A CFST-RC column with pbl stiffening member isosceles node and construction method thereof

Abstract

The application relates to a CFST-RC column equal-section joint with a PBL stiffening component and a construction method thereof, which comprises a concrete-filled steel tube column, a reinforced concrete column and a reinforced concrete beam, the concrete-filled steel tube column comprises a steel tube, a plurality of PBL stiffening steel plates are distributed on the inner wall of the steel tube in a ring direction, the PBL stiffening steel plates are vertical, and the PBL stiffening steel plates are perpendicular to the inner wall of the steel tube; shear ring bars are arranged at different heights in the steel tube, and each shear ring bar horizontally penetrates all the PBL stiffening steel plates. The application has the beneficial effects that the pressure acting on the internal concrete can be directly transmitted to the lower reinforced concrete of the joint; the pressure borne by the steel tube is partially transmitted to the end plate arranged in the steel tube and then transmitted to the lower reinforced concrete of the joint by the end plate, and the other part is transmitted to the PBL stiffening steel plate welded with the inner wall of the steel tube; at this time, the PBL stiffening steel plate bears the upper pressure and directly acts on the part of the pressure transmitted by the steel tube.

Description

Technical Field

[0001] This invention belongs to the field of steel structure and composite structure, and particularly relates to a CFST-RC column with PBL stiffening member and its construction method. Background Technology

[0002] Large landmark buildings such as airport terminals, waiting halls, large convention centers, and cultural complexes have large roof spans, complex loads, and stringent requirements for utilizing the above-ground space. Therefore, they require fewer load-bearing structures, resulting in larger and more complex internal forces in the load-bearing structures beneath the roof, demanding higher performance from these structures. In contrast, the load-bearing structures of the substructures, such as basements, experience smaller and simpler loads, but must still meet durability requirements while considering cost and construction factors. Therefore, these buildings often employ a load-bearing structure consisting of steel-concrete composite columns on top and reinforced concrete columns below.

[0003] The transition joints between steel-concrete composite columns and reinforced concrete columns can be categorized into embedded, end-bearing, and enclosed types. Embedded joints extend the upper steel pipe by at least several times its diameter and embed it into the lower foundation or frame. The deep embedment of the steel pipe likely affects the distribution of reinforcement within the foundation. End-bearing joints connect the bottom end plate of the steel pipe to the lower structure using bolts or continuous reinforcing bars, thus requiring high precision during on-site construction. Enclosed joints are similar to embedded joints, but feature a larger bottom concrete cross-section that encloses the steel pipe.

[0004] Although the above-mentioned column transfer joints can meet the strength and basic usage requirements, summarizing the characteristics of these column transfer joints reveals that, under the same load conditions, the cross-sectional area of ​​a concrete column is larger than that of a steel-concrete composite column. In addition, some steel-concrete composite column transfer joints use haunches at the joint to improve the joint strength, which results in inconsistent cross-sectional areas between the upper and lower columns, irregular cross-sectional shapes at the column transfer joint location, insufficient aesthetics, and problems such as complex construction, greater construction difficulty, and greater material waste. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a CFST-RC column with equal cross-section joint and its construction method.

[0006] This type of CFST-RC column with PBL stiffeners includes: concrete-filled steel tube columns, reinforced concrete columns, and reinforced concrete beams. The concrete-filled steel tube column includes a steel tube with several PBL stiffening steel plates distributed circumferentially on the inner wall of the steel tube. The PBL stiffening steel plates are vertical and perpendicular to the inner wall of the steel tube. Shear reinforcement rings are provided at different heights inside the steel tube, and each shear reinforcement ring horizontally penetrates all the PBL stiffening steel plates.

[0007] The reinforced concrete column includes longitudinal reinforcement bars that extend to the top of the steel tube concrete column. The longitudinal reinforcement bars are welded to the PBL stiffening steel plate. The cross-sectional dimensions of the steel tube concrete column and the reinforced concrete column are the same.

[0008] The bottom end of the PBL stiffening steel plate extends below the steel pipe, and the beam reinforcement cage of the reinforced concrete beam is located within the height range of the PBL stiffening steel plate below the steel pipe.

[0009] Preferably, the PBL stiffening steel plate has holes for shear reinforcement bars to pass through, and the diameter of the holes is larger than the cross-sectional diameter of the shear reinforcement bars.

[0010] Preferably, the bottom end of the steel pipe is provided with an end plate, which is annular and has several holes arranged circumferentially. The PBL stiffening steel plate and the longitudinal reinforcement pass through the holes, and the size of the holes is larger than the cross-sectional size of the PBL stiffening steel plate and the longitudinal reinforcement. The bottom end of the PBL stiffening steel plate extends below the bottom end of the steel pipe.

