A method for calculating the axial compressive bearing capacity of square steel tube concrete columns with circular cavities

Abstract

This invention belongs to the field of civil engineering and relates to a method for calculating the axial compressive bearing capacity of square steel tube concrete columns with circular cavities. This method can accurately calculate the axial compressive bearing capacity of square steel tube concrete columns with circular cavities. The calculation method includes the following steps: calculating the void ratio based on the volume of the cavity and the volume of the concrete; and, based on existing formulas for calculating the bearing capacity of steel tube concrete columns, considering the influence of the cavity on the column's bearing capacity, deriving a method for determining the bearing capacity of square steel tube concrete columns with circular cavities. This invention provides a simple and clear method for calculating the axial compressive bearing capacity of square steel tube concrete columns with circular cavities, offering theoretical support for this calculation.

Description

Technical Field

[0001] The invention belongs to the field of civil engineering and relates to a method for calculating the axial compressive bearing capacity of a square steel tube concrete column with a circular cavity. Background Art

[0002] In recent years, CFST components have been increasingly widely used in practical projects due to their advantages of high bearing capacity, good plasticity and toughness, strong fire resistance, good seismic performance and convenient construction. However, in the construction process, due to insufficient concrete pouring, loose vibration, stiffening ribs and internal partitions inside the steel tube, and unreasonable concrete maintenance in the later stage, cavities will inevitably be generated inside the CFST components, thus affecting the bearing capacity of the components.

[0003] At present, regarding the bearing capacity calculation method of steel tube concrete columns without cavities, domestic and foreign scholars have proposed different formulas based on the cross-sectional shape, but there is no definite bearing capacity calculation method for steel tube concrete columns with cavities. Summary of the invention

[0004] The purpose of the invention is to propose a method for calculating the axial compressive bearing capacity of a square steel tube concrete column with a circular cavity.

[0005] The present invention is achieved through the following technical solutions:

[0006] Step 1: Calculate the hollow ratio of the steel tube concrete column according to formula (1);

[0007]

[0008] Where: χ is the cavity ratio; d is the diameter of the circular cavity; h is the height of the circular cavity; B is the side length of the steel pipe, t is the thickness of the steel pipe; l is the column length;

[0009] Step 2: Calculate the axial compressive bearing capacity of the concrete-filled steel tube column with cavity according to formula (2):

[0010]

[0011] Where: μ is the calculation length coefficient, 1.0 for hinged ends, 0.5 for rigid ends, 0.7 for hinged ends and rigid ends; I sc is the moment of inertia of the column section; E sc is the axial compression elastic modulus;

[0012] Step 3: Calculate the axial compressive bearing capacity of the concrete-filled steel tube column with cavity according to formulas (3)-(5):

[0013]

[0014] when or hour:

[0015] N0=A c f ck [1+α(1-χ 2 )θ]+(1-χ) 2 A s f y (4)

[0016] when hour:

[0017]

[0018] Where: θ is the hoop coefficient of the steel tube concrete column; A s A is the cross-sectional area of ​​the steel pipe; c is the cross-sectional area of ​​the core concrete; f y is the yield strength of steel; f ck is the standard value of concrete axial compressive strength; α is a coefficient related to the concrete strength grade, 2.0 for concrete strength grade ≤ C50 and 1.8 for C55~C80; q w is the location of the cavity;

[0019] Step 4: Calculate the stability coefficient of concrete-filled steel tube under axial compression according to formula (8)

[0020]

[0021]

[0022]

[0023] Where: i sc is the radius of gyration; sc A is the column slenderness ratio; sc =A s +A c ;k E is the conversion factor of axial compression elastic modulus; is the normal slenderness ratio; is the stability coefficient;

[0024] Step 5: Calculate the axial compressive stability bearing capacity of the steel tube concrete with circular cavity according to formula (9):

[0025]

[0026] Step 6: Determine the bearing capacity of the steel tube concrete column with circular cavity according to formula (10).

