Method for calculating bending bearing capacity of cable bent tower with steel box and concrete filled steel tube combined structure

Abstract

The invention discloses a bending bearing capacity calculation method for a cable bent tower of a steel box and concrete filled steel tube composite structure. The method comprises the following steps that a tower column is divided into a cross beam area and a non-cross beam area; when the bending bearing capacity of the non-cross-beam area is calculated, the bending bearing capacity of the non-cross-beam area is calculated on the basis of plane section assumption; when the bending bearing capacity of the cross beam area is calculated, the tower column is divided into an external steel structure and an internal steel pipe concrete latticed column structure to be calculated respectively; when the bending bearing capacity of the external steel structure is calculated, the bending bearing capacity of the external steel structure is calculated based on total cross-section plasticity; and when the bending bearing capacity of the internal concrete-filled steel tube latticed column structure is calculated, the bending bearing capacity of the internal concrete-filled steel tube latticed column structure is calculated by adopting plane section assumption. According to the method for calculating the bending bearing capacity of the cable bent tower of the steel box and concrete filled steel tube composite structure, the cross beam area and the non-cross beam area can be calculated in a targeted mode, and the method has the advantages of being accurate and reliable in calculation result and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and in particular, to a calculation method for the flexural-compressive bearing capacity of a cable tower with a steel box and concrete-filled steel tube composite structure. Background Art

[0002] With the increasing demand for the construction of long-span bridges in bridge engineering, the structural form of bridge cable towers has gradually evolved from reinforced concrete structures, concrete-filled steel tube structures to steel box and concrete-filled steel tube composite structures. Due to its ability to simultaneously exert the collaborative stress advantages of steel structures and concrete structures, the steel box and concrete-filled steel tube composite structure exhibits excellent mechanical properties in long-span bridge engineering and has become a cable tower structural form with good application prospects.

[0003] In the calculation method for the flexural-compressive bearing capacity of a steel box and concrete-filled steel tube composite structure cable tower in the related art, the plane section assumption is adopted, that is, it is assumed that the cross-section of the composite cable tower always maintains a planar shape during the stress process. However, the plane section assumption is not applicable to all positions of the composite structure cable tower, and some areas with complex stress cannot maintain the plane section assumption under the ultimate bearing capacity state. This results in insufficient calculation accuracy in these areas and the failure to correctly reflect the flexural-compressive bearing capacity during the design calculation stage. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a calculation method for the flexural-compressive bearing capacity of a steel box and concrete-filled steel tube composite structure cable tower, which can calculate the crossbeam area and the non-crossbeam area separately in a targeted manner and has the advantages of accurate and reliable calculation results.

[0005] To achieve the above object, according to an embodiment of the first aspect of the present invention, a calculation method for the flexural-compressive bearing capacity of a steel box and concrete-filled steel tube composite structure cable tower is provided. The steel box and concrete-filled steel tube composite structure cable tower includes two tower columns and a plurality of crossbeams. Each crossbeam is respectively connected to the two tower columns. Each tower column includes a steel box, four concrete-filled steel tube lattice columns, and a plurality of longitudinal diaphragms. The concrete-filled steel tube lattice columns are arranged in the steel box, and the longitudinal diaphragms are respectively connected to the steel box and the concrete-filled steel tube lattice columns. The calculation method for the flexural-compressive bearing capacity includes the following steps:

[0006] Divide the tower column into a crossbeam area connected to the crossbeam and a non-crossbeam area not connected to the crossbeam;

[0007] When calculating the flexural-compressive bearing capacity of the non-crossbeam area, calculate the flexural-compressive bearing capacity of the non-crossbeam area based on the plane section assumption;

[0008] When calculating the flexural-compressive bearing capacity of the crossbeam area, the tower column is divided into two parts, namely the external steel structure and the internal concrete-filled steel tubular lattice column structure, for separate calculations. The external steel structure includes the steel box and a plurality of the longitudinal diaphragms. The internal concrete-filled steel tubular lattice column structure includes four concrete-filled steel tubular lattice columns. The flexural-compressive bearing capacity of the crossbeam area is equal to the sum of the flexural-compressive bearing capacities of the external steel structure and the internal concrete-filled steel tubular lattice column structure;

[0009] When calculating the flexural-compressive bearing capacity of the external steel structure, the flexural-compressive bearing capacity of the external steel structure is calculated based on the full-section plasticity;

[0010] When calculating the flexural-compressive bearing capacity of the internal concrete-filled steel tubular lattice column structure, the flexural-compressive bearing capacity of the internal concrete-filled steel tubular lattice column structure is calculated by adopting the plane-section assumption.

