Method for detecting porosity of multi-layer concrete filled steel tubular column

Abstract

The invention relates to the technical field of concrete filled steel tube detection, in particular to a porosity detection method for a multi-layer concrete filled steel tube column. During detection, radial electromagnetic waves and input power are obtained through the electromagnetic wave output and receiving device, and data support is provided for subsequent calculation. The difference between the radial electromagnetic wave input power measurement value and the output device output power reflects the energy loss of the electromagnetic wave in the propagation process and is related to the void ratio; the distance between the transmitting point and the receiving point affects the electromagnetic wave propagation path length and further affects energy attenuation; the number of layers of steel pipes, the total thickness of steel and the total thickness of concrete reflect the influence of structural composition on electromagnetic wave propagation; electromagnetic wave impedance of air, steel and concrete is related to magnetic conductivity and dielectric constants of materials, and the parameters jointly determine propagation characteristics of electromagnetic waves in different materials. Through comprehensive consideration of the parameters, the porosity of the multi-layer concrete filled steel tubular column can be accurately calculated, and a reliable basis is provided for engineering quality detection.

Description

Technical Field

[0001] The invention relates to the technical field of steel tube concrete detection, in particular to a method for detecting the void ratio of a multi-layer steel tube concrete column. Background Art

[0002] Steel tube concrete structure is a composite structure composed of steel tube and concrete, with excellent mechanical properties. The steel tube provides good axial bearing capacity and bending resistance, while concrete has obvious advantages in compression resistance, fire resistance and durability. The outer shell of the steel tube can effectively restrain the expansion of concrete and prevent it from cracking, thereby improving the overall strength and stability of the structure. This structural form has been widely used in high-rise buildings, large bridges, towers and other projects, especially for buildings with high requirements for earthquake resistance and wind pressure resistance.

[0003] The multi-layer steel tube concrete composite structure not only has the excellent performance of traditional steel tube concrete, but also further optimizes the mechanical properties, durability and construction process of the structure through the configuration of double-layer steel tubes. Specifically, the outer steel tube plays a role in protecting the inner steel tube and concrete, improving the seismic resistance and fire resistance. At the same time, the combination of multi-layer steel tubes makes the structure more advantageous when subjected to force and can effectively share external loads. In multi-layer steel tube concrete components, the design of inner and outer double-layer steel tubes can enhance the compression, bending and shear resistance of the components. As a load-bearing component, the outer steel tube mainly bears axial force and bending moment, while the inner steel tube works together with concrete to improve the stiffness and stability of the structure. Concrete not only provides excellent compressive resistance for the structure, but also constrains the deformation of the inner and outer steel tubes, improving the overall seismic resistance and fire resistance. The combined design of double-layer steel tubes effectively avoids the limitations of a single material and can better adapt to complex load conditions in the application of multi-story and high-rise buildings.

[0004] However, due to the existence of two parts of concrete, the inner core and the outer core, it is difficult to ensure the casting void ratio, and most of the existing monitoring methods are aimed at single-layer steel tube concrete components. There are relatively few methods for void ratio detection of steel tube concrete composite structural components with multiple layers of steel tubes, so it needs to be solved urgently. Summary of the invention

[0005] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides a method for detecting the void ratio of a multi-layer steel tube concrete column. The present invention can more accurately calculate the void ratio of a multi-layer steel tube concrete column.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for detecting the void ratio of a multi-layer steel tube concrete column comprises the following detection steps: S1, using an electromagnetic wave output device to vertically transmit electromagnetic waves to the steel tube concrete column, using an electromagnetic wave receiving device to receive the electromagnetic waves that pass through the steel tube concrete column along the diameter direction of the steel tube concrete column, and recording the electromagnetic waves as radial electromagnetic waves, while measuring the input power of the radial electromagnetic waves when they are input into the electromagnetic wave receiving device; S2. Substitute the acquired input power into the void ratio calculation formula to calculate the void ratio of the current steel tube concrete column; the void ratio calculation formula is as follows: ; ; ; ; In the formula, It represents the void ratio of the concrete-filled steel tube column; It represents the measured value of radial electromagnetic wave input power; Indicates the distance between the emission point of the electromagnetic wave output device and the receiving point of the electromagnetic wave receiving device; Indicates the output power of the electromagnetic wave output device; Indicates the number of steel pipe layers; Indicates the total thickness of steel that radial electromagnetic waves pass through; Indicates the total thickness of concrete that radial electromagnetic waves pass through; Represents the electromagnetic wave impedance of air; Indicates the magnetic permeability of air; represents the dielectric constant of air; Indicates the electromagnetic wave impedance of steel; Indicates the magnetic permeability of steel; Indicates the dielectric constant of steel; It represents the electromagnetic wave impedance of concrete; It represents the magnetic permeability of concrete; Represents the dielectric constant of concrete.

