An outrigger beam embedded column foot structure and construction method for reducing the height of the pedestal

Abstract

A structure and construction method for an outward-extended beam embedded column foot for reducing the height of a cap, the structure includes a cap, a frame column, and a foundation pile, the frame column includes a steel section, the steel section at the root of the frame column is inserted into the cap, the foundation pile is symmetrically arranged below the cap with the frame column as the center, and the pile top passes through the cushion layer and is embedded in the bottom of the cap, the part of the steel section embedded in the cap is provided with an outward-extended steel section beam toward each surrounding foundation pile with its axis as the center, the cross-sectional shape of the outward-extended steel section beam is H-shaped or square tube-shaped, one end of each outward-extended steel section beam is fixedly connected to the steel section of the frame column to form an integral steel member with the steel section, and the other end extends to the top of the foundation pile head and makes its end extend through the center of the foundation pile; the steel section at the root of the frame column and the outward-extended steel section beam are supported on the cushion layer at the bottom through the supporting steel frame at the bottom thereof, and are cast in the cap with concrete as a whole. The present invention can solve the technical problem in the prior art that the cap height is too large, causing unnecessary waste and inconvenience in construction.

Description

Technical Field

[0001] The invention relates to the technical field of building structure design and civil construction, and in particular to an outrigger beam embedded column foot structure and a construction method for reducing the height of a cap. Background Art

[0002] Reasonable design of embedded column base nodes of composite structure columns or steel structure columns is the key to ensure the safety and reliability of the overall structural load-bearing. For composite structure frame columns, the current "Combined Structure Design Code" JGJ138 requires that the embedded column base of steel-concrete columns and rectangular steel tube concrete columns, the embedded depth of the steel in the foundation (including the foundation bottom plate or the pedestal) should not be less than 2.0 times the height of the column steel section; the embedded column base of circular steel tube concrete columns, the embedded depth of the steel in the foundation should not be less than 2.5 times the height of the column steel section. The standard atlas gives the embedded column base node method as shown in Figure 1. For steel structure columns, the current "Technical Code for Steel Structures of High-rise Civil Buildings" JGJ99 requires that the embedded depth of H-section columns should not be less than 2.0 times the height of the steel column section; the embedded depth of box columns should not be less than 2.5 times the long side of the steel column section; the embedded depth of circular columns should not be less than 3.0 times the outer diameter of the column. The standard atlas gives the following. Figure 2 The embedded column foot node method shown in the figure. The main purpose of the above regulations in the specification is twofold. The first is to effectively embed the frame column in the cap foundation by controlling the minimum embedding depth of the steel in the cap. The specification stipulates that the above requirements must be implemented when there is only one basement or no basement. The second is that when multiple pile caps are set under the column, the sufficient embedding depth can ensure that the internal force of the column is reliably transmitted to the cap and finally to the foundation piles through the bonding between the steel and the concrete, and the cap has sufficient rigidity to level the internal force shared between the foundation piles.

[0003] However, the cross-sectional form and size of the steel in the frame column need to be determined by calculation. If the cross-sectional size of the steel is large, the reference to the specifications and drawings will usually result in an excessively large cap height. Table 1 is a summary of the calculation formula for the buried depth of the steel of the frame column, the minimum buried depth structural requirements, and the minimum cap height according to the column foot node practices described in the current specifications and drawings. Table 2 lists the minimum cap height required for frame columns with different cross-sectional forms and different steel cross-sectional sizes (the long side size or outer diameter of the steel concrete column section is 1.0m, and the steel tube concrete column or steel column is 1.5m) that are often encountered in actual projects. However, actual structural calculations often do not require such a thick cap. That is, when the cross-sectional size of the steel is large, the cap height of the embedded column foot is mostly controlled by the buried depth requirements of the specification structure, which not only causes waste, but also increases the difficulty of construction due to the increase in the buried depth of the cap, which is even more inconvenient when encountering groundwater. In addition, the node practices given in the current specifications and atlas also require the installation of positioning bolts in order to ensure effective fixation during the construction of the column steel. The height of the pedestal where the positioning bolts are installed needs to be partially increased, that is, the height of the pedestal is further increased, and the pile head connection at the thickened slope is also more difficult to construct, as shown in Figure 1. Figure 2 shown.

[0004] Table 1 adopts the standard and atlas practices, the calculation formula for the embedded depth of frame column steel, the minimum embedded depth structural requirements and the minimum height of the pedestal

[0005]

[0006]

[0007] Note: 1. The column "Minimum height of the abutment at the locating bolt position" is the total height of the abutment height at the locating bolt position and the local deepening height.

[0008] 2. In the column “Calculation formula for buried depth of steel section”: h s is the buried depth of the steel; M is the design value of the bending moment of the embedded column foot; b r is the side length of the stirrups of the steel concrete column perpendicular to the calculated bending plane; b is the side length of the rectangular steel tube concrete column perpendicular to the calculated bending plane; D is the outer diameter of the steel tube; f c It is the design value of compressive strength of base concrete.

[0009] Table 2 Examples of minimum required heights of pedestals for frame columns of different cross-sections and steel sizes according to current specifications and atlas requirements

[0010]

[0011] Note: 1. In the "Steel Section Size" column, for cross-shaped steel: flange width x section width x web thickness x flange thickness; for H-shaped steel: flange width x section height x web thickness x flange thickness; for square tube: section length x section width x wall thickness; for round steel: outer diameter x wall thickness.

[0012] 2. The column "Calculate the required pedestal height according to the standard formula" is to calculate the required steel embedding depth according to the current "Code for Design of Composite Structures" JGJ138 formula (i.e. the "Steel embedding depth calculation formula" column in Table 1) based on the internal force at the bottom of the column.