[0011] As a preferred embodiment, several stirrups are provided on the longitudinal reinforcement below the PBL stiffening steel plate, and the bottom end of the longitudinal reinforcement is bent outward at the bottom end of the reinforced concrete column.

[0012] The construction method for this type of CFST-RC column with PBL stiffener and equal cross-section joint includes the following steps:

[0013] S1. Holes are made in the PBL stiffening steel plate according to the design position of the shear reinforcement ring;

[0014] S2. Weld the PBL stiffening steel plate into the steel pipe and install shear reinforcement rings;

[0015] S3. Weld the longitudinal reinforcement bars to the stiffening steel plate, and set stirrups on the longitudinal reinforcement bars of the reinforced concrete column.

[0016] S4: Insert the reinforcing cage of the reinforced concrete beam under the steel pipe concrete column and arrange the corresponding structure.

[0017] S5: Erect the cast-in-place formwork for reinforced concrete columns and reinforced concrete beams, and simultaneously pour concrete for steel pipe concrete columns, reinforced concrete columns, and reinforced concrete beams until curing is completed.

[0018] As a preferred option, an end plate is welded to the bottom of the steel pipe. The end plate has holes cut into it according to the design position of the PBL stiffening steel plate. The longitudinal ribs extend through the holes and into the steel pipe to be welded to the stiffening steel plate.

[0019] The method for calculating the bearing capacity of CFST-RC column constant section joints with PBL stiffeners is as follows:

[0020] Nu =f y A e '+f c A c

[0021] Among them, f y A represents the design value for the compressive strength of steel. e ' is the cross-sectional area of ​​the steel in the concrete-filled steel tube column; f c A represents the standard value of concrete compressive strength. c A is the cross-sectional area of ​​the reinforced concrete column; e The formula for calculating ' is:

[0022] A' e =b e td+∑A se

[0023]

[0024]

[0025] In the formula: b e Where λ is the equivalent thickness of the PBL stiffening steel plate, and λ is the flexibility coefficient. σ cr t represents the critical buckling stress of the steel, and t represents the thickness of the PBL stiffening steel plate. Then b e =ρt, where ρ is the effective width reduction factor, t is the thickness of the PBL stiffening steel plate, and n s The number of PBL stiffening plates installed inside the steel pipe, d is the width of the PBL stiffening plate, ρ i and b i These are the effective width reduction factor and equivalent thickness of a single PBL stiffening steel plate, respectively.

[0026] As a preferred option, the formula for calculating the critical buckling stress of steel is:

[0027]

[0028] The limit for the width-to-thickness ratio of steel pipe wall is

[0029]

[0030] In the formula, μ and E are Poisson's ratio and elastic modulus of steel, respectively, b is the thickness of steel pipe, k is the buckling coefficient of steel pipe, r1 is the outer radius of steel pipe, and r2 is the inner radius of steel pipe.

[0031] The beneficial effects of this invention are:

[0032] 1) The stress mechanism of the node in this invention is clear. The pressure is jointly borne by the steel pipe, the PBL stiffening steel plate, and the concrete inside the steel pipe. The pressure acting on the internal concrete can be directly transmitted to the reinforced concrete below the node. Part of the pressure borne by the steel pipe is transmitted to the end plate set inside the steel pipe and then to the reinforced concrete below the node. The other part is transmitted to the PBL stiffening steel plate welded to the inner wall of the steel pipe. At this time, the PBL stiffening steel plate bears part of the pressure transmitted directly from the upper pressure to the steel pipe. Part of the internal force of the PBL stiffening steel plate is directly transmitted to the reinforced concrete extending to the lower part of the node, and the other part is transmitted to the longitudinal reinforcement welded to it.

[0033] 2) By extending the longitudinal reinforcement bars directly into the steel-concrete composite column, the upper steel-concrete composite column and the lower reinforced concrete column can meet the performance requirements while having the same cross-sectional area. This not only improves the aesthetics but also increases space utilization, avoids material waste, and meets the dual carbon goals of energy conservation and emission reduction.

[0034] 3) This invention sets up simultaneous casting of steel pipe concrete columns, reinforced concrete columns and reinforced concrete beams, which is simple in structure and less affected by the construction environment. Compared with existing column conversion nodes, it can effectively shorten the construction period and reduce the overall construction cost. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the entire node.

[0036] Figure 2 A schematic diagram of the internal reinforcement bars of a reinforced concrete column and a reinforced concrete beam;

[0037] Figure 3 A schematic diagram of the joint structure connecting a steel-concrete composite column and a reinforced concrete column;

[0038] Figure 4 This is a diagram of the internal structure of a steel-concrete composite column.