[0007] Compared with the prior art, the present invention has the following beneficial effects: During detection, the present invention obtains radial electromagnetic waves and input power through electromagnetic wave output and receiving devices to provide data support for subsequent calculations. and They represent the measured value of radial electromagnetic wave input power and the output power of the output device respectively. The difference between the two reflects the energy loss of electromagnetic waves during propagation and is related to the void ratio. It is the distance between the transmitting point and the receiving point, which affects the length of the electromagnetic wave propagation path and thus affects the energy attenuation; , and They represent the number of steel pipe layers, the total thickness of steel, and the total thickness of concrete, respectively, reflecting the influence of the structural composition on the propagation of electromagnetic waves; , , Its derived parameters characterize the electromagnetic wave impedance of air, steel and concrete respectively, which are related to the magnetic permeability and dielectric constant of the materials. These parameters jointly determine the propagation characteristics of electromagnetic waves in different materials. By comprehensively considering these parameters, the void ratio of multi-layer steel tube concrete columns can be accurately calculated, providing a reliable basis for engineering quality inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the electromagnetic wave propagation state in the present invention.

[0009] In the figure: 1. Electromagnetic wave output device; 2. Electromagnetic wave receiving device; 3. External steel pipe; 4. External core concrete; 5. Inner steel pipe; 6. Inner core concrete. DETAILED DESCRIPTION

[0010] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0011] See also Figure 1 , an electromagnetic wave output device 1 and an electromagnetic wave receiving device 2 are arranged on both sides of the steel tube concrete column. Then, the electromagnetic wave output device 1 is used to vertically transmit electromagnetic waves to the steel tube concrete column. Figure 1 The arrow in the figure points to the process of passing through the steel tube concrete column. The electromagnetic wave output by the electromagnetic wave output device 1 will pass through multiple layers of steel tubes and multiple layers of concrete and reach the electromagnetic wave receiving device 2. In the process of electromagnetic wave propagation, refraction and reflection will occur, and the radial electromagnetic wave propagating along the radial direction of the steel tube concrete column will be received by the electromagnetic wave receiving device 2, and the input power when entering the electromagnetic wave receiving device 2 will be measured at the same time for subsequent calculation.

[0012] The electromagnetic wave output device 1 will emit electromagnetic waves of a specific frequency, which are transmitted to the electromagnetic wave receiving device 2 through the steel tube concrete column. A part of the electromagnetic wave output by the electromagnetic wave output device 1 will be refracted on the surface of the outer steel tube 3, and the other part will pass through the outer steel tube 3 and enter the interior of the steel tube concrete column. Among them, the reflection coefficient of the refracted part of the electromagnetic wave is expressed as follows: ; Where: It represents the reflection coefficient of electromagnetic waves on the surface of steel pipe.

[0013] represents the electromagnetic wave impedance of air, The electromagnetic wave impedance of steel is determined by the electromagnetic wave characteristics, specifically: ; ; Where: It represents the magnetic permeability of air, in units of H / m, and is generally taken as 4π×10 -7 H / m.

[0014] It represents the dielectric constant of air, with the unit of F / m, and the general value is 1F / m.

[0015] It indicates the magnetic permeability of steel, in units of H / m, and is generally taken as 1.257×10 -3 H / m.

[0016] It represents the dielectric constant of steel, with the unit of F / m, and the general value is 30F / m.

[0017] From this we can get: Ω; Ω; ; The calculation result of the above formula shows that when the output electromagnetic wave is emitted to the surface of the outer steel pipe 3 , 49.7% of the electromagnetic wave is incident into the interior of the outer steel pipe 3 .

