FRP prestress tensioning device for reduced scale model test

Abstract

The utility model relates to an FRP (Fiber Reinforce Plastic) prestress tensioning device for a reduced scale model test. The FRP prestress tensioning device comprises a fixed reaction frame, an integrated clamp, a limiter, a screw rod, a force sensor and a common bolt, the fixed counter-force frame is arranged at the end, to be tensioned, of a component, the integrated clamp penetrates through an upper steel plate and a lower steel plate of FRP in a fastened mode through common bolts, the limiting stopper limits the screw to drive the integrated clamp to rotate in the tensioning process, it is guaranteed that the position of the integrated clamp is straight, and the screw is sequentially connected with the integrated clamp, the force sensor and the fixed counter-force frame. The utility model further discloses an FRP prestress tensioning method for the reduced scale model test, and the screw rod is adjusted to reach the prestress meeting the design requirement by monitoring the change of the real-time tensioning force of the force sensor. The device has the characteristics of high efficiency, simplicity, convenience, high precision, low cost, high repeated utilization rate and the like, and can be applied to indoor tests and construction sites of reduced scale model tests.

Description

Technical Field

[0001] This utility model relates to the field of prestressed structure engineering, specifically to an FRP prestressing tensioning device for scaled-down model testing. Background Technology

[0002] Fiber-reinforced polymer (FRP) composites possess excellent mechanical properties, such as high strength, lightweight, and corrosion resistance, making them a widely used new type of material in structural reinforcement, bridge construction, and other fields. Prestressed FRP effectively reduces the structure's self-weight and inertial loads, improving its overall performance and seismic resistance, thus providing a reliable guarantee for the structure's safe operation. Furthermore, FRP materials exhibit excellent prestress retention performance, maintaining a stable prestress level even under long-term stress, and are not prone to relaxation or creep, ensuring the long-term stability of the structure.

[0003] Commonly used equipment for FRP prestressing includes a tensioning machine, prestressing anchors, and a prestressing application system. The tensioning machine is the key equipment for applying prestress; it is typically driven by a hydraulic system and can apply the required tension to the FRP. Prestressing anchors are used to secure the prestressed FRP material, and their design requirements dictate that they can effectively transfer the prestress to the structure. The prestressing application system controls the prestressing process, including monitoring and adjusting the tension force to ensure stable prestressing application.

[0004] In structural engineering, scaled-down model testing is a common method for evaluating structural performance under different loading conditions. For scaled-down model testing of complex structures, it is typically necessary to simulate prestressing tension in the real structure to accurately assess its behavior in actual engineering projects. However, traditional prestressing tensioning devices have several limitations. First, traditional devices are usually designed for prestressing treatment of large structures, and their size and operation may not be suitable for scaled-down model testing. This leads to problems such as inconvenience in operation and excessive space occupation when using traditional devices in scaled-down tests, limiting the flexibility and operability of the experiment. Second, the application range of traditional prestressing tensioning devices may not be flexible enough to meet the needs of scaled-down model testing. Because the structural dimensions and loads in scaled-down tests are relatively small, the required prestressing force may differ from that of traditional large-scale structures. Therefore, traditional devices may not be able to precisely control the amount of prestress applied, affecting the accuracy and reliability of the test. Furthermore, traditional devices are expensive, including equipment purchase, maintenance, and operation costs, which may increase the economic cost of the test and limit their widespread use in scientific research and engineering applications.

[0005] However, there is currently a lack of dedicated FRP prestressing tensioning devices and methods for scaled-down model tests. Existing FRP prestressing tensioning devices are typically used for structural reinforcement in practical engineering projects. For example, utility model patent CN110485748B discloses an anchoring structure and method for carbon fiber plates. Although multiple fixing clamps are connected in series to anchor the carbon fiber plates and can distribute the tensile force on the carbon fiber plates, it fails to meet the requirements of precise control of prestressing tension in scaled-down model tests. Therefore, it is necessary to develop an FRP prestressing tensioning device and method specifically for scaled-down model tests to meet the special requirements of the experiments and improve the accuracy, efficiency, and reliability of the tests.

[0006] Therefore, some people have submitted the following application to resolve the above issues;

[0007] Technical Comparison with Patent CN212693484U "A Long-Term Load Holding Test Device for FRP Bar Pull-Out Specimens Based on Spring Principle"

[0008] Patent CN212693484U describes a long-term load-bearing test device for FRP bar pull-out specimens designed using the spring principle, primarily for studying the bonding performance between FRP bars and the concrete interface. Our approach involves prestressing FRP sheets or fabrics at the bottom of the concrete to achieve a stable and safe prestressed tension state.

