F-beam structure and design method thereof

Abstract

The invention relates to the technical field of sea-crossing bridge construction, in particular to an F-beam structure and a design method thereof. Wherein the F-beam structure comprises a block A, a block B and a block C which are arranged in sequence; the block A comprises a first vertical wall, and a first bottom beam is arranged at the bottom; the block B comprises a second vertical wall, and a second bottom beam is arranged at the bottom; the C block comprises a third vertical wall, a third bottom beam is arranged at the bottom of the C block, a C block bottom plate is arranged on the side, close to the second bottom beam, of the third bottom beam, cantilever beams are arranged on the side, away from the second bottom beam, of the third bottom beam, the cantilever beams are arranged at intervals in the length direction of the C block, and the cantilever ends of the adjacent cantilever beams are connected through edge beams; wherein a first wet joint is arranged between the first bottom beam and the second bottom beam, and a second wet joint is arranged between the second bottom beam and the C-block bottom plate. According to the F beam structure, the F beam is divided into a plurality of blocks, the whole is broken up into parts, the weight of a single block is remarkably reduced, and the problem that construction of the F beam integrally formed through pouring is limited in a shallow water area is solved.

Description

Technical Field

[0001] This invention relates to the field of cross-sea bridge construction technology, and in particular to an F-beam structure and its design method. Background Technology

[0002] Currently, the structural design of cross-sea bridges typically prioritizes bearing the load of the roadway, while functional areas such as sidewalks, utility tunnels, and green spaces are often treated as ancillary structures, installed after the main beam construction is completed. This phased and separate construction model not only affects overall construction efficiency but also poses significant environmental risks when constructing in environmentally sensitive areas. Especially when crossing nearshore or shallow waters (such as ecologically fragile areas like mangroves and coral reefs), structural detachment or debris falling during the construction of ancillary structures could cause irreversible damage to the fragile marine ecosystem.

[0003] To address these issues, existing technologies have developed irregularly shaped beam structures that integrate utility tunnels, sidewalks, and green areas with the main beam. However, these integrally cast irregularly shaped beams are quite heavy (generally exceeding 400 tons), requiring large lifting equipment for installation during cross-sea bridge construction. If the bridge site is located in shallow water (e.g., water depth no greater than 2.5 meters), conventional large crane vessels cannot access the area, limiting the construction of these integrally cast irregularly shaped beams in shallow water. Summary of the Invention

[0004] The purpose of this invention is to overcome the limitations of existing large irregular beams that are integrally cast and molded in shallow water areas, and to provide an F-beam structure and its design method.

[0005] In a first aspect, the present invention provides an F-beam structure comprising blocks A, B, and C arranged sequentially; Block A includes a first vertical wall, and a first bottom beam is provided at the bottom of the first vertical wall; Block B includes a second vertical wall, and a second bottom beam is provided at the bottom of the second vertical wall; The C block includes a third vertical wall, a third bottom beam at the bottom of the third vertical wall, a C block base plate on the side of the third bottom beam close to the second bottom beam, and a cantilever beam on the side of the third bottom beam away from the second bottom beam. The cantilever beams are spaced apart along the length of the C block, and the cantilever ends of adjacent cantilever beams are connected by side beams. The first wet joint is between the first bottom beam and the second bottom beam, and the second wet joint is between the second bottom beam and the C-block bottom plate.

[0006] The F-beam structure provided by this invention decomposes the F-beam into blocks A, B, and C, achieving the goal of breaking down the whole into parts. The weight of each block is significantly reduced, allowing smaller lifting equipment or land-based machinery to complete the installation. This solves the problem of construction limitations in shallow water areas for integrally cast F-beams.

[0007] During construction, blocks A, B, and C can be prefabricated at the beam fabrication yard and then directly assembled on-site. A green area can be formed between blocks A and B, and a utility tunnel area can be formed between blocks B and C. The cantilever beams support pedestrian walkways. The cantilever beams and edge beams are integrated with block C during the prefabrication stage, requiring only wet joint treatment on-site. This avoids the risk of soil and debris falling from the installation of numerous loose components at height, as is common in traditional solutions, and greatly protects ecologically fragile areas such as mangroves and coral reefs.

[0008] By setting up a first wet joint and a second wet joint, the F-beam structure rationally distributes the internal stress during the construction stage through the wet joints. It is especially suitable for asymmetrical structures like the F-beam caused by a single-sided cantilever, and effectively controls the deformation and cracking of precast components during transportation and installation.

