Drop-weight impact test device for bridge FRP cables

Abstract

The present invention discloses a drop hammer impact test device for bridge FRP cables. The device uses a fully automated system to control the entire test process, making it convenient and efficient. Furthermore, the device can not only impact bridge FRP cables under various working conditions, such as different spans, pretensions, and inclination angles, but also conduct in-situ bending and tensile residual performance tests on the FRP cables after impact. This avoids the adverse effects of cable disassembly on the accuracy of the test results, facilitates researchers to understand the impact failure mechanism of FRP cables from multiple angles, and provides theoretical guidance for practical engineering industrial applications. The present invention solves the problem of the prior art in being unable to test the impact resistance of FRP cables under various combinations of spans, pretensions, and inclination angles.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, and in particular to a drop hammer impact test device for bridge FRP cables. Background Art

[0002] Parallel steel cables and stranded steel cables are the primary cable types used in cable-supported bridges. Their excellent mechanical properties have enabled the recent development of long-span, lightweight bridge structures. As the primary load-bearing component of cable-supported bridges, cable corrosion caused by various factors, including environmental factors, can have serious safety consequences for bridge structures.

[0003] Fiber reinforced polymer (FRP) offers advantages such as light weight, high strength, excellent durability, and fatigue resistance, making it a suitable alternative to traditional steel. Cables made from FRP are used in bridge structures, improving not only their durability but also their span and load-bearing capacity.

[0004] With the increasing number of motor vehicles in my country, the demand for transportation operations is also increasing. During actual operation, bridge cables are inevitably subject to impact loads such as vehicles. When the impact load exceeds the cable's own resistance, the cable is very likely to break, seriously causing the collapse of the bridge structure. FRP cables with orthotropic characteristics are more prone to this phenomenon under impact loads. Therefore, before engineering applications, it is necessary to conduct a large number of tests and theoretical analyses to explore the lateral stress performance and residual performance of bridge cables. Currently, there is no existing technology to test the impact resistance of FRP cables under different combinations of spans, pretensioning forces, and inclination angles.

[0005] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0006] In order to overcome the defects of the existing technology, a drop hammer impact test device for bridge FRP cables is now provided to solve the problem that the existing technology has not yet realized the impact resistance performance test of FRP cables under different span, pretension and inclination angle combinations.

[0007] To achieve the above-mentioned object, the present invention provides a drop weight impact test device for bridge FRP cables, comprising:

[0008] A base, wherein the base is provided with a top plate via a plurality of columns, and a guide rod is installed between the top plate and the base;

[0009] Two piers are arranged opposite to each other, the positions of the piers are adjustably mounted on the base, and the piers are reversibly mounted with support plates for installing cable anchors;

[0010] The hammer assembly includes a slider, a hammer body, and a lifting device. The slider is provided with a guide hole. The guide rod is movably inserted into the guide hole. The lifting device is connected to the slider via a chain. The slider is electromagnetically attracted to the hammer body. The hammer body is disposed between the two piers.

[0011] An anti-rebound member for electromagnetically adsorbing the hammer body, detachably mounted on the base and disposed below the hammer body, wherein the base is equipped with a distance sensor for collecting the distance value between the hammer body and the anti-rebound member;

[0012] A controller is connected to the lifting device, the distance sensor and the anti-rebound component.

[0013] Furthermore, ear plates are formed on opposite sides of the pier, and the ear plates are provided with two strip holes, at least one of the strip holes is arc-shaped, and the support plate is arranged between the two ear plates. Insert rods are formed on opposite sides of the support plate, and the insert rods can be movably passed through the strip holes and extended to the outside of the ear plates. The insert rods are installed with locking parts for locking the ear plates.

[0014] Furthermore, limiting plates are formed on opposite sides of the support plates on the two piers, and the limiting plates are provided with through holes for the FRP cables to pass through.

[0015] Furthermore, the slider and the anti-rebound component are respectively equipped with electromagnetic components.

[0016] Furthermore, a reinforcement beam is installed on the base, and the piers are adjustably installed at opposite ends of the reinforcement beam.

[0017] Furthermore, the reinforcement beam and the base are provided with through holes, the anti-rebound component is detachably mounted on the reinforcement beam to cover the through hole, the base is laid on the foundation, the foundation is provided with a receiving hole, the receiving hole is aligned with the through hole, and a loading head for testing the residual bending performance of the FRP cable is installed in a liftable manner in the receiving hole.

