the same time, because polyacrylic acid emulsion forms tiny bubbles in concrete, the air content is increased. In addition, an appropriate amount of polyacrylic acid emulsion can optimize the internal structure of concrete, fill the pores in concrete, and improve the density of concrete, thereby enhancing its compressive strength and flexural strength. However, excessive addition leads to too many bubbles inside the concrete, which will become defects inside the concrete and reduce the strength of the concrete.

[0061] Taking into account the changes in compressive strength and flexural strength, the optimal amount of polyacrylic acid emulsion should be around 80kg / m³ (the amount corresponding to No. 3). This is because an appropriate amount of polyacrylic acid emulsion can significantly improve the strength and durability of concrete, while excessive addition may lead to performance degradation. The reason for the effect of increasing first and then decreasing may be that too many additives interfere with the hydration process of cement or form too many bubbles, thereby affecting the mechanical properties of concrete.

[0062] Comparative Example 2 A modified concrete, the mix ratio is shown in Table 3 below: Table 3 Mix ratio selection table (kg / m³)

[0063] The concrete with the above mix ratio was tested with reference to the "Concrete Engineering Construction Quality Acceptance Code" (GB 50204-2015) and the "Concrete Physical and Mechanical Properties Test Method Standard" (GB / T 50081-2019), and the results are shown in Table 4: Table 4 Concrete performance strength

[0064] According to Table 3 and Table 4, with the increase of the amount of polypropylene fiber added (from 0 to 1.5 kg / m³, represented by numbers 3, 5, 6, and 7), the slump gradually decreases, and the change of air content is not obvious. When the amount of polypropylene fiber added increases from 0 to 1.0 kg / m³ (numbers 3 to 6), the compressive strength gradually increases; but when the amount added continues to increase to 1.5 kg / m³ (number 7), the compressive strength decreases slightly; the change trend of flexural strength is similar to that of compressive strength, which also increases first and then decreases, and reaches the maximum value when the amount added is 1.0 kg / m³. This is because the addition of polypropylene fiber can improve the crack resistance and toughness of concrete, and the appropriate amount of fiber can form an effective support network in concrete, thereby improving its compressive strength and flexural strength. With the increase of fiber addition, the interfacial bonding between fiber and cement matrix is ​​enhanced, which helps to transfer stress and thus improve the strength of concrete. However, when the amount of fiber added is too much, the fiber is unevenly dispersed and agglomerated, resulting in weak links inside the concrete, which reduces the strength of the concrete. In addition, too many fibers hinder the close packing of cement particles, affecting the density of concrete and thus its strength.

[0065] Taking into account the changes in compressive strength and flexural strength, the optimal range of polypropylene fiber addition should be around 1.0kg / m³ (the amount corresponding to No. 6). This is because an appropriate amount of polypropylene fiber can significantly improve the crack resistance and durability of concrete, while too much fiber may lead to construction difficulties, performance degradation or cost increase. The reason for the effect of increasing first and then decreasing may be that too many fibers form too many interfaces in concrete, increase interface defects, and thus affect the mechanical properties of concrete. At the same time, too many fibers may also lead to uneven stress distribution inside concrete, reducing the overall strength.

[0066] Example 1

[0067] like Figure 1-5 A fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure shown is prepared using the above exemplary process.

[0068] In this embodiment, the size of the lower column is 550mm×550mm×1000mm; the size of the composite beam is 300mm×500mm×2000mm, among which the composite layer height is 120mm, the keyway length is 400mm, the prestressed section stirrup spacing is 150mm, and the non-prestressed section stirrup spacing is 100mm; the diameters of the three steel strands are 12.7mm, the yield force is 191.0kN, the yield strength is 1625.3MPa, the tensile strength is 1928.8MPa, the elastic modulus is 194.8GPa, and the elongation is 4.56%; the size of the upper column is 550mm×550mm×1300mm.

[0069] The mix ratio of the modified concrete for the beam-column joint in this embodiment is 711kg P.O 52.5 grade silicate cement, 183kg coarse sand quartz sand, 776kg medium sand quartz sand, 183kg fine sand quartz sand, 58kg 400 mesh silica fume, 58kg S95 grade slag, 90kg II grade fly ash, 80kg polyacrylic acid emulsion, 45kg polycarboxyl water reducer, 20kg sodium gluconate, 150kg steel fiber, 1.0kg polypropylene fiber and 120kg water per cubic meter.