[0011] According to the method for calculating the flexural-compressive bearing capacity of the steel box and concrete-filled steel tubular composite structure cable tower according to the embodiment of the present invention, it is possible to calculate the crossbeam area and the non-crossbeam area separately in a targeted manner, and has the advantages of accurate and reliable calculation results.

[0012] In addition, the method for calculating the flexural-compressive bearing capacity of the steel box and concrete-filled steel tubular composite structure cable tower according to the above embodiment of the present invention may further have the following additional technical features:

[0013] According to an embodiment of the present invention, when calculating the flexural-compressive bearing capacity of the internal concrete-filled steel tubular lattice column structure, the four concrete-filled steel tubular lattice columns are divided into two axially symmetric groups for separate calculations, and each group includes two concrete-filled steel tubular lattice columns.

[0014] According to an embodiment of the present invention, let N1 and N2 be the axial forces of the two concrete-filled steel tubular lattice columns in each group, M1 and M2 be the bending moments of the two concrete-filled steel tubular lattice columns in each group, b1 and b2 be the distances from the axes of the two concrete-filled steel tubular lattice columns in each group to the center of the entire internal concrete-filled steel tubular lattice column structure, the axial force of the internal concrete-filled steel tubular lattice column structure is N and the bending moment is M, then:

[0015]

[0016] According to an embodiment of the present invention, the concrete-filled steel tubular lattice column includes an external steel pipe and internal concrete. Let E s and E c be the elastic moduli of the steel pipe and the concrete respectively, A s1 and A s2 be the cross-sectional areas of the two steel pipes respectively, A c1 and A c2 be the cross-sectional areas of the concrete in the two steel pipes respectively, Is1 and I s2 are the sectional moment of inertia of the two steel pipes respectively, and I c1 and I c2 are the sectional moment of inertia of the concrete in the two steel pipes respectively, then:

[0017]

[0018] where α1 = (EI)1 / (EI), α2 = (EI)2 / (EI), (EA)1 = E s A s1 + E c A c1 , (EA)2 = E s A s2 + E c A c2 , (EI)1 = E s I s1 + E c I c1 , (EI)2 = E s I s2 + E c I c2 ; (EA)1 = (EA)2, (EI)1 = (EI)2.

[0019] According to an embodiment of the present invention, when calculating the flexural compressive bearing capacity of each group of the concrete-filled steel tubular lattice columns, each group of the concrete-filled steel tubular lattice columns is divided into a uniform compression state and a single compression state for separate calculations. In the uniform compression state, the two concrete-filled steel tubular lattice columns in each group bear pressure. In the single compression state, one of the two concrete-filled steel tubular lattice columns in each group bears pressure and the other bears tension.

[0020] According to an embodiment of the present invention, when calculating the concrete-filled steel tubular lattice columns in the uniform compression state, both N1 and N2 are greater than 0. Let N1 > N2, and the following steps are included:

[0021] Calculate N1 and M1 according to the pressure-moment correlation relationship of the compressed concrete-filled steel tubular lattice column;

[0022] Obtain N2, M2, N, and M;

[0023] Check the other concrete-filled steel tubular lattice column to verify that it has not reached the flexural compressive limit state.

[0024] According to an embodiment of the present invention, when calculating the concrete-filled steel tubular lattice columns in the single compression state, let N1 > 0 while N2 < 0, and the following steps are included:

[0025] Calculate the ultimate loads of the two concrete-filled steel tubular lattice columns respectively for the flexural-compression member and the flexural-tension member, and the ultimate load of the corresponding internal concrete-filled steel tubular lattice column structure. Take the calculation result with the smaller ultimate load of the internal concrete-filled steel tubular lattice column structure as the final calculation result.

