A large-span low-pier special-shaped continuous rigid frame bridge structure in a karst area and a design method thereof

Abstract

The present application relates to a kind of karst area large-span low pier special-shaped continuous rigid frame bridge structure, belong to bridge engineering technical field, including bridge body, the bridge body includes main beam and several bridge piers, the main beam is arched along the shape of longitudinal bridge direction, the main beam is subjected to predeformation processing, several bridge piers are sequentially arranged along longitudinal bridge direction, the upper surface of any bridge pier is integrally connected with the lower surface of main beam, the lower surface of any bridge pier is inserted into ground and is connected with rectangular cushion, the rectangular cushion is provided with several pile foundations below;Any bridge pier is gradually convergent from top to bottom along the direction perpendicular to ground, the cross-sectional shape of bridge pier along transverse bridge direction is unchanged, the present application also provides a kind of design method, including the following steps: step one: preliminary construction bridge structure simulation model;Step two: generate structure configuration design parameter Bn, foundation boundary condition design parameter kn, structure predeformation design parameter δn, step three: the parameter is substituted into simulation model, and iteration is carried out.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas and its design method. Background Technology

[0002] A continuous rigid frame bridge is a bridge structure that combines the characteristics of a T-shaped rigid frame bridge and a continuous beam bridge. In engineering practice, the piers of a continuous rigid frame bridge are often built as flexible high piers or double-limb thin-walled piers to reduce the longitudinal lateral stiffness, thereby improving the stress on the bridge and thus improving the bridge's stress conditions under adverse conditions such as changes in ambient temperature, concrete shrinkage and creep, and uneven foundation settlement.

[0003] These types of bridge piers are often quite tall. However, in actual engineering projects, limitations imposed by external conditions, such as clearance requirements for intersecting roads, predetermined road alignments, or terrain constraints, often prevent the installation of excessively tall piers. In such cases, a common solution is to use a low-pier continuous rigid frame bridge. For example, Chinese Patent CN113174827A discloses a low-pier continuous rigid frame bridge, which includes a pier body and a box girder. The pier body is composed of a pier core and irregularly shaped steel sections. The pier core is a solid pier, and the irregularly shaped steel sections are I-shaped. Inside the pier body, made of UHPC, are longitudinal reinforcement bars and stirrups that are tied together around the shaped steel section. These longitudinal reinforcement bars are connected to the shaped steel section. At least one shear key with multiple openings is vertically positioned on the upper surface of the shaped steel section. A box girder connects to the upper end of the pier body. The box girder contains tied longitudinal reinforcement bars and stirrups. One end of the shear key connects to the upper surface of the shaped steel section, and the other end extends into the box girder. Stirrups from the box girder pass through the multiple openings. This low-pier continuous rigid frame bridge features high pier flexibility and low lateral stiffness. The above-mentioned schemes only reduce the cross-sectional size of the piers by simply reducing the thrust stiffness. The methods are relatively simple and the effect of reducing the thrust stiffness is poor. Therefore, there is a need for a large-span, irregularly shaped, continuous rigid frame bridge structure with piers in karst areas that has a significant effect on reducing thrust stiffness and has a good structural optimization effect, as well as its design method. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, this invention provides a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas and its design method, which features significant reduction in lateral stiffness and good structural optimization.

[0005] The objective of this invention can be achieved through the following technical solutions: A long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in a karst area includes a bridge body, which includes a main beam and several piers. The main beam is arched in shape along the longitudinal direction of the bridge and has undergone pre-deformation treatment. Several piers are arranged sequentially along the longitudinal direction of the bridge. The upper surface of any pier is integrally connected to the lower surface of the main beam. The lower surface of any pier extends into the ground and is connected to a rectangular pier cap. Several pile foundations are arranged below the rectangular pier cap. Each of the bridge piers gradually tapers from top to bottom in a direction perpendicular to the ground, while the cross-sectional shape of the bridge pier remains unchanged in the transverse direction.

[0006] As a preferred embodiment of the present invention, each of the pile foundations is provided with a multi-layer sleeve, the multi-layer sleeve including a plurality of hollow cylindrical sleeves concentrically arranged with the corresponding pile foundation, the space between adjacent sleeves being filled with backfill material, the space between the pile foundation and the adjacent sleeve being filled with backfill material, and the space between the side of the pile foundation and the soil layer being filled with backfill soil.

