Closed FRP stirrup seawater and sea sand concrete beam and construction method thereof

Abstract

According to the closed FRP stirrup seawater and sea sand concrete beam and the construction method thereof, the core concrete area constraint stability and shaping are high, and the flexural capacity and ductility of the concrete beam are improved. The beam comprises a beam body, a stress rib framework arranged in the beam body and a plurality of stirrup pieces arranged on the upper portion of the stress rib framework in the circumferential axial direction of the beam body. The multiple stirrup pieces form a constraint area in the middle of the stress rib framework, and the span of the constraint area accounts for 1 / 3-1 / 2 of the effective span of the beam body. The integrally-formed closed FRP stirrup structure is adopted, the phenomena of fiber stress concentration and fiber twisting of a bent section are greatly improved by reducing the radius difference between fibers of the inner layer and fibers of the outer layer, and meanwhile lap joint damage can be avoided through the closed shape. The method is applied to the technical field of civil engineering.

Description

Technical Field

[0001] This invention relates to the technical field of civil engineering, and in particular to a closed FRP-reinforced seawater sand concrete beam and its construction method. Background Technology

[0002] With river sand mining severely restricted, finding alternative sand sources has become an urgent need for the industry. On the one hand, sea sand, due to its abundant reserves, wide distribution, and convenient extraction, is considered a potential resource for alleviating the supply and demand imbalance of building materials and promoting sustainable development. On the other hand, global freshwater resources are becoming increasingly scarce, while concrete production consumes a large amount of freshwater, further exacerbating the water crisis. Using seawater instead of freshwater to mix concrete has become an effective means of conserving freshwater resources. However, the high chloride ion content in sea sand significantly accelerates the corrosion process of reinforcing steel, severely restricting its widespread application in ordinary reinforced concrete structures.

[0003] Currently, the control of chloride ions in sea sand mainly relies on freshwater rinsing. This process is not only costly and increases freshwater consumption, but also prone to residual chloride ions when incompletely treated, leading to steel reinforcement corrosion, reduced structural durability, and shortened service life. Fiber-reinforced polymer (FRP) bars, as a non-metallic reinforcing material, exhibit excellent chemical stability in chloride-rich environments. They are lightweight, high-strength, and durable, fundamentally avoiding corrosion problems and making them an ideal alternative to steel reinforcement.

[0004] The traditional rectangular FRP stirrups or FRP spiral stirrups currently used are used to implement regional confinement of the concrete in the compression zone of the beam, thereby improving the beam's bearing capacity, deformation capacity, and compressibility of the compressed concrete. However, the existing confinement methods still have significant shortcomings: (1) Traditional rectangular FRP stirrups are formed by lap splicing, and there are structural defects in the lap splice area. Due to manufacturing process limitations, fiber stress concentration and kinking are prone to occur at the corners of the stirrups, resulting in low confinement efficiency of the core concrete; (2) Circular FRP spiral stirrups are difficult to provide effective confinement of the corner concrete of rectangular cross-section beams, and therefore are not suitable for rectangular cross-sections. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a closed FRP stirrup seawater sand concrete beam with high core concrete area constraint stability and shape, which improves the flexural bearing capacity and ductility of the concrete beam and its construction method.

[0006] The technical solution adopted in this invention is as follows: This invention includes a beam, a reinforcing skeleton disposed in the beam, and a plurality of stirrups disposed along the circumferential axis of the beam on the upper part of the reinforcing skeleton; the plurality of stirrups form a constraint region in the middle of the reinforcing skeleton, and the span of the constraint region accounts for 1 / 3 to 1 / 2 of the effective span of the beam.

[0007] Furthermore, the stirrup is a continuous fiber winding integral molding structure.

[0008] Furthermore, the thickness-to-width ratio of the stirrup is taken as 1 / 3 to 1 / 2.

[0009] Furthermore, the stirrup member has a hollow rectangular structure.

[0010] Furthermore, the stirrup member has a hollow double rectangular structure.

[0011] Furthermore, the reinforcing skeleton includes two compression bars, two tension bars, and several shear bars. The two compression bars and the two tension bars are arranged along the axial direction of the beam. The two compression bars are symmetrically arranged on the upper part of the beam, and the two tension bars are symmetrically arranged on the lower part of the beam. Each shear bar is perpendicular to the compression bars and the tension bars, and each shear bar is fixedly connected to the compression bars and the tension bars at equal intervals along the axial direction of the beam.

[0012] Furthermore, the compression rib, the tension rib, and the shear rib are all made of FRP (fiberglass reinforced plastic).