[0018] The attenuation rate of electromagnetic waves inside the outer steel tube 3 is 1.54×10 6 m -1 , that is, the electromagnetic wave propagates one meter, and its intensity weakens by 1.54×10 6 times. At this time, the electromagnetic wave is transmitted between the outer steel tube 3 and the outer core concrete 4. For vertical incidence (i.e., the electromagnetic wave propagates perpendicularly to the interface between the outer steel tube 3 and the outer core concrete 4), the reflection coefficient between the steel and the concrete is The specific expressions are as follows: ; ; Where: It represents the magnetic permeability of concrete, in units of H / m, and is generally taken as 4π×10 -7 H / m.

[0019] It represents the dielectric constant of concrete, with the unit of F / m, and the general value is 8F / m.

[0020] Substituting the above values ​​into the formula, we get the following results: ; ; The above calculation results show that when the electromagnetic waves are emitted to the concrete surface, 78% of the electromagnetic waves are incident into the interior of the outer core concrete 4.

[0021] Similarly, it can be seen that when the electromagnetic wave is incident from the outer core concrete 4 to the surface of the inner steel tube 5, 49.7% of the electromagnetic wave is incident into the inner steel tube 5. When the electromagnetic wave is incident from the inner steel tube 5 to the surface of the inner core concrete 6, 78% of the electromagnetic wave is incident into the inner core concrete 6. The electromagnetic wave continues to propagate along the radial direction of the steel tube concrete column and continues to attenuate according to the above ratio.

[0022] The attenuation rate of electromagnetic waves inside dry concrete is 2m -1 , that is, the electromagnetic wave propagates one meter and its intensity weakens by 2 times. The attenuation rate of electromagnetic waves in the air is basically 0. Therefore, based on the dimensions of the inner core concrete 6, outer core concrete 4, inner steel tube 5 and outer steel tube 3 of the multi-layer steel tube concrete column, combined with the input and output electromagnetic wave power, the porosity of the section can be effectively determined.

[0023] The void ratio calculation formula is as follows: ; ; in, Indicates the calculated value of the input power of the radial electromagnetic wave.

[0024] Embodiment 1: Calculated value of input power of radial electromagnetic wave: ; The void ratio can be obtained as follows: ; Embodiment 2: Calculated value of input power of radial electromagnetic wave: ; The void ratio can be obtained as follows: ; Embodiment 3: Calculated value of input power of radial electromagnetic wave: ; The void ratio can be obtained as follows: ; Embodiment 4: Calculated value of input power of radial electromagnetic wave: ; The void ratio can be obtained as follows: ; As shown in Table 1, the values ​​of parameters and the calculation results of void ratio in four embodiments of the present invention are shown.

[0025] Table 1 Specific values ​​and void ratio calculation results of the examples ; Based on the relative errors of the void ratio in Table 1, it can be seen that the technical solution of the present invention can calculate the void ratio of the multi-layer steel tube concrete column more accurately and quickly.

[0026] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for detecting the porosity of a multi-layered concrete-filled steel tube column, characterized in that: The following detection steps are included: S1. Use an electromagnetic wave output device to vertically transmit electromagnetic waves to the steel tube concrete column, use an electromagnetic wave receiving device to receive radial electromagnetic waves propagating along the diameter direction of the steel tube concrete column, and simultaneously measure the input power of the radial electromagnetic waves when they are input to the electromagnetic wave receiving device; S2. Substitute the acquired input power into the void ratio calculation formula to calculate the void ratio of the current steel tube concrete column; the void ratio calculation formula is as follows: ； ； ； ； In the formula, It represents the void ratio of the concrete-filled steel tube column; It represents the measured value of radial electromagnetic wave input power; Indicates the distance between the emission point of the electromagnetic wave output device and the receiving point of the electromagnetic wave receiving device; Indicates the output power of the electromagnetic wave output device; Indicates the number of steel pipe layers; Indicates the total thickness of steel that radial electromagnetic waves pass through; Indicates the total thickness of concrete that radial electromagnetic waves pass through; Represents the electromagnetic wave impedance of air; Indicates the magnetic permeability of air; represents the dielectric constant of air; Indicates the electromagnetic wave impedance of steel; Indicates the magnetic permeability of steel; Indicates the dielectric constant of steel; It represents the electromagnetic wave impedance of concrete; It represents the magnetic permeability of concrete; Represents the dielectric constant of concrete.

Images