A test apparatus and method for bond slip between corroded steel and concrete

Abstract

This invention relates to the field of building structure testing, specifically to a test device and method for bond-slip testing of corroded steel and concrete. The device includes a frame, with a seismic simulation device connected to the bottom of the frame for mounting a steel-concrete composite test specimen. The test specimen has an exposed upper section of I-beam cast inside. A contact device fitted onto the test specimen is connected to the middle of the frame. A lifting and lowering power device is installed at the top of the frame. A locking device and a clamping device connected to the upper part of the I-beam are connected to the lower side of the power device, and a slip detection device is also provided. This device can simulate the seismic state of steel-concrete composite specimens under bond-slip testing and can effectively simulate the bond-slip curve of steel-concrete composite specimens under seismic conditions.

Description

Technical Field

[0001] This invention relates to the field of building structure testing, specifically to a test device and method for bond slip test between corroded steel and concrete. Background Technology

[0002] Bond-slip is a critical issue in steel-concrete composite structures. It plays a significant role in the nonlinear analysis of reinforced concrete (RC) structures. Bond-slip performance testing is an important method for establishing bond-slip properties in steel-concrete composite structures. Existing testing methods include pull-out tests, beam-type tests, and central tension tests. Pull-out tests use grooved reinforcing bars to measure the slip displacement of the reinforcing bars at the loaded and free ends of the specimen. The bond stress-slip displacement (τ-s) curve is then used to reflect the bond-slip performance of the specimen.

[0003] However, existing adhesive-slip performance testing devices cannot achieve rapid connection of the steel loading end when simulating the adhesive-slip performance between corrosive steel and concrete; at the same time, they cannot simulate the adhesive-slip performance between steel and concrete under seismic conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a test device and method for bond slip testing of corroded steel and concrete. This device can simulate the seismic state of steel-concrete specimens under bond slip test and can effectively simulate the bond slip curve of steel-concrete specimens under seismic state.

[0005] The technical solution of the present invention is as follows: a test device for bonding and slippage between corroded steel and concrete, comprising a frame, an earthquake simulation device for mounting a steel-concrete composite test specimen connected to the bottom of the frame, an exposed upper I-beam inside the steel-concrete composite test specimen, a contact device fitted onto the steel-concrete composite test specimen connected to the middle of the frame, a lifting and lowering power device installed at the top of the frame, a locking device and a clamping device connected to the upper part of the I-beam connected to the lower side of the power device, and a slippage detection device provided.

[0006] Furthermore, the earthquake simulation device includes a bottom tray and side plates fixed around the bottom of the frame. Lateral hydraulic rods are longitudinally slidably connected to the inner walls of the left and right side plates, and these lateral hydraulic rods are vertically slidably connected to the bottom tray. Longitudinal hydraulic rods are slidably connected laterally to the inner walls of the front and rear side plates, and these longitudinal hydraulic rods are vertically slidably connected to the bottom tray. A base plate is fixed between the lower parts of the front and rear side plates, and vertical hydraulic rods are longitudinally slidably connected to the base plate. The upper ends of these vertical hydraulic rods are slidably connected laterally to the bottom surface of the bottom tray. A fixing mechanism for connecting steel-concrete composite test specimens is provided on the bottom tray.

[0007] Furthermore, the fixing mechanism includes adjustment slots located on the bottom tray and on the left and right sides of the steel-concrete composite test piece. I-shaped sliding connectors are slidably connected in each adjustment slot. A fastening bolt is threaded through the top of each I-shaped sliding connector and is threaded to it. Clamping plates are welded to the inner sides of each I-shaped sliding connector. Through pins for penetrating the steel-concrete composite test piece are inserted through each clamping plate. A fixing nut is screwed to the end of each through pin that protrudes from the clamping plate.

[0008] Furthermore, the contact device includes a circular connecting seat that is fitted over the steel-concrete test piece. The circular connecting seat is fixedly connected to the frame via a fixing bracket, and a contact airbag is installed on the inner wall of the circular connecting seat.

[0009] Furthermore, the power unit includes an inverted U-shaped connecting frame, a top plate with a movable slot fixed to the top of the frame, the connecting frame extending vertically through the movable slot to the bottom of the top plate, a connecting plate fixed to the lower end of the connecting frame, a top hydraulic rod slidably connected to the top plate vertically installed on the inner side of the top of the connecting frame, and a bottom hydraulic rod slidably connected to the top plate vertically installed on the connecting plate.

