Steel structure embedded column foot structure and design method

Abstract

This invention belongs to the field of building engineering technology and discloses a steel structure embedded column base construction and design method. It includes a foundation for embedding a steel column. Inside the foundation, a horizontal tensile steel section is circumferentially fixed to the bottom end of the steel column, and a diagonal tensile steel section is circumferentially fixed to the top end. The diagonal tensile steel section forms a predetermined angle with the steel column, and its free end faces the horizontal tensile steel section. The vertical projection lengths of the diagonal and horizontal tensile steel sections are the same, and they use the same cross-sectional dimensions. Internal tensile stiffening ribs or through-type steel sections are provided at the connection between the steel column and the horizontal or diagonal tensile steel sections. The through-type steel sections in the steel column use the same cross-sectional dimensions as the diagonal or horizontal tensile steel sections. This invention has the technical effect of avoiding localized stress concentration and improving the overall stability and reliability of the column base. The design method of this invention ensures the reliability of the column base design within the embedment depth.

Description

Technical Field

[0001] This invention belongs to the field of building engineering technology, specifically relating to a steel structure embedded column base construction and design method. 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] Embedded column bases are widely used in high-rise buildings and large-span structures due to their excellent embedment, stiffness, and seismic performance. To meet requirements for bending stiffness, bearing capacity, and seismic ductility, current codes (such as the "Code for Design of Composite Structures") require the embedded depth of steel columns to be 2.0 to 2.5 times the column's cross-sectional diameter or height. However, in actual engineering design, the foundation height determined through calculation and analysis is often lower than the embedded depth requirements specified in the codes. Strictly adhering to the code values ​​necessitates a significant increase in foundation height. This contradiction is particularly pronounced for large-section steel columns.

[0004] For example, in the absence of a basement, when the diameter of a circular steel pipe column reaches 3 meters, according to the aforementioned regulations, its embedment depth must meet the requirement of 2.5 times the diameter, i.e., 7.5 meters. If the length of structural components such as anchor bolts at the column base is also taken into account, the overall foundation height may increase to 8.0 to 8.5 meters. This leads to a significant increase in the amount of excavation for a single column foundation pit, the scale of support, and the need for dewatering. On the other hand, it also causes a surge in the amount of foundation materials used, significantly increases the construction difficulty and safety risks, and dramatically raises the overall project cost, causing enormous challenges to engineering design and construction practices.

[0005] To address the aforementioned issues, existing technology discloses an overhanging beam-type embedded column base structure that reduces the height of the foundation. The technical solution is as follows: an overhanging steel beam is installed on the portion of the frame column steel embedded in the foundation, extending towards the surrounding piles. The overhanging steel beam and the column steel form an integral steel component. By replacing the positioning bolts with a supporting steel frame, the minimum embedment depth required by the specification is reduced to 0.6 times, thereby reducing the height of the foundation.

[0006] While the above solution optimizes the burial depth issue, it still has the following technical shortcomings: The above-mentioned overhanging steel beams must radiate strictly along the direction of the foundation piles at the bottom of the column base to transfer the axial force and shear force of the column to the foundation piles. However, the tension side of the "top bending section" of the column base is not optimized. For non-multi-pile cap scenarios (such as independent foundations) or large bending moment conditions, the lack of a targeted tensile bearing structure may lead to incomplete force transmission coverage and local stress concentration, causing component damage. In addition, the above-mentioned scheme only verifies the bearing capacity of the overhanging steel beams based on the "pure steel beam section strength" and does not independently verify the anchorage bearing capacity and plastic hinge formation requirements of the column base. For large-section steel columns (such as circular steel pipe columns with a diameter of 3m), ignoring the verification of plastic hinge and anchorage reliability will result in insufficient column base stiffness, which will not meet the design requirements for seismic ductility and energy dissipation capacity. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a steel structure embedded column base construction and design method, which can solve the technical problems of existing overhanging steel beams having local stress concentration that easily leads to component damage and failing to meet seismic design requirements.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In one aspect, a steel structure embedded column base structure is provided, including a foundation in which a steel column is embedded, wherein a horizontal tensile steel is circumferentially fixedly connected to the bottom end of the steel column and an oblique tensile steel is circumferentially fixedly connected to the top end of the steel column. The inclined tensile steel section forms a set angle with the steel column, and the free end of the inclined tensile steel section faces the horizontal tensile steel section; Internal tensile stiffening ribs or through-beams are provided at the connection between the steel column and the horizontal or diagonal tensile steel. The through-beams in the steel column have the same cross-sectional dimensions as the horizontal tensile steel.

[0009] Preferably, both the oblique tensile steel and the horizontal tensile steel adopt an open section, and the ratio of the overhang length of the oblique tensile steel and the horizontal tensile steel to the section height is 1.5~2.0; the included angle between the oblique tensile steel and the steel column is 45~60 degrees.

[0010] Preferably, the cross-sectional shape of the steel column is any one of I-shaped, cross-shaped, rectangular steel tube, or circular steel tube; When the steel column section is I-shaped, the diagonal tensile steel is arranged only in the direction of the strong axis; When the cross section of the steel column is a cross-shaped, rectangular, or circular steel tube, the oblique tensile steel and the horizontal tensile steel are arranged in a cross shape along the cross section of the steel column, just like the horizontal tensile steel. When the cross section of the steel column is I-shaped or cross-shaped, internal tensile stiffening ribs are provided at the corresponding positions where the upper and lower flanges of the inclined tensile steel or horizontal tensile steel connect to the steel column. When the cross-section of the steel column is a rectangular or circular steel tube, a through-type steel section is installed in the horizontal direction at the connection point between the inclined tensile steel or the horizontal tensile steel and the steel column.

