Concrete reinforcement bond stress test device

Abstract

The invention discloses a concrete reinforcement bond stress test device which is characterized in that a first sensor is connected to a second tension applying mechanism, and the second tension applying mechanism is detachable and is designed to be separated from the function, so that the problem that a traditional concrete reinforcement bond stress test device cannot be used for testing the bond stress in a long-term test is fundamentally solved; the problem of data drift caused by continuous working of the force sensor is solved, so that high-precision, long-term and stable bond stress monitoring is realized.

Description

Technical Field

[0001] This disclosure generally relates to the technical field of grip strength testing devices, and specifically to a device for testing the grip strength of concrete reinforcement bars. Background Technology

[0002] Bond strength is a physical quantity that measures the ability of concrete to resist the slippage of reinforcing bars. Generally, bond strength refers to the shear stress along the contact surface between the reinforcing bars and the concrete, which is also known as bond stress.

[0003] In related technologies, the force sensor of the concrete rebar bond force testing device generally suffers from significant data drift error in ultra-long cycle tests, resulting in inaccurate test data. Summary of the Invention

[0004] In a first aspect, this application provides a concrete reinforcement bond strength testing device, comprising: The first centering clamp engages with the loading end of the specimen, wherein the specimen includes a concrete matrix and reinforcing bars passing through the concrete matrix, and the reinforcing bars include a free end and the loading end; The second centering clamp is engaged with the concrete matrix for traction. The second centering clamp includes a slender force transmission member whose length extension direction is parallel to the length direction of the reinforcing bar. The first tension application mechanism is used to apply a first tension to the force transmission member in an increasing or decreasing manner, so that the forces applied to the specimen by the second centering clamp and the first centering clamp are equal in magnitude and opposite in direction; The second tension applying mechanism is movable and has an installation position and a disassembly position. In the installation position, the second tension applying mechanism is used to apply a second tension to the force transmission member in an increasing or decreasing manner, such that the forces applied to the specimen by the second centering clamp and the first centering clamp are equal in magnitude and opposite in direction. In the disassembly position, the device includes the first and second centering clamps and the first tension applying mechanism to form a monitoring device. A first sensor is used to acquire the axial force applied to the specimen, and the first sensor is mounted on the second tension application mechanism; In S1, the second tension applying mechanism is in the loading position, and the second tension applying mechanism applies the second tension to the force transmission component incrementally until the first sensor acquires the first load value F1; S2. The second tension applying mechanism is in the loading position. The second tension applying mechanism applies the second tension to the force transmission component in a decreasing manner until the first sensor obtains a preset load value F4, 0N < F4 < 1N. Simultaneously, the first tension applying mechanism applies the first tension to the force transmission component in a increasing manner. S3. The second tension application mechanism is switched from the installation position to the disassembly position, the device is switched to the monitoring device, and the monitoring device is transferred to the test environment and placed for a preset time; S4. The monitoring device is removed from the test environment, the second tension application mechanism is switched from the disassembly position to the installation position, the monitoring device is switched to the device, the second tension application mechanism is in the loading position, the first tension application mechanism applies the first tension to the force transmission component in a decreasing manner until zero, and at the current moment the first sensor obtains the second load value F2, F2 < F1.

[0005] In one embodiment, the first tension application mechanism includes a spring and a pressure plate disposed at one end of the spring, and the force transmission member passes through the spring and the pressure plate. The force transmission component includes a first threaded section, and a nut A is connected to the first threaded section to press the spring. The compression of the spring is adjusted by the nut A to apply the first tension to the force transmission component in an increasing or decreasing manner.

[0006] In one embodiment, a support frame is further included, comprising a first beam and a second beam disposed opposite to each other, wherein a first centering clamp and a second centering clamp are located between the first beam and the second beam, the first centering clamp being disposed closer to the first beam and the second centering clamp being disposed closer to the second beam. The second centering clamp and the spring are located on both sides of the second beam, the force transmission member passes through the second beam, and the other end of the spring is pressed onto the second beam.

[0007] In one embodiment, the support frame further includes a third beam and a fourth beam disposed opposite to each other, wherein the first beam, the third beam, the second beam, and the fourth beam are connected end to end to form a rectangular frame. The first centering clamp includes a first fixing part and a first hinge part. The first fixing part is installed on the first beam body, and the first hinge part can clamp the loading end. The first hinge part is hinged to the first fixing part so that the first centering clamp can adjust the extension direction of the steel bar. The second centering clamp includes the force transmission component, the connecting rod, and a first centering component, a second centering component, and a traction assembly arranged sequentially from the second beam to the first beam. The traction assembly includes a first traction plate and a second traction plate arranged opposite to each other, and a plurality of screws. The screws pass through the first traction plate and the second traction plate, and the plurality of screws are arranged around the edges of the first traction plate and the second traction plate. Each screw is provided with a plurality of locking nuts to provide space between the first traction plate and the second traction plate for accommodating the concrete substrate and the free end. The concrete substrate is in contact with one of the first traction plate and the second traction plate, so that the traction assembly can engage with the concrete substrate in a traction manner. The length direction of the connecting rod is the same as or parallel to the length direction of the force transmission member. One end of the connecting rod is connected to the other of the first traction plate and the second traction plate, and passes through the second centering member until it reaches the first centering member. The first centering member has the same structure as the first centering clamp, including a second fixing part and a second hinge part. The second hinge part can clamp the other end of the connecting rod. One end of the force transmission member is connected to the second fixing part, and the other end of the force transmission member passes through the second beam, the spring and the pressure plate in sequence. Under the action of the first centering clamp, the first centering member, and the second centering member, the length extension direction of the force transmission member is the same as the length extension direction of the reinforcing bar.

