Negative Poisson's ratio reinforcement cage unit with low stress concentration and reinforced concrete

Abstract

The invention discloses a negative poisson ratio reinforcement cage unit with low stress concentration, and belongs to the technical field of reinforced concrete structures. A steel reinforcement framework unit is formed by binding steel reinforcements in x, y and z directions, the steel reinforcements are perpendicular to each other in pairs, the steel reinforcements in the x and z directions are steel reinforcements with sine curves, the sine curve equation is as follows: # imgabs0 #, in the formula, A is the amplitude of the sine curve, and B is the amplitude of the sine curve; l is half of the distance between the steel bars in the y direction. The steel reinforcement framework unit has a typical negative Poisson's ratio effect, stress concentration is effectively relieved, and the compression resistance and impact resistance of reinforced concrete are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of reinforced concrete structures, and in particular to a negative Poisson's ratio steel skeleton unit with low stress concentration and reinforced concrete. Background Art

[0002] Reinforced concrete structures in service environments face different types of impact loads, such as ships hitting bridge piers, airport runways bearing the impact of aircraft landings, and offshore platforms bearing the impact of waves. Concrete materials have low strength, high brittleness, and are prone to cracking. At present, research on improving the impact resistance of concrete mainly uses two technical means to enhance the strength of the concrete matrix and add tough materials such as steel fibers. In recent years, negative Poisson's ratio metamaterial structures have obvious advantages in compression resistance, shear resistance, and impact resistance. In the prior art, the basic structure of negative Poisson's ratio reinforced concrete / cement is a concave hexagon. Under the action of axial impact or compression load, the negative Poisson's ratio structural design causes the material to produce a lateral aggregation effect, which can locally strengthen the strength and stiffness of the reinforced concrete structure, thereby improving its overall compression resistance and impact resistance. However, the sharp corner design of the concave hexagon will produce stress concentration in the connection area, seriously reducing the size of the initial peak force, and not giving full play to the performance advantages of the negative Poisson's ratio structure. In addition, the concave hexagonal structure also has large differences in performance in the horizontal and vertical directions, and severe stress concentration leads to poor durability. At present, the reinforcement design of reinforced concrete used for load-bearing building structures mainly focuses on the reinforcement ratio and strength control, and pays less attention to the special form and arrangement of the steel bars. Therefore, there is an urgent need for a steel skeleton unit and reinforced concrete with low stress concentration and negative Poisson's ratio effect to maximize its compression and impact resistance. Summary of the invention

[0003] In view of the problems existing in the above prior art, the first aspect of the present invention provides a negative Poisson's ratio steel skeleton unit with low stress concentration. The second aspect of the present invention provides a negative Poisson's ratio reinforced concrete with low stress concentration. The steel skeleton unit of the present invention has a sinusoidal structure, which reduces the stress concentration in the sharp corner area of ​​the steel bar. When applied to the field of concrete construction, it can improve the stability and durability of the overall structure. It is specifically achieved through the following technologies.

[0004] A first aspect of the present invention provides a negative Poisson's ratio steel skeleton unit with low stress concentration, wherein the steel skeleton unit is formed by tying steel bars arranged in the x, y and z directions, wherein the steel bars have a sinusoidal steel bar, and the sinusoidal curve equation is as follows:

[0005] ;

[0006] Where A is the amplitude of the sine curve; L is the distance between the crests of adjacent steel bars arranged in the x, y or z direction.

[0007] The present invention proposes a new type of negative Poisson's ratio steel skeleton unit with low stress concentration, and the skeleton unit also has a negative Poisson's ratio effect. The present invention adopts steel bars with a sinusoidal structure, and prepares them into a steel skeleton unit containing steel bars arranged in the x, y and z directions (which can be divided into main bars and stirrups according to actual conditions) through a prefabricated skeleton method, and then compounds it with concrete to form reinforced concrete with low stress concentration and negative Poisson's ratio effect. When the concrete is subjected to axial impact or compression load, a lateral aggregation effect will occur, thereby improving its compression and impact resistance. The steel bars of the present invention creatively introduce a new type of sinusoidal structure, thereby avoiding the stress concentration phenomenon in the sharp corner area of ​​the steel skeleton unit, and improving the compression and impact resistance of the overall structure.

