Construction process for reinforcing prefabricated concrete components with 3D fiber system

Abstract

The application provides a construction process for reinforcing a prefabricated concrete member by a 3D fiber system and relates to the technical field of civil engineering structure reinforcement. The process comprises the following steps: preparing a bottom U-shaped fiber, L-shaped fiber anchoring, longitudinal U-shaped fiber anchoring and vertical U-shaped fiber, placing the fibers into epoxy resin glue for impregnation, scraping off the excess glue on the fiber strips, and pasting the above fiber structures on a beam according to a certain order to form a 3D fiber system, so that the fiber strips are prevented from peeling off and breaking, and the high-strength performance of the fiber material is fully utilized.

Description

Technical Field

[0001] This invention relates to the field of civil engineering structural reinforcement technology, and more specifically, to a construction process for reinforcing precast concrete components using a 3D fiber system. Background Technology

[0002] Fiber-reinforced polymer (CFRP) reinforced concrete structures is an important structural strengthening technology. It improves the load-bearing capacity, ductility, and durability of concrete structures by bonding or embedding fiber materials on the surface. Studies have shown that fiber reinforcement can significantly improve the seismic performance, crack resistance, and durability of concrete structures, while also extending their service life. Regarding the research background, scholars have conducted in-depth research on prestressed fiber-reinforced concrete structures.

[0003] Existing reinforcement methods and designs, whether External Bonded (EB) or Near Surface Mounted (NSM) technologies, primarily utilize fibers to reinforce concrete structures in a 2D plane. This can improve the flexural capacity, ductility, and energy dissipation of concrete structures to some extent. However, due to imperfect anchoring mechanisms, the improvement effect is not significant, and the shear capacity of the concrete structure is not effectively enhanced. Furthermore, fiber-reinforced concrete structures in a 2D plane are prone to fiber debonding failure under load, failing to fully utilize the tensile strength of carbon fiber materials and reducing the load-bearing capacity of the concrete structure. In addition, traditional 2D fiber materials suffer from low elastic modulus and poor ductility, resulting in poor crack resistance and seismic performance of related components, which urgently need to be addressed. Summary of the Invention

[0004] This invention discloses a construction process for reinforcing precast concrete components with a 3D fiber system, which aims to improve the problems of existing reinforced beams.

[0005] The present invention adopts the following solution:

[0006] This application provides a construction process for reinforcing precast concrete components with a 3D fiber system, including the following steps:

[0007] S1. Preparation of epoxy resin adhesive;

[0008] S2. Preparation of fiber strips: Prepare bottom U-shaped fibers, L-shaped fiber anchors, longitudinal U-shaped fiber anchors and vertical U-shaped fibers, and impregnate them with epoxy resin, then scrape off the excess resin on the fiber strips;

[0009] S3. Clean the surface of the beam to be reinforced and apply the prepared epoxy resin adhesive evenly to the bonding surface of the beam.

[0010] S4. Attach the bottom U-shaped fiber to the bottom surface of the beam and attach the extended part to the left and right sides of the beam. Remove the internal air bubbles along the fiber direction until the strip of bottom U-shaped fiber is smoothed evenly so that the bottom U-shaped fiber is completely bonded to the beam.

[0011] S5. Attach the two L-shaped fiber anchors to the left bottom and left side of the beam, and the right bottom and right side, respectively. Remove the internal air bubbles along the fiber direction until the L-shaped fiber strips are evenly spread so that the L-shaped fibers are completely bonded to the beam to protect the bent parts and prevent shear damage.

[0012] S6. Wrap the two longitudinal U-shaped fibers around the side surface of the beam and remove the internal air bubbles along the direction of the fiber strips until the longitudinal U-shaped fibers are spread evenly so that the longitudinal U-shaped fibers are completely bonded to the beam to achieve longitudinal anchoring and prevent the bottom U-shaped fibers from peeling off and being damaged.

[0013] S7. Adhere the vertical U-shaped fibers to the front, back, and bottom sides of the beam, and remove the internal air bubbles along the direction of the fiber strips until the vertical U-shaped fibers are spread evenly, so that the vertical U-shaped fibers are completely bonded to the beam to improve the beam's shear bearing capacity.

[0014] S8. Place the installed beam for curing.

[0015] Further, in step S1, E2500S epoxy resin adhesive is used. Glue A and Glue B are mixed at a mass ratio of 2:1, stirred for 5 minutes, and allowed to stand for 20 minutes to obtain epoxy resin adhesive.