[0011] Preferably, when the steel column cross-section is a rectangular steel tube or a circular steel tube, a top stiffening rib is provided at the top of the steel column inside the foundation, and a bottom stiffening rib is provided at the bottom of the steel column.

[0012] Preferably, the flanges and webs of the inclined tensile steel, horizontal tensile steel, and steel column are all equipped with studs; the bottom surface of the steel column and the bottom surface of the free end of the horizontal tensile steel are fixed by a fixed steel frame.

[0013] Secondly, a design method for the aforementioned embedded column base structure of a steel structure is provided, the specific steps of which include: Step S1: Obtain the design information of the steel columns in the superstructure; Step S2: Set the design conditions for the column base; Step S3: Determine the initial embedment depth control value of the column base. Check whether the anchorage bearing capacity of the column base meets the requirements. If it does, proceed to the next step; otherwise, return to step S2 to adjust the design conditions until they are met. Step S4: Calculate the column base embedment depth to meet the stress requirements. and the embedment depth of the column base to meet the requirements of plastic hinge. ,like ≤ and ≤ If the design is successful, the design is complete; otherwise, return to step S2 to adjust the design conditions and re-execute step S3.

[0014] Preferably, the steel column design information includes the distance from the top of the foundation to the inflection point of the steel column. The properties of steel and concrete in steel columns, bending moment axial force Shear force .

[0015] Preferably, the column base design conditions include the foundation concrete strength grade, steel strength grade, cross-sectional dimensions of the diagonal tensile steel section, and its vertical angle with the steel column. In addition to the cross-sectional dimensions of the horizontal tensile steel, the horizontal tensile steel must also meet the following requirements: ; ; In the formula: This refers to the cross-sectional area of ​​the horizontal tensile steel section; This refers to the width of the upper flange of a horizontal tensile steel section. This refers to the design value of the tensile strength of the steel section. This refers to the design value of the shear strength of the steel section. The design value of the compressive strength of the foundation concrete; This refers to the single-sided outward extension length of the horizontal tensile steel section; Net section modulus of horizontal tensile steel; This is the plastic development coefficient of the cross section, and its value is taken according to the specification.

[0016] Preferred, The anchorage bearing capacity is 0.6 times the minimum embedment depth of the column base specified in the current standard. It needs to be increased to the original anchorage bearing capacity. 1 / 0.6 = 1.7 times, expressed by the following formula: ; ; ; ; In the formula: The cross-sectional area of ​​the steel column; The cross-sectional area of ​​the inclined tensile steel section; This refers to the cross-sectional area of ​​the horizontal tensile steel section; It is the vertical angle between the inclined tensile steel section and the steel column.

[0017] Preferred, The calculation is performed according to the following rules: When the steel column is an I-shaped or rectangular steel pipe column ; In the formula: The width of the pressure contact surface between the column and the concrete is used; for I-shaped or cross-shaped columns, it can be the width of the column flange; for rectangular steel pipe columns, it can be the width of the column. The cross-sectional height of the through-section steel and horizontal tensile steel within the steel column; When the steel column is a circular steel pipe column ; In the formula: The outer diameter of the circular steel pipe / column; The calculation is performed according to the following rules: When the steel column is an I-shaped or rectangular steel pipe column ; When the steel column is a circular steel pipe column ; In the formula: This represents the design value for the plastic bending capacity of the column. The yield strength of the steel section; It is the standard value of the compressive strength of the base concrete.

[0018] Compared with the prior art, the advantages and positive effects of this invention are: The column base structure of this invention, by incorporating horizontal and diagonal tensile steel sections, particularly the diagonal tensile steel sections arranged at a set angle with their free ends facing the horizontal tensile steel sections, forms a more three-dimensional tensile network. This network more effectively captures and transmits the tensile force caused by bending moment, thus avoiding localized stress concentration and improving the overall stability and reliability of the column base. Furthermore, this invention incorporates internal tensile stiffening ribs or through-type steel sections within the steel column at the connection between the steel column and the tensile steel sections, ensuring the strength and stiffness of key force transmission nodes.