[0026] According to an embodiment of the present invention, when calculating the flexural-compression bearing capacity of each group of the concrete-filled steel tubular lattice columns, the following steps are included:

[0027] Calculate one of the concrete-filled steel tubular lattice columns according to the flexural-compression ultimate state, and calculate N2 of the other concrete-filled steel tubular lattice column;

[0028] If N2 > 0, check the other concrete-filled steel tubular lattice column according to the flexural-compression ultimate state to ensure that it does not reach the flexural-compression ultimate state. If N2 < 0, check the other concrete-filled steel tubular lattice column according to the flexural-tension ultimate state to ensure that it does not reach the flexural-tension ultimate state. If it reaches the flexural-tension ultimate state, recalculate with the flexural-tension ultimate state of the other concrete-filled steel tubular lattice column as the ultimate state of the overall member.

[0029] According to an embodiment of the present invention, the calculation of the flexural-compression and flexural-tension ultimate states of the concrete-filled steel tubular lattice columns is carried out by theoretical calculation in accordance with the Technical Specification for Concrete-Filled Steel Tubular Structures DBJ-T13-51-2010.

[0030] According to an embodiment of the present invention, let M i be the flexural-compression bearing capacity of the internal concrete-filled steel tubular lattice column structure, M o be the flexural-compression bearing capacity of the external steel structure, M t be the total flexural-compression bearing capacity of the combined structure cable tower section, then:

[0031] M t = M i + M o .

[0032] The additional aspects and advantages of the present invention will be partly given in the following description, partly will become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, in which:

[0034] Figure 1 is a schematic structural diagram of a steel box concrete-filled steel tubular combined structure cable tower according to an embodiment of the present invention.

[0035] Figure 2It is a schematic cross-sectional structure diagram of a tower column of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0036] Figure 3 It is a schematic longitudinal-sectional structure diagram of a tower column of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0037] Figure 4 It is a schematic diagram of a force calculation method for the non-crossbeam area of a tower column of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0038] Figure 5 It is a schematic structure diagram of the external steel structure of a tower column of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0039] Figure 6 It is a schematic structure diagram of the internal concrete-filled steel tube lattice column structure of a tower column of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0040] Figure 7 It is a schematic diagram of a force calculation method for the crossbeam area of a tower column of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0041] Figure 8 It is a flowchart of a calculation method for the flexural-compressive bearing capacity of a steel box and concrete-filled steel tube composite structure cable tower according to an embodiment of the present invention.

[0042] Reference numerals: Steel box and concrete-filled steel tube composite structure cable tower 1, tower column 10, steel box 11, concrete-filled steel tube lattice column 12, longitudinal partition 13, external steel structure 100, internal concrete-filled steel tube lattice column structure 200, crossbeam 20. Detailed implementation manners

[0043] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0044] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the features defined with "first", "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0045] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] The following describes a method for calculating the flexural and compressive bearing capacity of a cable-stayed tower of a steel box and concrete-filled steel tube composite structure according to an embodiment of the present invention with reference to the drawings.

[0047] As Figures 1-8 shown, the cable-stayed tower 1 of the steel box and concrete-filled steel tube composite structure according to an embodiment of the present invention includes two tower columns 10 and a plurality of cross beams 20. Each cross beam 20 is respectively connected to the two tower columns 10. Each tower column 10 includes a steel box 11, four concrete-filled steel tube lattice columns 12, and a plurality of longitudinal partition plates 13. The concrete-filled steel tube lattice columns 12 are arranged inside the steel box 11, and the longitudinal partition plates 13 are respectively connected to the steel box 11 and the concrete-filled steel tube lattice columns 12.

[0048] Specifically, there may be three cross beams 20, including an upper cross beam, a middle cross beam, and a lower cross beam.

[0049] The method for calculating the flexural and compressive bearing capacity includes the following steps:

[0050] The tower column 10 is divided into a cross beam area connected to the cross beam 20 and a non-cross beam area not connected to the cross beam 20; here it should be understood that the "connection" here means direct connection and does not include indirect connection. In other words, the area on the tower column 10 directly connected to the cross beam 20 is divided into the cross beam area, and the area not directly connected to the cross beam 20 is divided into the non-cross beam area.

