Two-stage anchor for steel strand fatigue test

Abstract

The utility model provides a two -segment type anchor for steel strand fatigue test, including front anchor and the rear anchor of abutting behind the front anchor rear end, the front anchor includes the front anchor sleeve and the front anchor core in front anchor sleeve, the rear anchor includes the rear anchor sleeve and the rear anchor core in rear anchor sleeve, steel strand is clamped in front wire groove and rear wire groove, and the part of steel strand in front wire groove is covered with the protective sheath, the utility model can prevent the steel strand from breaking down because of radial shearing force in the process of steel strand fatigue test, causes the test failure.

Description

Technical Field

[0001] This utility model relates to the field of fatigue testing of steel strands, and in particular to a two-section anchor for fatigue testing of steel strands. Background Technology

[0002] Currently, most domestic fatigue performance tests of steel strands use anchor clamps to hold the steel strands. The two ends of the steel strand are clamped by anchors. The anchor includes an anchor sleeve and an anchor core, as shown in the "Anchor Clamping Plate for Fatigue Test of Steel Strand" with application number 2013107197923. The anchor core is surrounded by multiple clamping plates. Its inner wall has a cylindrical through hole and has annular teeth and annular grooves. Its outer wall is frustum-shaped. The inner wall of the anchor sleeve is also frustum-shaped. After the steel strand is clamped by the anchor core, it is placed in the anchor sleeve. An external force is applied to axially compress the anchor sleeve and the anchor core, thus clamping the steel strand tightly. The steel strand with anchors at both ends is then placed vertically on a steel strand fatigue testing machine. The machine has two connectors, one above the other, each with through holes. The two anchors pass through these holes, and a two-lobed limiting sleeve is installed at the step of each anchor. The outer diameter of the limiting sleeve is larger than the outer diameter of the through hole in the connector, thus firmly securing the steel strand and the two anchors between the two connectors. The lower connector is then subjected to frequent up-and-down movement driven by a hydraulic cylinder to perform tensile testing, thereby assessing the fatigue performance of the steel strand. In existing technology, to ensure the stable fixing of the steel strand, copper coated with diamond abrasive is typically wound around the ends of the steel strand to increase the friction between the steel strand and the anchors, and to protect the steel strand.

[0003] Theoretically, the above structure can perform fatigue tests on steel strands. However, in actual operation, because the steel strand fatigue testing machine is designed to test steel strands of different lengths and for easy assembly and disassembly, the upper connector is height-adjusted via lifting screws. Two vertical lifting screws are connected by a fixed crossbeam, and the upper connector is mounted on the fixed crossbeam. Although the lifting screws do not shift during the fatigue test, due to the screw's structural characteristics (its surface has threads), and the test involves reciprocating tension, these threads will experience slight wear. This can cause axial deviation in the steel strand during the reciprocating tension, rather than a vertical up-and-down movement. In this case, the end of the anchor furthest from the steel strand (such as the top of the lower anchor or the bottom of the upper anchor) will experience shear force with the steel strand, causing the steel strand to fracture at this location. Since the fracture is caused by shear force, according to GB / T5224-2003 "Steel Strands for Prestressed Concrete" standard, this test is invalid and therefore cannot correctly evaluate the fatigue performance of the steel strand.

[0004] Therefore, a new type of steel strand anchor is needed to adapt to the above situation, so that the test can be carried out smoothly and the test results that meet the standards can be obtained. Utility Model Content

[0005] The technical means adopted in this utility model are as follows: A two-section anchor for fatigue testing of steel strand includes a front anchor and a rear anchor adjacent to the rear end of the front anchor; The front anchor includes a front anchor sleeve and a front anchor core located within the front anchor sleeve; the front anchor core includes several front clamping pieces that are clustered together and can be pressed toward the axis, and the inner wall of the front anchor core forms a cylindrical front clamping groove, and the outer wall forms a frustum shape that is thicker at the back and thinner at the front; the inner wall of the front anchor sleeve has a front frustum hole that matches the outer wall of the front anchor core. The rear anchor includes a rear anchor sleeve and a rear anchor core located within the rear anchor sleeve. The front anchor core includes several rear clamping pieces that are clustered together and can be pressed towards the axis. The inner wall of the rear anchor core forms a cylindrical rear clamping groove. The rear end of the inner wall of the rear clamping groove has several annular teeth, and the front end has several parallel and spaced annular pressure relief grooves. The outer wall of the rear anchor core forms a frustum shape that is thicker at the rear and thinner at the front. The inner wall of the rear anchor sleeve has a rear frustum hole that matches the outer wall of the rear anchor core. The steel strand is clamped in the front clamping groove and the rear clamping groove, and the portion of the steel strand in the front clamping groove is covered with a protective sleeve.

[0006] Preferably, both the front anchor core and the rear anchor core are provided with O-ring mounting grooves at their rear ends.