[0013] 3. The calculation methods of “minimum buried depth requirements for steel sections”, “minimum height of pedestal” and “minimum height of pedestal at the location of the locating bolts” are shown in Table 1, where the locating bolts are considered to be d=30mm.

[0014] 4. In the "Steel Concrete" column, since the structural requirements for the minimum buried depth of steel sections are only related to the external dimensions of the steel sections, only the cross type is used as an example and the others are not elaborated on. Summary of the invention

[0015] In order to overcome the defects and shortcomings of the above-mentioned technology, the present invention provides a design and structure of an outrigger beam embedded column foot based on effectively reducing the height of the pedestal and transferring the internal force of the column to the foundation pile, which can solve the technical problems in the existing method that the height of the pedestal is too large to meet the standard construction requirements, resulting in unnecessary waste and inconvenience in construction.

[0016] The present invention adopts the following technical solutions:

[0017] The invention discloses an outward-extended beam embedded column base structure which reduces the height of a pedestal, comprising a pedestal, a frame column and foundation piles, wherein the frame column comprises a steel section, the steel section at the root of the frame column is inserted into the pedestal, the foundation piles are symmetrically arranged below the pedestal with the frame column as the center, and the pile tops thereof pass through the cushion layer and are embedded in the bottom of the pedestal, and the portion of the steel section embedded in the pedestal is provided with an outward-extended steel section beam centered on its axis toward each of the surrounding foundation piles, the cross-sectional shape of the outward-extended steel section beam is H-shaped or square tube-shaped, one end of each of the outward-extended steel section beams is fixedly connected to the steel section of the frame column to form an integral steel member with the steel section, and the other end extends to the top of the foundation pile head and has its end extending through the center of the foundation pile; the steel section and the outward-extended steel section beam at the root of the frame column are supported on the cushion layer at the bottom by a supporting steel frame at the bottom thereof, and are cast in the pedestal as a whole with concrete.

[0018] The frame column is a steel-concrete column, including an internal steel section in the center of the column and column longitudinal steel bars on the periphery thereof; above the top surface of the pedestal, column stirrups are arranged on the periphery of the internal steel section of the frame column and are tied and fixed with the column longitudinal steel bars; the portion of the column longitudinal steel bars inserted into the pedestal is anchored above the overhanging steel beam; a plurality of closed reinforcing stirrups are arranged on the periphery of the portion of the internal steel section of the frame column buried in the pedestal, and the reinforcing stirrups are tied and fixed with the portion of the column longitudinal steel bars anchored in the pedestal.

[0019] The built-in steel is a cross-shaped steel, including a column web plate that crosses orthogonally and a column flange plate that is vertically connected at its end. The part of the cross-shaped steel buried in the pedestal is provided with a gusset plate along the annular direction between the column flange plates, and the gusset plate and the column flange plate together enclose a closed polygonal steel pipe column;

[0020] A cap steel reinforcement rib plate is arranged between the upper flange of the extended steel beam and the top surface of the cap at the position corresponding to the upper steel bars of the cap; the cap steel reinforcement rib plate is supported and welded by the vertical stiffening plates at equal intervals around the built-in steel at the lower part; in the closed polygonal steel pipe column, a horizontal stiffening partition is arranged at the position corresponding to the cap steel reinforcement rib plate and at the upper flange and lower flange of the extended steel beam respectively, and the periphery of the stiffening partition is connected to the column web, column flange plate and the inner wall of the tie plate by strong welding; ventilation holes and grouting holes are arranged on the stiffening partition.

[0021] The built-in steel is a square steel tube or a round steel tube;

[0022] A cap steel reinforcement rib plate is arranged between the upper flange of the extended steel beam and the top surface of the cap at a position corresponding to the upper steel bars of the cap; the cap steel reinforcement rib plate is supported and welded by the vertical stiffening plates that surround the built-in steel at equal intervals at its lower part; a horizontal stiffening partition is arranged in the square steel pipe or round steel pipe corresponding to the position of the cap steel reinforcement rib plate and at the upper flange and lower flange of the extended steel beam, and the periphery of the stiffening partition is connected to the inner wall of the steel pipe of the built-in steel with equal strength welding; ventilation holes and grouting holes are arranged on the stiffening partition.

[0023] The bottom of the column longitudinal reinforcement is welded to the top surface of the upper flange of the extended steel beam through a mechanical connection sleeve or a column longitudinal reinforcement lap plate, and beam transverse stiffening ribs are arranged between the upper flange and the lower flange of the extended steel beam corresponding to the position of the mechanical connection sleeve or the column longitudinal reinforcement lap plate. The beam transverse stiffening ribs are arranged on both sides of the web of the extended steel beam with the same width as the side flange and the same height as the web.

[0024] The frame column is a steel tube concrete column, which includes an external steel section and plain concrete inside it; the external steel section is a square steel tube or a round steel tube; a cap steel bar rib plate is arranged between the upper flange of the extended steel beam and the top surface of the cap corresponding to the position of the upper steel bar of the cap; the cap steel bar rib plate is supported and welded and fixed by vertical stiffening plates at equal intervals around the external steel section at its lower part; a horizontal stiffening partition is arranged in the steel tube of the external steel section at the position of the cap steel bar rib plate and at the upper flange and lower flange of the extended steel beam, and the periphery of the stiffening partition is connected to the inner wall of the steel tube of the external steel section by equal strength welding; ventilation holes and grouting holes are arranged on the stiffening partition.