[0051] When calculating the flexural-compressive bearing capacity of the non-crossbeam area, the flexural-compressive bearing capacity of the non-crossbeam area is calculated based on the plane section assumption.

[0052] When calculating the flexural-compressive bearing capacity of the crossbeam area, the tower column 10 is divided into two parts, namely the external steel structure 100 and the internal concrete-filled steel tube lattice column structure 200, for separate calculations. The external steel structure 100 includes a steel box 11 and a plurality of longitudinal diaphragms 13, and the internal concrete-filled steel tube lattice column structure 200 includes four concrete-filled steel tube lattice columns 12. The flexural-compressive bearing capacity of the crossbeam area is equal to the sum of the flexural-compressive bearing capacity of the external steel structure 100 and the flexural-compressive bearing capacity of the internal concrete-filled steel tube lattice column structure 200.

[0053] When calculating the flexural-compressive bearing capacity of the external steel structure 100, the flexural-compressive bearing capacity of the external steel structure 100 is calculated based on the full-section plasticity.

[0054] When calculating the flexural-compressive bearing capacity of the internal concrete-filled steel tube lattice column structure 200, the plane section assumption is adopted to calculate the flexural-compressive bearing capacity of the internal concrete-filled steel tube lattice column structure.

[0055] This application is made based on the inventor's discovery and recognition of the following facts and problems:

[0056] In the calculation method of the flexural-compressive bearing capacity of the steel box concrete-filled steel tube composite structure cable tower in the related art, the plane section assumption is adopted, that is, it is assumed that the cross-section of the composite cable tower always maintains a plane shape during the stress process. However, the plane section assumption is not applicable to all positions of the composite structure cable tower, and some areas with complex stress cannot maintain the plane section assumption under the ultimate bearing capacity state. This results in insufficient calculation accuracy in these areas and the failure to correctly reflect the flexural-compressive bearing capacity in the design calculation stage.

[0057] Specifically, the cable tower of a long-span bridge mainly includes a tower column and a crossbeam, and has the stress characteristics of a transverse frame system. The tower column is mainly composed of an external steel box and an internal concrete-filled steel tube lattice column, and longitudinal diaphragms are connected between the steel box and the concrete-filled steel tube lattice column. The combination of the steel box and the concrete-filled steel tube column can make full use of the advantages of both in compression and bending resistance. The steel box structure has good tensile and bending resistance, while the concrete-filled steel tube lattice column has a high bearing capacity under flexural-compressive action, which can effectively disperse and transfer external forces and ensure the overall mechanical properties and stability of the cable tower. In addition, the cross-sectional form and structure of the composite cable tower can effectively reduce the material consumption and the self-weight of the structure, thereby improving the economic benefits.

[0058] Through a large amount of research, the inventors of the present application have found that near the cross beam of the combined structure cable tower, since the shear force transmitted by the connecting beam is first transmitted to the steel box and then distributed to the concrete-filled steel tube through the longitudinal partition, the shear stress of the steel box and the longitudinal partition in the area near the connecting beam increases, and the increase of the middle longitudinal partition is particularly obvious, and the plane section assumption no longer holds here. This local effect has not been fully considered in the existing design methods, resulting in insufficient calculation accuracy in these areas and the failure to correctly reflect the flexural-compressive bearing capacity in the design section. This is determined by the mechanical characteristics of the transverse frame system and has nothing to do with the section characteristics of the concrete-filled steel tube in the steel box. Therefore, away from the cross beam, the internal forces of the combined cable tower can be calculated according to the plane section assumption, and the plane section assumption should not be used for calculation near the cross beam.

[0059] According to the mechanical characteristics of the concrete-filled steel tube in the steel box combined structure cable tower 1, the calculation of the flexural-compressive bearing capacity is divided into separate calculations for the non-cross beam area and the cross beam area. Among them, since the non-cross beam area is not affected by the force of the cross beam 20, the overall section satisfies the stress state under the plane section assumption; while the cross beam area is affected by the force of the cross beam 20, and the outer steel box will yield under the ultimate stress state, and the section deformation no longer maintains the stress state of the plane section.

