Composite system concrete beam based on FRP bars and construction method thereof

Abstract

The invention belongs to the technical field of building structures, and particularly discloses a composite system concrete beam based on FRP ribs and a construction method of the composite system concrete beam. The beam is formed by integrally pouring the UHP-ECC and the FRP rib framework, the characteristics of high strength, high ductility and multi-seam cracking of the UHP-ECC are fully utilized, the UHP-ECC and the advantages of light weight, high strength and corrosion resistance of the FRP ribs work cooperatively, and the structural performance of high bearing capacity, high ductility, high durability and light weight is achieved. The invention further provides a full-process method which can be implemented industrially and is suitable for various engineering scenes such as buildings, bridges and oceans, wherein the full-process method comprises the steps of batching, framework processing, formwork installation, pouring, maintenance and post-treatment.

Description

Technical Field

[0001] This invention belongs to the field of building structure technology, specifically relating to a composite concrete beam based on FRP reinforcement and its construction method. Background Technology

[0002] Traditional reinforced concrete beams suffer from problems such as easy corrosion of reinforcing bars, heavy weight, insufficient ductility, poor crack resistance, and insufficient durability in harsh environments, which seriously restrict the service life and safety of engineering structures.

[0003] In recent years, FRP bars have been attempted to replace ordinary steel bars due to their advantages such as lightweight, high strength, and corrosion resistance; new matrix materials such as ECC (Engineered Cementitious Composites) and UHPC (Ultra-High Performance Concrete) have also been used to improve the ductility and crack control of beams.

[0004] However, FRP bars have a low elastic modulus, resulting in large deflection and crack width in the components, and the failure is brittle; ECC has limited compressive strength, making it difficult to meet high load-bearing requirements; UHPC has extremely high strength but insufficient ductility, resulting in a high risk of brittle failure; the bond performance between FRP bars and ordinary concrete or UHPC needs to be improved.

[0005] Therefore, there is an urgent need for a new type of composite beam system and construction method that combines high load-bearing capacity, high ductility, high durability and lightweight. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a composite concrete beam based on FRP reinforcement and its construction method. By combining FRP reinforcement with UHP-ECC, a novel composite beam with high load-bearing capacity, high ductility, high durability, and lightweight is obtained.

[0007] The composite concrete beam based on FRP reinforcement of the present invention includes:

[0008] Ultra-high performance, high ductility cement-based composite material UHP-ECC matrix; and

[0009] FRP reinforcing skeleton embedded in the UHP-ECC matrix;

[0010] The UHP-ECC has a compressive strength of 80 MPa or higher and an ultimate tensile strain of 6% or higher; the FRP reinforcement skeleton includes at least FRP longitudinal reinforcement; and the average bond strength between the UHP-ECC and the FRP reinforcement skeleton is 15 MPa or higher.

[0011] The FRP reinforcement skeleton also includes FRP stirrups.

[0012] The FRP reinforcement is selected from one or more of AFRP, BFRP, CFRP or GFRP, and the surface is treated by sandblasting, winding or sanding.

[0013] The beams have rectangular, T-shaped, box-shaped, or I-shaped cross-sections; the reinforcement ratio is 0.5%–4%.

[0014] The present invention also provides a method for constructing the above-mentioned composite concrete beam based on FRP reinforcement, comprising the following steps:

[0015] S1. Stir to prepare UHP-ECC matrix;

[0016] S2. FRP reinforcement skeleton processing: Bind or mechanically connect the FRP longitudinal bars and stirrups to form an integral skeleton;

[0017] S3. After setting up the template, pour the UHP-ECC mixture into the template and vibrate it to compact it.

[0018] S4. After initial setting, cover with film or steam for 24–48 hours, then allow to cure naturally.

[0019] S5. Cut, chamfer, or apply anti-corrosion coating to the ends of the beam.

[0020] The fiber used in the UHP-ECC in S1 is PE fiber.

[0021] The S4 process involves curing at room temperature.

[0022] The beneficial effects of this invention are:

[0023] Compared to traditional reinforced concrete beams and FRP-reinforced concrete beams, the beams of this invention have a smaller self-weight, better crack resistance, and superior durability in harsh environments. They also avoid the problem of low elastic modulus of FRP reinforcement, which leads to larger deflections and crack widths during operation. Furthermore, the bonding performance between FRP reinforcement and UHP-ECC is better, resulting in lower crack width and propagation rate compared to reinforced concrete and FRP-reinforced concrete beams. Compared to ECC beams, this invention has a higher load-bearing capacity, and for the same load-bearing capacity, the beam size is smaller, making it suitable for structural engineering projects with high load-bearing requirements. Compared to UHPC beams, the beam structure of this invention has better ductility, exhibiting better seismic performance under dynamic loads such as earthquakes, with smaller crack widths, more cracks, and greater beam deflection. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments are briefly introduced below.

[0025] Figure 1 This is a schematic diagram of a composite concrete beam structure.

[0026] Figure 2 Sectional view of beam AA with web reinforcement.

[0027] Figure 3 Cross-sectional view of beam BB with web reinforcement.

[0028] Figure 4 Sectional view of beam AA without stirrups.

[0029] Figure 5 Cross-sectional view of beam BB without stirrups.

[0030] Figure 6 This is a diagram showing the results of the cracking load test in the embodiment.

[0031] Figure 7 This is a diagram showing the results of the ultimate load test in the embodiment.

[0032] Figure 8 This is a diagram showing the deflection test results in the embodiment.