[0010] Furthermore, the locking device includes a connecting shaft passing through the connecting disc, the connecting shaft being rotatably connected to the connecting disc and driven to rotate by a driving mechanism, a locking ring being fixed at the lower end of the connecting shaft, a locking pin being fixed on the inner wall of the locking ring, and a snap-fit ​​groove for engaging with the locking pin being opened on the upper side of the I-beam.

[0011] Furthermore, a contact block is installed on the side of one of the locking pins, and a push switch electrically connected to the power source of the drive mechanism is installed on the inner side of the contact block.

[0012] Furthermore, the drive mechanism includes a drive gear fixed to the upper end of the connecting shaft, the drive gear meshing with the driving gear, and the driving gear being connected to the output end of a motor mounted on the connecting plate.

[0013] Furthermore, the clamping device includes a plurality of vertical connecting rods fixed at intervals along the circumferential direction on the bottom surface of the connecting plate. The lower end of each vertical connecting rod is hinged to an inclined fixing rod. The fixing rod is hinged to a clamping block away from the vertical connecting rod. A clamping hydraulic rod is hinged between the fixing rod and the vertical connecting rod. The bottom surface of the connecting plate is also vertically fixed with a suspension rod whose lower inner side is used to install a slip detection device.

[0014] A method for testing the bond-slip between corroded steel and concrete, employing a test device for bond-slip between corroded steel and concrete, includes the following steps:

[0015] 1) Cast the steel-concrete test specimen and cut out the snap-fit ​​groove on the exposed I-beam part of the steel-concrete test specimen.

[0016] 2) Place the cast steel-concrete composite test specimen on the earthquake simulation device and fix it in place;

[0017] 3) Adjust the height of the locking ring so that it fits onto the end of the I-beam. Fine-tune the locking ring until the locking pin is parallel to the locking groove. Drive the locking ring to rotate through the drive mechanism so that the locking pin matches the locking groove.

[0018] 4) The clamping device contacts and clamps the I-beam;

[0019] 5) The earthquake simulation device operates, simulating earthquake motion scenarios;

[0020] 6) The top and bottom hydraulic rods work alternately to realize the application of vertical load on the steel-concrete composite test specimen. The displacement acquisition instrument in the slip detection device acquires the slip of the steel and plots the stress-displacement curve.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The test device and method for bonding and slipping of corroded steel and concrete can simulate the seismic state of steel-concrete specimens under bonding and slipping test by setting up a seismic simulation device, and simulate the horizontal lateral force of the steel-concrete specimens by contacting the specimens with contact airbags, which can effectively simulate the bonding and slipping curve of steel-concrete specimens under seismic state.

[0023] 2. The test device and method for bonding and slippage between corroded steel and concrete can realize the vertical bidirectional tensile and compressive load test of steel-concrete specimens by adjusting the working state of the top hydraulic rod and the bottom hydraulic rod set on the power device.

[0024] 3. The test device and method for bonding and slippage between corroded steel and concrete can achieve the connection between the snap-fit ​​groove and the locking pin under the rotation of the motor by using the snap-fit ​​groove opened on the steel, which effectively improves the efficiency of rapid connection and installation of steel-concrete test.

[0025] 4. The bonding and slip test device and method for corroded steel and concrete can achieve docking between the clamping block and the I-shaped corroded steel by setting up a clamping device and driving the clamping hydraulic rod, which effectively improves the clamping stability of the I-shaped steel. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention. Figure 1 ;

[0027] Figure 2 This is a schematic diagram of the structure of the present invention. Figure 2 ;

[0028] Figure 3 This is a schematic diagram of the structure of the present invention. Figure 3 ;

[0029] Figure 4 For the present invention Figure 3 Schematic diagram of the cross-section at point A in the middle;

[0030] Figure 5 For the present invention Figure 3 Schematic diagram of the structure at point B;

