Steel shell filled with ultra high performance concrete plate-truss composite structure and optimization design method

Abstract

This invention discloses a steel-shell composite girder structure and its optimized design method for filling ultra-high performance concrete (UHPC) within a steel shell. It relates to the field of steel-concrete composite structure technology. The key technical points are: the invention welds and fixes the lower steel plate of the bridge deck's steel shell to the upper chord and upper crossbeam of the truss, creating a continuous connection between the upper chord and the lower steel plate, forming an integrally closed frame structure with the side plates of the steel shell. During UHPC pouring, the continuity between the upper chord and the lower steel plate avoids the problem of phased pouring. This frame structure also serves as a permanent formwork for the UHPC pouring and a part of the structural load-bearing capacity, thereby enhancing the integrity between the bridge deck and the truss. By arranging perforated I-beams, shear bolts, and transverse reinforcement details between the bridge deck's steel shell, a good combination of UHPC and steel shell is achieved, forming an integrated steel-shell-UHPC composite bridge deck system, improving the bridge deck's stiffness and load-bearing capacity.

Description

Technical Field

[0001] This invention relates to the field of steel-concrete composite structure technology, and more specifically, to a plate girder composite structure with a steel shell filled with ultra-high performance concrete and an optimization design method thereon. Background Technology

[0002] With the continuous growth of transportation demand, long-span suspension bridges have been widely used due to their superior spanning capacity. The main girder structure of traditional suspension bridges is mainly a combination of steel truss girders or steel box girders and ordinary concrete bridge decks, which has revealed many defects in long-term use.

[0003] For example, traditional concrete bridge decks are heavy and have limited material strength. To support the bridge deck and transfer loads, the underlying steel trusses or box girders require dense members and complex structures, further increasing the structural weight. This not only limits the spanning capacity of suspension bridges but also leads to high material consumption and poor economic efficiency. Another example is the connection method (steel plate under the steel shell to the top plate of the truss, or the top plate of the box girder) in traditional plate-truss composite structures (bridge deck and space truss combination), which mostly uses welding or bolting. Although this method is practical, it also has drawbacks such as low construction efficiency, numerous welds, and poor fatigue resistance. Meanwhile, traditional bridge deck optimization design methods cannot fully utilize the mechanical advantages of new structures, making the development of optimization design methods for these new structures crucial.

[0004] In summary, researching and designing a steel shell-filled ultra-high performance concrete composite structure that can overcome the above-mentioned defects, and proposing an optimized design method that can give full play to the structural characteristics, are urgent problems to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a plate girder composite structure with ultra-high performance concrete filling inside a steel shell and an optimized design method. Based on structural and material innovations, this invention, combined with an optimized design method, overcomes many defects in the main beam structure of long-span bridges, resulting in higher load-bearing capacity, a lighter structure, and improved design efficiency, thus having broad application prospects.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] Firstly, a plate-truss composite structure with steel shell filled with ultra-high performance concrete is provided, including a space truss structure and a steel shell bridge deck filled with ultra-high performance concrete (13).

[0008] The space truss structure includes an upper chord (12), a lower chord (4), web members and a crossbeam (5), and the web members include vertical web members (2) and diagonal web members (3);

[0009] The steel shell bridge deck includes an upper steel plate (1), a lower steel plate (11), a side plate (14), and perforated I-beams (6), transverse reinforcing bars (10), and shear bolts installed inside the steel shell.

[0010] The lower steel plate (11) of the steel shell is welded and fixed to the upper chord (12), and forms a closed frame structure with the side plate (14) of the steel shell. The ultra-high performance concrete (13) is filled in the closed frame structure.

[0011] The upper chord (12) is a U-shaped steel pipe structure, which is filled with ultra-high performance concrete (13) and equipped with PBL shear connection key (7).

[0012] Furthermore, the lower chord (4) is made of a rectangular steel tube filled with ultra-high performance concrete (13), and two pairs of perforated PBL shear connection keys (7) are symmetrically arranged inside the tube.

