Closed FRP (Fiber Reinforce Plastic) stirrup connected by inflection point sleeve

Abstract

The utility model discloses a closed FRP stirrup connected by inflection point sleeves, which comprises FRP ribs, inflection point sleeves and epoxy resin, the adjacent FRP ribs are connected through the inflection point sleeves to form the closed FRP stirrup, and each inflection point sleeve is filled with the epoxy resin; the inflection point sleeve comprises a sleeve body, a grouting opening and a grout outlet, wherein the grouting opening and the grout outlet are formed in the sleeve body, and the two ends of the sleeve body are in threaded connection with conical sleeve heads. According to the FRP stirrup, the problem that the strength of the FRP stirrup at the inflection point is insufficient is effectively solved, the performance and durability of the stirrup are remarkably improved through the unique connecting mode and grouting material selection, and the FRP stirrup is suitable for being applied to structural engineering under various severe environment conditions.

Description

Technical Field

[0001] The utility model relates to a closed FRP stirrup connected by an inflection point sleeve, belonging to the technical field of structural engineering. Background Art

[0002] Under corrosive or harsh environmental conditions, traditional reinforced concrete structures often face the problem of steel bar corrosion, which greatly weakens the overall performance of the structure and thus incurs high repair costs. To address this challenge, fiber-reinforced polymer (FRP) bars have gradually been regarded as an effective solution. Compared with steel bars, FRP bars exhibit a series of remarkable advantages. For example, they have excellent tensile strength, extremely strong resistance to corrosive environments, light weight which makes transportation and handling more convenient, and also possess thermal insulation and electrical insulation properties. These advantages have made FRP bars increasingly widely used in the field of structural engineering.

[0003] Since stirrups are located on the periphery of structural members, they are more vulnerable to severe environmental impacts, accelerating the structural deterioration process and reducing the service life of the structure. Therefore, using FRP materials as substitutes for shear reinforcement in prestressed and reinforced concrete structures is gradually becoming a countermeasure to address the erosion of structural members by harsh environments. In addition, closed stirrups are relatively common in FRP stirrups. A closed stirrup refers to a closed annular bar locked inside the concrete to enhance the bearing capacity of the concrete. Compared with ordinary stirrups, closed stirrups have significant differences in aspects such as shape structure, placement state, function, and enhanced seismic performance.

[0004] FRP bars are made of anisotropic materials, and their transverse strength is weaker compared to the longitudinal strength. Bending FRP bars to form stirrups significantly reduces the strength at the inflection points because at the inflection points, the stirrups not only bear the longitudinal stress parallel to the fiber direction but also the lateral load from the concrete. In addition, the bending of FRP bars causes kinking of the innermost fibers and the outermost fibers at the inflection points. Compared with straight bars, the inherent weakness of the fibers perpendicular to the axis and the kinking of the fibers at the bends result in a reduction in the strength of the bent part of FRP stirrups. In particular, FRP stirrups with circular cross-sections can only withstand approximately 30% - 80% of the axial tensile strength. It can be seen that the material utilization efficiency of FRP stirrups largely depends on the strength at their inflection points. When FRP bars are used as shear reinforcement in concrete beams, their designed shear strength is also determined by their bending ability. The bending performance of FRP bars is affected by the bending process, the ratio of the bending radius to the bar diameter, and the type of fiber. Summary of the Invention

[0005] In view of the problem that in the prior art, when FRP stirrups are applied in the field of structural engineering, especially under harsh environmental conditions, the strength at their inflection points is reduced due to the bending process and fiber characteristics,

[0006] The purpose of the present utility model is to provide a closed FRP stirrup connected by an inflection point sleeve, so as to solve the problem of insufficient strength at the inflection point during the formation of the FRP stirrup, and at the same time maintain excellent properties such as high strength and corrosion resistance of the FRP stirrup, so as to improve the mechanical properties, durability and service life of the structural engineering.

[0007] In order to achieve the above purpose, the technical solution of the present utility model is: a closed FRP stirrup connected by an inflection point sleeve, including FRP bars, inflection point sleeves and epoxy resin. Adjacent FRP bars are connected by inflection point sleeves to form a closed FRP stirrup, and epoxy resin is filled in each inflection point sleeve.

