High ductility full FRP bar concrete beam containing FRP rectangular tube and construction method
By using a combination of FRP rectangular tubes and square stirrups to constrain FRP-reinforced concrete beams, the problems of easy corrosion of traditional reinforced concrete and poor ductility of FRP-reinforced concrete are solved, thereby improving the load-bearing and deformation capacity of the beams and making them suitable for marine engineering.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INSTITUTE OF TECHNOLOGY (SHENZHEN) (INSTITUTE OF SCIENCE AND TECHNOLOGY INNOVATION HARBIN INSTITUTE OF TECHNOLOGY SHENZHEN)
- Filing Date
- 2023-06-27
- Publication Date
- 2026-06-23
AI Technical Summary
Traditional reinforced concrete beams are prone to corrosion in alkaline environments, FRP-reinforced concrete composite structures have poor ductility under seismic loads, and the insufficient confinement area of FRP spiral reinforcement leads to inadequate concrete compaction.
FRP rectangular tubes are used to replace FRP spiral stirrups. The combination of FRP square stirrups and rectangular tubes constrains the compression zone, increases the constrained area, and through holes are set on the rectangular tubes to facilitate concrete vibration.
It improves the load-bearing capacity and deformation capacity of FRP-reinforced concrete beams, avoids the problem of inadequate concrete vibration, and prevents FRP reinforcement corrosion, making it suitable for marine environments.
Smart Images
Figure CN116607704B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of structural engineering, specifically relating to a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes and its construction method. Background Technology
[0002] For traditional reinforced concrete beams, the alkaline environment inside the concrete can protect the reinforcing steel, but it is not enough to prevent corrosion. Under conditions such as insufficient concrete cover thickness, loose pouring, and high relative humidity, the intrusion of corrosive media such as chlorides and sulfides poses a severe challenge to the corrosion protection of the reinforcing steel. In particular, in the core area of frame joints with complex stress distribution and significant stress concentration, corrosion problems further exacerbate the vulnerability of the connection area, threatening the long-term safety of the structure and becoming the primary cause of functional degradation in old building structures.
[0003] Fiber-reinforced polymer (FRP) composites are materials composed of fiber reinforcements and a resin matrix. FRP products used in new civil engineering structures mainly include FRP bars, FRP pipes, and FRP profiles. Compared to traditional structural materials, FRP has advantages such as lightweight, high strength, good corrosion resistance, and high design flexibility. However, FRP exhibits linear elastic behavior and lacks a yield plateau, resulting in no obvious yield characteristics before component failure. This further leads to poor ductility of FRP-reinforced concrete composite structures under seismic loads, raising concerns about the feasibility of using FRP-reinforced concrete composite structures in seismically active regions.
[0004] Patent number "202111413342.2" discloses a fully FRP-reinforced high-ductility beam made of seawater sand concrete and its application. By using FRP spiral reinforcement to effectively constrain the concrete in the compression zone of the beam, a compressive yield plastic hinge with good deformation capacity is formed in the compression area, transforming the beam from a sudden brittle failure to a ductile failure process with signs of impending failure. However, the constrained area in the compression zone of this high-ductility beam is insufficient, resulting in a weak confinement effect. Furthermore, the excessively dense pitch of the FRP spiral reinforcement can prevent the concrete vibrator from reaching the core for proper compaction. Summary of the Invention
[0005] The purpose of this invention is to provide a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes and a construction method thereof. By setting the FRP tubes inside the concrete beam as rectangular tubes, the constraint area and constraint effect of the compression zone can be increased, and the situation where the concrete vibrator cannot be inserted to compact the concrete due to the excessively dense pitch of the FRP spiral stirrups can be avoided, thus solving the problems in the background art.
[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:
[0007] A high-ductility, fully FRP-reinforced concrete beam containing an FRP rectangular tube includes FRP square stirrups and a first FRP rectangular tube. The interior of each FRP square stirrup forms a rectangular receiving surface. The width of the receiving surface is the same as the width of the cross-section of the first FRP rectangular tube, and the length of the receiving surface is greater than the length of the cross-section of the first FRP rectangular tube. Multiple FRP square stirrups are equally spaced around the outside of the first FRP rectangular tube, and the receiving surface of each FRP square stirrup is perpendicular to the tube axis of the first FRP rectangular tube. Each FRP square stirrup is fixedly connected to the outer top wall, left side wall, and right side wall of the first FRP rectangular tube.
[0008] By setting up FRP rectangular tubes and constraining them with FRP square stirrups, the compression zone of the high-ductility fully FRP reinforced concrete beam is formed through the FRP rectangular tubes. The compression zone formed in this way is larger than that formed by FRP spiral stirrups in the prior art, thereby improving the constraint area and constraint effect of the compression zone. This effectively avoids the situation where the concrete vibrator cannot penetrate and compact the concrete due to the excessively dense pitch of the FRP spiral stirrups.
