Bearing capacity calculation method and system for circular steel tube thin-wall hollow concrete T-shaped joint

Abstract

The invention relates to the technical field of concrete filled steel tube bearing capacity, in particular to a bearing capacity calculation method and system for a circular steel tube thin-wall hollow concrete T-shaped joint. A corresponding punching model meets the following basic conditions that it is assumed that a main pipe of the circular steel pipe thin-wall hollow concrete member is a structural system composed of a steel pipe and concrete, and when the main pipe is subjected to lateral force, the ultimate bearing capacity of the concrete can be enhanced due to the hooping effect of the steel pipe on the main pipe; although the longitudinal stress and the circumferential stress of the concrete are inconsistent, when the concrete is damaged by punching, the damage result is assumed to occur simultaneously; assuming that a punching surface formed after the hollow steel tube concrete is damaged by lateral bearing force is a smooth curved surface; assuming that the top of the concrete cone formed by punching is circular and the bottom is elliptical; a concrete cone formed by punching is equivalent to a circular truncated cone; calculating the ultimate bearing capacity of the steel pipe corresponding to the bidirectional stiffening steel pipe T-shaped node, and further obtaining the ultimate bearing capacity of the hollow steel pipe concrete node by combining the ultimate bearing capacity of the concrete.

Description

Technical Field

[0001] The invention relates to the technical field of steel tube concrete bearing capacity, and in particular to a bearing capacity calculation method and system for a circular steel tube thin-wall hollow concrete T-shaped node. Background Art

[0002] Steel tube concrete structures are widely used in factory buildings, super high-rise buildings and other projects because of their high bearing capacity, good plasticity and toughness, economy and easy assembly, and their ability to meet the ever-increasing requirements for cross-sectional strength and fire resistance.

[0003] However, in the actual construction of power transmission and transformation towers in the power industry, it is difficult to carry out the on-site pouring process during construction, and a prefabricated component with light weight and easy transportation is necessary. Therefore, the circular steel tube thin-walled hollow concrete component was introduced, which can give full play to the mechanical properties of both steel and concrete materials, and avoid the shortcomings of the two materials when used alone. The structure has good stress resistance and relatively light weight.

[0004] A large number of experimental studies have shown that the deformation and failure process of concrete is very complex, which is closely related to the stress state of concrete. When studying the bearing capacity of T-type nodes of thin-walled hollow concrete of circular steel tubes, the node bearing capacity cannot be calculated directly according to the idea of ​​the stress of solid steel tube concrete components or the combination of steel tube concrete materials. An effective simplified calculation method is needed.

[0005] For example, the paper "Research on hollow steel tube concrete and component calculation, Zhang Sumei, Zhong Shantong. Research on hollow steel tube concrete and component calculation [J]. China Civil Engineering Journal, 1994, 27 (03): 24-32" discloses the structure of hollow steel tube concrete and the full curves corresponding to various stress states; the invention patent with publication number CN108875257A discloses a regression analysis method for the bearing capacity of N-type nodes of square steel tube trusses for piers, but it does not study the steel tube concrete structure, but only analyzes the bearing capacity of the steel tube; the invention patent with publication number CN118839435A discloses a method, system, equipment and storage medium for calculating the vertical ultimate bearing capacity of a steel structure base, the purpose of which is to calculate the vertical ultimate bearing capacity of a steel structure load-bearing base, which mainly focuses on the calculation of the vertical ultimate bearing capacity and the degree of influence of H-shaped steel plates and square steel tubes. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to solve the problems of the above-mentioned background technology and to provide a method for calculating the bearing capacity of a circular steel tube thin-walled hollow concrete T-node, and also to provide a system for calculating the bearing capacity of a circular steel tube thin-walled hollow concrete T-node.