[0019] The design method of this invention, through a step-by-step iterative and multi-condition comprehensive judgment strategy, ensures that the determined embedment depth not only meets the minimum requirements of the specifications, but also fully utilizes the tensile properties of the horizontal and diagonal tensile steel in the column base structure, thus ensuring the safety and reliability of the column base under various working conditions. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a perspective view of the embedded column base structure of the steel column in the form of an I-beam as described in Embodiment 1 or Embodiment 2 of the present invention; Figure 2 This is a top view of the embedded column base structure of the steel column in the form of an I-beam in Embodiment 1 or Embodiment 2 of the present invention; Figure 3 yes Figure 2 Cross-sectional view of AA in the middle; Figure 4 This is a perspective view of the cross-shaped embedded column base structure of the steel column in Embodiment 1 or Embodiment 2 of the present invention; Figure 5 This is a top view of the embedded steel column base structure with a cross shape, as described in Embodiment 1 or Embodiment 2 of the present invention. Figure 6 yes Figure 5 Cross-sectional view of BB in the middle; Figure 7 This is a perspective view of the embedded column base structure of the steel column, which is a rectangular steel tube, in Embodiment 1 or Embodiment 2 of the present invention. Figure 8 This is a top view of the embedded column base structure of the steel column, which is a rectangular steel tube, in Embodiment 1 or Embodiment 2 of the present invention. Figure 9 yes Figure 8 Cross-sectional view of CC in the middle; Figure 10 This is a perspective view of the embedded column base structure of the steel column, which is a circular steel pipe, in Embodiment 1 or Embodiment 2 of the present invention. Figure 11 This is a top view of the embedded column base structure of the steel column, which is a circular steel pipe, in Embodiment 1 or Embodiment 2 of the present invention. Figure 12 yes Figure 11 Cross-sectional view of DD in the middle; Figure 13 This is a flowchart illustrating the design method of the embedded column base structure of the steel structure according to Embodiment 2 of the present invention. Figure 14 This is a schematic diagram illustrating the force-bearing principle of the embedded column base structure in Embodiment 2 of the present invention. In the picture: 1. Steel column; 2. Foundation; 3. Diagonal tensile steel; 4. Horizontal tensile steel; 5. Internal tensile stiffener; 6. Through steel in the steel column; 7. Fixed steel frame; 8. Stiffener at the top of the column base; 9. Stiffener at the bottom of the column base; 10. Studs. Detailed Implementation

[0022] 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.

[0023] The present invention will now be described in detail with reference to the accompanying drawings.

[0024] Example 1 This embodiment discloses a steel structure embedded column base structure, such as Figure 1 , Figure 4 , Figure 7 , Figure 10 As shown, the foundation 2 includes a steel column 1 embedded within it. Inside the foundation 2, the bottom end of the steel column 1 is circumferentially fixedly connected to a horizontal tensile steel 4, and the top end of the steel column 1 is circumferentially fixedly connected to a diagonal tensile steel 3. It can be understood that the foundation is a concrete foundation.

[0025] It should be noted that within foundation 2, the horizontal tensile steel 4 is a structural member installed at the bottom of the steel column 1 and fixedly connected circumferentially. It is generally arranged in a cross pattern and is mainly used to enhance the resistance of the bottom of the steel column 1 to horizontal tensile forces and to assist in the transfer of bending moments. The diagonal tensile steel 3 is a structural member installed at the top of the steel column 1 and fixedly connected circumferentially. The placement of the diagonal tensile steel 3 needs to be determined based on the cross-section of the steel column 1. It is important to note that the diagonal tensile steel 3 forms a predetermined angle with the steel column 1, and the free end of the diagonal tensile steel 3 faces the horizontal tensile steel 4. It is mainly used to enhance the resistance of the top of the steel column 1 to diagonal tensile forces and to assist in the transfer of bending moments.

[0026] In this embodiment, the diagonal tensile steel 3 and the horizontal tensile steel 4 are made of the same steel. The horizontal tensile steel 4 and the diagonal tensile steel 3 work together to form two key tensile zones at the top and bottom of the steel column 1 embedded in the foundation 2. These tensile steels significantly enhance the column base's resistance to bending moment and tension through their own tensile strength and anchoring with the concrete.

[0027] In this embodiment, as Figure 3 , Figure 6 , Figure 9 , Figure 12 As shown, internal tensile stiffeners 5 or through-beams 6 are installed at the connection between steel column 1 and horizontal tensile steel 4 or diagonal tensile steel 3. These are used to enhance the local stiffness and bearing capacity of the connection node, prevent local buckling or failure, ensure reliable transmission of the tensile force introduced by the horizontal tensile steel 4 or diagonal tensile steel 3 in the connection area, and improve the overall strength and force transmission efficiency of the connection area. It should be noted that the through-beams 6 and horizontal tensile steel 4 have the same cross-sectional dimensions and are connected to the diagonal tensile steel 3 or horizontal tensile steel 4 and the column wall through welding or bolting. This ensures smooth transmission of tensile force between them, avoids stress concentration caused by abrupt changes in cross-section, and also helps simplify design and construction, ensuring the reliability of the connection and the integrity of the overall structure.

[0028] In this embodiment, the diagonal tensile steel 3 and the horizontal tensile steel 4 can be fixed to the flange or web of the steel column 1 by welding or bolting. To ensure the symmetry of the tensile force provided by the steel sections in the upper and lower bending sections of the column base, the cross-sectional area of ​​the horizontal tensile steel is... and the cross-sectional area of ​​diagonal tensile steel The following formula must be satisfied: .

[0029] Existing solutions only use outward-extending steel beams along the pile direction, which may be insufficient for covering the tension side force transmission under conditions other than multi-pile caps or large bending moments. In this embodiment, the horizontal and diagonal tensile steel beams, especially the diagonal tensile steel beams arranged at a set angle with their free ends facing the horizontal tensile steel beams, form a more three-dimensional tensile network. This network can more effectively capture and transmit the tensile force caused by bending moment, avoiding localized stress concentration and thus improving the overall stability and reliability of the column base.

[0030] Furthermore, this embodiment incorporates internal tensile stiffening ribs or through-type steel sections within the steel column at the connection between the steel column and the tensile steel section, ensuring the strength and stiffness of critical force transmission nodes. This contrasts with existing techniques that calculate the load-bearing capacity of outrigger steel beams based on the cross-sectional strength of pure steel beams, neglecting the anchorage bearing capacity and plastic hinge formation requirements at the column base. The structural design of this embodiment, by enhancing the performance of the connection area, provides a more reliable structural foundation for the anchorage bearing capacity and plastic hinge formation at the column base, thereby ensuring the seismic ductility and energy dissipation capacity of the column base under extreme loads, meeting higher requirements for structural safety and durability.