[0016] Furthermore, in step S6, a gap is left between the two longitudinal U-shaped fiber anchoring strips on the left and right sides to improve the beam's impact resistance.

[0017] Furthermore, the curing time is 1-2 weeks.

[0018] Furthermore, the fiber is carbon fiber cloth.

[0019] Beneficial effects:

[0020] This invention utilizes a sophisticated 3D fiber anchoring system to protect fiber strips from peeling damage, thereby fully leveraging the high strength of the fiber material. The primary anchoring mechanism is the bent portion of the bottom U-shaped fiber; longitudinal U-shaped fiber anchoring protects the bottom U-shaped fiber from peeling damage; and L-shaped fiber anchoring protects the bent portion from shear failure. This 3D fiber system fully utilizes the high strength of the fiber material, effectively improving the material strength utilization rate of traditional 2D fiber technology. Simultaneously, this anchoring system and shear-resistant system effectively control the slip relationship between the fiber and concrete, improving the deformation performance of related components. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the 3D fiber system reinforcement layout for a construction process of 3D fiber system reinforcement of precast concrete components according to an embodiment of the present invention;

[0022] Figure 2 This is a theoretical analysis diagram of the 3D fiber system of the present invention;

[0023] Figure 3 This is a schematic diagram of the stress-strain relationship of concrete after cracking of the 3D fiber system of the present invention. Figure 3 ;

[0024] Figure 4 This is a schematic diagram of the carbon fiber model of the 3D fiber system of the present invention;

[0025] Figure 5 This is a schematic diagram of fiber breakage in the 3D fiber system of Embodiment 3 of the present invention during an experiment;

[0026] Figure 6 This is a schematic diagram of fiber breakage in the 2D fiber system used as a comparative experiment in Embodiment 3 of the present invention during the experiment;

[0027] Icons: 1. Beam, 2. Bottom U-shaped fiber, 3. L-shaped fiber, 4. Vertical U-shaped fiber, 5. Chamfer, 6. Detailed Implementation

[0028] Example 1

[0029] Combination Figure 1 As shown in the figure, this embodiment provides a construction process for reinforcing precast concrete components with a 3D fiber system, including the following steps:

[0030] S1. Preparation of epoxy resin adhesive;

[0031] S2. Preparation of fiber strips: Prepare bottom U-shaped fibers 2, L-shaped fibers 3, longitudinal U-shaped fibers 4 and vertical U-shaped fibers 5, and impregnate them with epoxy resin. Then scrape off the excess resin on the fiber strips. Here, the soaking time is 3 minutes to ensure that the fiber strips are completely impregnated.

[0032] S3. Clean the surface of the beam 1 to be reinforced, ensuring that the surface of the beam 1 is clean and flat. Apply the prepared epoxy resin adhesive evenly to the bonding surface of the beam 1. Here, it is enough to make the surface of the beam 1 flat; there is no need to sand it to a smooth finish.

[0033] S4. Attach the bottom U-shaped fiber 2 to the bottom surface of beam 1 and attach the extended part to the left and right sides of beam 1. Remove the internal air bubbles along the fiber direction until the strip of bottom U-shaped fiber 2 is smoothed evenly so that bottom U-shaped fiber 2 is completely bonded to beam 1.

[0034] S5. Anchor the two L-shaped fibers 3 to the left bottom and left side, and the right bottom and right side of the beam 1 respectively, and remove the internal air bubbles along the fiber direction until the strips of the L-shaped fibers 3 are smoothed evenly so that the L-shaped fibers 3 are completely bonded to the beam 1 to protect the bent parts and avoid shear damage.

[0035] S6. Wrap the two longitudinal U-shaped fibers 4 around the side surface of the beam 1 and remove the internal air bubbles along the direction of the fiber strip until the longitudinal U-shaped fibers 4 are spread evenly so that the longitudinal U-shaped fibers 4 are completely bonded to the beam 1 to achieve longitudinal anchoring and prevent the bottom U-shaped fibers 2 from peeling and being damaged.

[0036] S7. Adhere the vertical U-shaped fiber 5 to the front and rear sides and bottom of the beam 1, and remove the internal air bubbles along the direction of the fiber strip until the vertical U-shaped fiber 5 is spread evenly, so that the vertical U-shaped fiber 5 is completely bonded to the beam 1 to improve the shear bearing capacity of the beam 1.

[0037] S8. Place the installed beam 1 for curing, which takes 1-2 weeks.

