Prestressed cable with external bracket self-resetting special-shaped embedded column base joint

Abstract

The application provides a peripheral corbel prestressed cable type self-resetting special-shaped cross-section embedded column foot joint, which comprises a special-shaped cross-section steel pipe concrete column, a corbel is arranged at the outer extension end of the lower part of the special-shaped cross-section steel pipe concrete column, a cable is arranged on the corbel through prestress, and the corbel and the cable are both in the foundation and used for enhancing the connecting capacity of the column foot joint. The application can effectively enhance the connecting capacity of the column foot joint and the surrounding foundation concrete through the peripheral corbel and the cable, thereby improving the punching shear resistance and the anti-seismic capacity of the column foot joint, achieving the purpose of reducing the embedding depth of the embedded column foot, and the column foot joint has a certain self-resetting capacity due to the prestress of the cable.

Description

Technical Field

[0001] This invention relates to the field of engineering structure technology, and in particular to an externally mounted corbel prestressed cable type self-resetting irregular cross-section embedded column base node. Background Technology

[0002] In traditional structural design, frame columns suffer from a significant convex column problem. To address this, scholars have proposed columns with irregular cross-sections. However, irregular cross-section reinforced concrete columns present challenges such as difficulties in formwork erection and ensuring the cross-sectional bearing capacity. Meanwhile, concrete-filled steel tubular (CFST) structures, with their advantages of eliminating formwork and the synergistic effect between concrete and steel tubing, are more suitable for designing irregular cross-sections. Therefore, the application of irregular cross-section CFST columns in practical engineering is becoming increasingly widespread.

[0003] However, the design and construction requirements for the most important node in irregular cross-section steel tube concrete column structures—the column foot node—are not perfect in existing design codes and studies. Existing designs often use traditional cross-section design methods, which leads to excessive embedment depth of the embedded column foot, resulting in larger foundation dimensions and increased costs. Summary of the Invention

[0004] To address the aforementioned issues, this invention aims to propose a self-resetting irregular-section embedded column base joint with external corbel prestressed cable. This joint utilizes corbels extending outwards around the lower perimeter of an irregular-section steel-concrete composite column. Prestressed cables are pre-installed on the corbels, and both the corbels and cables are embedded within the foundation to effectively enhance the connection between the column base joint and the surrounding foundation concrete. This improves the punching shear resistance and seismic resistance of the column base joint, thereby reducing the embedment depth of the embedded column base. Furthermore, the prestress in the cables provides the column base joint with a certain degree of self-resetting capability.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] An external corbel prestressed cable type self-resetting irregular cross-section embedded column base node includes an irregular cross-section steel tube concrete column. The lower part of the irregular cross-section steel tube concrete column is provided with corbels on all four sides. Cables are prestressed and installed on the corbels. The corbels and cables are both in the foundation to enhance the connection capacity of the column base node.

[0007] Furthermore, the irregular cross-section steel tube concrete column includes an irregular cross-section multi-cavity steel tube, and concrete is poured into the inner cavity of the irregular cross-section multi-cavity steel tube.

[0008] Furthermore, a column base plate is welded to the bottom of the irregular cross-section multi-cavity steel pipe. The column base plate has holes at positions corresponding to the inner cavity of the irregular cross-section multi-cavity steel pipe. Several holes are opened at predetermined positions on the outer ring of the column base plate, and ground anchors are installed through the holes and anchor nuts.

[0009] Furthermore, the ground anchor at the bottom of the column base plate is located in the pre-embedded section of the foundation, the lower part of the cable is located in the pre-embedded section of the foundation, and the corbel is located in the post-embedded section of the foundation.

[0010] Furthermore, the irregularly shaped cross-section multi-cavity steel pipe, column base plate, and corbel are all prefabricated steel components.