[0031] In this embodiment, both the oblique tensile steel 3 and the horizontal tensile steel 4 adopt open-section sections, which are H-shaped or cross-shaped. The open-section steel has good bending and torsional resistance, which facilitates connection with the steel column. Furthermore, the use of open-section steel components makes it easier for the concrete to fill and wrap the oblique tensile steel 3 and the horizontal tensile steel 4 during concrete pouring, ensuring a reliable connection between the oblique tensile steel 3 and the horizontal tensile steel 4 and the concrete.

[0032] In this embodiment, to ensure the anchoring performance of the inclined tensile steel 3 and the horizontal tensile steel 4, the ratio of the overhang length of the inclined tensile steel 3 and the horizontal tensile steel 4 to the section height is taken as 1.5 to 2.0; to avoid the inclined tensile steel 3 from being punched by the insufficient thickness of the concrete at the top of the foundation 2, the angle between the inclined tensile steel and the steel column is taken as 45 to 60 degrees and the free end faces the horizontal tensile steel.

[0033] like Figure 2 , Figure 5 , Figure 8 , Figure 11 As shown, in this embodiment, the cross-sectional shape of the steel column is any one of I-beam, cross-shaped, rectangular steel tube, or circular steel tube. It should be noted that the cross-sectional shape of the steel column refers to its geometric shape in a plane perpendicular to its axis. These cross-sectional shapes are standard profiles commonly used in engineering structures, each with different mechanical properties and construction characteristics. For example, the I-beam cross-section has high bending stiffness and load-bearing capacity; the cross-shaped cross-section has similar bending performance in both principal axis directions; rectangular and circular steel tube cross-sections have good compressive and bending resistance, and their internal space can be used to fill concrete, providing higher load-bearing capacity and stability. Different cross-sectional shapes can be selected for optimization based on architectural design, load conditions, and economic requirements.

[0034] like Figure 1 , Figure 2As shown, when the cross-section of steel column 1 is I-shaped, due to the distinct strong and weak axes, the bending stiffness of steel column 1 in the strong axis direction is much greater than that in the weak axis direction. In this case, the diagonal tensile steel section 3 at the top is arranged only in the strong axis direction, effectively utilizing the load-bearing advantage of the I-shaped steel column in the strong axis direction to primarily resist the tensile force caused by the bending moment along the strong axis. This arrangement simplifies the construction and concentrates the strengthening of tensile performance in the main load-bearing direction. Figure 1 , Figure 2 As shown, the horizontal tensile steel 4 at the bottom is arranged in a cross shape along the cross section of the steel column 1.

[0035] like Figure 4 , Figure 5 , Figure 7 , Figure 8 , Figure 10 , Figure 11 As shown, when the cross-section of steel column 1 is a cross-shaped, rectangular, or circular steel tube, these cross-sections typically possess good bidirectional load-bearing capacity or isotropic properties (such as a circular steel tube). In this case, the oblique tensile steel 3 and the horizontal tensile steel 4 are arranged in a cross-shaped pattern along the cross-section of steel column 1, ensuring that the column base has balanced tensile strength in all directions, thus effectively resisting bending moments from any direction. This symmetrical or multi-directional arrangement provides more comprehensive anchorage performance and is suitable for structures subjected to complex multi-directional loads.

[0036] In this embodiment, as Figure 1 , Figure 3 , Figure 4 , Figure 6 As shown, when the cross-section of steel column 1 is I-shaped or cross-shaped, internal tensile stiffeners 5 are provided at the corresponding positions where the upper and lower flanges of the oblique tensile steel 3 or horizontal tensile steel 4 connect to steel column 1. These internal tensile stiffeners 5 effectively transmit the horizontal tensile force generated by the oblique tensile steel by providing additional local stiffness and bearing area, thereby enhancing the local stiffness and bearing capacity of the steel column. This prevents local stress concentration and buckling failure, ensuring the strength and stability of the connection area.

[0037] like Figure 7 , Figure 9 , Figure 10 , Figure 12As shown, when the cross-section of steel column 1 is a rectangular or circular steel tube, a through-beam 6 is installed horizontally at the connection point between the oblique tensile steel 3 or the horizontal tensile steel 4 and steel column 1. It should be noted that the through-beam 6 refers to a steel member that passes through the interior of the steel column and connects to the oblique tensile steel 3 or the horizontal tensile steel 4. When the cross-section of steel column 1 is a rectangular or circular steel tube, since its interior is hollow, directly connecting the oblique tensile steel 3 or the horizontal tensile steel 4 to the tube wall may lead to excessive local stress or tube wall deformation. A through-beam 6 is installed horizontally at the corresponding position of the tensile steel. The through-beam 6 serves as an intermediate medium for the transmission of tensile force, transferring the tensile force of the inclined tensile steel 3 or the horizontal tensile steel 4 from one side of the pipe wall of the steel column 1 to the other side and distributing it evenly throughout the entire cross section of the steel pipe column. This avoids local stress concentration in the pipe wall of the steel column 1 and improves the tensile bearing capacity and integrity of the column base of the steel column 1.

[0038] This embodiment, through its meticulously designed column base structure, enables it to better adapt to the mechanical properties of different steel column types, thereby improving the overall performance and safety of the entire embedded column base structure.