[0013] Furthermore, the web of the perforated I-beam (6) is provided with a through circular hole, the transverse reinforcing bar (10) is arranged through the through circular hole, and the upper and lower flanges of the perforated I-beam (6) are welded and fixed to the upper steel plate (1) and the lower steel plate (11) of the steel shell, respectively.

[0014] Furthermore, the shear bolts include a first shear bolt (8) welded to the upper steel plate (1) of the steel shell and a second shear bolt (9) welded to the lower steel plate (11) of the steel shell.

[0015] Furthermore, the vertical web member (2), the diagonal web member (3), and the crossbeam (5) are all hollow rectangular steel pipe structures.

[0016] Secondly, an optimized design method for plate girder composite structures with steel shells filled with ultra-high performance concrete is provided, including the following steps:

[0017] Determine the dimensions of the steel shell-filled ultra-high performance concrete composite structure as described in any of the first aspects, establish a finite element model, and apply design loads in accordance with current specifications.

[0018] The initial efficiency coefficients, including the nodal efficiency coefficient, the member efficiency coefficient, and the bridge deck efficiency coefficient, are calculated based on the finite element model.

[0019] Based on the principle of constant internal force distribution and linear change of self-weight internal force, the initial efficiency coefficient is corrected by adjusting the cross-sectional dimensions.

[0020] An optimized finite element model was built based on the adjusted dimensions, the efficiency coefficient was recalculated, and the error was verified.

[0021] If the verification error meets the requirements, the final design scheme is output; otherwise, the finite element model is re-established for iterative optimization.

[0022] Furthermore, the node efficiency coefficient is the ratio of the node's bearing capacity under design load to the axial yield bearing capacity of the web member; the member efficiency coefficient is the ratio of the member's combined stress to the material's design strength under design load; and the bridge deck efficiency coefficient is the ratio of the combined bending moment value to the bending moment resistance value at the most unfavorable section of the bridge deck under design load.

[0023] Furthermore, the principle based on the constant distribution of internal forces in the structure and the linear change of internal forces due to self-weight specifically refers to:

[0024] The structural internal force distribution remains unchanged because the externally applied load and design target value remain unchanged before and after adjustment; and the self-weight internal force changes linearly because the adjusted structural weight changes linearly with the adjustment of the cross-sectional dimensions.

[0025] Furthermore, the adjustment of the cross-sectional dimensions to correct the initial efficiency coefficient includes:

[0026] Adjust the cross-sectional dimensions of the node to correct the node efficiency coefficient with the goal of having an efficiency coefficient greater than 1 and less than the upper limit of the coefficient.

[0027] The cross-sectional dimensions of the rod are adjusted to correct the efficiency coefficient of the rod with the goal of making the efficiency coefficient less than and close to 1;

[0028] In addition, the cross-sectional dimensions of the bridge deck are adjusted to correct the efficiency coefficient of the bridge deck with the goal of making the efficiency coefficient less than and close to 1.

[0029] Furthermore, the error verification specifically includes:

[0030] If the difference between the recalculated efficiency coefficient and the optimal efficiency coefficient after correction of the initial efficiency coefficient is within the allowable range, then the verification error meets the requirements.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention welds and fixes the lower steel plate of the bridge deck's steel shell to the upper chord and upper crossbeam of the truss, creating a continuous connection between the upper chord and the lower steel plate, forming an integrally closed frame structure with the side plates of the steel shell. During the casting of the UHPC (Ultra-High-Pressure Polymer), the continuity between the upper chord and the lower steel plate avoids the problem of phased casting. This frame structure also serves as a permanent formwork for the cast UHPC and part of the structural load-bearing capacity, thereby enhancing the integrity between the bridge deck and the truss. Furthermore, by arranging perforated I-beams, shear bolts, and transverse reinforcing bars across the perforated I-beams between the bridge deck's steel shell, a good composite effect between the UHPC and the steel shell is achieved, further forming an integrated "steel shell-UHPC" composite bridge deck system, improving the rigidity and load-bearing capacity of the bridge deck. Using UHPC as the filling material for the bridge deck and steel pipe truss chords, it has extremely high compressive strength, toughness and durability, which allows the bridge deck to be made thinner, reducing the structural self-weight and realizing the integrated and lightweight design of the main beam and bridge deck, laying the foundation for breakthroughs in bridge span.