[0009] Preferably, the width of the first wet joint is 1300mm ± 20mm, and the width of the second wet joint is 500mm ± 20mm.

[0010] The inclusion of a first and second wet joint significantly reduces the cross-sectional area of ​​blocks A, B, and C, thereby keeping the weight of individual precast components within the rated load. Preferably, the width of the second wet joint is 500mm ± 20mm, and a certain width of the bottom plate of block C is retained. This partially offsets the eccentric moment generated by the cantilever beam and side beam on the other side, making it easier for the lifting hook to find a balanced position during hoisting and ensuring that block C remains horizontally stable during lifting.

[0011] In a second aspect, the present invention provides a design method for an F-beam structure, for designing the aforementioned F-beam structure, comprising the following steps: S1. Divide the construction into stages, obtain the three-dimensional geometric parameters and material properties of beam F, and preliminarily determine the layout scheme of beam F; Perform eccentricity parameter calculation: calculate the eccentricity between the centroid and the mass center of beam F caused by the single-sided cantilever beam and the edge beam, and determine the initial eccentric moment; S2. Establish finite element models for blocks A, B, and C respectively. Configure the finite element models to simulate the overall stress based on the construction sequence of the first wet joint and the second wet joint. S3. Based on the finite element model established in S2, simulate the tensioning of prestressed tendons with positive bending moment in blocks A, B, and C, the pouring of the first and second wet joints, and the tensioning of negative bending moment after system transformation. Perform finite element calculations to calculate the effect of the reverse moment generated by prestressing at each construction stage on the cancellation effect of the initial eccentric moment calculated in S1. S4. Based on the calculation results of S3, adjust the distribution of prestressing tendons in beam F, and repeat S3 until the prestress of beam F meets the set threshold, thus completing the design of beam F.

[0012] Because the irregularly shaped F-beams are designed in sections, the resulting asymmetrical structure makes the prestressed beam arrangement design challenging. Traditional symmetrical arrangement methods struggle to meet load-bearing requirements, easily leading to uneven local stress distribution and concrete cracking, thus affecting the structure's load-bearing capacity and durability. The design method for F-beam structures provided by this invention first calculates eccentricity parameters, quantitatively obtaining the eccentricity between the centroid and centroid of the cross-section caused by the single-sided cantilever beams and edge beams, as well as the initial eccentric moment. This provides a precise mechanical benchmark for this asymmetrical F-beam structure. By establishing a finite element model and simulating the overall stress according to the construction sequence of the first and second wet joints between blocks A, B, and C, the complex evolution of stress distribution in each construction stage (such as block prefabrication, wet joint pouring between blocks A, B, and C, and bridge operation) can be dynamically captured. By simulating prestressed tensioning and evaluating the effect of the resulting reverse moment on offsetting the initial eccentric moment, the mechanical equilibrium of the F-beam was achieved. This fundamentally solved the risk of rollover and cracking caused by the inherent eccentricity of the irregular F-beam, realizing the breakdown of the F-beam into smaller parts, significantly reducing the tonnage of a single hoisting operation to adapt to shallow water construction, and greatly improving the load-bearing capacity, construction accuracy, and life-cycle durability of the irregular bridge structure while protecting the marine ecological environment.

[0013] Preferably, in S1, the construction phase is divided into three stages: F-beam prefabrication, F-beam installation, and F-beam operation.

[0014] By dividing the construction phase into three key stages—F-beam prefabrication, F-beam installation, and F-beam operation—the finite element model is provided with boundary conditions and load histories that conform to the actual engineering logic, ensuring the integrity of the mechanical analysis.

[0015] Preferably, in S1, the preliminary determination of the arrangement scheme of beam F includes the following steps: A preliminary plan for the arrangement of prestressing tendons in beam F is proposed, with the prestressing tendons arranged symmetrically and tensioned symmetrically; preliminary plans for the pouring of the first and second wet joints and the pier-beam consolidation scheme are also proposed.

[0016] In the design of complex irregular F-beams, simulation using a traditional symmetrical scheme can quickly and intuitively expose the unbalanced bending moment and torque deviation caused by the cantilever structure, avoiding the blindness of directly carrying out asymmetrical design.

[0017] Preferably, in S2, finite element models corresponding to blocks A, B, and C are established respectively, including the following steps: A hybrid mesh combining structured and unstructured meshes is used for the finite element basis meshing. Blocks A and B are meshed using structured meshes, while block C is meshed using unstructured meshes.