[0007] Preferably, the outer wall of the rear anchor sleeve is cylindrical.

[0008] Preferably, the outer wall of the front anchor sleeve is cylindrical, and the outer wall of the front anchor sleeve is provided with a step for locking the limiting sleeve.

[0009] Preferably, the length of the rear anchor is less than the length of the front anchor.

[0010] Preferably, the protective sleeve is a PE sleeve.

[0011] Preferably, the portion of the steel strand located at the front end of the rear clamping groove is covered with the protective sleeve, and the protective sleeves for the steel strand located in the front clamping groove and the rear clamping groove are the same protective sleeve.

[0012] Preferably, the rear end of the front anchor sleeve has a groove, the inner diameter of which is adapted to the outer diameter of the rear anchor sleeve.

[0013] Preferably, the inner diameter of the front anchor core is the same as the inner diameter of the rear anchor core.

[0014] Preferably, the outer surface taper of the front anchor core is the same as that of the rear anchor core.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This utility model adopts a two-section anchorage. The rear anchorage plays the main role in fixing the steel strand, while the front anchorage plays the role in partially fixing the steel strand and also plays the role of buffering the axial displacement of the steel strand. The front and rear anchorages are tightly connected, and there is basically no radial shear force between the steel strand and the anchorage at the connection between the front and rear anchorages. This ensures that the breakage point during the test will not be at the connection between the front and rear anchorages. The steel strand is wrapped with a protective sleeve, which enhances the clamping force and buffers the radial movement of the steel strand.

[0016] 2. A sinkhole was set at the tail end of the front anchorage, and the front end of the rear anchorage was located in the sinkhole. The protective sleeve extended to the front end of the rear anchorage, which minimized the radial shear force at the front end of the rear anchorage and ensured the smooth progress of the test.

[0017] Based on the above reasons, this utility model can be widely promoted in the field of steel strand fatigue testing. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a two-section anchor for fatigue testing of steel strands under the present invention in use.

[0020] Figure 2 This is a cross-sectional view of a two-section anchor for fatigue testing of steel strand after installation at the mounting head.

[0021] Figure 3 This is a sectional view of the front anchor sleeve of this utility model.

[0022] Figure 4 This is a cross-sectional view of the front anchor core of this utility model.

[0023] Figure 5 This is a top view of the front anchor core of this utility model.

[0024] Figure 6 This is a sectional view of the rear anchor sleeve of this utility model.

[0025] Figure 7 This is a cross-sectional view of the rear anchor core of this utility model.

[0026] Figure 8 This is a top view of the rear anchor core of this utility model.

[0027] In the picture: 1. Front anchor; 11. Front anchor sleeve; 111. Front truncated cone hole; 112. Step; 113. Slot; 12. Front anchor core; 121. Front clamp; 122. Front clamp groove; 123. O-ring mounting groove; 2. Rear anchor; 21. Rear anchor sleeve; 211. Rear truncated cone hole; 22. Rear anchor core; 221. Rear clamping plate; 222. Rear clamping groove; 223. Annular tooth; 224. Annular pressure relief groove; 3. Steel strand; 4. Limiting sleeve; 5. Connector; 6. Protective cover. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figures 1-8 As shown in the figure, this specific embodiment discloses a two-section anchor for fatigue testing of steel strand, including a front anchor 1 and a rear anchor 2 adjacent to the rear end of the front anchor 1; The front anchor 1 includes a front anchor sleeve 11 and a front anchor core 12 located within the front anchor sleeve 11; the front anchor core 12 includes a plurality of (three in this specific embodiment) front clamping pieces 121 that are clustered together and can be pressed toward the axis, and the inner wall of the front anchor core 12 forms a cylindrical front clamping groove 122, and the outer wall forms a frustum shape that is thicker at the back and thinner at the front; the inner wall of the front anchor sleeve 11 has a front frustum hole 111 that matches the outer wall of the front anchor core 12; The rear anchor 2 includes a rear anchor sleeve 21 and a rear anchor core 22 located within the rear anchor sleeve 21. The front anchor core 22 includes several (three in this specific embodiment) rear clamping pieces 221 that are clustered together and can be pressed toward the axis. The inner wall of the rear anchor core 22 forms a cylindrical rear clamping groove 222. The rear clamping groove 222 has several annular teeth 223 at its rear end and several parallel and spaced annular pressure relief grooves 224 at its front end. The outer wall of the rear anchor core 22 forms a frustum shape that is thicker at the rear and thinner at the front. The inner wall of the rear anchor sleeve 21 has a rear frustum hole 211 that matches the outer wall of the rear anchor core 22. Both the front anchor core 12 and the rear anchor core 22 are provided with O-ring mounting grooves 123 at their rear ends. O-rings are installed in the O-ring mounting grooves 123 to easily assemble and fix the anchor cores.