[0025] The frame column is a steel column, the steel section is the steel column, and the steel column is a square steel tube or a round steel tube; a cap steel bar rib plate is arranged between the upper flange of the extended steel beam and the top surface of the cap corresponding to the position of the upper steel bar of the cap; the cap steel bar rib plate is supported and welded and fixed by the vertical stiffening plates at equal intervals around the steel column at its lower part; a horizontal stiffening partition is arranged in the steel tube of the steel column corresponding to the position of the cap steel bar rib plate and at the upper flange and lower flange of the extended steel beam, and the periphery of the stiffening partition is connected to the inner wall of the steel tube of the steel column by equal strength welding; ventilation holes and grouting holes are arranged on the stiffening partition.

[0026] A construction method for an outrigger beam embedded column foot structure for reducing the height of a cap, comprising the following steps:

[0027] 1) The outrigger steel beam and the column root of the steel section are welded into an integral steel component in the factory;

[0028] 2) First, construct foundation piles on the ground, then dig a groove to the bottom of the concrete cushion layer and cast the concrete cushion layer, lay a cap waterproof layer and a waterproof protective layer on the concrete cushion layer, and the pile head of the foundation pile passes through the concrete cushion layer and is embedded in the bottom of the cap to be cast, and then lay a supporting steel frame on the cap waterproof layer and the waterproof protective layer of the cushion layer, corresponding to the center position of the steel section of the frame column to be constructed;

[0029] 3) transporting the steel structure in step 1) to the site and hoisting it as a whole onto the supporting steel frame in step 2), adjusting the position and then reliably fixing it;

[0030] 4) Tie up the steel bars of the foundation, and then pour the concrete at the base of the foundation and frame columns from bottom to top.

[0031] The present invention has the following positive and beneficial effects:

[0032] The node approach of the present invention solves the problem of large pedestal height under the premise of fully ensuring reliable force transmission from axially compressed or eccentrically compressed frame columns to each foundation pile, and provides reference design principles. Combined with the provision of a supporting steel frame to temporarily support the frame column steel during the construction phase (since the supporting function is mainly borne by the concrete column foot after the concrete solidifies, the supporting function of the supporting steel frame is temporary), the positioning bolts and the local thickening of the pedestal are eliminated. According to actual engineering tests, the column foot node is safe, reasonable, effective and easy to construct. By applying the approach of the present invention, the pedestal design of the composite structure frame column or steel structure frame column can get rid of the dilemma of being forced to increase the pedestal height due to the buried depth requirement in the past. It has strong versatility and can be used as a corresponding supplement to the current specifications and atlases, and provide reference and reference for related projects in the future.

[0033] Compared with the current specifications and drawings, the height of the pedestal of the present invention is significantly reduced, the construction difficulty is reduced, and the construction period is shortened accordingly. Although the amount of steel is increased to a certain extent, the amount of concrete and the amount of excavation and filling are saved, so the overall project cost does not increase. Generally speaking, a relatively satisfactory effect is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1(a) and Figure 1(b) are the embedded column foot nodes of steel concrete columns as shown in the current "Design Code for Composite Structures" JGJ138;

[0035] Figure 2 It is the embedded column foot node of steel tube concrete column or steel column as shown in the current Technical Code for Steel Structures of High-rise Civil Buildings JGJ99;

[0036] FIG3 (a1) is a plan view of the embedded column foot node of the steel concrete column of the present invention;

[0037] FIG3( a2 ) is a cross-sectional view taken along line AA of FIG3( a1 );

[0038] FIG3( b1 ) is a plan view of the embedded column foot node of the steel tube concrete column of the present invention;

[0039] FIG3( b2 ) is a cross-sectional view of the BB position of FIG3( b1 );

[0040] FIG3 (c1) is a plan view of the embedded column foot node of the steel column in the present invention;

[0041] FIG3( c2 ) is a cross-sectional view of the CC position of FIG3( c1 );

[0042] FIG. 4( a ) and FIG. 4( b ) are diagrams showing the calculation of the extended steel beam at the embedded column foot node in the present invention;

[0043] FIG5( a ) is a schematic diagram of the connection of the column longitudinal reinforcement through a mechanical connection sleeve when the anchorage length in the cap is insufficient in the present invention;

[0044] FIG5( b ) is a schematic diagram of the column longitudinal reinforcement of the present invention being connected by welding through the reinforcement plate when the anchorage length in the cap is insufficient;

[0045] FIG6 (a1) is a plan view of the embedded column foot node at position a of Example 1 of the present invention;

[0046] Fig. 6(a2) is a cross-sectional view of the DD position of Fig. 6(a1);

[0047] FIG6(a3) is a plan view of the position of the steel reinforcement slab of the cap in FIG6(a1);

[0048] FIG6(a4) is a vertical view of the position of the reinforcement plate of the cap in FIG6(a1);

[0049] FIG6 (b1) is a plan view of the embedded column foot node at b in Example 1 of the present invention;

[0050] Fig. 6(b2) is a cross-sectional view of the EE position of Fig. 6(b1);

[0051] FIG6(b3) is a plan view of the position of the reinforcement plate of the cap in FIG6(b1);

[0052] FIG. 7 ( a1 ) is a plan view of the embedded column foot node at a of the second embodiment of the present invention;

[0053] Fig. 7(a2) is a cross-sectional view of the FF position of Fig. 7(a1);

[0054] FIG. 7 ( b1 ) is a plan view of the embedded column foot node at b in the second embodiment of the present invention;

[0055] FIG7( b2 ) is a cross-sectional view of the GG position of FIG7( b1 );

[0056] FIG7( b3 ) is a cross-sectional view of the HH position of FIG7( b1 ).