[0018] Because blocks A and B have relatively regular structures, using a structured mesh can achieve high computational convergence and data regularity with fewer computational degrees of freedom, ensuring the analysis efficiency of the main stress-bearing parts. Block C, however, contains a complex structure including a base plate, a single-sided cantilever beam, and edge beams. Its irregular geometry and complex stress transition zones necessitate the use of a more adaptable unstructured mesh, which can accurately capture the geometric details at the cantilever root and edge beam connections, avoiding distortions caused by regular meshes at irregular edges. This hybrid meshing method not only significantly improves the simulation accuracy of stress gradients in the eccentrically loaded region of beam F, but also shortens the iteration time of large-scale three-dimensional finite element models and improves computational efficiency by reducing redundant calculations in regular parts.

[0019] Preferably, in S2, finite element models corresponding to blocks A, B, and C are established respectively, including the following steps: The three-dimensional geometric parameters of beam F obtained from S1 are input into the three-dimensional modeling tool to construct the three-dimensional geometric model of beam F; the three-dimensional geometric parameters of beam F include the shape of blocks A, B, and C, the arrangement of prestressing tendons, and the relationship of support positions; Based on the material properties of beam F obtained from S1, determine the mechanical property parameters of blocks A, B, and C, and set the mechanical properties of blocks A, B, and C, including elastic modulus, Poisson's ratio, density, tensile strength, and compressive strength. The beam and slab elements of each structure of beam F are set up to determine the specific structural state of each structure in different construction stages. Activation / passivation elements of blocks A, B, and C are set up respectively. According to the construction progress and predetermined construction nodes, the corresponding elements are activated or passed through in each construction stage to determine the specific structural state of each structure in different construction stages. Based on the specific structural state of each structure in different construction stages, the mechanical behavior of beam F in each construction stage is simulated to realize the simulation of the construction sequence according to the first wet joint and the second wet joint.

[0020] The design method for F-beam structures provided by this invention, through setting beam and plate elements and using an "activation / passivation" method, can precisely simulate the unique "time-varying mechanical" characteristics of F-beams. Specifically, based on the actual construction sequence of the first and second wet joints, the model dynamically presents the entire process of the components transitioning from independent operation to shared stress after the wet joints are consolidated. This method accurately captures changes in secondary internal forces and stress distribution caused by eccentric structures, thus avoiding calculation errors caused by simplified construction processes in traditional designs. It ensures that the mechanical response of the F-beam at each construction stage is within a controlled range in complex construction environments in shallow sea areas, greatly improving the overall safety and design accuracy of the irregularly shaped modular structure combination.

[0021] Preferably, in S2, the finite element models corresponding to blocks A, B, and C are established respectively, and the following steps are also included: Based on the mechanical behavior of the F-beam at each construction stage and the actual construction conditions, the location of the support points, the type of support, and the support reaction force are set, and the constraint conditions of the support are determined. At each construction stage, loads are applied to beam F according to the construction process to simulate the stress state of beam F under different construction stages. The load application method for each construction stage is determined based on the actual construction situation, and the load changes over time are modeled.

[0022] By precisely setting the location of support points and the type of constraints based on the mechanical behavior of each construction stage, the stress boundary of the F-beam can be accurately reproduced under different working conditions, such as precast platform support, temporary hoisting supports, and final pier-beam consolidation. By modeling the load changes over time, the cumulative effect and evolution trend of stress in the F-beam during construction can be reflected more accurately.

[0023] Preferably, S3 further includes: real-time monitoring of the vertical displacement of the side beam and the deflection angle of the cross section of the F beam.

[0024] By monitoring the vertical displacement of the side beam and the deflection angle of the beam section in real time during the simulation, when the deflection angle exceeds the limit, the designer can adjust the prestress offset accordingly to ensure that the side beam and the cantilever end do not crack due to excessive deflection, while ensuring that the main beam section does not become unstable and overturned due to eccentric torque.

[0025] Preferably, in S4, adjusting the distribution of prestressing tendons in beam F includes the following steps: determining the number and layout of prestressing tendons based on the calculation results of S3, increasing the number of prestressing tendons in the stress concentration areas of blocks A, B, and C, and not setting prestressing tendons in cantilever beams and edge beams.