[0039] like Figure 9 , 12 As shown, when the steel column section is a rectangular steel tube or a circular steel tube, a top stiffening rib 8 is provided at the top of the steel column 1 inside the foundation 2, and a bottom stiffening rib 9 is provided at the bottom of the steel column to ensure the rigidity of the junction between the steel column and the foundation.

[0040] Understandably, compared to solid-web steel columns, the wall panels of tubular cross-section steel columns have relatively weaker stiffness under localized stress, especially in areas directly in contact with the foundation concrete, making them prone to localized deformation. The column base stiffening rib 8 refers to the reinforcing member installed at the top of the portion of the steel column 1 embedded in the foundation 2, near the interface between the steel column and the foundation concrete. The main function of the column base stiffening rib 8 is to enhance the local stiffness of the steel column 1's tubular wall, effectively resisting localized stress concentration caused by bending moments and shear forces transmitted from the superstructure, and assisting in more evenly distributing the internal forces of the steel column to the foundation concrete.

[0041] The bottom stiffening rib 9 of the column base refers to the stiffening member set at the bottom of the part of the steel column 1 embedded in the foundation 2, that is, the lowest end of the steel column. Its main function is to work together with the top stiffening rib of the column base to enhance the overall stiffness of the steel column inside the foundation. Especially for tubular cross-section steel columns, the bottom stiffening rib helps to prevent local buckling of the column base when subjected to axial pressure or bending moment, and ensures the effective anchorage of the horizontal tensile steel.

[0042] like Figures 1 to 12As shown, shear studs 10 are provided on the flanges and webs of the oblique tensile steel 3, the horizontal tensile steel 4, and the steel column 1 to enhance overall integrity and anchorage reliability. The studs 10 are used to connect the steel components and the concrete components, allowing them to share the load. In this embodiment, the diameter of the studs 10 ranges from 19mm to 22mm, and the spacing of the studs 10 ranges from 150mm to 200mm.

[0043] like Figure 3 , Figure 6 , Figure 9 , Figure 12 As shown, a fixed steel frame 7 is used for installation and fixation on the bottom surface of the steel column 1 and the bottom surface of the free end of the horizontal tensile steel 4 to reduce the increase in foundation height caused by the installation of anchor bolts and further optimize the foundation height. The fixed steel frame is used to position and temporarily fix the steel column and tensile steel during the construction phase to ensure that the column base assembly can be accurately held in the predetermined position and posture before concrete pouring. It should also be noted that the above-mentioned steel components in this embodiment can all be prefabricated in the factory and then welded or bolted on site, making construction convenient and quick.

[0044] Example 2 This embodiment discloses a structural design method for a steel structure embedded column base, which involves designing and verifying the component dimensions and material parameters of a steel structure embedded column base disclosed in Embodiment 1. Figure 13 As shown, the specific steps include: Step S1: Obtain the design information for steel column 1 in the superstructure. This step aims to provide necessary input data for subsequent column base design and embedment depth calculation. Specifically, the design information can be directly exported from the calculation results of structural analysis software (such as finite element analysis software, such as SAP2000, ETABS, or the commonly used PKPM in China). These software programs can provide internal force data for steel column 1 under various load combinations; alternatively, designers can manually review and compile the required cross-sectional dimensions, material performance parameters, and design internal forces of steel column 1 based on structural design drawings and calculation sheets.

[0045] Step S2: Define the design conditions for the column bases (steel columns 1 embedded in foundation 2 and all tensile steel sections). This step clarifies the design objectives and constraints of the column bases, guiding subsequent verification and calculation processes. Design conditions can be set according to the specific requirements of the project, such as considering the structural importance level of the building, the seismic fortification intensity of the region, and the usage environment; alternatively, designers can determine the corresponding design conditions based on the provisions regarding column base performance and safety levels in current national or industry design codes (such as the "Code for Design of Steel Structures" and the "Code for Design of Concrete Structures"), for example, specific requirements for bearing capacity, stiffness, or ductility.

[0046] Step S3: Determine the initial embedment depth control value of the column base. , The minimum embedment depth of the column base is 0.6 times that specified in the current code. Verify that the anchorage bearing capacity of the column base meets the requirements. If it does, proceed to the next step; otherwise, return to step S2 to adjust the design conditions until they are met. The purpose of this step is to ensure that the column base can reliably resist the tensile force transmitted from the superstructure after being embedded in foundation 2, preventing the column base from being pulled out of foundation 2.

[0047] Step S4: Calculate the column base embedment depth to meet the internal force requirements at the column base. And the column base embedment depth that meets the ultimate bending bearing capacity requirements of the column base. ,like ≤ and ≤ If the design in step S2 is successful, the design is complete. Otherwise, return to step S2 to adjust the design conditions and repeat step S3. The purpose of this step is to ensure that the embedment depth of the column base meets the requirements of the internal forces and ultimate bending capacity of the column base, to prevent the column base from undergoing plastic failure before the column, and to ensure the overall seismic performance and ductility of the column base.

[0048] The structural design method of this application, through a step-by-step iterative and multi-condition comprehensive judgment strategy, ensures that the determined embedment depth not only meets the minimum requirements of the specification, but also fully utilizes the tensile strength of the horizontal and diagonal tensile steel in the above-mentioned embedded steel column base structure, thus ensuring the safety and reliability of the column base under various working conditions.