[0009] Patent CN212693484U uses an oil pump in conjunction with a ring-shaped pressure sensor to determine the loading level. Our S-shaped tension / compression sensor, however, has threaded holes at both ends pre-drilled to match the tension rod, allowing for real-time monitoring of the loading status with an accuracy class of C2 or C3.

[0010] Comparison with patent CN104264998B "For FRP quantitative control self-anchored prestressing tensioning machine"

[0011] Patent CN104264998B uses a jack to apply reaction force for prestressed FRP tensioning. Our design, in addition to using a through-hole jack, can also be operated using a simpler manual torque method.

[0012] Patent CN104264998B uses a self-anchoring method with locking function for prestressing tensioning. Our method, however, uses a ground anchoring method fixed to the ground or supporting structure for prestressing tensioning, which provides a more reliable fixation.

[0013] Technical comparison with patent CN107700867A "A prestressed tensioning device and method for flexible FRP sheets"

[0014] Patent CN107700867A utilizes the dual effects of end winding and corrugated clamping to prevent the flexible FRP sheet from sliding within the fixture. Our approach employs a roughened contact surface treatment, allowing for not only corrugated clamping but also wedge-shaped or toothed clamping, enabling more flexible clamping methods depending on the loading level and FRP type.

[0015] Patent CN107700867A provides a relatively ideal method for horizontal prestressed FRP tensioning. To address potential rotation issues during actual tensioning, we employ easily removable limiters to ensure horizontal tensioning of the FRP. Utility Model Content

[0016] To solve the above-mentioned technical problems, this utility model proposes an FRP prestressing tensioning device for scaled-down model tests. This device is efficient, simple, accurate, low-cost, and has a high reusability.

[0017] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0018] A prestressed FRP tensioning device for scaled-down model testing includes a fixed reaction frame, an integrated clamp, a limiter, a screw, a force sensor, and ordinary bolts. The fixed reaction frame is located at the end of the FRP to be tensioned. The integrated clamp secures the FRP with ordinary bolts. One side of the limiter is fixed to the fixed reaction frame with ordinary bolts, and the other side contacts the upper surface of the integrated clamp. One end of the screw passes through the middle of the U-shaped steel plate of the integrated clamp and is fixed with bolts. The other end of the screw passes through the outer end support of the fixed reaction frame and is fixed with bolts. The force sensor is located between the integrated clamp and the outer end support of the fixed reaction frame. The force sensor is S-shaped and passes through the screw.

[0019] As a further improvement to the structure of this utility model, the fixed reaction frame is composed of five steel plates, namely two side plates on the left and right, two end plates on the front and rear, and a bottom plate. The left and right side plates each have two round holes, the end plate away from the component has one round hole, and the upper surface of the end plate close to the component is flush with the lower surface of the integrated clamp.

[0020] As a further improvement to the structure of this utility model, the integrated clamp is composed of a U-shaped steel plate, an upper steel plate, a lower steel plate and ordinary bolts. The U-shaped steel plate has a chamfered interior and a central hole. The lower steel plate is integrally formed or welded with the U-shaped steel plate. The upper steel plate is detachable and its width is 5-20 mm lower than that of the lower steel plate. The upper and lower steel plates each have two rows of holes, with 2-4 holes in each row.

[0021] As a further improvement to the structure of this utility model, the contact surfaces of the upper and lower steel plates of the integrated fixture are roughened to be wedge-shaped, wave-shaped, or toothed.

[0022] As a further improvement to the structure of this utility model, the limiter is made of angle steel or channel steel, and the side plate connected to the fixed reaction frame has two round holes.

[0023] As a further improvement to the structure of this utility model, the screw thread connects to the force sensor, and the matching nut is respectively connected to the outer side of the reaction frame and the inner side of the integrated clamp U-shaped steel plate through the hole, which is medium or rough assembly; the ordinary bolt is connected to the reaction frame, integrated clamp and limiter through the hole, which is medium or rough assembly.

[0024] As a further improvement to the structure of this utility model, the force sensor is an S-shaped tension and compression sensor with digital display or signal output function, and has a threaded hole at the top and bottom. The measurement range is 0~100 kN and the accuracy class is C2 or C3.

[0025] As a further improvement to the structure of this utility model, the FRP is an FRP board or FRP cloth, and the length of the clamped section is the length of the upper and lower steel plates of the integrated clamp along the FRP direction.