[0026] Based on the calculation results of S3, increasing the number of prestressing tendons in the stress concentration areas of blocks A, B, and C (especially at the connection between the vertical wall and the bottom beam) can effectively offset the tensile stress generated by the eccentric self-weight, significantly improving the crack resistance and safety reserve of the structure. Since the cantilever beam only bears pedestrian loads and is arranged at intervals, not setting prestressing tendons can reduce the structural self-weight at the cantilever end and improve the overall balance of beam F.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The F-beam structure provided by this invention decomposes the F-beam into blocks A, B, and C, realizing the transformation from whole to part. The weight of each block is significantly reduced, allowing smaller lifting equipment or land-based machinery to complete the installation. This solves the problem of construction limitations of integrally cast F-beams in shallow water areas.

[0028] 2. This invention provides a design method for an F-beam structure. By simulating prestressed tension and evaluating the effect of the generated reverse moment on the initial eccentric moment, the mechanical equilibrium of the F-beam is achieved. This fundamentally solves the risk of rollover and cracking caused by the inherent eccentricity of irregular F-beams, enabling the F-beam to be broken down into smaller parts. This significantly reduces the tonnage of a single hoisting operation, making it suitable for construction in shallow water areas. While protecting the marine ecological environment, it greatly improves the load-bearing capacity, construction accuracy, and overall durability of irregular bridge structures. Attached Figure Description

[0029] Figure 1 Elevation view of beam F; Figure 2 This is a top view of beam F; Figure 3 This is a schematic diagram of the prestressing tendon arrangement for beam F.

[0030] Marked in the image: 1-Block A, 11-First vertical wall, 12-First bottom beam, 2-Block B, 21-Second vertical wall, 22-Second bottom beam, 3-Block C, 31-Third vertical wall, 32-Third bottom beam, 33-Block C base plate, 34-Cantilever beam, 35-Edge beam, 100-First wet joint, 200-Second wet joint. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0032] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0033] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0034] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0035] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0036] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0037] Example 1 like Figure 1 , Figure 2 As shown, this embodiment provides an F-beam structure, including blocks A1, B2, and C3 arranged sequentially. Specifically, during the construction of the cross-sea bridge, block A1 is close to the central axis of the bridge, block C3 is arranged on the outer side, and block B2 is located between block A1 and block C3.

[0038] Block A1 includes a first vertical wall 11, and a first bottom beam 12 is provided at the bottom of the first vertical wall 11. Specifically, for example... Figure 1 The portion below the dotted line at the bottom of the first vertical wall 11 can be divided into the first bottom beam 12. It can be understood that the first bottom beam 12 and the first vertical wall 11 are only functional area divisions based on spatial location. In actual molding, the two can be integrally cast to form an integrated structure.

[0039] Block B2 includes a second vertical wall 21, and a second bottom beam 22 is provided at the bottom of the second vertical wall 21; Block C3 includes a third vertical wall 31, and a third bottom beam 32 is provided at the bottom of the third vertical wall 31. The third bottom beam 32 is located on the side close to the second bottom beam 22 (for example...). Figure 1 A C-block bottom plate 33 is provided on the left side of the third bottom beam 32. The side of the third bottom beam 32 away from the second bottom beam 22 (e.g.) Figure 1 A cantilever beam 34 is provided on the right side of the third bottom beam 32. For example... Figure 2 As shown, cantilever beams 34 are spaced apart along the length of block C3, and the cantilever ends of adjacent cantilever beams 34 are connected by side beams 35. In actual molding, the side beams 35 and the spaced-apart cantilever beams 34 can be integrally cast; as shown... Figure 2 As shown, from a top-down view, the continuous edge beams 35 connect the ends of the originally discrete cantilever beams 34 into a whole, thereby enhancing the rigidity of the sidewalk area.

[0040] The first wet joint 100 is located between the first bottom beam 12 and the second bottom beam 22, and the second wet joint 200 is located between the second bottom beam 22 and the bottom plate 33 of block C. In this embodiment, the width of the first wet joint 100 is 1300mm ± 20mm, and the width of the second wet joint 200 is 500mm ± 20mm. The arrangement of the first wet joint 100 and the second wet joint 200 significantly reduces the cross-sectional area of ​​blocks A, B, and C, thereby keeping the weight of a single prefabricated component within the rated load. Preferably, the width of the second wet joint 200 is 500mm ± 20mm, and a certain width of bottom plate 33 of block C is retained, which can partially offset the eccentric moment generated by the cantilever beam 34 and the side beam 35 on the other side, making it easier for the hook to find the balance position during hoisting and ensuring that block C remains horizontally stable during hoisting.

