Clamp device suitable for shear resistance test of connection joint of iron-based shape memory alloy plate and structure to be reinforced

Abstract

The utility model discloses a clamp device suitable for a shear resistance test of a connection node of an iron-based shape memory alloy plate and a to-be-reinforced structure, which comprises an upper clamping piece (1) and a lower clamping piece (2), one side of the upper clamping piece (1) is slotted, the lower clamping piece (2) is connected with a square plate (8), the upper clamping piece (1) and the lower clamping piece (2) are matched and connected through a nut (5) and a screw (7), and a triangular stiffening rib (9) is fixedly connected between the square plate (8) and the lower clamping piece (2). By adopting the clamp device, the influence of loading eccentricity on a node single shear test can be effectively reduced, and a connection interface is ensured to be in a pure shear state. The clamp device is easy to manufacture and convenient to operate, can be applied to a single shear test between a to-be-reinforced structure and an Fe-SMA plate in various connection modes such as structural adhesives and bolts, and can be repeatedly used. The method is simple, convenient and efficient.

Description

Technical Field

[0001] The utility model relates to a shear performance test method and tool, in particular to a fixture device suitable for testing the shear performance of the connection node between an iron-based shape memory alloy plate and a structure to be strengthened. Background Technique

[0002] Under the long-term internal and external physical or chemical actions, civil structures such as buildings and bridges may have problems such as aging, damage, and deformation. Moreover, during the service process, their uses may change, and the demand for loads may also increase over time. Therefore, in order to avoid local damage or even overall collapse of the structure and meet the application requirements, it is very necessary to repair or strengthen the existing structure in a timely manner. This problem is widespread globally and has currently become an important research direction in related fields. In the past few decades, scientific research personnel have conducted in-depth exploration on this, in order to improve the bearing capacity of the structure, improve its working performance, and extend the service life of the structure through different strengthening methods.

[0003] The existing structural strengthening methods at home and abroad mainly include the following: 1. Method of increasing cross-sectional area for strengthening; 2. Method of bonding steel plates for strengthening; 3. Method of bonding fiber composite materials for strengthening; 4. Method of external prestressing tendon for strengthening; 5. Method of prestressed fiber composite plate for strengthening; 6. Method of changing structural system for strengthening. Among them, the method of strengthening with prestressed carbon fiber reinforced polymer (CFRP) plates is a relatively advanced strengthening method at present. CFRP has been widely used in the field of civil structure strengthening with its excellent mechanical properties, fatigue properties, and durability, and has achieved remarkable strengthening effects. However, CFRP belongs to an anisotropic material, and its strength in the thickness direction is very low, which to a certain extent limits the exertion of its high-strength characteristics. In addition, the method of strengthening with prestressed CFRP plates needs to introduce prestress by means of heavy tensioning mechanical equipment such as jacks and oil pumps and complex anchors, which not only increases the construction difficulty and cost, but also makes its implementation process easily restricted by the operation space and the original structural form. Therefore, there is an urgent need in the industry to seek a new type of convenient, efficient and economical strengthening method.

[0004] Iron-based shape memory alloy (Fe-SMA) refers to an alloy that deforms under external force within a certain temperature range and can restore its original shape after heating and activation. This shape-recoverable property is the shape memory effect. If the Fe-SMA plate is fixed to the structure to be reinforced and then heated and activated, a very considerable recovery stress will be generated inside it due to the limited deformation, thereby achieving prestressed reinforcement of the structure. As a new type of intelligent material with broad application prospects, Fe-SMA has the advantages of low cost, high strength, good plasticity, high elastic modulus, and good hot and cold processing performance. The prestress loss caused by long-term effects such as fatigue and creep can be restored by reactivation, which can meet the growing performance and operation and maintenance needs of newly built and in-service civil structures.

[0005] In order to give full play to the strength advantage of Fe-SMA, the shear connection between Fe-SMA and the structure to be reinforced is crucial. When verifying the mechanical properties of the shear connection node between the Fe-SMA plate and the structure to be reinforced, especially when conducting a single shear tensile test on the connection node between the Fe-SMA plate and the concrete structure, there are problems such as the difficulty in clamping the concrete and the difficulty in ensuring that the connection interface is in a pure shear state. Summary of the invention

[0006] Purpose of the invention: The utility model provides a fixture device suitable for testing the mechanical properties of the connection node when the Fe-SMA plate is used to reinforce concrete. The fixture device is easy to manufacture and can be reused, effectively reducing the influence of the eccentric effect during the test, solving the problem that the mechanical properties of the connection node between the concrete structure and the reinforced structure are difficult to verify, and is suitable for other structures to be reinforced that are large in size and inconvenient to clamp. The device does not damage the structure to be reinforced, can be reused, and can ensure that the loading surface coincides with the connection interface, thereby effectively reducing the eccentric effect during the test and ensuring that the interface between the Fe-SMA plate and the concrete is in a pure shear state.