[0057] Figure numbers: 1-cap, 2-frame column, 3-foundation pile, 4-concrete cushion, 5-extending steel beam, 51-upper flange, 52-lower flange, 6-supporting steel frame, 7-reinforcing partition, 8-air vent, 9-grouting hole, 10-column longitudinal reinforcement, 11-column stirrups, 12-reinforcement stirrups, 13-column flange plate, 14-stitching plate, 15-column web, 16-cap steel bar lap plate, 17-vertical stiffening plate, 18-mechanical connection sleeve, 19-column longitudinal reinforcement lap plate, 20-beam transverse stiffening rib, 22-anchor bolt, 23-ground beam, 24-steel, 26-bolt. DETAILED DESCRIPTION

[0058] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0059] The following examples are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the following description, and these obvious changes or modifications derived from the spirit of the present invention are still within the scope of protection of the present invention.

[0060] Referring to the figures, in particular to Figures 3(a1), 3(a2), 3(b1), 3(b2), 3(c1), and 3(c2), an outrigger beam embedded column foot structure with reduced cap height includes a cap, a frame column, and a foundation pile, wherein the frame column includes a steel section, and the steel section at the root of the frame column is inserted into the cap, and the foundation pile 3 is symmetrically arranged below the cap 1 with the frame column 2 as the center, and the pile top passes through the cushion layer 4 and is embedded in the bottom of the cap 1, and the steel section 24 is embedded in the cap 1 with its axis An extended steel beam 5 is arranged from the center to the surrounding piles 3. The cross-sectional shape of the extended steel beam 5 is H-shaped or square tube-shaped. One end of each extended steel beam 5 is fixedly connected to the steel 24 of the frame column 2 to form an integral steel member with the steel 24, and the other end extends to the top of the pile 3 and its end extends through the center of the pile 3; the steel 24 at the root of the frame column 2 and the extended steel beam 5 are supported on the cushion layer 4 at the bottom through the supporting steel frame 6 at the bottom, and are cast in the base 1 with concrete as a whole.

[0061] Referring to Figure 3(a1) and Figure 3(a2), the frame column 2 is a steel-concrete column, including an internal steel section in the center of the column and a column longitudinal reinforcement 10 on the periphery thereof; above the top surface of the pedestal 1, column stirrups 11 are arranged on the periphery of the internal steel section of the frame column 2 and are tied and fixed to the column longitudinal reinforcement 10; the portion of the column longitudinal reinforcement 10 inserted into the pedestal 1 is anchored above the overhanging steel beam 5; a plurality of closed reinforcing stirrups 12 are arranged on the periphery of the portion of the internal steel section of the frame column 2 buried in the pedestal 1, and the reinforcing stirrups 12 are tied and fixed to the portion of the column longitudinal reinforcement 10 anchored in the pedestal.

[0062] Referring to FIG. 3 (a1), the built-in steel is a cross-shaped steel, including a column web 15 orthogonally crossed and a column flange plate 13 vertically connected at its end. The cross-shaped steel embedded in the cap 1 is provided with a gusset plate 14 along the annular direction between the column flange plates 13. The gusset plate 14 and the column flange plates 13 together enclose a closed polygonal steel pipe column.

[0063] Referring to Fig. 3(a2), a cap steel reinforcement rib plate 16 is provided between the upper flange 51 of the extended steel beam 5 and the top surface of the cap 1 at the position corresponding to the upper steel bar of the cap; the cap steel reinforcement rib plate 16 is supported and welded by vertical stiffening plates 17 of the built-in steel at equal intervals at its lower part; in the closed polygonal steel pipe column, a horizontal stiffening partition plate 7 is provided at the position corresponding to the cap steel reinforcement rib plate 16 and at the upper flange 51 and the lower flange 52 of the extended steel beam 5, respectively, and the periphery of the stiffening partition plate 7 is connected to the inner wall of the column web plate 15, the column flange plate 13 and the gusset plate 14 by equal strength welding; the stiffening partition plate 7 is provided with air holes 8 and grouting holes 9.

[0064] The built-in steel is a square steel tube or a round steel tube;

[0065] A cap steel reinforcement rib plate 16 is provided between the upper flange 51 of the extended steel beam 5 and the top surface of the cap 1 at a position corresponding to the upper reinforcement of the cap; the cap steel reinforcement rib plate 16 is supported and welded and fixed by vertical stiffening plates 17 of the built-in steel at equal intervals at its lower part; a horizontal stiffening partition plate 7 is provided in the square steel pipe or round steel pipe corresponding to the position of the cap steel reinforcement rib plate 16, and at the upper flange 51 and the lower flange 52 of the extended steel beam 5, respectively, and the periphery of the stiffening partition plate 7 is connected to the inner wall of the steel pipe of the built-in steel with equal strength welding; the stiffening partition plate 7 is provided with air holes 8 and grouting holes 9.

[0066] The bottom of the column longitudinal reinforcement 10 is welded to the top surface of the upper flange 51 of the extended steel beam 5 through a mechanical connection sleeve 18 or a column longitudinal reinforcement lap plate 19, and beam transverse stiffening ribs 20 are arranged between the upper flange 51 and the lower flange 52 of the extended steel beam 5 corresponding to the position of the mechanical connection sleeve 18 or the column longitudinal reinforcement lap plate 19. The beam transverse stiffening ribs 20 are arranged on both sides of the web of the extended steel beam 5 with the same width as the side flange and the same height as the web.