[0008] In one embodiment, the second tension application mechanism includes a connecting frame that is fitted into the second beam.

[0009] In one embodiment, the second tension applying mechanism further includes a force-applying element, and the connecting frame includes a fifth beam. The force-applying component and the first sensor are located on one side of the second beam, the spring is located on the other side of the second beam, the force-transmitting component passes through the fifth beam, the first sensor and the force-applying component are mounted on the force-transmitting component, and the first sensor is sandwiched between the fifth beam and the force-applying component. In this process, the spring switches from its self-compression state to its initial state, and a safe distance exists between the pressure plate and the fifth beam.

[0010] In one embodiment, the force-applying component includes a jack or a fastening nut threadedly connected to the force-transmitting component.

[0011] In one embodiment, the force-applying component is the jack. The force transmission component also includes a second threaded section, with another nut B connected to the second threaded section, ensuring seamless contact between the connecting frame and the second beam, seamless contact between the first sensor and the fifth beam, and seamless contact between the first sensor and the jack. The jack is a hollow jack, the first sensor is a hollow pressure sensor, and the force transmission component passes through the hollow area of ​​the hollow jack and the hollow area of ​​the hollow pressure sensor.

[0012] In one embodiment, the orthographic projection of the hollow pressure sensor onto the fifth beam is completely located on the fifth beam, and the radial dimension of the hollow pressure sensor is smaller than the radial dimension of the hollow jack body.

[0013] In one embodiment, the connecting frame further includes a sixth beam and a seventh beam located on both sides of the fifth beam, the sixth beam, the seventh beam and the fifth beam forming a U-shape; A stop portion is formed on the second beam body with opposite sides protruding, and a slot is formed between the two stop portions. One slot is inserted into the free end of the sixth beam body, and the other slot is inserted into the free end of the seventh beam body, so as to realize the insertion and engagement of the connecting frame and the second beam body. At the current moment, the connecting frame and the support frame are arranged vertically. When the connecting frame and the second beam are engaged, the second tension application mechanism is positioned in the installation position; when the connecting frame and the second beam are disengaged, the second tension application mechanism is positioned in the disassembly position. The free ends of the sixth and seventh beams are in planar contact with the second beam.

[0014] Secondly, a method for testing the bond strength of reinforced concrete includes: S1. The second tension applying mechanism is in the loading position. The second tension applying mechanism applies the second tension to the force transmission member incrementally until the first sensor acquires the first load value F1. S2. The second tension applying mechanism is in the loading position. The second tension applying mechanism applies the second tension to the force transmission component in a decreasing manner until the first sensor obtains a preset load value F4, 0N < F4 < 1N. Simultaneously, the first tension applying mechanism applies the first tension to the force transmission component in a increasing manner. S3. The second tension application mechanism is switched from the installation position to the disassembly position, and the device is switched to the monitoring device; and the monitoring device is transferred to the test environment and placed for a preset time; S4. The monitoring device is removed from the test environment, the second tension application mechanism is switched from the disassembly position to the installation position, the monitoring device is switched to the device, the second tension application mechanism is in the loading position, the first tension application mechanism applies the first tension to the force transmission component in a decreasing manner until zero, and at the current moment the first sensor obtains the second load value F2, F2 < F1.

[0015] In one embodiment, the difference between the first load value F1 and the second load value F2 includes a measurement error value F3. The specimen is replaced with a steel plate with a thickness of 2 mm or more. One end of the steel plate is engaged with the first centering clamp and the other end is engaged with the second centering clamp. S1-S4 are repeated. The first centering clamp, the second centering clamp and the steel plate are relatively stationary. The first load value F1′ is obtained in S1 and the second load value F2′ is obtained in S4. The difference between F1′ and F2′ is the measurement error value F3.

[0016] In one embodiment, it further includes: S5. Verify whether the test can be repeated. If (F1-(F2+F3)) / F1≤5%, the test is qualified. If (F1-(F2+F3)) / F1>5%, then repeat S1-S4.

[0017] In one embodiment, it further includes: S5. Verify whether the experiment can be repeated. If ((F1-F t If (F1)% ≤ 5%, then the test is qualified; if (F1 - F t If ) / F1)%>5%, then repeat S1-S4. The specimen is provided with multiple second sensors on the concrete matrix, which are used to acquire the interface slip between the reinforcing bar and the concrete matrix; the specimen is provided with multiple third sensors on the reinforcing bar, which are used to acquire the true axial strain of the reinforcing bar itself; the second sensors are dial indicator clamps; the third sensors include grating sensors. (1) ; (2) The cross-section of the reinforcing bar is rectangular. The width of the reinforcing bar; The thickness of the reinforcing steel; This is the axial elastic modulus of the reinforcing steel. is the axial temperature expansion coefficient of the reinforcing steel. The temperature change of the first temperature of the monitoring device under S3 relative to the second temperature of the device under S1; (3) (4) in, The average value of data measured by multiple grating sensors; The strain transfer efficiency from the grating sensor to the reinforcing bar is 0 < β ≤ 1; The pasting length is 0.5 times the original length. It is the coefficient of thermal expansion of the grating; is the axial temperature expansion coefficient of the reinforcing steel. (5) in, It is the radius of the grating sensor with a protective layer; It is the radius of the grating without a protective layer; It is the elastic modulus of the grating; It is the thickness of the grating adhesive layer; The elastic modulus of the grating adhesive layer; It is the integral angle along the circumference.

