A concrete-filled steel tube column and a calculation method for compressive strength

Abstract

The present invention discloses a concrete-filled steel tube column and a calculation method for compressive strength. The concrete-filled steel tube column includes a steel tube and a steel skeleton member arranged inside the steel tube. Concrete is poured inside the steel tube and the steel skeleton to form a composite section. The steel skeleton member includes annular steel sheets, longitudinal stiffening plates, and cross connecting plates. Each annular steel sheet is welded to the longitudinal stiffening plate as a whole, and the annular steel sheets are connected to form a whole through longitudinal stiffening plates, cross connecting plates, gusset plates, and bolts. Spiral stirrups are arranged on the outer side of the steel skeleton member. End plates are provided at both ends of the steel skeleton member, and connecting plates are provided on the inner walls at both ends of the steel tube. The steel tube and the steel skeleton member are connected through gusset plates and bolts. By arranging a steel skeleton member inside the concrete-filled steel tube column, the present invention utilizes the outer steel tube and the internal steel skeleton to enhance the double restraint effect on the core concrete, effectively improving the stiffness and load-bearing capacity of the concrete-filled steel tube column; at the same time, the inner steel skeleton can effectively reduce the influence of concrete shrinkage.

Description

Technical Field

[0001] The present invention relates to a concrete-filled steel tube column and a method for calculating the compressive strength, and belongs to the technical field of steel tube tower design. Background Art

[0002] Concrete-filled steel tube is a composite member formed by pouring concrete inside a steel tube. Under the action of an axial load, the concrete-filled steel tube member will undergo axial compression deformation. Due to the Poisson effect, the concrete expands laterally under compression, and the steel tube will restrain the expansion deformation of the concrete, thereby exerting a lateral restraint on the concrete and improving the strength and ductility of the concrete. The filled concrete can also prevent the steel tube from buckling prematurely. Therefore, under axial compression, the concrete-filled steel tube structure can give full play to the combined action of the outer steel tube and the filled concrete, showing good load-bearing capacity and deformation capacity. At the same time, the outer steel tube can also serve as a construction formwork, greatly advancing the construction speed and having significant economic benefits.

[0003] In recent years, with the higher requirements for the load-bearing capacity of concrete-filled steel tube members, relevant scholars have proposed concrete-filled steel tube members with internal stiffeners, that is, adding stiffeners in the core concrete on the basis of concrete-filled steel tube members. On the one hand, the internal stiffeners can effectively increase the strength and stiffness of the composite column; on the other hand, the concrete surrounding the internal stiffeners can prevent the stiffeners from buckling locally; the inner steel skeleton can also prevent the concrete from generating shrinkage cracks. Therefore, the concrete-filled steel tube members with internal stiffeners can effectively utilize the common action among the outer steel tube, the core concrete, and the internal stiffeners to improve the load-bearing capacity of the members on the basis of the good mechanical properties of the concrete-filled steel tube members. At the same time, after placing the stiffeners in the concrete-filled steel tube, even if the outer wall steel tube loses its load-bearing capacity due to fire, the internal stiffeners can still maintain a certain load-bearing capacity and prevent the concrete from spalling, effectively improving the problem of poor fire resistance of ordinary concrete-filled steel tubes. At present, the internal stiffeners of concrete-filled steel tube members are mainly steel bars, profiled steel, steel tubes, etc. Common cross-sections of concrete-filled steel tube members with internal stiffeners include those with internal steel bars, internal steel tubes, internal angle steels, internal multiple steel tube rectangular forms, and internal cross-shaped profiled steels. Due to the different forms of the stiffeners, the mechanical properties of each concrete-filled steel tube member are different. Most of the existing types of steel skeleton concrete-filled steel tube columns are suitable for high-rise building structures. Due to the special structure system of the transmission steel tube tower and the complex field construction environment. In view of the characteristics of large load on the main members of the legs of the long-span transmission tower, complex external forces on the load, and complex construction environment, there is an urgent need for a concrete-filled steel tube column cross-section type with good load-bearing performance and convenient processing and installation. Summary of the Invention