[0008] Furthermore, the ratio of A to L is (0.1-0.25):1.

[0009] Furthermore, the ratio of A to L is 0.158:1.

[0010] Specifically, A is 15 mm, and L is 95.2 mm.

[0011] Furthermore, the phase difference of the corresponding sine curves of the adjacent steel bar shapes arranged in the x-direction is π or 0; the phase difference of the corresponding sine curves of the adjacent steel bar shapes photographed in the y-direction is π or 0; the phase difference of the corresponding sine curves of the adjacent steel bar shapes arranged in the z-direction is π or 0.

[0012] Furthermore, when the phase difference of the sinusoidal curves corresponding to the shapes of adjacent steel bars arranged in the x, y, and z directions is π, the narrowest distance between adjacent steel bars is 0.1-0.25 times of L.

[0013] Furthermore, the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the x-direction are located is α, the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the y-direction are located is β, and the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the z-direction are located is γ, and α, β, γ=0-90°.

[0014] Furthermore, the binding points of the steel bars arranged in the x, y and z directions converge into one point.

[0015] A second aspect of the present invention provides a negative Poisson's ratio reinforced concrete with low stress concentration, which is composed of the above-mentioned negative Poisson's ratio reinforced concrete skeleton unit with low stress concentration poured with concrete.

[0016] Ordinary materials will have a necking phenomenon when subjected to longitudinal tensile stress, and their Poisson's ratio is positive. However, negative Poisson's ratio materials, i.e., tensile expansion materials, have the opposite deformation. The reinforced concrete of the present invention is obtained by compounding a steel skeleton unit with a negative Poisson's ratio effect with concrete. Therefore, the reinforced concrete of the present invention has a negative Poisson's ratio effect. When the negative Poisson's ratio concrete is stretched, it will expand laterally within the elastic range, and when it is compressed, it will shrink laterally. Therefore, the concrete of the present invention can greatly absorb external energy and has excellent compression resistance and impact resistance.

[0017] Optionally, the concrete raw materials include cement, sand, water-reducing agent and water, wherein the mass ratio of cement, sand and water is 1:2:0.5; and the amount of water-reducing agent is 0.5% of the mass of the cementitious material.

[0018] Since the reinforced concrete of the present invention also has a negative Poisson's ratio effect, according to the deformation characteristics of the negative Poisson's ratio, the reinforced concrete of the present invention will have a lateral aggregation effect when subjected to axial impact or compression load, thereby improving its compression and impact resistance. This helps to improve the earthquake resistance, wind resistance, explosion resistance and other capabilities of the reinforced concrete load-bearing body, while enhancing its safety, extending its service life, and reducing maintenance and repair costs.

[0019] Compared with the prior art, the present invention is beneficial in that:

[0020] 1. The steel skeleton unit of the present invention is made of steel bars with a sinusoidal structure, which not only has a negative Poisson's ratio effect, but also can effectively avoid the problem of severe stress concentration and improve its durability performance;

[0021] 2. The reinforced concrete of the present invention adopts a steel skeleton with low stress concentration and negative Poisson's ratio effect. Even if the simplest concrete ingredients are used, the maximum stress of the reinforced concrete can be significantly reduced; the durability and service life of the concrete are improved;

[0022] 3. The steel skeleton unit and reinforced concrete of the present invention help to improve the earthquake resistance, wind resistance, explosion resistance and other properties of the concrete load-bearing body, enhance the safety of concrete buildings, while extending the service life of concrete buildings and reducing the cost of maintaining and repairing concrete buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a steel bar skeleton unit provided in Examples 1-3 of the present invention.

[0024] Figure 2 It is the basic cell structure of the steel skeleton unit of Examples 1-3.

[0025] Figure 3This is a schematic diagram of the structure of the steel bar skeleton unit provided in Example 4.

[0026] Figure 4 This is the basic cell structure of the steel skeleton unit provided in Example 4.

[0027] Figure 5 for Figure 4 Example 4 provides orthographic projection views of the basic cell structure of the steel skeleton unit in the x, y and z directions (the orthographic projection views at the three angles have the same shape).