[0007] Technical solution: According to a first aspect of the present invention, a method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node is provided, the method comprising: A concrete punching shear model corresponding to the destruction of hollow steel tube concrete nodes is constructed; the concrete punching shear model meets the following basic conditions: it is assumed that the main pipe of the circular steel tube thin-walled hollow concrete member is a structural system composed of two elements: steel tube and concrete; when subjected to shear destruction, it is assumed that the longitudinal and circumferential destruction of the concrete occurs simultaneously; it is assumed that the punching surface formed after the hollow steel tube concrete is destroyed by the lateral bearing force is a smooth curved surface; it is assumed that the concrete cone formed by the punching is round at the top and elliptical at the bottom; The concrete cone formed by the punching is equivalent to a truncated cone, and the circumferential concrete is unfolded into a concrete flat plate for calculation, and the equivalent angle between the concrete crack caused by the punching and the branch pipe, that is, the punching angle, is calculated according to the three-parameter criterion of double shear stress; The punching shear strength under the axial symmetry of the circular load is calculated according to the obtained punching shear angle, thus indicating the ultimate bearing capacity of concrete; According to the ultimate bearing capacity of the steel tube corresponding to the obtained hollow steel tube concrete T-node and combined with the ultimate bearing capacity of concrete, the ultimate bearing capacity of the hollow steel tube concrete T-node is obtained. The hollow steel tube concrete T-node includes a main pipe and a branch pipe. The cross-section of the main pipe is circular and concrete is arranged inside. The branch pipe is arranged on the main pipe and is T-shaped.

[0008] Further, including: The calculation of the equivalent angle between the concrete crack and the branch pipe caused by punching, i.e., the punching angle, according to the three-parameter criterion of double shear stress includes: The punching shear failure mode of the concrete slab is close to the ideal rigid-plastic failure, the bending effect in the structure is negligible, and the punching shear strength of the concrete is analyzed according to the double shear stress three-parameter criterion; The punching strength that meets the double shear stress three-parameter criterion is regarded as the material being destroyed, thereby obtaining the relationship between the coefficient related to the material strength in the double shear stress three-parameter criterion and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength; When the destruction cone is symmetrical about the branch axis, the corresponding double shear stress three-parameter criterion expression is obtained, and the ultimate stress circle envelope is obtained according to the annular stress in the double shear stress three-parameter criterion, thereby determining the punching angle.

[0009] Further, including: The relationship between the coefficient related to material strength and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength in the three-parameter criterion of double shear stress is obtained, including: When different normal stress influence coefficients are taken, the double shear stress three-parameter criterion can be obtained: In the formula, , , It is a coefficient related to material strength and is determined by material property tests; If one of the formulas 1 and 2 is satisfied, it means that the steel pipe and concrete materials are damaged; Assuming that concrete is an ideal rigid-plastic material, its effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength are , and , according to Kupfer test data: ,make ,but: The cohesion of concrete is obtained from the punching strength under the axial symmetry of the circular load, and then the ultimate bearing capacity of concrete is obtained.

[0010] Further, including: When the destruction cone is symmetrical about the branch pipe axis, the corresponding double shear stress three-parameter criterion expression is obtained, including: When the destruction cone is symmetrical about the branch axis, the hoop stress is , since the displacement field is axisymmetric, that is ; Assuming that the plastic deformation is small and the concrete volume is incompressible, the following can be obtained from the plastic deformation theory: Substituting Formula 3 into Formula 1 and Formula 2, we get the three-parameter criterion for double shear stress in the axisymmetric case: in: . Further, including: The method of obtaining the limit stress circle envelope according to the hoop stress in the double shear stress three-parameter criterion, thereby determining the punching angle, includes: A point M is set on the punching surface, which is a point on the limit stress circle equation G. The normal stress and shear stress of point M on the punching surface are recorded as and ; Then when The limit stress circle equation G is: Because the equation F and equation G is tangent at point M, equation and equation G are tangent at point M, then equation F is tangent to equation G and The same as equation G at point M ; where equation F refers to equation 1; equation Refers to Formula 2; From formula 4, formula 5, and formula 6, we get: Combining Formula 7 and Formula 9, we can get: Combining Formula 8 and Formula 9, we can get: Combining Formula 4 and Formula 10, we can get: Substituting Equation 12 into Equation 6, we obtain the equation for the ultimate stress circle envelope based on Equation F: in: ; Combining Formula 5 and Formula 11, we can get: Substituting Equation 14 into Equation 6, we obtain the equation of the ultimate stress circle envelope based on F: in: make When ; when hour, , , which shows and Intersect, that is, the actual limit stress circle envelope is and The enclosing polyline; when hour, , , which means that the actual limit stress circle envelope is ; For general concrete, , so the envelope of the ultimate stress circle of the concrete shear surface is ,have: After finishing, we can get: Further, including: The punching shear strength under the axial symmetry of the circular load is calculated according to the obtained punching shear angle, thereby indicating the ultimate bearing capacity of concrete, including: The area increment of the annular fracture surface caused by punching is: According to the plastic upper limit theory and related flow laws, the internal work and external work are equal and we get: Where, for the punching strength under the axisymmetric circular load, the cohesion of concrete is expressed as , After further arrangement, the ultimate bearing capacity of concrete is obtained: in, is the tensile stress of concrete; is the shear force, is the concrete diameter at the branch pipe, is the thickness of the concrete slab after unfolding, x is the displacement along the punching direction.