[0041] The F-beam structure provided in this embodiment decomposes the F-beam into block A1, block B2, and block C3, realizing the reduction of the whole into parts. The weight of each block is significantly reduced, allowing smaller lifting equipment or land-based machinery to complete the installation. This solves the problem of construction restrictions in shallow water areas for integrally cast F-beams.

[0042] During construction, blocks A1, B2, and C3 can be prefabricated at the beam fabrication yard and then directly assembled on the construction site, such as... Figure 1 As shown, a green area can be formed between Block A1 and Block B2, and a utility tunnel area can be formed between Block B2 and Block C3. The cantilever beam 34 is used to support the pedestrian walkway. The cantilever beam 34 and the edge beam 35 have been integrated with Block C3 during the prefabrication stage. On-site, only wet joint treatment is required, which avoids the risk of soil falling due to the installation of a large number of loose components at high altitudes in traditional solutions, and greatly protects ecologically fragile areas such as mangroves and coral reefs.

[0043] By setting the first wet joint 100 and the second wet joint 200, the F-beam structure rationally distributes the internal stress during the construction stage through the wet joints. It is especially suitable for asymmetrical structures such as F-beams caused by single-sided cantilever, and effectively controls the deformation and cracking of prefabricated components during transportation and installation.

[0044] Example 2 This embodiment provides a design method for an F-beam structure, mainly used for designing the F-beam structure provided in Embodiment 1, including the following steps: S1. Divide the construction into stages, obtain the three-dimensional geometric parameters and material properties of beam F, and preliminarily determine the layout scheme of beam F; Specifically, in this embodiment, the construction stage can be divided into three stages: F-beam prefabrication, F-beam installation, and F-beam operation. This provides the subsequent finite element model with boundary conditions and load histories that conform to the actual engineering logic, enabling the constructed finite element model to simulate the construction stress conditions of the entire process of F-beam prefabrication, installation, and operation, thus ensuring the integrity of the mechanical analysis.

[0045] In this embodiment, the obtained three-dimensional geometric parameters of beam F can specifically be parameters required for subsequent modeling, such as: detailed dimensions such as the length, width, and height of blocks A1, B2, and C3, with a focus on the extension length and width of cantilever beam 34, the longitudinal spacing (step distance) of cantilever beam 34, the cross-sectional dimensions of edge beam 35, the width of the first wet joint 100 and the second wet joint 100, the position and size of the support, and the initially planned path of the prestressing tendons. The material properties of beam F can include: elastic modulus, Poisson's ratio, density, strength parameters, time-varying characteristic parameters, etc.

[0046] In this embodiment, the preliminary arrangement scheme of beam F is determined, which may include the following steps: a preliminary arrangement scheme of prestressing tendons for beam F is proposed, wherein the prestressing tendons of beam F are arranged symmetrically and tensioned symmetrically; a preliminary casting scheme for the first wet joint 100 and the second wet joint 200, and a pier-beam consolidation scheme are proposed.

[0047] In the design of complex irregular F-beams, simulation using a traditional symmetrical scheme can quickly and intuitively expose the unbalanced bending moment and torque deviation caused by the cantilever structure, avoiding the blindness of directly carrying out asymmetrical design.

[0048] Perform eccentricity parameter calculation: calculate the eccentricity between the centroid and the mass center of beam F caused by the single-sided cantilever beam 34 and the edge beam 35, and determine the initial eccentricity moment.

[0049] It can be understood that the initial eccentric moment can be determined using calculation methods commonly used in industrial production in this embodiment. For example, it can be: First, based on the cross-sectional design drawing of beam F, establish a two-dimensional rectangular coordinate system (or establish a three-dimensional coordinate system in the spatial model) and extract the geometric dimensions and density attributes of blocks A1, B2, and C3; Second, use the integral method or area-weighted average method to calculate the position y of the centroid of the entire cross-section of beam F. g Subsequently, the position of the centroid y is determined. g With the center line y of the support s By comparison, the lateral eccentricity e = |y g -y s Finally, combining the structure's self-weight and gravitational acceleration, the initial torque caused by the structure's self-weight is obtained, which is the initial eccentric moment M. e .

[0050] S2. Establish finite element models for blocks A1, B2, and C3 respectively. Configure the finite element models to simulate the overall stress according to the construction sequence of the first wet joint 100 and the second wet joint 200.

[0051] Furthermore, in this embodiment, a hybrid mesh combining structured and unstructured meshes is used for the finite element basis meshing, wherein block A1 and block B2 are meshed using structured meshes, and block C3 is meshed using unstructured meshes.