[0011] Furthermore, the corbel includes an upper flange plate, a web plate, a diaphragm plate, and a lower flange plate. The web plate is a vertical trapezoidal plate, and the upper end and left and right sides of the vertical trapezoidal plate are respectively welded with diaphragms, upper flange plates, and lower flange plates. The outer wall of the steel pipe of the steel-concrete composite column is welded to the upper flange plate, web plate, and lower flange plate.

[0012] Furthermore, the upper flange plate is perpendicular to the outer wall of the steel pipe of the steel-concrete composite column, and the lower flange plate is connected to the outer wall of the steel pipe of the steel-concrete composite column at an angle downward. Both the upper and lower flange plates are provided with a number of pre-set holes. The cable passes through the pre-set holes of the lower and upper flange plates of the corbel in sequence, and is prestressed and anchored.

[0013] Furthermore, the corbel also includes curved stiffening ribs, which are provided in several places between the lower flange plate and the upper flange plate and are attached to the upper part of the cable for use as baffles.

[0014] Furthermore, the punching shear capacity design of column base joints can be calculated according to the formulas in the "Code for Design of Concrete Structures GB50010-2010":

[0015] F l ≤(0.5f t +0.25σ pc，m )ηu m h0

[0016] In the formula, η should be calculated according to the following two formulas, and the smaller value should be taken:

[0017]

[0018]

[0019] F l —Design values ​​for local loads;

[0020] β h— Cross-section height influence coefficient: When h is not greater than 800mm, take β. h The value is 1.0; when h is not less than 2000 mm, β is taken. h The value is 0.9, and values ​​are taken using linear interpolation.

[0021] f t —Design value of tensile strength of concrete;

[0022] σ pc，m —The effective prestressing stress of concrete in two directions along the perimeter of the calculated section is a length-weighted average value, which should be controlled within 1.0 N / mm². 2 ~3.5N / mm 2 Within the range;

[0023] u m —Calculate the perimeter of the section by taking the most unfavorable perimeter of the vertical section of the plate at a distance of h0 / 2 from the perimeter of the area where the local load or concentrated reaction force acts;

[0024] h0 — Effective height of the section, which is the average of the effective heights of the section reinforced in two directions.

[0025] According to the calculation of anti-punching in the specification, it can be determined that the corbel in this invention raises the punching starting surface from the bottom plate by d2-d1, where d1 is the distance between the upper surface of the corbel and the foundation surface; d2 is the distance between the upper surface of the bottom plate and the foundation surface. That is, the effective height h0 of the section increases by d2-d1. Furthermore, since the cable is set in the punching cone, the cable can provide a certain punching resistance.

[0026] The punching shear resistance of column bases is higher than that of column bases without corbels and cables:

[0027] F = (0.5f) t +0.25σ pc，m )ηu m (d2-d2)+0.8f y A sbu

[0028] In the formula, f y —Design value of tensile strength of cable;

[0029] A sbu —The cross-sectional area of ​​all cables intersecting the oblique section of the cone that is punched at 45°.

[0030] Similarly, the calculation of the pull-out bearing capacity of column bases also takes into account the bearing capacity of the cables and the increase of the pull-out bearing capacity due to the prestress on them;

[0031] Regarding the seismic performance of column base joints, mechanical analysis shows that when a column tilts, at least one cable in a direction will increase its tension to generate a bending moment to resist the seismic bending moment. When the external load stops, the symmetrical cables will pull the column back to its initial position due to the imbalance of tension, i.e., the self-resetting function.

[0032] Bending moment generated by tension:

[0033] M s =f y A y l yv sinα y +f y A y l yl cosα y

[0034] The resultant horizontal force generated by the tension:

[0035] N s =f y A y sinα y

[0036] in:

[0037] A y —The cross-sectional area of ​​the cable for increased tension.

[0038] α y —The angle between the cable tension and the longitudinal axis of the member.

[0039] l yv l yl —These represent the vertical and horizontal distances from the point of application of the resultant force of the cable to the midpoint of the embedded part, respectively.

