A method for calculating the bearing capacity of a spatial tube plate node

Abstract

The present application relates to a kind of bearing capacity calculation methods of space tube plate node, specifically includes the following steps: 1) selection section: selection section under the deformation of space tube plate node in different direction space load;2) assume stiffener rigidity: according to deformation, assume stiffener to be rigid plate;3) propose the calculation model of main pipe deformation resistance;4) hinge support equivalence: according to deformation, two hinge supports are equivalent to single hinge support;5) take half to get ring beam rigidity: obtain the calculation rigidity of circular ring beam;6) calculation, check and verify.The present application compared with prior art is in that: the failure mode of space tube plate node under the action of multi-plane different direction load is described, which fills the gap of bearing capacity calculation method of space tube plate node under the action of multi-plane different direction load.Perfects the design theory system of steel pipe joint, guarantees the reliability and safety of steel pipe structure under external load.

Description

Technical Field

[0001] This invention relates to the field of stress calculation technology for transmission towers, specifically to a method for calculating the bearing capacity of a spatial tube sheet node. Background Technology

[0002] The main types of joints in the structure of power transmission steel pipe towers are intersecting joints and tube sheet joints. Intersecting joints directly transmit the force of the spatial branch pipe to the main pipe, while tube sheet joints convert the force of the spatial branch pipe into planar force and then transmit it to the main pipe.

[0003] In power transmission line projects, the tower joints are complex and irregular, and most towers are located in remote areas with relatively harsh working conditions. If intersecting joints are used, not only will the construction progress be slow, but more importantly, the on-site welding quality cannot be guaranteed, which seriously affects the safety of the tower.

[0004] The node plates of the tube sheet joint are mechanically welded directly to the main pipe in the factory. On-site, only bolts are needed to connect the branch pipes to the main pipe, which is not only convenient for construction but also ensures quality. The forms and classifications of tube sheet joints are the same as those of the intersecting joints mentioned above. They can also be divided into planar joints and spatial joints. On transmission towers, almost all forms of spatial tube sheet joints are formed by coupling regular joint forms such as planar K-type joints, planar KT-type joints, spatial KK-type joints, and spatial KT-type joints in a certain spatial arrangement. Combined with appropriately distributed circumferential stiffening plates, they form spatial joints with high load-bearing capacity.

[0005] Spatial tube sheet nodes are the main node type in steel pipe structures such as transmission towers, and are also the most complex force convergence area in the structure. Currently, foreign standards such as Japanese specifications and CIDECT standards have specified calculation methods for simple planar tube sheet nodes. However, my country's current standards such as the "Steel Structure Design Standard", "Technical Regulations for the Design of Overhead Transmission Line Towers", and "Technical Regulations for the Design of Overhead Transmission Line Steel Pipe Towers" do not yet have provisions for the design of tube sheet nodes.

[0006] Due to the coupling effect of multi-plane loads, spatial tube sheet joints are more prone to deep yielding and local buckling. For example, when a load acting on one plane is of the same magnitude but opposite sign to a load acting on another plane, the coupling of loads exacerbates the local deformation of the tube and reduces the connection strength. On the other hand, for loads of the same sign, their coupling increases the axial pressure on the tube and intensifies the yielding at the bottom of the tube. Based on this, the bearing capacity of spatial tube sheet joints is usually significantly lower than that obtained using the single-plane connection method, posing a potential threat to the reliability of steel tube structures. Le et al. conducted experimental research and numerical analysis on DK joints under multi-plane loads of the same sign (loads acting on two planes are symmetrical along the bisector of the angle between the two planes), and proposed a method for calculating the ultimate bearing capacity of spatial tube sheet joints based on numerical fitting. However, research on the failure modes and bearing capacity calculation methods of spatial tube sheet joints under multi-plane loads of opposite signs is still lacking.

[0007] In summary, domestic standards lack regulations on the design methods for tube sheet joints in steel tube structures; regulations on the design methods for spatial tube sheet joints are currently absent in both domestic and international standards; and current research on spatial tube sheet joints only addresses loads acting in the same direction, failing to accurately reflect and predict the failure modes and load-bearing capacity of joints under loads acting in opposite directions. These shortcomings greatly increase the risk of failure of the designed steel tube tower structure joints under external loads, leading to the overall collapse of the structure.