[0018] In one embodiment, when ((F1-F t When ) / F1)%>5%, Verify that F4 is correct by (Ft-(F2+F3)) / Ft>5%; or verify that S4 is correct by (F1-(F2+F3)) / F1>5%.

[0019] In the above solution, this application connects the first sensor to the second tension application mechanism, and the second tension application mechanism is designed to be detachable and functionally separate. This fundamentally solves the problem of data drift caused by the continuous operation of the force sensor in the long-term (ultra-long-cycle) test of the traditional concrete rebar bond force test device, thereby achieving high-precision and long-term stable bond force monitoring. Attached Figure Description Figure 1 A schematic diagram of the concrete rebar bond strength testing device provided in this embodiment of the invention. Figure 1 ; Figure 2 A schematic diagram of the concrete rebar bond strength testing device provided in this embodiment of the invention. Figure 2 ; Figure 3 This is a schematic diagram of the structure of the first centering fixture and the second centering fixture provided in an embodiment of the present invention; Figure 4 This is a partial structural schematic diagram of the specimen provided in an embodiment of the present invention; Figure 5 A schematic diagram of the cross-section of a grating sensor provided in an embodiment of the present invention. Figure 1; Figure 6 A schematic diagram of the cross-section of a grating sensor provided in an embodiment of the present invention. Figure 2 ; Support frame 10, first beam 11, second beam 12, third beam 13, fourth beam 14; Second tension application mechanism 20, force application component 21, connecting frame 22, fifth beam 221, sixth beam 222, seventh beam 223; First centering clamp 31, first fixing part 311, first hinge part 312, second centering clamp 32, first centering component 321, second centering component 322, second hinge part 3211, second fixing part 3212, traction assembly 323, first traction plate 3231, second traction plate 3232, screw 3233, connecting rod 324, force transmission component 325; First tension application mechanism 40, spring 41, pressure plate 42; First sensor 50, second sensor 60, third sensor 70; Specimen 80, reinforcing bar 81, loading end 811, free end 812, concrete matrix 82. Detailed Implementation

[0020] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] like Figures 1-6 As shown, a concrete rebar bond strength testing device includes: a first centering clamp 31, a second centering clamp 32, a first tension application mechanism 40, a second tension application mechanism 20, and a first sensor 50. The specimen 80 includes a concrete matrix 82 and a rebar 81 passing through the concrete matrix 82. The rebar 81 includes a free end 812 and a loaded end 811.

[0023] The first centering clamp 31 is engaged with the loading end 811 for traction; the second centering clamp 32 is engaged with the concrete matrix 82 for traction. The second centering clamp 32 includes a slender force transmission member 325, the length extension direction of which is parallel to the length direction of the reinforcing bar 81.

[0024] The first tensile force applying mechanism 40 is used to apply the first tensile force to the force transmission member 325 incrementally or decrementally, so that the acting forces exerted on the test piece 80 by the second centering fixture 32 and the first centering fixture 31 are equal in magnitude and opposite in direction.

[0025] The second tensile force applying mechanism 20 is movable and has an installation position and a disassembly position. When the second tensile force applying mechanism 20 is in the installation position, it is used to apply the second tensile force to the force transmission member 325 incrementally or decrementally, so that the acting forces exerted on the test piece 80 by the second centering fixture 32 and the first centering fixture 31 are equal in magnitude and opposite in direction; when the second tensile force applying mechanism 20 is in the disassembly position, the device includes the first and second centering fixtures and the first tensile force applying mechanism 40 to form a monitoring device.

[0026] The first sensor 50 is used to obtain the axial force applied to the test piece 80, and the first sensor 50 is installed on the second tensile force applying mechanism 20. The first sensor 50 is a pressure sensor.

[0027] The test piece 80 is tested by the device, including the following steps: S1. The second tensile force applying mechanism 20 is in the installation position, and the second tensile force applying mechanism 20 applies the second tensile force to the force transmission member 325 incrementally until the first sensor 50 obtains the first load value F1. S2. The second tensile force applying mechanism 20 is in the installation position, and the second tensile force applying mechanism 20 applies the second tensile force to the force transmission member 325 decrementally until the first sensor 50 obtains the preset load value F4, where 0 N < F4 < 1 N. Synchronously, the first tensile force applying mechanism 40 applies the first tensile force to the force transmission member 325 incrementally. S3. The second tensile force applying mechanism 20 is switched from the installation position to the disassembly position, and the device is switched to a monitoring device. Then the monitoring device is transported to the test environment and placed for a preset time. S4. The monitoring device is removed from the test environment, the second tensile force applying mechanism 20 is switched from the disassembly position to the installation position, the monitoring device is switched back to the device, the second tensile force applying mechanism 20 is in the installation position, and the first tensile force applying mechanism 40 applies the first tensile force to the force transmission member 325 decrementally until zero. At the current moment, the first sensor 50 obtains the second load value F2, where F2 < F1.

