Embedded steel pipe concrete column base structure and design method

Abstract

This invention belongs to the field of building engineering technology and discloses a construction and design method for an embedded steel-concrete composite column base. It includes concentric inner and outer steel columns, connected by several horizontal stiffening ribs distributed along the height of the column base. The outer steel column is fixedly connected to a web plate on the side facing the inner steel column. The outer steel column is divided into three sections from top to bottom: the top and bottom sections are bending-resistant sections, both with box-shaped cross-sections; the middle section is a shear-resistant section, with an open-corner cross-section. The corners between the bending-resistant section and the middle shear-resistant section are rounded. Foundation concrete is used to fill the space between the inner and outer steel columns. This invention provides differentiated bending and shear resistance at different column base heights, reduces the amount of column base material used, and saves construction costs. The open-corner cross-section of the shear-resistant section ensures column base quality and facilitates connection with the bending-resistant section.

Description

Technical Field

[0001] This invention belongs to the field of building engineering technology, specifically relating to a structure and design method for the column base of an embedded steel tube concrete column. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Concrete-filled steel tube columns are widely used in large-span structures and high-rise and super high-rise buildings due to their outstanding advantages such as high load-bearing capacity, good plasticity and toughness, and convenient construction.

[0004] As a crucial node connecting the upper steel-concrete composite column to the lower foundation, the embedment depth of the column base directly affects the structural fixation effect and force transmission reliability. According to the current "Technical Specification for Concrete Structures of High-Rise Buildings," to ensure the fixation performance of the column base, the embedment depth of the steel-concrete composite column should not be less than 2.5 times the outer diameter of the steel pipe. This means that the theoretical minimum embedment depth for large-diameter columns (such as steel pipe columns with a diameter of 3 meters) needs to reach 7.5 meters. This increases the amount of earthwork excavation for the foundation pit, the difficulty of support, the construction period, and the project cost.

[0005] To address the aforementioned technical problem of excessive column base embedment depth, existing technology discloses an embedded steel-concrete composite column base with boot beams. By fixing multiple boot beams circumferentially to the steel-concrete composite column, the bearing width of the embedded part is increased, thereby reducing the embedment depth.

[0006] The above solution can reduce the column base embedment depth by adding a boot beam, but it still has the following drawbacks: The aforementioned scheme enhances force transmission through a single structure such as a boot beam, but it fails to consider the significant differences in bending moment and shear force experienced at different heights of the column base. While adjusting parameters such as the boot beam's length, height, width, web thickness, and flange thickness to ensure the column base meets load-bearing requirements, this approach is prone to localized load-bearing capacity redundancy within the column base height range. It also makes it difficult to coordinate and optimize bending and shear performance, resulting in excessive material consumption in the case of large-diameter steel-concrete composite columns. Furthermore, although the aforementioned scheme discloses a method for calculating the embedment depth, this method does not consider the stress differences at different parts of the column base, making optimization for different locations impossible and further increasing material consumption. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a structure and design method for the column base of an embedded steel tube concrete column, which can solve the technical problem of excessive material consumption in the case of large-diameter steel tube concrete columns due to the use of a single structure to enhance force transmission.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In the first aspect, a column base structure for an embedded steel-concrete composite column is provided, including a foundation and a steel-concrete column, wherein the portion of the steel-concrete column within the foundation is the column base. The column base consists of concentric inner and outer steel columns, which are connected by several horizontal stiffening ribs distributed along the height of the column base. The outer steel column is fixedly connected to the web plate on the side facing the inner steel column. The outer steel column is divided into three sections from top to bottom. The top and bottom sections are bending resistance sections and are both box-shaped sections. The middle section is a shear resistance section, and the shear resistance section is a cross-shaped section with open corners. The corners between the bending section and the middle shear section are rounded, and the space between the inner and outer steel columns is filled with foundation concrete.

[0009] Preferably, the width of the box-shaped cross-section is , The diameter of the cross-section of the steel pipe column or inner steel column 1.5 to 2 times; the width of the steel flange with a cross-shaped cross section is , Cross-sectional width 0.5 to 0.8 times.