[0038] In this embodiment, in step S1, E2500S epoxy resin adhesive is used. Glue A and Glue B are mixed at a mass ratio of 2:1, stirred for 5 minutes, and allowed to stand for 20 minutes to obtain epoxy resin adhesive.

[0039] In this embodiment, the bottom U-shaped fiber 2, L-shaped fiber 3 anchoring, longitudinal U-shaped fiber 4 anchoring, and vertical U-shaped fiber 5 are made of carbon fiber cloth, which is cut to size.

[0040] In step S6, gaps are left between the two longitudinal U-shaped fiber 4 anchoring strips on the left and right sides to improve the impact resistance of beam 1. In addition, the 3D fibers form chamfers 6 on the sides of beam 1.

[0041] In this embodiment, a 3D fiber reinforcement system is formed on the beam 1 by setting the bottom U-shaped fiber 2, the L-shaped fiber 3 for anchoring, the longitudinal U-shaped fiber 4 for anchoring, and the vertical U-shaped fiber 5. The 3D fiber system consists of a tensile system, a shear system, and an anchoring system. The tensile system consists of the bottom U-shaped fiber 2, the shear system consists of the vertical U-shaped fiber 5, and the anchoring system consists of the bottom U-shaped fiber 2, the longitudinal U-shaped fiber 4 for anchoring, and the L-shaped fiber 3 for anchoring.

[0042] Regarding the bottom U-shaped fiber 2, the carbon fiber strips can improve the bending resistance of beam 1. The 90° bends on both sides of the fiber strips can limit the slippage between the fiber and the concrete, improve the integrity of the fiber and the component, thereby effectively reducing fiber peeling failure and fully utilizing the bending resistance of carbon fiber. L-shaped fiber 3 anchorage protects the bending point and prevents shear failure. Longitudinal U-shaped fiber 4 anchorage prevents peeling failure of the bottom U-shaped fiber 2, and the gaps left improve the impact resistance of the component. Vertical U-shaped fiber 5 can effectively improve the shear capacity of the component.

[0043] Compared to existing 2D fiber technology, this invention's embodiment utilizes a sophisticated 3D fiber anchoring system to prevent fiber strips from peeling and damage, thereby fully leveraging the high strength of the fiber material. Specifically, the bent portion of the bottom U-shaped fiber 2 is the primary anchoring method. Therefore, this 3D fiber system can fully utilize the high strength of the fiber material, effectively improving the material strength utilization rate of traditional 2D fiber technology. Through the anchoring system and shear resistance system, the slip relationship between the fiber and concrete can be effectively controlled, improving the deformation performance of the relevant components. In other words, compared to traditional 2D fiber technology, this invention's 3D fiber system can control fiber-concrete slippage to achieve a load-deflection curve similar to that of a properly reinforced beam 1, thereby effectively improving the deformation capacity of the relevant components. Furthermore, this 3D fiber spatial system can significantly increase the bonding area between the fiber and concrete, thereby improving the tensile properties of the concrete after cracking, and ultimately enhancing the overall flexural stiffness of the relevant components.

[0044] Example 2

[0045] To calculate the shear and bending resistance of this 3D fiber system, a theoretical analysis and calculation model is also provided. Specifically, since the effect of the fibers is negligible before concrete cracking, the cracking bending moment M of the concrete at this time is... cr With corresponding curvature φ cr It can be calculated as:

[0046] M cr =f cr bh 2 / 6;

[0047] φ cr =2f cr / (E c h);

[0048] in,

[0049] Among them, f c ρ is the maximum strength of concrete under compression; b is the cross-sectional width; h is the cross-sectional height;

[0050] The equilibrium relationship between force and bending moment is as follows: Figure 2 As shown, in Figure 2 In the diagram, (a) shows the cross-sectional dimensions of the 3D fiber system at a certain location on beam 1, while (b) is a schematic diagram of the forces acting within that cross-section. Figure 2 (a) and (b) in the figure, and a schematic diagram of the stress-strain relationship of the concrete after cracking. Figure 3 The model description yields the following formula model:

[0051] F c -F t -F bf =0;

[0052] M c +M t +M bf -P app / 2×L i =0;

[0053]

[0054]

[0055]

[0056] F bf =ε f_app ·E f_app ·A f ;

[0057] ε f_app =ε cx (hx) / x;

[0058]

[0059] M bf =ε f_app ·E f_app ·A f ·(hX);

[0060]

[0061] Among them, F c F t F bf These represent the tensile and compressive stresses in the concrete, and the tensile stress in the bottom fibers, respectively; M c M t M bf ε represents the bending moment of the concrete and the bottom fiber, respectively. cx ε represents the concrete strain on a layer at a distance x from the neutral axis; t_y f represents the strain of the tensile concrete layer at a distance y from the bottom fiber; cr app According to εf_app The calculated composite stress of the concrete, such as Figure 4 As shown.