[0070] Example 2

[0071] Different from the first embodiment, the reinforced concrete structure in this embodiment is not provided with a friction damper.

[0072] Example 3

[0073] Different from Example 1, the reinforced concrete structure beam-column joint in this embodiment is cast with C40 concrete.

[0074] Example 4

[0075] Different from the third embodiment, the reinforced concrete structure in this embodiment is not provided with a friction damper.

[0076] Destruction experiment The reinforced concrete structural components in Examples 1-4 were placed in a load loading device in turn for a destructive test. Among them, a 320t hydraulic jack was set at the top of the column, and the axial compression ratio was 0.2; a 60t unidirectional jack was set at the end of the composite beams on both sides, and an antisymmetric load was applied to the beam end through an oil pump. The experiment adopted a force and displacement mixed loading control method. In the elastic stage, load control loading was adopted, and each loading cycle was performed once. After the specimen yielded, displacement control loading was adopted, and each level of displacement load was cycled 3 times. The loading was carried out until the load dropped to 85% of the ultimate load. The experimental results are shown in the following table: Table 5 Destruction test results

[0077] According to Table 5, the maximum load (151 kN) of Example 1 is significantly higher than that of Example 2 (143 kN), and the cracking load is also slightly higher; the maximum load (133 kN) of Example 3 (with high-performance concrete but without friction damper) is higher than the maximum load (121 kN) of Example 4 (with high-performance concrete and without friction damper). This is because when the structure deforms, the friction components inside the friction damper will generate resistance, converting part of the energy into heat energy, thereby reducing the energy transferred to the main body of the structure, reducing the vibration amplitude and acceleration of the structure, and thus improving the bearing capacity and seismic performance of the structure.

[0078] According to Table 5, the maximum load of Example 1 (151 kN) is also significantly higher than that of Example 3 (133 kN), and the cracking load is also higher. This is because, compared with ordinary concrete, the modified concrete in Example 1 reduces the volume change of concrete during the curing process through polyacrylic acid emulsion and polypropylene fiber, achieves low shrinkage, and effectively reduces the stress caused by volume change inside the concrete, thereby reducing the impact on the bonding force of the steel strand. In addition, the tension caused by the shrinkage of concrete under stress will generate friction at the interface to resist relative displacement. The shrinkage of the modified concrete in Example 1 causes tiny gaps to appear at the interface, and the larger normal pressure can still maintain sufficient friction to prevent the steel strand from slipping significantly.

[0079] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure, characterized in that: include: A reinforced concrete column (1) comprising a lower column body (11) and an upper column body (12); A composite beam (2), wherein a pair of composite beams (2) are arranged relative to the reinforced concrete column (1), each composite beam (2) comprising a precast beam (21) and a composite layer (22) cast on the precast beam (21); one end of the precast beam (21) close to the reinforced concrete column (1) is recessed inward to form a keyway (23), and the cross-section of the keyway (23) is U-shaped; a steel strand (24) is arranged in the precast beam (21), and the steel strand (24) extends from the inner bottom of the precast beam (21) to the outside of the keyway (23); A beam-column node (3) is formed by pouring modified concrete on the top end surface of the lower column (11) and in the keyway (23), connecting the lower column (11), the upper column (12) and the composite beam (2); A friction damper (4) is arranged on the side of the connection between the prefabricated beam (21) and the lower column (11), one end of which is fixed to the bottom surface of the prefabricated beam (21) and the other end of which is fixed to the side of the lower column (11); The modified concrete comprises cement, quartz sand, mineral admixtures, polymer modifiers, water reducers, retarders, fibers and water; the cement is silicate cement; the quartz sand has a particle size of 0.016-1.25 mm; the mineral admixtures include silica fume with a mass fraction of 20-40%, slag with a mass fraction of 20-40% and fly ash with a mass fraction of 40-60%; the polymer modifier is polyacrylic acid emulsion; the water reducer is a polycarboxyl water reducer with a solid content of more than 20% and a water reduction rate of more than 29%; the retarder is sodium gluconate; the fibers include steel fibers and polypropylene fibers, the steel fibers have a diameter of 0.18-0.23 mm, a length of 12-14 mm, and a tensile strength of more than 2850 MPa, and the polypropylene fibers have a diameter of 0.7-0.8 mm and an aspect ratio of 40-45; The modified concrete comprises 700-800kg of silicate cement, 1000-1200kg of quartz sand, 140-200kg of mineral admixture, 80-120kg of polyacrylic acid emulsion, 30-60kg of polycarboxyl water reducer, 20-40kg of sodium gluconate, 120-150kg of steel fiber, 0.5-1.5kg of polypropylene fiber and 120-150kg of water per cubic meter.