[0013] Furthermore, a construction method for closed-cell FRP-reinforced seawater sand concrete beams includes the following steps:

[0014] S1. Cut the continuously fiber-wound FRP pipe to obtain multiple stirrup sections;

[0015] S2. Assemble the casting mold and apply release agent evenly to the inner surface of the mold;

[0016] S3. Tie the reinforcing bar cage according to the drawings. Fix the stirrups to the upper part of the reinforcing bar cage and set the pads on the bottom and sides of the reinforcing bar cage to ensure the required concrete cover thickness.

[0017] S4. Put the dry materials into the mixer and mix them evenly. Then add the seawater containing the admixture and mix wet until a fresh concrete with uniform color and consistency is obtained.

[0018] S5. Pour the concrete into the prepared molds in batches and vibrate the concrete to remove air bubbles.

[0019] S6. Immediately after pouring, cover with geotextile or plastic film for water retention and curing. After final setting, remove the side formwork within 12-24 hours depending on the temperature. After removing the formwork, immediately use spraying, water storage or wrapping with curing film for continuous moist curing for no less than 14 days.

[0020] Furthermore, in step S1, a high-speed cold cut is performed using a precision saw with a diamond grinding wheel or a waterjet cutter to ensure that the cut is flat and burr-free, and that the cutting plane is perpendicular to the axis of the FRP pipe.

[0021] Furthermore, in step S4, the dry material is prepared using coarse aggregate, sea sand and cement, and the admixture is a water-reducing agent.

[0022] The beneficial effects of this invention are as follows: This invention uses stirrups to form a confinement area in the middle of the upper side of the reinforcing bar skeleton. The confinement area further improves the bending load-bearing capacity and ductility of the beam, and the upper side of the beam has stronger resistance to deformation. The stirrups adopt an integrally formed closed FRP stirrup structure. By reducing the radius difference between the inner and outer fibers, the fiber stress concentration and fiber kinking phenomenon in the bending section are greatly improved. At the same time, the closed shape can avoid the occurrence of lap joint failure. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the first structure of the closed FRP stirrup seawater sand concrete beam of the present invention;

[0024] Figure 2 This is a schematic diagram of the second structure of the closed FRP stirrup seawater sand concrete beam of the present invention;

[0025] Figure 3 This is a structural schematic diagram of Embodiment 1 of the closed FRP stirrup seawater sand concrete beam of the present invention;

[0026] Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the closed FRP stirrup seawater sand concrete beam of the present invention;

[0027] Figure 5 This is a schematic diagram of the bent portion of a traditional rectangular FRP stirrup in the background art;

[0028] Figure 6 This is a schematic diagram of the bent portion of the stirrup member in the closed FRP stirrup seawater sand concrete beam of the present invention.

[0029] In the diagram: 1. Beam; 2. Stirrups; 3. Confined area; 4. Compression reinforcement; 5. Tension reinforcement; 6. Shear reinforcement. Detailed Implementation

[0030] Example 1

[0031] like Figures 1 to 3As shown, in this embodiment, the present invention includes a beam 1, a reinforcing skeleton disposed within the beam 1, and a plurality of stirrups 2 disposed along the circumferential axis of the beam 1 on the upper part of the reinforcing skeleton; the plurality of stirrups 2 form a constraint region 3 in the middle of the reinforcing skeleton, and the span of the constraint region 3 accounts for 1 / 3 to 1 / 2 of the effective span of the beam 1.

[0032] Specifically, beam 1 is a seawater sand concrete beam structure. The reinforcing skeleton is formed by binding two compression bars 4, two tension bars 5 and several shear bars 6. Each stirrup 2 is set between two adjacent shear bars 6 to improve the bending bearing capacity and ductility of beam 1 after it is formed. At the same time, the stirrup 2 forms a confinement area 3 by surrounding the core concrete of the upper part of beam 1, which restricts its lateral expansion deformation, thereby improving the bending bearing capacity and ductile deformation capacity of beam 1. Especially under seismic or high load conditions, it can effectively prevent brittle failure.

[0033] Under the same casting conditions, reinforcement skeleton structure, and strength, the flexural bearing capacity of the beam using the new type of closed FRP stirrups 2 to confine the compression zone is increased by 14.83%, 8.69%, and 3.44% compared to beams with unconfined stirrups, traditional FRP rectangular stirrups, and circular FRP spiral stirrups, respectively.

[0034] Under the same conditions of beam 1 casting, reinforcing bar skeleton structure and strength, the energy ductility coefficient of the beam using the new closed FRP stirrup 2 to confine the compression area is increased by 65.63%, 13.11% and 8.80% compared with the beam with unconfined stirrups, traditional FRP rectangular stirrups and circular FRP spiral stirrups.

[0035] In this embodiment, the stirrup 2 is a continuous fiber winding integral molding structure.

