Multidirectional adjustable concrete test fixture

Abstract

The utility model relates to the technical field of auxiliary clamps, in particular to a multidirectional adjustable concrete test clamp, which comprises a test piece, an upper clamp mechanism mounted at the upper end of the test piece and a lower clamp mechanism mounted at the lower end of the test piece, and the lower clamp mechanism and the upper clamp mechanism have the same composition structure and are oppositely arranged; the upper clamp mechanism comprises a horizontally-arranged connecting steel plate, three longitudinal clamping grooves evenly distributed in the left-right direction are formed in the connecting steel plate in a penetrating mode, and the three longitudinal clamping grooves are jointly connected with a plurality of clamping assemblies distributed in the front-back direction. The problems that according to an existing embedded type stretching device, the embedded depth of an extending object is not easy to master, and a concrete test piece is prone to cracking are solved, and the problem that according to an adhesive type stretching device, due to the fact that the bonding stress of the test piece and an end steel plate is insufficient, measurement of a whole curve cannot be conducted is solved. And an external clamping type stretching device has the problems that a test piece and a clamp are not tightly attached, the adaptability is poor, and cyclic loading cannot be carried out.

Description

TECHNICAL FIELD

[0001] The utility model relates to auxiliary fixture technical field, concretely is a kind of multidirectional adjustable concrete test fixture. BACKGROUND

[0002] Modern a large number of experimental research and engineering practice all show that concrete structure cracking is inevitable, especially under the action of earthquake. In order to improve the seismic performance of structure itself, prevent the catastrophic brittle failure of structure, the crack of concrete needs to be controlled within the range of allowable harmful degree. Therefore, a series of new concrete with high toughness and excellent crack width control ability are proposed, such as ECC. ECC is a kind of fiber reinforced cement-based composite material, which has the characteristics of high toughness and high damage tolerance.

[0003] Studies have shown that under the condition of enough stable loading process, many fiber concrete materials can show strain hardening characteristics, but under the action of direct tensile load, they show strain softening characteristics, so direct tensile test can verify whether fiber reinforced cement-based composite material has strain hardening characteristics. In addition, direct tensile test can also give tensile elastic modulus, initial cracking strength, initial cracking strain, ultimate tensile strength, ultimate tensile strain and ultimate crack width parameters. At present, the main direct tensile test devices are internal embedding type, pasting type and external clamping type three kinds of tensile devices. Internal embedding type tensile device needs to pre-embed reinforcing steel bars or bolts and other extension objects when pouring test piece, and the extension objects transmit tensile force to test piece during loading; pasting type tensile device is to roughen the end of test piece and local side surface first, then bond test piece and end steel plate together with epoxy resin glue, bond bonding steel plate and test piece side surface with steel sheet, and finally stretch test piece axially through steel plate; external clamping type tensile device is to stretch test piece axially by using left and right clamping arms to contact variable cross-section area of dumbbell type tensile test piece through clamp.

[0004] However, practice shows that the existing direct tensile test device has the following problems: first, the inner-buried tensile device, because the embedded depth of the extension is not easy to control, the embedded length is too long, which is easy to cause the extension to be deflected and affect the centering, and the embedded length is too short, which is easy to cause the debonding failure, and different types of studs will also cause the difference of the strength test value, at the same time, the local weakening effect of the stud end is easy to cause the concrete test piece to crack, thereby affecting the final result; second, the pasting tensile device, because the bonding stress between the test piece and the end steel plate is not enough, which will cause the final debonding stress to be less than the failure stress of the test piece, and the full curve measurement cannot be carried out; third, the outer clamping tensile device, because the clamp and the clamping arm are rigidly connected and cannot be adjusted, the contact surface of the clamp and the test piece is not dense, stress concentration occurs, thereby causing cracks at this position, and the outer clamping tensile device is only suitable for single size test piece, if the size of the test piece changes, the clamp needs to be redesigned, the adaptability is poor, in addition, the outer clamping tensile device can only carry out unidirectional tensile test, and cannot carry out cyclic loading and reverse pressure.