[0018] Furthermore, a platform is installed in the accommodating hole in a liftable manner, a loading jack is vertically arranged on the platform, and the loading head is installed on the loading jack.

[0019] Furthermore, a receiving frame for the FRP cable to pass through is installed on the top of the loading jack, and the loading head is installed on the upper part of the frame opening of the receiving frame.

[0020] The present invention provides a construction method of a drop hammer impact test device for bridge FRP cables, comprising the following steps:

[0021] Install both ends of the FRP cable to be tested on the supporting plates of the two piers through anchors;

[0022] Adjusting the positions of the two piers on the base and the flip angle of the support plate so that the FRP cable is arranged at a preset position on the base at a preset inclination angle;

[0023] The lifting device is turned on by the controller to suspend the hammer above the FRP cable to be tested;

[0024] The slider is powered off so that the hammer falls and impacts the FRP cable to be tested, and the distance sensor collects the distance value between the hammer and the anti-rebound component;

[0025] The controller activates the anti-rebound component based on the distance value, so that when the hammer approaches the base, it is electromagnetically attracted to the anti-rebound component to prevent the hammer from rebounding a second time.

[0026] The beneficial effects of the present invention lie in the fact that the drop-hammer impact test apparatus for bridge FRP cables employs a fully automated system to control the entire testing process, resulting in a convenient and efficient process. Furthermore, the apparatus not only allows impact testing of bridge cables under various operating conditions, such as varying spans, pretensions, and inclination angles, but also enables in-situ testing of the cables' residual bending and tensile properties after impact. This prevents the need for cable disassembly after impact, which could compromise the accuracy of test results. This allows researchers to understand the impact failure mechanisms of cables from multiple perspectives, providing theoretical guidance for practical engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0028] Figure 1 Schematic diagram of the structure of a drop hammer impact test device for bridge FRP cables according to an embodiment of the present invention.

[0029] Figure 2 Schematic diagram of the internal structure of a drop hammer impact test device for bridge FRP cables according to an embodiment of the present invention.

[0030] Figure 3 This is a front view of the internal structure of a drop weight impact test device for bridge FRP cables according to an embodiment of the present invention.

[0031] Figure 4 Schematic diagram of adjusting the inclination angle of the FRP cable according to an embodiment of the present invention.

[0032] Figure 5 Schematic diagram of the position adjustment of the FRP cable according to an embodiment of the present invention.

[0033] Figure 6 Schematic diagram of the loading head in use according to an embodiment of the present invention.

[0034] Figure 7 This is a schematic structural diagram of a first form of a loading head according to an embodiment of the present invention.

[0035] Figure 8 This is a schematic structural diagram of a second type of loading head according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0037] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] See Figures 1 to 8 As shown, the present invention provides a drop hammer impact test device for bridge FRP cables, comprising: a base 1, two piers 2, a hammer assembly, an anti-rebound component 4, and a controller.

[0039] In this embodiment, the base is a high-quality steel plate base. The base 1 is supported by a top plate 11 via a plurality of columns 12. A guide rod 13 is installed between the top plate 11 and the base 1. The top plate and the base are both rectangular. There are four columns. The four columns are arranged in a rectangular shape. The upper ends of the columns are connected to the top plate via flanges. The lower ends of the columns are connected to the base via flanges. The ends of the guide rods are threadedly connected to the threaded holes of the top plate and the base. After the guide rods are installed, the ends of the guide rods are in a tensioned state.

[0040] The two piers 2 are arranged opposite to each other. The two piers 2 are respectively mounted on the base 1 in an adjustable manner. The piers 2 are reversibly mounted with support plates 21. The support plates 21 are used to install the anchors of the cables 6.

[0041] As a preferred embodiment, a reinforcement beam 14 is installed on the base 1. The pier 2 is installed at the opposite ends of the reinforcement beam 14 in an adjustable manner.

[0042] In this embodiment, the reinforcement beam is a double T-shaped beam. The reinforcement beam is provided with a plurality of first positioning holes. The plurality of first positioning holes are spaced apart along the length of the reinforcement beam. The pier is provided with a plurality of second positioning holes. The second positioning holes are aligned with the first positioning holes and are connected by bolts.

[0043] See Figure 5 As shown, the position of the pier on the reinforced beam is adjusted by aligning the second positioning hole with the first positioning hole at different positions.

