Large-span arch bridge dead load and long-term effect bending moment amplitude modulation method based on axial compression compensation

Abstract

The invention discloses a large-span arch bridge dead load and long-term effect bending moment amplitude modulation method based on axial compression compensation, and is applied to the technical field of bridge engineering. Comprising the following steps: establishing a large-span arch bridge rod system unit model according to design parameters; respectively calculating arch ring vault internal force caused by dead load, contraction and creep; solving the axial compression amount of the arch ring caused by dead load, temperature, shrinkage and creep; the initial axial compression compensation amount of the closure opening is calculated; the total internal force of the structure under the ten-year creep effect after the initial axial compression compensation amount of the closure opening is applied is calculated; judging whether the ratio of the internal force to the initial dead load internal force is smaller than a threshold value or not, and if yes, performing iterative calculation until the ratio is smaller than the threshold value; and outputting the final length compensation amount of the closure gap for guiding construction closure. According to the method, the compensation amount is preset in the closure stage, the axial compression effect caused by dead load, temperature, shrinkage and creep is effectively counteracted, the bridge forming bending moment is reduced, and the real pure pressure of the large-span arch bridge is achieved.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, and more specifically to a method for adjusting the bending moment amplitude of dead load and long-term effects of long-span arch bridges based on axial compression compensation. Background Technology

[0002] For arch bridges in long-span bridges, theoretically, a zero-bending-moment state for a rigid arch structure under dead load can be achieved by adopting a reasonable arch axis. However, in reality, the arch ring will deform under dead load, overall temperature change, shrinkage and creep, and moving load, thus causing internal forces in the main arch. Dead load, overall temperature change, and shrinkage and creep all generate structural internal forces in the form of axial compressive deformation, which can be adjusted by compensating for axial compression. The structural internal forces generated by moving loads are variable, and their effects are not distributed in the same way as those generated by axial compressive deformation. Therefore, it is impossible to completely eliminate the structural internal forces generated by moving loads solely through compensation for axial compression. However, the peak bending stress at each control section of the arch rib can be equalized under a specific live load distribution pattern by adjusting the length and rotation of the arch crown closure section. Therefore, how to provide a method for adjusting the bending moment amplitude of long-span arch bridges based on axial compression compensation under dead load and long-term effects is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0003] In view of this, the present invention provides a method for adjusting the bending moment amplitude of dead load and long-term effects of a long-span arch bridge based on axial compression compensation. Based on the concept of axial compression compensation, a displacement opposite to the direction of axial compression deformation is preset during the closure stage to offset the axial compression effect caused by dead load, temperature, shrinkage and creep.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for adjusting the bending moment amplitude of dead load and long-term effects in a long-span arch bridge based on axial compression compensation includes the following steps: S1. Establish a member model of the long-span arch bridge based on the design parameters of the long-span arch bridge; S2. Calculate the internal forces in the arch ring and crown caused by dead load, shrinkage, and creep, respectively. , and ; S3. Solve for the axial compression of the arch ring caused by dead load, temperature, shrinkage, and creep respectively. , , and ; S4. Calculate the initial axial compression compensation at the closure joint. ; S5. Calculate the total internal forces of the structure under ten years of creep after applying the initial axial compression compensation at the closure joint. ; S6, Judgment and initial constant load internal forces If the ratio is less than a threshold, and if it is greater than or equal to the threshold, then the axial compression caused by creep is recalculated. Update axial compression compensation Iterate until the ratio is less than the threshold; S7, Output the final closure length compensation amount. Used to guide the construction and closure process.

[0005] Optionally, in S2, the finite element method is used to calculate the internal forces in the arch ring and crown caused by dead load, shrinkage, and creep. , and .

[0006] Optionally, solve for the axial compression of the arch ring caused by the dead load. Specifically: ; In the formula, The cross-sectional area of ​​the arch rib is... The area of ​​the vault is [area]. It is the angle between the tangent to the arch axis and the horizontal line. To design for strain, For the curvature of the vault, This is the span length.

[0007] Optionally, solve for the axial compression of the arch ring caused by temperature. Specifically: ; In the formula, This is the difference between the temperature at the time of closure and the average temperature. The coefficient of thermal expansion of the material. This is the span length.