[0005] Therefore, it is necessary to invent a multi-directional adjustable concrete test clamp to solve the above problems. Practical new type content

[0006] The utility model discloses to solve the problem that the existing inner-buried tensile device is not easy to control the embedded depth of the extension and is easy to cause the concrete test piece to crack, the problem that the pasting tensile device is not easy to carry out full curve measurement due to the bonding stress between the test piece and the end steel plate is not enough, and the problem that the outer clamping tensile device is not easy to carry out cyclic loading due to the poor adaptability of the test piece and the clamp, provide a multi-directional adjustable concrete test clamp.

[0007] The utility model discloses the following technical scheme is realized:

[0008] A multi-directional adjustable concrete test clamp, comprising a test piece, further comprising an upper clamp mechanism installed on the upper end of the test piece, a lower clamp mechanism installed on the lower end of the test piece, the lower clamp mechanism and the upper clamp mechanism are the same in composition and are oppositely arranged;

[0009] The upper clamp mechanism comprises horizontally arranged connecting steel plates, three longitudinal clamping grooves evenly distributed along the left and right directions are formed through the connecting steel plates, a plurality of groups of clamping assemblies distributed along the front and back directions are connected to the three longitudinal clamping grooves, each group of clamping assemblies comprises two clamping arms, the two clamping arms are respectively connected to the longitudinal clamping grooves on the left part of the connecting steel plate and the longitudinal clamping grooves on the right part of the connecting steel plate, the two clamping arms of each group of clamping assemblies are arranged oppositely and have the same structure, the top of each clamping arm is fixed with a vertical screw rod, each clamping arm is fastened to the corresponding longitudinal clamping groove through the vertical screw rod and a nut I, a gasket I is clamped between the nut I and the connecting steel plate, a notch is formed in the bottom of each clamping arm, a chuck is installed in each notch, the working surface of each chuck is attached to the side surface of the corresponding test piece, a vertical clamping groove is formed through the side wall of each clamping arm, two vertical clamping grooves of each group of clamping assemblies are provided with a cross beam, one vertical screw rod is fixed to the left and right ends of each cross beam, the left and right ends of each cross beam are fastened to the corresponding vertical clamping groove through the vertical screw rod and a nut II, a screw hole is formed in the middle of the upper surface of each cross beam, a bolt I is threadedly connected to each screw hole, each cross beam is connected to the longitudinal clamping groove in the middle of the connecting steel plate through the bolt I, and the lower surface of the cross beam is attached to the upper surface of the test piece.

[0010] Further, a plurality of reserved holes are formed in each connecting steel plate, and the plurality of reserved holes are evenly distributed around the three longitudinal clamping grooves on the connecting steel plate.

[0011] Further, the connecting end of each chuck is in a semicircular arc shape, each notch is matched with the shape of the connecting end of the corresponding chuck, and the connecting end of each chuck is connected to the corresponding notch through a bolt II and a nut IV.

[0012] Further, two nuts III are sleeved on each bolt I, and the two nuts III are arranged on the upper surface and the lower surface of the connecting steel plate, respectively, and a gasket II is clamped between each nut III and the upper surface or the lower surface of the corresponding connecting steel plate.

[0013] Further, the vertical screw rod is a half-threaded screw rod.

[0014] The utility model discloses reasonable and reliable structure design, convenient to assemble and disassemble, not only can adapt to different thickness, height's test piece, can also adjust the clamping mode according to the specific shape of test piece, has ensured the uniformity of test piece stress in the test process, effectively avoided stress concentration phenomenon, improved the reliability and accuracy of test result, simultaneously, the adjustable design of this fixture has simplified the test preparation process, reduced the demand of the fixture that needs to be redesigned because of the size change of test piece, greatly improved the test efficiency, the fixture supports the continuous cyclic loading of tension and pressure, satisfies the experimental demand under the complex stress state, especially for the hysteresis performance research of ECC this fiber reinforced cement-based composite material, solved the problem that the existing technology external clamping type tension device can only carry out unidirectional tension test, cannot carry out cyclic loading and reverse pressurization, in addition, as a kind of new external clamping type tension device, this fixture avoids the problems that the existing internal embedding type tension device has the embedding depth of extension object that is not easy to control and can cause concrete test piece cracking and the problems that the sticking type tension device has the bonding stress of test piece and end steel plate, which leads to the measurement of full curve. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is the structure diagram of the utility model Figure 1 .