[0011] Further, including: The method of obtaining the ultimate bearing capacity of the hollow steel tube concrete T-node based on the obtained ultimate bearing capacity of the steel tube corresponding to the hollow steel tube T-node and combining it with the ultimate bearing capacity of the concrete includes: The ultimate bearing capacity of the hollow steel tube concrete T-node is calculated by the ultimate bearing capacity of the steel tube corresponding to the hollow steel tube T-node. and the ultimate bearing capacity of concrete Specifically: ;in, It is determined according to the ratio of the cross-sectional area of ​​the stiffening rib on the T-node of the hollow steel pipe to the branch area of ​​the hollow steel pipe.

[0012] On the other hand, the present invention also provides a bearing capacity calculation system for a circular steel tube thin-wall hollow concrete T-node, the system comprising: A model building system is used to build a concrete punching model corresponding to the destruction of a hollow steel tube concrete node; the concrete punching model meets the following basic conditions: it is assumed that the main pipe of a circular steel tube thin-walled hollow concrete member is a structural system composed of two elements, steel tube and concrete; when subjected to shearing destruction, it is assumed that the destruction results of the concrete in the longitudinal and circumferential directions occur simultaneously; it is assumed that the punching surface formed after the hollow steel tube concrete is destroyed by the lateral bearing force is a smooth curved surface; it is assumed that the concrete cone formed by the punching is round at the top and elliptical at the bottom; The punching angle calculation module is used to convert the concrete cone formed by the punching into a truncated cone, and at the same time, expand the annular concrete into a concrete flat plate for calculation, and calculate the equivalent angle between the concrete crack caused by the punching and the branch pipe according to the double shear stress three-parameter criterion, that is, the punching angle; The concrete ultimate bearing capacity calculation module is used to calculate the shear strength under the axial symmetry of the circular load according to the obtained shear angle, thereby indicating the ultimate bearing capacity of the concrete; The ultimate bearing capacity calculation module of the hollow steel tube concrete T-node is used to obtain the ultimate bearing capacity of the hollow steel tube concrete T-node according to the ultimate bearing capacity of the steel tube corresponding to the hollow steel tube concrete T-node and the ultimate bearing capacity of the concrete. The hollow steel tube concrete T-node includes a main pipe and a branch pipe. The cross-section of the main pipe is circular and concrete is arranged therein. The branch pipe is arranged on the main pipe and is T-shaped.

[0013] Further, including: The punching angle calculation module includes: Punching shear strength analysis unit: The punching shear failure mode of the concrete slab is close to the ideal rigid-plastic failure, and the bending effect in the structure is negligible. The punching shear strength of the concrete is analyzed according to the double shear stress three-parameter criterion; Relationship acquisition unit: The punching strength that meets the double shear stress three-parameter criterion is regarded as the material being destroyed, thereby obtaining the relationship between the coefficient related to the material strength in the double shear stress three-parameter criterion and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength; Punching angle calculation unit: When the destruction cone is symmetrical about the branch axis, the corresponding double shear stress three-parameter criterion expression is obtained, and the ultimate stress circle envelope is obtained according to the annular stress in the double shear stress three-parameter criterion, thereby determining the punching angle.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention proposes a bearing capacity calculation method for circular steel tube thin-wall hollow concrete T-node for the first time. The method takes into account the ultimate bearing capacity of concrete and the ultimate bearing capacity of steel tube. According to the ultimate bearing capacity of concrete, the present invention constructs a concrete shear calculation model, and on the basis of the model, the concrete shear strength is analyzed according to the double shear stress three-parameter criterion to obtain the shear angle. Finally, the ultimate bearing capacity of concrete is derived based on the shear angle, and the final bearing capacity of circular steel tube thin-wall hollow concrete T-node is obtained by combining the ultimate bearing capacity calculation result of steel tube. The calculated result of the present invention is compared and verified with the test results of nodes with corresponding size parameters and the finite element calculation results, and it is found that the method can meet the design requirements of setting circular steel tube thin-wall hollow concrete T-node, provide a reliable reference for node design in actual engineering, and is conducive to the promotion and application of steel tube thin-wall hollow concrete T-node. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A design process diagram of a method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node according to an embodiment of the present invention; Figure 2 The diagram is a comparison diagram of the punching shear model according to the embodiment of the present invention, wherein Figure (a) is a schematic diagram of the concrete punching shear model, and Figure (b) is an example diagram of damage caused by punching shear; Figure 3 This is a schematic diagram of the punching failure surface according to an embodiment of the present invention; Figure 4 Schematic diagram of a simplified model according to an embodiment of the present invention, wherein FIG (a) is a schematic diagram of a structure in which a cone-like body is equivalent to a truncated cone, and FIG (b) is a schematic diagram of a structure in which annular concrete is unfolded into a concrete flat plate; Figure 5 Schematic diagram of a T-shaped stiffened compression node according to an embodiment of the present invention, wherein Figures (a), (b), and (c) are schematic diagrams of the structure at three different viewing angles, respectively; Figure 6 This is a schematic diagram of the flat plate punching failure according to an embodiment of the present invention; The figure includes: main pipe 1, branch pipe 2, and stiffening rib 3. DETAILED DESCRIPTION