[0004] The object of the present invention is to provide a concrete-filled steel tube column and a calculation method for compressive strength. By arranging a steel skeleton member inside the concrete-filled steel tube column, the double restraint effect on the core concrete is enhanced by means of the outer steel tube and the internal steel skeleton, effectively improving the stiffness and load-bearing capacity of the concrete-filled steel tube column.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a concrete-filled steel tube column, including a steel tube and a steel skeleton member disposed inside the steel tube. Concrete is cast inside the steel tube and the steel skeleton member to form a composite section.

[0007] The steel skeleton member includes a circular steel sheet, longitudinal stiffening plates and cross connecting plates.

[0008] The circular steel sheet is longitudinally arranged along the inner side of the steel tube and is of the same length as the steel tube.

[0009] The longitudinal stiffening plates are perpendicular to the circular steel sheet, and the longitudinal stiffening plates are arranged longitudinally along the inner side of the circular steel sheet and are welded integrally with the circular steel sheet.

[0010] A cross connecting plate is arranged at the center of the steel tube. The cross connecting plates are longitudinally distributed inside the steel tube, and the cross connecting plates are fixedly connected with the longitudinal stiffening plates.

[0011] Spiral stirrups are arranged on the outer side of the steel skeleton member. The spiral stirrups are arranged along the inner side of the steel tube and are of the same length as the steel tube. The spiral stirrups are welded to the outer surface of the circular steel sheet.

[0012] The head and tail ends of the steel skeleton member are respectively fixedly connected to the head and tail ends of the steel tube.

[0013] Further, there are 4 circular steel sheets and longitudinal stiffening plates each, and they are evenly distributed along the axial direction of the steel tube.

[0014] Further, the cross connecting plates and the longitudinal stiffening plates are fixedly connected through first gusset plates and first bolts.

[0015] Further, the longitudinal distance between adjacent cross connecting plates is 1 m to 2 m.

[0016] Further, end plates are arranged at the head and tail ends of the steel skeleton member; the end plates are welded to the outer side of the circular steel sheet;

[0017] Connection plates are provided at the head and tail ends of the steel tube; the connection plates are welded to the inner wall of the steel tube;

[0018] The end plates at both ends of the steel skeleton member are respectively connected to the connection plates at both ends of the steel tube through second gusset plates and second bolts to fix the steel skeleton member inside the steel tube.

[0019] Furthermore, the steel materials of the steel pipe, the annular steel sheet, the longitudinal stiffening plate, the cross connecting plate, the end plate, the connecting plate and the second joint plate are any one of Q355, Q390, Q420 and Q460.

[0020] Furthermore, the second bolt is a 6.8 - grade or 8.8 - grade rough - made bolt.

[0021] The present invention also provides a method for calculating the compressive strength of a concrete - filled steel tube column, including:

[0022] Calculating the equivalent reinforcement area \(A_{s}\) according to the spiral stirrup arrangement in the concrete - filled steel tube column described in any one of claims 1 to 7 sso :

[0023]

[0024] wherein, \(d\) s is the diameter of the annular steel skeleton, \(A_{ss}\) ss is the cross - sectional area of the spiral stirrup, and \(s\) is the spacing between adjacent turns of the spiral stirrup;

[0025] Calculating the sectional confinement coefficient \(\theta\) according to the steel tube cross - sectional area \(A\) s , the concrete area \(A_{c}\) c , and the equivalent area \(A_{s}\) of the spiral stirrup sso : y :

[0026]

[0027] wherein, \(f_{y}\) v is the tensile strength of the spiral stirrup, \(f_{c}\) c is the compressive strength of the internal concrete, and \(f\) is the design value of the compressive strength of the steel tube;

