Longitudinal shear calculation method and system of steel-concrete composite beam in structural system conversion process

Abstract

The application discloses a longitudinal shear calculation method and system of a steel-concrete composite beam in a structural system conversion process, and the method comprises the following steps: obtaining vertical shears of the steel-concrete composite beam structural system before and after a structural system conversion at a target calculation section; calculating a vertical shear variation caused by the structural system conversion; obtaining a combined section inertia moment of the steel-concrete composite beam at the target calculation section and an area moment of a combined section neutral axis; taking the vertical shear variation as a core parameter for representing the structural system conversion, combining section geometric characteristics defined by the combined section inertia moment and the area moment, and calculating a steel-concrete combination surface longitudinal shear caused by the structural system conversion process on a unit length according to a section internal force balance and a shear stress calculation rule. The application solves the problem that the existing design specification does not consider the influence of the structural system conversion process on the longitudinal shear distribution in the calculation of the longitudinal shear in the construction stage, so that the calculation result is greatly deviated from the actual situation.

Description

Technical Field

[0001] This invention relates to the field of composite beam technology, specifically to a method and system for calculating longitudinal shear force in steel-concrete composite beams during structural system transformation. Background Technology

[0002] Steel-concrete composite beam structures are widely used in modern bridges and building structures due to their superior mechanical properties and ease of construction. In actual engineering projects, a structural system transformation process is required. For example, in the construction of long-span prefabricated steel-concrete composite beam bridges, steel beams are first erected in sections, then spliced ​​and welded together, followed by the pouring of concrete bridge decks. After the concrete has solidified, the temporary supports are removed, completing the system transformation from individual steel beam load-bearing to composite section load-bearing.

[0003] Currently, the methods for calculating longitudinal shear force in engineering practice mainly rely on existing design codes. These codes specify the main parameters of longitudinal shear force as the vertical shear force acting on the composite beam after the composite section is formed, the area moment of the concrete slab about the neutral axis of the composite section, and the moment of inertia of the composite section. However, existing code calculation methods do not consider the impact of the structural system transformation process on the distribution of longitudinal shear force, leading to significant deviations between the calculated results and actual conditions. Therefore, there is an urgent need for a method that can accurately calculate the longitudinal shear force during the transformation of steel-concrete composite beam structural systems. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for calculating longitudinal shear force in steel-concrete composite beams during structural system transformation, in order to solve the problem that existing design codes do not consider the impact of structural system transformation on the distribution of longitudinal shear force during the construction stage, resulting in a large deviation between the calculated results and the actual situation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The method for calculating the longitudinal shear force of steel-concrete composite beams during structural system transformation includes the following steps: S1: Obtain the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section; S2: Based on the vertical shear forces obtained before and after the transformation of the steel-concrete composite beam structure system, calculate the change in vertical shear force caused by the transformation of the structure system; S3: Obtain the moment of inertia of the composite section of the steel-concrete composite beam at the target calculation section, and the area moment of the concrete slab about the neutral axis of the composite section in the steel-concrete composite beam structure; S4: Using the change in vertical shear force as the core parameter characterizing the structural system transformation, and combining the cross-sectional geometric properties defined by the moment of inertia and area moment of the combined section, the longitudinal shear force of the steel-concrete composite surface caused by the structural system transformation process per unit length is calculated according to the rules for calculating the internal force balance and shear stress of the cross-section.

[0006] To optimize the above technical solution, the specific limitations also include: In step S1, the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section is obtained by establishing a finite element calculation model of the steel-concrete composite beam and simulating its structural system transformation process.

[0007] Preferably, the conversion process of the steel-concrete composite beam structure system is a process in which the steel beam is subjected to stress alone and the steel-concrete composite structure is subjected to stress together during the construction phase, including erecting temporary supports, erecting steel beams, pouring concrete slabs, and removing temporary supports.

[0008] Preferably, the structural system transformation process simulated in the finite element calculation model includes the simulation of temporary construction loads, concrete shrinkage and creep effects, and prestressing tensioning procedures.

[0009] Preferably, the finite element calculation model is constructed using general-purpose finite element software, including one of Midas / Civil, ANSYS, ABAQUS, or SAP2000.

[0010] Furthermore, the calculation formula for the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process is as follows:

[0011] in, This refers to the longitudinal shear force per unit length at the steel-concrete interface caused during the structural system transformation process. This represents the change in vertical shear force. For the moment of inertia of the composite section, Let be the area moment of the concrete slab about the neutral axis of the composite section.