[0060] For the non-cross beam area, the section of the combined structure cable tower 1 can maintain the plane section assumption and can be calculated according to the Figure 4 shown stress model.

[0061] For the cross beam area, at the ultimate bearing capacity state, the flange of the outer steel box 11 and the longitudinal partition 13 have basically yielded, and although the section deformation of the four internal concrete-filled steel tube lattice columns 12 is no longer a plane section after deformation, the deviation is negligible. To simplify the calculation of the flexural-compressive bearing capacity of the combined structure cable tower 1, the section of the combined structure cable tower 1 is divided into two parts, the external steel structure 100 and the internal concrete-filled steel tube lattice column structure 200, for separate calculations, as shown in Figure 5 and Figure 6 shown. The external steel structure 100 calculates the flexural bearing capacity according to the full-section plasticity. Since the deviation of the plane section of the internal concrete-filled steel tube lattice column structure 200 can be ignored, the plane section assumption can still be used to calculate the flexural-compressive bearing capacity, and the sum of the two is the total flexural-compressive bearing capacity of the section. It is assumed that the external steel structure 100 does not bear axial force after reaching full-section yield during calculation. As shown in Figure 7 shown, the cross beam area can be calculated according to the Figure 7 shown stress model.

[0062] According to the cable tower 1 of the steel box and concrete-filled steel tube composite structure according to the embodiment of the present invention, by separately calculating the tower column 10 of the cable tower 1 of the steel box and concrete-filled steel tube composite structure into the crossbeam area and the non-crossbeam area, the cooperative work of the steel box 11 and the concrete-filled steel tube lattice column 12 under different stress states can be more accurately reflected. Especially in the ultimate bearing capacity state, the sectional calculation method enables the mechanical properties of the external steel structure 100 and the internal concrete-filled steel tube lattice column structure 200 to be effectively integrated, improving the accuracy and reliability of the overall calculation.

[0063] Moreover, aiming at the complex stress condition in the crossbeam area, the traditional plane section assumption calculation method is corrected, making the calculation in the local complex stress area more reasonable, avoiding the risks of stress concentration and local failure, and thus greatly improving the safety and durability of the structure.

[0064] In addition, by separately calculating and superimposing the flexural-compressive bearing capacities of the external steel structure 100 and the internal concrete-filled steel tube lattice column structure 200, it can be ensured that the forces of the two are reasonably distributed under the ultimate state during the bridge design process, thus facilitating the improvement of the overall bearing capacity of the composite structure cable tower 1.

[0065] Therefore, the cable tower 1 of the steel box and concrete-filled steel tube composite structure according to the embodiment of the present invention can specifically calculate the crossbeam area and the non-crossbeam area separately, and has the advantages of accurate and reliable calculation results.

[0066] Next, the cable tower 1 of the steel box and concrete-filled steel tube composite structure according to the specific embodiment of the present invention will be described with reference to the drawings.

[0067] Specifically, when calculating the flexural-compressive bearing capacity of the internal concrete-filled steel tube lattice column structure 200, the four concrete-filled steel tube lattice columns 12 are divided into two axially symmetric groups for separate calculation, and each group includes two concrete-filled steel tube lattice columns 12. This can facilitate the simplification of the calculation process and improve the calculation efficiency.

[0068] More specifically, let N1 and N2 be the axial forces of the two concrete-filled steel tube lattice columns 12 in each group, M1 and M2 be the bending moments of the two concrete-filled steel tube lattice columns 12 in each group, b1 and b2 be the distances from the axes of the two concrete-filled steel tube lattice columns 12 in each group to the center of the entire internal concrete-filled steel tube lattice column structure 200, the axial force of the internal concrete-filled steel tube lattice column structure 200 be N and the bending moment be M, then:

[0069]

[0070] This can facilitate the calculation of the axial force and bending moment of the internal concrete-filled steel tube lattice column structure 200.