[0052] like Figure 1As shown, since blocks A1 and B2 have relatively regular structures, using a structured mesh can achieve high computational convergence and data regularity with fewer computational degrees of freedom, ensuring the analysis efficiency of the main stress-bearing parts. Block C3, however, contains a complex structure including the C-block base plate 33, a single-sided cantilever beam 34, and an edge beam 35. Its geometry is irregular and contains complex stress transition zones. Using a more adaptable unstructured mesh can accurately capture the geometric details at the cantilever root and the connection of the edge beam 35, avoiding distortions caused by regular meshes at irregular edges. This hybrid mesh generation method not only significantly improves the simulation accuracy of the stress gradient in the eccentrically loaded region of beam F, but also shortens the iteration time of large-scale three-dimensional finite element models and improves computational efficiency by reducing redundant calculations in regular parts.

[0053] Specifically, in this embodiment, finite element models corresponding to block A1, block B2, and block C3 are established respectively, including the following steps: The three-dimensional geometric parameters of beam F obtained from S1 are input into a three-dimensional modeling tool (specifically, it can be finite element analysis software commonly used in industrial production, such as Midas Civil or Midas FEA) to construct a three-dimensional geometric model of beam F; the three-dimensional geometric parameters of beam F include the shape of block A1, block B2, and block C3, the arrangement of prestressing tendons, and the relationship of support positions. Based on the material properties of beam F obtained from S1, determine the mechanical property parameters of blocks A1, B2, and C3, and set the mechanical properties of blocks A1, B2, and C3, including elastic modulus, Poisson's ratio, density, tensile strength, and compressive strength. The beam and slab elements of each structure of the F beam are set up to determine the specific structural state of each structure in different construction stages. Activation / passivation elements of block A1, block B2, and block C3 are set up respectively. In each construction stage, the corresponding elements are activated or passedivated according to the construction progress and predetermined construction nodes to determine the specific structural state of each structure in different construction stages. Based on the specific structural state of each structure in different construction stages, the mechanical behavior of the F beam in each construction stage is simulated to realize the construction sequence simulation based on the first wet joint 100 and the second wet joint 200.

[0054] By setting up beam and slab elements and using the "activation / passivation" method, the unique "time-varying mechanical" characteristics of the F-beam can be simulated in a refined manner. This means that, based on the actual construction sequence of the first wet joint 100 and the second wet joint 200, the entire process of the component's transformation from independent operation to joint stress after the wet joints are consolidated can be dynamically presented in the model. This accurately captures the changes in secondary internal forces and the stress distribution caused by the eccentric structure, thus avoiding calculation errors caused by simplifying the construction process in traditional designs. This ensures that the mechanical response of the F-beam at each construction stage is within a controlled range in the complex construction environment of shallow water areas across the sea, improving the overall safety and design accuracy of the modular F-beam structure.

[0055] Furthermore, in this embodiment, based on the mechanical behavior of the F-beam at each construction stage and the actual construction conditions, the location of the support points, the support type, and the support reaction force are set, and the constraint conditions of the supports are determined. At each construction stage, loads are applied to the F-beam according to the construction process to simulate the stress state of the F-beam under different construction stages. The load application method for each construction stage is determined based on the actual construction conditions, and the load variation over time is modeled. This setup allows for precise setting of the support point location and constraint type based on the mechanical behavior of each construction stage, realistically reproducing the stress boundaries of the F-beam under different working conditions such as precast platform support, temporary hoisting supports, and final pier-beam consolidation. By modeling the load variation over time, the cumulative effect and evolution trend of stress in the F-beam during construction can be more accurately reflected.

[0056] S3. Based on the finite element model established in S2, simulate the positive bending moment prestressing tendon tensioning in blocks A1, B2, and C3, the pouring of the first wet joint 100 and the second wet joint 200, and the negative bending moment tensioning process after system transformation. Perform finite element calculations to calculate the effect of the reverse moment generated by prestressing at each construction stage on the cancellation effect of the initial eccentric moment calculated in S1. Specifically, finite element analysis software can be used to extract the equivalent radial force generated by the asymmetrically arranged prestressing tendons on the F beam body at each construction stage; calculate the resultant moment M of this equivalent radial force about the rotation center of the support. p M p The initial eccentric moment M obtained in S1 e By performing vector superposition, the residual torque M at each stage is obtained. r This allows us to determine the effectiveness of the counteracting moment generated by prestressing at each construction stage in counteracting the initial eccentric moment. It can be understood that the aforementioned system transformation refers to the change in the mechanical behavior of beam F from a longitudinal bridge to a simply supported state and then to a longitudinal bridge to a continuous state.

