Device for testing the bond performance between high stress horizontal steel bars and concrete subjected to lateral pressure

Abstract

The present invention discloses a device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to transverse pressure. The device comprises two columns, an upper beam and a bottom beam are arranged between the two columns, the upper beam is located above the bottom beam, a bottom base is arranged on the bottom beam between the upper beam and the bottom beam, a self-balancing loading frame for accommodating reinforced concrete specimens is arranged on the bottom base, one end of the self-balancing loading frame is laterally connected to one end of a dynamic and static tension and compression servo actuator through a box-type distribution beam, and the other end of the dynamic and static tension and compression servo actuator is connected to the column; a servo actuator is slidingly arranged on the upper beam, and the servo actuator is vertically located above the self-balancing loading frame. The good integrity of the device enables the loading frame to achieve rigid self-balancing, and can realize one-end push-and-pull tests of reinforced concrete specimens and bond slip performance tests of reinforced concrete under reciprocating loads under high stress conditions, which conforms to the actual stress and seismic load conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of testing equipment, and in particular relates to a device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to transverse pressure. Background Art

[0002] In reinforced concrete structures, the two materials, steel bars and concrete, with completely different properties, are able to work together, mainly relying on the bond stress between them, that is, the shear stress on the contact surface. The bond stress state between steel bars and concrete directly affects the quality of reinforced concrete, so the bond slip performance of reinforced concrete has an important impact on engineering structures. For example, in the anchorage area of ​​beam and column structures, the steel bars are not only subjected to simple tension, but also to shear and bending moments acting simultaneously. When subjected to seismic forces, there are even reciprocating loads. In reinforced concrete structures with cross-shaped beam-column nodes, when the structure is subjected to horizontal loads, the bending moments at the left and right points in the horizontal direction of the node are opposite. At the same time, the upper structure of the node has a certain yield strength ratio, which restricts the vertical displacement of the node and applies loads. In order to better simulate the bond state between steel bars and concrete, it is necessary to conduct bond slip performance tests on this part of the steel bars to ensure the stiffness of the structure, which is very important for the stability of beam and column structures.

[0003] At present, the main methods for testing the bond-slip performance of reinforced concrete include pull-out tests and beam tests. Existing bond-slip performance tests mainly use a steel bar pull-out device under unidirectional loads. In traditional pull-out tests, the steel bar tension and bond force are balanced forces. After the bond is broken, the steel bar tension will also decrease. However, the steel bars in the node area are subjected to strong tension and the concrete is subjected to strong pressure. Even if the bond is broken, the steel bars are in a high stress state. Traditional pull-out tests are unable to test the bond-slip performance of steel bars and concrete under reciprocating loads. They do not consider the bond-slip performance of steel bars when they are subjected to other stress states (such as high stress levels, sinusoidal loads, square waves and other dynamic loads), and cannot better correspond to the load conditions that steel bars and concrete are subjected to in reality. Summary of the Invention

[0004] To address the aforementioned shortcomings of the prior art, the present invention provides a device for testing the bond performance between high-stress rebar and concrete subjected to lateral pressure. The device's superior integrity enables a rigid, self-balancing loading frame, enabling testing of the bond-slip performance of rebar and concrete under reciprocating loads at high stress levels. A self-balancing reaction frame applies pre-tension to the rebar, achieving high stress levels in the rebar while accounting for the "Poisson effect" of elongated and tapered rebar. The lateral pressure applied by the servo actuator of the external reaction frame better reflects the actual stress state of the concrete in the joint area.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A device for testing the bond slip performance of steel bars and concrete under reciprocating loads is provided, comprising two columns, with an upper beam and a lower beam disposed between the two columns. The upper beam is located above the lower beam, and the columns, upper beam, and lower beam together constitute the device's external self-balancing frame. A bottom base is disposed on the lower beam between the upper and lower beams, and a self-balancing loading frame for accommodating a reinforced concrete specimen is disposed on the lower base. One end of the self-balancing loading frame is laterally connected to one end of a dynamic and static tension and compression servo actuator via a box-type distribution beam, and the other end of the dynamic and static tension and compression servo actuator is connected to the column. A servo actuator is slidably disposed on the upper beam. During testing, the servo actuator is fixed so that it is vertically located above the specimen in the self-balancing loading frame.