[0044] In a preferred embodiment, lug plates 22 are formed on opposite sides of the pier 2. Each lug plate 22 has two strip-shaped holes, at least one of which is arc-shaped. A support plate 21 is disposed between the two lug plates 22. Insertion rods 211 are formed on opposite sides of the support plate 21. The insertion rods 211 are movably inserted through the strip-shaped holes and extend to the outside of the lug plates 22. Locking members are mounted on the insertion rods 211 to lock the lug plates 22.

[0045] In this embodiment, one abutment's lug plate has a circular hole and a strip hole. The inner diameter of the circular hole matches the outer diameter of the rod, allowing the rod to rotate only within the circular hole. The inner arc of the strip hole in the abutment's lug plate faces the circular hole. Another abutment's lug plate has two arc-shaped holes. These three arc-shaped strip holes are all centered around the circular hole.

[0046] The angle value is marked next to the outermost strip hole, which is the longest strip hole. The strip hole closest to the center of the circle is the innermost strip hole, and the length of the strip holes gradually increases from the innermost strip hole to the outermost strip hole. Figure 4 As shown, the impact resistance test of the FRP cable at different tilt angles can be carried out by adjusting the flip angles of the two support plates.

[0047] As a preferred embodiment, limiting plates 212 are formed on opposite sides of the support plates 21 of the two piers 2. These limiting plates 212 have holes for the FRP cables 6 to pass through. Using these limiting plates, a pre-tensioning device can be used to apply pre-tension to the FRP cables or perform in-situ tensile residual performance testing.

[0048] The FRP cable is fixed to the support plate using anchors. Specifically, pre-tightening nuts, jacks, and force sensors are installed on both sides of the perforations in the limit plate. Pre-tensioning the cable is applied using the pre-tightening nuts or jacks, and the force is measured and recorded by the force sensors. Once these operations are complete, the cable's impact resistance can be tested under different pre-tensions. Furthermore, after the impact test, a secondary torque is applied to the pre-tightening nuts or a secondary tension is applied using a jack, allowing the FRP cable to be tested for residual tensile strength after impact.

[0049] The hammer assembly includes a slider 31, a hammer 32, and a lifting device 33. The slider 31 has a guide hole. The guide rod 13 is movably inserted into the guide hole. The lifting device 33 is connected to the slider 31 via a chain. The slider 31 is electromagnetically attracted to the hammer 32. The hammer 32 is located between the two piers 2.

[0050] The lifting device includes a motor. The motor is connected to the slider via a chain and sprocket. The slider is moved up and down by rotating the motor's output shaft in both forward and reverse directions.

[0051] The motor uses a brake motor, which will self-lock when the power is off or the equipment is turned off, and the hammer will not fall accidentally under the action of tension.

[0052] The hammer is lifted by a chain. Compared with high-strength steel wire ropes, the chain has less elasticity, which makes the height measurement more accurate. The chain also has higher strength and is less prone to wear.

[0053] The hammer body adopts a split design, consisting of a main hammer and a secondary hammer, connected by high-strength bolts. The secondary hammer body directly contacts the test piece, facilitating removal and replacement. The hammer body is machined from high-strength steel plate, offering excellent impact resistance and preventing breakage due to casting defects.

[0054] The anti-rebound member 4 is used to electromagnetically attract the hammer 32. The anti-rebound member 4 is detachably mounted on the base 1 and is disposed below the hammer 32. The base 1 is equipped with a distance sensor 7 for collecting the distance value between the hammer 32 and the anti-rebound member 4.

[0055] In this embodiment, the slider 31 and the anti-rebound member 4 are respectively equipped with electromagnetic members, which generate or eliminate magnetism by switching on and off current, thereby causing the hammer to fall and the anti-rebound member to absorb the fallen hammer.

[0056] The distance sensor uses an infrared sensor. When the impact energy is high, the cable breaks and the hammer continues to fall under gravity. When it approaches the base, the corresponding position signal is detected by the infrared sensor, and the electromagnetic component of the associated anti-rebound component is activated. The electromagnetic force clamps the hammer through the clamp and locks it, effectively preventing the hammer's rebound from causing secondary damage to the cable.

[0057] In a preferred embodiment, through-holes are provided in the reinforcement beam 14 and the base 1. The anti-rebound member 4 is removably mounted on the reinforcement beam 14 to conceal the through-holes. The base 1 is laid on the foundation. The foundation has a receiving hole, which is aligned with the through-hole. A loading head 5 for testing the residual bending resistance of the FRP cable 6 is movably mounted in the receiving hole.