[0033] 2. This invention confirms the structural dimensions based on relevant requirements and specifications, and establishes a finite element model for the preliminary design scheme. It calculates the efficiency coefficients of the initial structure, including node efficiency coefficients, member efficiency coefficients, and bridge deck efficiency coefficients. By employing simplified calculation methods in the intermediate process for structural optimization, it avoids the repeated trial calculations of the finite element model in traditional methods, significantly improving optimization efficiency. After optimization, a corresponding finite element model is established, the optimized efficiency coefficients are calculated, and their effectiveness is verified. If the verification error is large, the design scheme is revised; if the error is small, the final design scheme is determined. Traditional optimization methods require repeated iterative calculations based on the finite element model. The method presented in this paper uses simplified calculations in the intermediate optimization stages, employing finite element calculations only in the preliminary analysis and final verification stages, which significantly improves the efficiency of structural optimization design. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 This is a schematic diagram of the overall structure in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the internal structure of the bridge deck in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the steel shell enclosed structure of the bridge deck in Embodiment 1 of the present invention; Figure 4 This is a flowchart from Embodiment 2 of the present invention.

[0036] The attached diagram shows the markings and corresponding component names:

[0037] 1. Upper steel plate of the steel shell; 2. Vertical web members; 3. Diagonal web members; 4. Lower chord; 5. Horizontal beam; 6. Perforated I-beam; 7. PBL shear connection key; 8. First shear bolt; 9. Second shear bolt; 10. Transverse reinforcement; 11. Lower steel plate of the steel shell; 12. Upper chord; 13. Ultra-high performance concrete; 14. Side plates of the steel shell. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0039] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly or indirectly attached to that other component. When a component is referred to as being "connected to" another component, it can be directly or indirectly connected to that other component.

[0040] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0042] Example 1: A plate girder composite structure with a steel shell filled with ultra-high performance concrete, such as... Figures 1-3 As shown, it includes a space truss structure and a steel shell bridge deck filled with ultra-high performance concrete 13.

[0043] like Figure 1 As shown, the space truss structure consists of three truss structures arranged horizontally along the transverse direction of the bridge. The space truss structure includes chords, web members, and crossbeams 5.

[0044] The chords are divided into an upper chord (12) and a lower chord (4). The lower chord (4) consists of a rectangular steel tube filled with ultra-high performance concrete (UHPC) (13) and PBL shear connection keys (7). Its cross-sectional dimensions can be determined according to relevant specifications and engineering requirements. Two pairs of perforated PBL shear connection keys (7) are symmetrically arranged on the inner wall of the lower chord (4), forming a tenon-like structure with the UHPC to improve the shear resistance and co-load-bearing capacity of the steel-concrete interface. The upper chord (12) adopts a U-shaped steel tube structure, that is, the top plate of the rectangular steel tube is removed, leaving only the side plates and the bottom plate. Its interior is also filled with UHPC, and perforated PBL shear connection keys (7) are set at the positions of the side plates and the bottom plate to form a steel-concrete tenon-like load-bearing system to enhance shear resistance and overall stiffness.

[0045] The web members include vertical web members 2 and diagonal web members 3, both of which are hollow rectangular steel tube structures, with their cross-sectional dimensions determined according to relevant specifications. The web members connect the upper chord 12 and the lower chord 4, forming a planar truss load-bearing system and improving the overall load-bearing capacity of the structure. The crossbeams 5, also hollow rectangular steel tube structures, are arranged at various nodes to connect the three trusses in the transverse direction, thus forming a stable spatial truss system.