[0007] The self-balancing loading frame includes a box-type longitudinal beam, one end of which is connected to the box-type distribution beam. A specimen fixing structure and a steel bar anchoring beam are arranged in the box-type longitudinal beam. The specimen fixing structure consists of two box-type beams, 4 adjusting screws and pads, and is connected to the bottom base; there are two steel bar anchoring beams and they are respectively located on both sides of the specimen fixing structure. There are steel bar holes in the middle of the two steel bar anchoring beams and both ends are connected to the inner side of the box-type longitudinal beam. The steel bars at both ends of the reinforced concrete specimen respectively pass through the steel bar holes of the steel bar anchoring beam, and the first spoke force sensor is connected to the end of the steel bar close to the dynamic and static tension and compression servo actuator, and the second spoke force sensor and a pulling instrument for applying prestress are connected to the end of the steel bar away from the dynamic and static tension and compression servo actuator.

[0008] Furthermore: a connecting plate is provided on the bottom base, the connecting plate is provided with screw holes, and steel bar holes for the steel bars at both ends of the reinforced concrete specimen to pass through; the specimen fixing structure is movably connected to the connecting plate by adjusting the screw and the screw hole, and the reinforced concrete specimen is located between the specimen fixing structure and the connecting plate.

[0009] Furthermore: a pad is provided between the two box beams of the specimen fixing structure and the adjusting screw.

[0010] Furthermore: a clip-type anchor is provided on the side of the first spoke-type force sensor and the second spoke-type force sensor away from the reinforced concrete specimen. The clip is a cone formed by three steel sheets and is clamped on the force sensor.

[0011] Furthermore, an optical axis guide rail is also provided on the bottom base, and the optical axis guide rail fixes the self-balancing loading frame and the bottom base through a guide rail connector.

[0012] Furthermore, the self-balancing loading frame is connected to the dynamic and static tension and compression servo actuator via the box-type distribution beam and a universal ball joint.

[0013] Furthermore, pads of different modules are provided on the bottom base to ensure that the centroid of the steel bars in the test pieces of different sizes is always coaxial with the dynamic and static tension and compression servo actuator.

[0014] Furthermore, a lifting jack for adjusting the height of the dynamic and static tension and compression servo actuator is provided between the dynamic and static tension and compression servo actuator and the bottom beam.

[0015] Furthermore, the dynamic and static tension and compression servo actuator is slidably arranged on the column through the actuator fixing piece and the actuator connecting seat; and the servo actuator is slidably arranged on the upper beam through the actuator connecting plate.

[0016] The beneficial effects of the present invention are:

[0017] 1. The good integrity of this device enables the loading frame to achieve rigid self-balancing, which can realize the bond-slip performance test of steel bars and concrete under reciprocating loads at high stress levels, which is consistent with the actual stress and seismic load conditions.

[0018] 2. When testing the bond performance between rebar and concrete, this device overcomes the shortcomings of low rebar stress and no lateral pressure on concrete, while also achieving dynamic and static loading, more accurately reflecting the actual stress conditions at the rebar-concrete interface. The rebar fixing structure is also connected to the loading frame, further increasing the rigidity of the self-balancing frame. Under the action of force, the self-balancing loading frame will not experience planar warping or spatial misalignment, preventing deformation when subjected to stress and improving the overall stability of the device.