[0028] Calculating the design value \(f_{cc}\) of the compressive strength of the concrete - filled steel tube section according to the confinement coefficient \(\theta\) y : sc :

[0029]

[0030] wherein, \(B\) is the influence coefficient of the steel grade on the confinement effect, and \(C\) is the influence coefficient of the concrete grade on the confinement effect;

[0031] Calculating the axial compressive strength bearing capacity \(N_{0}\) of the concrete - filled steel tube column according to the steel tube area \(A\) s , the concrete area \(A_{c}\) c , the internal steel skeleton area \(A_{s}\) b and the design value \(f_{cc}\) of the compressive strength of the concrete - filled steel tube section: sc \(N_{0}=(A\)

[0032] \(N_{0}=(A\) s+A c )f sc +A b f b ,

[0033] Among them, f b is the design value of the compressive strength of the circular steel pipe.

[0034] The beneficial effects of the present invention are as follows:

[0035] The present invention provides a concrete-filled steel tube column and a calculation method for compressive strength. By arranging a steel skeleton member inside the concrete-filled steel tube column, the double restraint effect on the core concrete is improved by using the outer steel tube and the internal steel skeleton, effectively improving the stiffness and bearing capacity of the concrete-filled steel tube column. At the same time, the internal steel skeleton can effectively reduce the influence of concrete shrinkage. The compressive strength calculation method of the present invention takes into account the influence of the internal steel skeleton and the spiral stirrups outside the steel skeleton, and truly reflects the axial compression force mechanism of the new concrete column. Description of the Drawings

[0036] Figure 1 is a schematic diagram of the steel skeleton member provided in this embodiment;

[0037] Figure 2 is Figure 1 the sectional view taken along line 1-1 in

[0038] Figure 3 is Figure 1 the sectional view taken along line 2-2 in

[0039] Figure 4 is Figure 1 the sectional view taken along line 3-3 in Detailed Embodiments

[0040] The present invention will be further described below. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0041] Embodiment 1

[0042] This embodiment provides a new type of concrete-filled steel tube column, including a steel tube 1 and an internal steel skeleton member. Concrete is poured inside the steel tube and the steel skeleton member to form a composite section.

[0043] Referring to Figure 1 、 Figure 2 and Figure 3 , the steel skeleton member includes a circular steel sheet 2, a longitudinal stiffening plate 3 and a cross connecting plate 4.

[0044] Specifically, the circular steel sheet 2 and the longitudinal stiffening plate 3 are longitudinally arranged along the inner side of the steel tube 1 and are of the same length as the steel tube 1. The circular steel sheet 2 and the longitudinal stiffening plate 3 are welded into a whole.

[0045] Further, referring to Figure 2 and Figure 3 , there are 4 annular steel sheets, and correspondingly, there are also 4 longitudinal stiffening plates. The longitudinal stiffening plates are perpendicular to the annular steel sheets and are arranged along the inner side of the annular steel sheets throughout the length.

[0046] Further, referring to Figure 2 and Figure 4 , a cross connecting plate 4 is arranged at the center of the steel pipe. The cross connecting plate 4 is fixedly connected to each longitudinal stiffening plate through a first node plate 5 and a first bolt 6.

[0047] Further, the cross connecting plates 4 are longitudinally distributed inside the steel pipe, and the distance between adjacent cross connecting plates 4 is 1 m to 2 m.

[0048] Referring to Figure 2 , spiral stirrups 7 are arranged on the outer side of the steel skeleton member. The spiral stirrups 7 are arranged along the inner side of the steel pipe 1 and are of the same length as the steel pipe 1. The spiral stirrups 7 are welded to the outer surface of the annular steel sheet 2.

[0049] Referring to Figure 1 and Figure 2 , end plates 8 are arranged at the longitudinal head and tail ends of the steel skeleton member. The end plate 8 is a rectangular plate with 3 bolt holes on it and is welded to the outer side of the annular steel sheet 2.