[0009] Preferably, a first FRP tension longitudinal bar is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup; the first FRP tension longitudinal bar is arranged along the tube axis of the first FRP rectangular tube and is perpendicular to the receiving surface of each FRP square stirrup; the first FRP tension longitudinal bar and each FRP square stirrup are fixedly connected and located below the outer bottom wall of the first FRP rectangular tube; a constraint zone is provided between the first FRP tension longitudinal bar and the outer bottom wall of the first FRP rectangular tube; the constraint zone is filled with concrete.
[0010] Preferably, the first FRP rectangular tube has openings at both ends; the high-ductility fully FRP reinforced concrete beam further includes FRP reinforcing bars; the FRP reinforcing bars are fixedly disposed on the inner top wall of the first FRP rectangular tube, and a first compression zone is formed between the FRP reinforcing bars and the inner bottom wall of the first FRP rectangular tube; the first compression zone is filled with concrete.
[0011] Preferably, the length of the receiving surface is equal to twice the length of the cross-section of the first FRP rectangular tube; a second FRP rectangular tube is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup; each of the FRP square stirrups is fixedly connected to the outer bottom wall, left side wall, and right side wall of the second FRP rectangular tube; the outer top wall of the second FRP rectangular tube is in contact with the outer bottom wall of the first FRP rectangular tube.
[0012] Preferably, the high-ductility fully FRP reinforced concrete beam further includes a second FRP tensile longitudinal bar; the second FRP rectangular tube has openings at both ends; the second FRP tensile longitudinal bar is fixedly disposed on the inner bottom wall of the second FRP rectangular tube, and a second compression zone is formed between the second FRP tensile longitudinal bar and the inner bottom wall of the second FRP rectangular tube; the second compression zone is filled with concrete.
[0013] Preferably, the top wall of the first FRP rectangular tube is provided with a plurality of through holes at equal intervals along its tube axis, and there is one first through hole between every two adjacent FRP square stirrups; the bottom wall of the first FRP rectangular tube is provided with a plurality of through holes at equal intervals along its tube axis, and there is one second through hole between every two adjacent FRP square stirrups; the number of first through holes and second through holes is the same and their positions correspond one-to-one.
[0014] Preferably, the left or right side wall of the first FRP rectangular tube is provided with a plurality of through third through holes at equal intervals along its tube axis, and there is one third through hole between every two adjacent FRP square stirrups; the left or right side wall of the second FRP rectangular tube is provided with a plurality of through fourth through holes at equal intervals along its tube axis, and there is one fourth through hole between every two adjacent FRP square stirrups.
[0015] Preferably, the high-ductility fully FRP reinforced concrete beam further includes a protective layer; the protective layer encloses the FRP square stirrups and the first FRP rectangular tube.
[0016] Preferably, the distance between the first FRP rectangular tubes along the width direction of the cross section is l1; the distance between the first FRP rectangular tubes along the height direction of the cross section is l2, and l2 = 1.0l1 to 1.2l1; the outer chamfer radius of the first FRP rectangular tubes and the inner chamfer radius of the FRP square stirrups are the same.
[0017] The present invention also provides a construction method for a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes, comprising the aforementioned high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes; the construction method further comprises the following steps:
[0018] Step S1. Set the first spacing value, and space multiple FRP support ribs according to the first spacing value and fix them to the inner top wall of the first FRP rectangular tube;
[0019] Step S2. Set the second spacing value, and tie multiple FRP square stirrups to the outside of the first FRP rectangular tube according to the second spacing value. Each FRP square stirrup is fixedly connected to the outer top wall, left side wall and right side wall of the first FRP rectangular tube.
[0020] Step S3. Set the third spacing value, and space multiple first FRP tension longitudinal bars according to the third spacing value and set them between the outer bottom wall of the first FRP rectangular tube and the FRP square stirrups, and fix them to the FRP square stirrups;
[0021] Step S4. After multiple FRP square stirrups are tied to the first FRP rectangular tube, an FRP reinforcement cage is formed; the FRP reinforcement cage is placed into the casting mold and fixed in place;
[0022] Step S5. Pour concrete into the FRP reinforcement cage in the casting mold and tamp and vibrate it until it is compacted to obtain the casting specimen;
[0023] Step S6. Set the curing period. After the cast specimen has reached the curing period, remove the casting mold to obtain a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes.
[0024] The present invention provides a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes and a construction method thereof, which, compared with the prior art, have the following advantages:
[0025] 1. Based on a conventional fully FRP reinforced concrete beam, the concrete in the compression zone of the beam is constrained, resulting in enhanced load-bearing capacity and deformation capacity under bending moment, and significantly improved section ductility. In bending tests, the load-displacement curve of this easily cast, high-ductility fully FRP reinforced concrete beam does not exhibit the sudden drop after peak load seen in ordinary concrete beams.
[0026] 2. Compared with the method of confining the compression zone by FRP spiral stirrups, the rectangular FRP tubes confine the concrete in the compression zone of the FRP longitudinal reinforcement, which to some extent alleviates the phenomenon of compression buckling of the longitudinal reinforcement in the compression zone and improves the load-bearing capacity of the component.