[0012] Furthermore, the total longitudinal shear force during the structural system conversion process is the sum of the longitudinal shear force per unit length caused by the structural system conversion process at the steel-concrete interface, the longitudinal shear force caused by subsequent loads after the structural system conversion is completed, and the longitudinal shear force caused by concrete shrinkage and creep and prestressing.

[0013] Further, in step S4, after calculating the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process, the results are verified. Specific verification steps include: Select the axial length of the beam at the target calculation section A concrete slab with two cross-sections of aa and bb ; The longitudinal shear force per unit length is obtained based on the principle of static equilibrium, and the calculation formula is as follows:

[0014] in, The horizontal force includes the longitudinal shear force at the joint surface between the concrete slab and the steel beam. For the cross section of the concrete slab Axial pressure after system transformation; For the cross section of the concrete slab Axial pressure after system transformation; , In the opposite direction; The accuracy of the calculation results is verified by comparing the verified value of the longitudinal shear force per unit length with the calculated longitudinal shear force at the steel-concrete interface caused by the structural system transformation process per unit length.

[0015] This invention also proposes a longitudinal shear force calculation system for steel-concrete composite beams during structural system transformation, characterized by comprising: The data acquisition module is used to acquire the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section, as well as the moment of inertia of the composite section and the area moment of the concrete slab about the neutral axis of the composite section at the target calculation section. The core calculation module is used to calculate the change in vertical shear force caused by the transformation of the steel-concrete composite beam structure system before and after the transformation, based on the obtained vertical shear force before and after the transformation. Using the change in vertical shear force as the core parameter characterizing the transformation of the structure system, and combining the cross-sectional geometric properties defined by the moment of inertia and area moment of the composite section, the module calculates the longitudinal shear force per unit length of the steel-concrete composite surface caused by the transformation process of the structure system according to the rules of cross-sectional internal force balance and shear stress calculation. The output module is used to output and display the longitudinal shear force per unit length at the steel-concrete interface caused by the calculated structural system transformation process.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a method and system for calculating longitudinal shear force of steel-concrete composite beams during structural system transformation. By introducing the change in vertical shear force before and after structural system transformation as the core calculation parameter, it accurately quantifies the influence of the structural system transformation process itself on the stress on the steel-concrete interface during the construction stage. In principle, it corrects the incompleteness of the physical model in the transient working conditions of structural system transformation in existing standard methods, so that the calculation results can more realistically reflect the actual mechanical behavior of the structure during construction.

[0017] This invention provides a safer and more reliable basis for the design of shear-resistant connectors by proposing a calculation method for the additional longitudinal shear force generated during the system transformation process, which is easily overlooked. This avoids potential structural safety hazards caused by underestimating shear force and improves the long-term safety margin of bridges during construction and in their completed state. Furthermore, this invention proposes a complete technical process from finite element simulation to theoretical calculation and independent verification, effectively demonstrating the correctness of the proposed longitudinal shear force calculation method and the reliability of the results. This fills the current gap in longitudinal shear force calculation during system transformation processes both domestically and internationally, and has significant engineering application value for ensuring the construction safety and long-term structural performance of large-span composite beam bridges. Attached Figure Description

[0018] Figure 1 : A flowchart illustrating the longitudinal shear force calculation method for the steel-concrete composite beam during the structural system transformation process of the present invention.

[0019] Figure 2 : Cross-sectional view of the steel-concrete composite beam of the present invention, wherein (a) is an elevation view of the steel-concrete composite beam and (b) is a cross-sectional view of the steel-concrete composite beam.

[0020] Figure 3 : Schematic diagram of the longitudinal shear force calculation principle of the steel-concrete composite beam of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0022] In one embodiment, this invention proposes a method for calculating the longitudinal shear force of steel-concrete composite beams during structural system transformation, as shown in the flowchart below. Figure 1 As shown, the entire method includes the following steps: S1: Obtain the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section; S2: Based on the obtained vertical shear forces before and after the transformation of the steel-concrete composite beam structure system, calculate the change in vertical shear force caused by the transformation of the structure system; S3: Obtain the moment of inertia of the composite section of the steel-concrete composite beam at the target calculation section, and the area moment of the concrete slab about the neutral axis of the composite section in the steel-concrete composite beam structure; S4: Taking the change in vertical shear force as the core parameter characterizing the structural system transformation, and combining the cross-sectional geometric properties defined by the moment of inertia and area moment of the combined section, the longitudinal shear force of the steel-concrete interface caused per unit length during the structural system transformation process is calculated according to the rules for calculating the internal force balance and shear stress of the cross-section.