[0028] In step S1, the second tension application mechanism 20 is in the installed position and applies the second tension incrementally. The first sensor 50 obtains F1 in real time, and at this time, the data of the first sensor 50 has no drift error. In step S2, the second tension application mechanism 20 synchronously decreases the second tension, and the first tension application mechanism 40 synchronously increases the first tension, so that the resultant force on the specimen 80 is constant, and the load is smoothly transferred to the first tension application mechanism 40. When the reading of the first sensor 50 drops to F4, it has been basically unloaded. Considering that it is inconvenient to obtain the 0 value of the first pressure sensor in practical applications, the reading of the first sensor 50 is chosen to drop to F4, 0N. <F4<1N, thus eliminating the influence on the F1 benchmark; in S3, the second tension application mechanism 20 is completely disassembled, and the first sensor 50 is moved out of the test environment with the mechanism, completely avoiding any influence caused by temperature, humidity, or corrosive media. The first tension application mechanism 40 maintains a constant tension in a purely mechanical manner, and its creep and relaxation are negligible within the preset monitoring time; in S4, the second tension application mechanism 20 is reinstalled, and the first tension application mechanism 40 is gradually unloaded, with the entire load once again borne by the second tension application mechanism 20, and the first sensor 50 acquires F2. Because the first sensor 50 only operates under the two short, controllable, and environmentally friendly conditions of S1 and S4, its two readings F1 and F2 have equally high accuracy, and the difference (F1−F2) truly characterizes the amount of bond force loss at the concrete-reinforcement interface 81 in long-term testing, thereby solving the data distortion problem caused by long-term sensor service in the background technology, and significantly improving the reliability and repeatability of long-term bond force testing.

[0029] Therefore, the first sensor 50 is connected to the second tension application mechanism 20, and the second tension application mechanism 20 is designed to be detachable and functionally separate, which fundamentally solves the problem of data drift caused by the continuous operation of the force sensor in the long-term (ultra-long-cycle) test of the traditional concrete rebar bond force test device, thereby achieving high-precision and long-term stable bond force monitoring.

[0030] The following is a detailed description of the test device for the bond strength of concrete reinforcement: like Figures 1-3 As shown, the device also includes a support frame 10. The support frame 10 includes a first beam 11 and a second beam 12 arranged opposite to each other, and a third beam 13 and a fourth beam 14 arranged opposite to each other. The first beam 11, the third beam 13, the second beam 12 and the fourth beam 14 are connected end to end to form a rectangular frame.

[0031] The first centering clamp 31 and the second centering clamp 32 are located between the first beam 11 and the second beam 12. The first centering clamp 31 is set closer to the first beam 11, and the second centering clamp 32 is set closer to the second beam 12.

[0032] The first centering clamp 31 includes a first fixing part 311 and a first hinge part 312. The first fixing part 311 is mounted on the first beam 11, and the first hinge part 312 is capable of clamping the loading end 811. The first hinge part 312 is hinged to the first fixing part 311 so that the first centering clamp 31 can adjust the length extension direction of the reinforcing bar 81. Figure 3 As shown, the first centering clamp 31 adjusts the loading end 811 of the reinforcing bar 81 in the front-back direction, thereby adjusting the position of the entire specimen 80 in the front-back direction.

[0033] like Figure 3 As shown, the second centering clamp 32 includes a force transmission element 325, a connecting rod 324, and a first centering element 321, a second centering element 322, and a traction assembly 323 arranged sequentially from the second beam 12 to the first beam 11. The traction assembly 323 includes a first traction plate 3231 and a second traction plate 3232 arranged opposite each other, and a plurality of screws 3233 passing through the first traction plate 3231 and the second traction plate 3232. The plurality of screws 3233 are arranged around the edges of the first traction plate 3231 and the second traction plate 3232, and each screw 3233 is equipped with a plurality of locking nuts to provide space between the first traction plate 3231 and the second traction plate 3232 for accommodating the concrete substrate 82 and the free end 812. This space can properly accommodate the concrete substrate 82, and the surrounding screws 3233 will not contact the concrete substrate 82, thereby avoiding load loss due to local crushing or slippage during loading, which could affect the test results. The concrete substrate 82 comes into contact with one of the first traction plate 3231 and the second traction plate 3232, so that the traction component 323 and the concrete substrate 82 can be tractionally engaged.

[0034] The length direction of the connecting rod 324 is the same as or parallel to the length direction of the force transmission member 325. One end of the connecting rod 324 is connected to the other of the first traction plate 3231 and the second traction plate 3232, and passes through the second centering member 322 until it reaches the first centering member 321. The first centering member 321 has the same structure as the first centering clamp 31. The first centering member 321 includes a second fixing part 3212 and a second hinge part 3211. The second hinge part 3211 can hold the other end of the connecting rod 324, and one end of the force transmission member 325 is connected to the second fixing part 3212. Figure 3 As shown, the first centering member 321 adjusts the position of the entire specimen 80 in the front-back direction by adjusting the free end 812 of the reinforcing bar 81. The second centering member 322 has the same function as the first centering member 321, so it will not be described again.

[0035] Under the action of the first centering clamp 31, the first centering piece 321, and the second centering piece 322, the length extension direction of the force transmission piece 325 is the same as the length extension direction of the reinforcing bar 81, that is, the axis of the force transmission piece 325 coincides with the axis of the reinforcing bar 81.

[0036] The rectangular support frame 10 provides a high-rigidity load-bearing foundation. The first centering clamp 31 and the first centering member 321 form symmetrical hinged ends, constraining the coaxial boundary conditions of the reinforcing bar 81 and the force transmission member 325; the traction assembly 323 achieves slip-free clamping of the concrete matrix 82 through the ring bolt 3233 and the multi-locking nut structure, eliminating measurement noise introduced by interface loosening; the connecting rod 324, as an intermediate flexible force transmission element, smoothly introduces the traction force; the isomorphic design of the first and second centering members and the first centering clamp 31 ensures that the axis of the force transmission member 325 coincides with the axis of the reinforcing bar 81.