[0058] The in-situ static load system includes a lifting jack, a platform, a force sensor, a loading jack and a loading head, etc., which are located in a limited area of ​​the foundation within a certain depth below the horizontal ground where the base is located. Figure 7 and Figure 8 A platform 51 is installed in the receiving hole in a movably movable manner. A loading jack 52 is vertically installed on the platform 51, and the loading head 5 is installed on the loading jack 52. Specifically, a plurality of jacking jacks are vertically installed in the receiving hole. The platform 51 is installed on the plurality of jacking jacks. The force sensor is padded between the platform 51 and the loading jack 52.

[0059] In this embodiment, there are two types of loading heads, such as Figure 7 As shown, the loading head is a downward pressing type loading head; Figure 8 As shown, the loading head is a top-up type loading head.

[0060] Continue reading Figure 6 and Figure 7 The top of the loading jack is provided with a receiving frame 53 for passing the FRP cable 6. The downward pressure loading head 5 is installed on the upper part of the frame opening of the receiving frame.

[0061] During the FRP cable impact test, if the impact energy is low and the FRP cable does not fail or fracture, after the impact, the motor is started to raise the hammer to the position where the hammer catch and release device was originally fixed, and the anti-rebound component located at the top of the reinforced beam is removed. The in-situ static load system's loading jack and platform height can then be adjusted by operating the lifting jack, allowing the loading head to extend above the reinforced beam. When conducting the FRP cable impact resistance test, the loading head is lowered below the horizontal ground level of the base, and the anti-rebound component is then installed on the reinforced beam to cover the through-hole of the reinforced beam. The two types of tests do not affect each other.

[0062] In the in-situ static loading system, the upper push-up and lower pressure loading heads can test the bending residual performance of the cable loading at the back impact side and the impacted side respectively, and the relevant mechanical parameter indicators are derived and recorded by the force sensor.

[0063] In this embodiment, the controller is connected to the lifting device 33, the distance sensor 7, and the anti-rebound member 4. The controller is designed using a PLC programmable controller, with an electronic touch screen for direct user operation and a rotary encoder to measure and control the drop hammer height, making the hammer catching, lifting, zeroing, and impacting a fully automated process.

[0064] Continue reading Figure 1The drop-weight impact test apparatus for bridge FRP cables of the present invention also includes a protective structure. This protective structure includes enclosed electromagnetic protective doors surrounding the impact tester. These doors can be opened in four directions, facilitating the feeding of test specimens and the installation and removal of related equipment components. The protective doors are equipped with a sensing device. When the protective door is open, the drop-weight impact test apparatus for bridge FRP cables of the present invention self-locks via a controller, rendering the corresponding equipment inoperable and ensuring the safety of test personnel.

[0065] After installing the cable specimen, before the actual test begins, closing the protective door effectively prevents any dangerous splashing from the broken specimen during the test. The protective door is equipped with a sensor, and if it is not fully closed, the tester will self-lock, and a warning light will begin flashing. Once the test begins, the drop hammer start light illuminates, and the slider releases the hammer, impacting the FRP cable specimen. During the impact, the impact force applied to the sensor mounted on the cable specimen and the specimen's deformation are transmitted to a computer via the appropriate equipment, generating the required indicators, such as the impact force-time curve and the impact force-displacement curve.

[0066] By keeping the length of the FRP cable specimen to be tested unchanged and moving the position of the pier again, the impact resistance test of the cable can be achieved when the hammer is at different impact positions.

[0067] In this embodiment, the cable specimens to be tested can be FRP rod type cables, FRP stranded wire type cables and FRP sheet type cables, and the corresponding anchor types can be adhesive anchors, clip anchors and mechanical clamping anchors.

[0068] The present invention provides a construction method of a drop hammer impact test device for bridge FRP cables, comprising the following steps:

[0069] S1: Install both ends of the FRP cable 6 to be tested on the supporting plates 21 of the two piers 2 through anchors respectively.

[0070] S2: Adjust the positions of the two piers 2 on the base 1 and the flip angle of the support plate 21 so that the FRP cables 6 are arranged at a preset position on the base 1 at a preset tilt angle.

[0071] S3: The controller turns on the lifting device 33 to suspend the hammer 32 above the FRP cable 6 to be tested.

[0072] S4 : The slider 31 is powered off to make the hammer 32 fall and impact the FRP cable 6 to be tested. The distance sensor 7 collects the distance value between the hammer 32 and the anti-rebound component 4 .

[0073] S5: The controller activates the anti-rebound component 4 based on the distance value, so that when the hammer 32 approaches the base 1 , it is electromagnetically attracted to the anti-rebound component 4 to prevent the hammer 32 from rebounding a second time.