[0010] Preferably, the spacing of the horizontal stiffeners in the bending zone is 500-1000 mm, and the spacing of the horizontal stiffeners in the shear zone is 1000-1500 mm.

[0011] Preferably, the horizontal stiffening ribs are provided with multiple casting holes and multiple venting holes, and the web, flanges and surfaces of the outer steel column and the inner steel column are all provided with studs.

[0012] Secondly, a design method for the aforementioned embedded steel-concrete composite column base structure is provided, the specific steps of which include: Step S1: Obtain the design information of the steel pipe columns in the superstructure and determine the initial embedment depth control value of the column base. , =0.6 times the standard allowable value ; Step S2: Set the design conditions for the column base; Step S3: Verify whether the design conditions of the column base in step S2 can meet the anchorage bearing capacity; if not, return to step S2 to reset until the design conditions of the column base meet the requirements. Step S4: Calculate the column base embedment depth to meet the stress requirements. Height of the bending section And the embedment depth of the column base to meet the rigid fixing requirements. Height of the bending section , like ＞ or ＞ Then return to step S2 until... ≤ ,and ≤ ; Step S5: Determine the final embedment depth of the column base. Height of the bending section and shear section height ,as follows: ; ; .

[0013] Preferably, the design information for the steel pipe column includes cross-sectional dimensions, material performance parameters, and design internal forces, wherein the cross-sectional dimensions include the diameter of the inner steel column or steel pipe column. Steel pipe column wall thickness Distance from the top of the foundation to the inflection point of the steel pipe column Material performance parameters include the material strength of the steel pipe column or internal steel column; design internal forces include bending moment. axial force Shear force .

[0014] Preferably, the design conditions for the column base include the strength grade of the foundation concrete, the strength grade of the external steel column, and the width of the flexural section. Shear section width .

[0015] Preferably, in step S3: ; In the formula: A c1 - Cross-sectional area of ​​the inner steel column; A c2 - Cross-sectional area of ​​the external steel column.

[0016] Preferably, the column base embedment depth in step S4 meets the stress requirements. Calculate using the following formula: ; ; In the formula: Design value of compressive strength of foundation 1 concrete; The thickness of the protective layer at the top of the column base; At this point, the height of the bending section is Solve using the following formula: .

[0017] Preferably, the column base embedment depth in step S4 meets the rigid fixing requirements. , Pick , The plastic bending capacity of a column is given by the following formula: ; ; At this point, the height of the bending section is Solve using the following formula: .

[0018] Compared with the prior art, the advantages and positive effects of this invention are: This invention involves concentrically connecting an outer steel column to an inner steel column. The outer steel column comprises a bending section at the top and bottom and a shear section in the middle. The bending sections have box-shaped cross-sections, while the shear sections have open-corner cross-sections. The outer steel column provides differentiated bending and shear resistance at different heights. Compared to traditional techniques that rely on a single structure to enhance force transmission, resulting in design redundancy within the column base height range and a large amount of material used for the column base, this invention ensures both shear and bending resistance while reducing the amount of material used for the column base, thus saving construction costs. Furthermore, the open-corner cross-section of the shear section in this invention ensures shear bearing capacity while facilitating the smooth pouring of concrete within the annular space between the inner and outer steel columns, thus guaranteeing concrete density, strength, and column base quality. Finally, the open-corner cross-section of the shear section also facilitates connection with the bending section. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a front view of an embedded steel-concrete composite column base structure according to Embodiment 1 or Embodiment 2 of the present invention; Figure 2 This is from Embodiment 1 or Embodiment 2 of the present invention. Figure 1 aa cross-sectional view; Figure 3 This is from Embodiment 1 or Embodiment 2 of the present invention. Figure 1 bb cross-section diagram; Figure 4This is a force-bearing principle diagram of the column base structure in Embodiment 1 or Embodiment 2 of the present invention; Figure 5 This is a flowchart of the design method of Embodiment 2 of the present invention; In the picture: 1. Foundation; 2. Steel pipe column; 3. Column base; 4. Inner steel column; 5. Outer steel column; 6. Horizontal stiffening rib; 61. Pouring hole; 62. Vent hole; 7. Bending section; 8. Shear section; 9. Stud; 10. Fixed steel frame. Detailed Implementation

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] The present invention will now be described in detail with reference to the accompanying drawings.