[0050] Connecting plates 9 are arranged on the inner walls at the head and tail ends of the steel pipe. The connecting plates 9 are welded to the inner walls of the outer steel pipe.

[0051] The end plates 8 at both ends of the steel skeleton member are respectively connected to the connecting plates at both ends of the steel pipe through a second node plate 10 and a second bolt 11, so as to fix the whole steel skeleton member inside the steel pipe and prevent displacement during the process of pouring concrete.

[0052] Preferably, the steel materials of the steel pipe 1, the annular steel sheet 2, the longitudinal stiffening plate 3, the cross connecting plate 4, the first node plate 5, the end plate 8, the connecting plate 9 and the second node plate 10 can adopt any one of Q355, Q390, Q420 and Q460.

[0053] Preferably, the first bolt 6 and the second bolt 11 adopt 6.8 - grade or 8.8 - grade rough - made bolts.

[0054] Embodiment 2

[0055] This embodiment provides a new type of concrete - filled steel tube column, and its manufacturing steps are as follows:

[0056] Each part of the steel components of the new type of concrete - filled steel tube column, including the steel pipe 1, the annular steel sheet 2, the longitudinal stiffening plate 3, the cross connecting plate 4, the first node plate 5, the first bolt 6, the spiral stirrups 7, the end plate 8, the connecting plate 9, the second node plate 10 and the second bolt 11, are manufactured in the factory.

[0057] The factory completes the welding of the annular steel sheet 2 and the longitudinal stiffening plate 3.

[0058] The factory completes the assembly of the steel skeleton member. The annular steel sheets 2 are connected by the longitudinal stiffening plates 3, the cross connecting plates 4, the first gusset plates 5 and the first bolts 6 to form the steel skeleton member.

[0059] The factory completes the arrangement of the spiral stirrups on the outer side of the steel skeleton member and welds the spiral stirrups to the outer surface of the annular steel sheet.

[0060] The factory completes the welding of the end plates 8 at both ends of the steel skeleton member and the welding of the inner wall connecting plates 9 at both ends of the steel pipe.

[0061] The factory completes the trial assembly work of the steel pipe 1 and the steel skeleton member.

[0062] After transporting each part of the steel components of the new concrete-filled steel tube column to the construction site, sectional assembly is carried out.

[0063] At the site, the prepared concrete is poured into the inside of the steel pipe and the steel skeleton member, cured for 28 days as required, and then the construction quality acceptance of the concrete-filled steel tube column is carried out. After passing the acceptance, the new concrete-filled steel tube column is obtained.

[0064] Embodiment 3

[0065] This embodiment provides a calculation method for the compressive strength of a new concrete-filled steel tube column as follows:

[0066] Step 1: Calculate its equivalent reinforcement area A according to the arrangement of the spiral stirrups sso ;

[0067]

[0068] Among them, d s is the diameter of the annular steel skeleton, A ss is the cross-sectional area of the spiral stirrup, and s is the spacing between adjacent turns of the spiral stirrup.

[0069] Step 2: Calculate the sectional hoop coefficient θ according to the steel pipe cross-sectional area A s , the concrete area A c , and the equivalent area A of the spiral stirrup sso ; y ;

[0070]

[0071] Among them, f v is the tensile strength of the spiral stirrup, f c is the compressive strength of the internal concrete, and f is the design value of the compressive strength of the steel pipe.

[0072] Step 3: According to the hoop coefficient θy Calculate the design value of the compressive strength f of the concrete-filled steel tube section sc ;

[0073]

[0074] Among them, B is the influence coefficient of the steel grade on the confinement effect, and C is the influence coefficient of the concrete grade on the confinement effect.

[0075] Step 4. According to the steel tube area A s , the concrete area A c , the internal steel skeleton area A b and the design value of the compressive strength f of the concrete-filled steel tube section sc calculate the axial compressive strength bearing capacity N0 of the new concrete-filled steel tube column:

[0076] N0 = (A s + A c )f sc + A b f b ,

[0077] Among them, f b is the design value of the compressive strength of the circular steel tube.