[0008] Therefore, a method for calculating the bearing capacity of space tube sheet nodes urgently needs to be studied. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0010] A method for calculating the bearing capacity of a space tube sheet joint, specifically including the following steps:

[0011] 1) Section selection: Select the deformation section of the spatial tube sheet node under opposite spatial loads;

[0012] 2) Assume stiffness of the stiffening plate: Based on deformation, the stiffening plate is assumed to be a rigid plate;

[0013] 3) A calculation model for the deformation resistance of the main tube is proposed;

[0014] 4) Equivalent hinge support: Based on the deformation, the two hinge supports are equivalent to a single hinge support;

[0015] 5) Obtaining the stiffness of the ring beam by taking half: Taking half of the structure as the analysis system, the calculated stiffness of the circular ring beam is obtained according to the method in structural mechanics for calculating statically indeterminate problems;

[0016] 6) Calculate, verify and validate: Calculate the deformation resistance of the main tube and the ultimate bearing capacity of the tube sheet joints, etc., and use Matlab program to perform calculation and verification. Then compare and verify the calculation results with the finite element analysis results.

[0017] As a preferred embodiment, in step 2), it is assumed that the stiffening plate has a much greater stiffness than the main pipe, and that the stiffening plate rotates about the center point where it connects to the main pipe under the action of force.

[0018] As a preferred embodiment, in step 3), the stiffening plate acts like a lever around the center of rotation, and the applied force balances the deformation resistance of the main pipe. To obtain the value of the applied force, it is only necessary to calculate the deformation resistance of the main pipe. A calculation model for the deformation resistance of the main pipe is proposed, and the point of intersection before and after deformation is assumed to be a hinge support.

[0019] As a preferred embodiment, in step 4), the tube sheet node is defined as the limit state when the main tube deforms to 0.03 times its diameter. The majority of the main tube is in a linear elastic state, and the reaction force calculation model under the two forces is equivalent to the reaction force calculation model under a single force. Furthermore, the deformation within the range of the two lower support areas is small, so the two hinged supports can be equivalent to a single hinged support.

[0020] The advantages of this invention compared to existing technologies are as follows: it elucidates the failure modes of spatial tube sheet joints under multi-plane anisotropic loads, filling the gap in the calculation method for the bearing capacity of spatial tube sheet joints under multi-plane anisotropic loads. It also improves the design theory system of steel tube joints, ensuring the reliability and safety of steel tube structures under external loads. Attached Figure Description

[0021] Figure 1 This is a block diagram of the present invention.

[0022] Figures 2-5 This is a reference diagram used in the calculation process of this invention. Detailed Implementation

[0023] The present invention is illustrated below with specific embodiments, which are not intended to limit the scope of the invention.

[0024] A method for calculating the bearing capacity of a space tube sheet joint, specifically including the following steps:

[0025] 1. Cross-sectional deformation of the tube sheet joint under opposite spatial loads, such as Figure 2 ;

[0026] 2. Assume that the stiffener plate has a much greater stiffness than the chord, and that the stiffener plate rotates about the center point where it connects to the chord under the action of force, Δ = 2δ;

[0027] 3. The stiffening plate acts like a lever around the center of rotation, and the applied force P f With the deformation resistance P of the main body e They are mutually balanced. To obtain P... f The value only needs to be calculated for P e Therefore, a calculation model for the resistance to deformation of the main structural member is proposed, and the point of intersection before and after deformation is assumed to be a hinged support, such as... Figure 3 ;

[0028] 4. The tube sheet joint uses the deformation of the main pipe reaching 0.03 times its diameter as the limit state. Most areas of the main pipe are linearly elastic, and the reaction force calculation model under the two forces mentioned above is equivalent to the reaction force calculation model under a single force. Furthermore, the deformation within the two lower support areas is relatively small, so the two hinged supports can be considered equivalent to a single hinged support. Figure 4 .

[0029] 5. Taking half of the structure as the analysis system, the calculated stiffness of the circular ring beam is obtained according to the force method in structural mechanics for statically indeterminate problems, such as... Figure 5 .

[0030] Taking "semi-structure" as the research object, for hollow shell components, the ratio of their diameter to thickness is usually relatively large. Therefore, only the influence of bending moment on their deformation needs to be considered. The internal bending moment of the ring beam should include four parts represented by formulas (1)-(4): (1) the applied load (F / 2); (2) the angular constraint load (X1); (3) the horizontal constraint load (X2); and the support reaction load (X3).