[0016] The implementation of the present invention is described in detail below in conjunction with the accompanying drawings, but it does not constitute a limitation of the present invention and is only used as an example to make the advantages of the present invention clearer and easier to understand through the description.

[0017] Referring to the detailed drawings, it can be seen that the present invention provides a method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node, such as Figure 1 As shown, the following steps are included: Step 1: Without considering the improvement of the concrete punching bearing capacity by the arch and the steel tube, this embodiment only analyzes the failure mechanism of the hollow steel tube concrete node, and the failure of the hollow steel tube concrete node can be analyzed in conjunction with the flat plate punching shear failure, such as Figure 2 The failure of steel tube concrete joints can be regarded as the superposition of two types of failure, namely, steel tube compression failure and concrete shear failure. The following basic assumptions need to be made when proposing the concrete shear calculation model: 1) First, the main pipe 1 of the circular steel tube thin-walled hollow concrete member is a structural system composed of two elements: hollow steel tube and concrete. When subjected to lateral force, the ultimate bearing capacity of concrete will be enhanced due to the hoop effect of the steel tube on it; 2) Although the longitudinal and circumferential forces on concrete are inconsistent, it is assumed that the failure results occur simultaneously when subjected to shear failure; 3) Assume that the punching surface formed after the hollow steel tube concrete is damaged by the lateral bearing force is a smooth curved surface; 4) Assume that the concrete cone formed by punching is circular at the top and elliptical at the bottom, such as Figure 3 shown.

[0018] In this embodiment, according to Figure 2 In the shape described in (a), when the branch pipe 2 is subjected to the shearing force, the top of the concrete cone is circular, and the bottom becomes elliptical due to the shearing force.

[0019] In the embodiment of the present application, because the failure of the steel tube concrete will be similar to punching only when the hollow ratio is moderate, it is closer to the test result. Figure 2 The upper ring shown in (a) is the hollow concrete section of the main pipe. When the oblique crack develops to a certain extent, C and D are the short pressure-bearing columns in the slab, which presents a spatial shell and is decomposed into two spatial shells coupled in zones I and III. Figure 2 (b) in the figure is an example, which illustrates that two compression zones, zones I and III, and one tension zone, zone II, are generated on the shear failure slope.

[0020] Step 2: Calculate the equivalent angle between the concrete crack and branch pipe 2, i.e. the punching angle Calculation.

[0021] Step 2.1: Based on the basic assumptions in step 1, in order to obtain the surface area of ​​the fracture surface of the steel pipe and concrete caused by the damage, Figure 2 This type of cone in is equivalent to a truncated cone, such as Figure 4 (a) in the figure. At the same time, the annular concrete is expanded into a concrete slab for calculation, and the original model is simplified as follows: Figure 4 As shown in (b), in this embodiment, the circle-ellipse cone is further transformed into a truncated cone, that is, the top and bottom are equivalent to circles. Since the top view of the circle-ellipse cone is axially symmetrical, the generatrix of the transformed truncated cone is the longest generatrix and the shortest generatrix. Because the lateral area of ​​a cone-like body is too complicated to solve, it must be appropriately simplified to approximate it. Compared with the more accurate numerical solution, the simplified approximation error is not large.