[0049] It should be noted that the steel column design information in step S1 includes cross-sectional dimensions, material property parameters, and design internal forces. Cross-sectional dimensions are the geometric characteristics of the steel column's cross-section, directly affecting its mechanical properties such as moment of inertia and section modulus. These include the cross-sectional width or flange width used for area calculation, cross-sectional height, flange thickness, web thickness, and the distance from the top of the foundation to the inflection point of the steel column. Material performance parameters refer to the mechanical properties of the steel used in steel column 1, which are crucial for evaluating the load-bearing capacity of the steel column. Also included are the performance parameters of the concrete cladding the steel column 1. Design internal forces refer to the various load effects acting on the steel column and are the core input for structural analysis, including bending moments. axial force Shear force These internal forces reflect the loads transferred from the superstructure to the column bases. The design internal force information can be calculated using structural analysis software or determined according to design specifications and load combinations.

[0050] In this embodiment, the column base design conditions include the concrete strength grade of the foundation 2, the cross-sectional dimensions of the inclined tensile steel 3, and its vertical angle with the steel column 1. In addition to the cross-sectional dimensions of the horizontal tensile steel 4, the strength grades of the steel used for the oblique tensile steel 3 and the horizontal tensile steel 4, and considering that the horizontal tensile steel 4 relies on the compression of the upper flange concrete for anchorage, the horizontal tensile steel 4 must also meet the following requirements: ; ; In the formula: The cross-sectional area of ​​the horizontal tensile steel is 4. The width of the upper flange of the horizontal tensile steel section 4; The design value of tensile strength for structural steel (the oblique tensile steel 3 and the horizontal tensile steel 4 are made of the same steel, and are collectively referred to as structural steel); This refers to the design value of the shear strength of the steel section. The design value of the compressive strength of the foundation concrete; The horizontal tensile steel section is the single-sided overhang length, which is the effective contact and anchorage range between the horizontal tensile steel section and the foundation concrete. Net section modulus of horizontal tensile steel; This is the plastic development coefficient of the cross section, and its value is taken according to the specification.

[0051] To ensure the symmetry of the tensile force provided by the upper and lower bending sections of the column base steel, the cross-sectional area of ​​the horizontal tensile steel is... and the cross-sectional area of ​​diagonal tensile steel The following formula must be satisfied: ; In step S3, since the anchorage performance of the column base is directly proportional to the anchorage bearing capacity of the component, if the embedment depth is to be optimized and reduced, the anchorage bearing capacity of the component needs to be increased. Assuming the embedment depth control value... Taking 0.6 times the standard value, the current anchorage bearing capacity is... The anchorage bearing capacity needs to be increased to the level specified in the original code. 1 / 0.6 = 1.7 times, expressed by the following formula: ; ; ; In the formula: The cross-sectional area of ​​the steel column; The cross-sectional area of ​​the inclined tensile steel section; It is the vertical angle between the inclined tensile steel section and the steel column.

[0052] The tensile contribution of the steel column 1 itself, as well as the tensile contributions of the diagonal tensile steel 3 and the horizontal tensile steel 4, were taken into account.

[0053] When determining the embedment depth of the embedded column base structure of the steel structure, when performing the anchorage bearing capacity verification step S3, the preliminary anchorage bearing capacity is first calculated based on the design information of steel column 1 and the design conditions of the column base. Subsequently, to enhance the reliability of the anchorage, it is necessary to increase the anchorage bearing capacity. Multiply by 1.7 to obtain the target anchorage bearing capacity. If the actual anchoring capacity is less than this If the value is too high, the design conditions need to be adjusted, such as increasing the cross-sectional dimensions of the inclined tensile steel section and its vertical angle with the steel column. The dimensions of the horizontal tensile steel section 4 are adjusted until the requirements are met.

[0054] like Figure 14 The diagram shown illustrates the force distribution principle of an embedded column base in a steel structure. The required embedment depth of the column base to meet the force requirements during the solution process is also relevant. The following rules must be followed: When the steel column is an I-shaped or rectangular steel pipe column ; ; ; ; ; In the formula: This refers to the length of the bending section; This refers to the length of the shear-resistant section; This refers to the design value of the tensile strength of the steel section. This refers to the design value of the axial tensile force of the horizontal tensile steel section. This refers to the design value of the axial tensile force of the inclined tensile steel. The width of the pressure contact surface between the column and the concrete is used; for I-shaped or cross-shaped columns, it can be the width of the column flange; for rectangular steel pipe columns, it can be the width of the column. The cross-sectional height of the through-section steel and horizontal tensile steel within the steel column; This refers to the cross-sectional area of ​​the horizontal tensile steel section.

[0055] Solving the above formula, we get: ; When the cross-sectional shape is a circular steel pipe column, considering the reduction in the width of the arc-shaped compressive surface of the steel pipe column, the width of the pressure contact surface between the steel pipe column and the concrete can be taken as 0.8D. Then the formula for calculating the embedment depth is as follows: ; In the formula: It is the outer diameter of the circular steel pipe column.