[0007] Technical solution: The fixture device for testing the shear resistance of the connection node between Fe-SMA and the structure to be reinforced includes an upper clamping piece with a slot on one side and a lower clamping piece connected to a square plate. The upper clamping piece and the lower clamping piece are connected and fixed by nuts and screws, and a triangular stiffening rib is fixedly connected between the square plate and the lower clamping piece.

[0008] Furthermore, the number of the triangular stiffening ribs is two.

[0009] Furthermore, the square plate and the lower clamping piece are perpendicular.

[0010] Furthermore, the square plate and the Fe-SMA plate are on the same plane.

[0011] Furthermore, the alloy plate is an iron-based shape memory alloy plate, a nickel-titanium-based shape memory alloy plate or a copper-based shape memory alloy plate.

[0012] Further, the structure to be strengthened is a combined structure of one or more of a concrete structure, a steel structure, a wood structure, and a masonry structure.

[0013] Further, the upper clamping piece is circular, oval or triangular. The lower clamping piece is circular, oval or triangular.

[0014] A method for testing the shear resistance performance of the connection node between the alloy plate and the structure to be strengthened by a fixture device includes the following steps:

[0015] Step S1: Pretreatment, grinding the surface of the base block of the structure to be strengthened, grinding the surface of the alloy plate, applying structural adhesive, pasting and assembling, and curing and maintaining.

[0016] Step S2: Positioning and drilling the upper and lower clamping pieces, and grooving the upper clamping piece; for the lower clamping piece, a square plate and two triangular stiffeners need to be welded, and the welding position of the square plate corresponds to the grooving depth of the upper clamping piece.

[0017] Step S3: Assembling the fixture device, installing the assembled specimen between the upper and lower clamping pieces, making the alloy plate just fit at the grooved place, and connecting the two clamping plates with screws.

[0018] Step S4: Installing the fixture device, using a testing machine to clamp the lower clamping piece of the fixture device and the Fe-SMA plate respectively, and then a single-shear tensile test can be carried out on the connection node of the specimen.

[0019] The alloy plate and the assembled reinforced structure are fixed to the fixture of the testing machine through the fixture device, so that the loading surface coincides with the adhesive layer interface, thus ensuring that the connection interface between the alloy plate and the concrete is in a pure shear state during the loading process. The grooving of the upper clamping piece is convenient to ensure that the connection interface with the alloy plate coincides with the loading surface after fixing the concrete block. The lower clamping piece includes a clamping plate, a square plate perpendicularly connected to the clamping plate, and two triangular stiffeners at the connection of the two. The square plate should be in the same plane as the alloy plate to reduce the eccentric effect when placing the fixture device on the testing machine for loading. The screw group includes a plurality of screws and corresponding nuts and gaskets, which are used to connect the four corners of the upper and lower clamping pieces. After installing the concrete and the alloy plate into the fixture device and then fixing it to the loading testing machine, a single-shear tensile test can be carried out.

[0020] Compared with the prior art, the utility model has the following beneficial effects:

[0021] The present utility model provides a testing method for single-shear tensile test applicable to the connection node between an alloy plate and a structure to be strengthened, which is simple to manufacture and convenient to operate. The fixture device consists of three major parts, and the materials for each part are easily obtainable, convenient to process, and reusable. Through reasonable design, on the basis of installing the assembled test piece onto the testing machine, the fixture device can ensure that the connection interface between the alloy plate and the structure to be strengthened is in a pure-shear state. The form of the fixture device is flexible and can be applied to mechanical property tests of various different structures, with a relatively wide application range. Description of the Drawings

[0022] Figure 1 is the structural schematic diagram of this embodiment;

[0023] Figure 2 is the schematic diagram of the upper clamping piece;

[0024] Figure 3 is the schematic diagram of the lower clamping piece. Specific Embodiment

[0025] To make the objectives, technical solutions, and advantages of the present utility model clearer, the technical solutions of the present utility model will be further described below.