[0023] Example 1 This embodiment discloses a column base structure for an embedded steel-concrete composite column, such as... Figure 1 As shown, the structure includes a foundation 1 and steel pipe columns 2. The portion of the steel pipe columns 2 within the foundation 1 forms the column base 3. The column base 3 includes concentric inner steel columns 4 and outer steel columns 5. In this embodiment, the concentric arrangement of the inner steel columns 4 and outer steel columns 5 helps to achieve uniform load transfer and overall structural stability. The inner steel columns 4 and outer steel columns 5 are connected by several horizontal stiffening ribs 6, which are distributed along the height direction of the column base. Their function is to enhance the cooperative working ability between the inner steel columns 4 and outer steel columns 5, prevent local buckling, and improve the overall stiffness of the column base.

[0024] like Figure 2 , Figure 3 As shown, the web plate is fixedly connected to the side of the outer steel column facing the inner steel column, which aims to enhance the local stiffness and load-bearing capacity of the outer steel column and optimize the load transfer path from the outer steel column to the inner steel column and the internal concrete. Figure 1 As shown, the outer steel column 5 is divided into three sections from top to bottom, with the top and bottom sections forming the bending resistance zone 7, as shown below. Figure 2 As shown, the bending section 7 consists entirely of box-shaped sections. Box-shaped sections have high bending stiffness and can effectively resist the large bending moments that the column base may experience near the top surface of the foundation and at the bottom of the embedment. The middle section is the shear section 8, as shown... Figure 3As shown, the outer steel column 5 of the shear section 8 has an open cross-shaped cross section at the corners. While ensuring shear bearing capacity, its open corner structure facilitates the smooth pouring of concrete within the annular space between the inner and outer steel columns, thus ensuring the density and strength of the concrete. The corners between the top or bottom bending section 7 and the middle shear section 8 adopt a rounded transition. The rounded transition ensures a smooth transfer of load between different cross-sectional forms, avoids stress concentration caused by abrupt changes in cross-section, and improves the fatigue performance and overall durability of the structural members. It is understood that foundation concrete is also filled between the inner steel column 4 and the outer steel column 5.

[0025] In this embodiment, based on the differences in bending moment and shear force at different heights of the column base, the outer steel column 5 can provide differentiated bending and shear resistance at different heights of the column base. Specifically, the top and bottom sections of the outer steel column have box-shaped sections, which can effectively resist bending moments, while the middle section adopts a cross-shaped section with open corners to optimize concrete casting while ensuring shear resistance. In this embodiment, the bending resistance section 7 and the shear resistance section 8 have different lengths.

[0026] In traditional construction design, force transmission is enhanced by a single structure such as a boot beam, and the strength of the column base is increased by increasing the cross-sectional area or length of the boot beam, thereby reducing the embedment depth of the column base. Although increasing the cross-sectional area or length of the boot beam ensures that the boot beam meets the minimum bearing pressure requirements within the column base height range, it inevitably creates design redundancy within the column base height range, resulting in a large amount of column base material used.

[0027] In this embodiment, an outer steel column 5 is concentrically installed on the outside of the inner steel column 4. Based on the stress characteristics of the column base 3, the outer steel column 5 is divided into a top section, a middle section, and a bottom section. Different cross-sectional forms are used in the top, middle, and bottom sections to achieve synergistic optimization of bending and shear resistance. This segmented and differentiated design allows the column base 3 to provide the most suitable load-bearing capacity in different areas according to the actual stress distribution. This avoids the redundancy of load-bearing capacity in some areas caused by using a single support beam to reinforce the column base in traditional solutions, which results in a large amount of material used for the column base.