[0057] S3 also includes: real-time monitoring of the vertical displacement of the edge beam 35 and the deflection angle of the F beam section. By monitoring the vertical displacement of the edge beam 35 and the deflection angle of the beam section in real time during the simulation, when the deflection angle exceeds the limit, the designer can adjust the prestressing offset accordingly to ensure that the edge beam 35 and the cantilever end do not crack due to excessive deflection, while ensuring that the main beam section does not become unstable and overturned due to eccentric torque.

[0058] S4. Based on the calculation results of S3, analyze the stress distribution pattern within the prestressed beam F after prestressing. Considering the structural layout, load requirements, and construction stage of the beam F, adjust the distribution of the prestressing tendons to achieve an asymmetrical prestressed arrangement. If the design requirements are not met, repeat S3 until the prestressing of the beam F meets the set threshold. Figure 3 The design of beam F is shown in the figure.

[0059] Specifically, based on the calculation results of S3, the number and layout of prestressing tendons can be adjusted. The number of prestressing tendons can be increased in the stress concentration areas of blocks A1, B2, and C3, while no prestressing tendons are installed at cantilever beam 34 and edge beam 35. By increasing the number of prestressing tendons in the stress concentration areas of blocks A1, B2, and C3 (especially at the connection between the vertical wall and the bottom beam), the tensile stress generated by the eccentric self-weight can be effectively offset, significantly improving the structure's crack resistance and safety reserve. Since cantilever beam 34 only bears pedestrian loads and is spaced out, omitting prestressing tendons reduces the structural self-weight at the cantilever end, improving the overall balance of beam F.

[0060] Because the irregularly shaped F-beam is designed in sections, the resulting asymmetrical structure makes the prestressing arrangement design challenging. Traditional symmetrical arrangement methods are insufficient to meet stress requirements, easily leading to uneven local stress and concrete cracking, affecting structural bearing capacity and durability. The design method for the F-beam structure provided in this embodiment first calculates eccentricity parameters, quantitatively obtaining the eccentricity between the centroid and centroid of the cross-section caused by the single-sided cantilever beam 34 and the edge beam 35, as well as the initial eccentric moment, providing a precise mechanical benchmark for this asymmetrical F-beam structure. A finite element model is established, and overall stress simulation is performed based on the construction sequence of the first wet joint 100 and the second wet joint 200 between blocks A1, B2, and C3. This dynamically captures the complex evolution of stress distribution in various construction stages (e.g., prefabrication in sections, pouring of wet joints between blocks A1, B2, and C3, and bridge operation). By simulating prestressing tension and evaluating the counteracting effect of the generated reverse moment on the initial eccentric moment, the mechanical equilibrium of the F-beam is achieved. This fundamentally solves the risk of rollover and cracking caused by the inherent eccentricity of irregular F-beams, and realizes the breakdown of F-beams into smaller parts, significantly reducing the tonnage of a single hoisting operation to adapt to shallow water construction. While protecting the marine ecological environment, it greatly improves the load-bearing capacity, construction accuracy and durability of irregular bridge structures throughout their entire life cycle.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An F-beam structure, characterized in that, Including blocks A (1), B (2), and C (3) arranged in sequence; Block A (1) includes a first vertical wall (11), and a first bottom beam (12) is provided at the bottom of the first vertical wall (11). Block B (2) includes a second vertical wall (21), and a second bottom beam (22) is provided at the bottom of the second vertical wall (21). The C block (3) includes a third vertical wall (31), the bottom of the third vertical wall (31) is provided with a third bottom beam (32), the side of the third bottom beam (32) near the second bottom beam (22) is provided with a C block bottom plate (33), the side of the third bottom beam (32) away from the second bottom beam (22) is provided with a cantilever beam (34), the cantilever beams (34) are spaced apart along the length of the C block (3), and the cantilever ends of adjacent cantilever beams (34) are connected by side beams (35); The first wet joint (100) is between the first bottom beam (12) and the second bottom beam (22), and the second wet joint (200) is between the second bottom beam (22) and the C block bottom plate (33).

2. The F-beam structure according to claim 1, characterized in that, The width of the first wet joint (100) is 1300mm ± 20mm, and the width of the second wet joint (200) is 500mm ± 20mm.