[0023] In step S1, the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section is obtained by establishing a finite element calculation model of the steel-concrete composite beam and simulating its structural system transformation process.

[0024] The transformation process of a steel-concrete composite beam structure system refers to the process during construction from a state where the steel beams are subjected to individual stress to a state where the steel-concrete composite structure is subjected to joint stress. This includes the erection of temporary supports, the erection of steel beams, the pouring of concrete slabs, and the removal of temporary supports. The structural transformation process simulated in the finite element method (FEM) model includes the simulation of temporary construction loads, concrete shrinkage and creep effects, and the prestressing tensioning process. The FEM model is constructed using general-purpose finite element software, including one of Midas / Civil, ANSYS, ABAQUS, or SAP2000.

[0025] In step S4, the longitudinal shear force at the steel-concrete interface per unit length caused by the structural system transformation process is calculated based on the principles of mechanics of materials. This specifically includes the following steps: Based on the finite element method model, the vertical shear force of the structural system before the transformation is obtained. ; Based on the finite element method model, the vertical shear force of the transformed structural system is obtained. ; Calculate the change in vertical shear force :

[0026] The formula for calculating the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process is as follows:

[0027] in, This refers to the longitudinal shear force per unit length at the steel-concrete interface caused during the structural system transformation process. This represents the change in vertical shear force. For the moment of inertia of the composite section, Let be the area moment of the concrete slab about the neutral axis of the composite section.

[0028] The total longitudinal shear force during the structural system conversion process is the sum of the longitudinal shear force per unit length caused by the structural system conversion process at the steel-concrete interface, the longitudinal shear force caused by subsequent loads after the structural system conversion is completed, and the longitudinal shear force caused by concrete shrinkage and creep and prestressing.

[0029] In step S4, after calculating the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process, the results are verified. The specific verification steps include: Select the axial length of the beam at the target calculation section A concrete slab with two cross-sections of aa and bb ; According to the principle of static equilibrium, the resultant force in the horizontal direction is zero, specifically:

[0030] The verification value of longitudinal shear force per unit length is obtained by the following formula:

[0031] in, The horizontal force includes the longitudinal shear force at the joint surface between the concrete slab and the steel beam. For the cross section of the concrete slab Axial pressure after system transformation; For the cross section of the concrete slab Axial pressure after system transformation; , In the opposite direction; Before system transformation, the bending moment of the composite section The resulting compressive stress acts entirely on the upper flange of the steel beam, while the compressive stress at the concrete slab is zero; after system transformation, the bending moment at the combined section is... Only The resulting compressive stress acts on the concrete slab; therefore, the cross-section of the concrete slab... , Axial pressure , They are respectively: =

[0032]

[0033] in, For the cross section of the concrete slab The compressive stress after the system transformation; For the cross section of the concrete slab The compressive stress after the system transformation; Composite section Bending moment after system transformation; Composite section Bending moment after system transformation; Composite section Bending moment before system transformation; Composite section Bending moment before system transformation; The moment of inertia of the composite section; The distance from the neutral axis of the composite section to any point on the concrete slab section; The width of the concrete slab cross section; The expression for the longitudinal shear force per unit length is as follows:

[0034] in, Let S be the area moment of the concrete slab about the neutral axis of the composite section, then we have: .

[0035] By applying the principle of static equilibrium of micro-segments of concrete slabs to decompose and substitute the internal forces of the cross-section, an expression for calculating the longitudinal shear force per unit length is derived. This theoretically proves that the formula for calculating the longitudinal shear force per unit length of the steel-concrete interface caused by the structural system transformation process is a direct deduction and concrete manifestation of the basic principles of mechanics of materials and structural mechanics under specific working conditions of structural system transformation, thus ensuring the reliability of the calculation.

[0036] The method provided by this invention can be extended to novel material composite structures, including longitudinal shear force calculation in UHPC-steel composite beams, UHPC-concrete composite beams, and fiber-reinforced concrete-steel composite beams.