[0071] Furthermore, the concrete-filled steel tubular lattice column 12 includes an outer steel pipe and inner concrete. Let E s and E c be the elastic moduli of the steel pipe and the concrete respectively, A s1 and A s2 be the cross-sectional areas of the two said steel pipes respectively, A c1 and A c2 be the cross-sectional areas of the concrete in the two said steel pipes respectively, I s1 and I s2 be the moment of inertia of the cross-section of the two said steel pipes respectively, I c1 and I c2 be the moment of inertia of the cross-section of the concrete in the two said steel pipes respectively. Then:

[0072]

[0073] where α1 = (EI)1 / (EI), α2 = (EI)2 / (EI), (EA)1 = E s A s1 + E c A c1 , (EA)2 = E s A s2 + E c A c2 , (EI)1 = E s I s1 + E c I c1 , (EI)2 = E s I s2 + E c I c2 ; (EA)1 = (EA)2, (EI)1 = (EI)2.

[0074] Since the cross-section of the concrete-filled steel tubular lattice column 12 can basically maintain a plane section at each loading stage, its deflection can be ignored and it can be applied to the plane section assumption, which further facilitates the calculation of the bearing capacity of the internal concrete-filled steel tubular lattice column structure 200.

[0075] Specifically, by combining the above four equations, the current unknowns are N1, N2, M1, M2, M, N. The relationship between the axial force and moment of the concrete-filled steel tubular lattice column 12 under the ultimate bearing capacity state is also required as a supplementary equation. In the concrete-filled steel tubular lattice column 12, both of the two-limb concrete-filled steel tubular lattice columns 12 may bear compression or one limb bears compression and the other limb bears tension. Therefore, two cases need to be considered in the calculation:

[0076] In some embodiments, when calculating the flexural-compressive bearing capacity of each group of concrete-filled steel tubular lattice columns 12, each group of concrete-filled steel tubular lattice columns 12 is divided into a uniform compression state and a single compression state for separate calculations. In the uniform compression state, both of the two concrete-filled steel tubular lattice columns 12 in each group bear pressure. In the single compression state, one of the two concrete-filled steel tubular lattice columns 12 in each group bears pressure and the other bears tension. In this way, the stress conditions of the concrete-filled steel tubular lattice columns 12 in the two states can be calculated separately.

[0077] Specifically, when calculating the concrete-filled steel tubular lattice column 12 in the uniform compression state, both N1 and N2 are greater than 0. Assuming N1 > N2, the following steps are included:

[0078] Calculate N1 and M1 according to the pressure-moment correlation relationship of the compressed concrete-filled steel tubular lattice column 12;

[0079] Obtain N2, M2, N, and M;

[0080] Check the other concrete-filled steel tubular lattice column 12 to verify that it has not reached the flexural-compressive ultimate state.

[0081] In this way, it is convenient to calculate the stress condition of the concrete-filled steel tubular lattice column 12 in the uniform compression state.

[0082] When calculating the concrete-filled steel tubular lattice column 12 in the single compression state, assuming N1 > 0 and N2 < 0, the following steps are included:

[0083] Calculate the ultimate loads of the two concrete-filled steel tubular lattice columns 12 and the corresponding ultimate loads of the internal concrete-filled steel tubular lattice column structures 200 respectively as flexural-compressive members and tension-compressive members, and take the calculation result with the smaller ultimate load of the internal concrete-filled steel tubular lattice column structure 200 as the final calculation result.

[0084] In this way, it is convenient to calculate the stress condition of the concrete-filled steel tubular lattice column 12 in the single compression state.

[0085] In some other embodiments, when calculating the flexural-compressive bearing capacity of each group of the concrete-filled steel tubular lattice columns, the following steps are included:

[0086] Calculate one of the concrete-filled steel tubular lattice columns 12 according to the flexural-compressive ultimate state and calculate N2 of the other concrete-filled steel tubular lattice column 12;

[0087] If N2 > 0, then check the other concrete-filled steel tubular lattice column 12 according to the flexural-compression ultimate state to ensure that it has not reached the flexural-compression ultimate state. If N2 < 0, then check the other concrete-filled steel tubular lattice column 12 according to the tension-bending ultimate state to ensure that it has not reached the tension-bending ultimate state. If it has reached the tension-bending ultimate state, then recalculate with the tension-bending ultimate state of the other concrete-filled steel tubular lattice column 12 as the ultimate state of the overall component. This can comprehensively calculate the uniform compression state and the single compression state, simplify the calculation process, and improve the calculation efficiency.