[0046] like Figure 2 As shown, the bridge deck is a steel shell composite structure filled with UHPC. The steel shell bridge deck includes an upper steel plate 1, a lower steel plate 11, side steel plates 14, and perforated I-beams 6, transverse reinforcing bars 10, and shear bolts installed inside the steel shell. The lower steel plate 11 is welded to the side plate of the U-shaped upper chord 12, forming an integrated closed frame structure of upper chord 12, side steel plate 14, and lower steel plate 11. Figure 3 As shown, a perforated I-beam 6 is arranged between the upper steel plate 1 and the lower steel plate 11 of the steel shell. A through-hole is provided in the web of the I-beam 6 along the cross-sectional height, and transverse reinforcing bars 10 are arranged through the through-hole. The upper and lower flanges of the perforated I-beam 6 are welded and fixed to the upper steel plate 1 and the lower steel plate 11 of the steel shell, respectively. Simultaneously, a first shear bolt 8 and a second shear bolt 9 are welded to the upper steel plate 1 and the lower steel plate 11 of the steel shell, respectively.

[0047] The UHPC is poured into the aforementioned closed frame structure. This structure serves as both a permanent formwork and participates in the structural stress, thereby significantly enhancing the overall synergy between the bridge deck and the truss. Since the upper chord 12 is continuous with the lower steel plate 11 of the steel shell, the UHPC can be cast as a whole in one go, eliminating the need for segmented construction, thus simplifying the construction process and improving construction efficiency.

[0048] Component fabrication: The upper chord 12, lower chord 4, web members, perforated I-beams 6, PBL shear connection keys 7, and shear bolts are fabricated in the factory according to the design dimensions. The truss, web members, and beams 5 are assembled and welded on the jig to form a multi-cell space truss unit, and non-destructive testing is performed.

[0049] UHPC casting: 10 transverse reinforcing bars are passed through 6 holes in the perforated I-beams. UHPC is mixed using a dedicated mixing plant and then poured using a pump. The concrete is vibrated to ensure compaction. After casting, standard curing is performed, and temperature and humidity are monitored to ensure the concrete strength meets design requirements.

[0050] This invention welds and fixes the lower steel plate 11 of the bridge deck steel shell to the upper chord 12 and upper crossbeam 5 of the truss, connecting the upper chord 12 to the lower steel plate 11, forming an integrally closed frame structure with the side plate 14 of the steel shell. During the casting of the UHPC, the connection between the upper chord 12 and the lower steel plate avoids the problem of phased casting. This frame structure also serves as a permanent formwork for the cast UHPC and part of the structural load-bearing capacity, thereby enhancing the integrity between the bridge deck and the truss. Furthermore, by arranging perforated I-beams, shear bolts, and transverse reinforcing bars 10 piercing the perforated I-beams 6 between the bridge deck steel shells, a good composite effect between the UHPC and the steel shell is achieved, further forming an integrated "steel shell-UHPC" composite bridge deck system, improving the rigidity and load-bearing capacity of the bridge deck. Using UHPC as the filling material for bridge deck and steel pipe truss chords has extremely high compressive strength, toughness and durability, which allows the bridge deck to be made thinner, reducing the structural weight and making it possible to realize suspension bridges with larger spans.

[0051] Example 2: The optimized design method for the plate girder composite structure with ultra-high performance concrete filled in the steel shell described in Example 1, such as... Figure 4 As shown, it includes the following steps:

[0052] S1: Determine the dimensions of the plate girder composite structure filled with ultra-high performance concrete inside the steel shell, establish a finite element model, and apply the design load according to the current specifications;

[0053] S2: Calculate the initial efficiency coefficients based on the finite element model, including the nodal efficiency coefficient, the member efficiency coefficient, and the bridge deck efficiency coefficient;

[0054] S3: Based on the principle of constant internal force distribution and linear change of self-weight internal force, the initial efficiency coefficient is corrected by adjusting the cross-sectional dimensions;

[0055] S4: Based on the adjusted dimensions, establish an optimized finite element model, recalculate the efficiency coefficient, and verify the error.

[0056] S5: If the verification error meets the requirements, output the final design scheme; otherwise, rebuild the finite element model and perform iterative optimization.

[0057] In step S1, the finite element model can be constructed using methods already disclosed in the prior art, and there are no restrictions on this method. Current standards include the "General Design Specifications for Highway Bridges and Culverts" (JTG D60-2015).