[0074] During actual operation, the FRP cable under test may encounter relatively low impact energy. In this case, visible damage may appear on the cable's surface, but the cable may not completely break. Alternatively, invisible damage may occur within the cable. While the cable can continue to bear load in these situations, the cable's residual performance after the impact must be tested. Since the hammer has not fallen onto the base, the hammer must be raised to its original position after the impact test, and then the anti-rebound component on the reinforced beam must be removed.

[0075] The in-situ static load device is located on the ground of the receiving hole at a certain depth below the horizontal ground where the base is located. The platform is lifted by a lifting jack so that the loading head extends above the reinforced beam to perform bending residual performance testing.

[0076] The residual bending properties of the FRP cable after impact obtained by loading on the impact side and the back impact side are different. Figure 7 The loading head can exert a downward force on the impacted FRP cable at the impacted side until it completely breaks and fails. Figure 8 The loading head shown can apply a vertical upward force to the FRP cable at the back impact side after impact to test the bending residual performance. The relevant data is transmitted to the computer through the force sensor for recording.

[0077] The residual tensile strength of the FRP cable after impact is also crucial for evaluating its mechanical properties. By applying a secondary torque to the preload nut or using a jack to tension the FRP cable until failure, the changes in the residual tensile strength of the cable after impact can be recorded to assess its mechanical properties.

[0078] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A drop weight impact test device for bridge FRP cables, characterized in that: include: A base, wherein the base is provided with a top plate via a plurality of columns, and a guide rod is installed between the top plate and the base; Two piers are arranged opposite to each other, the positions of the piers are adjustably mounted on the base, and the piers are reversibly mounted with support plates for installing cable anchors; The hammer assembly includes a slider, a hammer body, and a lifting device. The slider is provided with a guide hole. The guide rod is movably inserted into the guide hole. The lifting device is connected to the slider via a chain. The slider is electromagnetically attracted to the hammer body. The hammer body is disposed between the two piers. An anti-rebound member for electromagnetically adsorbing the hammer body is detachably mounted on the base and disposed below the hammer body, wherein the base is equipped with a distance sensor for collecting the distance value between the hammer body and the anti-rebound member; a controller connected to the lifting device, the distance sensor, and the anti-rebound component; The pier is formed with ear plates on opposite sides, each of which is provided with two strip-shaped holes, at least one of which is arc-shaped. The support plate is arranged between the two ear plates, and each of which is provided with an insertion rod on opposite sides. The insertion rod can be movably passed through the strip-shaped holes and extended to the outside of the ear plates. The insertion rod is installed with a locking piece for locking the ear plates. Limiting plates are formed on opposite sides of the supporting plates of the two piers, and the limiting plates are provided with through holes for the FRP cables to pass through; The base is formed with a reinforcement beam, and the piers are adjustably mounted at opposite ends of the reinforcement beam; The reinforcement beam and the base are provided with through holes, the anti-rebound member is detachably mounted on the reinforcement beam to cover the through holes, the base is laid on a foundation, the foundation is provided with a receiving hole, the receiving hole is aligned with the through hole, and a loading head for testing the bending residual performance of the FRP cable is movably mounted in the receiving hole; A platform is installed in the receiving hole in a liftable manner, a loading jack is vertically arranged on the platform, and the loading head is installed on the loading jack; A receiving frame for the FRP cable to pass through is installed on the top of the loading jack, and the loading head is installed on the upper part of the frame opening of the receiving frame.

2. The drop weight impact test device for bridge FRP cables according to claim 1, characterized in that: The slider and the anti-rebound component are respectively equipped with electromagnetic components.

3. A construction method for a drop weight impact test device for bridge FRP cables according to any one of claims 1 to 2, characterized in that: The following steps are involved: Install both ends of the FRP cable to be tested on the supporting plates of the two piers through anchors; Adjusting the positions of the two piers on the base and the flip angle of the support plate so that the FRP cable is arranged at a preset position on the base at a preset inclination angle; The lifting device is turned on by the controller to suspend the hammer above the FRP cable to be tested; The slider is powered off to cause the hammer to fall and impact the FRP cable to be tested, and a distance sensor collects the distance value between the hammer and the anti-rebound component; The controller activates the anti-rebound component based on the distance value, so that when the hammer approaches the base, it is electromagnetically attracted to the anti-rebound component to prevent the hammer from rebounding a second time.

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