[0027] 3. The perforations in the FRP rectangular tubes facilitate concrete pouring and vibration when the beam reinforcement cage is located behind the formwork during actual construction, and the perforation diameter is larger than that of ordinary vibrators. Compared to the FRP spiral stirrup restraint method, using perforated FRP rectangular tubes to restrain the concrete in the compression zone effectively avoids the situation where the concrete vibrator cannot reach in and compact the concrete due to the excessively dense pitch of the FRP spiral stirrups.
[0028] 4. The entire component does not use steel reinforcement, which effectively avoids the reduction of the component's load-bearing capacity or even premature failure caused by steel corrosion. It is suitable for marine environments with corrosive media such as chlorides and sulfides, and proposes a new type of beam cross-section for marine engineering.
[0029] 5. FRP rectangular tubes are used to confine the concrete in the compression zone. The FRP rectangular tubes can be opened on one side for lateral pouring. Within the confinement range of the FRP rectangular tubes, rubber concrete, which has lower stiffness and better ductility than ordinary concrete, can be poured locally to enhance the deformation capacity of the concrete in the compression zone of the beam section in the later stage of load bearing, and further achieve the design goal of high ductility. Attached Figure Description
[0030] Figure 1 The figure shown is a cross-sectional schematic diagram of a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes according to Embodiment 1.
[0031] Figure 2 The diagram shown is a structural diagram of the FRP square stirrups in a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes, according to Embodiment 1.
[0032] Figure 3 The figure shown is a schematic diagram of the longitudinal section of a high-ductility all-FRP reinforced concrete beam containing FRP rectangular tubes according to Embodiment 1.
[0033] Figure 4 As shown Figure 1 A schematic diagram of the first FRP rectangular tube;
[0034] Figure 5 The diagram shown is a schematic diagram of the bundled FRP reinforcement cage of a high-ductility all-FRP reinforced concrete beam containing FRP rectangular tubes according to Embodiment 1.
[0035] Figure 6 The diagram shown is a schematic diagram of a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes after casting, according to Embodiment 1.
[0036] Figure 7 The diagram shown is a schematic diagram of the first FRP rectangular tube in a high-ductility fully FRP reinforced concrete beam containing an FRP rectangular tube according to Embodiment 2.
[0037] Figure 8 The diagram shown is a schematic of the bundled FRP reinforcement cage of a high-ductility all-FRP reinforced concrete beam containing FRP rectangular tubes according to Embodiment 2.
[0038] Figure 9 The diagram shown is a schematic diagram of a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes after casting, according to Embodiment 2.
[0039] Figure 10 The diagram shown is a schematic of the bundled FRP reinforcement cage of a high-ductility all-FRP reinforced concrete beam containing FRP rectangular tubes according to Embodiment 3.
[0040] Figure 11The diagram shown is a schematic diagram of a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes after casting, according to Example 3.
[0041] Figure 12 The diagram shows a flowchart of a construction method for a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes, according to Embodiment 1.
[0042] Figure label:
[0043] 1. Protective layer; 2. FRP support reinforcement; 3. First FRP rectangular tube; 4. FRP square stirrup; 5. First FRP tensile longitudinal reinforcement; 6. First compression zone; 7. Constraint zone; 8. First through hole; 9. Third through hole; 10. Second FRP rectangular tube; 11. Second compression zone; 12. Fourth through hole. Detailed Implementation
[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.
[0045] The technical solution of the present invention will be described in detail below with specific embodiments.
[0046] Example 1
[0047] like Figures 1-6 As shown, this embodiment of a high-ductility fully FRP-reinforced concrete beam containing FRP rectangular tubes includes FRP square stirrups 4 and a first FRP rectangular tube 3; the interior of the FRP square stirrups 4 forms a rectangular receiving surface; the width of the receiving surface is the same as the width of the cross-section of the first FRP rectangular tube 3, and the length of the receiving surface is greater than the length of the cross-section of the first FRP rectangular tube 3; multiple FRP square stirrups 4 are equally spaced on the outside of the tube body of the first FRP rectangular tube 3, and the receiving surface of each FRP square stirrup 4 is perpendicular to the tube axis of the first FRP rectangular tube 3; each FRP square stirrup 4 is fixedly connected to the outer top wall, left side wall, and right side wall of the first FRP rectangular tube 3.
[0048] Preferably, a first FRP tension longitudinal bar 5 is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup 4; the first FRP tension longitudinal bar 5 is provided along the tube axis of the first FRP rectangular tube 3 and is perpendicular to the receiving surface of each FRP square stirrup 4.
[0049] Preferably, the first FRP tensile longitudinal reinforcement 5 and each FRP square stirrup 4 are fixedly connected and located below the outer bottom wall of the first FRP rectangular tube 3; a constraint zone 7 is provided between the first FRP tensile longitudinal reinforcement 5 and the outer bottom wall of the first FRP rectangular tube 3; the constraint zone 7 is filled with concrete.