[0019] 3. This device can not only test the bond-slip properties of rebar and concrete under reciprocating loads, but also perform unidirectional pullout or pushout tests on the rebar and concrete. Pullout tests are performed by simply releasing all constraints on the side closest to the dynamic and static tension and compression servo actuators. Pushout tests are performed by installing the spoke-type force sensor and clip-type anchor near the end of the dynamic and static tension and compression servo actuators on the side of the rebar anchor beam in the self-balancing loading frame closest to the specimen, and releasing the constraints away from the dynamic and static tension and compression servo actuators.

[0020] 4. The specimen fixing structure of this device is connected to the connecting plate of the bottom base with an adjusting bolt, and is detachable on the side away from the dynamic and static tension and compression servo actuator. It can control the specifications of the specimen and prevent the specimen from displacement and damage. It not only fixes the specimen but also makes it easier to replace the specimen.

[0021] 5. This device is an easily disassembled, multifunctional self-balancing frame system with good stability, sufficient structural strength and good experimental application performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the overall main structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the overall top view of the structure of the present invention;

[0024] Figure 3 This is a schematic side view of the overall structure of the present invention;

[0025] Figure 4 This is a schematic diagram of the overall explosion structure of the present invention;

[0026] Figure 5 An exploded view of the external self-balancing frame and actuator related structures of the present invention;

[0027] Figure 6 This is an exploded view of the bottom base and self-balancing loading frame related structures of the present invention;

[0028] Figure 7 This is a schematic diagram of the self-balancing loading frame structure of the present invention;

[0029] Figure 8 This is a schematic side view of the bottom base structure of the present invention;

[0030] Figure 9 This is a schematic diagram of the main structure of the bottom base of the present invention;

[0031] Figure 10 This is a schematic diagram of the self-balancing loading frame structure for a unidirectional pull-out test according to the present invention;

[0032] Figure 11 This is a schematic diagram of the self-balancing loading frame structure for a unidirectional push-out test according to the present invention;

[0033] Figure 12 It is a schematic diagram of the structure of the test piece (ribbed steel bar) and spoke-type force sensor, clip-type anchor and other components of the present invention.

[0034] Among them: 1. Column; 2. Upper beam; 3. Bottom beam; 4. Bottom base; 5. Self-balancing loading frame; 6. Box-type distribution beam; 7. Dynamic and static tension and compression servo actuator; 8. Servo actuator; 9. Box-type longitudinal beam; 10. Specimen fixing structure; 11. Steel bar anchoring beam; 12. Guide rail connector; 13. First spoke-type force sensor; 14. Clip-type anchor; 15. Puller; 16. Adjusting screw; 17. Screw hole; 18. Steel bar hole; 19. Pad; 20. Actuator connecting plate; 21. Optical axis guide rail; 22. Connecting plate; 23. Second spoke-type force sensor; 24. Lifting jack; 25. Actuator fixing part; 26. Actuator connecting seat. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0036] Example 1 Test of the bond performance between high stress horizontal steel bars and lateral pressure concrete under reciprocating load

[0037] Reference Figure 1-4 , a bonding performance testing device between high stress horizontal steel bars and concrete under lateral pressure, consists of an external self-balancing frame and a self-balancing loading frame 5, the external self-balancing frame includes two columns 1, an upper beam 2 and a bottom beam 3 are arranged between the two columns 1, the upper beam 2 is located above the bottom beam 3; a bottom base 4 is arranged on the bottom beam 3 between the upper beam 2 and the bottom beam 3, the bottom base 4 is fixed to the bottom beam 3 by 10 screws, and a self-balancing loading frame 5 for accommodating reinforced concrete specimens is provided on the bottom base 4, one end of the self-balancing loading frame 5 is connected to the box-type distribution beam 6, the box-type distribution beam 6 is laterally connected to one end of the dynamic and static tension and compression servo actuator 7 through a universal ball joint, and the other end of the dynamic and static tension and compression servo actuator 7 is connected to the column 1; preferably, the dynamic and static tension and compression servo actuator 7 is slidably set on the column 1 through the actuator fixing member 25 and the actuator connecting seat 26; the servo actuator 8 is slidably set on the upper beam 2 through the actuator connecting plate 20. During the test, the servo actuator 8 is vertically located above the test piece of the self-balancing loading frame 5 .