[0040] According to the system of equations:

[0041]

[0042] The formula for calculating the concrete bearing stress of embedded column bases in the "Technical Specification for Steel Structures of High-Rise Civil Buildings" can be derived:

[0043]

[0044] in:

[0045] V – Column base shear force

[0046] h0 — Distance from the inflection point of the column to the top surface of the foundation

[0047] d—Column base embedment depth

[0048] b f—Column base section width

[0049] x — Distance from the column base plate to the neutral axis

[0050] Therefore, the formula for calculating the embedment depth of embedded column bases is as follows:

[0051]

[0052] Applying the same principle to the effect of embedded column base nodes with prestressed cable-stayed external brackets and self-resetting irregular cross-sections, the embedment depth formula is as follows:

[0053]

[0054] This shows that it can effectively reduce the lower limit of burial depth.

[0055] Furthermore, the irregularly shaped cross-section steel tube concrete column has a cross-shaped, T-shaped, or L-shaped cross-section.

[0056] Beneficial effects: This invention provides corbels at the lower perimeter of irregularly shaped steel-concrete composite columns, with prestressed cables installed on the corbels. Both the corbels and cables are located within the foundation, effectively enhancing the connection between the column base joint and the surrounding foundation concrete. This improves the punching shear resistance and seismic resistance of the column base joint, thereby reducing the embedment depth of the embedded column base. Furthermore, the prestress in the cables allows the column base joint to have a certain self-resetting capability. Attached Figure Description

[0057] 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 undue limitation of the invention. In the drawings:

[0058] Figure 1 This is a schematic elevation view of the external corbel prestressed cable type self-resetting irregular cross-section embedded column base node described in an embodiment of the present invention;

[0059] Figure 2 This is a schematic diagram of the pre-embedded part of the external corbel prestressed cable type self-resetting irregular cross-section embedded column foot node according to an embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram of the corbel of the prestressed cable-stayed self-resetting irregular cross-section embedded column base node of the external corbel according to an embodiment of the present invention;

[0061] Figure 4 This is a schematic diagram of the precast steel component of the external corbel prestressed cable type self-resetting irregular cross section embedded column foot node (cross-shaped cross section) as described in an embodiment of the present invention;

[0062] Figure 5This is an isometric view of the external corbel prestressed cable type self-resetting irregular cross-section embedded column base node (T-shaped cross-section) described in an embodiment of the present invention;

[0063] Figure 6 This is an isometric view of the embedded column base node (L-shaped section) of the external corbel prestressed cable type self-resetting irregular cross section described in the embodiment of the present invention. Detailed Implementation

[0064] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0065] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0066] Example 1

[0067] See Figure 1-6 A self-resetting irregular cross-section embedded column base node with external corbel prestressed cable, comprising an irregular cross-section steel tube concrete column 1, wherein corbels 2 are provided on the lower four sides of the irregular cross-section steel tube concrete column 1, and cables 3 are prestressed and installed on the corbels 2. Both the corbels 2 and the cables 3 are located in the foundation 7 to enhance the connection capacity of the column base node.

[0068] This embodiment can effectively enhance the connection between the column base joint and the surrounding foundation concrete by adding corbels and cables, thereby improving the punching shear resistance and seismic resistance of the column base joint, thus achieving the purpose of reducing the embedment depth of the embedded column base. Furthermore, the prestress of the cables can give the column base joint a certain self-resetting ability.

[0069] In a specific example, the irregular cross-section steel tube concrete column 1 includes an irregular cross-section multi-cavity steel tube, and concrete is poured into the inner cavity of the irregular cross-section multi-cavity steel tube.

[0070] It should be noted that the irregular cross-section multi-cavity steel pipe in this embodiment is composed of multiple square steel pipes spliced ​​together, and concrete is poured inside the cavity of the square steel pipe to form the core concrete.

[0071] In a specific example, a column base plate 4 is welded to the bottom of the irregular cross-section multi-cavity steel pipe. The column base plate 4 has several openings at predetermined positions on the outer ring of the column base plate 4, corresponding to the inner cavity of the steel pipe. An anchor 5 is installed by matching the opening positions with the anchoring nut 6.