[0062] Where, f(ε) cx ) for using ε cx The obtained concrete compressive stress; X is the distance from the neutral axis to the top concrete layer; y is the distance from the neutral axis to the side fiber layer for calculating tensile contribution; A f p is the cross-sectional area of ​​the bottom fiber. app For mid-span load; L i E is the distance from the support to the i-th section; f E represents the elastic modulus of the fiber. t f is the elastic modulus of the concrete in the tension zone. t ε represents the tensile strength of concrete. f_ult ε represents the strain at which the fiber is finally completely peeled off. cr app This represents the strain from cracking to failure of the concrete.

[0063] E f_app This is a modified modulus to describe the displacement caused by interfacial slip and fiber tension. Since the fiber is bent and anchored, complete peeling would result in a modulus decrease of 0.3E. f Here it is assumed that from the start to the end of loading, the apparent modulus of the fiber (fiber model) includes fiber elongation and slip (see...). Figure 4 ),but:

[0064] E f_app =(1-(ε) i / ε ult ) 0.1 0.3E f ;

[0065] The deflection of the i-th span within the span can be calculated as follows:

[0066]

[0067] F bon d represents the bonding strength between the fiber and the concrete, which can be calculated as follows:

[0068]

[0069] τ max =1.35 + 0.25β w f cr +0.62f cr ;

[0070] S f = -0.06 + (0.88 - 0.23β) w 2 )f cr -0.5β w 0.5 ;

[0071]

[0072] In this embodiment, the formula for the shear bearing capacity of the 3D fiber-reinforced concrete member is:

[0073]

[0074] Where n is the number of strips attached to the side of the cross-section; ε i ε is the strain at the i-th section; ult f is the strain when the fiber is finally completely peeled off. cr τ represents the stress at which concrete cracks; b represents the width of the concrete; τ max S represents the maximum shear stress within the concrete. f β represents the shear strength of the fiber. w This is the concrete strength development coefficient.

[0075] The above formula model verifies that the 3D fiber system obtained through this design possesses good shear and bending resistance. Furthermore, the formula can be used to calculate the required dimensions and installation positions of the bottom U-shaped fiber 2, L-shaped fiber 3, longitudinal U-shaped fiber 4, and vertical U-shaped fiber 5 within the 3D fiber system for beam 1 of the corresponding dimensions, thus providing dimensional standards for the reinforcement of beam 1.

[0076] Example 3

[0077] In one experimental embodiment, E2500S adhesive was used. Glue A and Glue B were mixed at a mass ratio of 2:1, stirred for 5 minutes, and allowed to stand for 20 minutes to obtain epoxy resin adhesive.

[0078] like Figure 1 As shown, the bottom U-shaped fiber 2 used in the experiment had dimensions of 914mm × 152mm, the L-shaped fiber 3 had an anchoring dimension of 272mm × 152mm, the longitudinal U-shaped fiber 4 had an anchoring dimension of 472mm × 152mm with a gap width of 20mm, and the vertical U-shaped fiber 5 had dimensions of 610mm × 456mm. The cut fiber strips were immersed in epoxy resin for 3 minutes to ensure complete wetting, and then excess resin was scraped off the fibers.

[0079] Clean the dust off the surface of beam 1, and apply the prepared epoxy resin adhesive evenly to the bonding surface of beam 1. After brushing, ensure that the surface of the epoxy resin adhesive layer is clean.

[0080] The fully impregnated bottom U-shaped fibers 2 are longitudinally attached to the bottom surface of beam 1, and the extended portions are attached to the left and right sides of beam 1. Air bubbles are expelled along the fiber direction until the fiber strips are smoothed evenly, ensuring complete adhesion between the fiber strips and beam 1. The fully impregnated L-shaped fibers 3 are anchored and attached to the left or right bottom and sides of beam 1, and air bubbles are expelled along the fiber direction until the fiber strips are smoothed evenly, ensuring complete adhesion between the fiber strips and beam 1. The same operation is performed on the other side of beam 1. The longitudinal U-shaped fibers 4 are anchored and wrapped around the side surface of beam 1, and air bubbles are expelled along the fiber direction until the fiber strips are smoothed evenly, ensuring complete adhesion between the fiber strips and beam 1. It is important to note that a 20mm gap should be left between these two fiber strips. Finally, the vertical U-shaped fibers 5 are attached to the front and rear sides and bottom of beam 1, and air bubbles are expelled along the fiber direction until the fiber strips are smoothed evenly, ensuring complete adhesion between the fiber strips and beam 1. After installing test beam 1, place the installed beam 1 in a clean environment to cure for 10 days.