[0038] Furthermore, a lifting jack 24 for adjusting the height of the dynamic and static tension and compression servo actuator 7 is provided between the dynamic and static tension and compression servo actuator 7 and the bottom beam 3 , and is used to adjust the height of the dynamic and static tension and compression servo actuator 7 to adapt to different specimen sizes.

[0039] Reference Figure 5-9 Specifically, the self-balancing loading frame 5 includes a box-type longitudinal beam 9, one end of which is connected to the box-type distribution beam 6, and a specimen fixing structure 10 and a steel bar anchoring beam 11 are arranged in the box-type longitudinal beam 9; a connecting plate 22 is provided on the bottom base 4, and a screw hole 17 and a steel bar hole 18 for the steel bars at both ends of the reinforced concrete specimen to pass through are provided on the connecting plate 22; the specimen fixing structure 10 is movably connected to the connecting plate 22 by means of an adjusting screw 16 that cooperates with the screw hole 17, and the reinforced concrete specimen is located between the specimen fixing structure 10 and the connecting plate 22. Preferably, a pad 19 is provided between the two beams of the specimen fixing structure 10 and the adjusting screw 16. Pads of different modules are also provided on the bottom base 4 to ensure that the centroid of the steel bars in specimens of different sizes is coaxial with the dynamic and static tension and compression servo actuator 7.

[0040] There are two steel bar anchoring beams 11, one located on each side of the specimen fixing structure 10. A steel bar hole is provided in the middle of each of the two steel bar fixing structures 11. Both ends of the two steel bar fixing structures 11 are connected to the inner side of the box longitudinal beam 9. The steel bars at both ends of the reinforced concrete specimen pass through the steel bar holes of the steel bar anchoring beams 11, and a first spoke-type force sensor 13 is connected to the end of the steel bar close to the dynamic and static tension and compression servo actuator 7. A second spoke-type force sensor 23 and a puller 15 are connected to the end of the steel bar away from the dynamic and static tension and compression servo actuator 7. Preferably, a clip-type anchor 14 is provided on the side of the first spoke-type force sensor 13 and the second spoke-type force sensor 23 away from the reinforced concrete specimen.

[0041] Furthermore, an optical axis guide rail 21 is provided on the bottom base 4 , and the optical axis guide rail 21 fixes the self-balancing loading frame 5 and the bottom base 4 via a guide rail connector 12 .

[0042] Working principle:

[0043] First, the bottom beam 3 and the upper beam 2 are fixed with bolts on both sides and installed on the column 1 to form the external self-balancing frame of the device. The actuator connecting plate 20 is fixed on the upper beam 2 and connected to the servo actuator 8. The distribution beam is connected to the servo actuator 8 and placed above the specimen to apply a lateral load to the concrete specimen during the test. The lifting jack 24 is installed on the bottom beam 3, and the actuator connecting seat 26 is installed on the upper position of the column 1 on one side. Figure 5 As shown, the actuator fixing part 25, the dynamic and static tension and compression servo actuator 7, the universal ball joint and the box-type distribution beam 6 are installed in sequence. Then, the bottom base 4 is fixed to the bottom beam 3 via 10 screws and the connecting plate 22 and the optical axis guide rail 21 are installed in sequence, and the optical axis guide rail connector 12 is installed on the guide rail. Then, the specimen ribbed steel bars are placed on the bottom base 4. According to the specifications and dimensions of the specimen, the height of the dynamic and static tension and compression servo actuator 7 is adjusted and fixed using the lifting jack 24 installed on the bottom beam 3. Connect the middle of the box longitudinal beam 9 to the guide rail connector 12, and connect the end to the box distribution beam 6. Finally, install the steel anchor beam 11 close to the dynamic and static tension and compression servo actuator, pass the steel bars of the specimen through the steel bar holes, and then let the steel bars on the other side pass through the steel bar holes of another steel anchor beam 11. Install the spoke force sensor and the clip-type anchor 14 in sequence, and install the pulling instrument at the end away from the dynamic and static tension and compression servo actuator 7. Tension the steel bars to reach the high stress level designed for the experiment. After tensioning is completed, fix the connecting plate 22 and the specimen fixing structure 10 by adjusting the screw 16. The specimen is located between the two. Apply a reciprocating load to the specimen according to the experimental plan for testing.