[0067] The frame column 2 is a steel tube concrete column, which includes an external steel section and plain concrete inside it; the external steel section is a square steel tube or a round steel tube; a cap steel bar rib plate 16 is arranged between the upper flange 51 of the extended steel beam 5 and the top surface of the cap 1 at the position of the upper steel bar of the cap; the cap steel bar rib plate 16 is supported and welded and fixed by vertical stiffening plates 17 that surround the external steel section at equal intervals at its lower part; a horizontal stiffening partition 7 is arranged in the steel tube of the external steel section at the position of the cap steel bar rib plate 16 and at the upper flange 51 and the lower flange 52 of the extended steel beam 5, and the periphery of the stiffening partition 7 is connected to the inner wall of the steel tube of the external steel section by equal strength welding; the stiffening partition 7 is provided with air holes 8 and grouting holes 9.

[0068] The frame column 2 is a steel column, the steel section 24 is the steel column, and the steel column is a square steel tube or a round steel tube; a cap steel bar rib plate 16 is arranged between the upper flange 51 of the extended steel beam 5 and the top surface of the cap 1 at the position of the upper steel bar of the cap; the cap steel bar rib plate 16 is supported and welded and fixed by the vertical stiffening plates 17 at equal intervals around the steel column at its lower part; a horizontal stiffening partition 7 is arranged in the steel tube of the steel column at the position of the cap steel bar rib plate 16 and at the upper flange 51 and the lower flange 52 of the extended steel beam 5, and the periphery of the stiffening partition 7 is connected to the inner wall of the steel tube of the steel column by equal strength welding; the stiffening partition 7 is provided with air holes 8 and grouting holes 9.

[0069] A construction method for an outrigger beam embedded column foot structure for reducing the height of a cap, comprising the following steps:

[0070] 1) The outrigger steel beam 5 and the column root portion of the steel section 24 are welded into an integral steel member in the factory;

[0071] 2) First, construct foundation piles 3 on the ground, then dig a groove to the bottom of a concrete cushion layer 4 and cast the concrete cushion layer 4, lay a cap waterproof layer and a waterproof protective layer on the concrete cushion layer 4, and the pile head of the foundation pile 3 passes through the concrete cushion layer 4 and is embedded in the bottom of the cap 1 to be cast, and then lay a support steel frame 6 on the cap waterproof layer and the waterproof protective layer of the cushion layer 4, corresponding to the center position of the steel 24 of the frame column 2 to be constructed;

[0072] 3) transporting the steel structure in step 1) to the site and hoisting it as a whole onto the supporting steel frame 6 in step 2), adjusting the position and then reliably fixing it;

[0073] 4) Tie up the foundation reinforcement, and then pour the concrete at the base of foundation 1 and frame column 2 from bottom to top.

[0074] The invention is suitable for the design and construction of a house with only one basement or no basement, with a multi-pile cap foundation, and with an embedded composite structure column foot or a steel structure column foot with a larger cross-sectional size.

[0075] The embedded column foot node of the present invention is made as follows:

[0076] (1) The open steel section is closed into a closed section within the height range of the pedestal through an annular tie plate; the tie plate and the flange of the column steel should be connected by a full penetration groove weld. (2) An extended steel beam is set between the column steel and the center line of the surrounding piles. The cross-section of the extended steel beam can be H-shaped or square tube-shaped. The flange of the H-shaped and square tube-shaped extended steel beam and the column flange or tie plate should be connected by a full penetration groove weld. The web of the H-shaped extended steel beam and the column flange or tie plate can be connected by a partial penetration weld. (3) The pedestal steel reinforcement slab is set at the position of the upper steel bar of the pedestal, and is supported and welded by the vertical stiffening plates welded around the frame column steel at equal intervals at its lower part. The pedestal steel reinforcement slab is strongly welded to the steel flange of the cross steel or the outer wall of the tie plate, the outer wall of the square tube or round tube steel, etc. The present invention lists the embedded column foot node samples of steel-concrete columns (see Figure 3 (a1), Figure 3 (a2)), steel tube concrete columns (see Figure 3 (b1), Figure 3 (b2)) and steel columns (see Figure 3 (c1), Figure 3 (c2)) after adopting the method of the present invention. The construction of the column foot node is recommended as follows: (1) A supporting steel frame (as shown in Figure 3) is laid on the foundation cushion layer to replace the positioning bolts, thereby eliminating the local thickening part of the pedestal; the supporting steel frame ensures the positioning and stability of the steel structure before the pedestal concrete solidifies. (2) The extended steel beam and the steel column foot of the frame column are welded in the factory, transported to the site as a whole and hoisted into place. The position of the column splicing joint can be taken at 1.0m-1.3m above the top of the pedestal.

[0077] The following two purposes are achieved by adopting the method of the present invention: (1) reducing the embedding depth of the steel section and thus reducing the height of the pedestal. Referring to the relevant provisions of the mechanical anchoring of steel bars, the author suggests that the minimum embedding depth of the steel section can be 0.6 times the standard requirement. Considering the height of the supporting steel frame of 500 mm, the corresponding minimum embedding depth structural requirements of the steel section and the minimum height of the pedestal are adjusted as shown in Table 3.

[0078] Table 3 Calculation formula for buried depth of steel section, minimum buried depth structural requirements and minimum height of pedestal after adopting the method of the present invention

[0079]

[0080] Note: 1. The minimum buried depth requirement of steel section is 0.6 times of the standard. Please note that only the minimum buried depth requirement should be adjusted, and the buried depth calculation formula of the standard should not be adjusted. The column foot nodes are designed according to the present invention in each example as shown in Table 2, and the results are shown in Table 4.