[0033] In the diagram: 1. UHP-ECC matrix; 2. Upper FRP longitudinal reinforcement; 3. FRP stirrups; 4. Lower FRP longitudinal reinforcement. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] Example 1

[0036] See Figure 1 As shown, the composite concrete beam based on FRP reinforcement provided in this embodiment has a rectangular cross-section and a reinforcement ratio of 0.5%–4%. The beam structure includes:

[0037] Ultra-high performance, high ductility cement-based composite material UHP-ECC matrix; and FRP reinforcement skeleton embedded in the UHP-ECC matrix;

[0038] Among them, the compressive strength of UHP-ECC is above 80MPa and the ultimate tensile strain is above 6%; the FRP reinforcement skeleton must contain at least FRP longitudinal reinforcement, see reference. Figures 4 to 5 As shown, the average bond strength between UHP-ECC and FRP reinforcement is above 15 MPa.

[0039] See Figure 2 and Figure 3 As shown, the FRP reinforcement skeleton also includes FRP stirrups.

[0040] Specifically, the FRP reinforcement is selected from one or more of AFRP, BFRP, CFRP or GFRP, and the surface is treated by sandblasting, winding or sanding.

[0041] The above-mentioned method for constructing composite concrete beams based on FRP reinforcement includes the following steps:

[0042] S1. Stir to form UHP-ECC matrix. The fiber used in UHP-ECC is PE fiber.

[0043] S2. FRP reinforcement skeleton processing: Bind or mechanically connect the FRP longitudinal bars and stirrups to form an integral skeleton;

[0044] S3. After setting up the template, pour the UHP-ECC mixture into the template and vibrate it to compact it.

[0045] S4. After initial setting, cover with film or steam for 24–48 hours, then allow to cure naturally at room temperature.

[0046] S5. Cut, chamfer, or apply anti-corrosion coating to the ends of the beam.

[0047] Experimental Example 1

[0048] As shown in Table 1 below, a numbering and classification experiment was conducted.

[0049] Table 1

[0050]

[0051] The test results are as follows Figures 6 to 8 As shown:

[0052] ① By comparing the different reinforcement ratios of beams 1-6, it can be seen that the cracking load of the beam first increases and then tends to be horizontal. It can be seen that the reinforcement ratio has a limited impact on the cracking load of the beam. This is because the cracking load of the beam is mainly determined by the tensile properties of the UHP-ECC material. The ultimate load of the beam increases with the increase of the reinforcement ratio, and the magnitude gradually slows down.

[0053] ② Comparing beams No. 3 and No. 7, and No. 10 and No. 11, it can be seen that the beam with GFRP bottom longitudinal reinforcement has a relatively small cracking load. This is because the bond between GFRP reinforcement and concrete is weaker than that between steel reinforcement and concrete. Therefore, the beam cracks earlier. However, due to the high tensile strength of GFRP reinforcement, the ultimate load of the beam is higher.

[0054] ③ Comparing the deflections of beams with different reinforcement ratios (numbers 1-6), the deflection first increases and then decreases with increasing reinforcement ratio. This is because when the reinforcement ratio is small, the ultimate bearing capacity of the beam is small, resulting in a small deflection when the ultimate bearing capacity is reached. As the reinforcement ratio increases, both the ultimate bearing capacity and stiffness of the beam increase, thus resulting in a smaller deflection. Comparing the deflections of beams with different types of concrete, it can be seen that the UHP-ECC beam has the largest deflection and the best ductility.

[0055] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A composite concrete beam based on FRP reinforcement, characterized in that, include: UHP-ECC matrix, an ultra-high performance, high-ductility cement-based composite material; as well as FRP reinforcing skeleton embedded in the UHP-ECC matrix; The UHP-ECC has a compressive strength of 80 MPa or higher and an ultimate tensile strain of 6% or higher; the FRP reinforcement skeleton includes at least FRP longitudinal reinforcement; and the average bond strength between the UHP-ECC and the FRP reinforcement skeleton is 15 MPa or higher.

2. The composite concrete beam based on FRP reinforcement according to claim 1, characterized in that, The FRP reinforcement skeleton also includes FRP stirrups.

3. The composite concrete beam based on FRP reinforcement according to claim 2, characterized in that, The FRP reinforcement is selected from one or more of AFRP, BFRP, CFRP or GFRP, and the surface is treated by sandblasting, winding or sanding.

4. The composite concrete beam based on FRP reinforcement according to claim 2, characterized in that, The beams have rectangular, T-shaped, box-shaped, or I-shaped cross-sections; the reinforcement ratio is 0.5%–4%.

5. A method for constructing a composite concrete beam based on FRP reinforcement, characterized in that, Includes the following steps: S1. Stir to prepare UHP-ECC matrix; S2. FRP reinforcement skeleton processing: Bind or mechanically connect the FRP longitudinal bars and stirrups to form an integral skeleton; S3. After setting up the template, pour the UHP-ECC mixture into the template and vibrate it to compact it. S4. After initial setting, cover with film or steam for 24–48 hours, then allow to cure naturally. S5. Cut, chamfer, or apply anti-corrosion coating to the ends of the beam.

6. The method for constructing a composite concrete beam based on FRP reinforcement according to claim 5, characterized in that, The fiber used in the UHP-ECC in S1 is PE fiber.

7. The method for constructing a composite concrete beam based on FRP reinforcement according to claim 5, characterized in that, The S4 process involves curing at room temperature.

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