[0022] Step 2.2: The shear failure mode of the concrete slab is close to ideal rigid-plastic failure, and the bending effect in the structure can be ignored. The concrete shear strength is analyzed according to the double shear stress three-parameter criterion.

[0023] Step 2.2.1: When different normal stress influence coefficients are taken, the double shear stress three-parameter criterion can be obtained: In the formula, , , It is a coefficient related to material strength and is determined by material property tests.

[0024] Step 2.2.2: If one condition in the formula of step 2.2.1 is satisfied, it means that the steel pipe and concrete materials are damaged; Assuming that concrete is an ideal rigid-plastic material, its effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength are , and , according to Kupfer test data: ,make ,but ; Step 2.2.3: When the destruction cone is symmetrical about the axis of branch pipe 2, that is, in the case of axisymmetry, assume the hoop stress is Since the displacement field is axisymmetric, ; Assuming that the plastic deformation is small and the concrete volume is incompressible, the following can be obtained from the plastic deformation theory: Substituting formula 3 into formula 1 and formula 2 in step 2.2.1, we can obtain the three-parameter criterion for double shear stress in the axisymmetric case: Where: Step 2.2.4: Determine the punching angle based on the solved envelope equation .

[0025] Assume that the normal stress and shear stress at point M on the punching surface are and In this embodiment, a point M is set on the punching surface, which is a point on the limit stress circle equation G. This point M is also the limit stress circle equation G and the double shear stress three-parameter criterion equation F or A point of tangency. The limit stress circle equation G is: Because the equation F and equation G is tangent at point M, equation and equation G are tangent at point M, then equation F is tangent to equation G and The same as equation G at point M . Where, equation F refers to formula 1; equation It refers to formula 2.

[0026] From formula 4, formula 5, and formula 6, we can get: Combining Formula 7 and Formula 9, we can get: Combining formula 8 and formula 9, we can get: Combining Formula 4 and Formula 10, we can get: Substituting Formula 12 into Formula 6, the equation of the ultimate stress circle envelope based on F can be obtained: Where: Combining Formula 5 and Formula 11, we can get: Substituting Formula 14 into Formula 6, the equation of the ultimate stress circle envelope based on F can be obtained: Where: make , the solution is .

[0027] when hour, , , which shows and Intersect, that is, the actual limit stress circle envelope is and The enclosing polyline.

[0028] when hour, , , which means that the actual limit stress circle envelope is .

[0029] For general concrete, , so the envelope of the ultimate stress circle of the concrete shear surface is ,have: After finishing, we can get: Step 3: Based on the punching angle solved in step 2 Derive and calculate the formula for the ultimate bearing capacity of concrete.

[0030] The area increment of the annular fracture surface caused by punching is: According to the plastic upper limit theory and related flow laws, the internal work and external work are equal and we get: like Figure 6 As shown in the figure, for the punching shear strength under the axial symmetry of the circular load, the hoop strain can be approximately considered as , the cohesion of concrete can be expressed as , is the tensile stress of concrete; is the shear force, is the diameter of branch pipe 2, is the thickness of the concrete slab after unfolding, x is the displacement along the punching direction.

[0031] Further sorting out the calculation formula of concrete ultimate bearing capacity: Step 4: Calculation of the ultimate bearing capacity of the steel pipe. This embodiment does not limit the specific steel pipe structure, as long as the cross-section of the main pipe 1 is circular and concrete is arranged inside it, and the branch pipe 2 is arranged on the main pipe 1 and is T-shaped.

[0032] Specifically, in this embodiment, a bidirectional stiffened steel pipe T-type node is taken as an example, and the calculation is performed according to the compression formula of the stiffening rib 3, such as Figure 5 As shown, it includes a circular main pipe 1, a branch pipe 2 and a stiffening rib 3. The main pipe 1 and the branch pipe 2 are designed in a T shape. The setting direction of the stiffening rib 3 is consistent with that of the branch pipe 2, and is used to fix the main pipe 1 and the branch pipe 2. In this embodiment, a total of 4 identical stiffening ribs 3 are set, and the stiffening ribs 3 in four directions are arranged around the outer circumference of the branch pipe 2.