[0028] In this embodiment, the shear-resistant section 8 in the middle section adopts a cross-shaped cross section with open corners, instead of a box-shaped cross section with a smaller cross-sectional area. This is because it is necessary to consider not only the shear resistance provided by the outer steel column 5 in the middle section, but also the convenience of connecting the shear-resistant section 8 with the bending sections 7 in the top and bottom sections. If the shear-resistant section 8 adopts a box-shaped cross section with a smaller cross-sectional area, a variable-diameter section is required between the bending section 7 and the shear-resistant section 8 to ensure the continuity of the outer steel column 5, which would be difficult to manufacture. In addition, if a box-shaped cross section and a variable-diameter section are used to form a closed space between the inner and outer steel columns, it would be difficult to fill the space between the inner steel column 4 and the outer steel column 5 with concrete when pouring concrete between them. The open corner structure design of the shear section 8 not only ensures the shear performance of the outer steel column 5 in the middle position, but also facilitates the connection between the bending section 7 and the shear section 8, ensuring the continuity of the outer steel column 5. It also improves the fluidity and density of concrete between the outer steel column 5 and the inner steel column 4, ensuring the filling quality of concrete in the annular space between the inner and outer steel columns.

[0029] like Figure 2 As shown, the outer steel column 5 has a box-shaped cross-section at the top or bottom. In this embodiment, the width of the box-shaped cross-section is... , The diameter of the cross-section of steel pipe column 2 or inner steel column 3. The size range is 1.5 to 2 times that of the column base 3. This size range is to ensure that the bending section 7 within the foundation 1 has sufficient bending stiffness and bearing capacity, so as to effectively distribute the bending moment and axial force transmitted by the upper steel pipe column to the foundation, while avoiding excessive cross-sectional size that would lead to material waste or difficulty in connecting with the foundation.

[0030] like Figure 3 As shown, the outer steel column 5 has an open cruciform cross-section in the middle shear section 8, and the width of the steel flange of the cruciform cross-section is... , The width of section 7 in the bending section The size range of 0.5 to 0.8 times that of the shear zone is designed to ensure that the shear zone 8 provides the necessary shear bearing capacity.

[0031] In this embodiment, the horizontal stiffening ribs 6 are arranged differently in different functional sections (such as the bending section and the shear section). Specifically, in order to enhance the connection between the inner steel column and the outer steel column and the overall stress performance, the spacing of the horizontal stiffening ribs 6 in the bending section 7 is 500-1000mm, and the spacing of the horizontal stiffening ribs 6 in the shear section 8 is 1000-1500mm.

[0032] It should be noted that within the bending section 7, the spacing of the horizontal stiffeners 6 ranges from 500 to 1000 mm. This closer spacing provides stronger lateral restraint, ensuring that the bending section 7 can withstand larger bending moments and shear forces, effectively suppressing local buckling of the inner and outer steel columns, and enhancing the compressive performance of the concrete. This ensures that the inner and outer steel columns and the concrete in the bending section 7 can work closely together to resist external loads. In the shear section 8, which primarily bears shear forces and has lower stiffness requirements than the bending section 7, the horizontal stiffeners 6 are spaced further apart. This avoids the adverse effects of excessively dense horizontal stiffeners on the concrete compaction and also prevents excessive material consumption. This differentiated stiffener spacing allows the entire column base to achieve efficient composite action in different stress zones, ensuring the coordinated stress and integrity of the inner and outer steel columns, thereby improving the overall load-bearing capacity and seismic performance of the column base.

[0033] like Figure 3 As shown, within the shear section 8, the horizontal stiffening rib 6 is fixedly connected to the flange plate of the shear section 8; the shear section 8 has an open corner cross section, and the horizontal stiffening rib 6 within the shear section 8 has an octagonal structure.

[0034] like Figure 2 , Figure 3 As shown, in order to ensure that the concrete can smoothly enter the cavity formed by the outer steel column 5 and the inner steel column 4, and to ensure the continuity, density and strength of the concrete pouring, multiple pouring holes 61 and multiple venting holes 62 are provided on the horizontal stiffening rib 6. The diameter of the pouring hole should not be less than 200 mm, and the diameter of the venting hole should not be less than 25 mm.