[0007] As a preferred embodiment of the present invention, any of the bridge piers is provided with a hollowed-out section, the cross-sectional shape of which remains unchanged along the transverse direction of the bridge, and the hollowed-out section gradually narrows from top to bottom along the direction perpendicular to the ground.

[0008] As a preferred embodiment of the present invention, the main beam includes a top plate, a bottom plate, a web plate, and a transverse diaphragm. The transverse diaphragm is positioned such that after the main beam is connected to the pier, the transverse diaphragm is located directly above the pier.

[0009] A design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas, applicable to the aforementioned long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas, includes the following steps: Step 1: Initially construct a bridge structure simulation model; Step 2: Initially set the dimensions of each part of the bridge, generate structural design parameters Bn based on the dimensions of each part, initially set the elastic coefficient of the backfill material and the compressibility of the backfill soil for each part, generate foundation boundary condition design parameters kn based on the elastic coefficient of the backfill material and the compressibility of the backfill soil for each part, initially set the degree of pre-deformation treatment required for each part, generate structural pre-deformation design parameters δn based on the degree of pre-deformation treatment required for each part, and form the overall initial structural stiffness set and final deformation parameters, where n=1, 2...n; Step 3: Substitute the overall initial structural stiffness set and final deformation parameters into the bridge structure simulation model to simulate the structural construction process and the bridge completion process, verify the thrust stiffness, and determine whether the thrust stiffness has reached the target value. If the result is yes, proceed to step 4; otherwise, proceed to step 5. Step 4: Based on the calculated lateral stiffness, correct the dimensions of each part of the bridge, the elastic coefficient of the backfill material, the compressibility of the backfill soil, and the degree of pre-deformation treatment required for each part. Based on the corrected dimensions of each part of the bridge, regenerate the structural design parameters Bn. Based on the corrected elastic coefficient of the backfill material and the compressibility of the backfill soil, regenerate the foundation boundary condition design parameters kn. Based on the corrected degree of pre-deformation treatment required for each part, regenerate the structural pre-deformation design parameters δn. This forms the overall initial structural stiffness set and final deformation parameters. Return to Step 3. Step 5: Complete the design and generate construction drawings.

[0010] As a preferred technical solution of the present invention, step one further includes: exploring the geological conditions of the construction site, generating a geological coefficient based on the geological conditions, such that the magnitude of the geological coefficient is positively correlated with the magnitude of the settlement risk; step two further includes: generating structural design parameters Bn based on the dimensions of each part, and then correcting the structural design parameters Bn downward when the geological coefficient exceeds a threshold, and correcting the structural design parameters Bn upward when the geological coefficient is below a threshold.

[0011] As a preferred technical solution of the present invention, step one further includes: monitoring the temperature change at the construction point and generating a temperature coefficient, such that the magnitude of the temperature coefficient is positively correlated with the magnitude of the temperature difference; step two further includes: after generating the structural design parameter Bn and the foundation boundary condition design parameter kn, when the temperature coefficient exceeds the threshold, the structural design parameter Bn is corrected upward and the foundation boundary condition design parameter kn is corrected downward.

[0012] As a preferred embodiment of the present invention, step one further includes: monitoring the diurnal temperature difference and seasonal temperature difference at the construction site, generating a short-term temperature coefficient based on the diurnal temperature difference, and generating a long-term temperature coefficient based on the seasonal temperature difference, such that the magnitude of the short-term temperature coefficient is positively correlated with the magnitude of the diurnal temperature difference, and the magnitude of the long-term temperature coefficient is positively correlated with the magnitude of the seasonal temperature difference; step two further includes: after generating the structural design parameter Bn and the foundation boundary condition design parameter kn, correcting the structural design parameter Bn upward when the short-term temperature coefficient exceeds a threshold, and correcting the foundation boundary condition design parameter kn downward when the long-term temperature coefficient exceeds a threshold.