[0016] Figure 2 It is the structure diagram of the utility model Figure 2 .

[0017] Figure 3 It is the structure diagram of the utility model

[0018] Figure 4 It is the structure diagram of the utility model

[0019] Figure 5 It is the structure diagram of the utility model

[0020] Figure 6 It is the structure diagram of the utility model

[0021] Figure 7 It is the structure diagram of the utility model Figure 1 .

[0022] Figure 8 It is the structure diagram of the utility model Figure 2 .

[0023] In the figure: 1. Specimen; 2. Connecting steel plate; 3. Longitudinal groove; 4. Clamping arm; 5. Vertical screw; 6. Washer I; 7. Nut I; 8. Groove; 9. Clamp; 10. Vertical groove; 11. Crossbeam; 12. Horizontal screw; 13. Reserved hole; 14. Nut II; 15. Screw through hole; 16. Bolt I; 17. Nut III; 18. Washer II. Detailed Implementation

[0024] A multi-directional adjustable concrete testing fixture, as shown in the attached document. Figure 1 ~Appendix Figure 8 As shown, it includes specimen 1, an upper clamping mechanism installed on the upper end of specimen 1, and a lower clamping mechanism installed on the lower end of specimen 1. The lower clamping mechanism and the upper clamping mechanism have the same composition and are arranged opposite to each other.

[0025] The upper clamping mechanism includes a horizontally arranged connecting steel plate 2. Three longitudinal slots 3, evenly distributed along the left and right sides, are formed through the connecting steel plate 2. These three longitudinal slots 3 are connected to several sets of clamping components distributed along the front and back sides. Each set of clamping components includes two clamping arms 4, which are respectively connected to the longitudinal slots 3 on the left and right sides of the connecting steel plate 2. The two clamping arms 4 of each set of clamping components have the same structure and are arranged opposite each other. A vertical screw 5 is fixed to the top of each clamping arm 4. Each clamping arm 4 is fastened to the corresponding longitudinal slot 3 by the vertical screw 5 and a nut I7. A washer I6 is clamped between the nut I7 and the connecting steel plate 2. A slot 8 is formed at the bottom of each clamping arm 4. Each clamp 8 is equipped with a chuck 9. The working surface of each chuck 9 is in contact with the side surface of the corresponding specimen 1. Each clamp arm 4 has a vertical slot 10 through its side wall. A crossbeam 11 is provided between the two vertical slots 10 of each clamping assembly. A horizontal screw 12 is fixed to each of the left and right ends of each crossbeam 11. The left and right ends of each crossbeam 11 are fastened to the corresponding vertical slot 10 by the horizontal screw 12 and the nut II 14. A screw through hole 15 is opened in the middle of the upper surface of each crossbeam 11. A bolt I 16 is threaded into each screw through hole 15. Each crossbeam 11 is connected to the longitudinal slot 3 in the middle of the connecting steel plate 2 by the bolt I 16. The lower surface of the crossbeam 11 is in contact with the upper surface of the specimen 1.

[0026] In this invention, the upper clamping mechanism, in conjunction with the lower clamping mechanism, effectively clamps and fixes the specimen 1. The connecting steel plate 2 has three longitudinal slots 3, and the clamping arms 4 are fixed within the corresponding longitudinal slots 3 by vertical screws 5 and nuts I7. The clamping arms 4 can be adjusted in position by sliding along the corresponding longitudinal slots 3, thereby providing a more stable clamping of the specimen 1 and improving the flexibility of the fixture. Several sets of clamping components connected within the three longitudinal slots 3 work together to accommodate specimens 1 of different thicknesses, improving the adaptability of the fixture. This solves the problem that existing external clamping tensile devices are typically only suitable for specimens of a single size, requiring redesign of the fixture if the specimen size changes, resulting in poor adaptability. (Clamping arms 4, vertical slots) The combined structural design of 10, 11, 12, 14, 15, 16, and 16—including the crossbeam 11, the horizontal screw 12, the nut II, the screw through hole 15, and the bolt I—ensures that the lower surface of the crossbeam 11 of the upper clamping mechanism is in close contact with the upper surface of the specimen 1, and the upper surface of the crossbeam 11 of the lower clamping mechanism is in close contact with the lower surface of the specimen 1. This design ensures stability while also providing adjustability, allowing it to adapt to specimens 1 of different heights. This ensures that the specimen 1 is uniformly compressed during the test, thus achieving continuous cyclic loading of tension and compression. This meets the experimental requirements under complex stress states, particularly for the study of the hysteretic properties of fiber-reinforced cementitious composite materials like ECC. It solves the problem that existing external clamping tensile devices typically only perform uniaxial tensile tests and cannot perform cyclic loading or reverse compression.