[0035] In this embodiment, pouring holes 61 are provided at the center and on the circumferential plane of the horizontal stiffening ribs 6. The pouring holes are used to ensure that the concrete passes smoothly between the horizontal stiffening ribs 6 and avoid blockage. Venting holes 62 are provided at the corners of the horizontal stiffening ribs 6 in the bending section 7 to discharge air that may be trapped during the pouring process, promote the flow of concrete in the cavity, prevent the formation of voids or air bubbles, and improve the density of the concrete.

[0036] like Figures 1 to 3 As shown, in order to ensure the integrity and anchoring reliability of the column base 3 and the foundation 1, and to ensure that the load can be effectively transferred from the column base 3 to the foundation 1, studs 9 are provided (usually by welding) on ​​the web, flange and inner steel column 4 of the outer steel column 5.

[0037] In this embodiment, the diameter of the stud 9 can be selected as 19mm or 22mm according to design requirements to provide sufficient shear resistance. The spacing of the studs 9 ranges from 150 to 200mm to ensure uniform and sufficient anchoring force within a limited area.

[0038] like Figure 1 As shown, in this embodiment, the bottom of the column base 3 is fixed with a fixed steel frame 10 to further reduce the foundation height.

[0039] In this embodiment, all components of the column base 3 are steel structures, which can be fabricated in the factory and transported to the site for fixed installation. The structure is simple and easy to construct.

[0040] Example 2 This embodiment discloses a design method for the column base structure of an embedded steel-concrete composite column. It performs design verification on the column base structure of an embedded steel-concrete composite column disclosed in Embodiment 1, including embedment depth, bending zone height, shear depth, etc. Figure 5 As shown, the specific steps include: Step S1: Obtain the design information of the steel pipe column 2 in the superstructure and determine the initial embedment depth control value of the column base 3. This step aims to provide the necessary foundational data for subsequent column base design. The principle for determining the initial embedment depth control value d0 of the column base is: first, determine the allowable value of the column base embedment depth according to current specifications. And take 0.6 times this allowable value as the initial burial depth control value, that is... =0.6 .

[0041] Step S2: Set the design conditions for column base 3. This step is used to clarify the various parameters of column base 3 and provide adjustable data for subsequent verification of bearing capacity.

[0042] Step S3: Verify whether the design conditions of column base 3 in step S2 can meet the anchorage bearing capacity; if not, return to step S2 to readjust the design conditions of column base 3 until the requirements are met.

[0043] Step S4: Calculate the column base embedment depth to meet the stress requirements. and the height of the bending section ,like Greater than Then return to step S2 to readjust the design conditions of column base 3 and return to step 3 to recalculate until the conditions are met. Less than or equal to Simultaneously calculate the embedment depth of the column base to meet the rigid fixing requirements. and bending section height ,like Greater than If so, return to step S2 to readjust the design conditions of column base 3 and return to step 3 to recalculate. Less than or equal to ,and Less than or equal to Then proceed to the next step.

[0044] Step S5: Determine the final embedment depth of the column base. Height of the bending section and shear section height Calculate using the following formula: ; ; .

[0045] In this embodiment, the design information for the steel pipe column 2 in step S1 includes cross-sectional dimensions, material performance parameters, and design internal forces. The cross-sectional dimensions include the diameter of the inner steel column 4 (actually the portion of the steel pipe column 2 within the foundation). 2 steel pipe column wall thickness The distance from the top of foundation 1 to the inflection point of steel pipe column 2 Material performance parameters include the material strength of steel pipe column 2 or inner steel column 4; design internal forces include bending moment. axial force Shear force Among them, axial force Reaction force at the base of the column They are equal, but in opposite directions.