[0026] This utility model discloses an operation method for an FRP prestressing tensioning device used in scaled-down model tests. The specific steps are as follows:

[0027] (a) FRP fixing: FRP passes through the upper and lower steel plates of the integrated fixture and is fastened with ordinary bolts;

[0028] (b) Centering: Tighten the ordinary bolts of the limiter to ensure that the fixed reaction frame, integrated clamp, force sensor and screw are horizontally aligned;

[0029] (c) Force sensor debugging: Connect the force sensor and the data acquisition system, and set and adjust the data acquisition parameters;

[0030] (d) Prestressing tensioning: Use a wrench to turn the nut of the screw or a through-hole jack to drive the screw, apply stress in stages, in the order of 25%, 50%, 75%, 100%, and 103% of the design tension stress, stabilize for 2-3 minutes, observe the force value change of the data acquisition system, and determine whether the FRP has slipped. If slippage occurs, slowly unload the FRP, remove the ordinary bolts of the integrated fixture, and repeat the operation according to steps (a) to (d).

[0031] (e) Fixing the FRP tensioning end: Install the FRP tensioning end anchorage. The installation process should be symmetrical, and there should be no loosening or misalignment after installation.

[0032] (f) FRP holding and screw unloading: Hold the FRP load to the design requirements, observe the force value changes of the data acquisition system during this period, and after there are no abnormalities, slowly unload the nut in contact with the fixed reaction frame. If the nut is not easy to remove, the nut in contact with the integrated fixture can be loosened.

[0033] (g) Device removal and FRP removal: Remove the limiter, screw, and force sensor in sequence, loosen the ordinary bolts of the integrated fixture, and cut off the excess FRP.

[0034] The beneficial effects of this utility model are as follows:

[0035] This utility model discloses an FRP prestressing tensioning device for scaled-down model testing, comprising a fixed reaction frame, an integrated clamp, a limiter, a screw, and a force sensor. The fixed reaction frame is positioned at the end of the component to be tensioned. The integrated clamp secures the FRP with ordinary bolts. One side of the limiter is fixed to the fixed reaction frame with ordinary bolts, and the other side contacts the upper surface of the integrated clamp. The screw is divided into two sections, connecting the integrated clamp, the force sensor, and the fixed reaction frame respectively. Through this structural design, the prestressing tensioning device adopts a modular design, enabling rapid disassembly and assembly of the components. This simplifies the assembly and adjustment process, improves assembly efficiency, and allows for flexible selection of components as needed, reducing costs. The segmented design of the screw allows for flexible length adjustment according to different testing requirements, while also improving reusability. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the prestressed tensioning device of this utility model;

[0037] Figure 2 This is a structural schematic diagram of the fixed reaction frame of this utility model;

[0038] Figure 3 This is a schematic diagram of the integrated clamp of this utility model;

[0039] Figure 4 This is a schematic diagram of the limiter of this utility model;

[0040] Figure 5 This is a schematic diagram of the screw structure of this utility model;

[0041] Figure 6 This is a schematic diagram of the force sensor of this utility model.

[0042] exist Figures 1 to 6 This includes:

[0043] 1. Fixed reaction frame, 2. Integrated clamp, 3. Limiter, 4. Screw, 5. Force sensor, 6. Ordinary bolt, 7. FRP. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0045] like Figures 1 to 6 As shown, an FRP prestressing tensioning device for scaled-down model testing includes a fixed reaction frame 1, an integrated clamp 2, a limiter 3, a screw 4, a force sensor 5, and a common bolt 6.

[0046] The fixed reaction frame 1 is installed at the end of the component to be tensioned according to design requirements and is fixed to the ground or supporting structure using an appropriate connection method. The integrated clamp 2 is fastened to the FRP 7 with ordinary bolts 6. The tightening force of the ordinary bolts does not exceed the load-bearing capacity of the FRP material to avoid damage or failure of the material. One side of the limiter 3 is fixed to the fixed reaction frame 1 with ordinary bolts 6, and the other side contacts the upper surface of the integrated clamp 2. One end of the screw 4 passes through the middle of the U-shaped steel plate of the integrated clamp 2 and is fixed with bolts. The other end of the screw 4 passes through the outer end bracket of the fixed reaction frame 1 and is fixed with bolts. The force sensor 5 is located between the integrated clamp 2 and the outer end bracket of the fixed reaction frame 1. The force sensor 5 is S-shaped and passes through the screw 4.