[0088] Optionally, the calculation of the flexural-compression and tension-bending ultimate states of the concrete-filled steel tubular lattice column 12 is carried out according to the theoretical calculation in the Technical Specification for Concrete-Filled Steel Tubular Structures DBJ-T13-51-2010. This can facilitate the calculation of the flexural-compression and tension-bending ultimate states of the concrete-filled steel tubular lattice column 12.

[0089] Specifically, the cross-sectional set information and material properties of the specimen are both taken as the measured values. The flow of calculating the flexural-compression and bearing capacity of circular concrete-filled steel tubes in this specification is as follows:

[0090] a) First, calculate the confinement effect coefficient, axial compressive strength, and flexural bearing capacity calculation coefficient of the circular concrete-filled steel tube as the basic parameters for subsequent calculations:

[0091] ξ0 = (A s f y ) / (A c f c )

[0092] f sc = (1.14 + 1.02ξ0)f c

[0093] γ m = 1.1 + 0.48ln(ξ0 + 0.1)

[0094] b) Then, calculate the axial compressive bearing capacity and pure flexural bearing capacity of the circular concrete-filled steel tube as the basic parameters for the flexural-compression and tension-bending bearing capacities:

[0095] N u = f sc A sc = f sc (A s + A c )

[0096] M u = γ m f sc W scm = γ m f sc πD 3 / 32

[0097] c) Bending-related curves:

[0098]

[0099] In the formula, a, b, and c are parameters, which are calculated according to the following formula:

[0100]

[0101] d) Stretch-bending related curves

[0102]

[0103] In the formula, N is the absolute value of the tensile force.

[0104] Specifically, let M i be the flexural-compressive bearing capacity of the internal concrete-filled steel tube lattice column structure, M o be the flexural-compressive bearing capacity of the external steel structure, and M t be the total flexural-compressive bearing capacity of the combined structure cable tower section. Then:

[0105] M t = M i + M o .

[0106] Specifically, it is assumed that the external steel structure 100 does not bear axial force after reaching full cross-section yield during calculation. This can facilitate the calculation of the bearing capacity of the external steel structure 100.

[0107] Other components and operations of the flexural-compressive bearing capacity calculation method for the steel box concrete-filled steel tube combined structure cable tower according to the embodiments of the present invention are known to those of ordinary skill in the art and will not be described in detail here.

[0108] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0109] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower, characterized in that: The steel box steel tube concrete composite structure cable tower comprises two tower columns and a plurality of cross beams, each of the cross beams is respectively connected to the two tower columns, each of the tower columns comprises a steel box, four steel tube concrete lattice columns and a plurality of longitudinal diaphragms, the steel tube concrete lattice columns are arranged in the steel box, the longitudinal diaphragms are respectively connected to the steel box and the steel tube concrete lattice columns, and the compression and bending bearing capacity calculation method comprises the following steps: Dividing the tower column into a crossbeam area connected to the crossbeam and a non-crossbeam area not connected to the crossbeam; When calculating the compression-bending bearing capacity of the non-beam area, the compression-bending bearing capacity of the non-beam area is calculated based on the plane section assumption; When calculating the compression-bending bearing capacity of the cross beam area, the tower column is divided into two parts: an external steel structure and an internal steel tube concrete lattice column structure, and the calculations are performed separately. The external steel structure includes the steel box and a plurality of longitudinal partitions, and the internal steel tube concrete lattice column structure includes four steel tube concrete lattice columns. The compression-bending bearing capacity of the cross beam area is equal to the sum of the compression-bending bearing capacity of the external steel structure and the compression-bending bearing capacity of the internal steel tube concrete lattice column structure. When calculating the compression and bending bearing capacity of the external steel structure, the compression and bending bearing capacity of the external steel structure is calculated based on the full-section plasticity; When calculating the compression-bending bearing capacity of the internal steel tube concrete lattice column structure, a plane section assumption is adopted to calculate the compression-bending bearing capacity of the internal steel tube concrete lattice column structure.

2. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 1 is characterized in that: When calculating the compression and bending bearing capacity of the internal steel tube concrete lattice column structure, the four steel tube concrete lattice columns are divided into two axisymmetric groups for separate calculations, each group including two steel tube concrete lattice columns.

3. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 2 is characterized in that: Assume that N1 and N2 are the axial forces of the two steel tube concrete lattice columns in each group, M1 and M2 are the bending moments of the two steel tube concrete lattice columns in each group, b1 and b2 are the distances from the axis of the two steel tube concrete lattice columns in each group to the center of the entire internal steel tube concrete lattice column structure, and the axial force of the internal steel tube concrete lattice column structure is N and the bending moment is M, then:

4. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 3 is characterized in that: The steel tube concrete lattice column includes an external steel tube and an internal concrete. s and E c are the elastic moduli of the steel pipe and concrete, A s1 and A s2 are the cross-sectional areas of the two steel pipes, A c1 and A c2 are the cross-sectional areas of the concrete in the two steel pipes, I s1 and I s2 are the section inertia moments of the two steel pipes, I c1 and I c2 are the section inertia moments of the concrete in the two steel pipes respectively, then: where α1 = (EI)1 / (EI), α2 = (EI)2 / (EI), (EA)1 = E s A s1 + E c A c1 , (EA)2 = E s A s2 + E c A c2 , (EI)1 = E s I s1 + E c i c1 , (EI)2 = E s I s2 + E c I c2 ; (EA)1 = (EA)2, (EI)1 = (EI)2.

5. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 4 is characterized in that: When calculating the compression-bending bearing capacity of each group of the steel tube concrete lattice columns, each group of the steel tube concrete lattice columns is divided into a uniform compression state and a single compression state for separate calculations. In the uniform compression state, the two steel tube concrete lattice columns in each group are both subjected to compression. In the single compression state, one of the two steel tube concrete lattice columns in each group is subjected to compression and the other is subjected to tension.

6. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 5 is characterized in that: When calculating the steel tube concrete lattice column in the uniformly compressed state, N1 and N2 are both greater than 0, and N1>N2 is assumed, and the following steps are included: Calculate N1 and M1 based on the pressure-bending moment correlation of the compressed concrete-filled steel tube lattice column; Obtain N2, M2, N and M; The other steel tube concrete lattice column is verified to have not reached the compression-bending limit state.

7. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 5 is characterized in that: When calculating the steel tube concrete lattice column in the single compression state, assuming N1>0 and N2<0, the following steps are included: The ultimate loads of the two steel tube concrete lattice columns and their corresponding ultimate loads of the internal steel tube concrete lattice column structure are calculated according to the compression bending members and the tension bending members, and the calculation result with the smaller ultimate load of the internal steel tube concrete lattice column structure is taken as the final calculation result.

8. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 4 is characterized in that: When calculating the compression-bending bearing capacity of each group of the steel tube concrete lattice columns, the following steps are included: Calculate one of the steel tube concrete lattice columns according to the compression-bending limit state, and calculate N2 of the other steel tube concrete lattice column; If N2>0, the other steel tube concrete lattice column is checked according to the compression and bending limit state to ensure that it has not reached the compression and bending limit state. If N2<0, the other steel tube concrete lattice column is checked according to the tension and bending limit state to ensure that it has not reached the tension and bending limit state. If it has reached the tension and bending limit state, the limit state of the entire component is recalculated based on the tension and bending limit state reached by the other steel tube concrete lattice column.

9. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to any one of claims 1 to 8, characterized in that: The calculation of the compression-bending and tension-bending limit states of the steel tube concrete lattice column is carried out theoretically in accordance with the DBJ-T13-51-2010 Technical Code for Steel Tube Concrete Structures.

10. The method for calculating the compression and bending bearing capacity of a steel box steel tube concrete composite structure cable tower according to claim 1, characterized in that: Assume M i is the compression and bending bearing capacity of the internal steel tube concrete lattice column structure, M o is the bending capacity of the external steel structure, M t is the total compression and bending bearing capacity of the composite structure tower section, then: M t =M i +M o 。

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