A thin-walled box culvert prestress partition design method

Abstract

The application discloses a kind of thin-walled stacked box aqueduct prestress zoning design methods, it is related to the technical field of hydraulic engineering and bridge engineering design.The method constructs water-gas interface discontinuous temperature difference distribution field using quasi-step smooth operator, truly reproduces temperature fault at water level line;Then temperature difference field and radial water pressure, concrete time-varying shrinkage and creep effect are applied to the three-dimensional finite element model of thin-walled stacked box aqueduct as combined load;Then introduce construction deviation vector, combined with sensitivity matrix to calculate stress disturbance envelope value and robustness index, divide aqueduct into safety zone, transition zone and fragile zone;Again, failure diagnosis operator is calculated for fragile zone node, and the corresponding optimization instruction is executed according to the failure diagnosis operator;Finally, the optimized construction parameters are output, which solves the problems of load distortion, mechanical disconnection and design construction fault in existing stacked box aqueduct prestress design technology.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and bridge engineering design technology, specifically to a prestressed zoning design method for thin-walled stacked box girder aqueducts. Background Technology

[0002] As a key hydraulic structure controlling inter-regional water transfer projects, the prestressed design of thin-walled caisson aqueducts directly affects the safety and durability of the structure. Current hydraulic engineering and bridge design codes generally use the following two simplified models when calculating the temperature stress of thin-walled caisson aqueducts:

[0003] The first type, continuous distribution model, assumes that the temperature decreases smoothly or linearly with the height of the cross section.

[0004] The second type, homogeneous boundary model, treats the structure as a whole exposed to air or submerged in water, ignoring abrupt changes in the physical medium at the water level.

[0005] In the prestressed design stage, traditional methods rely on empirical formulas and a single safety factor, lacking quantitative analysis of the mutual interference between vertical, horizontal, U-shaped, and other multi-directional prestressed tendons.

[0006] The above methods reveal the following three core problems when applied to practical engineering:

[0007] 1. Load input distortion: The quasi-step temperature jump caused by the difference in heat capacity at the water-air interface is ignored, resulting in a serious underestimation of the local tensile stress in the web of the water-facing side (saddle plate area).

[0008] 2. Disconnection in mechanical analysis: The strong "clamping effect" of flowing water on the submerged concrete is not considered. That is, the water acts as a "thermal axis" and exerts a strong stretch on the shrinking upper concrete. This effect is completely flattened in the traditional continuous model.

[0009] 3. Design and construction failure: Existing solutions only provide static stress results and cannot quantitatively assess the impact of construction deviations (such as duct positioning offset and tension error) on the final compressive stress reserve, making the design results prone to failure in actual construction and lacking robustness.

[0010] In summary, the existing prestressed design technology for stacked box girder aqueducts suffers from problems such as load distortion, mechanical disconnect, and design-construction discontinuity, leading to the long-standing industry problem of design-qualified products cracking on-site. Summary of the Invention

[0011] The technical problem to be solved by this invention is that existing thin-walled stacked box girder aqueduct prestressed design technology suffers from problems such as load input distortion, disconnect between mechanical analysis and design and construction, resulting in the industry pain point of qualified design but cracking on site. The purpose is to provide a prestressed zoning design method for thin-walled stacked box girder aqueducts, which solves the above problems.

[0012] This invention is achieved through the following technical solution:

[0013] In a first aspect, the present invention provides a prestressed zoning design method for thin-walled stacked box girder aqueducts, comprising:

[0014] A three-dimensional finite element model of a thin-walled stacked box aqueduct is established. A quasi-step smoothing operator is introduced to construct a discontinuous temperature difference distribution field that considers the sudden change in heat capacity of the water-air interface medium. The temperature difference distribution field, radial water pressure, and concrete time-varying shrinkage and creep effect are applied as composite loads to the model. The reference principal tensile stress and prestress reserve of key nodes in the aqueduct under the most unfavorable working condition combination are extracted.