[0058] In step S2, nodes are crucial components of the truss structure. When a node is weaker than a member, it will fail first; conversely, a member will fail before the node. Therefore, the node efficiency coefficient is defined as the ratio of the node's bearing capacity under design load to the combined truss beam's bearing capacity at the point of web member failure. The node efficiency coefficient reflects the material utilization rate of the node. A high value indicates that the node's bearing capacity is close to the member's ultimate strength at web member failure, representing a high material utilization rate at the node.

[0059] Specifically, the formula for calculating the node efficiency coefficient is as follows:

[0060] ;

[0061] in, The node efficiency coefficient; The bearing capacity of a node, or the ultimate bearing capacity of a node, is a comprehensive capacity that depends on factors such as node geometry, welds, main pipe wall thickness, and concrete infill effect. The axial yield strength of the web member connected to the node; This represents the net cross-sectional area of ​​the steel members connected to the calculated node. ; Here is the standard value of the yield strength of the web steel, in MPa. If... If the nodes are stronger than the web members, failure will occur in the web members (the desired ductile failure mode). The nodes are weaker than the web members, and failure will occur at the nodes first (a brittle failure mode that needs to be avoided). The bearing capacity of the nodes can be obtained from relevant specifications and literature, such as the "Standard for Design of Steel Structures" GB 50017-2017.

[0062] The member efficiency coefficient is defined as the ratio of the combined stress of the member obtained by finite element numerical simulation to the strength of the material of the same cross section. Its value is less than 1. The closer it is to 1, the higher the material utilization rate of the member. Members include web members, chord members and beams.

[0063] The formula for calculating the efficiency coefficient of a link is:

[0064] ;

[0065] in, The efficiency coefficient of the link; The combined stress of the members obtained from the finite element numerical simulation is expressed in MPa. The design strength of the steel material is MPa. For the upper chord under compression, the concrete contributes significantly to the bearing capacity. Therefore, the upper chord does not need to be verified and only needs to meet the structural requirements specified in the code. The strength reduction factor is determined according to the "Design Specification for Steel Structure Bridges of Highway" (JTG D64-2015).

[0066] The bridge deck efficiency coefficient is the ratio of the combined bending moment design value of the steel-shell-ultra-high performance concrete composite bridge deck obtained through finite element numerical simulation to the bending moment resistance of the steel-shell-ultra-high performance concrete composite bridge deck at the same cross section. Its value is less than 1. The closer it is to 1, the higher the material utilization rate.

[0067] The formula for calculating the bridge deck efficiency coefficient is:

[0068] ;

[0069] in, The efficiency coefficient of the steel shell-UHPC bridge deck is less than 1, and the closer it is to 1, the higher the material utilization rate. The bending moment combination design value of the most unfavorable section of the steel shell-ultra-high performance concrete composite bridge deck obtained from finite element numerical simulation is given in kN·m. The value represents the bending moment resistance of the steel shell-ultra-high performance concrete composite bridge deck with the same cross section, in kN·m. In the calculation, it can be assumed that there is no slippage at the interface between the steel shell and the UHPC, and only the contribution of the steel plate and the UHPC can be considered, while ignoring the influence of the perforated I-beam and the transverse reinforcement. The result can be obtained through mechanical knowledge. Alternatively, a refined finite element modeling analysis can be performed to consider the contribution of the perforated I-beam and the transverse reinforcement to the bearing capacity.

[0070] For example, The calculation formula is:

[0071] ;