[0028] Figure 6 This is the basic cell structure of the steel skeleton unit of Comparative Example 1. DETAILED DESCRIPTION

[0029] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0030] The present invention exemplarily provides a negative Poisson's ratio steel skeleton unit with low stress concentration. The steel skeleton unit is formed by tying a plurality of steel bars in three arrangement directions of x, y and z. The steel bars in the three directions are all steel bars with sine curves. The equation of the sine curve is as follows:

[0031]

[0032] Where A is the amplitude of the sine curve; L is the distance between the crests of adjacent steel bars arranged in the y direction.

[0033] In some examples of the present invention, the ratio of A to L is (0.1-0.25):1.

[0034] In some examples of the present invention, the ratio of A to L is preferably 0.158:1.

[0035] Specifically, the A may be selected to be 15 mm, and the L may be correspondingly selected to be 95.2 mm.

[0036] In some examples of the present invention, the phase difference of the corresponding sine curves of adjacent steel bar shapes arranged in the x-direction is π or 0; the phase difference of the corresponding sine curves of adjacent steel bar shapes arranged in the y-direction is π or 0; the phase difference of the corresponding sine curves of adjacent steel bar shapes arranged in the z-direction is π or 0.

[0037] It can be understood that "phase difference of π" means that two adjacent steel bars are arranged in a state of wave crest to wave trough, and "phase difference of 0" means that two adjacent steel bars are arranged in a state of wave crest to wave crest.

[0038] In some examples of the present invention, when the phase difference of the sinusoidal curves corresponding to the shapes of adjacent steel bars arranged in the x, y, and z directions is π, the narrowest distance between adjacent steel bars is 0.1-0.25 times of L.

[0039] In some examples of the present invention, the angle between the planes containing the sinusoidal curves of adjacent steel bar shapes arranged in the x-direction is α, the angle between the planes containing the sinusoidal curves of adjacent steel bar shapes arranged in the y-direction is β, and the angle between the planes containing the sinusoidal curves of adjacent steel bar shapes arranged in the z-direction is γ; α, β, γ=0-90°.

[0040] It can be understood that, no matter the steel bars are arranged in the x, y, or z direction, when each steel bar is in the shape of a sine curve, its wave shape naturally forms a corresponding plane, α is the angle between the planes where two adjacent steel bars arranged in the x direction are located. The same is true for β and γ.

[0041] The present invention also exemplarily provides a negative Poisson's ratio reinforced concrete with low stress concentration, which is composed of the above-mentioned negative Poisson's ratio reinforced concrete skeleton unit with low stress concentration poured with concrete.

[0042] In some examples of the present invention, the concrete raw materials include cement, sand, water reducing agent and water. The specific amount of each raw material can be adjusted according to the site environment and actual needs.

[0043] Optionally, the mass ratio of cement, sand and water can be 1:2:0.5; and the amount of water reducing agent can be 0.5% of the mass of the cementitious material.

[0044] In some examples of the present invention, the cement can be selected from various common grades of cement, such as PO 42.5 ordinary Portland cement.

[0045] In some examples of the present invention, the fineness modulus of the sand may be 2.6, 2.8, and other common choices.

[0046] In some examples of the present invention, the water reducer used may be a polycarboxylic acid-based water reducer, a naphthalene-based water reducer, or the like.

[0047] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] In the following examples and comparative examples, the cement used is PO42.5 cement.

[0049] In the following examples and comparative examples, the sand used was medium sand with a fineness modulus of 2.6.

[0050] In the following examples and comparative examples, the water reducers used are all naphthalene-based water reducers.

[0051] In the following examples and comparative examples, the method for preparing reinforced concrete comprises the following steps:

[0052] After cement, sand, water reducing agent and water are mixed and stirred evenly, they are poured into a mold with a steel skeleton unit.

[0053] In the following examples and comparative examples, the concrete curing time is 28 days.

[0054] Example 1

[0055] The steel skeleton unit with low stress concentration provided in this embodiment is formed by tying steel bars in the x, y and x directions, and the position of each steel bar tying point is fixed. The steel bars arranged in the x, y and x directions are all steel bars with sine curves, and the equation of the sine curve is:

[0056] ,

[0057] And the value follows , that is, the ratio of A to L is 0.158:1;

[0058] The distribution and arrangement of steel bars refer to Figure 1 and 2 shown. Figure 1 is the three-dimensional structure diagram of the steel skeleton unit. Figure 2 for Figure 1 The basic cellular structure of the steel skeleton unit.