[0033] Based on the above structure, the calculation formula of the first ultimate bearing capacity is: in, is the discriminant coefficient, such as Figure 5 As shown in (a), (b) and (c), C is the width of the stiffening rib 3, and D is the outer diameter of the main pipe 1. is the radius of main tube 1, is the wall thickness of main pipe 1, is the thickness of the stiffening rib 3, R is the height of the main pipe 1, is the yield strength of the steel pipe; To obtain the effective amplitude of the stiffening rib 3 according to the Thurlimann calculation theory formula.

[0034] When the determination coefficient When: The second ultimate bearing capacity is expressed as: When the coefficient of determination When in, is the yield strength of stiffener 3, the ultimate bearing capacity of the steel pipe The first ultimate bearing capacity and the second ultimate bearing capacity In this embodiment, the first ultimate bearing capacity is is the bearing capacity of main pipe 1 under pipe wall failure, the second ultimate bearing capacity is the bearing capacity under the failure of stiffener 3. Step 5: Combining the formulas of step 3 and step 4, the ultimate bearing capacity of the hollow steel tube concrete node is obtained: In the formula, It is determined according to the ratio of the cross-sectional area of ​​the stiffening rib 3 to the area of ​​the branch pipe 2. For the steel tube concrete without stiffening ribs, it is taken as 1, and for the steel tube concrete with stiffening ribs, that is, in this embodiment, it is taken as 1.2.

[0035] On the other hand, the present invention also provides a bearing capacity calculation system for a circular steel tube thin-wall hollow concrete T-node, the system comprising: A model building system is used to build a concrete punching model corresponding to the destruction of a hollow steel tube concrete node; the concrete punching model meets the following basic conditions: it is assumed that the main pipe of a circular steel tube thin-walled hollow concrete member is a structural system composed of two elements, steel tube and concrete; when subjected to shearing destruction, it is assumed that the destruction results of the concrete in the longitudinal and circumferential directions occur simultaneously; it is assumed that the punching surface formed after the hollow steel tube concrete is destroyed by the lateral bearing force is a smooth curved surface; it is assumed that the concrete cone formed by the punching is round at the top and elliptical at the bottom; The punching angle calculation module is used to convert the concrete cone formed by the punching into a truncated cone, and at the same time, expand the annular concrete into a concrete flat plate for calculation, and calculate the equivalent angle between the concrete crack caused by the punching and the branch pipe according to the double shear stress three-parameter criterion, that is, the punching angle; The concrete ultimate bearing capacity calculation module is used to calculate the shear strength under the axial symmetry of the circular load according to the obtained shear angle, thereby indicating the ultimate bearing capacity of the concrete; The ultimate bearing capacity calculation module of the hollow steel tube concrete T-node is used to obtain the ultimate bearing capacity of the hollow steel tube concrete T-node according to the ultimate bearing capacity of the steel tube corresponding to the hollow steel tube concrete T-node and the ultimate bearing capacity of the concrete. The hollow steel tube concrete T-node includes a main pipe and a branch pipe. The cross-section of the main pipe is circular and concrete is arranged therein. The branch pipe is arranged on the main pipe and is T-shaped.

[0036] Furthermore, it includes: The punching angle calculation module includes: Punching strength analysis unit: The punching failure mode of the concrete slab is close to ideal rigid-plastic failure. The bending effect in the structure is ignored, and the punching strength of the concrete is analyzed according to the three-parameter criterion of double shear stress. Relationship obtaining unit: The punching strength that conforms to the three-parameter criterion of double shear stress is regarded as the material being damaged, so as to obtain the relationship between the coefficient related to the material strength in the three-parameter criterion of double shear stress and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial equal-compression strength. Punching angle calculation unit: When the failure cone is symmetric about the axis of the branch pipe, the corresponding representation form of the three-parameter criterion of double shear stress is obtained, and the envelope line of the limit stress circle is obtained according to the circumferential stress in the three-parameter criterion of double shear stress, so as to determine the punching angle.

[0037] Other technical features of the bearing capacity calculation system of the circular steel tube thin-walled hollow concrete T-joint described in this embodiment are similar to the corresponding bearing capacity calculation method of the circular steel tube thin-walled hollow concrete T-joint, and will not be elaborated here.

[0038] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0039] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concepts. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0040] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and variations.