[0050] Preferably, the first FRP rectangular tube 3 has openings at both ends; the high-ductility all-FRP reinforced concrete beam also includes FRP reinforcing bars 2; the FRP reinforcing bars 2 are fixedly installed on the inner top wall of the first FRP rectangular tube 3, and a first compression zone 6 is formed between the FRP reinforcing bars 2 and the inner bottom wall of the first FRP rectangular tube 3; the first compression zone 6 is filled with concrete.
[0051] Preferably, the top wall of the first FRP rectangular tube 3 is provided with a plurality of through holes 8 at equal intervals along its tube axis, and there is a first through hole 8 between every two adjacent FRP square stirrups 4; the bottom wall of the first FRP rectangular tube 3 is provided with a plurality of through holes 8 at equal intervals along its tube axis, and there is a second through hole between every two adjacent FRP square stirrups 4; the number of first through holes 8 and second through holes is the same and their positions correspond one-to-one.
[0052] Preferably, the high-ductility fully FRP reinforced concrete beam further includes a protective layer 1; the protective layer 1 encloses the FRP square stirrups 4 and the first FRP rectangular tube 3.
[0053] This embodiment describes a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes, such as... Figure 1 As shown, the beam cross-section dimensions are 250*450mm, and the total beam length is 3000mm. The width of protective layer 1 is 25mm. Figure 2 As shown, the FRP square stirrup 4 has an outer width of 200mm, an outer height of 400mm, a diameter of 13mm, and an inner chamfer radius of 40mm; and both chamfers on the same side of the FRP square stirrup 4 are provided with lap sections.
[0054] The specific reinforcement information of the beam is as follows: The confinement zone 7 of the high ductility all-FRP reinforced concrete beam is equipped with a first FRP tension longitudinal bar 5 with a diameter of 19mm, specifically a glass fiber tension longitudinal bar with an elastic modulus of approximately 50GPa and a fracture strain of approximately 0.0176. The first FRP tension longitudinal bar 5 is made of epoxy resin or vinyl ester resin, and its surface is sandblasted after the resin of the first FRP tension longitudinal bar 5 has cured.
[0055] The first compression zone 6 of the high-ductility all-FRP reinforced concrete beam is equipped with FRP stirrups 2 with a diameter of 13mm, specifically glass fiber reinforcement used as stirrups, with an elastic modulus of about 50GPa and a fracture strain of about 1.80%. The FRP stirrups 2 are also made of epoxy resin or vinyl ester resin, and the surface of the FRP stirrups 2 is sandblasted after the resin has cured.
[0056] The FRP square stirrup 4 uses 13mm diameter GFRP bars to position the longitudinal GFRP bars and form an FRP reinforcement skeleton to resist the actual shear force borne by the beam. The inner chamfer radius of the FRP square stirrup 4 meets the requirements of the fiber reinforced composite material specification, not less than 3 times the stirrup diameter, and is taken as 40mm. The FRP square stirrup 4 is also made of epoxy resin or vinyl ester resin, and its surface is sandblasted after the resin of the FRP square stirrup 4 has cured. The lap length of the FRP square stirrup 4 meets the specification requirements, not less than 12 times the bar diameter. To simplify the manufacturing process, the FRP square stirrup 4 adopts a half-length lap method, and the lap range includes the two corners on the same side, which meets the force transmission requirements of the stirrup lap.
[0057] The pitch of the FRP square stirrups 4 is selected as follows: the spacing of the stirrups in the dense zone near the beam end is selected as 80mm to improve the shear bearing capacity of the GFRP stirrups in the dense zone. The length of the dense zone is about 500mm from the beam end. The spacing of the stirrups in the non-dense zone is selected as 100mm to meet the requirements of shear bearing capacity, overall stiffness and stability of the component.
[0058] The dimensions of the first FRP rectangular tube 3 in this embodiment are as follows: the outer chamfer radius of the first FRP rectangular tube 3 should be matched with the inner chamfer radius of the FRP square stirrup 4, which is 40mm, to achieve sufficient restraint of the concrete in the compression zone. Compared with the method of restraining the compression zone using FRP spiral stirrups in the prior art, this embodiment uses the first FRP rectangular tube 3 to restrain the concrete in the compression zone, further enhancing the restraint area and restraint effect. The fiber winding angle of the first FRP rectangular tube 3 is selected as 80 degrees to achieve a good circumferential restraint effect on the concrete inside the tube; the thickness of the first FRP rectangular tube 3 is selected as 6mm, which enhances the restraint effect on the concrete in the compression zone of the beam and also avoids material waste to a certain extent. The diameters of the first through hole 8 and the second through hole of the first FRP rectangular tube 3 are both 55mm, and the hole spacing is matched with the spacing of the FRP square stirrup 4.