[0013] The beneficial effects of this invention are as follows: (1) By setting the piers to gradually taper from top to bottom in a direction perpendicular to the ground, while keeping the cross-sectional shape unchanged in the transverse direction, the piers form a triangular prism shape that is larger at the top and smaller at the bottom. This ensures the stability of the support while minimizing the cross-sectional dimensions of the piers in the longitudinal direction, thereby reducing the stress on other parts when deformation occurs and reducing the lateral stiffness. At the same time, by designing the main beam as a variable cross-section arch, the uniformity of the force distribution is improved in conjunction with the piers, further enhancing the structural durability of the bridge. (2) By setting the position of the transverse diaphragm of the main beam directly above the pier, the stability of the arched main beam is ensured and sufficient lateral stiffness is provided. (3) By setting the pile foundation as a multi-layer sleeve structure and selectively filling the gaps between adjacent sleeves of the pile foundation with a certain elasticity, the safety of pile foundation construction in karst areas is ensured, while the constraint effect of adjusting the pile side is achieved more precisely. (4) By excavating the pier, the longitudinal cross-sectional dimensions of the pier are further reduced, thereby reducing the stress of the pier on other parts when deformation occurs and reducing the lateral stiffness. At the same time, by setting the shape of the hollow to be larger at the top and smaller at the bottom in line with the direction of the pier, the longitudinal bearing capacity of the pier is improved, and the structural durability of the bridge is guaranteed. (5) By setting structural design parameters Bn, foundation boundary condition design parameters kn and pre-deformation design parameters δn, the adjustment of dimensions at various points during simulation design can be expressed more accurately, the constraint effect of the pile side can be adjusted, and the parameter optimization of pre-deformation of the structure can be adjusted. The initial structural stiffness set and the final deformation parameters generated by the three parameters are substituted into the simulation design for iterative calculation, which ensures the overall synergistic effect of the structural dimensions, backfill material elastic constraints and pre-deformation at various points, and optimizes the overall stress performance. (6) By generating geological coefficients and correcting structural design parameters Bn based on geological coefficients, when the geological structure is relatively unstable, the structural design parameters Bn are enlarged, forcing the operators to further reduce the structural dimensions, thereby further ensuring the reduction of the thrust stiffness. At the same time, when the geological structure is relatively stable and there is no need to consider the thrust stiffness too much, the structural design parameters are reduced, making it less likely to exceed the target value and relaxing the restrictions on the operators in the dimension design. (7) By generating a temperature coefficient, and correcting the structural design parameter Bn upward and the foundation boundary condition design parameter kn downward when the temperature coefficient exceeds the threshold, the structural design parameter Bn is enlarged when the thermal expansion and contraction effect is more obvious, forcing the operators to further correct the structural dimensions downward, while reducing the foundation boundary condition design parameter kn, so that the operators can adjust the selection range of the elastic coefficient of the backfill material within a wider range, and give fuller play to the lateral constraint effect of the backfill material. Attached Figure Description

[0014] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 This is a side perspective view of the overall structure of the present invention; Figure 2 This is a top perspective view of the overall structure of the present invention; Figure 3This is a perspective view of the bridge pier portion of the present invention from a transverse direction. Figure 4 This is a longitudinal perspective view of the bridge pier portion of the present invention; Figure 5 This is a top perspective view of the bridge pier portion of the present invention; Figure 6 This is a side perspective view of the pile foundation portion of the present invention.

[0016] Explanation of key component symbols: In the diagram: 1. Main beam; 2. Pier; 3. Pier cap; 4. Pile foundation; 5. Multi-layer sleeve; 6. Solid area of ​​pier; 7. Hollow area of ​​pier; 8. Top slab; 9. Bottom slab; 10. Diaphragm; 11. Manhole; 12. Web. Detailed Implementation