[0046] inner steel column diameter This refers to the cross-sectional diameter of the internal steel column in a concrete-filled steel tube column, and the wall thickness of the steel tube column. This refers to the thickness of the steel tube portion in a concrete-filled steel tube column; the wall thickness of the steel tube column. The load-bearing capacity and local stability of the steel pipe are determined by both the material strength and the strength of the steel pipe itself. The distance from the top of foundation 1 to the inflection point of steel pipe column 2. This refers to the distance from the top of foundation 1 to the point where the bending moment of steel pipe column 2 is zero under load. This distance is usually obtained through overall structural analysis or by making reasonable assumptions based on the structural system and load conditions.

[0047] Material strength refers to the mechanical properties of the steel used in steel pipe columns, such as yield strength and tensile strength. It can be selected according to the steel grade specified in the design specifications (such as Q235, Q345, etc.) or determined according to the material test report in the actual project.

[0048] The design internal force refers to the bending moment generated inside the cross section of the steel pipe column 2 under various load combinations. axial force Shear force These internal forces are the main basis for the design and verification of steel column sections. They are usually obtained through structural analysis software (such as finite element analysis software) or derived from load codes and structural mechanics principles.

[0049] In this embodiment, the column base design conditions in step S2 include the concrete strength grade of foundation 1, the strength grade of outer steel column 5, and the cross-sectional width of bending section 7. 8-section width of the shear resistance zone Thickness of the web of the outer steel column outer steel column flange thickness (Used to calculate the cross-sectional area of ​​the outer steel column).

[0050] In this embodiment, since the anchorage performance of column base 3 is directly proportional to the anchorage bearing capacity of the component, if the embedment depth is optimized to be reduced, the anchorage bearing capacity of the component needs to be increased. This is because optimizing the embedment depth involves reducing the depth of the column base embedded in the foundation while meeting structural safety and functional requirements. Increasing the anchorage bearing capacity of the component can compensate for the loss of anchorage capacity due to the reduced embedment depth. In this embodiment, when the embedment depth is reduced to 0.6 times the original specification value, in order to maintain the same anchorage performance, theoretically, the bearing capacity of the anchoring component needs to be increased to 1 / 0.6 times the original value, i.e., 1.7 times. Therefore, the anchorage bearing capacity... It needs to be increased to the original anchorage bearing capacity. 1 / 0.6 = 1.7 times. The bearing capacity can be obtained by multiplying the area by the material strength. In this embodiment, the inner and outer steel columns use the same type of steel, so the anchorage bearing capacity is... With the original anchorage bearing capacity The simplified formula for expressing this is as follows: ; In the formula: A c1 - Cross-sectional area of ​​the inner steel column; A c2 - Cross-sectional area of ​​the external steel column.

[0051] The force diagram of column base 3 in foundation 1 in this embodiment is as follows: Figure 4 As shown, the embedment depth of the column base that meets the stress requirements in step S4 is... Calculated according to the following principles: ; ; ; In the formula: The design value of the compressive strength of the base concrete.

[0052] Solving the above formula, we get: ; Considering the installation of a protective layer at the top of column base 3, the calculated values... Correction: ; In the formula: The thickness of the protective layer at the top of column base 3; At this time, the height of the bending section 7 is Solve using the following formula: .

[0053] It should be noted that the embedment depth of the column base must meet the load-bearing requirements. This refers to the minimum embedment depth required for a column base to maintain structural integrity and load-bearing capacity when subjected to design internal forces such as bending moment, axial force, and shear force transmitted from the superstructure.

[0054] The column base embedment depth that meets the rigid fixing requirements in step S4 Calculated according to the following principles: To meet the requirements of rigid fixation Pick , For the plastic bending capacity of a column, the following formula applies: ; ; ; ; Solving the above formula, we get: ; Similarly, considering the installation of a protective layer at the top of column base 3, the calculated values... Correction: ; At this time, the height of the bending section 7 is Solve using the following formula: .