[0008] Optionally, solve for the axial compression of the arch ring caused by shrinkage. Specifically: ; The axial compression caused by shrinkage is calculated based on the ratio of shrinkage to the bending moment of the arch rib under constant load.

[0009] Optionally, solve for the axial compression of the arch ring caused by creep. Specifically: ; The axial compression caused by creep is calculated based on the ratio of creep to the bending moment of the dead load arch rib.

[0010] Optionally, the threshold in S6 is 0.1.

[0011] As can be seen from the above technical solutions, compared with the prior art, the present invention provides a method for adjusting the bending moment amplitude of dead load and long-term effects of a long-span arch bridge based on axial compression compensation, which has the following beneficial effects: By pre-setting the compensation amount in the closure stage, the present invention can effectively offset the axial compression effect caused by dead load, temperature, shrinkage and creep, reduce the bending moment of the completed bridge by 2 to 3 orders of magnitude, realize the true pure compression state of the long-span arch bridge, and greatly improve the structural performance. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0013] Figure 1 This is a flowchart of the method for adjusting the bending moment amplitude of dead load and long-term effects on long-span arch bridges according to the present invention. Figure 2 This is a schematic diagram of the axial compression of the main arch of the long-span arch bridge of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] This invention discloses a method for adjusting the bending moment amplitude of dead load and long-term effects in a long-span arch bridge based on axial compression compensation, such as... Figure 1 As shown, it includes the following steps: S1. Establish a member model of the long-span arch bridge based on the design parameters of the long-span arch bridge; S2. Calculate the internal forces in the arch ring and crown caused by dead load, shrinkage, and creep, respectively. , and ; S3. Solve for the axial compression of the arch ring caused by dead load, temperature, shrinkage, and creep respectively. , , and ; S4. Calculate the initial axial compression compensation at the closure joint. ; S5. Calculate the total internal forces of the structure under ten years of creep after applying the initial axial compression compensation at the closure joint. ; S6, Judgment and initial constant load internal forces If the ratio is less than a threshold, and if it is greater than or equal to the threshold, then the axial compression caused by creep is recalculated. Update axial compression compensation Iterate until the ratio is less than the threshold; S7, Output the final closure length compensation amount. Used to guide the construction and closure process.

[0016] For long-span arch bridges with a reasonable arch axis, the bending moment of the arch rib caused by dead load, overall temperature change, shrinkage and creep is only generated by elastic compression. The internal forces generated by elastic compression, overall temperature change, shrinkage and creep can be eliminated by compensating for elastic compression, thereby achieving the purpose of adjusting the bending moment of the completed bridge.

[0017] Under constant load, overall temperature change, and shrinkage / creep, the elastic compression of the arch ring manifests as a shortening of the arch axis length. This deformation of the arch ring generates corresponding internal forces within the arch, resulting in maximum bending stress at the arch foot and crown. Taking a cantilevered curved beam as the basic structure, such as... Figure 2 As shown, elastic compression will shorten the arch axis in the span direction, and the amount of elastic compression can be obtained by integrating the axial compressive strain along the axis. If the length and rotation angle of the closure joint are controlled to be 0, the structure is in a stress-free closure state, and the internal forces of the structure included in the construction process are the same as those in the first scaffolding placement. If axial compression compensation is performed at the closure joint, the internal forces generated by axial compression can be eliminated, so that the bending moment after the arch is closed is zero.

[0018] The axial compressive strain of the arch satisfies ,in , , , These represent the compressive strain caused by constant load, temperature, shrinkage, and creep, respectively.

[0019] Furthermore, in S2, the finite element method is used to calculate the internal forces in the arch ring and crown caused by dead load, shrinkage, and creep. , and .

[0020] Furthermore, the axial compression of the arch ring caused by the dead load is calculated. Specifically: ; In the formula, The cross-sectional area of ​​the arch rib is... The area of ​​the vault is [area]. It is the angle between the tangent to the arch axis and the horizontal line. To design for strain, For the curvature of the vault, This is the span length.