[0031]

[0032]

[0033]

[0034]

[0035] in, R is the main pipe radius, T is the main pipe wall thickness, and θ is the angle between the calculated section and the axis of symmetry (see [reference needed]). Figure 5 .

[0036] The fundamental equations of the force method with three unknown parameters are:

[0037] δ 11 X1+δ 12 X2+δ 13 X3+Δ 1F =0 (5)

[0038] δ 21 X1+δ 22X2+δ 23 X3+Δ 2F =0 (6)

[0039] δ 31 X1+δ 32 X2+δ 33 X3+Δ 3F =0 (7)

[0040] The coefficients δ of the equation ij and free term Δ iF As given in formulas (8)-(16), the unknowns can be obtained from formulas (17)-(19).

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] Where E is the elastic modulus. b is the width of the ring beam, T is the thickness, and b = -16.315 + 0.125D - 0.880T 4.324 ×10 -3 .

[0055] The bending moment of the chord under load F / 2 can be obtained using formula (20):

[0056]

[0057] Similarly, the bending moment under unit load can be obtained using formula (21):

[0058]

[0059] The transformation of the supervisor can be obtained in the following ways.

[0060]

[0061]

[0062] According to formula (23), the deformation of the string is related to the position (parameter) of the hinge support, and the elastic stiffness of the constrained string can be obtained by formula (24).

[0063]

[0064] 6. The deformation resistance of the main tube and the ultimate bearing capacity of the tube sheet joint.

[0065] P′ e =K2Δ=2K2δ (25)

[0066] When failure is under the control of the competent authority, the ultimate bearing capacity is given by the following formula.

[0067]

[0068] This patent proposes a calculation method using Matlab program source code:

[0069]

[0070]

[0071] Comparison table of formula calculation results and finite element analysis results

[0072] To verify the accuracy of the proposed method, the finite element analysis results were compared with the model calculation results based on a finite element model of a space tube sheet node. The "Example" in the table below shows the calculated information for the space node: DKT represents a space KT-type node, 194x6 represents the outer diameter and wall thickness of the main pipe, and 120x10 represents the height and thickness of the stiffening plate. The average ratio of the theoretical model calculation results to the finite element analysis results is 1.04, and the standard deviation is 0.09, demonstrating the accuracy of the calculation method.

[0073]

[0074]

[0075] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for calculating the bearing capacity of a spatial tube sheet joint, characterized in that, Specifically, the following steps are included: 1) Section selection: Select the deformation section of the spatial tube sheet node under opposite spatial loads; 2) Assume stiffness of the stiffening plate: Based on deformation, the stiffening plate is assumed to be a rigid plate; 3) Propose a calculation model for the deformation resistance of the main tube; 4) Equivalent hinge support: Based on the deformation, the two hinge supports are equivalent to a single hinge support; 5) Obtain the ring beam stiffness by taking half: Take half of the structure with hinged support as the analysis system, calculate the internal bending moment of the ring beam, and obtain the calculated stiffness of the ring beam. 6) Calculate, verify and validate: Calculate the deformation resistance of the main tube and the ultimate bearing capacity of the tube sheet joint, obtain the calculation results of the formula, and perform calculation verification in conjunction with the Matlab program. Based on the finite element model of the spatial tube sheet joint, the calculation results of the formula are then compared and verified with the finite element analysis results.

2. The method for calculating the bearing capacity of a space tube sheet node according to claim 1, characterized in that: In step 2), it is assumed that the stiffening plate has a much greater stiffness than the main pipe, and that the stiffening plate rotates around the center point where it connects to the main pipe under the action of force.

3. The method for calculating the bearing capacity of a space tube sheet node according to claim 1, characterized in that: In step 3), the stiffening plate acts like a lever around the center of rotation. The applied force is balanced with the deformation resistance of the main pipe. To obtain the value of the applied force, it is only necessary to calculate the deformation resistance of the main pipe. A calculation model for the deformation resistance of the main pipe is proposed, and the point of intersection before and after deformation is assumed to be a hinge support.

4. The method for calculating the bearing capacity of a space tube sheet node according to claim 3, characterized in that: In step 4), the tube sheet node is defined as the limit state when the main tube deforms to 0.03 times the diameter. Most areas of the main tube are in linear elasticity. The reaction force calculation model under the two forces is equivalent to the reaction force calculation model under a single force. Furthermore, the deformation within the area of ​​the two lower supports is small, so the two hinged supports are equivalent to a single hinged support.

Images