[0059] Specifically, in this embodiment, the inner chamfer radius of the first FRP rectangular tube 3 and the FRP square stirrup 4 shall not be less than three times the diameter of the FRP square stirrup 4. The dimensions of the first FRP rectangular tube 3 should be adapted to the dimensions of the FRP square stirrup 4 to achieve the maximum restraint effect.
[0060] Specifically, the dimensions of the first FRP rectangular tube 3 in this embodiment should be determined based on the internal clear distance of the FRP square stirrups 4, taking into account the 5mm dimensional error of the stirrups due to sandblasting.
[0061] Specifically, such as Figure 1 and 4As shown, in this embodiment, the distance along the width direction of the first FRP rectangular tube 3 is l1 = 165mm, and the outer chamfer radius is selected to be the same as the inner chamfer radius of the FRP square stirrup 4, which is 40mm, so as to achieve a smooth transition in the chamfer area, thereby achieving good constraint of the first FRP rectangular tube 3 on the concrete of the compression core area; at the same time, the distance along the height direction of the first FRP rectangular tube 3 is l2 = 1.0l1~1.2l1, and in this example, it is preferably 170mm.
[0062] Specifically, in this embodiment, the first FRP rectangular tube 3 is a bending member, satisfying the requirements of the plane section assumption. Under bending moment, according to the plane section assumption, in the initial elastic stage, the neutral axis of the section is close to the beam axis. As the concrete cracks in the tension zone develop, the neutral axis of the beam section gradually moves upward, and the height of the compression zone gradually decreases. Therefore, the distance l2 of the first FRP rectangular tube 3 along the section height direction should not be too long. At the same time, the length of the first FRP rectangular tube 3 is adapted to the length of the first FRP tension longitudinal reinforcement 5 and is not affected by its own section width and height.
[0063] Using the above reinforcement scheme, this embodiment also provides a construction method for a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes; such as Figure 12 As shown, the construction method includes the following steps:
[0064] Step S1. Set the first spacing value, and space the multiple FRP support ribs 2 according to the first spacing value and fix them to the inner top wall of the first FRP rectangular tube 3;
[0065] Step S2. Set the second spacing value, and space multiple FRP square stirrups 4 according to the second spacing value and tie them to the outside of the first FRP rectangular tube 3. Each FRP square stirrup 4 is fixedly connected to the outer top wall, left side wall and right side wall of the first FRP rectangular tube 3.
[0066] Step S3. Set the third spacing value, and space multiple first FRP tension longitudinal bars 5 according to the third spacing value and set them between the outer bottom wall of the first FRP rectangular tube 3 and the FRP square stirrups 4, and fix them to the FRP square stirrups 4;
[0067] Step S4. After multiple FRP square stirrups 4 are tied to the first FRP rectangular tube 3, an FRP reinforcement cage is formed; the FRP reinforcement cage is placed into the casting mold and fixed in place;
[0068] Step S5. Pour concrete into the FRP reinforcement cage in the casting mold and tamp and vibrate it until it is compacted to obtain the casting specimen;
[0069] Step S6. Set the curing period. After the cast specimen has reached the curing period, remove the casting mold to obtain a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes.
[0070] Specifically, in step S2, the binding directions of multiple FRP square stirrups 4 should be alternated sequentially, and loops can be set at 100mm intervals to enhance overall stability.
[0071] Specifically, the concrete poured in step S5 can be commercial concrete, etc.; and during pouring, the gaps between adjacent FRP square stirrups 4, the first through hole 8, and the hole positions of the second through hole should be used for tamping. The concrete poured into the FRP cage should be properly vibrated until it is dense and has no obvious honeycomb surface.
[0072] Example 2
[0073] like Figures 7-9 As shown, this embodiment of a high-ductility fully FRP-reinforced concrete beam containing FRP rectangular tubes includes FRP square stirrups 4 and a first FRP rectangular tube 3; the interior of the FRP square stirrups 4 forms a rectangular receiving surface; the width of the receiving surface is the same as the width of the cross-section of the first FRP rectangular tube 3, and the length of the receiving surface is greater than the length of the cross-section of the first FRP rectangular tube 3; multiple FRP square stirrups 4 are equally spaced on the outside of the tube body of the first FRP rectangular tube 3, and the receiving surface of each FRP square stirrup 4 is perpendicular to the tube axis of the first FRP rectangular tube 3; each FRP square stirrup 4 is fixedly connected to the outer top wall, left side wall, and right side wall of the first FRP rectangular tube 3.
[0074] Preferably, a first FRP tension longitudinal bar 5 is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup 4; the first FRP tension longitudinal bar 5 is provided along the tube axis of the first FRP rectangular tube 3 and is perpendicular to the receiving surface of each FRP square stirrup 4.
[0075] Preferably, the first FRP tensile longitudinal reinforcement 5 and each FRP square stirrup 4 are fixedly connected and located below the outer bottom wall of the first FRP rectangular tube 3; a constraint zone 7 is provided between the first FRP tensile longitudinal reinforcement 5 and the outer bottom wall of the first FRP rectangular tube 3; the constraint zone 7 is filled with concrete.