3. A design method for an F-beam structure, characterized in that, The method for designing an F-beam structure according to any one of claims 1 to 2 includes the following steps: S1. Divide the construction into stages, obtain the three-dimensional geometric parameters and material properties of beam F, and preliminarily determine the layout scheme of beam F; Perform eccentricity parameter calculation: calculate the eccentricity between the centroid and the mass center of the F beam section caused by the single-sided cantilever beam (34) and the side beam (35), and determine the initial eccentricity moment; S2. Establish finite element models corresponding to blocks A (1), B (2), and C (3) respectively. The finite element models are configured to simulate the overall stress according to the construction sequence of the first wet joint (100) and the second wet joint (200). S3. Based on the finite element model established in S2, simulate the positive bending moment prestressing tendon tensioning of blocks A (1), B (2), and C (3), the pouring of the first wet joint (100) and the second wet joint (200), and the negative bending moment tensioning process after system conversion. Perform finite element calculations to calculate the effect of the reverse moment generated by prestressing at each construction stage on the initial eccentric moment calculated in S1. S4. Based on the calculation results of S3, adjust the distribution of prestressing tendons in beam F, and repeat S3 until the prestress of beam F meets the set threshold, thus completing the design of beam F.

4. The design method for an F-beam structure according to claim 3, characterized in that, S1 divides the construction phase into three stages: F-beam prefabrication, F-beam installation, and F-beam operation.

5. The design method for an F-beam structure according to claim 3, characterized in that, In S1, the preliminary arrangement of beam F is determined, including the following steps: A preliminary plan for the arrangement of prestressing tendons in beam F is proposed, in which the prestressing tendons of beam F are arranged symmetrically and tensioned symmetrically. Preliminary plans have been drafted for the pouring of the first wet joint (100) and the second wet joint (200), as well as the pier-beam consolidation plan.

6. The design method for an F-beam structure according to claim 5, characterized in that, In S2, finite element models corresponding to blocks A (1), B (2), and C (3) are established respectively, including the following steps: A hybrid mesh combining structured and unstructured meshes was used for the finite element basis meshing. Blocks A (1) and B (2) were meshed using structured meshes, while block C (3) was meshed using unstructured meshes.

7. The design method for an F-beam structure according to claim 6, characterized in that, In S2, finite element models corresponding to blocks A (1), B (2), and C (3) are established respectively, including the following steps: The three-dimensional geometric parameters of beam F obtained by S1 are input into the three-dimensional modeling tool to construct the three-dimensional geometric model of beam F; the three-dimensional geometric parameters of beam F include the shape of block A (1), block B (2), block C (3), the arrangement of prestressing tendons, and the relationship of support positions; Based on the material properties of beam F obtained from S1, determine the mechanical property parameters of blocks A (1), B (2), and C (3), and set the mechanical properties of blocks A (1), B (2), and C (3), including elastic modulus, Poisson's ratio, density, tensile strength, and compressive strength. Set up beam and slab units for each structure of F beam, determine the specific structural state of each structure in different construction stages, set up activation / passivation units for blocks A (1), B (2), and C (3) respectively, activate or passivate the corresponding units according to the construction progress and predetermined construction nodes in each construction stage, determine the specific structural state of each structure in different construction stages, simulate the mechanical behavior of F beam in each construction stage based on the specific structural state of each structure in different construction stages, and realize the simulation of the construction sequence according to the first wet joint (100) and the second wet joint (200).

8. The design method for an F-beam structure according to claim 7, characterized in that, In S2, finite element models corresponding to blocks A (1), B (2), and C (3) are established respectively, and the following steps are also included: Based on the mechanical behavior of the F-beam at each construction stage and the actual construction conditions, the location of the support points, the type of support, and the support reaction force are set, and the constraint conditions of the support are determined. At each construction stage, loads are applied to beam F according to the construction process to simulate the stress state of beam F under different construction stages. The load application method for each construction stage is determined based on the actual construction situation, and the load changes over time are modeled.

9. The design method for an F-beam structure according to claim 3, characterized in that, S3 also includes: real-time monitoring of the vertical displacement of the side beam (35) and the deflection angle of the cross section of the F beam.

10. The design method for an F-beam structure according to claim 3, characterized in that, In S4, the distribution of prestressing tendons in beam F is adjusted, including the following steps: based on the calculation results of S3, the number and layout of prestressing tendons are determined, the number of prestressing tendons is increased in the stress concentration areas of block A (1), block B (2), and block C (3), and no prestressing tendons are set at cantilever beam (34) and side beam (35).

Images