2. A fiber-reinforced ultra-high strength and ultra-toughness reinforced concrete structure according to claim 1, characterized in that: The friction damper (4) comprises a T-shaped steel plate (41) and two L-shaped steel plates (42) respectively arranged on both sides of the T-shaped steel plate (41); wherein the T-shaped steel plate (41) comprises a wing plate (411) fixed to the prefabricated beam (21) by bolts and a web plate (412) perpendicular to the wing plate (411); the L-shaped steel plate (42) comprises a short limb (421) fixed to the lower column (11) by bolts and a long limb (422) perpendicular to the short limb (421); the long limb (422) of the L-shaped steel plate (42) is slidably connected to the web plate (412) of the T-shaped steel plate (41) by bolts, and a friction damping area (431) is arranged on the contact surface between the long limb (422) and the web plate (412).

3. A fiber-reinforced ultra-high strength and ultra-toughness reinforced concrete structure according to claim 2, characterized in that: A through slot (413) is provided at the center of the web (412) along the normal direction of the web (412), and through holes (423) perpendicular to the direction of the through slot (413) are provided on the long limbs (422) on both sides of the web (412) respectively; an adjusting bolt (432) matching the inner diameter of the through hole (423) is provided in the through slot (413), and two ends of the adjusting bolt (432) respectively pass through the through holes (423) located on both sides of the through slot (413) and are fixed by nuts.

4. The fiber-reinforced ultra-high strength and ultra-toughness reinforced concrete structure according to claim 1, characterized in that: The outer end of the steel strand (24) extending out of the keyway (23) is subjected to embossed anchor processing to form an embossed anchor end (241).

5. The fiber-reinforced ultra-high strength and ultra-toughness reinforced concrete structure according to claim 4, characterized in that: The outer end of the steel strand (24) extending out of the keyway (23) is fixed in the keyway (23) of another oppositely arranged composite beam (2) via an anchoring end plate (25); the anchoring end plate (25) is a rectangular steel plate and is provided with an anchoring groove (251) along the width direction, the width of the anchoring groove (251) matching the width of the steel strand (24).

6. The fiber-reinforced ultra-high strength and ultra-toughness reinforced concrete structure according to claim 5, characterized in that: A pier head steel bar (31) is arranged in the beam-column node (3); two ends of the pier head steel bar (31) are respectively anchored in keyways (23) of the composite beams (2) on both sides of the beam-column node (3).

7. The fiber-reinforced ultra-high strength and ultra-toughness reinforced concrete structure according to claim 1, characterized in that: The area of ​​the prefabricated beam (21) provided with the keyway (23) is a non-prestressed section (211), and the remaining part is a prestressed section (212); the steel strands (24) located in the prestressed section (212) are pre-stressed and anchored in advance by using a pre-tensioning method; the steel strands (24) located in the non-prestressed section (211) are not prestressed; and the spacing of the stirrups in the non-prestressed section (211) is smaller than the spacing of the stirrups in the prestressed section (212).

8. A process for preparing a fiber-reinforced ultra-high-strength and ultra-toughness reinforced concrete structure, based on the reinforced concrete structure according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, prepare the lower column; S2, preparing prefabricated beams; S3, hoisting precast beams and installing friction dampers; S4, perform embossed anchor processing, and install anchor end plates and pier head steel bars; S5, pouring beam-column joints; S6, pouring the superimposed layer; S7. Cast the upper column.

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