[0076] Preferably, the first FRP rectangular tube 3 has openings at both ends; the high-ductility all-FRP reinforced concrete beam also includes FRP reinforcing bars 2; the FRP reinforcing bars 2 are fixedly installed on the inner top wall of the first FRP rectangular tube 3, and a first compression zone 6 is formed between the FRP reinforcing bars 2 and the inner bottom wall of the first FRP rectangular tube 3; the first compression zone 6 is filled with concrete.
[0077] Preferably, the left or right side wall of the first FRP rectangular tube 3 is provided with a plurality of through third holes 9 at equal intervals along its tube axis, and there is a third hole 9 between every two adjacent FRP square stirrups 4.
[0078] Preferably, the high-ductility fully FRP reinforced concrete beam further includes a protective layer 1; the protective layer 1 encloses the FRP square stirrups 4 and the first FRP rectangular tube 3.
[0079] In this embodiment, a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes has a third through hole 9 with a diameter of 50mm opened on the left side wall of the first FRP rectangular tube 3 to facilitate concrete pouring and vibration, and the center distance between every two adjacent third through holes 9 is 100mm.
[0080] like Figure 9 As shown in the figure, in this embodiment, after a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes is placed laterally into the formwork, the ends of the first FRP rectangular tube 3 are temporarily sealed with sealing cloth. The concrete is poured in stages, and rubber concrete, which has lower stiffness and better ductility than ordinary concrete, can be poured locally inside the first FRP rectangular tube 3. In this embodiment, the coarse aggregate of the rubber concrete is selected as crushed stone with a particle size of 5-10mm, continuously graded, and rubber particles with a particle size of 1.5-3mm are added to the concrete in different proportions to make rubber concrete, so as to enhance the deformation capacity of the concrete in the compression zone of the beam section in the later stage of bearing, and further achieve the design goal of high ductility.
[0081] After the rubber concrete is poured, other types of concrete can be poured in the remaining part to complete subsequent operations such as vibration, smoothing, polishing and curing.
[0082] Example 3
[0083] like Figures 10-11 As shown, this embodiment of a high-ductility fully FRP-reinforced concrete beam containing FRP rectangular tubes includes FRP square stirrups 4 and a first FRP rectangular tube 3; the interior of the FRP square stirrups 4 forms a rectangular receiving surface; the width of the receiving surface is the same as the width of the cross-section of the first FRP rectangular tube 3, and the length of the receiving surface is greater than the length of the cross-section of the first FRP rectangular tube 3; multiple FRP square stirrups 4 are equally spaced on the outside of the tube body of the first FRP rectangular tube 3, and the receiving surface of each FRP square stirrup 4 is perpendicular to the tube axis of the first FRP rectangular tube 3; each FRP square stirrup 4 is fixedly connected to the outer top wall, left side wall, and right side wall of the first FRP rectangular tube 3.
[0084] Preferably, the first FRP rectangular tube 3 has openings at both ends; the high-ductility all-FRP reinforced concrete beam also includes FRP reinforcing bars 2; the FRP reinforcing bars 2 are fixedly installed on the inner top wall of the first FRP rectangular tube 3, and a first compression zone 6 is formed between the FRP reinforcing bars 2 and the inner bottom wall of the first FRP rectangular tube 3; the first compression zone 6 is filled with concrete.
[0085] Preferably, the left or right side wall of the first FRP rectangular tube 3 is provided with a plurality of through third holes 9 at equal intervals along its tube axis, and there is a third hole 9 between every two adjacent FRP square stirrups 4.
[0086] Preferably, the length of the receiving surface is equal to twice the length of the cross-section of the first FRP rectangular tube 3; a second FRP rectangular tube 10 is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup 4; each FRP square stirrup 4 is fixedly connected to the outer bottom wall, left side wall and right side wall of the second FRP rectangular tube 10; the outer top wall of the second FRP rectangular tube 10 is in contact with the outer bottom wall of the first FRP rectangular tube 3.
[0087] Preferably, the high-ductility fully FRP reinforced concrete beam further includes a second FRP tensile longitudinal bar; the second FRP rectangular tube 10 has openings at both ends; the second FRP tensile longitudinal bar is fixedly disposed on the inner bottom wall of the second FRP rectangular tube 10, and a second compression zone 11 is formed between the second FRP tensile longitudinal bar and the inner bottom wall of the second FRP rectangular tube 10; the second compression zone 11 is filled with concrete.
[0088] Preferably, the left or right side wall of the second FRP rectangular tube 10 is provided with a plurality of through fourth holes 12 at equal intervals along its tube axis, and there is a fourth hole 12 between every two adjacent FRP square stirrups.
[0089] Specifically, in this embodiment, both the first FRP rectangular tube 3 and the second FRP rectangular tube 10 have openings on one side of the sidewall, which is different from the first and second embodiments where openings are made on both the upper and lower walls.