[0031] In the diagram: 1. Frame; 2. Earthquake simulation device; 201. Side plate; 202. Base plate; 203. Lateral hydraulic rod; 204. Connecting frame; 205. Vertical hydraulic rod; 206. Forward hydraulic rod; 207. Bottom tray; 208. Adjustment groove; 210. I-shaped sliding connector; 211. Fastening bolt; 212. Clamping plate; 213. Through pin; 214. Fixing nut; 3. Steel-concrete test piece; 4. I-shaped steel; 401. Clip groove; 5. Power unit; 501. Connecting frame; 502. Top hydraulic rod; 503. Sliding block one; 504. Bottom hydraulic... 505. Rod; 506. Connecting plate; 507. Sliding block II; 6. Locking device; 601. Connecting shaft; 602. Locking ring; 603. Locking pin; 604. Fixing block; 605. Contact block; 606. Drive gear; 607. Motor; 608. Drive gear; 7. Clamping device; 701. Vertical connecting rod; 702. Fixing rod; 703. Clamping hydraulic rod; 704. Clamping block; 705. Suspension rod; 8. Contact device; 801. Fixing frame; 802. Circular connecting seat; 803. Contact airbag; 9. Movable groove; 10. Top plate; 11. Slip detection device. Detailed Implementation

[0032] To make the above features and advantages of the present invention more readily understood, specific embodiments are described below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0033] refer to Figures 1 to 5

[0034] A test device for bonding and slippage of corroded steel and concrete includes a frame 1. The bottom of the frame 1 is connected to an earthquake simulation device 2 for mounting a steel-concrete composite test piece 3. The steel-concrete composite test piece 3 has an exposed upper I-beam 4 cast inside. The middle of the frame 1 is connected to a contact device 8 that is fitted onto the steel-concrete composite test piece 3. The top of the frame 1 is equipped with a lifting and lowering power device 5. The lower side of the power device 5 is connected to a locking device 6 and a clamping device 7 that are connected to the upper part of the I-beam 4, and a slippage detection device 11 is provided.

[0035] In this embodiment, the earthquake simulation device 2 includes a bottom tray 207 and side plates 201 fixed around the bottom of the frame 1; a pair of horizontally placed lateral hydraulic rods 203 are longitudinally slidably connected to the inner walls of the left and right side plates 201; a pair of vertically placed connecting frames 204 (the long side of the connecting frame is vertical) are fixed to the left and right sides of the bottom tray 207; the output end of the lateral hydraulic rod 203 is vertically slidably connected to the corresponding connecting frame 204.

[0036] A longitudinally placed positive hydraulic rod 206 is slidably connected to the middle of the inner wall of the side plate 201 on both the front and rear sides. A vertically placed connecting frame 204 (the long side of the connecting frame is vertical) is fixed to the middle of the front and rear sides of the bottom tray 207. The output end of the positive hydraulic rod 206 is vertically slidably connected to the corresponding connecting frame 204.

[0037] A pair of base plates 202 are fixed between the lower parts of the side plates 201 on the front and rear sides. Each base plate 202 has a vertical hydraulic rod 205 slidably connected longitudinally. The upper end of the vertical hydraulic rod 205 is laterally slidably connected to the bottom surface of the bottom tray 207. Specifically, the upper end of the vertical hydraulic rod 205 is laterally slidably connected to the bottom tray 207 via a connecting frame (the long side of the connecting frame is laterally oriented) that is laterally fixed to the bottom surface of the bottom tray 207. The lower end of the vertical hydraulic rod 205 is longitudinally slidably connected to the base plate 202 via a connecting frame (the long side of the connecting frame is longitudinally oriented) that is longitudinally fixed to the base plate 202. Note: In this invention, "lateral" refers to the left-right direction, "longitudinal" refers to the front-back direction, and "vertical" refers to the up-down direction.

[0038] The earthquake simulation device 2 can simulate the base plate 202 under earthquake conditions by alternating the operation of the lateral hydraulic rod 203, the connecting frame 204, the vertical hydraulic rod 205, and the forward hydraulic rod 206, and can effectively test the bonding and sliding performance of steel-concrete composite components.