[0059] Depend on Figure 2 It can be seen that the phase difference between the sinusoidal curves of two adjacent steel bar shapes arranged in the x-direction is π, that is, the peak to the trough; the phase difference between the sinusoidal curves of two adjacent steel bar shapes arranged in the y-axis direction is 0; the phase difference between the sinusoidal curves corresponding to the two adjacent steel bars in the z-axis direction is also π.

[0060] The angle between the planes where the sinusoidal curves of adjacent steel bar shapes in the x direction provided in this embodiment are located is α, the angle between the planes where the sinusoidal curves of adjacent steel bar shapes in the y direction are located is β, and the angle between the planes where the sinusoidal curves of adjacent steel bar shapes in the z direction are located is γ; α, β, γ=0.

[0061] In this embodiment, in the x-direction, the narrowest distance between two adjacent arranged steel bars (the trough of one steel bar and the corresponding crest of the other steel bar) is 350 mm.

[0062] In this embodiment, in the y direction, the narrowest distance between two adjacent arranged steel bars (the trough of one steel bar and the corresponding crest of the other steel bar) is 350 mm.

[0063] In this embodiment, in the z direction, the narrowest distance between two adjacent arranged steel bars (the trough of one steel bar and the corresponding crest of the other steel bar) is 350 mm.

[0064] In this embodiment, the diameter of the steel bar itself is temporarily ignored. In practical applications, the narrowest distance mentioned above refers to the distance after deducting the diameter of the steel bar itself.

[0065] This embodiment also provides a reinforced concrete, which is composed of the above-mentioned steel skeleton unit poured with concrete; wherein the concrete includes cement, sand and water in a mass ratio of 1:1.91:0.59, and also includes a water reducing agent in an amount of 0.5% of the mass of cement.

[0066] Example 2

[0067] The steel bar structure of the steel bar skeleton unit with low stress concentration provided in this embodiment is basically the same as that in embodiment 1. The difference is that:

[0068] In this embodiment, in the x-direction, the narrowest distance between two arranged steel bars (frame tying points) is 175 mm;

[0069] In this embodiment, in the y direction, the narrowest distance between two arranged steel bars (framework binding points) is 175 mm. ;

[0070] In this embodiment, in the z direction, the narrowest distance between two arranged steel bars (framework binding points) is 175 mm.

[0071] This embodiment also provides a reinforced concrete, which is composed of the above-mentioned steel skeleton unit poured with concrete; wherein the concrete includes cement, sand and water in a mass ratio of 1:1.91:0.59, and also includes a water reducing agent in an amount of 0.5% of the mass of cement.

[0072] Example 3

[0073] The steel bar structure of the steel bar skeleton unit with low stress concentration provided in this embodiment is basically the same as that in embodiment 1. The difference is that:

[0074] In this embodiment, in the x-direction, the narrowest distance between two arranged steel bars (frame tying points) is 280 mm;

[0075] In this embodiment, in the y direction, the narrowest distance between two arranged steel bars (framework binding points) is 280 mm. ;

[0076] In this embodiment, in the z direction, the narrowest distance between two arranged steel bars (framework binding points) is 280 mm.

[0077] This embodiment also provides a reinforced concrete, which is composed of the above-mentioned steel skeleton unit poured with concrete; wherein the concrete includes cement, sand and water in a mass ratio of 1:1.91:0.59, and also includes a water reducing agent in an amount of 0.5% of the mass of cement.

[0078] Example 4

[0079] The structure of the negative Poisson's ratio steel skeleton unit provided in this embodiment is as follows Figure 3-5 As shown, compared with the steel bar skeleton unit of Example 1, the difference is that among the steel bars arranged in the x, y and x directions, there is a certain angle between the planes where two adjacent steel bars are located.

[0080] Specifically, the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the x direction are located is α, the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the y direction are located is β, and the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the z direction are located is γ, and α, β, γ=45°.

[0081] Example 5

[0082] The steel skeleton unit with low stress concentration provided in this embodiment is formed by tying steel bars in the x, y and x directions, and the position of each steel bar tying point is fixed. The steel bars arranged in the x, y and x directions are all steel bars with sine curves, and the equation of the sine curve is:

[0083] ;

[0084] And the value follows , that is, the ratio of A to L is 0.1:1. The distribution and arrangement of the steel bars in the x, y and x directions are similar to those in Example 1.