[0055] It should be noted that the embedment depth of the column base to meet the rigid fixing requirements During the design process, to ensure that the connection between column base 3 and foundation 1 provides sufficient rotational stiffness, and to ensure that the column base still provides sufficient rigid restraint when the column reaches its ultimate bearing capacity, thus preventing premature failure or excessive rotation of the column base. Under seismic loading or large lateral force loading, it can significantly enhance the overall overturning resistance and seismic performance of the structure, ensuring that the structure maintains good deformation control even when it reaches its ultimate bearing capacity, thereby improving the structure's safety reserve and service life.

[0056] In this embodiment, if the result in step S4 does not meet the requirements, the process returns to step S2 to adjust the width of the bending section 7. At the same time, according to and The relationship is compared with the diameter of the inner steel column section 3. .

[0057] In this embodiment, the range and height of each section are optimized through design verification to ensure that each section meets the load-bearing requirements, avoid redundant design, and reduce material usage.

[0058] In a specific example of a construction design method: Assuming the outer diameter of the steel-concrete composite column =3000mm, wall thickness is 60mm, total column height is 45m, the concrete strength grade inside the pipe is C60, the steel material of the inner steel column and steel pipe is Q420, the concrete strength grade of foundation 1 is C30, the steel material of the outer steel column of foundation 1 is Q420, and the column base is designed according to the traditional column base design according to the specification, the column base embedment depth is... The value of 2.5D, or 7.5m, results in high costs for single column base pit support, dewatering, and foundation. The design method described in this embodiment optimizes the column base embedment depth. The design process is as follows: First, obtain the design information of the steel columns in the superstructure, which will reveal the outer diameter of the concrete-filled steel tube column. =3000mm, wall thickness t =60mm, height from the top of foundation 1 to the inflection point =45m, the concrete strength grade inside the pipe is C60, and the standard value of concrete compressive strength is... f ck =38.5N / mm 2 The cross-sectional area of ​​the inner steel column and steel pipe A sc = 554176mm 2 ， The steel used for the inner steel columns and pipes is Q420, and the tensile and bending strength of the steel is [not specified]. f =320N / mm 2 shear strength f v =185N / mm 2 Yield strength is f y =380N / mm 2 Bending moment design value =167970 kN·m, shear force design value =3733KN. Determine the initial burial depth control value for the column base. =0.6 .

[0059] Next, the design conditions for the column base are set, with the concrete strength grade of foundation 1 set to C30 and the design value of concrete compressive strength set to... fc =14.3 N / mm 2 Standard value of concrete compressive strength f ck =20.1 N / mm 2 Width of the bending section of the outer steel column B =5000mm, width of the shear section of the outer steel column B 1=2500mm, thickness of the web of the outer steel column t w =40mm, outer steel column flange thickness t f =60mm, length of the web of the outer steel column on one side between the inner and outer steel columns. h 1=690mm, thickness of the protective layer at the top of the outer steel column foundation c =300mm.

[0060] Verify whether the anchorage bearing capacity of the column base meets the requirements: ; ; ; The above calculation results meet the requirements. Calculate the column base embedment depth to meet the stress requirements. Height of the bending section The specific solution is as follows: ; ; ; ; The above calculation results meet the requirements, and the embedment depth of the column base that meets the rigid fixing requirements can be calculated. and bending section height The specific solution is as follows: ; ; ; ; ; ; ; In the formula: The steel content of the concrete-filled steel tube member. For concrete-filled steel tube members, the hoop coefficient is... B, CThe coefficient representing the influence of cross-sectional shape on the hoop effect is taken according to the "Technical Specification for Concrete-Concrete Composite Steel Tube Structures". This refers to the standard value of the compressive strength of concrete-filled steel tubing. This is the plastic section modulus of a bending member.

[0061] ; ; ; ; The calculation results meet the requirements, and the final dimension of the column base embedment depth can be determined: Column base embedment depth: ; Height of the bending section: Round down to 1750. mm ; Shear section height: .

[0062] Through the above design, the embedment depth of this column base is 4.5m, which is 40% less than the standard value of 7.5m (2.5D). This can significantly reduce the foundation size, foundation pit excavation and support costs, reduce construction difficulty and have significant economic benefits.