[0027] N=min{N1,N2} (10)

[0028] Beneficial effects of the invention: The invention discloses a method for calculating the axial compressive bearing capacity of a square steel tube concrete column with a circular cavity, which can determine the stable bearing capacity of the axially compressed square steel tube concrete column with a circular cavity according to the cross-sectional parameters, material performance parameters and circular cavity size parameters of the steel tube concrete column. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A three-dimensional stereogram of a square steel tube concrete column with a circular cavity provided by an embodiment of the present invention;

[0030] Figure 2 Front elevation view of a square steel tube concrete column with a circular cavity according to an embodiment of the present invention;

[0031] Figure 3 A top view of a square steel tube concrete column with a circular cavity according to an embodiment of the present invention;

[0032] In the figure: 1. square steel pipe, 2. concrete, 3. circular cavity. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and by way of embodiments.

[0034] Example

[0035] A calculation method for the axial compressive bearing capacity of square steel tube concrete columns with circular cavities is taken as an example of a single-layer square steel tube concrete column of a youth activity center in a certain city. The material is Q355 square steel tube, C40 core concrete, the total height of the column is 5.4m, the column section is 400mm×400mm, the steel tube thickness is 10mm, the internal cavity is located in the center of the column, the diameter is 100mm, the height is 500mm, and the two ends of the column are hinged.

[0036] A method for calculating the axial compressive bearing capacity of a square steel tube concrete column with a circular cavity comprises the following steps:

[0037] Step 1: Calculate the hollow ratio of concrete-filled steel tube columns;

[0038]

[0039] Step 2: Calculate the axial compressive bearing capacity of concrete-filled steel tube columns with cavities:

[0040]

[0041]

[0042] Step 3: Calculate the axial compressive bearing capacity of the steel tube concrete column with the cavity located in the center:

[0043]

[0044] Step 4: Calculate the stability factor of concrete-filled steel tube under axial compression

[0045]

[0046]

[0047]

[0048] Step 5: Calculate the axial compressive stability of the concrete-filled steel tube with a circular cavity:

[0049]

[0050] Step 6: Determine the bearing capacity of CFST columns with circular cavities.

[0051] N=min{N1,N2}=19587.5KN

[0052] Although the specific calculation method of the present invention is described above in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Technical personnel in the relevant field should understand that various modifications or variations that can be made by technical personnel in the field without creative work on the basis of the design of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for calculating the bearing capacity of square steel tube concrete columns with circular cavities, characterized in that: The steps include: Step 1: Calculate the hollow ratio of the steel tube concrete column according to formula (1); Where: χ is the cavity ratio; d is the diameter of the circular cavity; h is the height of the circular cavity; B is the side length of the steel pipe, t is the thickness of the steel pipe; l is the column length; Step 2: Calculate the axial compressive bearing capacity of the concrete-filled steel tube column with cavity according to formula (2): Where: μ is the calculation length coefficient, 1.0 for hinged ends, 0.5 for rigid ends, 0.7 for hinged ends and rigid ends; I sc is the moment of inertia of the column section; E sc is the axial compression elastic modulus; Step 3: Calculate the axial compressive bearing capacity of the concrete-filled steel tube column with cavity according to formulas (3)-(5): when or hour: N0=A c f ck [1+α(1-x 2 )θ]+(1-x) 2 A s f y (4) when hour: Where: θ is the hoop coefficient of the steel tube concrete column; A s A is the cross-sectional area of ​​the steel pipe; c is the cross-sectional area of ​​the core concrete; f y is the yield strength of steel; f ck is the standard value of concrete axial compressive strength; α is a coefficient related to the concrete strength grade, 2.0 for concrete strength grade ≤ C50 and 1.8 for C55~C80; q w is the location of the cavity; Step 4: Calculate the stability coefficient of concrete-filled steel tube under axial compression according to formula (8) Where: i sc is the radius of gyration; sc A is the column slenderness ratio; sc =A s +A c ;k E is the conversion factor of axial compression elastic modulus; is the normal slenderness ratio; is the stability coefficient; Step 5: Calculate the axial compressive stability bearing capacity of the steel tube concrete with circular cavity according to formula (9): Step 6: Determine the bearing capacity of square steel tube concrete columns with circular cavities according to formula (10): N=min{N1,N2} (10).

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