[0037] The first tension application mechanism 40 includes a spring 41 and a pressure plate 42 disposed at one end of the spring 41. A force transmission component 325 passes through the spring 41 and the pressure plate 42. The force transmission component 325 includes a first threaded section, to which a nut A is connected to press-fit the spring 41. The compression of the spring 41 is adjusted by the nut A to apply a first tension force to the force transmission component 325 incrementally or incrementally. Because the spring 41 has definite linear stiffness characteristics and low creep performance, and the pressure plate 42 ensures the uniformity and coaxiality of force transmission, the first threaded section of the force transmission component 325 and the nut A form a high-precision displacement-force conversion pair, which can smoothly bear the load removed by the second tension application mechanism 20 in S2 and controllably release all preload in S4.

[0038] In addition, such as Figure 2 As shown, the second centering clamp 32 and the spring 41 are located on both sides of the second beam 12. The other end of the spring 41 is pressed onto the second beam 12; the other end of the force transmission member 325 passes through the second beam 12, the spring 41 and the pressure plate 42 in sequence.

[0039] The second tension application mechanism 20 includes a connecting frame 22, which is fitted into the second beam 12.

[0040] like Figure 1 As shown, the second tension application mechanism 20 includes a force-applying component 21 and a connecting frame 22. The connecting frame 22 includes a fifth beam 221 and a sixth beam 222 and a seventh beam 223 located on both sides of the fifth beam 221. The sixth beam 222, the seventh beam 223 and the fifth beam 221 form a U-shape.

[0041] A protrusion forming opposing stops on the second beam 12, with a slot between the two stops. One slot engages with the free end 812 of the sixth beam 222, and the other slot engages with the free end 812 of the seventh beam 223, thus achieving the engagement of the connecting frame 22 and the second beam 12. Currently, the connecting frame 22 and the support frame 10 are positioned vertically. When the connecting frame 22 and the second beam 12 are engaged, the second tension application mechanism 20 is in the installed position; when the connecting frame 22 and the second beam 12 are disengaged, the second tension application mechanism 20 is in the disassembled position. The free ends 812 of the sixth beam 222 and the seventh beam 223 are in planar contact with the second beam 12.

[0042] The connection frame 22 and the second beam 12 are constrained by contact with the plane through the slot, which avoids the problem of slight overturning, local warping and reference surface drift of the connection frame 22 under large load, so that the measurement reference of the first sensor 50 always remains stable.

[0043] In addition, such as Figure 1 , 2 As shown, the force-applying component 21 and the first sensor 50 are located on one side of the second beam 12, and the spring 41 is located on the other side of the second beam 12. The force-transmitting component 325 passes through the fifth beam 221, and the first sensor 50 and the force-applying component 21 are installed on the force-transmitting component 325. The first sensor 50 is sandwiched between the fifth beam 221 and the force-applying component 21. The spring 41 switches from its compressed state to its initial state, and a safe distance exists between the pressure plate 42 and the fifth beam 221.

[0044] In step S4, when the spring 41 of the first tension application mechanism 40 fully recovers from the compressed state to the initial state, the pressure plate 42 will not come into contact with the fifth beam 221, thereby avoiding distortion of the reading of the first sensor 50 due to mechanical impact. At the same time, the rigid clamping of the fifth beam 221 and the force application member 21 on the first sensor 50 ensures that it is under the same mechanical boundary conditions in both the loading stage of S1 and the final reading stage of S4, which significantly suppresses the influence of installation stress release, thermal expansion and contraction drift and micro-vibration interference on the reading of the first sensor 50.

[0045] It should be noted that the force-applying component 21 includes a jack or a fastening nut threadedly connected to the force-transmitting component 325. Preferably, the force-applying component 21 is the jack.

[0046] The force transmission member 325 further includes a second threaded section, and another nut B is connected to the second threaded section, so that the connecting frame 22 is in seamless contact with the second beam body 12, the first sensor 50 is in seamless contact with the fifth beam body 221, and the first sensor 50 is in seamless contact with the jack. Among them, the jack is a hollow jack, the first sensor 50 is a pressure hollow sensor, and the force transmission member 325 passes through the hollow area of the hollow jack and the hollow area of the pressure hollow sensor.

[0047] With such a setting, an axial force transmission chain with high stiffness, zero clearance, and full coaxiality can be constructed, thus avoiding measurement distortion caused by assembly eccentricity and interface clearance.

[0048] Furthermore, the orthographic projection of the hollow pressure sensor on the fifth beam body 221 is completely located on the fifth beam body 221, and the radial dimension of the hollow pressure sensor is smaller than the radial dimension of the body of the hollow jack.

[0049] Since the orthographic projection of the hollow pressure sensor on the fifth beam body 221 is completely within the range of the fifth beam body 221, the fifth beam body 221 provides a complete, continuous, and high-stiffness bottom support for the hollow pressure sensor, fundamentally eliminating the bending deformation and lateral yaw tendency of the hollow pressure sensor caused by the cantilever effect.