[0081] Table 4 Examples of minimum heights of caps required according to the present invention under different cross-sectional frame columns and steel sizes

[0082]

[0083] Note: 1. The calculation methods of “calculating the required pedestal height according to the standard formula”, “structural requirements for the minimum buried depth of steel sections” and “minimum pedestal height” are shown in Table 3.

[0084] 2. Other notes are the same as Table 2.

[0085] After adopting the method of the present invention, except for the steel concrete column, the height of the pedestal is significantly reduced. When the internal force at the bottom of the column is not large, the embedding depth can be controlled by the result obtained by the standard calculation formula in some cases.

[0086] Table 5 Comparison of the height of the pedestal using the method of the present invention and the method of the standard atlas

[0087]

[0088] Note: 1. “None” means that the height of the pedestal is not optimized by adopting the method of the present invention.

[0089] (2) Effectively transfer the internal force of the frame column to the foundation pile. Usually, the internal force at the bottom of the frame column is relatively large. When there are multiple pile caps, the method of the present invention can effectively transfer the internal force at the bottom of the frame column to the top of the pile through the extended steel beam, and the force transmission path is clear.

[0090] The following issues should also be noted when applying the method of the present invention: (1) As mentioned above, the purpose of controlling the embedding depth of the steel beam in the pedestal is to ensure the embedding requirements of the frame column. Therefore, for axially compressed or eccentrically compressed columns, the author recommends the use of the method of the present invention; however, for axially or eccentrically tensile columns, because the concrete thickness between the extended steel beam and the top surface of the pedestal is small after the height of the pedestal is reduced, the concrete on the top of the pedestal may be damaged under the action of tension, so it is still recommended to use the method described in the specification. Under normal circumstances, the proportion of structural tension columns is relatively small, and the method of the present invention can be applied to most frame columns in engineering. (2) The design of the extended steel beam can be conservative and carried out as follows. First, the reaction force of each foundation pile is calculated according to the internal force at the bottom of the frame column, and then the extended steel beam is verified according to the cantilever beam section with the column bottom position fixed, the foundation pile position free, and the foundation pile vertical reaction force loaded to the end of the beam, as shown in Figures 4(a) and 4(b). The detailed verification formula and process can be referred to the existing reference books, and will not be repeated in this invention. In the figure, L0 is the distance from the center of the foundation pile to the root of the connection between the extended steel beam and the column steel. When calculating, we can be conservative and ignore the beneficial effect of concrete. The bearing capacity of the extended steel beam section and its connection with the frame column can be verified according to the pure steel beam section. According to practical experience, the cross-sectional dimensions of the extended steel beam are generally large, and the bearing requirements can be met by the pure steel beam verification. If the bearing capacity of the extended steel beam is insufficient, the connection position of the steel beam and the column steel can be treated by a variable section plus axil. The width-to-thickness ratio of the flange and web of the extended steel beam should refer to the width-to-thickness ratio limit of the steel in the steel-concrete beam in the current "Combined Structure Design Code" JGJ138. (3) As the column foot node is the key stress bearing part, it is recommended to set shear studs 26 on the upper and lower flanges of the extended steel. The diameter of studs 26 should not be less than 16mm and the length should not be less than 4d (d is the stud diameter); the spacing along the beam axis should not exceed 200mm and should not be less than 6d, the spacing perpendicular to the beam axis should not exceed 200mm and should not be less than 4d, and the distance from studs 26 to the flange edge should not be less than 50mm. (4) Horizontal stiffening partitions should be set on the part of the frame column steel corresponding to the extended steel beam flange, and concrete grouting holes with a diameter of not less than 200mm should be opened according to construction needs; groove butt welds should be used between the partition and the column steel flange, and partial penetration welds or fillet welds can be used between the partition and the column web. (5) If the steel structure column foot node is heavy, the frame column steel can also be welded into the corresponding cantilever beam section according to the relevant specifications and drawings, and the extended steel beam and the column foot node can be spliced ​​on site. (6) The extended steel beam must extend beyond the center of the pile by no less than 200 mm. In addition, the steel bars anchored into the cap at the top of the pile must be bent to avoid the extended steel beam.(7) When the frame column is a steel-concrete column, the column longitudinal reinforcement should be anchored in the pedestal, and the height from the top surface of the extended cross beam to the top surface of the pedestal should meet the requirements of the column reinforcement anchorage length. At this time, the column longitudinal reinforcement should extend to the top of the upper flange of the extended steel beam and be bent. The length after bending should not be less than 6d (dcolumn is the diameter of the column longitudinal reinforcement) and not less than 120mm; when the height from the top surface of the extended cross beam to the top surface of the pedestal does not meet the above requirements, the column longitudinal reinforcement should be bent around, a mechanical connection sleeve should be provided on the upper flange of the extended steel, or a rib plate should be welded, and full-height stiffening ribs should be added on both sides of the web of the extended steel at the corresponding position (see Figure 5 (a) and Figure 5 (b)). (8) According to experience, the steel-concrete embedded steel is usually slightly smaller than the steel tube concrete column steel and steel column steel. Therefore, the effect of reducing the pedestal height by adopting the method of the present invention is relatively small, and the effect on the steel tube concrete column and the steel structure column is relatively large. In the case of multiple pile caps, all types of structural forms can play the role of frame columns in distributing and transferring internal forces to each foundation pile.