[0056] The embedment depth d2 of the column base that meets the requirements of the plastic hinge is calculated according to the following principle: Still refer to Figure 14 The force diagram shows that, to meet the requirements of the plastic hinge, the bending moment is based on the design value of the column's plastic bending capacity. When the column cross-section is an I-shaped or rectangular steel pipe column, assuming the bending moment and shear force at the column base are zero, the following formula applies: ; ; ; ; ; ; Solving the above formula, we get: ; When the steel column has a circular cross-section, considering the reduction in the width of the arc-shaped compressive surface of the steel pipe column, the width of the pressure contact surface between the steel pipe column and the concrete can be taken as 0.8D. Then, the formula for calculating the embedment depth is as follows: ; In the formula: The ultimate bearing capacity of the connection between the column base and the foundation is calculated according to the "Technical Specification for Concrete-Concrete Composite Structures" and the "Code for Seismic Design of Buildings"; it represents the maximum bending moment design value that the steel column can withstand when plastic failure occurs. It serves as a key input for the embedment depth d2 to meet the ultimate bending bearing capacity requirements of the column base, ensuring that the column base can remain stable when the plastic state is reached. The yield strength of oblique tensile steel or horizontal tensile steel; It is the standard value of the compressive strength of the base concrete.

[0057] Step S4 comprehensively considers the design internal forces (bending moments) of steel column 1. axial force The compressive strength of the foundation concrete, the cross-sectional dimensions of steel column 1, the tensile contributions of the diagonal tensile steel 3 and the horizontal tensile steel 4, and the design value of the column's plastic bending bearing capacity are all considered. Specifically, by balancing the external bending moment With internal resistance moment, and internal resistance moment is caused by axial force The combined effect of the concrete compressive strength and the tensile strength of the inclined tensile steel section 3 and the horizontal tensile steel section 4 constitutes the structure. The results can be calculated using the combined formulas. And the external bending moment Replace with the design value of the plastic bending capacity of the column. The simultaneous formulas can be used to calculate... .

[0058] In a specific example of a construction design method: Assuming steel column 1 is a concrete-filled steel tube column with an outer diameter D = 3000mm, a wall thickness of 60mm, a total height of 45m, a concrete strength grade of C60, a steel tube material of Q420, a foundation concrete strength grade of C30, and tensile steel in the foundation material of Q420, the traditional column base design using a embedment depth d of 2.5D (7.5m) results in high costs for foundation pit support, dewatering, and foundation work for a single column base. The column base design method described in this embodiment optimizes the embedment depth. The design process is as follows: Step S1: Obtain the design information for the steel columns in the superstructure. The outer diameter of the steel-concrete composite column is D=3000mm, the wall thickness is 60mm, and the height from the top of the column foundation to the inflection point is... =45m, the concrete strength grade inside the pipe is C60, and the cross-sectional area of ​​the steel pipe is... =554176mm 2 The steel used for the pipes is Q420, and the tensile, bending and tensile strengths of the steel are [not specified]. =320N / mm 2 shear strength =185N / mm 2 Yield strength is =380N / mm 2 Bending moment design value =167970 kN·m, shear force design value =3733KN.

[0059] Step S2: Set the design conditions for the column base. The foundation concrete strength grade is C30, and the design value of the concrete compressive strength is... =14.3 N / mm 2 Standard value of concrete compressive strength =20.1 N / mm 2The foundation internal tensile steel is made of Q420 steel, and the angle between the top diagonal tensile steel and the vertical steel column is... =45°, the length of the inclined tensile steel is taken as 1.5m, and the outward extension length of the horizontal tensile steel is... =1.2m, the information of the through steel section corresponding to the horizontal tensile steel and the top inclined tensile steel is as follows: H-shaped section, flange and web thickness are both 40mm, section height is 500mm, upper and lower flange widths are... = =600mm, cross-sectional area =64800mm 2 Net section modulus =11170240mm 3 Section plastic development coefficient =1.05. Information on the oblique tensile steel section is as follows: H-shaped section is used. =91641mm 2 .

[0060] Verification of the tensile strength of the bottom steel section:

[0061]

[0062] Not satisfied The requirements necessitate returning to the previous step for adjustment; After trial calculations and adjustments, the steel profile information for the through-section steel columns corresponding to the horizontal tensile steel and the top diagonal tensile steel is updated as follows: H-shaped cross-section, flange and web thickness both 40mm, cross-section height 800mm, upper and lower flange widths both 700mm, and cross-sectional area both 84800mm². 2 Net section modulus =23345066.67mm 3 The section plastic development coefficient γx = 1.05. Information on the oblique tensile steel section is as follows: It adopts an H-shaped section. =119925mm 2 The verification is as follows:

[0063]

[0064] If the requirements are met, proceed to step S3 for verification.

[0065] Step S3: Verify whether the anchorage bearing capacity of the column base meets the requirements: ; ;

[0066] After verifying that the requirements are met, proceed to the next step and calculate. and .

[0067] Step S4: The embedment depth d1 of the column base that meets the stress requirements is calculated as follows: ;

[0068] Column base embedment depth to meet plastic hinge requirements The solution is as follows: ; ; ; ; ; ; ; In the formula: The steel content of the concrete-filled steel tube member. For concrete-filled steel tube members, the confinement coefficient is... B, C The 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.

[0069]

[0070] Based on the calculation results, it can be seen that ≤ and ≤ If so, then the design of step S2 is successful.

[0071] The final embedment depth of the column base d=4.5m is 40% less than the standard value of 7.5m (2.5D), which can significantly reduce the foundation size, foundation pit excavation and support costs, reduce construction difficulty and save construction costs.