[0036] Specifically, the stirrup 2 formed by continuous fiber winding can be classified, bundled, transported and stored, making management convenient. Compared with circular FRP spiral stirrups, the stirrup 2 formed by continuous fiber winding can be pre-processed in large quantities and transported to the work surface. During construction, it is only necessary to insert it into the longitudinal reinforcement and fix it with tie wire at the corners and necessary positions. The operation is simple and intuitive, and workers do not need special training.

[0037] In this embodiment, the thickness-to-width ratio of the stirrup member 2 is 1 / 3 to 1 / 2.

[0038] Specifically, the constraint area 3 formed by the stirrup 2 provides effective constraint on the upper part of the beam 1, and the thickness-to-width ratio is preferably 0.4, so that the stirrup 2 has sufficient constraint effect, the beam 1 has better plastic deformation capacity, and the seismic performance and safety of the structure are improved.

[0039] In this embodiment, the stirrup 2 has a hollow rectangular structure.

[0040] Specifically, the stirrup component 2 has a rectangular hollow structure, which is suitable for most of the reinforcing bar skeletons on the market. It can be classified, bundled, transported and stored, making management convenient. It is also highly adaptable to non-standard components or beams with varying dimensions.

[0041] In this embodiment, the reinforcing skeleton includes two compression bars 4, two tension bars 5, and several shear bars 6. The two compression bars 4 and the two tension bars 5 are arranged along the axial direction of the beam 1. The two compression bars 4 are symmetrically arranged on the upper part of the beam 1, and the two tension bars 5 are symmetrically arranged on the lower part of the beam 1. Each shear bar 6 is perpendicular to the compression bars 4 and the tension bars 5, and each shear bar 6 is fixedly connected to the compression bars 4 and the tension bars 5 at equal intervals along the axial direction of the beam 1.

[0042] Specifically, the compression reinforcement 4, tension reinforcement 5, and shear reinforcement 6 are tied together with cable ties to form a skeleton structure for the pouring of beam 1. A stirrup 2 is tied between two adjacent shear reinforcements 6 to form a stable FRP reinforcement skeleton with the compression reinforcement 4 and tension reinforcement 5, ensuring that the compression reinforcement 4 and tension reinforcement 5 maintain the correct position during concrete pouring and stress, and preventing displacement or instability.

[0043] In this embodiment, the compression rib 4, the tension rib 5, and the shear rib 6 are all made of FRP (fiberglass reinforced plastic) bars.

[0044] Specifically, regarding FRP (fiberglass reinforced plastic) skeletons.

[0045] In this embodiment, the construction method of a closed FRP stirrup seawater sand concrete beam includes the following steps:

[0046] S1. Cut the continuously fiber-wound FRP pipe to obtain multiple stirrup pieces 2;

[0047] S2. Assemble the casting mold and apply release agent evenly to the inner surface of the mold;

[0048] S3. Tie the reinforcing bar skeleton according to the drawings. Fix the stirrup 2 to the upper part of the reinforcing bar skeleton and set the pads on the bottom and sides of the reinforcing bar skeleton to ensure the required concrete cover thickness.

[0049] S4. Put the dry materials into the mixer and mix them evenly. Then add the seawater containing the admixture and mix wet until a fresh concrete with uniform color and consistency is obtained.

[0050] S5. Pour the concrete into the prepared molds in batches and vibrate the concrete to remove air bubbles.

[0051] S6. Immediately after pouring, cover with geotextile or plastic film for water retention and curing. After final setting, remove the side formwork within 12-24 hours depending on the temperature. After removing the formwork, immediately use spraying, water storage or wrapping with curing film for continuous moist curing for no less than 14 days.

[0052] Specifically, in step S2, the binding technique for the reinforcing bar skeleton should be gentle to avoid damaging the FRP bars.

[0053] In step S4, an immersion vibrator is used to fully vibrate the specimen to remove air bubbles and ensure compaction. During this process, it is strictly necessary to avoid the vibrator touching the FRP reinforcement skeleton. Finally, the surface of the specimen is smoothed.

[0054] After completing step S6 and the maintenance period is over, a qualified testing unit is commissioned to conduct physical inspections such as core sampling.

[0055] In this embodiment, in step S1, a precision saw or waterjet cutter with a diamond grinding wheel is used for high-speed cold cutting to ensure that the cut is flat and burr-free, and the cutting plane is perpendicular to the axis of the FRP pipe.

[0056] Specifically, the stirrup 2 cut along the axis perpendicular to the FRP pipe has a stable stress surface. The thickness-to-width ratio of the stirrup 2 is between 1 / 3 and 1 / 2 to ensure that the stirrup 2 can surround the core concrete of the upper part of the beam 1 and limit its lateral expansion deformation, thereby improving the bending bearing capacity and ductile deformation capacity of the beam 1, and effectively preventing brittle failure, especially under seismic or high load conditions.