[0050] This application also proposes a method based on a concrete steel bar bond strength test device, and this method includes the following steps: S1. The second tension applying mechanism 20 is in the installation position, and the second tension applying mechanism 20 applies a second tension to the force transmission member 325 incrementally until the first sensor 50 obtains a first load value F1; S2. The second tension applying mechanism 20 is in the installation position, and the second tension applying mechanism 20 applies a second tension to the force transmission member 325 decrementally until the first sensor 50 obtains a preset load value F4, 0 N < F4 < 1 N. Synchronously, the first tension applying mechanism 40 applies a first tension to the force transmission member 325 incrementally; S3. The second tension applying mechanism 20 switches from the installation position to the disassembly position, the device switches to a monitoring device, and the monitoring device is transported to the test environment and placed for a preset time; S4. The monitoring device is removed from the test environment, the second tension applying mechanism 20 switches from the disassembly position to the installation position, the monitoring device switches to the device, the second tension applying mechanism 20 is in the installation position, and the first tension applying mechanism 40 applies a first tension to the force transmission member 325 decrementally until zero. At the current moment, the first sensor 50 obtains a second load value F2, F2 < F1.

[0051] In practical applications, there are inherent error components in the system, which cover mechanical structures, such as threaded pair clearance and micro-deformation of beams. Based on this, in this embodiment, the specimen 80 is replaced with a steel plate with a thickness of 2 mm or more. One end of the steel plate is engaged with the first centering clamp 31, and the other end is engaged with the second centering clamp 32. S1–S4 are repeated, with the first centering clamp 31, the second centering clamp 32, and the steel plate relatively stationary. The first load value F1′ is obtained in S1, and the second load value F2′ is obtained in S4. The difference between F1′ and F2′ is the measurement error value F3.

[0052] The F3 value can be directly used in subsequent specific implementations to correct the actual grip strength degradation (F1−F2−F3), so that the final evaluation result can eliminate device interference.

[0053] The method also includes S5, verifying whether the test can be repeated. If (F1-(F2+F3)) / F1≤5%, the test is qualified; if (F1-(F2+F3)) / F1>5%, then S1-S4 are repeated. (F1-(F2+F3)) / F1 and 5% constitute the test qualification criterion.

[0054] Furthermore, in some embodiments, it is verified whether the experiment is repeated; if ((F1-F t If (F1)% ≤ 5%, then the test is qualified; if (F1 - F t If ) / F1)%>5%, then repeat S1-S4, ((F1-F t ) / F1) / F1 and 5% constitute the test pass criterion.

[0055] Among them, such as Figures 3-6 As shown, a plurality of second sensors 60 are provided on the concrete matrix 82 of the specimen 80. The second sensors 60 are used to obtain the interface slip between the steel bar 81 and the concrete matrix 82. A plurality of third sensors 70 are provided on the steel bar 81 of the specimen 80. The third sensors 70 are used to obtain the true axial strain of the steel bar 81 itself. The third sensors 70 include grating sensors. (1) ; (2) Among them, the cross-section of steel bar 81 is rectangular. This refers to the width of the 81mm rebar. The thickness of the 81mm rebar; Here is the axial elastic modulus of steel bar 81; Here is the axial temperature expansion coefficient of steel bar 81; The temperature change of the first temperature of the monitoring device under S3 relative to the second temperature of the device under S1; (3) (4) Where εf is the average value of data measured by multiple grating sensors; β is the strain transfer efficiency from the grating sensor to the reinforcing bar 81 (81), 0 < β ≤ 1; L is 0.5 times the bonding length; αf is the temperature expansion coefficient of the grating; αfrp is the axial temperature expansion coefficient of the reinforcing bar 81; (5) in, It is the radius of the grating sensor with a protective layer; It is the radius of the unprotected grating; E f It is the elastic modulus of the grating; It is the thickness of the grating adhesive layer; The elastic modulus of the grating adhesive layer; It is the integral angle along the circumference.

[0056] It should be noted that when ((F1-Ft) / F1)%>5%, the correctness of F4 can be verified by (Ft-(F2+F3)) / Ft>5%, and if (Ft-(F2+F3)) / Ft>5%, then F4 is incorrect; or, the correctness of operation S4 can be verified by (F1-(F2+F3)) / F1>5%, and if (F1-(F2+F3)) / F1>5%, then operation S4 is incorrect.

[0057] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A test device for concrete rebar bond strength, characterized in that, include: The first centering clamp (31) is engaged with the loading end (811) of the specimen (80) for traction. The specimen (80) includes a concrete matrix (82) and a steel bar (81) passing through the concrete matrix (82). The steel bar (81) includes a free end (812) and the loading end (811). The second centering clamp (32) is engaged with the concrete matrix (82) for traction. The second centering clamp (32) includes a slender force transmission member (325), the length extension direction of which is parallel to the length direction of the reinforcing bar (81). The first tension application mechanism (40) is used to apply a first tension to the force transmission member (325) in an increasing or decreasing manner, so that the forces applied to the specimen (80) by the second centering clamp (32) and the first centering clamp (31) are equal in magnitude and opposite in direction; The second tension applying mechanism (20) is movable and has an installation position and a disassembly position. The second tension applying mechanism (20) is in the installation position and is used to apply a second tension to the force transmission member (325) incrementally or incrementally, so that the forces applied to the specimen (80) by the second centering clamp (32) and the first centering clamp (31) are equal in magnitude and opposite in direction. The second tension applying mechanism (20) is in the disassembly position. The device includes the first and second centering clamps and the first tension applying mechanism (40) to form a monitoring device. A first sensor (50) is used to acquire the axial force applied to the specimen (80), and the first sensor (50) is mounted on the second tension application mechanism (20). In S1, the second tension application mechanism (20) is in the loading position, and the second tension application mechanism (20) applies the second tension to the force transmission member (325) incrementally until the first sensor (50) acquires the first load value F1; S2. The second tension application mechanism (20) is in the loading position. The second tension application mechanism (20) applies the second tension to the force transmission member (325) in a decreasing manner until the first sensor (50) obtains the preset load value F4, 0N < F4 < 1N. Simultaneously, the first tension application mechanism (40) applies the first tension to the force transmission member (325) in an increasing manner. S3. The second tension application mechanism (20) is switched from the installation position to the disassembly position, the device is switched to the monitoring device, and the monitoring device is transferred to the test environment and placed for a preset time. S4. The monitoring device is removed from the test environment, the second tension application mechanism (20) is switched from the disassembly position to the installation position, the monitoring device is switched to the device, the second tension application mechanism (20) is in the loading position, the first tension application mechanism (40) applies the first tension to the force transmission component (325) decreasingly until zero, and at the current moment the first sensor (50) obtains the second load value F2, F2 < F1.