[0017] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0018] Please see Figure 1-6 A long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in a karst area includes a bridge body, which includes a main beam 1 and several piers 2. The main beam 1 is arched in shape along the longitudinal direction of the bridge and is pre-deformed. Several piers 2 are arranged sequentially along the longitudinal direction of the bridge. The upper surface of any pier 2 is integrally connected to the lower surface of the main beam 1. The lower surface of any pier 2 extends into the ground and is connected to a rectangular pier 3. Several pile foundations 4 are arranged below the rectangular pier 3. Any pier 2 gradually tapers from top to bottom along the direction perpendicular to the ground, while the cross-sectional shape of pier 2 remains unchanged along the transverse direction of the bridge. In this embodiment, the bridge is specifically designed as a three-span structure, consisting of a main span and two side spans. The main span is 155 meters long, and the side spans are 95 meters long. The main span is composed of a main beam 1, which is an arch shape that is thicker at both ends and thinner in the middle. The main beam 1 includes a top plate 8, a bottom plate 9, a web plate 12, and transverse diaphragms 10. The transverse diaphragms 10 are located on both sides of the arched main beam 1, and manholes 11 are provided on the transverse diaphragms 10. The transverse diaphragms 10 are positioned to ensure that after the main beam 1 is connected to the pier 2, the transverse diaphragms 10 are located directly above the pier 2. The arched main beam 1 adopts a single-box double-cell cross-section structure, and the beam height varies with a circular curve. For the dimensions of the main beam 1, refer to... Figures 1-2 The nominal height is denoted as H1, which is 11.5m; the box width is denoted as B1, which is 13m; the length of the cantilever on both sides is denoted as B2, which is 4m; the top surface of the box girder is provided with a unidirectional 2% cross slope; the thickness of the top plate 8 is denoted as T1, which is 0.3m; the thickness of the bottom plate 9 is denoted as T2, which is 0.32m to 1m; the thickness of the web 12 is denoted as T3, which is 0.55m to 0.85m; and the thickness of the transverse diaphragm 10 is denoted as T4, which is 0.4m. By setting the position of the transverse diaphragm 10 of the main beam 1 directly above the pier 2, the stability of the arched main beam 1 is ensured and sufficient lateral stiffness is provided. Meanwhile, there are two piers 2. The two piers 2 are located directly below the main beam 1 near both ends, that is, directly below the transverse diaphragm 10 of the main beam 1. The upper part of the pier 2 smoothly transitions to the lower surface of the main beam 1 near itself and the lower surface of the corresponding side span near itself. At this time, the main beam 1, the side span and the pier 2 form an integrated structure. The curve of the lower surface of the arched main beam 1 continues to extend, forming the shape of the pier 2 which is larger at the top and smaller at the bottom. For the dimensions of each pier 2 at various points, refer to Figures 1-2 The height of pier 2, H2, is 13.2m. The longitudinal width of the upper part of pier 2 is denoted as B3, which is 12m. The bottom width of pier 2 is denoted as B4, which is 3.5m. The height of the solid pier part above the abutment 3 is denoted as H4, which is 5m. The arched main beam 1 is made of C60 concrete, and the irregularly shaped pier 2 is made of C50 concrete. Because pier 2 has a shape that is larger at the top and smaller at the bottom, it is smaller in volume than traditional pier 2. According to the formula force = stiffness × deformation, when deformation occurs under the influence of external force, compared with bridges of general shape, under the same force, the smaller lateral stiffness can adapt to a larger displacement. By setting pier 2 to gradually taper from top to bottom in a direction perpendicular to the ground while keeping the cross-sectional shape unchanged in the transverse direction, pier 2 forms a quadrangular prism with a trapezoidal cross-section that is larger at the top and smaller at the bottom. This ensures the stability of the support while minimizing the longitudinal cross-sectional dimensions of pier 2, thereby reducing the stress on other parts when deformation occurs and reducing the lateral stiffness. At the same time, by designing the main beam 1 as a variable cross-section arch, in conjunction with pier 2, the uniformity of stress distribution is improved, further enhancing the structural durability of the bridge.

[0019] Each pile foundation 4 is provided with a multi-layer sleeve 5. The multi-layer sleeve 5 includes several hollow cylindrical sleeves that are concentrically arranged with the corresponding pile foundation 4. Backfill material is filled between adjacent sleeves, backfill material is filled between the pile foundation 4 and the adjacent sleeves, and backfill soil is filled between the side of the pile foundation 4 and the soil layer.

[0020] By setting the pile foundation 4 as a multi-layer sleeve 5 structure and selectively filling the gaps between adjacent sleeves of the pile foundation 4 with a certain degree of elasticity, the safety of pile foundation construction in karst areas is ensured, while the constraint effect of adjusting the pile side is achieved more precisely, thereby more precisely adjusting the lateral stiffness of the overall structure composed of pier 2, cap 3 and pile foundation.