[0027] Each connecting steel plate 2 has several reserved holes 13, and the reserved holes 13 are evenly distributed around the three longitudinal slots 3 on the connecting steel plate 2.

[0028] The reserved hole 13 of the upper clamping mechanism is designed to be fixed with the MTS electro-hydraulic servo actuator during operation, and the reserved hole 13 of the lower clamping mechanism is designed to be fixed with the universal testing machine.

[0029] Each chuck 9 has a semi-circular connecting end, and each slot 8 is adapted to the shape of the corresponding chuck 9 connecting end. Each chuck 9 connecting end is connected to the corresponding slot 8 by bolt II and nut IV.

[0030] This structural design allows the chuck 9 to be adjusted and rotated at a certain angle within the corresponding slot 8, thus facilitating the adaptation to different specifications of specimens 1 and the casting errors of specimens 1. It also ensures that the chuck 9 and specimen 1 are in close contact, avoiding stress concentration and ensuring uniform force distribution, thereby obtaining the ideal failure mode through testing and improving the accuracy and reliability of the test. At the same time, the chuck 9 is easy to disassemble, and for specimens 1 of different shapes, the test requirements can be met by replacing the chuck 9 with different shaped working surfaces, further improving the adaptability of this fixture.

[0031] Two nuts III 17 are sleeved on each bolt I 16, and the two nuts III 17 are arranged on the upper surface and the lower surface of the connecting steel plate 2 respectively, and a gasket II 18 is clamped between each nut III 17 and the upper surface or the lower surface of the corresponding connecting steel plate 2.

[0032] The structure design of the two nuts III 17 and the gasket II 18 can ensure the stable connection of the cross beam 11 and the connecting steel plate 2, prevent loosening, and thus improve the reliability of the concrete test.

[0033] The cross screw rod 12 is a half-thread screw rod.

[0034] The utility model will be further explained in detail through specific embodiments, and it should be noted that the utility model is not limited to the following embodiments.

[0035] In the embodiment, the test piece 1 is a dumbbell-shaped tensile test piece; the upper clamp mechanism and the lower clamp mechanism each include two groups of clamping assemblies.

[0036] During installation, first, the upper clamp mechanism is connected and fixed with the MTS electro-hydraulic servo actuator through the reserved hole 13 of the connecting steel plate 2 and the high-strength bolt, the lower clamp mechanism is connected and fixed with the universal testing machine through the reserved hole 13 of the connecting steel plate 2 and the high-strength bolt, the upper clamp mechanism and the lower clamp mechanism are arranged oppositely, each nut IV is loosened, the test piece 1 is placed in the middle part between the upper clamp mechanism and the lower clamp mechanism, the lower surface of the test piece 1 is attached to the upper surfaces of the two cross beams 11 of the lower clamp mechanism, the upper surfaces of the two cross beams 11 of the lower clamp mechanism are on the same horizontal plane, each nut I 7 is loosened, the position of each vertical screw rod 5 of each clamping arm 4 is adjusted by sliding in the corresponding longitudinal clamping groove 3, the four clamping arms 4 of the lower clamp mechanism are evenly distributed on the left and right sides of the lower end of the test piece 1, and the positions of the four clamping arms 4 of the upper clamp mechanism are corresponded to and arranged oppositely to the four clamping arms 4 of the lower clamp mechanism, then each nut I 7 is tightened, each clamping arm 4 is fixed in the corresponding longitudinal clamping groove 3 through the vertical screw rod 5 and the nut I 7, then each nut II 14 is loosened, the position of the cross screw rod 12 of each cross beam 11 is adjusted by sliding in the corresponding vertical clamping groove 10, the upper surfaces of the two cross beams 11 of the lower clamp mechanism are on the same horizontal plane and are tightly attached to the lower surface of the test piece 1, the lower surfaces of the two cross beams 11 of the upper clamp mechanism are on the same horizontal plane and are tightly attached to the upper surface of the test piece 1, each cross beam 11 is fixed in the corresponding vertical clamping groove 10 by tightening each nut III 17, then each chuck 9 is rotated and adjusted, the working surfaces of each chuck 9 are tightly attached to the variable cross section of the test piece 1, then each chuck 9 is fixed by tightening each nut IV, and thus the installation of the clamp is completed, and the subsequent loading test of the test piece 1 can be performed, and it should be noted that, before formal loading, in order to ensure that each cross beam 11 is attached to the test piece 1, pressure preloading needs to be performed.