[0044] In this embodiment, a reinforced concrete specimen is placed on a bottom base 4. After pre-tensioning the steel bars at both ends of the specimen using through-hole jacks, the ends of the steel bars passing through the steel anchor beam 11 are secured using clip-type anchors 14. A first spoke-type force sensor 13 and a second spoke-type force sensor 23 are connected in series to the steel bars extending from both ends of the specimen. A puller 15 applies tension to the steel bars until a high stress level is reached. The steel bars are then secured by a specimen securing structure 10. A self-balancing loading frame 5 secures the specimen and connects it to a dynamic and static tension and compression servo actuator 7. Once the entire apparatus is stabilized, a reciprocating load is applied, and the servo actuator 8 applies lateral pressure to the reinforced concrete specimen, simulating the effect of the axial compression ratio on bond performance.

[0045] A dynamic and static tension and compression servo actuator 7 is connected to the box distribution beam 6 to apply load to the device, and a vertical servo actuator 8 applies lateral pressure to the specimen. Under the condition that the loading direction is always along the axial direction of the steel bar, the bond-slip performance test of the steel bar and concrete specimen under various loads is carried out.

[0046] The test device is easy to install. The box-type distribution beam 6 is connected to the universal ball joint and is connected to the dynamic and static tension and compression servo actuator 7. After adjustment, it can carry out pull-out tests under the unidirectional loading system of the original device and realize loading modes such as reciprocating load, sine wave load, square wave load, and triangular wave load.

[0047] The connecting plate 22 is connected to the bottom base 4 as a whole. The connecting plate 22 is connected to the specimen fixing structure 10 through four adjusting screws 16. A pad 19 is provided between the adjusting screws 16 and the two box beams of the specimen fixing structure 10. The specimen fixing structure 10 is used to constrain the horizontal displacement of the concrete part.

[0048] The internal self-balancing loading frame 5 applies pretension to the steel bars, while the servo actuator 8 applies lateral pressure to the concrete, achieving high stress levels in both the steel and concrete. The dynamic and static tension-compression servo actuator 7 applies reciprocating loads, more accurately simulating the bond-slip behavior of the steel and concrete at beam-column joints under seismic loads.

[0049] Example 2 Unidirectional pulling test

[0050] Reference Figure 10 When performing the pull-out test, it is only necessary to open all the constraints on the side close to the dynamic and static tension and compression servo actuator 7, and the remaining operations are the same as in Example 1 to achieve a unidirectional pull-out test.