[0039] Explanation of reference numerals in the attached drawings: 1. Concrete-filled steel tube column; 2. Reinforced concrete column; 3. Reinforced concrete beam; 101. Steel pipe; 102. PBL stiffening steel plate; 103. Shear ring reinforcement; 104. Continuous longitudinal reinforcement; 105. End plate; 106. Stirrups; 107. Beam reinforcement cage. Detailed Implementation

[0040] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0041] Example 1

[0042] As one example, such as Figures 1 to 4 As shown, this CFST-RC column with PBL stiffening members includes: a steel tube concrete column 1, a reinforced concrete column 2, and a reinforced concrete beam 3. The steel tube concrete column 1 includes a steel tube 101. Several PBL stiffening steel plates 102 are evenly distributed circumferentially on the inner wall of the steel tube 101. The PBL stiffening steel plates 102 are vertical and welded perpendicular to the inner wall of the steel tube 101.

[0043] Shear reinforcement 103 is provided at different heights inside the steel pipe 101, and each shear reinforcement 103 horizontally penetrates all PBL stiffening steel plates 102; holes for the shear reinforcement 103 to pass through are equally spaced on the PBL stiffening steel plates 102, and the diameter of the holes is larger than the cross-sectional diameter of the shear reinforcement 103, which is beneficial to fill the holes during concrete pouring, strengthen the bond between the concrete and the steel pipe 101, and make the interface shear force more effectively transferred between the steel pipe 101 and the concrete.

[0044] The bottom end of the steel pipe 101 is provided with an end plate 105. The end plate 105 is annular and has several holes circumferentially arranged on the end plate 105. The PBL stiffening steel plate 102 and the longitudinal rib 104 pass through the holes, and the size of the holes is larger than the cross-sectional size of the PBL stiffening steel plate 102 and the longitudinal rib 104. The bottom end of the PBL stiffening steel plate 102 extends below the bottom end of the steel pipe 101.

[0045] The reinforced concrete column 2 includes a continuous longitudinal bar 104, the top of which extends to the top of the steel tube concrete column 1. The continuous longitudinal bar 104 and the PBL stiffening steel plate 102 are welded together, so that the continuous longitudinal bar 104, the PBL stiffening steel plate 102 and the steel pipe 101 form an integral whole. The bottom end of the PBL stiffening steel plate 102 replaces the steel pipe and is embedded in the lower concrete. The upper steel tube concrete column 1 and the lower reinforced concrete column 2 have the same cross-sectional dimensions. This design solves many problems caused by non-uniform cross-sections in most interfaces. At the same time, it has the advantages of simple structure, shallow embedment depth, no impact on the distribution of internal reinforcement of the foundation, strengthening the bond between the steel pipe 101 and the concrete, convenient construction, and high aesthetics.

[0046] The longitudinal reinforcement 104 below the PBL stiff steel plate 102 is provided with several stirrups 106 spot welded to form an integral whole. The bottom end of the longitudinal reinforcement 104 bends outward at the bottom end of the reinforced concrete column 2 to improve its tensile strength.

[0047] The beam reinforcement cage 107 of the reinforced concrete beam 3 is located within the height range of the PBL stiffening steel plate 102 below the steel pipe 101.

[0048] Example 2

[0049] As another embodiment, this second embodiment, based on the first embodiment, proposes a construction method for CFST-RC column equal section joints with PBL stiffening members, including the following steps:

[0050] S1. Holes are made in the PBL stiffening steel plate 102 according to the design position, spacing, diameter and other information of the shear ring reinforcement 103; end plate 105 is welded to the bottom end of steel pipe 101, and the end plate 105 has holes made according to the design position of PBL stiffening steel plate 102.

[0051] S2. Weld the PBL stiffening steel plate 102 into the steel pipe 101 and set the shear circumferential reinforcement 103.

[0052] S3. Weld the longitudinal reinforcement 104 to the rigid steel plate 102. The longitudinal reinforcement 104 passes through the hole on the end plate 105 and extends into the steel pipe 101 to be welded to the rigid steel plate 102. Stirrups 106 are set on the longitudinal reinforcement 104 in the reinforced concrete column 2 section.

[0053] S4: Insert the beam reinforcement cage 107 of the reinforced concrete beam 3 under the steel pipe concrete column 1 and arrange the corresponding structure.

[0054] S5: Erect the cast-in-place formwork for reinforced concrete column 2 and reinforced concrete beam 3, and simultaneously pour concrete for steel pipe concrete column 1, reinforced concrete column 2 and reinforced concrete beam 3 until curing is completed.