[0008] Further, the inflection point sleeve includes a sleeve body, a grouting port and a slurry outlet provided on the sleeve body, and tapered socket heads are threadedly connected to both ends of the sleeve body.

[0009] Further, internal threads are provided in the sleeve body.

[0010] Further, the tapered socket head is composed of a tapered cylinder and an interface thread section, and a rubber sealing ring is installed in the tapered cylinder.

[0011] Further, the anchorage length of the FRP bar in the inflection point sleeve is not less than 10 times the diameter of the FRP bar.

[0012] Due to the adoption of the above technical solution, the advantages of the present utility model are: the present utility model not only effectively solves the problem of insufficient strength at the inflection point of the FRP stirrup, but also significantly improves the performance and durability of the stirrup through a unique connection method and grouting material selection, and is applicable to structural engineering applications under various harsh environmental conditions. Description of the Drawings

[0013] By describing the exemplary embodiments of the present utility model in more detail with reference to the drawings, the above and other aspects and advantages of the present utility model will become more clearly understood. In the drawings:

[0014] Figure 1 is a structural schematic diagram of the present utility model;

[0015] Figure 2 is a detailed connection drawing at the inflection point of the stirrup;

[0016] Figure 3 is a front view of the tapered socket head;

[0017] Figure 4 is a top view of the tapered socket head;

[0018] Description of reference numerals: 1 - FRP straight rib; 2 - inflection point sleeve; 21 - sleeve body; 211 - barrel wall; 212 - internal thread; 22 - grouting port; 23 - slurry outlet; 24 - conical socket head; 241 - conical barrel; 242 - interface thread section; 243 - rubber sealing ring; 3 - epoxy resin. Detailed implementation mode

[0019] In order to make the purpose, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below with reference to the drawings and embodiments, wherein the materials can all be obtained through commercial channels.

[0020] Embodiment 1

[0021] The structural schematic diagram of a closed FRP stirrup connected by an inflection point sleeve of the present utility model is as Figures 1 to 4 shown, including FRP rib 1, inflection point sleeve 2 and epoxy resin 3. Adjacent FRP ribs 1 are connected by inflection point sleeve 2 to form a closed FRP stirrup, and epoxy resin 3 is filled in each inflection point sleeve 2. In this embodiment, the variety of epoxy resin 3 is bisphenol A type epoxy, the epoxy equivalent is 210 - 244 g / eq, and the viscosity is 15000 - 25000 mPas. A polyamine is used as the curing agent and is used in a 1:1 molar ratio with the epoxy resin.

[0022] The production process of all FRP ribs 1 involves completely impregnating continuous fibers in a thermosetting resin, and then shaping through a pultrusion process. FRP rib 1 is a composite material formed by combining high-performance fibers and polymers, including carbon fiber reinforced polymer CFRP rib, basalt fiber reinforced polymer BFRP rib, glass fiber reinforced polymer GFRP rib, and aramid fiber reinforced polymer AFRP rib. The ultimate tensile strength of the FRP rib 1 used in this embodiment reaches 1000 MPa, the elastic modulus reaches 120 GPa, and an elongation rate of 0.019 can be exhibited under the ultimate state. In order to ensure good anchoring performance of the FRP rib 1 in the inflection point sleeve 2, an FRP rib 1 with ribbed surfaces is selected, and the height of the ribbed surface is at least 0.5 mm.

[0023] The inflection point sleeve 2 includes a sleeve body 21, a grouting port 22 and a slurry outlet 23 provided on the sleeve body 21. The grouting port 22 and the slurry outlet 23 are located on the straight section of the sleeve body 21. Tapered socket heads 24 are threadedly connected to both ends of the sleeve body 21. The preparation material of the inflection point sleeve 2 can be selected from steel or thermoplastic engineering plastics with excellent mechanical properties, dimensional stability, and high and low temperature resistance. In highly corrosive or harsh environments, thermoplastic engineering plastics should be used for preparation. The raw materials of thermoplastic engineering plastics can be high-performance plastics such as polycarbonate PC, polyamide nylon PA, and polyoxymethylene POM. The plastic processing method adopts injection molding. The minimum value of the difference between the minimum inner diameter of the sleeve body 21 and the nominal diameter of the FRP bar 1 should not be less than 10 mm.

[0024] To improve the bonding force of the FRP bar 1 in the sleeve body 21 and improve the connection effect, internal threads are provided in the sleeve body 21.