[0021] Any pier 2 has a hollow section. The cross-sectional shape of the hollow section remains unchanged along the transverse direction of the bridge, and the hollow section gradually narrows from top to bottom along the direction perpendicular to the ground. Specifically, since the shape of pier 2 is wider at the top and narrower at the bottom, the hollow is also wider at the top and narrower at the bottom. Taking the longitudinal bridge direction and the surface perpendicular to the ground as the reference surface, the hollow as a whole is a hollow quadrangular prism with a trapezoidal cross section on the reference surface. The two inclined sides of the trapezoid are roughly parallel to the sides of the cross section of the pier on the reference surface. At this time, the shape of the hollow is set to be consistent with the direction of pier 2, which improves the longitudinal bearing capacity of pier 2. The hollow is not set along the transverse direction of the bridge pier 2. The two ends of the hollow are a certain distance away from the side of the bridge pier 2 in the transverse direction of the bridge. There is a partition in the middle of the hollow along the transverse direction of the bridge, which reduces the impact of the hollow on the structural strength of the bridge pier 2. At this time, the hollow in the bridge pier 2 constitutes the hollow area 7 of the bridge pier, and the rest constitutes the solid area 6 of the bridge pier. By excavating a hollowed-out section in pier 2, the longitudinal cross-sectional dimensions of pier 2 are further reduced, thereby reducing the stress on other parts when deformation occurs and lowering the lateral stiffness. At the same time, by setting the shape of the hollowed-out section to be larger at the top and smaller at the bottom, which is consistent with the orientation of pier 2, the longitudinal bearing capacity of pier 2 is improved, ensuring the structural durability of the bridge.

[0022] A design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas, applicable to the aforementioned long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas, includes the following steps: Step 1: Initially construct a bridge structure simulation model; Step 2: Initially set the dimensions of each part of the bridge, generate structural design parameters Bn based on the dimensions of each part, initially set the elastic coefficient of the backfill material and the compressibility of the backfill soil for each part, generate foundation boundary condition design parameters kn based on the elastic coefficient of the backfill material and the compressibility of the backfill soil for each part, initially set the degree of pre-deformation treatment required for each part, generate structural pre-deformation design parameters δn based on the degree of pre-deformation treatment required for each part, and form the overall initial structural stiffness set and final deformation parameters, where n=1, 2...n; Specifically, the structural design parameter Bn includes several structural design sub-parameters B, and the several Bs constitute the size parameter matrix of the bridge. For example, the workers divide the pier 2 and the main beam 1 into several parts in advance, and the size of each part is represented by a sub-parameter B. When the workers adjust the size of a certain part, B changes accordingly. The structural design parameter Bn composed of several sub-parameters B represents the size of various parts of the bridge. Similarly, the basic boundary condition design parameter kn includes several basic boundary condition design sub-parameters k. These k represent the elastic coefficient of the backfill material and the compressibility of the backfill soil in each part. When the operators need to adjust the elastic coefficient of the backfill material in a certain part or the compressibility of the backfill soil in a certain part, k will change accordingly. The structural pre-deformation design parameter δn includes several structural pre-deformation design sub-parameters δ, each sub-parameter δ representing the degree of pre-deformation applied to each part before the bridge is completed; Step 3: Substitute the overall initial structural stiffness set and final deformation parameters into the bridge structure simulation model to simulate the structural construction process and the bridge completion process, verify the thrust stiffness, check the structural stiffness distribution and internal force distribution, and determine whether it meets the verification requirements. Then, determine whether the thrust stiffness has reached the target value. If the judgment result is yes, proceed to step 4; otherwise, proceed to step 5. Step 4: Based on the calculated lateral stiffness, correct the dimensions of each part of the bridge, the elastic coefficient of the backfill material, the compressibility of the backfill soil, and the degree of pre-deformation treatment required for each part. Based on the corrected dimensions of each part of the bridge, regenerate the structural design parameters Bn. Based on the corrected elastic coefficient of the backfill material and the compressibility of the backfill soil, regenerate the foundation boundary condition design parameters kn. Based on the corrected degree of pre-deformation treatment required for each part, regenerate the structural pre-deformation design parameters δn. This forms the overall initial structural stiffness set and final deformation parameters. Return to Step 3. For example, when Bn is adjusted in a certain iteration, the overall size changes. At this time, kn and δn need to be adjusted simultaneously to complete the overall coordinated adjustment. Step 5: Complete the design and generate construction drawings.