[0030] The outer walls of both the rear anchor sleeve 21 and the front anchor sleeve 11 are cylindrical. The outer wall of the front anchor sleeve 11 has a step 112 for engaging the limiting sleeve 4. The length of the rear anchor 2 is less than the length of the front anchor 1. The outer surface taper of the front anchor core 12 is the same as that of the rear anchor core 22. The inner diameter of the front anchor core 12 is the same as that of the rear anchor core 22. The rear end of the front anchor sleeve 11 has a recess 113, the inner diameter of which matches the outer diameter of the rear anchor sleeve 21, and the front end of the rear anchor sleeve 21 is embedded in the recess 113.

[0031] The steel strand 3 is clamped in the front clamping groove 122 and the rear clamping groove 222, and the portion of the steel strand 3 in the front clamping groove 122 and the portion located at the front end of the rear clamping groove 222 are covered with a protective sleeve 6. The protective sleeve 6 is a PE sleeve.

[0032] In use: Protective sleeves 6 are fitted onto both ends of the steel strand 3 to be tested near its ends. Then, the front anchor core 12 is wrapped around the steel strand 3 and an O-ring is fitted on it. Next, the front anchor sleeve 11 is fitted over the front anchor core 12 and axially compressed to achieve a tight fit. Then, the rear anchor core 22 is wrapped around the end of the steel strand 3 and an O-ring is fitted on it. Next, the rear anchor sleeve 21 is fitted over the rear anchor core 22 and axially compressed to achieve a tight fit. The front end of the rear anchor sleeve 21 is embedded in the sinker 113, and the front anchor 1 and the rear anchor 2 are tightly attached. The two anchors are arranged symmetrically. The steel strand 3 with anchors is moved to the steel strand fatigue testing machine. The upper anchor is passed through the central through hole of the upper connector 5. Then, a two-lobed limiting sleeve 4 is put on the upper step 112, so that the upper anchor is suspended in the upper connector 5. Then, the screw of the steel strand fatigue testing machine drives the upper connector and steel strand 3 to move downward, so that the lower end of the steel strand 3 and the anchor at the lower end of the steel strand 3 pass through the top central through hole of the lower connector 5 and enter the connector 5. After adjusting the distance, the limiting sleeve 4 is put on the lower step 112. In this way, the steel wire rope 3 is axially limited between the two connectors 5. Then, the hydraulic cylinder at the bottom of the lower connector 5 is started to perform reciprocating tensile vibration in the vertical direction to conduct the test.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A two-section anchor for fatigue testing of steel strand, characterized in that, Includes a front anchorage and a rear anchorage immediately adjacent to the rear end of the front anchorage; The front anchor includes a front anchor sleeve and a front anchor core located within the front anchor sleeve; the front anchor core includes several front clamping pieces that are clustered together and can be pressed toward the axis, and the inner wall of the front anchor core forms a cylindrical front clamping groove, and the outer wall forms a frustum shape that is thicker at the back and thinner at the front; the inner wall of the front anchor sleeve has a front frustum hole that matches the outer wall of the front anchor core. The rear anchor includes a rear anchor sleeve and a rear anchor core located within the rear anchor sleeve. The front anchor core includes several rear clamping pieces that are clustered together and can be pressed towards the axis. The inner wall of the rear anchor core forms a cylindrical rear clamping groove. The rear end of the inner wall of the rear clamping groove has several annular teeth, and the front end has several parallel and spaced annular pressure relief grooves. The outer wall of the rear anchor core forms a frustum shape that is thicker at the rear and thinner at the front. The inner wall of the rear anchor sleeve has a rear frustum hole that matches the outer wall of the rear anchor core. The steel strand is clamped in the front clamping groove and the rear clamping groove, and the portion of the steel strand in the front clamping groove is covered with a protective sleeve.

2. The two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, Both the front anchor core and the rear anchor core are provided with O-ring mounting grooves at their rear ends.

3. The two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The outer wall of the rear anchor sleeve is cylindrical.

4. The two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The outer wall of the front anchor sleeve is cylindrical, and a step is provided on the outer wall of the front anchor sleeve to lock the limiting sleeve.

5. A two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The length of the rear anchor is less than the length of the front anchor.

6. A two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The protective sleeve is a PE sleeve.

7. A two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The portion of the steel strand located at the front end of the rear clamping groove is covered by the protective sleeve, and the protective sleeves for the steel strand located in the front clamping groove and the rear clamping groove are the same protective sleeve.

8. A two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The rear end of the front anchor sleeve has a groove, the inner diameter of which is adapted to the outer diameter of the rear anchor sleeve.

9. A two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The inner diameter of the front anchor core is the same as the inner diameter of the rear anchor core.

10. A two-section anchor for fatigue testing of steel strand according to claim 1, characterized in that, The outer surface taper of the front anchor core is the same as that of the rear anchor core.

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