[0025] To improve the gripping ability of the FRP bar 1 and prevent the epoxy resin 3 from falling off due to low shear ability, tapered socket heads 24 are threadedly connected to both ends of the sleeve body 21. The tapered socket head 24 is composed of a tapered cylinder 241 and an interface thread section 242. A rubber sealing ring 243 is installed in the tapered cylinder 241. The material of the rubber sealing ring 243 can be selected from general synthetic rubber and natural rubber, which usually have excellent elasticity, mechanical strength, deformation ability, acid and alkali resistance, water isolation and other characteristics. In this embodiment, the natural rubber used has a density of about 0.913 g / cm 3 , a refractive index of 1.52, a glass transition temperature of -72 °C, a flow temperature of 130 - 140 °C, a tensile strength of up to 17 - 25 Mpa, an elastic modulus of 2 - 4 Mpa, an elongation at break of up to 1000%, and a resilience between 50% - 85%. The rubber sealing ring 243 and the tapered cylinder 241 are connected by hot melting.

[0026] To ensure that the FRP bar 1 and the epoxy resin 3 can stably transfer loads during the force application process, thereby meeting the structural bearing capacity requirements, the anchorage length of the FRP bar 1 in the inflection point sleeve 2 is not less than 10 times the diameter of the FRP bar 1.

[0027] The specific manufacturing process of the embodiment of the present utility model is as follows:

[0028] First, prepare the FRP bar 1 material according to the design requirements, and ensure that the surface of the straight bar has ribs with a height of at least 0.5 mm to enhance the anchoring performance with the sleeve. Next, prepare the inflection point sleeve 2. According to the required dimensions, select steel or thermoplastic engineering plastic as the raw material to prepare the sleeve body 21, and process internal threads 212 on its inner wall. Install tapered sleeves 24 at both ends of the inflection point sleeve 2, ensure that they are threadedly connected to the sleeve body 21, and set rubber sealing rings 243 at the FRP bar 1 insertion ports of the tapered sleeves 24. The rubber sealing rings 243 are connected to the tapered cylinders 241 by hot melting to ensure tightness. Then, insert the FRP bar 1 into the tapered sleeve 24 and tighten the tapered sleeve 24 to ensure a tight connection and meet the anchoring length requirements. Inject the epoxy resin 3 grouting material into the sleeve through the grouting port 22 until it overflows from the slurry outlet 23, ensuring that the inside of the inflection point sleeve 2 is filled with the epoxy resin 3 to improve the bonding force between the FRP bar and the sleeve. Finally, after waiting for the epoxy resin 3 to completely cure, the closed FRP stirrup connected by the inflection point sleeve can be obtained.

[0029] In summary, the present utility model not only effectively solves the problem of insufficient strength of FRP stirrups at the inflection points, but also significantly improves the performance and durability of the stirrups through a unique connection method and grouting material selection, and is applicable to structural engineering applications under various harsh environmental conditions.

[0030] The above are only the preferred embodiments of the present utility model and are not used to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the foregoing technical solutions or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A closed FRP stirrup connected by an inflection sleeve, comprising an FRP bar (1), an inflection sleeve (2) and an epoxy resin (3), characterized in that: Adjacent FRP bars (1) are connected via inflection sleeves (2) to form closed FRP stirrups, and each inflection sleeve (2) is filled with epoxy resin (3).

2. The closed FRP stirrup connected by an inflection sleeve according to claim 1, characterized in that: The inflection point sleeve (2) comprises a sleeve body (21) and a grouting port (22) and a grouting port (23) arranged on the sleeve body (21), and conical sleeve heads (24) are threadedly connected at both ends of the sleeve body (21).

3. The closed FRP stirrup connected by an inflection sleeve according to claim 2, characterized in that: The sleeve body (21) is provided with an internal thread.

4. The closed FRP stirrup connected by an inflection sleeve according to claim 2, characterized in that: The conical sleeve (24) is composed of a conical cylinder (241) and an interface threaded section (242), and a rubber sealing ring (243) is installed in the conical cylinder (241).

5. The closed FRP stirrup connected by an inflection sleeve according to claim 1, characterized in that: The anchoring length of the FRP bar (1) in the inflection point sleeve (2) is not less than 10 times the diameter of the FRP bar (1).

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