[0078] The above is only the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A concrete-filled steel tube column, characterized in that, It includes a steel pipe and a steel skeleton member placed inside the steel pipe. Concrete is poured inside the steel pipe and the steel skeleton member to form a composite section; The steel skeleton member includes an annular steel sheet, longitudinal stiffening plates, and cross connecting plates; The annular steel sheet is longitudinally arranged along the inner side of the steel pipe and is of the same length as the steel pipe; The longitudinal stiffening plates are perpendicular to the annular steel sheet, and the longitudinal stiffening plates are arranged longitudinally along the inner side of the annular steel sheet and are welded to the annular steel sheet to form a whole; A cross connecting plate is arranged at the center of the steel pipe. The cross connecting plates are longitudinally distributed inside the steel pipe, and the longitudinal spacing between adjacent cross connecting plates is 1m - 2m; The cross connecting plates are fixedly connected to the longitudinal stiffening plates; Spiral stirrups are arranged on the outer side of the steel skeleton member. The spiral stirrups are arranged along the inner side of the steel pipe and are of the same length as the steel pipe. The spiral stirrups are welded to the outer surface of the annular steel sheet; The head and tail ends of the steel skeleton member are respectively fixedly connected to the head and tail ends of the steel pipe.

2. A concrete-filled steel tube column according to claim 1, characterized in that, There are 4 annular steel sheets and longitudinal stiffening plates each, and they are evenly distributed along the axial direction of the steel pipe.

3. A concrete-filled steel tubular column according to claim 2, wherein, The cross connecting plates and each longitudinal stiffening plate are fixedly connected through first gusset plates and first bolts; 4. A concrete-filled steel tubular column according to claim 1, characterized in that, End plates are arranged at the head and tail ends of the steel skeleton member; The end plates are welded to the outer side of the annular steel sheet; Connecting plates are provided at the head and tail ends of the steel pipe; The connecting plates are welded to the inner wall of the steel pipe; The end plates at both ends of the steel skeleton member are respectively connected to the connecting plates at both ends of the steel pipe through second gusset plates and second bolts to fix the steel skeleton member inside the steel pipe.

5. A concrete-filled steel tubular column according to claim 4, characterized in that, The steel materials of the steel pipe, annular steel sheet, longitudinal stiffening plates, cross connecting plates, end plates, connecting plates, and second gusset plates adopt any one of Q355, Q390, Q420, and Q460.

6. A concrete-filled steel tube column according to claim 4, characterized in that, The second bolts adopt 6.8 - grade or 8.8 - grade rough bolts.

7. A method for calculating the compressive strength of a concrete-filled steel tubular column according to any one of claims 1 to 6, characterized in that, It includes: Calculate the equivalent reinforcement area according to the arrangement of the spiral stirrups in the concrete-filled steel tubular column : ， Among them, is the diameter of the circular steel section, is the cross-sectional area of the spiral stirrup, is the spacing between adjacent turns of the spiral stirrup; According to the cross-sectional area of the steel pipe , the cross-sectional area of the concrete , and the equivalent cross-sectional area of the spiral stirrups , calculate the sectional confinement coefficient : ， Among them, is the tensile strength of the spiral stirrup, is the compressive strength of the internal concrete, is the design value of the compressive strength of the steel pipe; According to the confining coefficient calculate the design value of the compressive strength of the concrete-filled steel tube cross-section : ， Among them, is the influence coefficient of steel grade on the confinement effect, is the influence coefficient of concrete grade on the confinement effect; According to the area of the steel pipe , the area of the concrete , the area of the internal steel skeleton and the design value of the axial compressive strength of the concrete-filled steel tube section , calculate the axial compressive strength bearing capacity of the concrete-filled steel tube column : ， Among them, is the design value of the compressive strength of the circular steel pipe.

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