[0072] in, It represents the bending moment resistance value, with the unit being kN·m. It is the maximum bending moment that the structure can withstand when the composite bridge deck fails under compression. It is the overall stability coefficient of the composite bridge deck, a dimensionless parameter. Its function is to correct the instability risk of the composite deck under compression. The value ranges from 0.7 to 0.95, and is determined by the local stability of the steel plate and the confined stability of the concrete. For example, the minimum stability coefficient of the compression member should not be less than 0.7 to avoid safety hazards caused by excessive stability reduction. The upper limit of the stability coefficient of the axially compressed member is 0.95, which corresponds to the ideal working condition of short columns and no instability risk. The effective compressive area of ​​the steel plates on the composite bridge deck is measured in units of... ; It is the yield strength of the upper steel plate, in MPa, and the value should be selected according to the steel grade; It is the confinement enhancement factor of concrete, a dimensionless parameter that reflects the confinement effect of the steel plate on the concrete. For flat panels, it is 1.1-1.3, and for corrugated panels, it is 1.3-1.5. It can change the concrete from uniaxial compression to triaxial compression, thereby improving its strength. It is the net compressive area of ​​the concrete in the composite bridge deck, and the unit is ______. The calculation method is to subtract the area of ​​the upper and lower steel plates from the total cross-sectional area of ​​the composite panel; It is the axial compressive strength of concrete, and the unit is MPa; The effective compressive area of ​​the steel plate under the composite bridge deck is measured in m2. This is the yield strength of the steel plate, expressed in MPa, and the value must be determined according to the steel grade. The effective height (m) of the composite truss is the vertical distance from the centroid of the compression zone of the composite bridge deck to the centroid of the tension zone of the lower chord.

[0073] In step S3, based on the principles of constant internal force distribution and linear change of self-weight internal force, a rapid iterative correction method for the efficiency coefficient theory is constructed, which can be implemented in a spreadsheet. Specifically: constant internal force distribution means that the externally applied load and design target value remain unchanged before and after adjustment; and linear change of self-weight internal force means that the adjusted structural weight changes linearly with the adjustment of cross-sectional dimensions.

[0074] First, calculate the initial efficiency coefficient of the structure, and then calculate the proportion of self-weight stress in the structure under the combined load. Secondly, adjust the cross-sectional dimensions (for example, the cross-sectional area of ​​a certain member from...). Become Based on the adjusted cross-sectional dimensions, the internal forces and resistance values ​​of the new cross-section combination are calculated. Finally, the new efficiency coefficient is recalculated based on the new cross-sectional combined internal forces and resistance values. Finally, it is determined whether the new cross-section meets the economic and load-bearing capacity requirements. Based on the above cross-sectional dimension analysis, a systematic optimization strategy can be formulated and iterative adjustments can be performed. The entire adjustment process can be rapidly iterated in a spreadsheet environment based on basic assumptions. Each efficiency coefficient can be iterated independently or in parallel, but it is only after all efficiency coefficients meet the target that they are substituted into the finite element model for final verification.

[0075] Adjusting the cross-sectional dimensions to correct the initial efficiency coefficient includes: adjusting the cross-sectional dimensions of the nodes to correct the node efficiency coefficient with the goal of having an efficiency coefficient greater than 1 and less than the upper limit of the coefficient; adjusting the cross-sectional dimensions of the members to correct the member efficiency coefficient with the goal of having an efficiency coefficient less than and close to 1; and adjusting the cross-sectional dimensions of the bridge deck to correct the bridge deck efficiency coefficient with the goal of having an efficiency coefficient less than and close to 1.

[0076] It should be noted that if multiple efficiency coefficients simultaneously meet the target requirements, the cross-sectional dimension corresponding to the optimal solution can be selected as the final adjusted dimension.

[0077] For example, the formula for calculating the proportion of self-weight stress is:

[0078] ;

[0079] in, The self-weight stress proportion coefficient is a dimensionless number between 0 and 1. It represents the proportion of the initial stress generated by the weight of the member itself. To obtain the total stress (unit: MPa) of the member under all loads. To obtain the stress (unit: MPa) of the members under their own weight only, only the structural self-weight load is applied.

[0080] For example, the formula for calculating the newly estimated combined stress of a cross-section adjusted member is:

[0081] ;

[0082] in, The estimated combined stress of the member after adjusting the cross-section (unit: MPa). The combined stress of the members (unit: MPa) obtained from the initial finite element analysis before adjusting the cross section. The cross-sectional area of ​​the member before adjustment (unit: mm²); The cross-sectional area of ​​the member after adjustment (unit: mm²).