2. The apparatus according to claim 1, characterized in that, The first tension application mechanism (40) includes a spring (41) and a pressure plate (42) disposed at one end of the spring (41), and the force transmission member (325) passes through the spring (41) and the pressure plate (42). The force transmission component (325) includes a first threaded section, and a nut (A) is connected to the first threaded section to press the spring (41). The compression of the spring (41) is adjusted by the nut (A) to apply the first tension to the force transmission component (325) in an increasing or decreasing manner.

3. The apparatus according to claim 2, characterized in that, It also includes a support frame (10), which includes a first beam (11) and a second beam (12) disposed opposite to each other. The first centering clamp (31) and the second centering clamp (32) are located between the first beam (11) and the second beam (12). The first centering clamp (31) is disposed close to the first beam (11), and the second centering clamp (32) is disposed close to the second beam (12). The second centering clamp (32) and the spring (41) are located on both sides of the second beam (12), the force transmission member (325) passes through the second beam (12), and the other end of the spring (41) is pressed onto the second beam (12).

4. The apparatus according to claim 3, characterized in that, The supporting frame (10) also includes a third beam (13) and a fourth beam (14) arranged opposite to each other. The first beam (11), the third beam (13), the second beam (12), and the fourth beam (14) are connected end to end in sequence to form a rectangular frame. The first centering clamp (31) includes a first fixing part (311) and a first hinge part (312). The first fixing part (311) is installed on the first beam (11). The first hinge part (312) can clamp the loading end (811). The first hinge part (312) is hinged to the first fixing part (311) so that the first centering clamp (31) can adjust the length extension direction of the reinforcing bar (81). The second centering clamp (32) includes the force transmission component (325), the connecting rod (324), and the first centering component (321), the second centering component (322), and the traction assembly (323) arranged sequentially from the second beam (12) to the first beam (11). The traction assembly (323) includes a first traction plate (3231) and a second traction plate (3232) disposed opposite to each other, and a plurality of screws (3233). The screws (3233) pass through the first traction plate (3231) and the second traction plate (3232). The plurality of screws (3233) are arranged around the edges of the first traction plate (3231) and the second traction plate (3232). Each screw (3233) is provided with a plurality of locking nuts to provide space between the first traction plate (3231) and the second traction plate (3232) for accommodating the concrete substrate (82) and the free end (812). The concrete substrate (82) contacts one of the first traction plate (3231) and the second traction plate (3232), so that the traction assembly (323) and the concrete substrate (82) can be tractionally engaged. The length direction of the connecting rod (324) is the same as or parallel to the length direction of the force transmission member (325). One end of the connecting rod (324) is connected to the other of the first traction plate (3231) and the second traction plate (3232), and passes through the second centering member (322) until the first centering member (321). The first centering member (321) has the same structure as the first centering clamp (31), including a second fixing part (3212) and a second hinge part (3211). The second hinge part (3211) can clamp the other end of the connecting rod (324). One end of the force transmission member (325) is connected to the second fixing part (3212), and the other end of the force transmission member (325) passes through the second beam (12), the spring (41), and the pressure plate (42) in sequence. Under the action of the first centering clamp (31), the first centering member (321), and the second centering member (322), the length extension direction of the force transmission member (325) is the same as the length extension direction of the reinforcing bar (81).

5. The apparatus according to claim 3, characterized in that, The second tension application mechanism (20) includes a connecting frame (22) which is fitted into the second beam (12).

6. The apparatus according to claim 5, characterized in that, The second tension application mechanism (20) also includes a force application element (21), and the connecting frame (22) includes a fifth beam (221). The force-applying component (21) and the first sensor (50) are located on one side of the second beam (12), the spring (41) is located on the other side of the second beam (12), the force-transmitting component (325) passes through the fifth beam (221), the first sensor (50) and the force-applying component (21) are installed on the force-transmitting component (325), and the first sensor (50) is sandwiched between the fifth beam (221) and the force-applying component (21). The spring (41) switches from the compressed state to the initial state, and there is a safe distance between the pressure plate (42) and the fifth beam (221).

7. The apparatus according to claim 6, characterized in that, The force-applying component (21) includes a jack or a fastening nut that is threadedly connected to the force-transmitting component (325).