[0037] This invention also proposes a longitudinal shear force calculation system for steel-concrete composite beams during structural system transformation, comprising: The data acquisition module is used to acquire the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section, as well as the moment of inertia of the composite section and the area moment of the concrete slab about the neutral axis of the composite section at the target calculation section. The core calculation module is used to calculate the change in vertical shear force caused by the structural system transformation based on the vertical shear force obtained before and after the transformation of the steel-concrete composite beam structure system. Using the change in vertical shear force as the core parameter characterizing the structural system transformation, and combining the cross-sectional geometric properties defined by the moment of inertia and area moment of the composite section, the module calculates the longitudinal shear force per unit length of the steel-concrete interface caused by the structural system transformation process according to the rules for calculating the internal force balance and shear stress of the cross-section. The output module is used to output and display the longitudinal shear force per unit length at the steel-concrete interface caused by the calculated structural system transformation process.

[0038] To further understand the technical solution of the present invention, a detailed description is provided in conjunction with specific embodiments: A three-dimensional finite element model of the steel-concrete composite beam was created using the general-purpose finite element software Midas / Civil. In the model, the concrete slab was simulated using plate elements, and the steel beam was simulated using beam elements. Shear connection components were also accurately constructed.

[0039] The bridge is a 50m span, uniform cross-section steel-concrete composite simply supported beam bridge. The bridge is 50m long and 24.5m wide. The steel-concrete composite beam adopts a combined structure of channel steel box girders and concrete bridge deck. During construction, the 50m steel beam is divided into three sections of 15m, 20m, and 15m for segmented erection. The first step involves erecting temporary supports and hoisting the 15m channel steel box girders at both ends, followed by hoisting the 20m channel steel box girder in the middle section and completing the assembly of the three steel beam segments. The second step is to pour the concrete slab. The third step is to remove the temporary supports to complete the system transformation; this process represents the conversion of the structural system from individual steel beam load-bearing to composite beam load-bearing.

[0040] Ten consecutive elements are randomly selected from a steel-concrete composite beam, with each element having a length of... =1m, based on the finite element calculation model, obtain the vertical shear force of the steel-concrete composite beam structure system before transformation at the target calculation section. Vertical shear force after conversion and the combined moment of inertia of the target calculated section and the area moment of the concrete slab about the neutral axis of the composite section ; The longitudinal shear force of each element was calculated based on the formula for calculating the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process, and the results are summarized in Table 1, as follows: Table 1 Calculated values ​​of longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process.

[0041] Note: Area moment of the neutral axis of the composite section Moment of inertia of composite section I .

[0042] Draw a schematic diagram of a steel-concrete composite beam, such as... Figure 2 As shown in Figures (a) and (b), a small section of the concrete slab is taken. Analysis was conducted, and its two cross-sections were... aa and bb ; According to the principle of static equilibrium, the resultant force in the horizontal direction is zero, specifically:

[0043] The verification value of longitudinal shear force per unit length is obtained by the following formula:

[0044] in, The horizontal force includes the longitudinal shear force at the joint surface between the concrete slab and the steel beam. For the cross section of the concrete slab Axial pressure after system transformation; For the cross section of the concrete slab Axial pressure after system transformation; , In the opposite direction; like Figure 3 As shown, before the system transformation, the bending moment of the composite section... The resulting compressive stress acts entirely on the upper flange of the steel beam, while the compressive stress at the concrete slab is zero; after system transformation, the bending moment at the combined section is... Only The resulting compressive stress acts on the concrete slab; therefore, the cross-section of the concrete slab... , Axial pressure , They are respectively: =

[0045]

[0046] in, For the cross section of the concrete slab The compressive stress after the system transformation; For the cross section of the concrete slab The compressive stress after the system transformation; Composite section Bending moment after system transformation; Composite section Bending moment after system transformation; Composite section Bending moment before system transformation; Composite section Bending moment before system transformation; The moment of inertia of the composite section; The distance from the neutral axis of the composite section to any point on the concrete slab section; The width of the concrete slab cross section; Ten identical elements were selected during the calculation of the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process. Each element has a length dx = 1m. The verified values ​​of the longitudinal shear force per unit length are shown in the table below: Table 2 Verification values ​​of longitudinal shear force per unit length calculated based on the principle of static equilibrium.

[0047] Note: Units 6# to 10# are composite beams located in the middle section between temporary supports. After the temporary supports are removed, the axial pressure on the concrete slab is the same. Therefore, the longitudinal shear force per unit length is approximately 0.