[0091] Embodiment 1

[0092] The land for a certain vehicle depot is an irregular rectangle, 950m long from north to south and 440m wide from east to west; the land area is about 28.01 hectares. The parking and train inspection depot, joint maintenance depot, throat area and surrounding roads in the yard adopt a plan of sinking 5.0m as a whole. The depot area and throat area are covered with non-residential buildings such as office or commercial buildings. The entire depot area, throat area and entry and exit lines are planned to be divided into 10 structural units. Among them, some frame columns in the joint maintenance depot area 3, parking and train inspection depot area 4 and throat areas 5 and 6 are made of steel-concrete components, and steel tube concrete components are used in throat area 7. The above-mentioned composite structural components are all designed with embedded column foot nodes according to the present invention. Here, one example of a steel-concrete frame column in area a of the parking and train inspection depot 4 is listed, see Figure 6 (a1), Figure 6 (a2), Figure 6 (a3), Figure 6 (a4); one example of a steel tube concrete frame column in area b of area 7 is listed, see Figure 6 (b1), Figure 6 (b2), Figure 6 (b3).

[0093] Table 5 Basic dimension parameters of embedded column foot node frame column, pedestal and extended steel used in the design of the present invention

[0094]

[0095] Note: 1. When the cross-sectional dimensions in the "Frame Column Section" column are square columns: section length x section width, when they are round columns: outer diameter; when the cross-sectional dimensions in the "Column Internal Steel Section" column are cross-shaped: flange width x section width x web thickness x flange thickness, when they are round tubes: outer diameter x wall thickness.

[0096] 2. The steel beam size in the "Extended Steel Beam" column is H-type: flange width x section height x web thickness x flange thickness.

[0097] 3. Materials: Frame column concrete C50; Cap foundation concrete C35; Steel Q345B; Steel HRB400.

[0098] It can be seen from the above table that the cross-sectional dimensions of the steel sections of the medium-sized steel-concrete columns of the vehicle section in this embodiment are relatively large, and some of them are steel tube concrete columns. Therefore, after the embedded column foot nodes are designed by the method of the present invention, not only the height of the pedestal is significantly reduced, but also the problem of the frame column transmitting internal forces to each foundation pile when there are multiple pile pedestals can be solved.

[0099] Embodiment 2

[0100] The west side of a certain vehicle depot is the throat area, the middle part is the joint inspection depot and the operating depot (a two-story car garage is developed above the operating depot); the east and north sides are the turnaround line, and the south side of the operating depot is the test line; the living area is between the east turnaround line and the depot area. Residential buildings are developed on the depot area, and the entire depot area and the throat area are planned to be divided into 17 structural units. The frame columns of some of the partitions of the joint maintenance depot A1-1, A1-2, A2-1, A2-2, A3-1, and A3-2 are steel-concrete components, and the embedded column base nodes are designed according to the method of the present invention. Here is an example of the steel-concrete frame column base node at a in the A2-1 area of ​​the joint maintenance depot, see. Figure 7(a1) , 7(a2) ; An example of the steel-concrete frame column base node at location b in area A2-2, see Figure 7(b1), Figure 7(b2), and Figure 7(b3).

[0101] Table 6 Basic dimension parameters of embedded column foot node frame column, pedestal and extended steel used in the design of the present invention

[0102]

[0103] Note: Materials: frame column concrete C60; cap foundation concrete C40; steel Q345B; steel HRB400. Other notes are the same as Table 5.

[0104] Since the cross-sectional size of the steel-concrete column of the vehicle section in this embodiment is not large, the height of the pedestal is not reduced by adopting the method of the present invention, but the local thickening of the pedestal at the positioning bolt is still eliminated and the problem of the multi-pile pedestal frame column transmitting internal force to each foundation pile is solved.

Claims

1. An outrigger beam embedded column foot structure for reducing the height of a cap, comprising a cap, a frame column, and a foundation pile, wherein the frame column comprises a steel section, and the steel section at the root of the frame column is inserted into the cap, characterized in that: The foundation piles (3) are symmetrically arranged below the pedestal (1) with the frame column (2) as the center, and the pile tops pass through the cushion layer (4) and are embedded in the bottom of the pedestal (1). The portion of the steel section (24) buried in the pedestal (1) is provided with an extended steel beam (5) around each of the foundation piles (3) with its axis as the center. The cross-sectional shape of the extended steel beam (5) is H-shaped or square tube-shaped. One end of each of the extended steel beams (5) is fixedly connected to the steel section (24) of the frame column (2) to form an integral steel structure with the steel section (24), and the other end extends to the top of the pile head of the foundation pile (3) and its end extends through the center of the foundation pile (3); the steel section (24) and the extended steel beam (5) at the base of the frame column (2) are supported on the cushion layer (4) at the bottom through the supporting steel frame (6) at the bottom thereof, and are cast in the pedestal (1) as a whole with concrete.

2. The outrigger beam embedded column foot structure for reducing the height of the pedestal as claimed in claim 1, characterized in that: The frame column (2) is a steel-concrete column, comprising an internal steel profile at the center of the column and a column longitudinal steel bar (10) on the periphery thereof; above the top surface of the pedestal (1), column stirrups (11) are arranged on the periphery of the internal steel profile of the frame column (2) and are tied and fixed to the column longitudinal steel bar (10); the portion of the column longitudinal steel bar (10) inserted into the pedestal (1) is anchored above the overhanging steel beam (5); a plurality of closed reinforcing stirrups (12) are arranged on the periphery of the portion of the internal steel profile of the frame column (2) buried in the pedestal (1), and the reinforcing stirrups (12) are tied and fixed to the portion of the column longitudinal steel bar (10) anchored in the pedestal.