Claims

1. A method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-joint, characterized in that: The method includes: A concrete punching shear model corresponding to the destruction of hollow steel tube concrete T-type node is constructed; the concrete punching shear model meets the following conditions: it is assumed that the main pipe of the circular steel tube thin-wall hollow concrete T-type node is a structural system composed of two elements: steel tube and concrete; when subjected to shear destruction, it is assumed that the longitudinal and circumferential destruction of the concrete occurs simultaneously; it is assumed that the punching surface formed after the hollow steel tube concrete is destroyed by the lateral bearing force is a smooth curved surface; it is assumed that the concrete cone formed by the punching is round at the top and elliptical at the bottom; The concrete cone formed by the punching is equivalent to a truncated cone, and the circumferential concrete is expanded into a concrete flat plate, and the equivalent angle between the concrete crack caused by the punching and the branch pipe, that is, the punching angle, is calculated according to the three-parameter criterion of double shear stress; The punching shear strength under the axial symmetry of the circular load is calculated according to the obtained punching shear angle, thus indicating the ultimate bearing capacity of concrete; According to the obtained ultimate bearing capacity of the steel tube corresponding to the hollow steel tube concrete T-node, the ultimate bearing capacity of the hollow steel tube concrete T-node is obtained in combination with the ultimate bearing capacity of the concrete. The hollow steel tube concrete T-node includes a main pipe, a branch pipe and a stiffening rib. The cross-section of the main pipe is circular, the branch pipe and the main pipe are fixed in a T shape, and the stiffening rib is used to strengthen the connection between the main pipe and the branch pipe.

2. The method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node according to claim 1 is characterized in that: The calculation of the equivalent angle between the concrete crack and the branch pipe caused by punching, i.e., the punching angle, according to the three-parameter criterion of double shear stress includes: The punching shear failure mode of concrete slab is close to ideal rigid-plastic failure, and the punching shear strength of concrete is analyzed according to the double shear stress three-parameter criterion. If the punching strength meets the double shear stress three-parameter criterion, the material is considered to be destroyed, thus obtaining the relationship between the coefficient related to the material strength in the double shear stress three-parameter criterion and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength; When the destruction cone is symmetrical about the branch axis, the corresponding double shear stress three-parameter criterion expression is obtained, and the ultimate stress circle envelope is obtained according to the annular stress in the double shear stress three-parameter criterion, thereby determining the punching angle.

3. The method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node according to claim 2 is characterized in that: The relationship between the coefficient related to material strength and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength in the three-parameter criterion of double shear stress is obtained, including: When different normal stress influence coefficients are taken, the double shear stress three-parameter criterion can be obtained: In the formula, , , It is a coefficient related to material strength and is determined by material property tests; If one of the formulas 1 and 2 is satisfied, it means that the steel pipe and concrete materials are damaged; Assuming that concrete is an ideal rigid-plastic material, its effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength are , and , according to Kupfer test data: ,make ,but: The cohesion of concrete is obtained from the punching strength under the axisymmetric condition of circular load, and then the ultimate bearing capacity of concrete is obtained.

4. The method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node according to claim 3 is characterized in that: When the destruction cone is symmetrical about the branch pipe axis, the corresponding double shear stress three-parameter criterion expression is obtained, including: When the destruction cone is symmetrical about the branch axis, the hoop stress is , since the displacement field is axisymmetric, that is ; Assuming that the plastic deformation is small and the concrete volume is incompressible, the following is obtained from the plastic deformation theory: Substituting Formula 3 into Formula 1 and Formula 2, we obtain the three-parameter criterion for double shear stress in the axisymmetric case: in: .

5. The method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node according to claim 4 is characterized in that: The method of obtaining the limit stress circle envelope according to the hoop stress in the double shear stress three-parameter criterion, thereby determining the punching angle, includes: A point M is set on the punching surface, which is a point on the limit stress circle equation G. The normal stress and shear stress of point M on the punching surface are recorded as and ; Then when The limit stress circle equation G is: Because the equation F and equation G is tangent at point M, equation and equation G are tangent at point M, then equation F is tangent to equation G and The same as equation G at point M ; where equation F refers to equation 1; equation Refers to Formula 2; From formula 4, formula 5, and formula 6, we get: Combining Formula 7 and Formula 9, we can get: Combining formula 8 and formula 9, we can get: Combining Formula 4 and Formula 10, we can get: Substituting Equation 12 into Equation 6, we obtain the equation for the ultimate stress circle envelope based on Equation F: in: Combining Formula 5 and Formula 11, we can get: Substituting Equation 14 into Equation 6, we obtain the equation of the ultimate stress circle envelope based on F: in: make When ;when hour, , which shows and Intersect, that is, the actual limit stress circle envelope is and The enclosing polyline; when hour, , , which means that the actual limit stress circle envelope is ; When the ultimate stress circle envelope of the concrete punching surface is Sometimes: Then, according to formula 17, the corresponding punching angle is obtained: .