[0083] The above formula estimates the combined stress value. The estimation of the new efficiency coefficient applies only to the efficiency coefficient of the members. For the estimation of combined stress in bridge decks, which involves two materials (UHPC and steel), it is necessary to treat both materials as equivalent single materials using the elastic modulus ratio method. The cross-sectional area of ​​the non-dominant material must be converted into the equivalent area of ​​the dominant material (e.g., converting the concrete cross-sectional area into the steel cross-sectional area). The combined section is then transformed into an "equivalent single-material section" before applying the original formula for calculation. ,at this time The stress value corresponding to the most unfavorable position of the cross section under bending (such as the lower edge of the cross section) is given by the following formula for the converted cross section:

[0084] Equivalent area before adjustment: ;

[0085] Adjusted equivalent area: ;

[0086] in, To adjust the equivalent cross-sectional area before adjustment, ; The adjusted equivalent cross-sectional area, ; To adjust the cross-sectional area of ​​the steel before, ; The cross-sectional area of ​​the concrete before adjustment. ; The elastic modulus of steel is taken as a value in MPa according to relevant specifications. The elastic modulus of concrete is taken as a value in MPa according to relevant specifications. To adjust the cross-sectional area of ​​the steel, ; To adjust the cross-sectional area of ​​the concrete, .

[0087] For the estimation of combined stress at nodes, due to the diversity of node types, stress locations, and failure modes, the corresponding bearing capacity calculation formulas vary and cannot be summarized by a single unified expression. Therefore, when calculating the node efficiency coefficient, it is necessary to determine the bearing capacity calculation formula based on the specific node type and failure mode, according to relevant standards or literature. On this basis, the known cross-sectional area should then be considered. and stress Further solution yields and .

[0088] In step S4, an optimized finite element model is established based on the adjusted dimensions, the efficiency coefficient is recalculated, and error verification is performed.

[0089] It should be noted that when adjusting the cross section in step S3, it is not necessary to rebuild the finite element model. This step is to rebuild the finite element model with the adjusted dimensions corresponding to the optimal solution after the efficiency coefficient corrected in step S3 reaches the corresponding target requirements, and then calculate the latest efficiency coefficient based on the rebuilt finite element model.

[0090] In step S5, the error verification specifically involves verifying that if the difference between the recalculated efficiency coefficient and the optimal efficiency coefficient after the initial efficiency coefficient correction is within the allowable range, then the verification error meets the requirements.

[0091] For example, if the absolute value of the difference between the recalculated efficiency coefficient and the optimal efficiency coefficient after the initial efficiency coefficient correction is less than or equal to the error threshold, then the verification error meets the requirements.

[0092] Traditional designs for similar structures rely on finite element numerical simulations, which require repeated trial and error adjustments for verification and optimization. This process is inefficient, cumbersome, lacks clear guidance, and makes it difficult to optimize members, nodes, and bridge decks simultaneously, which can easily lead to uneven material utilization.

[0093] This invention introduces the efficiency coefficient method. The main design steps of this method are as follows: First, based on relevant requirements and specifications, the structural dimensions are initially confirmed, and a finite element model of the preliminary design scheme is established. Then, the efficiency coefficients of the initial structure are calculated, including the efficiency coefficients of nodes, members, and bridge deck. Next, the efficiency coefficients are corrected by adjusting cross-sectional dimensions, adjusting the internal forces of cross-sectional self-weight, and calculating cross-sectional resistance. After optimization, a corresponding finite element model is established, the optimized efficiency coefficients are calculated, and their effectiveness is verified. If the verification error is large, the design scheme is revised; if the error is small, the final design scheme is determined. This optimization process not only ensures the efficiency and economy of the design but also considers the feasibility of the structure and a high material utilization rate.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A plate girder composite structure with a steel shell filled with ultra-high performance concrete, characterized in that, Including a space truss structure and a steel shell bridge deck filled with ultra-high performance concrete (13); The space truss structure includes an upper chord (12), a lower chord (4), web members and a crossbeam (5), and the web members include vertical web members (2) and diagonal web members (3); The steel shell bridge deck includes an upper steel plate (1), a lower steel plate (11), a side plate (14), and perforated I-beams (6), transverse reinforcing bars (10), and shear bolts installed inside the steel shell. The lower steel plate (11) of the steel shell is welded and fixed to the upper chord (12), and forms a closed frame structure with the side plate (14) of the steel shell. The ultra-high performance concrete (13) is filled in the closed frame structure. The upper chord (12) is a U-shaped steel pipe structure, which is filled with ultra-high performance concrete (13) and equipped with PBL shear connection key (7).