8. The apparatus according to claim 7, characterized in that, The force-applying component (21) is the jack. The force transmission component (325) further includes a second threaded section, and another nut (B) is connected to the second threaded section, so that the connecting frame (22) is in seamless contact with the second beam (12), the first sensor (50) is in seamless contact with the fifth beam (221), and the first sensor (50) is in seamless contact with the jack. The jack is a hollow jack, the first sensor (50) is a hollow pressure sensor, and the force transmission component (325) passes through the hollow area of ​​the hollow jack and the hollow area of ​​the hollow pressure sensor.

9. The apparatus according to claim 8, characterized in that, The orthographic projection of the hollow pressure sensor onto the fifth beam (221) is completely located on the fifth beam (221), and the radial dimension of the hollow pressure sensor is smaller than the radial dimension of the hollow jack body.

10. The apparatus according to claim 8, characterized in that, The connecting frame (22) also includes a sixth beam (222) and a seventh beam (223) located on both sides of the fifth beam (221), and the sixth beam (222), the seventh beam (223) and the fifth beam (221) form a U-shape; A stop (121) is formed on the second beam (12) and oppositely arranged. A slot is formed between the two stop (121). One slot is inserted into the free end of the sixth beam (222) and the other slot is inserted into the free end of the seventh beam (223), so that the connecting frame (22) and the second beam (12) are inserted into each other. At the current moment, the connecting frame (22) and the support frame (10) are arranged vertically. When the connecting frame (22) and the second beam (12) are engaged, the second tension application mechanism (20) is positioned in the installation position; when the connecting frame (22) and the second beam (12) are disengaged, the second tension application mechanism (20) is positioned in the disassembly position. The free ends of the sixth beam (222) and the seventh beam (223) are in planar contact with the second beam (12).

11. A method for testing the bond strength of reinforced concrete, applied to the apparatus according to any one of claims 1-10, characterized in that, include: S1, the second tension application mechanism (20) is in the loading position, and the second tension application mechanism (20) applies the second tension to the force transmission member (325) incrementally until the first sensor (50) acquires the first load value F1; S2. The second tension application mechanism (20) is in the loading position. The second tension application mechanism (20) applies the second tension to the force transmission member (325) in a decreasing manner until the first sensor (50) obtains the preset load value F4, 0N < F4 < 1N. Simultaneously, the first tension application mechanism (40) applies the first tension to the force transmission member (325) in an increasing manner. S3. The second tension application mechanism (20) is switched from the installation position to the disassembly position, and the device is switched to the monitoring device; and the monitoring device is transferred to the test environment and placed for a preset time. S4. The monitoring device is removed from the test environment, the second tension application mechanism (20) is switched from the disassembly position to the installation position, the monitoring device is switched to the device, the second tension application mechanism (20) is in the loading position, the first tension application mechanism (40) applies the first tension to the force transmission component (325) decreasingly until zero, and at the current moment the first sensor (50) obtains the second load value F2, F2 < F1.

12. The method according to claim 11, characterized in that, The difference between the first load value F1 and the second load value F2 includes the measurement error value F3. The specimen (80) is replaced with a steel plate with a thickness of more than 2 mm. One end of the steel plate is engaged with the first centering clamp (31) and the other end is engaged with the second centering clamp (32). S1-S4 are repeated. The first centering clamp (31), the second centering clamp (32) and the steel plate are relatively stationary. The first load value F1′ is obtained in S1 and the second load value F2′ is obtained in S4. The difference between F1′ and F2′ is the measurement error value F3.

13. The method according to claim 12, characterized in that, Also includes: S5. Verify whether the test can be repeated. If (F1-(F2+F3)) / F1≤5%, the test is qualified. If (F1-(F2+F3)) / F1>5%, then repeat S1-S4.

14. The method according to claim 12, characterized in that, Also includes: S5. Verify whether the experiment can be repeated. If ((F1-F t If (F1)% ≤ 5%, then the test is qualified; if (F1 - F t If ) / F1)%>5%, then repeat S1-S4. The specimen (80) has multiple second sensors (60) on its concrete matrix (82), which are used to acquire the interface slip between the reinforcing bar (81) and the concrete matrix (82); the specimen (80) has multiple third sensors (70) on its reinforcing bar (81), which are used to acquire the true axial strain of the reinforcing bar (81); the second sensors (60) are dial indicator clamps; the third sensors (70) include grating sensors. (1) ； (2) The cross-section of the steel bar (81) is rectangular. The width of the reinforcing bar (81); The thickness of the reinforcing bar (81); The axial elastic modulus of the reinforcing bar (81); is the axial temperature expansion coefficient of the reinforcing bar (81); The temperature change of the first temperature of the monitoring device under S3 relative to the second temperature of the device under S1; (3) (4) in, The average value of data measured by multiple grating sensors; For the strain transfer efficiency from the grating sensor to the reinforcing bar (81), 0 < β ≤ 1; The pasting length is 0.5 times the original length. It is the coefficient of thermal expansion of the grating; is the axial temperature expansion coefficient of the reinforcing bar (81); (5) in, It is the radius of the grating sensor with a protective layer; It is the radius of the grating without a protective layer; It is the elastic modulus of the grating; It is the thickness of the grating adhesive layer; The elastic modulus of the grating adhesive layer; It is the integral angle along the circumference.

15. The method according to claim 14, characterized in that, When ((F1-F) t When ) / F1)%>5%, Verify that F4 is correct by (Ft-(F2+F3)) / Ft>5%; or verify that S4 is correct by (F1-(F2+F3)) / F1>5%.

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