[0051] Example 3 Unidirectional push-out test

[0052] Reference Figure 11When conducting a push-out test, the first spoke-type force sensor 13, the clip-type anchor 14 and other components of the steel bar anchoring beam 11 close to one end of the dynamic and static tension and compression servo actuator 7 are installed on the side close to the specimen, and the constraint away from the end of the dynamic and static tension and compression servo actuator 7 is opened. The remaining operations are the same as in Example 1, and a unidirectional push-out test can be achieved.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0054] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. Device for testing the bond performance between high stress horizontal steel bars and concrete subjected to lateral pressure, characterized by: The invention comprises an external self-balancing frame and a self-balancing loading frame (5), wherein the external self-balancing frame comprises two columns (1), an upper beam (2) and a bottom beam (3) are arranged between the two columns (1), the upper beam (2) is located above the bottom beam (3), a bottom base (4) is arranged on the bottom beam (3) between the upper beam (2) and the bottom beam (3), a self-balancing loading frame (5) for accommodating reinforced concrete test pieces is arranged on the bottom base (4), one end of the self-balancing loading frame (5) is horizontally connected to one end of a dynamic and static tension and compression servo actuator (7) through a box-type distribution beam (6), the other end of the dynamic and static tension and compression servo actuator (7) is connected to the column (1), and the dynamic and static tension and compression servo actuator (7) can move up and down at the column (1); a servo actuator (8) is slidably arranged on the upper beam (2), and during the test, the servo actuator (8) is vertically located above the reinforced concrete test piece in the internal self-balancing loading frame (5); The self-balancing loading frame (5) comprises two box-type longitudinal beams (9), one end of the box-type longitudinal beam (9) is connected to the box-type distribution beam (6), a specimen fixing structure (10) and a steel bar anchoring beam (11) are provided in the box-type longitudinal beam (9), and the specimen fixing structure (10) is connected to the bottom base (4); a steel bar hole is provided in the middle of the steel bar anchoring beam (11), and is respectively located on both sides of the specimen fixing structure (10), and both ends of the steel bar anchoring beam (11) are connected to the inner side of the box-type longitudinal beam (9), and the steel bars at both ends of the reinforced concrete specimen pass through the steel bar holes of the steel bar anchoring beams (11) on both sides, and a first spoke-type force sensor (13) is connected to one end of the steel bar close to the dynamic and static tension and compression servo actuator (7), and a second spoke-type force sensor (23) and a pulling instrument (15) are connected to one end of the steel bar away from the dynamic and static tension and compression servo actuator (7); An optical axis guide rail (21) is also provided on the bottom base (4), and the optical axis guide rail (21) fixes the self-balancing loading frame (5) and the bottom base (4) via a guide rail connector (12).

2. The bonding performance testing device between high stress horizontal steel bars and concrete subjected to lateral pressure according to claim 1 is characterized in that: A connecting plate (22) is provided on the bottom base (4), and screw holes (17) and steel bar holes (18) for the steel bars at both ends of the reinforced concrete specimen to pass through are provided on the connecting plate (22); the specimen fixing structure (10) is movably connected to the connecting plate (22) by adjusting the screw (16) to cooperate with the screw holes (17), and the reinforced concrete specimen is located between the specimen fixing structure (10) and the connecting plate (22).

3. The bonding performance testing device between high stress horizontal steel bars and concrete subjected to lateral pressure according to claim 2, characterized in that: The test piece fixing structure (10) comprises two box-shaped cross beams and four adjusting screws (16), and a pad (19) is provided between the box-shaped cross beams and the adjusting screws (16).

4. The device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to lateral pressure according to claim 1, characterized in that: A clip-type anchor (14) is provided on the side of the first spoke-type force sensor (13) and the second spoke-type force sensor (23) away from the reinforced concrete test piece.

5. The device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to lateral pressure according to claim 1, characterized in that: The box-type distribution beam (6) is connected to the dynamic and static tension and compression servo actuator (7) via a universal ball joint.

6. The device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to lateral pressure according to claim 1, characterized in that: Pads of different modules are also provided on the bottom base (4) to ensure that the centroid of the steel bars in test pieces of different sizes is always coaxial with the dynamic and static tension and compression servo actuator (7).

7. The device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to lateral pressure according to claim 1, characterized in that: A lifting jack (24) for adjusting the height of the dynamic and static tension and compression servo actuator (7) is provided between the dynamic and static tension and compression servo actuator (7) and the bottom beam (3).

8. The device for testing the bonding performance between high-stress horizontal steel bars and concrete subjected to lateral pressure according to claim 1, characterized in that: The dynamic and static tension and compression servo actuator (7) is slidably arranged on the column (1) through an actuator fixing member (25) and an actuator connecting seat (26); the servo actuator (8) is slidably arranged on the upper beam (2) through an actuator connecting plate (20).

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