[0039] In this embodiment, the bottom tray 207 is also provided with a fixing mechanism for connecting the steel-concrete composite test piece 3. Specifically, the fixing mechanism includes adjustment slots 208 formed on the bottom tray 207 and located on the left and right sides of the steel-concrete composite test piece 3. I-shaped sliding connectors 210 are slidably connected within each adjustment slot 208. A fastening bolt 211 threaded through the top of each I-shaped sliding connector 210 is vertically inserted into it. Clamping plates 212 are welded to the inner surfaces of each I-shaped sliding connector 210. A pair of through pins 213 for laterally penetrating the steel-concrete composite test piece 3 are inserted through each clamping plate 212. A fixing nut 214 is screwed to the end of each through pin 213 that protrudes from the clamping plate 212. After the through pin 213 penetrates the steel-concrete composite test piece 3, it is clamped by the two clamping plates 212 through the fixing nut 214. Tightening the fastening bolt 211 downwards locks the I-shaped sliding connector 210, thus locking the steel-concrete composite test piece 3.

[0040] In this embodiment, the contact device 8 includes a circular connecting seat 802 fitted outside the steel-concrete composite test piece 3. The circular connecting seat 802 is welded and fixed to the frame 1 via a fixing bracket 801. A contact airbag 803 is installed on the inner wall of the circular connecting seat 802. After the contact airbag 803 is inflated, it can exert a lateral force on the contact airbag 803 through the movement of the steel-concrete composite test piece 3, effectively simulating the unstable lateral load situation under earthquake conditions.

[0041] In this embodiment, the power unit 5 includes a connecting frame 501. A top plate 10 is welded and fixed to the top of the frame 1. A pair of movable slots 9 are provided on the top plate. The connecting frame 501 extends vertically through the movable slots 9 and to the bottom of the top plate 10. A connecting plate 505 is fixed to the lower end of the connecting frame 501. A top hydraulic rod 502 is vertically fixed to the inner side of the top of the connecting frame 501. The top hydraulic rod 502 is located between the pair of movable slots 9 and its lower end is slidably connected to the top plate 10. A bottom hydraulic rod 504 is vertically fixed to the connecting plate 505 and its upper end is slidably connected to the top plate 10. The connecting plate 505 can be driven to move up and down by the top hydraulic rod 502 and the bottom hydraulic rod 504, which can facilitate vertical compression and pull-out tests on the steel-concrete composite test specimen 3.

[0042] In this embodiment, in order to better achieve the sliding connection between the top hydraulic rod 502, the bottom hydraulic rod 504 and the top plate, the bottom of the top hydraulic rod 502 is fixed with a sliding block 503 that is slidably connected to the top of the top plate, and the top of the bottom hydraulic rod 504 is fixed with a sliding block 506 that is slidably connected to the bottom of the top plate.

[0043] In this embodiment, the connecting frame 501 is inverted U-shaped to facilitate loading operations by the top hydraulic rod 502.

[0044] In this embodiment, to connect with the I-beam 4 of the steel-concrete composite test piece 3, the locking device 6 includes a connecting shaft 601 passing through a connecting plate 505 at its upper part. The connecting shaft 601 is rotatably connected to the connecting plate 505 via a connecting flange and is driven to rotate by a driving mechanism. A locking ring 602 is fixed to the lower end of the connecting shaft 601. Several locking pins 603 are fixed at intervals on the inner wall of the locking ring 602. The upper side of the I-beam 4 has a snap-fit ​​groove 401 for engaging with the locking pins 603. By adjusting the locking ring 602 with the top hydraulic rod 502 and the bottom hydraulic rod 504, the locking pins 603 inside the locking ring 602 can be aligned parallel to the snap-fit ​​groove 401. The driving mechanism can rotate the locking ring 602 and engage the locking pins 603 with the snap-fit ​​groove 401.

[0045] In this embodiment, in order to drive the connecting shaft 601 to rotate, the driving mechanism includes a driving gear 606 fixed on the upper end of the connecting shaft 601. The driving gear 606 meshes with the drive gear 608, and the drive gear 608 is connected to the output end of the motor 607 mounted on the connecting plate 505.

[0046] In this embodiment, a contact block 605 is installed on the side of one of the locking pins, and a push switch electrically connected to the controller of the motor 607 is installed on the inner side of the contact block 605. When the contact block 605 contacts the profile steel, the motor 607 stops running, realizing the docking operation of the locking device 6.