[0063] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A column base structure for an embedded steel-concrete composite column, comprising a foundation and a steel-concrete composite column, wherein the portion of the steel-concrete composite column within the foundation constitutes the column base; characterized in that, The column base includes concentric inner steel columns and outer steel columns, and the inner steel columns and outer steel columns are connected by a number of horizontal stiffening ribs, which are distributed along the height direction of the column base. The outer steel column is fixedly connected to the web plate on the side facing the inner steel column. The outer steel column is divided into three sections from top to bottom. The top and bottom sections are bending resistance sections and are both box-shaped sections. The middle section is a shear resistance section and the shear resistance section is a cross-shaped section with open corners. The corners between the bending section and the middle shear section are rounded, and the space between the inner and outer steel columns is filled with foundation concrete.

2. The embedded steel-concrete composite column base structure as described in claim 1, characterized in that, The width of the box-shaped cross-section is , The diameter of the cross-section of the steel pipe column or inner steel column 1.5 to 2 times; the width of the steel flange with a cross-shaped cross section is , Cross-sectional width 0.5 to 0.8 times that.

3. The embedded steel-concrete composite column base structure as described in claim 1, characterized in that, The spacing of the horizontal stiffening ribs in the bending section is 500-1000 mm, and the spacing of the horizontal stiffening ribs in the shear section is 1000-1500 mm.

4. The embedded steel-concrete composite column base structure as described in claim 1, characterized in that, The horizontal stiffening ribs are provided with multiple casting holes and multiple venting holes, and studs are provided on the web, flanges and surfaces of the outer steel column and the inner steel column.

5. A design method for the column base structure of an embedded steel-concrete composite column as described in any one of claims 1-4, characterized in that, The specific steps include: Step S1: Obtain the design information of the steel pipe columns in the superstructure and determine the initial embedment depth control value of the column base. , =0.6 times the standard allowable value ; Step S2: Set the design conditions for the column base; Step S3: Verify whether the design conditions of the column base in step S2 can meet the anchorage bearing capacity; if not, return to step S2 to reset until the design conditions of the column base meet the requirements. Step S4: Calculate the column base embedment depth to meet the stress requirements. Height of the bending section And the embedment depth of the column base to meet the rigid fixing requirements. Height of the bending section , like ＞ or ＞ Then return to step S2 until... ≤ ,and ≤ ; Step S5: Determine the final embedment depth of the column base. Height of the bending section and shear section height ,as follows: ; ; .

6. The design method for the column base structure of an embedded steel-concrete composite column as described in claim 5, characterized in that, The design information for the steel pipe column includes cross-sectional dimensions, material performance parameters, and design internal forces, wherein the cross-sectional dimensions include the diameter of the inner steel column or steel pipe column. Steel pipe column wall thickness Distance from the top of the foundation to the inflection point of the steel pipe column Material performance parameters include the material strength of the steel pipe column or internal steel column; design internal forces include bending moment. axial force Shear force .

7. The design method for the column base structure of an embedded steel-concrete composite column as described in claim 5, characterized in that, The design conditions for the column base include the strength grade of the foundation concrete, the strength grade of the external steel column, and the width of the bending section. Shear section width .

8. The design method for the column base structure of an embedded steel-concrete composite column as described in claim 5, characterized in that, In step S3: ； In the formula: A c1 - Cross-sectional area of ​​the inner steel column; A c2 - Cross-sectional area of ​​the external steel column.

9. The design method for the column base structure of an embedded steel-concrete composite column as described in claim 5, characterized in that, The column base embedment depth that meets the stress requirements in step S4 Calculate using the following formula: ； ； In the formula: Design value of compressive strength of foundation 1 concrete; The thickness of the protective layer at the top of the column base; At this point, the height of the bending section is Solve using the following formula: 。 10. The design method for the column base structure of an embedded steel-concrete composite column as described in claim 5, characterized in that, The column base embedment depth that meets the rigid fixing requirements in step S4 , Pick , The plastic bending capacity of a column is calculated using the following formula: ； ； At this point, the height of the bending section is Solve using the following formula: 。

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