3. The outrigger beam embedded column foot structure for reducing the height of the pedestal as claimed in claim 2, characterized in that: The built-in steel is a cross-shaped steel, comprising a column web (15) that crosses orthogonally and a column flange plate (13) whose ends are vertically connected. The portion of the cross-shaped steel buried in the pedestal (1) is provided with a gusset plate (14) along the annular direction between the column flange plates (13). The gusset plate (14) and the column flange plate (13) together enclose a closed polygonal steel pipe column. A cap steel reinforcement rib plate (16) is arranged between the upper flange (51) of the extended steel beam (5) and the top surface of the cap (1) at the position corresponding to the upper steel bars of the cap; the cap steel reinforcement rib plate (16) is supported and welded by the vertical stiffening plates (17) at equal intervals around the inner steel section at its lower part; a horizontal stiffening partition (7) is arranged in the closed polygonal steel pipe column at the position corresponding to the cap steel reinforcement rib plate (16) and at the upper flange (51) and the lower flange (52) of the extended steel beam (5); the periphery of the stiffening partition (7) is connected to the column web (15), the column flange plate (13) and the inner wall of the tie plate (14) by equal strength welding; the stiffening partition (7) is provided with air holes (8) and grouting holes (9).

4. The outrigger beam embedded column foot structure for reducing the height of the pedestal as claimed in claim 2, characterized in that: The built-in steel is a square steel tube or a round steel tube; A cap steel reinforcement rib plate (16) is arranged between the upper flange (51) of the extended steel beam (5) and the top surface of the cap (1) at the position corresponding to the upper steel bars of the cap; the cap steel reinforcement rib plate (16) is supported and welded fixed by the vertical stiffening plates (17) surrounding the built-in steel at equal intervals at its lower part; a horizontal stiffening partition (7) is arranged in the square steel tube or round steel tube at the position corresponding to the cap steel reinforcement rib plate (16) and at the upper flange (51) and lower flange (52) of the extended steel beam (5), and the periphery of the stiffening partition (7) is connected to the inner wall of the steel tube of the built-in steel by equal strength welding; and the stiffening partition (7) is provided with air holes (8) and grouting holes (9).

5. The outrigger beam embedded column foot structure for reducing the height of the pedestal as claimed in claim 3 or 4, characterized in that: The bottom of the column longitudinal reinforcement (10) is welded to the top surface of the upper flange (51) of the extended steel beam (5) through a mechanical connection sleeve (18) or a column longitudinal reinforcement slab (19), and beam transverse stiffening ribs (20) are arranged between the upper flange (51) and the lower flange (52) of the extended steel beam (5) at the position corresponding to the mechanical connection sleeve (18) or the column longitudinal reinforcement slab (19), and the beam transverse stiffening ribs (20) are arranged on both sides of the web of the extended steel beam (5) with the same width as the side flange and the same height as the web.

6. The outrigger beam embedded column foot structure for reducing the height of the pedestal as claimed in claim 1, characterized in that: The frame column (2) is a steel tube concrete column, which includes an external steel section and plain concrete inside the column; the external steel section is a square steel tube or a round steel tube; a cap steel reinforcement slab (16) is arranged between the upper flange (51) of the extended steel beam (5) and the top surface of the cap (1) at the position corresponding to the upper steel bars of the cap; the cap steel reinforcement slab (16) is supported and welded fixed by vertical stiffening plates (17) at equal intervals around the external steel section at its lower part; a horizontal stiffening partition (7) is arranged in the steel tube of the external steel section at the position corresponding to the cap steel reinforcement slab (16) and at the upper flange (51) and the lower flange (52) of the extended steel beam (5), and the periphery of the stiffening partition (7) is connected to the inner wall of the steel tube of the external steel section by equal strength welding; and the stiffening partition (7) is provided with air holes (8) and grouting holes (9).

7. The outrigger beam embedded column foot structure for reducing the height of the pedestal as claimed in claim 1, characterized in that: The frame column (2) is a steel column, the steel section (24) is the steel column, and the steel column is a square steel tube or a round steel tube; a cap steel reinforcement slab (16) is arranged between the upper flange (51) of the extended steel beam (5) and the top surface of the cap (1) at the position corresponding to the upper steel bars of the cap; the cap steel reinforcement slab (16) is supported and welded and fixed by vertical stiffening plates (17) at the lower part thereof which surround the steel column at equal intervals; a horizontal stiffening partition (7) is arranged in the steel tube of the steel column at the position corresponding to the cap steel reinforcement slab (16) and at the upper flange (51) and the lower flange (52) of the extended steel beam (5), and the periphery of the stiffening partition (7) is connected to the inner wall of the steel tube of the steel column by equal strength welding; the stiffening partition (7) is provided with air holes (8) and grouting holes (9).

8. The construction method of the outrigger beam embedded column foot structure for reducing the height of the cap as claimed in claim 1, characterized in that: The following steps are involved: 1) welding the outrigger steel beam (5) and the column root portion of the section steel (24) into an integral steel member in the factory; 2) first construct foundation piles (3) on the ground, then dig a groove to the bottom of a concrete cushion layer (4) and cast the concrete cushion layer (4), lay a cap waterproof layer and a waterproof protective layer on the concrete cushion layer (4), and the pile head of the foundation pile (3) passes through the concrete cushion layer (4) and is embedded in the bottom of the cap (1) to be cast, and then lay a supporting steel frame (6) on the cap waterproof layer and the waterproof protective layer of the cushion layer (4) corresponding to the center position of the steel (24) of the frame column (2) to be constructed; 3) transporting the steel structure in step 1) to the site and hoisting the steel structure as a whole onto the supporting steel frame (6) in step 2), adjusting the position and then reliably fixing the steel structure; 4) Tie up the cap reinforcement, and then pour concrete at the base of the cap (1) and frame column (2) from bottom to top.

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