6. The method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-node according to claim 5 is characterized in that: The punching shear strength under the axial symmetry of the circular load is calculated according to the obtained punching shear angle, thereby indicating the ultimate bearing capacity of concrete, including: The area increment of the annular fracture surface caused by punching is: According to the plastic upper limit theory and related flow laws, the internal work and external work are equal and we get: Where, for the punching strength under the axisymmetric circular load, the cohesion of concrete is expressed as , After further arrangement, the ultimate bearing capacity of concrete is obtained: in, is the tensile stress of concrete; is the shear force, is the concrete diameter at the branch pipe, is the thickness of the concrete slab after unfolding, x is the displacement along the punching direction.

7. The method for calculating the bearing capacity of a circular steel tube thin-wall hollow concrete T-joint according to claim 6, characterized in that: The method of obtaining the ultimate bearing capacity of the hollow steel tube concrete T-node based on the ultimate bearing capacity of the steel tube corresponding to the hollow steel tube T-node and combining it with the ultimate bearing capacity of concrete includes: The ultimate bearing capacity of the hollow steel tube concrete T-node is calculated by the ultimate bearing capacity of the steel tube corresponding to the hollow steel tube T-node. and the ultimate bearing capacity of concrete Specifically: in, It is determined according to the ratio of the cross-sectional area of ​​the stiffening rib on the hollow steel pipe T-node to the branch pipe area.

8. A bearing capacity calculation system for circular steel tube thin-wall hollow concrete T-joints, characterized in that: The system includes: a model building system for building a concrete punching model corresponding to the destruction of a hollow steel tube concrete T-type node; the concrete punching model meets the following conditions: it is assumed that the main pipe of the circular steel tube thin-wall hollow concrete T-type node is a structural system composed of two elements, steel tube and concrete; when subjected to punching destruction, it is assumed that the destruction results of the concrete in the longitudinal direction and the circumferential direction occur simultaneously; it is assumed that the punching surface formed after the hollow steel tube concrete is destroyed by the lateral bearing force is a smooth curved surface; it is assumed that the concrete cone formed by the punching is round at the top and elliptical at the bottom; The punching angle calculation module is used to convert the concrete cone formed by the punching into a truncated cone, and at the same time, expand the annular concrete into a concrete flat plate for calculation, and calculate the equivalent angle between the concrete crack caused by the punching and the branch pipe according to the double shear stress three-parameter criterion, that is, the punching angle; The concrete ultimate bearing capacity calculation module is used to calculate the shear strength under the axial symmetry of the circular load according to the obtained shear angle, thereby indicating the ultimate bearing capacity of the concrete; The ultimate bearing capacity calculation module of the hollow steel tube concrete T-node is used to obtain the ultimate bearing capacity of the hollow steel tube concrete T-node according to the ultimate bearing capacity of the steel tube corresponding to the hollow steel tube concrete T-node and the ultimate bearing capacity of the concrete. The hollow steel tube concrete T-node includes a main pipe, a branch pipe and a stiffening rib. The cross-section of the main pipe is circular, the branch pipe and the main pipe are fixed in a T shape, and the stiffening rib is used to strengthen the connection between the main pipe and the branch pipe.

9. The bearing capacity calculation system of circular steel tube thin-wall hollow concrete T-node according to claim 8 is characterized in that: The punching angle calculation module includes: Punching shear strength analysis unit, used to make the punching failure mode of concrete slab close to ideal rigid-plastic failure, and analyze the punching shear strength of concrete according to the double shear stress three-parameter criterion; A relationship obtaining unit is used to determine that when the punching strength meets the double shear stress three-parameter criterion, the material is regarded as being destroyed, thereby obtaining the relationship between the coefficient related to the material strength in the double shear stress three-parameter criterion and the effective uniaxial tensile strength, uniaxial compressive strength and biaxial isostatic strength; The punching angle calculation unit is used to obtain the corresponding double shear stress three-parameter criterion representation when the destruction cone is symmetrical about the branch axis, and obtain the ultimate stress circle envelope according to the annular stress in the double shear stress three-parameter criterion, so as to determine the punching angle.

Images