[0047] In this embodiment, the clamping device 7 includes a plurality of vertical connecting rods 701 fixed at intervals along the circumferential direction on the bottom surface of the connecting plate 505. The lower end of each vertical connecting rod 701 is hinged to an inclined fixing rod 702. The fixing rod 702 is hinged to a clamping block 704 away from the vertical connecting rod 701. A clamping hydraulic rod 703 is provided between the fixing rod 702 and the vertical connecting rod 701. Both ends of the clamping hydraulic rod 703 are hinged to the fixing rod 702 and the clamping hydraulic rod 703. The clamping block 704 and the contact surface with the corrosion-resistant steel adopt a pin-type contact, which effectively improves the connection stability between the clamping device 7 and the corrosion-resistant steel.

[0048] In this embodiment, the bottom surface of the connecting plate 505 is also vertically fixed with a suspension rod 705 on the inner side of its lower end for mounting the sliding detection device 11.

[0049] A method for testing the bond-slip between corroded steel and concrete, employing a test device for bond-slip between corroded steel and concrete, includes the following steps:

[0050] 1) Cast the steel-concrete test specimen 3, and cut the snap-fit ​​groove 401 on the exposed I-beam 4 of the steel-concrete test specimen 3.

[0051] 2) Place the cast steel-concrete test specimen 3 on the bottom tray 207, adjust the I-type sliding connector 210 to place the cast test specimen on the bottom tray 207, insert the pin 213 through the steel-concrete test specimen 3, and tighten the fixing nuts 214 at both ends to complete the fixing of the steel-concrete test specimen 3.

[0052] 3) Adjust the height of the locking ring 602 so that the locking ring 602 is sleeved on the end of the I-beam 4, and finely adjust the locking ring 602 until the locking pin 603 is parallel to the snap-fit ​​groove 401. Drive the locking ring 602 to rotate through the motor 607 so that the locking pin 603 matches the snap-fit ​​groove 401.

[0053] 4) The clamping hydraulic rod 703 is activated, bringing the clamping block 704 into contact with and clamping the I-beam 4;

[0054] 5) The alternating operation of the lateral hydraulic rod 203, the bottom hydraulic rod 205, and the forward hydraulic rod 206 simulates a seismic motion scenario;

[0055] 6) The top hydraulic rod 502 and the bottom hydraulic rod 504 work alternately to realize the application of load in the vertical direction of the steel-concrete test specimen 3. The displacement acquisition instrument in the slip detection device 11 acquires the slip of the steel and plots the stress-displacement curve.

[0056] The above description is only a preferred embodiment of the present invention. For those skilled in the art, designing different forms of corrosion-resistant steel and concrete bond slip test devices and methods based on the teachings of the present invention does not require creative labor. All equivalent changes, modifications, substitutions and variations made in accordance with the scope of the patent application of the present invention without departing from the principles and spirit of the present invention shall be covered by the present invention.