[0015] The various types of prestress within the aqueduct are defined parametrically, and the stress response gradient of each prestress to each key node is extracted to establish a sensitivity matrix.

[0016] Based on the sensitivity matrix and the preset construction deviation vector, the stress disturbance envelope value of each key node is calculated. Based on the reference principal tensile stress, the prestress reserve and the stress disturbance envelope value, the robustness index is calculated. Based on the robustness index, the aqueduct is divided into a safe zone, a transition zone and a vulnerable zone.

[0017] For each critical node in the vulnerable zone, a failure diagnosis operator is calculated based on the sensitivity matrix, and corresponding optimization instructions are executed according to the failure diagnosis operator until the robustness index of each critical node reaches the preset safety threshold, and the optimized construction parameters are output; the construction parameters are used to guide the prestressed construction of the aqueduct.

[0018] Optionally, the mathematical expression for the discontinuous temperature difference distribution field is as follows:

[0019]

[0020] in, For discontinuous temperature kernel functions; These are the height coordinates along the web of the aqueduct; The water in the flooded area is at an equivalent constant temperature; The equivalent air temperature in the air cavity region affected by alternating sunlight and convection; To design the water level height; Let be the smooth step function for the transition segment that has a maximum first derivative at the design water level.

[0021] Optionally, the various types of prestressing include vertical prestressing, U-shaped prestressing, and transverse prestressing;

[0022] The sensitivity matrix contains Poisson interferometry terms and curvature mapping terms; the Poisson interferometry terms are used to quantify the weakening effect of the transverse material expansion caused by the vertical prestress on the transverse prestress reserve; the transverse prestress reserve is the transverse component of the prestress reserve.

[0023] The curvature mapping term is used to quantify the superposition effect of centripetal radial compressive forces generated by the U-shaped prestress in the saddle-shaped curvature section.

[0024] Optionally, the formula for calculating the stress disturbance envelope value is as follows:

[0025]

[0026] in, The stress disturbance envelope value; This is the sensitivity matrix; The construction deviation vector includes the geometric deviation of the duct spatial positioning and the tension control error.

[0027] Optionally, the robustness index is calculated using the following formula:

[0028]

[0029] in, The robustness index is mentioned above; The reference principal tensile stress; This is for the storage of pre-stress.

[0030] Optionally, dividing the aqueduct into a safe zone, a transition zone, and a vulnerable zone based on the robustness index includes:

[0031] If the robustness index of any critical node Then the area where the critical node is located is designated as a safe zone;

[0032] If the robustness index of any critical node satisfies Then the area where the key node is located is designated as a transition zone;

[0033] If the robustness index of any critical node Then the area where the critical node is located is classified as a vulnerable area.

[0034] Optionally, the calculation formula for the failure diagnosis operator is as follows:

[0035]

[0036] in, For the failure diagnosis operator; For nodal stress; For spatial curvature; This represents the tension amplitude of the prestress; This indicates the sensitivity of nodal stress to spatial curvature. This indicates the sensitivity of nodal stress to the tension amplitude of prestress.

[0037] Optionally, executing the corresponding optimization instructions based on the failure diagnosis operator includes:

[0038] When the failure diagnosis operator is greater than the preset diagnosis threshold, a geometric trajectory reconstruction optimization instruction is executed; the geometric trajectory reconstruction optimization instruction is used to increase the tangential extrusion force by adjusting the curve of the U-shaped prestress.

[0039] When the failure diagnosis operator is less than or equal to the preset diagnosis threshold, a multi-directional stress decoupling compensation optimization instruction is executed; the multi-directional stress decoupling compensation optimization instruction is used to offset the Poisson effect by coordinating the adjustment of the multiple types of prestress.

[0040] Optionally, the step of executing corresponding optimization instructions according to the failure diagnosis operator until the robustness indicators of each key node reach the preset safety threshold, and outputting optimized construction parameters, includes:

[0041] Execute corresponding optimization instructions according to the failure diagnosis operator until the robustness index of each key node reaches the preset safety threshold.