[0081] Destruction tests were conducted on beam 1, which was cured using a 3D fiber system in this embodiment, and beam 1 reinforced using 2D fiber technology. The results are as follows: Figure 5 and Figure 6 As shown in the figure. Experimental results show that the average load-bearing capacity of beam 1 reinforced with the 3D fiber system in this embodiment is 101 kN, and the maximum load-bearing capacity is 104 kN. In contrast, the average load-bearing capacity of the 2D fiber reinforcement technology is 62 kN, and the maximum load-bearing capacity is 72 kN. Compared to the 2D fiber reinforcement technology, the average fiber stress capacity utilized by beam 1 reinforced in this embodiment is 162.9%, and the maximum stress capacity is 144.4%. In terms of failure mode, beam 1 reinforced with the 3D fiber system did not experience fiber debonding failure. Therefore, compared with 2D fiber reinforced concrete technology, this invention can effectively improve fiber utilization, fully utilize the tensile strength of the fiber strips, improve the failure mode of beam 1, and thus improve the load-bearing capacity of concrete.

[0082] It should be understood that the above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0083] The accompanying drawings used in the above description of the embodiments only illustrate certain embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

Claims

1. A construction process for reinforcing a precast concrete member with a 3D fiber system, characterized in that, The method comprises the following steps: S1, preparing epoxy resin glue; S2, preparing fiber strips: preparing bottom U-shaped fiber, L-shaped fiber anchoring, longitudinal U-shaped fiber anchoring and vertical U-shaped fiber, and placing them in the epoxy resin glue for impregnation, and then scraping off the excess glue on the fiber strips; S3, cleaning the surface of the beam to be reinforced, and evenly brushing the prepared epoxy resin glue on the bonding surface of the beam; S4, bonding the bottom U-shaped fiber to the bottom surface of the beam and bonding the extended part to the left and right side surfaces of the beam, and discharging the internal bubbles along the fiber direction until the bottom U-shaped fiber strip is evenly applied, so that the bottom U-shaped fiber is completely bonded with the beam; S5, bonding two L-shaped fiber anchoring to the left bottom surface and the left side surface of the beam, and the right bottom surface and the right side surface of the beam respectively, and discharging the internal bubbles along the fiber direction until the L-shaped fiber strip is evenly applied, so that the L-shaped fiber is completely bonded with the beam to protect the bending part and avoid shear failure; S6, wrapping two longitudinal U-shaped fibers to the side surface of the beam and discharging the internal bubbles along the direction of the fiber strip until the longitudinal U-shaped fiber is evenly applied, so that the longitudinal U-shaped fiber is completely bonded with the beam to achieve longitudinal anchoring to prevent the bottom U-shaped fiber from being peeled off; S7, bonding the vertical U-shaped fiber to the front and rear side surfaces and the bottom surface of the beam, and discharging the internal bubbles along the direction of the fiber strip until the vertical U-shaped fiber is evenly applied, so that the vertical U-shaped fiber is completely bonded with the beam to improve the shear bearing capacity of the beam; S8, placing the installed beam for curing.

2. The construction process of 3D fiber system reinforced precast concrete members according to claim 1, characterized in that, In step S1, E2500S epoxy resin glue is used, A glue and B glue are mixed in a mass ratio of 2:1, stirred for 5 minutes and left for 20 minutes to obtain the epoxy resin glue.

3. The construction process of 3D fiber system reinforced precast concrete members according to claim 1, characterized in that, In step S6, a gap is left between the two longitudinal U-shaped fiber anchoring strips on the left and right sides to improve the impact resistance of the beam.

4. The construction process of 3D fiber system reinforced precast concrete members according to claim 1, characterized in that, The curing time period is 1-2 weeks.

5. The construction process of 3D fiber system reinforced precast concrete members according to claim 1, characterized in that, The fiber is a carbon fiber cloth.

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