[0026] Figures 1 - 3 is a fixture for the shear performance testing method of the connection node between a novel iron-based shape memory alloy plate and a structure to be strengthened in this embodiment, including an upper clamping piece 1 with a groove on one side, a lower clamping piece 2 connected with a square plate 8. The upper clamping piece 1 and the lower clamping piece 2 are connected by matching a nut 5 and a screw rod 7. A triangular stiffening rib 9 is fixedly connected between the square plate 8 and the lower clamping piece 2. The number of the triangular stiffening ribs 9 is two. The square plate 8 and the lower clamping piece 2 are perpendicular. The square plate 8 and the alloy plate are on the same plane. The alloy plate is an iron-based shape memory alloy plate Fe-SMA plate 3, a nickel-titanium-based shape memory alloy plate, or a copper-based shape memory alloy plate. The structure to be strengthened is a combination structure of one or several of a concrete block 4, a steel structure, a wood structure, and a masonry structure. The upper clamping piece 1 is circular, oval, or triangular. The lower clamping piece 2 is circular, oval, or triangular.

[0027] The implementation steps of the detection scheme are as follows:

[0028] Step S1: Pretreatment, such as grinding the surface of the base block of the structure to be strengthened, grinding the surface of the Fe-SMA plate, applying structural adhesive, pasting and assembling, and curing and maintaining.

[0029] Step s2: Positioning and drilling the upper and lower clamping pieces. Grooving treatment is carried out on the upper clamping piece 1, and the grooving depth needs to ensure the alignment of the center of the structure to be strengthened and the upper clamping piece 1. A square plate needs to be welded below the lower clamping piece, and the welding position of the square plate corresponds to the grooving depth of the upper clamping piece 1. Two triangular stiffening ribs are welded between the square plate and the lower clamping piece.

[0030] Step S3: Assemble the fixture device, install the assembled specimen between the upper and lower clamping pieces, so that the Fe-SMA plate just fits at the grooved place but is not tightly attached; connect the two clamping plates with screws and fix them on the outer sides of the two clamping plates with nuts, and add gaskets 6 to the nuts.

[0031] Step s4: Install the fixture device, use the testing machine to clamp the lower clamping piece 2 of the fixture device and the Fe-SMA plate respectively, and then the single-shear tensile test can be carried out on the connection node of the specimen.

[0032] The above are only the preferred embodiments of the present invention and do not impose any limitation on the present invention. Any person skilled in the art within the technical field, without departing from the technical solution of the present invention, makes any form of equivalent replacement or modification and other changes to the technical solution and technical content disclosed by the present invention, all of which belong to the content of not departing from the technical solution of the present invention and still fall within the protection scope of the present invention.

Claims

1. A fixture device applicable to the shear performance test of the connection node between an iron-based shape memory alloy plate and a structure to be strengthened, characterized in that: It includes an upper clamping piece (1) with a groove on one side, a lower clamping piece (2) connected with a square plate (8), and the upper clamping piece (1) and the lower clamping piece (2) are fixedly connected and fixed through the cooperation of a nut (5) and a screw rod (7). A triangular stiffening rib (9) is fixedly connected between the square plate (8) and the lower clamping piece (2).

2. The fixture device for the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be reinforced according to claim 1, characterized in that: The number of the triangular stiffening ribs (9) is two.

3. The fixture device for the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be strengthened according to claim 1, wherein: The square plate (8) and the lower clamping piece (2) are perpendicular.

4. The fixture device for the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be strengthened according to claim 1, characterized in that: The square plate (8) is in the same plane as the alloy plate.

5. The fixture device applicable to the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be strengthened according to claim 1, characterized in that: The alloy plate is an iron-based shape memory alloy plate, a nickel-titanium-based shape memory alloy plate or a copper-based shape memory alloy plate.

6. The fixture device for the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be strengthened according to claim 1, characterized in that: The structure to be strengthened is a combined structure of one or more of a concrete structure, a steel structure, a wood structure, and a masonry structure.

7. The fixture device for the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be reinforced according to claim 1, wherein: The upper clamping piece (1) is circular, oval or triangular.

8. The fixture device for the shear performance test of the connection node between the iron-based shape memory alloy plate and the structure to be strengthened according to claim 1, characterized in that: The lower clamping piece (2) is circular, oval or triangular.

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