[0072] 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 steel structure embedded column base structure, characterized in that, The foundation includes a steel column, inside which a horizontal tensile steel section is circumferentially fixedly connected to the bottom end of the steel column, and an oblique tensile steel section is circumferentially fixedly connected to the top end of the steel column. The inclined tensile steel is at a set angle to the steel column, and the free end of the inclined tensile steel is oriented towards the horizontal tensile steel. Internal tensile stiffening ribs or through-type steel sections are provided at the connection between the steel column and the horizontal tensile steel or the diagonal tensile steel; the through-type steel section and the diagonal tensile steel or the horizontal tensile steel have the same cross-sectional dimensions.

2. The embedded column base structure of a steel structure as described in claim 1, characterized in that, Both the inclined and horizontal tensile steel sections adopt open sections, and the ratio of the overhang length to the section height of the inclined and horizontal tensile steel sections is 1.5 to 2.0; the included angle between the inclined tensile steel section and the steel column is 45 to 60 degrees.

3. The embedded column base structure of a steel structure as described in claim 1, characterized in that, The cross-sectional shape of the steel column is any one of I-shaped, cross-shaped, rectangular steel tube, or circular steel tube; When the steel column section is I-shaped, the diagonal tensile steel is arranged only in the direction of the strong axis; When the cross section of the steel column is a cross-shaped, rectangular, or circular steel tube, the oblique tensile steel and the horizontal tensile steel are arranged in a cross shape along the cross section of the steel column, just like the horizontal tensile steel. When the cross section of the steel column is I-shaped or cross-shaped, internal tensile stiffening ribs are provided at the corresponding positions where the upper and lower flanges of the inclined tensile steel or horizontal tensile steel connect to the steel column. When the cross-section of the steel column is a rectangular or circular steel tube, a through-type steel section is installed in the horizontal direction at the connection point between the inclined tensile steel or the horizontal tensile steel and the steel column.

4. The embedded column base structure of a steel structure as described in claim 3, characterized in that, When the cross-section of the steel column is a rectangular steel tube or a circular steel tube, a top stiffening rib is provided at the top of the steel column inside the foundation, and a bottom stiffening rib is provided at the bottom of the steel column.

5. The embedded column base structure of a steel structure as described in claim 1, characterized in that, The flanges and webs of the inclined tensile steel, horizontal tensile steel, and steel columns are all equipped with studs; the bottom surface of the steel columns and the bottom surface of the free ends of the horizontal tensile steel are fixed by a fixed steel frame.

6. The design method for a steel structure embedded column base as described in any one of claims 1-5, characterized in that, The specific steps include: Step S1: Obtain the design information of the steel columns in the superstructure; Step S2: Set the design conditions for the column base; Step S3: Determine the initial embedment depth control value of the column base. Check whether the anchorage bearing capacity of the column base meets the requirements. If it does, proceed to the next step; otherwise, return to step S2 to adjust the design conditions until they are met. Step S4: Calculate the column base embedment depth to meet the stress requirements. and the embedment depth of the column base to meet the requirements of plastic hinge. ,like ≤ and ≤ If the design is successful, the design is complete; otherwise, return to step S2 to adjust the design conditions and re-execute step S3.

7. The design method for a steel structure embedded column base as described in claim 6, characterized in that, The steel column design information includes the distance from the top of the foundation to the inflection point of the steel column. The properties of steel and concrete in steel columns, bending moment axial force Shear force .

8. The design method for a steel structure embedded column base as described in claim 6, characterized in that, The column base design conditions include the foundation concrete strength grade, steel strength grade, cross-sectional dimensions of the diagonal tensile steel section, and its vertical angle with the steel column. In addition to the cross-sectional dimensions of the horizontal tensile steel, the horizontal tensile steel must also meet the following requirements: ； ； In the formula: This refers to the cross-sectional area of ​​the horizontal tensile steel section; This refers to the width of the upper flange of a horizontal tensile steel section. This refers to the design value of the tensile strength of the steel section. This refers to the design value of the shear strength of the steel section. The design value of the compressive strength of the foundation concrete; This refers to the single-sided outward extension length of the horizontal tensile steel section; Net section modulus of horizontal tensile steel; This is the plastic development coefficient of the cross section, and its value is taken according to the specification.

9. The design method for a steel structure embedded column base as described in claim 6, characterized in that, The The anchorage bearing capacity is 0.6 times the minimum embedment depth of the column base specified in the current standard. It needs to be increased to the original anchorage bearing capacity. 1 / 0.6 = 1.7 times, expressed by the following formula: ； ； ； ； In the formula: The cross-sectional area of ​​the steel column; The cross-sectional area of ​​the inclined tensile steel section; This refers to the cross-sectional area of ​​the horizontal tensile steel section; It is the vertical angle between the inclined tensile steel section and the steel column.

10. The design method for a steel structure embedded column base as described in claim 6, characterized in that, The The calculation is performed according to the following rules: When the steel column is an I-shaped or rectangular steel pipe column ； In the formula: The width of the pressure contact surface between the column and the concrete is used; for I-shaped or cross-shaped columns, it can be the width of the column flange; for rectangular steel pipe columns, it can be the width of the column. The cross-sectional height of the through-section steel and horizontal tensile steel within the steel column; When the steel column is a circular steel pipe column ； In the formula: The outer diameter of the circular steel pipe / column; The d2 calculation is performed according to the following rules: When the steel column is an I-shaped or rectangular steel pipe column ； When the steel column is a circular steel pipe column ； In the formula: This represents the design value for the plastic bending capacity of the column. The yield strength of the steel section; It is the standard value of the compressive strength of the base concrete.

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