[0047] Furthermore, the fixed reaction frame 1 consists of five steel plates: two side plates on the left and right, two end plates on the front and rear, and a bottom plate.

[0048] It should be further pointed out that the left and right side plates of the fixed reaction frame 1 each have two round holes, the end plate away from the component has one round hole, and the upper surface of the end plate close to the component is flush with the lower surface of the integrated fixture 2.

[0049] It should be further pointed out that the integrated clamp 2 is composed of a U-shaped steel plate, an upper steel plate, a lower steel plate and ordinary bolts 6. The gap between the inside of the U-shaped steel plate and the upper and lower steel plates is 50~100mm, which facilitates the tightening of ordinary bolts 6.

[0050] It should be further pointed out that the integrated fixture has a chamfered interior on the U-shaped steel plate with a central round hole. The lower steel plate is integrally formed or welded with the U-shaped steel plate, and the upper steel plate is detachable. Its width is 5-20 mm lower than that of the lower steel plate. The upper and lower steel plates correspond to two rows of round holes, with 2-4 round holes in each row, reducing the risk of overall failure due to single-point failure.

[0051] It should be further pointed out that the roughening treatment of the contact surfaces of the upper and lower steel plates of the integrated fixture 2 can be wedge-shaped, wave-shaped, or toothed.

[0052] It should be further noted that the limiter 3 can be an angle steel or a channel steel, and the side plate connected to the fixed reaction frame has two round holes.

[0053] It should be further pointed out that the screw 4 is connected to the force sensor 5 through the thread, and the matching nut is connected to the outer side of the reaction frame 1 and the inner side of the U-shaped steel plate of the integrated clamp 2 through the hole respectively, which is a medium or rough assembly; the ordinary bolt 6 is connected to the reaction frame 1, the integrated clamp 2 and the limiter 3 through the hole, which is a medium or rough assembly.

[0054] It should be further pointed out that when the screw 4 and the ordinary bolt 6 are connected through the hole, a spring washer and a flat washer should be installed between the nut and the connected parts in sequence. When reused, the spring washer should be replaced in time.

[0055] It should be further noted that the screw 4 can be grade 8.8, 10.9 or 12.9, with a nominal diameter of 10~18 mm, and comes with 2 nuts; the ordinary bolt 6 can be grade 4.8, 5.6 or 8.8, with a nominal diameter of 12~18 mm.

[0056] It should be further noted that when the tension is 0~40 kN, the screw 4 should be grade 8.8 or 10.9 with a nominal diameter of 10~14 mm, and the ordinary bolt 6 should be grade 4.8 or 5.6 with a nominal diameter of 12~16 mm; when the tension is 40~100 kN, the screw 4 should be grade 10.9 or 12.9 with a nominal diameter of 14~18 mm, and the ordinary bolt 6 should be grade 5.6 or 8.8 with a nominal diameter of 16~18 mm.

[0057] It should be further noted that the force sensor 5 is an S-shaped tension and compression sensor with digital display or output signal function. It has a threaded hole at the top and bottom, a measurement range of 0~100 kN, and an accuracy class of C2 or C3.

[0058] It should be further pointed out that FRP7 is an FRP board or FRP cloth, and the length of the clamped section is the length of the upper and lower steel plates of the integrated clamp 2 along the FRP direction.

[0059] Therefore, considering the above structural design, the FRP prestressed tensioning device of this utility model has the advantages of simple assembly, low cost, and high reusability, and is suitable for various scaled model tests and construction sites with tension forces below 10 t.

[0060] like Figures 1 to 6As shown, a method for prestressing FRP for scaled-down model testing includes the following steps: (a) FRP fixing: FRP7 passes through the upper and lower steel plates of the integrated clamp 2, and the ordinary bolts 6 of the integrated clamp 2 are tightened; (b) Centering: The ordinary bolts 6 of the limiter 3 are tightened to ensure that the fixed reaction frame 1, integrated clamp 2, force sensor 5 and screw 4 are horizontally aligned; (c) Force sensor debugging: The force sensor 5 is connected to the data acquisition system, and the data acquisition parameters are set and adjusted; (d) Prestressing: The screw 4 is tensioned in stages by turning the nut of the screw 4 with a wrench or by driving the screw 4 with a through-hole jack, with the stress applied in stages, successively 25%, 50%, 75%, 100%, and 103% of the design tension stress. After stabilizing for 2-3 minutes, the force value change of the data acquisition system is observed to determine whether FRP7 has slipped. If slippage occurs, the FRP7 is slowly unloaded, the ordinary bolts 6 of the integrated clamp 2 are removed, and the operation is repeated according to steps (a) to (d); (e) FRP tensioning end fixing: Install FRP7 tensioning end anchorage, and operate symmetrically during the installation process. After installation, there should be no loosening or misalignment. (f) FRP holding and screw unloading: Hold FRP7 to the design requirements. During this period, observe the force value changes of the data acquisition system. After there are no abnormalities, slowly unload the nut in contact with the fixed reaction frame 1. If the nut is not easy to remove, the nut in contact with the integrated clamp 2 can be loosened. (g) Device removal and FRP treatment: Remove the limiter 3, screw 4, and force sensor 5 in sequence, loosen the ordinary bolts 6 of the integrated clamp 2, and cut off the excess FRP7.