[0090] Preferably, the high-ductility fully FRP reinforced concrete beam further includes a protective layer 1; the protective layer 1 encloses the FRP square stirrups 4, the first FRP rectangular tube 3, and the second FRP rectangular tube 10.
[0091] like Figures 10-11 As shown in the figure, this embodiment describes a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes. The beam cross-section is 250*450mm, the total length of the beam is 3000mm, and the width of the protective layer 1 is 25mm.
[0092] Under wind loads and horizontal seismic action, the bending moments borne by frame beams are prone to change sign, sometimes positive and sometimes negative. Furthermore, for prefabricated beam components, to simplify design and facilitate construction, symmetrical reinforcement of the beam cross-section is adopted to avoid the phenomenon of staggered longitudinal reinforcement.
[0093] The specific reinforcement information of the beam is as follows: In this embodiment, a high-ductility all-FRP reinforced concrete beam containing FRP rectangular tubes is provided with a second FRP tension longitudinal bar with a diameter of 13mm in the second compression zone 11. Specifically, it is a glass fiber bar used as a stirrup bar with an elastic modulus of about 50GPa and a fracture strain of about 1.80%. The second FRP tension longitudinal bar is also made of epoxy resin or vinyl ester resin, and its surface is sandblasted after the resin of the second FRP tension longitudinal bar has cured.
[0094] That is, the first compression zone 6 at the top and the second compression zone 11 at the bottom of the high-ductility fully FRP reinforced concrete beam adopt a symmetrical reinforcement method.
[0095] Specifically, such as Figure 10 As shown, in this embodiment, the first FRP rectangular tube 3 has a third through hole 9 on its left side wall, and the second FRP rectangular tube 10 also has a fourth through hole 12 on its left side wall. The hole spacing on one side of the two FRP rectangular tubes should match the spacing of the FRP square stirrups 4. In this embodiment, both the third through hole 9 and the fourth through hole 12 are circular holes with a diameter of 50mm, and the center distance between adjacent circular holes is 100mm.
[0096] Specifically, this embodiment describes a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes. The concrete can be ordinary concrete, high-strength concrete, rubber concrete, or seawater sand concrete; for ordinary concrete, a grade of C30-C55 is recommended. To facilitate pouring and ensure the compactness of the confined zone concrete, concrete with aggregate diameters in the range of 5-10mm is selected. The concrete is mixed according to the mix proportion, and the slump of the mixed concrete is controlled at 180-200mm. After pouring and vibration, and curing under standard conditions to reach the design specified age, the high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes provided by this invention can be obtained.
[0097] Specifically, in this embodiment, the design of a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes should comply with fiber composite material specifications, with a cross-sectional reinforcement ratio ρ greater than 1.4 times the equilibrium reinforcement ratio ρ. b This results in the cross-sectional failure mode exhibiting as compressive failure of concrete; the constraint of the two FRP rectangular tubes in the compression zone further enhances the compressive strength and deformation capacity of the concrete. Simultaneously, the two FRP rectangular tubes can, to some extent, prevent the reduction in bearing capacity caused by the buckling of the FRP reinforcement in the compression zone.
[0098] Specifically, in this embodiment, a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes improves the load-bearing capacity and ductility of the entire beam under bending moment by confining the concrete in the compression zone through two perforated FRP rectangular tubes. Simultaneously, the two FRP rectangular tubes can, to some extent, prevent buckling of components located in the compression zone. The perforations in the two FRP rectangular tubes facilitate concrete pouring and vibration during actual construction, and the diameter of the perforations in the two FRP rectangular tubes is larger than that of a conventional vibrator.
[0099] Preferably, the FRP material in this embodiment can be GFRP, CFRP, BFRP or AFRP.
[0100] Preferably, the thickness of the two FRP rectangular tubes in this embodiment can be selected as 6-10mm.
[0101] Preferably, the reinforcement in this embodiment should be configured as over-reinforced, and the failure state of the cross section should be concrete compressive failure.