[0057] In this embodiment, in step S4, the dry material is prepared using coarse aggregate, sea sand and cement, and the admixture is a water-reducing agent.

[0058] Specifically, the dry materials are added to the mixer in the following order: coarse aggregate, sea sand, and cement, with a ratio of 1:2:3.

[0059] Example 2

[0060] Figure 4 The illustration shows a second embodiment of the present invention, which is similar to... Figures 1 to 3 The difference in the first embodiment shown is that:

[0061] The stirrup 2 has a hollow double rectangular structure.

[0062] Specifically, the hollow double rectangular stirrup 2 forms a supporting rod-like structure in the middle region, which further improves the constraint effect of the constraint region 3 on the beam 1 and improves the bending bearing capacity and ductility of the beam 1.

[0063] Although the embodiments of the present invention are described with reference to actual solutions, they do not constitute a limitation on the meaning of the present invention. Modifications to the embodiments and combinations with other solutions based on this specification will be obvious to those skilled in the art.

Claims

1. A closed-type FRP-stirred seawater sand concrete beam, characterized in that: It includes a beam body (1), a reinforcing skeleton disposed within the beam body (1), and several stirrups (2) disposed along the circumferential axis of the beam body (1) on the upper part of the reinforcing skeleton; Several of the stirrups (2) form a constraint area (3) in the middle of the reinforcing skeleton, and the span of the constraint area (3) is 1 / 3 to 1 / 2 of the effective span of the beam (1).

2. The closed-type FRP-stirred seawater sand concrete beam according to claim 1, characterized in that: The stirrup (2) is a continuous fiber winding integral molding structure.

3. A closed-type FRP-reinforced seawater sand concrete beam according to claim 1, characterized in that: The thickness-to-width ratio of the stirrup (2) is 1 / 3 to 1 / 2.

4. A closed-type FRP-stirred seawater sand concrete beam according to claim 1, characterized in that: The stirrup (2) has a hollow rectangular structure.

5. A closed-type FRP-stirred seawater sand concrete beam according to claim 1, characterized in that: The stirrup (2) has a hollow double rectangular structure.

6. A closed-type FRP-stirred seawater sand concrete beam according to claim 1, characterized in that: The reinforcing skeleton includes two compression bars (4), two tension bars (5), and several shear bars (6). The two compression bars (4) and the two tension bars (5) are arranged along the axial direction of the beam (1). The two compression bars (4) are symmetrically arranged on the upper part of the beam (1), and the two tension bars (5) are symmetrically arranged on the lower part of the beam (1). Each shear bar (6) is perpendicular to the compression bars (4) and the tension bars (5). Each shear bar (6) is fixedly connected to the compression bars (4) and the tension bars (5) at equal intervals along the axial direction of the beam (1).

7. A closed-type FRP-reinforced seawater sand concrete beam according to claim 6, characterized in that: The compression reinforcement (4), the tension reinforcement (5), and the shear reinforcement (6) are all made of FRP (fiberglass reinforced plastic).

8. The construction method of the closed FRP stirrup seawater sand concrete beam as described in any one of claims 1-7, characterized in that, The method includes the following steps: S1. Cut the FRP pipe formed by continuous fiber winding to obtain multiple stirrups (2). S2. Assemble the casting mold and apply release agent evenly to the inner surface of the mold; S3. Tie the reinforcing bar skeleton according to the drawings. Fix the stirrups (2) to the upper part of the reinforcing bar skeleton and set the pads on the bottom and sides of the reinforcing bar skeleton to ensure the concrete protective layer thickness required by the design. S4. Add the dry materials into the mixer in the predetermined order and mix them evenly. Then add the seawater containing the admixture and mix wet until a fresh concrete with uniform color and consistency is obtained. S5. Pour the concrete into the prepared molds in batches and vibrate the concrete to remove air bubbles. S6. Immediately after pouring, cover with geotextile or plastic film for water retention and curing. After final setting, remove the side formwork within 12-24 hours depending on the temperature. After removing the formwork, immediately use spraying, water storage or wrapping with curing film for continuous moist curing for no less than 14 days.

9. The construction method according to claim 8, characterized in that: In step S1, a high-speed cold cut is performed using a precision saw with a diamond grinding wheel or a waterjet cutter to ensure that the cut is flat and burr-free, and that the cutting plane is perpendicular to the axis of the FRP pipe.

10. The construction method according to claim 8, characterized in that: In step S4, the dry material is prepared using coarse aggregate, sea sand and cement, and the admixture is a water-reducing agent.

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