[0021] The compressive strain induced by dead load can be expressed in different ways depending on the cross-sectional changes: ; Integrating the above equation yields the expression for constant load elastic compression.

[0022] Furthermore, the axial compression of the arch ring caused by temperature is calculated. Specifically: ; In the formula, This is the difference between the temperature at the time of closure and the average temperature. The coefficient of thermal expansion of the material. This is the span length.

[0023] In this embodiment of the invention, the compressive strain caused by shrinkage can be calculated according to Appendix C of the "Design Specification for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" (JTG 3362-2018), or it can be calculated using the finite element method.

[0024] Furthermore, the axial compression of the arch ring caused by shrinkage is calculated. Specifically: ; The axial compression caused by shrinkage is calculated based on the ratio of shrinkage to the bending moment of the arch rib under constant load.

[0025] Furthermore, the axial compression of the arch ring caused by creep is solved. Specifically: ; The axial compression caused by creep is calculated based on the ratio of creep to the bending moment of the dead load arch rib.

[0026] The compressive strain caused by creep is related to the structural stress. The axial compression compensated during the closure stage will change the structural stress and thus affect the creep process of the structure. Therefore, it is necessary to use finite element method to iterate multiple times to adjust the creep internal force.

[0027] Furthermore, the threshold in S6 is 0.1.

[0028] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0029] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for adjusting the bending moment amplitude of dead load and long-term effects in a long-span arch bridge based on axial compression compensation, characterized in that, Includes the following steps: S1. Establish a member model of the long-span arch bridge based on the design parameters of the long-span arch bridge; S2. Calculate the internal forces in the arch ring and crown caused by dead load, shrinkage, and creep, respectively. , and ; S3. Solve for the axial compression of the arch ring caused by dead load, temperature, shrinkage, and creep respectively. , , and ; S4. Calculate the initial axial compression compensation at the closure joint. ; S5. Calculate the total internal forces of the structure under ten years of creep after applying the initial axial compression compensation at the closure joint. ; S6, Judgment and initial constant load internal forces If the ratio is less than a threshold, and if it is greater than or equal to the threshold, then the axial compression caused by creep is recalculated. Update axial compression compensation Iterate until the ratio is less than the threshold; S7, Output the final closure length compensation amount. Used to guide the construction and closure process.

2. The method for adjusting the dead load and long-term effect bending moment of a long-span arch bridge based on axial compression compensation according to claim 1, characterized in that, In S2, the internal forces in the arch ring and crown caused by dead load, shrinkage, and creep are calculated using the finite element method. , and .

3. The method for adjusting the dead load and long-term effect bending moment of a long-span arch bridge based on axial compression compensation according to claim 1, characterized in that, Solve for the axial compression of the arch ring caused by dead load. Specifically: ； In the formula, The cross-sectional area of ​​the arch rib is... The area of ​​the vault is [area]. It is the angle between the tangent to the arch axis and the horizontal line. To design for strain, For the curvature of the vault, This is the span length.

4. The method for adjusting the dead load and long-term effect bending moment of a long-span arch bridge based on axial compression compensation according to claim 1, characterized in that, Solve for the axial compression of the arch ring caused by temperature. Specifically: ； In the formula, This is the difference between the temperature at the time of closure and the average temperature. The coefficient of thermal expansion of the material. This is the span length.

5. The method for adjusting the dead load and long-term effect bending moment of a long-span arch bridge based on axial compression compensation according to claim 1, characterized in that, Solve for the axial compression of the arch ring caused by shrinkage. Specifically: ； The axial compression caused by shrinkage is calculated based on the ratio of shrinkage to the bending moment of the arch rib under constant load.

6. The method for adjusting the dead load and long-term effect bending moment of a long-span arch bridge based on axial compression compensation according to claim 1, characterized in that, Solve for the axial compression of the arch ring caused by creep. Specifically: ； The axial compression caused by creep is calculated based on the ratio of creep to the bending moment of the dead load arch rib.

7. The method for adjusting the dead load and long-term effect bending moment of a long-span arch bridge based on axial compression compensation according to claim 1, characterized in that, The threshold in S6 is 0.1.

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