[0055] Example 3

[0056] As another embodiment, this third embodiment, based on embodiments one and two, proposes a method for calculating the bearing capacity of CFST-RC column equal section joints with PBL stiffening members, including calculating the cross-sectional bearing capacity of columns with equal section transfer joints of steel pipes with PBL stiffening plates:

[0057] The formula for the axial compressive bearing capacity of the column in this node is an extension of the following formula:

[0058] N u =f y A e +f c A c

[0059] Where: N u For bearing capacity; f y A represents the design value for the compressive strength of steel. e f is the cross-sectional area of ​​the steel. c A represents the standard value of concrete compressive strength. c This represents the cross-sectional area of ​​the concrete.

[0060] Based on the above formula, this invention proposes a formula for calculating the bearing capacity of CFST-RC columns with equal cross-section joints and PBL stiffeners:

[0061] N u =f y A e '+f c A c

[0062] Where μ is the bearing capacity equivalence coefficient; f y A represents the design value for the compressive strength of steel. e , where f is the cross-sectional area of ​​the steel in the concrete-filled steel tube column 1; c A represents the standard value of concrete compressive strength. c The lower concrete cross-sectional area, i.e. the concrete cross-sectional area of ​​reinforced concrete column 2; now, the calculation formula for the bearing capacity of the CFST-RC equal cross-section transition node column is derived.

[0063] For this node:

[0064] A' e =b e td+∑A se

[0065]

[0066]

[0067] In the formula: b e Where λ is the equivalent thickness of the steel plate, and λ is the flexibility coefficient. σ cr Let be the critical buckling stress of the steel, and t be the thickness of the steel plate. Then b e =ρt, where ρ is the effective width reduction factor, d is the width of the PBL stiffening steel plate 102, ρ i and b i These are the effective width reduction factor and equivalent thickness of a single PBL stiffening steel plate 102, respectively.

[0068]

[0069] In the formula, μ and E are Poisson's ratio and elastic modulus of steel, μ is the thickness of steel pipe 101, k is the buckling coefficient of steel pipe 101, r1 is the outer radius of the circular steel pipe, and r2 is the inner radius of the circular steel pipe.

[0070] The limit for the width-to-thickness ratio of steel pipe wall is

[0071]

[0072] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 1 can be referred to each other, and will not be repeated in this application.

[0073] Example 4

[0074] As another embodiment, this fourth embodiment, based on the third embodiment, proposes that in a CFST-RC column with equal cross-section joints and PBL stiffeners, the concrete strength is C50, E c =34500MPa, steel pipe 101 is of type Q355, outer diameter r1=900mm, plate thickness 25mm, steel elastic modulus is 206000MPa, Poisson's ratio μ=0.3, the number of PBL stiffening steel plates 102 installed inside steel pipe 101 is n. s =8, PBL stiffening steel plate 102 has dimensions of 400mm×25mm.

[0075] The radius of the opening on the PBL stiffening steel plate 102 is r0 = 20mm, the center depth of the opening is u0 = 85mm, the center-to-center distance of the PBL stiffening steel plate 102 is 120mm, a transverse diaphragm is installed 1m inside the column, and the number of openings on each PBL stiffening steel plate 102 is n = 6.

[0076] The elastic stiffness of a single-hole PBL

[0077]

[0078] Spring constant

[0079] c=k / l=270940 / 120=2257MPa

[0080] PBL stiffened steel plate 102 surface stiffness:

[0081] D = Et 3 / 2[12(1-μ 2 )]=206000×25 3 / 2×[12(1-0.3 2 )]=295kN·m

[0082] PBL stiffening plate wiring stiffness

[0083]

[0084] Relative stiffness of single-limb PBL stiffening steel plate 102:

[0085]

[0086] 2753 > 2177, therefore the PBL stiffened steel plate 102 belongs to the stiffened PBL plate category.

[0087] The concrete area is:

[0088] A c =3.14 × 875 2 -8×(400×25)=2324062mm 2

[0089] Substitute the corresponding numbers into the formula:

[0090]

[0091] σ cr =426MPa. Then

[0092]

[0093] b e =0.87×25=21.75mm; that is, the effective area of ​​the steel pipe and PBL is:

[0094]

[0095] A' e =8 × 21.75 × 400 + 900 2 ×3.14=261300mm 2 .

[0096] The bearing capacity of the column section of the PBL stiffened steel pipe equal cross-section transfer node of the present invention is: N u =10671kN.

[0097] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 3 can be referred to each other, and will not be repeated in this application.