[0072] The central opening in the base plate of this embodiment allows the concrete inside the steel pipe to leak in and form an integral part of the foundation during pouring, preventing the foundation and the embedded column base from becoming independent of each other due to the partition of the base plate.

[0073] In practice, the size of the column base plate is larger than that of the irregular cross-section multi-cavity steel pipe. Ground anchors are installed on the column base plate on the outside of the steel-concrete composite column and fixed by anchor nuts. The ground anchors connect the base plate and the foundation, and the barbs of the ground anchors face outwards to further improve the connection strength of the structure.

[0074] In a specific example, the ground anchor 5 at the bottom of the column base plate 4 is located in the pre-embedded section foundation 71 of the foundation 7, the lower part of the cable 3 is located in the pre-embedded section foundation 71 of the foundation 7, and the corbel 2 is located in the post-embedded section foundation 72 of the foundation 7.

[0075] During on-site construction, the cables and ground anchors can be pre-positioned at the designed locations, and the foundation concrete of the embedded section can be poured. After the foundation concrete of the embedded section reaches the specified strength, the upper part of the cable can be connected to the corbel and prestressed anchored.

[0076] In a specific example, the irregular cross-section multi-cavity steel pipe, the column base plate 4, and the corbel 2 are all prefabricated steel components.

[0077] In this embodiment, the irregular cross-section multi-cavity steel pipe, column base plate, and corbel are all prefabricated steel components, which improves the on-site installation and construction efficiency of the column base joint.

[0078] In a specific example, the corbel 2 includes an upper flange plate 21, a web plate 22, a partition plate 23, and a lower flange plate 24. The web plate 22 is a vertical trapezoidal plate, and the partition plate 23, the upper flange plate 21, and the lower flange plate 24 are welded to the upper end and the left and right sides of the vertical trapezoidal plate, respectively. The outer wall of the steel pipe of the steel-concrete composite column 1 is welded to the upper flange plate 21, the web plate 22, and the lower flange plate 24.

[0079] In a specific example, the upper flange plate 21 is perpendicular to the outer wall of the steel pipe of the steel-concrete composite column 1, and the lower flange plate 24 is connected to the outer wall of the steel pipe of the steel-concrete composite column 1 at an angle downward. Both the upper flange plate 21 and the lower flange plate 24 are provided with a number of pre-set holes. The cable 3 passes through the pre-set holes of the lower flange plate 24 and the upper flange plate 21 of the corbel 2 in sequence, and is prestressed and anchored.

[0080] This embodiment, through a specially designed bracket and cable combination, achieves both the required stress on the column base and a simple structure that is easy to install and construct. At the same time, it can effectively enhance the connection performance between the column base and the foundation, reduce the embedment depth of the column base, and thus achieve the goal of saving costs.

[0081] In a specific example, the corbel 2 further includes a curved stiffening rib 25, which is provided with a plurality of curved stiffening ribs located between the lower flange plate 24 and the upper flange plate 21 and attached to the upper part of the cable 3 for use as a baffle.

[0082] It should be noted that in this embodiment, the web plate and the curved stiffening rib serve as the corbel reinforcement component and the baffle of the cable, respectively, to improve the structural strength;

[0083] In the specific implementation, from top to bottom, the curved stiffening ribs of this embodiment are curved outwards.

[0084] In a specific example, the punching shear capacity design of column base joints can be calculated according to the formulas in the "Code for Design of Concrete Structures GB 50010-2010":

[0085] F l ≤(0.5f t +0.25σ pc，m )ηu m h0

[0086] In the formula, η should be calculated according to the following two formulas, and the smaller value should be taken:

[0087]

[0088]

[0089] F l —Design values ​​for local loads;

[0090] β h — Cross-section height influence coefficient: When h is not greater than 800mm, take β. h The value is 1.0; when h is not less than 2000 mm, β is taken. h The value is 0.9, and values ​​are taken using linear interpolation.