[0061] Through the above-described process steps, this invention can effectively complete the prestressing tensioning of FRP, and the operation is simple, accurate and controllable.

[0062] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any modifications or equivalent changes made based on the technical essence of the present utility model shall still fall within the scope of protection claimed by the present utility model.

Claims

1. A FRP prestressed tensioning device for a scale model test, characterized by, The utility model relates to a kind of FRP tensioning devices, including fixed counterforce frame (1), integrated fixture (2), limiter (3), screw rod (4), force sensor (5) and ordinary bolt (6);The fixed counterforce frame (1) is arranged at the tensioning end of FRP (7), the integrated fixture (2) is fastened FRP (7) by ordinary bolt (6), the limiter (3) is fixed to the fixed counterforce frame (1) by ordinary bolt (6) on one side, and the other side contacts the upper surface of integrated fixture (2), the screw rod (4) one end passes through the middle of the U-shaped steel plate of integrated fixture (2) and is fixed by bolt, the screw rod (4) the other end passes through the outer end support of fixed counterforce frame (1) and is fixed by bolt, the force sensor (5) is between integrated fixture (2) and the outer end support of fixed counterforce frame (1), and the force sensor (5) is S-shaped and is passed by screw rod (4).

2. The FRP prestressed tensioning device for scale model test according to claim 1, characterized in that: The fixed counterforce frame (1) is composed of five steel plates, which are left and right side plates, front and rear end plates, and a bottom plate, wherein the left and right side plates each have two round holes, the end plate away from the component has one round hole, and the upper surface of the end plate close to the component is flush with the lower surface of the integrated fixture (2).

3. The FRP prestressed tensioning device for scale model test according to claim 1, characterized in that: The integrated fixture (2) is composed of a U-shaped steel plate, an upper steel plate, a lower steel plate, and ordinary bolts (6), wherein the U-shaped steel plate has an internal chamfer and a central round hole, the lower steel plate is integrally formed or welded with the U-shaped steel plate, the upper steel plate is detachable and has a width of 5-20 mm less than the lower steel plate, and the upper and lower steel plates correspond to two columns of round holes respectively, with 2-4 round holes in each column.

4. The FRP prestressed tensioning device for scale model test according to claim 3, characterized in that: The contact surface of the upper and lower steel plates of the integrated fixture (2) is roughened and has a wedge shape, a wave shape, or a tooth shape.

5. The FRP prestressed tensioning device for scale model test according to claim 1, characterized in that: The limiter (3) is an angle steel or a channel steel, and the side plate connected with the fixed counterforce frame has two round holes.

6. The FRP prestressed tensioning device for scale model test according to claim 1, characterized in that: The screw rod (4) is threadedly connected with the force sensor (5), and the matching nuts are respectively connected with the outer side of the fixed counterforce frame (1) and the inner side of the U-shaped steel plate of the integrated fixture (2) through holes, with medium assembly or rough assembly; the ordinary bolts (6) are connected with the fixed counterforce frame (1), the integrated fixture (2), and the limiter (3) through holes, with medium assembly or rough assembly.

7. The FRP prestressed tensioning device for scale model test according to claim 1, characterized in that: The force sensor (5) is an S-shaped tension and compression force sensor, has a digital display or output signal function, has a threaded hole at the top and the bottom respectively, has a measurement range of 0-100 kN, and has a precision level of C2 or C3.

8. The FRP prestressed tensioning device for scale model test according to claim 1, characterized in that: The FRP (7) is an FRP plate or an FRP cloth, and the clamped segment length is the length of the upper and lower steel plates of the integrated fixture (2) along the FRP direction.

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