[0037] In the implementation process, the material of the test piece 1 can be ECC, ultra-high performance concrete or other high-performance materials, but is not limited thereto.

[0038] In the description of the utility model, it is understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model.

[0039] Although the embodiments of the utility model have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the utility model, and the scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A multi-directional adjustable concrete test fixture, comprising a specimen (1), characterized in that: It also includes an upper clamping mechanism installed on the upper end of the specimen (1) and a lower clamping mechanism installed on the lower end of the specimen (1). The lower clamping mechanism and the upper clamping mechanism have the same composition structure and are arranged opposite to each other. The upper clamping mechanism includes a horizontally arranged connecting steel plate (2). Three longitudinal slots (3) are evenly distributed along the left and right sides through the connecting steel plate (2). The three longitudinal slots (3) are connected to several sets of clamping components distributed along the front and back. Each set of clamping components includes two clamping arms (4). The two clamping arms (4) are respectively connected to the longitudinal slots (3) on the left and right sides of the connecting steel plate (2). The two clamping arms (4) of each set of clamping components have the same structure and are arranged opposite to each other. A vertical screw (5) is fixed to the top of each clamping arm (4). Each clamping arm (4) is fastened to the corresponding longitudinal slot (3) by the vertical screw (5) and nut I (7). A gasket I (6) is clamped between the nut I (7) and the connecting steel plate (2). A slot (8) is opened at the bottom of each clamping arm (4). Each slot (8) Each clamp (4) has a chuck (9) installed inside, and the working surface of each chuck (9) is in contact with the side surface of the corresponding specimen (1). Each clamp arm (4) has a vertical slot (10) through its side wall. A crossbeam (11) is provided between the two vertical slots (10) of each clamping assembly. A horizontal screw (12) is fixed at each end of the left and right sides of each crossbeam (11). The left and right ends of each crossbeam (11) are connected by horizontal screws. The rod (12) and nut II (14) are fastened in the corresponding vertical slot (10). Each crossbeam (11) has a screw through hole (15) in the middle of its upper surface. Each screw through hole (15) is threaded with bolt I (16). Each crossbeam (11) is connected to the longitudinal slot (3) in the middle of the connecting steel plate (2) by bolt I (16), and the lower surface of the crossbeam (11) is attached to the upper surface of the specimen (1).

2. The multi-directional adjustable concrete testing fixture according to claim 1, characterized in that: Each connecting steel plate (2) has several reserved holes (13), and the reserved holes (13) are evenly distributed around the three longitudinal slots (3) on the connecting steel plate (2).

3. The multi-directional adjustable concrete testing fixture according to claim 1, characterized in that: The connecting end of each clamp (9) is semi-circular, and each slot (8) is adapted to the shape of the connecting end of the corresponding clamp (9). The connecting end of each clamp (9) is connected to the corresponding slot (8) by bolt II and nut IV.

4. The multi-directional adjustable concrete testing fixture according to claim 1, characterized in that: Each bolt I (16) is fitted with two nuts III (17), and the two nuts III (17) are respectively set on the upper and lower surfaces of the connecting steel plate (2). Each nut III (17) is sandwiched between the upper or lower surface of the corresponding connecting steel plate (2) and a washer II (18).

5. A multi-directional adjustable concrete testing fixture according to claim 1, characterized in that: The transverse screw (12) is a semi-threaded screw.

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