[0048] The longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process is summarized in the table below, along with its verification value. The error between the two values ​​is calculated. Table 3. Longitudinal shear force per unit length and verification value

[0049] Note: The longitudinal shear force per unit length for units 6# to 10# is approximately zero and is not included in the comparison results. As shown in the table above, the longitudinal shear force per unit length for units 1# to 5# has an error of approximately 5%, verifying the formula. The accuracy.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation, characterized in that... Includes the following steps: S1: Obtain the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section; S2: Based on the vertical shear forces obtained before and after the transformation of the steel-concrete composite beam structure system, calculate the change in vertical shear force caused by the transformation of the structure system; S3: Obtain the moment of inertia of the composite section of the steel-concrete composite beam at the target calculation section, and the area moment of the concrete slab about the neutral axis of the composite section in the steel-concrete composite beam structure; S4: Using the change in vertical shear force as the core parameter characterizing the structural system transformation, and combining the cross-sectional geometric properties defined by the moment of inertia and area moment of the combined section, the longitudinal shear force of the steel-concrete composite surface caused by the structural system transformation process per unit length is calculated according to the rules for calculating the internal force balance and shear stress of the cross-section.

2. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 1, characterized in that: In step S1, the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section is obtained by establishing a finite element calculation model of the steel-concrete composite beam and simulating its structural system transformation process.

3. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 2, characterized in that: The transformation process of the steel-concrete composite beam structure system is the process of changing from the state of steel beams being subjected to stress alone to the state of steel-concrete composite structure being subjected to stress together during the construction phase. It includes erecting temporary supports, erecting steel beams, pouring concrete slabs, and removing temporary supports.

4. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 2, characterized in that: The structural system transformation process simulated in the finite element calculation model includes the simulation of temporary construction loads, concrete shrinkage and creep effects, and prestressing tensioning procedures.

5. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 2, characterized in that: The finite element calculation model is constructed using general-purpose finite element software, including one of Midas / Civil, ANSYS, ABAQUS, or SAP2000.

6. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 1, characterized in that: The calculation formula for the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process is as follows: in, This refers to the longitudinal shear force per unit length at the steel-concrete interface caused during the structural system transformation process. This represents the change in vertical shear force. For the moment of inertia of the composite section, Let be the area moment of the concrete slab about the neutral axis of the composite section.

7. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 1, characterized in that: The total longitudinal shear force during the structural system conversion process is the sum of the longitudinal shear force per unit length caused by the structural system conversion process at the steel-concrete interface, the longitudinal shear force caused by subsequent loads after the structural system conversion is completed, and the longitudinal shear force caused by concrete shrinkage and creep and prestressing.

8. The method for calculating the longitudinal shear force of a steel-concrete composite beam during structural system transformation according to claim 1, characterized in that: In step S4, after calculating the longitudinal shear force per unit length at the steel-concrete interface caused by the structural system transformation process, the results are verified. Specific verification steps include: Select the axial length of the beam at the target calculation section A concrete slab with two cross-sections of aa and bb ; The longitudinal shear force per unit length is obtained based on the principle of static equilibrium, and the calculation formula is as follows: in, The horizontal force includes the longitudinal shear force at the joint surface between the concrete slab and the steel beam. For the cross section of the concrete slab Axial pressure after system transformation; For the cross section of the concrete slab Axial pressure after system transformation; , In the opposite direction; The accuracy of the calculation results is verified by comparing the verified value of the longitudinal shear force per unit length with the calculated longitudinal shear force at the steel-concrete interface caused by the structural system transformation process per unit length.

9. A longitudinal shear force calculation system for steel-concrete composite beams during structural system transformation, characterized in that, include: The data acquisition module is used to acquire the vertical shear force of the steel-concrete composite beam structure system before and after the transformation at the target calculation section, as well as the moment of inertia of the composite section and the area moment of the concrete slab about the neutral axis of the composite section at the target calculation section. The core calculation module is used to calculate the change in vertical shear force caused by the transformation of the steel-concrete composite beam structure system before and after the transformation, based on the obtained vertical shear force before and after the transformation. Using the change in vertical shear force as the core parameter characterizing the transformation of the structure system, and combining the cross-sectional geometric properties defined by the moment of inertia and area moment of the composite section, the module calculates the longitudinal shear force per unit length of the steel-concrete composite surface caused by the transformation process of the structure system according to the rules of cross-sectional internal force balance and shear stress calculation. The output module is used to output and display the longitudinal shear force per unit length at the steel-concrete interface caused by the calculated structural system transformation process.

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