[0091] f t —Design value of tensile strength of concrete;

[0092] σ pc，m —The effective prestressing stress of concrete in two directions along the perimeter of the calculated section is a length-weighted average value, which should be controlled within 1.0 N / mm². 2 ~3.5N / mm 2 Within the range;

[0093] u m —Calculate the perimeter of the section by taking the most unfavorable perimeter of the vertical section of the plate at a distance of h0 / 2 from the perimeter of the area where the local load or concentrated reaction force acts;

[0094] h0 — Effective height of the section, which is the average of the effective heights of the section reinforced in two directions.

[0095] According to the calculation of anti-punching in the specification, it can be determined that the corbel in this invention raises the punching starting surface from the bottom plate by d2-d1, where d1 is the distance between the upper surface of the corbel and the foundation surface; d2 is the distance between the upper surface of the bottom plate and the foundation surface. That is, the effective height h0 of the section increases by d2-d1. Furthermore, since the cable is set in the punching cone, the cable can provide a certain punching resistance.

[0096] The punching shear resistance of column bases is higher than that of column bases without corbels and cables:

[0097] F = (0.5f) t +0.25σ pc，m )ηu m (d2-d2)+0.8f y A sbu

[0098] In the formula, f y —Design value of tensile strength of cable;

[0099] A sbu —The cross-sectional area of ​​all cables intersecting the oblique section of the cone that is punched at 45°.

[0100] Similarly, the calculation of the pull-out bearing capacity of column bases also takes into account the bearing capacity of the cables and the increase of the pull-out bearing capacity due to the prestress on them;

[0101] Regarding the seismic performance of column base joints, mechanical analysis shows that when a column tilts, at least one cable in a direction will increase its tension to generate a bending moment to resist the seismic bending moment. When the external load stops, the symmetrical cables will pull the column back to its initial position due to the imbalance of tension, i.e., the self-resetting function.

[0102] Bending moment generated by tension:

[0103] M s =f y A y l yv sinα y +f y A y l yl cosα y

[0104] The resultant horizontal force generated by the tension:

[0105] N s =f y A y sinα y

[0106] in:

[0107] A y—The cross-sectional area of ​​the cable for increased tension.

[0108] α y —The angle between the cable tension and the longitudinal axis of the member.

[0109] l yv l yl —These represent the vertical and horizontal distances from the point of application of the resultant force of the cable to the midpoint of the embedded part, respectively.

[0110] According to the system of equations:

[0111]

[0112] The formula for calculating the concrete bearing stress of embedded column bases in the "Technical Specification for Steel Structures of High-Rise Civil Buildings" can be derived:

[0113]

[0114] in:

[0115] V – Column base shear force

[0116] h0 — Distance from the inflection point of the column to the top surface of the foundation

[0117] d—Column base embedment depth

[0118] b f —Column base section width

[0119] x — Distance from the column base plate to the neutral axis

[0120] Therefore, the formula for calculating the embedment depth of embedded column bases is as follows:

[0121]

[0122] Applying the same principle to the effect of embedded column base nodes with prestressed cable-stayed external brackets and self-resetting irregular cross-sections, the embedment depth formula is as follows:

[0123]

[0124] This shows that it can effectively reduce the lower limit of burial depth.

[0125] The special design of the bracket and cable in this embodiment can reduce the pre-embedding depth, and can ensure punching resistance and seismic resistance even at a low pre-embedding depth.

[0126] In a specific example, the irregularly shaped cross-section steel tube concrete column 1 has a cross-shaped, T-shaped, or L-shaped cross-section.