[0102] The embodiments of a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes and its construction method provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
Claims
1. A high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes, characterized in that, The system includes FRP square stirrups (4) and a first FRP rectangular tube (3). The interior of the FRP square stirrups (4) forms a rectangular receiving surface. The width of the receiving surface is the same as the width of the cross-section of the first FRP rectangular tube (3), and the length of the receiving surface is greater than the length of the cross-section of the first FRP rectangular tube (3). Multiple FRP square stirrups (4) are equally spaced on the outside of the tube body of the first FRP rectangular tube (3), and the receiving surface of each FRP square stirrup (4) is perpendicular to the tube axis of the first FRP rectangular tube (3). Each FRP square stirrup (4) is fixedly connected to the outer top wall, left side wall, and right side wall of the first FRP rectangular tube (3). The top wall of the first FRP rectangular tube (3) is provided with a plurality of through holes (8) at equal intervals along its tube axis, and there is a first through hole (8) between every two adjacent FRP square stirrups (4); the bottom wall of the first FRP rectangular tube (3) is provided with a plurality of through holes (2) at equal intervals along its tube axis, and there is a second through hole between every two adjacent FRP square stirrups (4); the number of first through holes (8) and second through holes is the same and their positions correspond one-to-one; The distance along the width direction of the first FRP rectangular tube (3) is l1; the distance along the height direction of the first FRP rectangular tube (3) is l2, and l2 = 1.0l1~1.2l1; the outer chamfer radius of the first FRP rectangular tube (3) is the same as the inner chamfer radius of the FRP square stirrup (4); A first FRP tension longitudinal bar (5) is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup (4); the first FRP tension longitudinal bar (5) is provided along the tube axis of the first FRP rectangular tube (3) and is perpendicular to the receiving surface of each FRP square stirrup (4); the first FRP tension longitudinal bar (5) and each FRP square stirrup (4) are fixedly connected and located below the outer bottom wall of the first FRP rectangular tube (3); a constraint area (7) is provided between the first FRP tension longitudinal bar (5) and the outer bottom wall of the first FRP rectangular tube (3); the constraint area (7) is filled with concrete; The first FRP rectangular tube (3) has openings at both ends; the high-ductility all-FRP reinforced concrete beam also includes FRP reinforcing bars (2); the FRP reinforcing bars (2) are fixedly installed on the inner top wall of the first FRP rectangular tube (3), and a first compression zone (6) is formed between the FRP reinforcing bars (2) and the inner bottom wall of the first FRP rectangular tube (3); the first compression zone (6) is filled with concrete.
2. The high-ductility fully FRP reinforced concrete beam according to claim 1, characterized in that, The length of the receiving surface is equal to twice the length of the cross-section of the first FRP rectangular tube (3); a second FRP rectangular tube (10) is provided between the outer bottom wall of the FRP square stirrup and the FRP square stirrup (4); each of the FRP square stirrups (4) is fixedly connected to the outer bottom wall, left side wall and right side wall of the second FRP rectangular tube (10); the outer top wall of the second FRP rectangular tube (10) is in contact with the outer bottom wall of the first FRP rectangular tube (3).
3. The high-ductility fully FRP reinforced concrete beam according to claim 2, characterized in that, The high-ductility fully FRP reinforced concrete beam also includes a second FRP tension longitudinal bar; the two ends of the second FRP rectangular tube (10) are open; the second FRP tension longitudinal bar is fixedly installed on the inner bottom wall of the second FRP rectangular tube (10), and a second compression zone (11) is formed between the second FRP tension longitudinal bar and the inner bottom wall of the second FRP rectangular tube (10); the second compression zone (11) is filled with concrete.
4. The high-ductility fully FRP reinforced concrete beam according to claim 2, characterized in that, The first FRP rectangular tube (3) has multiple through third holes (9) at equal intervals along its tube axis on its left or right side wall, and there is one of the third holes (9) between every two adjacent FRP square stirrups (4); the second FRP rectangular tube (10) has multiple through fourth holes (12) at equal intervals along its tube axis on its left or right side wall, and there is one of the fourth holes (12) between every two adjacent FRP square stirrups.
5. The high-ductility fully FRP reinforced concrete beam according to claim 1, characterized in that, The high-ductility fully FRP reinforced concrete beam also includes a protective layer (1); the protective layer (1) wraps the FRP square stirrups (4) and the first FRP rectangular tube (3).
6. A construction method for a high-ductility, fully FRP-reinforced concrete beam containing FRP rectangular tubes, characterized in that, Including the high-ductility fully FRP reinforced concrete beam as described in any one of claims 1 to 5; the construction method further includes the following steps: Step S1. Set the first spacing value, and space the multiple FRP support bars (2) according to the first spacing value and fix them to the inner top wall of the first FRP rectangular tube (3); Step S2. Set the second spacing value, and according to the second spacing value, space out multiple FRP square stirrups (4) and tie them to the outside of the first FRP rectangular tube (3), and each FRP square stirrup (4) is fixedly connected to the outer top wall, left side wall and right side wall of the first FRP rectangular tube (3); Step S3. Set the third spacing value, and space multiple first FRP tension longitudinal bars (5) according to the third spacing value and set them between the outer bottom wall of the first FRP rectangular tube (3) and the FRP square stirrup (4), and fix them to the FRP square stirrup (4). Step S4. After multiple FRP square stirrups (4) are tied to the first FRP rectangular tube (3), an FRP reinforcement cage is formed; the FRP reinforcement cage is placed into the casting mold and fixed in place; Step S5. Pour concrete into the FRP reinforcement cage in the casting mold and tamp and vibrate it until it is compacted to obtain the casting specimen; Step S6. Set the curing period. After the cast specimen has reached the curing period, remove the casting mold to obtain a high-ductility fully FRP reinforced concrete beam containing FRP rectangular tubes.