[0098] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

Claims

1. A CFST-RC column uniform section joint with PBL stiffener, characterized in that, The CFST-RC column with PBL stiffeners includes the following cross-section nodes: concrete-filled steel tube column, reinforced concrete column, and reinforced concrete beam. The concrete-filled steel tube column includes a steel tube with several PBL stiffening steel plates distributed circumferentially on the inner wall of the steel tube. The PBL stiffening steel plates are vertical and perpendicular to the inner wall of the steel tube. Shear reinforcement rings are provided at different heights inside the steel tube, and each shear reinforcement ring horizontally penetrates all the PBL stiffening steel plates. The reinforced concrete column includes longitudinal reinforcement bars that extend to the top of the steel tube concrete column. The longitudinal reinforcement bars are welded to the PBL stiffening steel plate. The cross-sectional dimensions of the steel tube concrete column and the reinforced concrete column are the same. The bottom end of the PBL stiffening steel plate extends below the steel pipe, and the beam reinforcement cage of the reinforced concrete beam is located within the height range of the PBL stiffening steel plate below the steel pipe. In the method for calculating the bearing capacity of the CFST-RC column with PBL stiffener and uniform cross-section joint, the formula for calculating the bearing capacity of the CFST-RC column with PBL stiffener and uniform cross-section joint is as follows: ； in, This refers to the design value of the compressive strength of the steel. The cross-sectional area of ​​the steel in the concrete-filled steel tube column; This refers to the standard value of concrete compressive strength. This represents the cross-sectional area of ​​the reinforced concrete column. The calculation formula is ； ； ； In the formula: Equivalent thickness of PBL stiffening steel plate The flexibility coefficient, , This refers to the critical buckling stress of steel. The thickness of the stiffening steel plate for PBL; ,but , This is the effective width reduction factor. For PBL stiffening steel plate thickness, The number of PBL stiffening steel plates to be installed inside the steel pipe. The width of the stiffening steel plate for PBL. and These are the effective width reduction factor and equivalent thickness of a single PBL stiffening steel plate, respectively.

2. The CFST-RC column uniform section joint with PBL stiffener as described in claim 1, characterized in that, The PBL stiffening steel plate has holes for shear reinforcement rings to pass through, and the diameter of the holes is larger than the cross-sectional diameter of the shear reinforcement rings.

3. The CFST-RC column uniform section joint with PBL stiffener as described in claim 1, characterized in that, The bottom end of the steel pipe is provided with an end plate, which is annular and has several holes in the circumferential direction. The PBL stiffening steel plate and the longitudinal reinforcement pass through the holes, and the size of the holes is larger than the cross-sectional size of the PBL stiffening steel plate and the longitudinal reinforcement. The bottom end of the PBL stiffening steel plate extends below the bottom end of the steel pipe.

4. The CFST-RC column uniform section joint with PBL stiffener as described in claim 1, characterized in that, Several stirrups are provided on the longitudinal reinforcement below the PBL stiffening steel plate, and the bottom end of the longitudinal reinforcement is bent outward at the bottom end of the reinforced concrete column.

5. The CFST-RC column uniform section joint with PBL stiffener as described in claim 1, characterized in that, The formula for calculating the critical buckling stress of steel is: ； The limit for the width-to-thickness ratio of steel pipe wall is ； In the formula , These are Poisson's ratio and elastic modulus of steel, respectively. For the thickness of the steel pipe, The buckling coefficient of the steel pipe is... The outer radius of the steel pipe, The radius is the inner radius of the steel pipe.

6. The construction method for CFST-RC column equal section joints with PBL stiffeners as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Holes are made in the PBL stiffening steel plate according to the design position of the shear reinforcement ring; S2. Weld the PBL stiffening steel plate into the steel pipe and install shear reinforcement rings; S3. Weld the longitudinal reinforcement bars to the stiffening steel plate, and set stirrups on the longitudinal reinforcement bars of the reinforced concrete column. S4: Insert the reinforcing cage of the reinforced concrete beam under the steel pipe concrete column and arrange the corresponding structure. S5: Erect the cast-in-place formwork for reinforced concrete columns and reinforced concrete beams, and simultaneously pour concrete for steel pipe concrete columns, reinforced concrete columns, and reinforced concrete beams until curing is completed.

7. The construction method for the CFST-RC column with equal cross-section joint with PBL stiffener as described in claim 6, characterized in that, The bottom end of the steel pipe is welded with an end plate. The end plate has holes opened according to the design position of the PBL stiffening steel plate. The longitudinal ribs extend through the holes and into the steel pipe to be welded to the stiffening steel plate.

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