[0127] The on-site installation steps of the external corbel prestressed cable-stayed self-resetting irregular cross-section embedded column base node in this embodiment are as follows: First, a cup-shaped post-cast section is set up during on-site construction, and the cables and ground anchors are pre-arranged in the design position, and the foundation concrete of the pre-embedded section is poured; Second, when the foundation concrete of the pre-embedded section reaches the specified strength, the pre-fabricated irregular steel components are hoisted to the designated position, the ground anchors pass through the outer holes of the base plate and are fixed by anchor bolts; The cables pass through the pre-set holes of the lower flange plate and upper flange plate of the corbel in sequence, and are prestressed and anchored; Finally, the core concrete inside the steel pipe is poured to form the irregular cross-section steel pipe concrete and the post-cast section foundation concrete, forming the irregular cross-section CFST embedded column base node.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-resetting irregular cross-section embedded column base node with externally mounted corbel prestressed cable, characterized in that, The column includes an irregularly shaped cross-section steel-concrete composite column (1). The lower part of the irregularly shaped cross-section steel-concrete composite column (1) has brackets (2) extending outwards around its perimeter. The brackets (2) are prestressed and equipped with cables (3). The brackets (2) and cables (3) are both located in the foundation (7) to enhance the connection capacity of the column base joint. The brackets (2) include an upper flange plate (21), a web plate (22), a diaphragm plate (23), and a lower flange plate (24). The web plate (22) is a vertical trapezoidal plate. The upper end and the left and right sides of the vertical trapezoidal plate are respectively welded with the diaphragm plate (23), the upper flange plate (21), and the lower flange plate (24). The outer wall of the steel tube of the irregularly shaped cross-section steel-concrete composite column (1) is connected to the upper flange plate (21) and the web plate (22). The lower flange plate (24) is welded together. The upper flange plate (21) is perpendicular to the outer wall of the steel pipe of the irregular cross-section steel pipe concrete column (1). The lower flange plate (24) is connected to the outer wall of the steel pipe of the irregular cross-section steel pipe concrete column (1) in a downward angle. The upper flange plate (21) and the lower flange plate (24) are provided with several preset holes. The cable (3) passes through the preset holes of the lower flange plate (24) and the upper flange plate (21) of the corbel (2) in sequence, and is prestressed and anchored. The corbel (2) also includes curved stiffening ribs (25). The curved stiffening ribs (25) are provided with several of them located between the lower flange plate (24) and the upper flange plate (21) and are attached to the upper part of the cable (3) for baffle.

2. The externally mounted corbel prestressed cable-stayed self-resetting irregular cross-section embedded column base node according to claim 1, characterized in that, The irregular cross-section steel tube concrete column (1) includes an irregular cross-section multi-cavity steel tube, and concrete is poured into the inner cavity of the steel tube.

3. The externally mounted corbel prestressed cable-stayed self-resetting irregular cross-section embedded column base node according to claim 2, characterized in that, The bottom of the irregular cross-section multi-cavity steel pipe is welded with a column base plate (4). The column base plate (4) has a hole at the corresponding position of the inner cavity of the irregular cross-section multi-cavity steel pipe. Several holes are opened at a set position on the outer ring of the column base plate (4). A ground anchor (5) is installed by matching the hole position with the anchor nut (6).

4. The externally mounted corbel prestressed cable-stayed self-resetting irregular cross-section embedded column base node according to claim 3, characterized in that, The anchor (5) at the bottom of the column base plate (4) is located in the pre-embedded section foundation (71) of the foundation (7), the lower part of the cable (3) is located in the pre-embedded section foundation (71) of the foundation (7), and the corbel (2) is located in the post-embedded section foundation (72) of the foundation (7).

5. The externally mounted corbel prestressed cable-stayed self-resetting irregular cross-section embedded column base node according to claim 4, characterized in that, The irregular cross-section multi-cavity steel pipe, column base plate (4), and corbel (2) are all prefabricated steel components.

6. The externally mounted corbel prestressed cable type self-resetting irregular cross-section embedded column base node according to claim 1, characterized in that, The irregular cross-section steel tube concrete column (1) has a cross-shaped, T-shaped or L-shaped cross-section.

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