2. The plate girder composite structure with steel shell filled with ultra-high performance concrete according to claim 1, characterized in that, The lower chord (4) is made of a rectangular steel tube filled with ultra-high performance concrete (13), and two pairs of perforated PBL shear connection keys (7) are symmetrically arranged inside the tube.

3. The plate girder composite structure with steel shell filled with ultra-high performance concrete according to claim 1, characterized in that, The web of the perforated I-beam (6) is provided with a through circular hole, the transverse reinforcing bar (10) is arranged through the through circular hole, and the upper and lower flanges of the perforated I-beam (6) are welded and fixed to the upper steel plate (1) and the lower steel plate (11) of the steel shell, respectively.

4. The plate girder composite structure with steel shell filled with ultra-high performance concrete according to claim 1, characterized in that, The shear bolts include a first shear bolt (8) welded to the upper steel plate (1) of the steel shell and a second shear bolt (9) welded to the lower steel plate (11) of the steel shell.

5. The plate girder composite structure with steel shell filled with ultra-high performance concrete according to claim 1, characterized in that, The vertical web members (2), the diagonal web members (3), and the crossbeams (5) are all hollow rectangular steel pipe structures.

6. An optimized design method for a plate girder composite structure with a steel shell filled with ultra-high performance concrete, characterized in that, Includes the following steps: Determine the dimensions of the steel shell-filled ultra-high performance concrete composite structure as described in any one of claims 1-5, establish a finite element model, and apply design loads according to current specifications. The initial efficiency coefficients, including the nodal efficiency coefficient, the member efficiency coefficient, and the bridge deck efficiency coefficient, are calculated based on the finite element model. Based on the principle of constant internal force distribution and linear change of self-weight internal force, the initial efficiency coefficient is corrected by adjusting the cross-sectional dimensions. An optimized finite element model was built based on the adjusted dimensions, the efficiency coefficient was recalculated, and the error was verified. If the verification error meets the requirements, the final design scheme will be output. Otherwise, rebuild the finite element model and perform iterative optimization.

7. The optimized design method for a steel shell-filled ultra-high performance concrete plate girder composite structure according to claim 6, characterized in that, The node efficiency coefficient is the ratio of the node's bearing capacity under design load to the axial yield bearing capacity of the web member; The efficiency coefficient of the member is the ratio of the combined stress of the member under the design load to the design strength of the material; The bridge deck efficiency coefficient is the ratio of the bending moment combination value to the bending moment resistance value at the most unfavorable section of the bridge deck under the design load.

8. The optimized design method for a steel shell-filled ultra-high performance concrete plate girder composite structure according to claim 6, characterized in that, The principle based on the constant distribution of internal forces in the structure and the linear change of internal forces due to self-weight is as follows: The structural internal force distribution remains unchanged because the externally applied load and design target value remain unchanged before and after adjustment; and the self-weight internal force changes linearly because the adjusted structural weight changes linearly with the adjustment of the cross-sectional dimensions.

9. The optimized design method for a steel shell-filled ultra-high performance concrete plate girder composite structure according to claim 6, characterized in that, The adjustment of the cross-sectional dimensions to correct the initial efficiency coefficient includes: Adjust the cross-sectional dimensions of the node to correct the node efficiency coefficient with the goal of having an efficiency coefficient greater than 1 and less than the upper limit of the coefficient. The cross-sectional dimensions of the rod are adjusted to correct the efficiency coefficient of the rod with the goal of making the efficiency coefficient less than and close to 1; In addition, the cross-sectional dimensions of the bridge deck are adjusted to correct the efficiency coefficient of the bridge deck with the goal of making the efficiency coefficient less than and close to 1.

10. The optimized design method for a steel shell-filled ultra-high performance concrete composite plate girder structure according to claim 6, characterized in that, The error verification specifically involves: If the difference between the recalculated efficiency coefficient and the optimal efficiency coefficient after correction of the initial efficiency coefficient is within the allowable range, then the verification error meets the requirements.

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