[0085] Example 6

[0086] The steel skeleton unit with low stress concentration provided in this embodiment is formed by tying steel bars in the x, y and x directions, and the position of each steel bar tying point is fixed. The steel bars arranged in the x, y and x directions are all steel bars with sine curves, and the equation of the sine curve is:

[0087] ;

[0088] And the value follows , that is, the ratio of A to L is 0.25:1. The distribution and arrangement of the steel bars in the x, y and x directions are similar to those in Example 1. Comparative Example 1

[0089] This comparative example is basically the same as Example 1, except that the steel skeleton unit is composed of a plurality of concave hexagonal cells connected in layers. Figure 6 shown.

[0090] That is, the steel bar skeleton unit of this comparative example has a sharp-angle design.

[0091] Application Examples

[0092] The reinforced concrete of Examples 1-4 and Comparative Example 1 was subjected to stress testing according to the method of "Standard for Test Methods of Mechanical Properties of Concrete" (GB / T50081). The test results are shown in Table 1 below.

[0093] According to the definition of Poisson's ratio , the Poisson's ratio of the reinforced concrete of Examples 1-4 and Comparative Example 1 was measured. The measurement results are described in Table 1 below.

[0094] Table 1 Stress test results of reinforced concrete of Examples 1-4 and Comparative Example 1

[0095]

[0096] As shown in Table 1, the strength of sin-curve reinforced concrete with different shape parameters is higher than that of concave hexagonal reinforced concrete. This is because sin-curve reinforced concrete effectively avoids stress concentration at sharp corners; under the action of axial compression load, the structural design of negative Poisson's ratio makes the concrete in a bidirectional compression state, effectively improving the overall bearing capacity of reinforced concrete. At the same time, sin-curve reinforced steel bars with different shape parameters can realize the regulation of mechanical properties such as Poisson's ratio and strength, and meet the application requirements of different load conditions.

[0097] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A negative Poisson's ratio steel skeleton unit with low stress concentration, characterized in that: The steel bar skeleton unit is formed by binding steel bars arranged in x, y and z directions perpendicular to each other. The shape of the steel bars conforms to the shape of a sine curve. The equation of the sine curve is as follows: ； Where A is the amplitude of the sine curve; L is the distance between the crest and the orthographic projection of the crest of adjacent steel bars arranged in the x, y or z direction.

2. The negative Poisson's ratio steel skeleton unit with low stress concentration according to claim 1, characterized in that: The ratio of A to L is (0.1-0.25):

1.

3. The negative Poisson's ratio steel skeleton unit with low stress concentration according to claim 1, characterized in that: The ratio of A to L is 0.158:

1.

4. The negative Poisson's ratio steel skeleton unit with low stress concentration according to claim 3, characterized in that: The A is 15 mm, and the L is 95.2 mm.

5. The steel bar skeleton unit with low stress concentration according to claim 1, characterized in that: The phase difference of the corresponding sine curves of the adjacent steel bar shapes arranged in the x direction is π or 0; the phase difference of the corresponding sine curves of the adjacent steel bar shapes arranged in the y direction is π or 0; the phase difference of the corresponding sine curves of the adjacent steel bar shapes arranged in the z direction is π or 0.

6. The negative Poisson's ratio steel skeleton unit with low stress concentration according to claim 5, characterized in that: When the phase difference of the sinusoidal curves corresponding to the shapes of adjacent steel bars arranged in the x, y, and z directions is π, the narrowest distance between adjacent steel bars is 0.1-0.25 times of L.

7. The negative Poisson's ratio steel skeleton unit with low stress concentration according to claim 5, characterized in that: The angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the x direction are located is α, the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the y direction are located is β, and the angle between the planes where the sinusoidal curves of adjacent steel bar shapes arranged in the z direction are located is γ; α, β, 0<γ≤90°.

8. The negative Poisson's ratio steel skeleton unit with low stress concentration according to claim 5, characterized in that: The binding points of the steel bars arranged in the x, y and z directions converge into one point.

9. A negative Poisson's ratio reinforced concrete with low stress concentration, characterized in that: It is composed of the steel frame unit described in any one of claims 1 to 8 poured with concrete.

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