[0023] By setting structural design parameters Bn, foundation boundary condition design parameters kn, and pre-deformation design parameters δn, the adjustment of dimensions at various points during simulation design can be expressed more accurately, the constraint effect of the pile side can be adjusted, and the parameter optimization of structural pre-deformation can be adjusted. The initial structural stiffness set and the final deformation parameters generated by the three parameters are substituted into the simulation design for iterative calculation, which ensures the overall synergistic effect of structural dimensions, elastic constraints of backfill materials, and pre-deformation at various points, and optimizes the overall stress performance. Step one also includes: exploring the geological conditions of the construction site, generating geological coefficients based on the geological conditions, so that the magnitude of the geological coefficients is positively correlated with the magnitude of the settlement risk; Step two also includes: generating structural design parameters Bn based on the dimensions of each part, and then correcting the structural design parameters Bn downward when the geological coefficients exceed the threshold, and correcting the structural design parameters Bn upward when the geological coefficients are below the threshold.

[0024] By generating geological coefficients and correcting the structural design parameter Bn based on these coefficients, the structural design parameter Bn can be enlarged when the geological structure is relatively unstable, forcing workers to further reduce the structural dimensions and thus further ensure the reduction of lateral stiffness. At the same time, when the geological structure is relatively stable and there is no need to consider lateral stiffness too much, the structural design parameter can be reduced, making it less likely to exceed the target value and relaxing the restrictions on workers in dimension design.

[0025] Step one also includes: monitoring temperature changes at the construction site and generating a temperature coefficient, such that the magnitude of the temperature coefficient is positively correlated with the magnitude of the temperature difference; Step two also includes: after generating the structural design parameter Bn and the foundation boundary condition design parameter kn, when the temperature coefficient exceeds the threshold, the structural design parameter Bn is corrected upward and the foundation boundary condition design parameter kn is corrected downward.

[0026] Step one also includes: monitoring the diurnal temperature range and seasonal temperature range at the construction site, generating a short-term temperature coefficient based on the diurnal temperature range, and generating a long-term temperature coefficient based on the seasonal temperature range, so that the magnitude of the short-term temperature coefficient is positively correlated with the magnitude of the diurnal temperature range, and the magnitude of the long-term temperature coefficient is positively correlated with the magnitude of the seasonal temperature range; Step two also includes: after generating the structural design parameter Bn and the foundation boundary condition design parameter kn, adjusting the structural design parameter Bn upward when the short-term temperature coefficient exceeds the threshold, and adjusting the foundation boundary condition design parameter kn downward when the long-term temperature coefficient exceeds the threshold.

[0027] By generating a temperature coefficient and correcting the structural design parameter Bn upwards and the foundation boundary condition design parameter kn downwards when the temperature coefficient exceeds a threshold, the structural design parameter Bn is amplified when the thermal expansion and contraction effect is significant. This forces the workers to further correct the structural dimensions downwards, while simultaneously reducing the foundation boundary condition design parameter kn. This allows the workers to adjust the selection range of the elastic coefficient of the backfill material within a wider range, thus more fully utilizing the lateral constraint effect of the backfill material.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas, characterized in that: The karst area long-span low-pier irregular continuous rigid frame bridge structure includes a bridge body, which includes a main beam and several piers. The main beam is arched in shape along the longitudinal direction of the bridge and has undergone pre-deformation treatment. Several piers are arranged sequentially along the longitudinal direction of the bridge. Each pier is formed by the main beam contracting from top to bottom. The lower surface of each pier extends into the ground and is connected to a rectangular pier. Several pile foundations are arranged below the rectangular pier. Each of the bridge piers gradually tapers from top to bottom in a direction perpendicular to the ground, while the cross-sectional shape of the bridge pier remains unchanged in the transverse direction. All of the pile foundations are provided with multi-layer sleeves, the multi-layer sleeves including a number of hollow cylindrical sleeves concentrically arranged with the corresponding pile foundations, the space between adjacent sleeves is filled with backfill material, the space between the pile foundation and the adjacent sleeves is filled with backfill material, and the space between the side of the pile foundation and the soil layer is filled with backfill soil. The longitudinal dimension of the upper surface of the bridge pier is denoted as B3, the longitudinal dimension of the lower surface is denoted as B4, and the height is denoted as H2. The ratio of B3 to B4 is 3~5:1, and the ratio of H2 to B4 is 3~4:

1. The method, applicable to the aforementioned long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas, further includes the following steps: Step 1: Initially construct a bridge structure simulation model; Step 2: Initially set the dimensions of each part of the bridge, generate structural design parameters Bn based on the dimensions of each part, initially set the elastic coefficient of the backfill material and the compressibility of the backfill soil for each part, generate foundation boundary condition design parameters kn based on the elastic coefficient of the backfill material and the compressibility of the backfill soil for each part, initially set the degree of pre-deformation treatment required for each part, generate structural pre-deformation design parameters δn based on the degree of pre-deformation treatment required for each part, and form the overall initial structural stiffness set and final deformation parameters, where n=1, 2...; Step 3: Substitute the overall initial structural stiffness set and final deformation parameters into the bridge structure simulation model to simulate the structural construction process and the bridge completion process, verify the thrust stiffness, check the structural stiffness distribution and internal force distribution, and determine whether it meets the verification requirements. Then, determine whether the thrust stiffness has reached the target value. If the judgment result is yes, proceed to step 4; otherwise, proceed to step 5. Step 4: Based on the calculated lateral stiffness, correct the dimensions of each part of the bridge, the elastic coefficient of the backfill material, the compressibility of the backfill soil, and the degree of pre-deformation treatment required for each part. Based on the corrected dimensions of each part of the bridge, regenerate the structural design parameters Bn. Based on the corrected elastic coefficient of the backfill material and the compressibility of the backfill soil, regenerate the foundation boundary condition design parameters kn. Based on the corrected degree of pre-deformation treatment required for each part, regenerate the structural pre-deformation design parameters δn. This forms the overall initial structural stiffness set and final deformation parameters. Return to Step 3. Step 5: Complete the design and generate construction drawings.

2. The design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in a karst area according to claim 1, characterized in that: Each of the bridge piers has a hollow section, the cross-sectional shape of which remains unchanged along the transverse direction of the bridge, and the hollow section gradually narrows from top to bottom along the direction perpendicular to the ground.

3. The design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in a karst area according to claim 1, characterized in that: The main beam includes a diaphragm, and the diaphragm is positioned such that it is directly above the pier after the main beam is connected to the pier.

4. The design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in karst areas according to claim 1, characterized in that: Step one also includes: exploring the geological conditions of the construction site, generating geological coefficients based on the geological conditions, so that the magnitude of the geological coefficients is positively correlated with the magnitude of the settlement risk; Step two also includes: generating structural design parameters Bn based on the dimensions of each part, and when the geological coefficients exceed the threshold, correcting the structural design parameters Bn downwards, and when the geological coefficients are below the thresholds, correcting the structural design parameters Bn upwards.

5. The design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in a karst area according to claim 4, characterized in that: Step one also includes: monitoring temperature changes at the construction site and generating a temperature coefficient, such that the magnitude of the temperature coefficient is positively correlated with the magnitude of the temperature difference; Step two also includes: after generating structural design parameters Bn and foundation boundary condition design parameters kn, when the temperature coefficient exceeds the threshold, the structural design parameters Bn are corrected upward and the foundation boundary condition design parameters kn are corrected downward.

6. The design method for a long-span, low-pier, irregularly shaped continuous rigid frame bridge structure in a karst area according to claim 5, characterized in that: Step one further includes: monitoring the diurnal temperature range and seasonal temperature range at the construction site, generating a short-term temperature coefficient based on the diurnal temperature range, and generating a long-term temperature coefficient based on the seasonal temperature range, so that the magnitude of the short-term temperature coefficient is positively correlated with the magnitude of the diurnal temperature range, and the magnitude of the long-term temperature coefficient is positively correlated with the magnitude of the seasonal temperature range; Step two further includes: after generating the structural design parameter Bn and the foundation boundary condition design parameter kn, correcting the structural design parameter Bn upward when the short-term temperature coefficient exceeds the threshold, and correcting the foundation boundary condition design parameter kn downward when the long-term temperature coefficient exceeds the threshold.

Images