Claims

1. A test device for bond slippage between corroded steel and concrete, comprising a frame (1), characterized in that, The bottom of the frame (1) is connected to an earthquake simulation device (2) for installing a steel-concrete composite test piece (3). The steel-concrete composite test piece (3) has an exposed upper I-beam (4) inside. The middle of the frame (1) is connected to a contact device (8) fitted onto the steel-concrete composite test piece (3). The top of the frame (1) is equipped with a lifting power device (5). The lower side of the power device (5) is connected to a locking device (6) and a clamping device (7) connected to the upper part of the I-beam (4), and a slip detection device (11) is provided. The earthquake simulation device (2) includes a bottom tray (207) and side plates (201) fixed around the bottom of the frame (1). The inner walls of the left and right side panels (201) are longitudinally slidably connected with horizontally placed lateral hydraulic rods (203), which are vertically slidably connected to the bottom tray (207); the inner walls of the front and rear side panels (201) are horizontally slidably connected with longitudinally placed forward hydraulic rods (206), which are vertically slidably connected to the bottom tray (207); a base plate (202) is fixed between the lower parts of the front and rear side panels (201), and a vertical hydraulic rod (205) is longitudinally slidably connected to the base plate (202). The upper end of the vertical hydraulic rod (205) is horizontally slidably connected to the bottom surface of the bottom tray (207), which is vertically slidably connected to the bottom surface of the bottom tray (207). 207) is provided with a fixing mechanism for connecting the steel-concrete composite test piece (3); the contact device (8) includes a circular connecting seat (802) sleeved on the steel-concrete composite test piece (3), the circular connecting seat (802) is fixedly connected to the frame (1) around the perimeter by a fixing frame (801), and a contact airbag (803) is installed on the inner wall of the circular connecting seat (802); the power device (5) includes a U-shaped connecting frame (501), the top of the frame (1) is fixed with a top plate (10) with an opening of a movable slot (9), the connecting frame (501) vertically penetrates the movable slot (9) and extends to the bottom of the top plate (10), and a connecting plate (503) is fixed at the lower end of the connecting frame (501). 5) A top hydraulic rod (502) that is slidably connected to the top plate (10) is vertically installed on the inner side of the top of the connecting frame (501), and a bottom hydraulic rod (504) that is slidably connected to the top plate (10) is vertically installed on the connecting plate (505); the locking device (6) includes a connecting shaft (601) that passes through the connecting plate (505), the connecting shaft (601) is rotatably connected to the connecting plate (505) and driven to rotate by the driving mechanism, a locking ring (602) is fixed at the lower end of the connecting shaft (601), a locking pin (603) is fixed on the inner wall of the locking ring (602), and a snap-fit ​​groove (401) for cooperating with the locking pin (603) is opened on the upper side of the I-beam (4);The clamping device (7) includes a plurality of vertical connecting rods (701) fixed at intervals along the circumferential direction on the bottom surface of the connecting plate (505). The lower ends of the vertical connecting rods (701) are hinged to inclined fixing rods (702). Clamping blocks (704) are hinged to the fixing rods (702) away from the vertical connecting rods (701). A clamping hydraulic rod (703) is hinged between the fixing rods (702) and the vertical connecting rods (701). The bottom surface of the connecting plate (505) is also vertically fixed with a suspension rod (705) whose lower inner side is used to install a sliding detection device (11).

2. The bonding slip test device for corrosion-resistant steel and concrete according to claim 1, characterized in that, The fixing mechanism includes adjustment slots (208) on the bottom tray (207) and located on the left and right sides of the steel-concrete test piece (3). I-shaped sliding connectors (210) are slidably connected in the adjustment slots (208). The top of the I-shaped sliding connectors (210) is vertically provided with fastening bolts (211) threaded to them. The inner side of the I-shaped sliding connectors (210) is welded with clamps (212). The clamps (212) are provided with through pins (213) for penetrating the steel-concrete test piece (3). The end of the through pins (213) that protrudes from the clamps (212) is screwed with a fixing nut (214).

3. The bonding slip test device for corrosion-resistant steel and concrete according to claim 1, characterized in that, One of the locking pins has a contact block (605) mounted on its side, and a push switch electrically connected to the power source of the drive mechanism is mounted on the inner side of the contact block (605).

4. A test device for bond slippage between corroded steel and concrete according to claim 1 or 3, characterized in that, The drive mechanism includes a drive gear (606) fixed on the upper end of the connecting shaft (601), the drive gear (606) meshing with the drive gear (608), and the drive gear (608) being connected to the output end of a motor (607) mounted on the connecting plate (505).

5. A method for testing the bond-slip between corroded steel and concrete, using the bond-slip testing device for corroded steel and concrete as described in claim 1 or 3, characterized in that, Includes the following steps: 1) Cast steel-concrete test specimen (3) and cut out a snap-fit ​​groove (401) on the exposed I-beam (4) of the steel-concrete test specimen (3). 2) Place the cast steel-concrete test specimen (3) on the earthquake simulation device (2) and fix it; 3) Adjust the height of the locking ring (602) so that the locking ring (602) is sleeved on the end of the I-beam (4), and finely adjust the locking ring (602) until the locking pin (603) is parallel to the snap-fit ​​groove (401). Drive the locking ring (602) to rotate through the drive mechanism so that the locking pin (603) matches the snap-fit ​​groove (401); 4) The clamping device (7) contacts and clamps the I-beam (4); 5) The earthquake simulation device (2) operates to simulate earthquake motion scenarios; 6) The top hydraulic rod (502) and the bottom hydraulic rod (504) work alternately to realize the vertical load application of the steel-concrete test piece (3) in the vertical direction. The displacement acquisition instrument in the slip detection device (11) acquires the slip of the steel and plots the stress-displacement curve.

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