[0042] A prestress extreme value decay function with time variable is constructed, and the residual compressive stress is verified according to the function under the most unfavorable working condition within the specified service life. The function includes concrete creep, shrinkage and long-term relaxation degradation factors of prestressed steel bars.

[0043] If yes, output the optimized construction parameters; if no, re-execute the optimization command.

[0044] Optionally, the construction parameters include the optimized three-dimensional spatial geometric coordinates of the steel strand, the prestressed tension control force data of the steel strand, and the allowable limit of construction deviation; the allowable limit of construction deviation is derived by reverse derivation based on the optimized robustness margin and the sensitivity matrix; the optimized robustness margin is the product of the optimized robustness index and the stress disturbance envelope value.

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] This application provides a prestressed zoning design method for thin-walled stacked box girder aqueducts. First, a discontinuous temperature difference distribution field is constructed using a quasi-step smoothing operator, mathematically reproducing the temperature discontinuity at the water level (rather than the traditional continuous smoothing assumption). This makes the temperature load input closer to physical reality, solving the fundamental problem of stress underestimation due to load distortion. Then, the discontinuous temperature difference distribution field is nonlinearly superimposed with radial water pressure and the time-varying shrinkage and creep effect of concrete to form a combined load. The temperature difference field reproduces the temperature boundary conditions of the water body as a "thermal axis," and the water pressure reproduces the hydrostatic load. The coupling effect of these two elements accurately reflects the constraint effect of the water body on the concrete, solving the problem of disconnect between mechanical analysis and practical application. Finally, by introducing a construction deviation vector, calculating the stress disturbance envelope value, defining robustness indicators, performing zoning judgment, targeting and optimizing vulnerable areas, and outputting executable construction parameters, a complete closed loop from design stress analysis to construction quality control is formed, fundamentally solving the design-construction discontinuity problem. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0048] Figure 1 A schematic flowchart illustrating a prestressed zoning design method for thin-walled stacked box aqueducts provided in an embodiment of this application;

[0049] Figure 2 A comparative illustration of the discontinuous temperature field provided in the embodiments of this application and the traditional model. Figure 1 ;

[0050] Figure 3 A comparative illustration of the discontinuous temperature field provided in the embodiments of this application and the traditional model. Figure 2 ;

[0051] Figure 4 Spatial distribution cloud map of the robustness index of the saddle-shaped region provided in the embodiments of this application;

[0052] Figure 5 A comparative schematic diagram showing the U-shaped rib trajectory before and after optimization, provided in an embodiment of this application;

[0053] Figure 6 A bar chart comparing the full lifecycle robustness verification provided in the embodiments of this application. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining this invention and are not intended to limit this invention.

[0055] To address the problems of load input distortion, disconnect between mechanical analysis and design, and design-construction gaps in existing prestressed design technologies for thin-walled caisson aqueducts, this application provides a prestressed zoning design method for thin-walled caisson aqueducts. This method is not only applicable to hydraulic aqueducts but can also be extended to any engineering field with liquid-gas interfaces and thin-walled structures, such as LNG storage tanks, cross-sea water diversion tunnel linings, and large-scale sewage treatment ponds. Any prestressed thin-walled structure with abrupt media interfaces or sensitivity to temperature gradients and construction deviations can be designed using the prestressed zoning design method for thin-walled caisson aqueducts provided by this invention.

[0056] Please refer to Figure 1 This is a schematic flowchart of a prestressed zoning design method for thin-walled stacked box girder aqueducts provided in this application embodiment. The following is a further explanation. Figure 1 The prestressed zoning design method for thin-walled stacked box aqueducts is introduced.

[0057] S1. Establish a three-dimensional finite element model of the thin-walled stacked box aqueduct, introduce a quasi-step smoothing operator to construct a discontinuous temperature difference distribution field that considers the sudden change in heat capacity of the water-air interface medium, and apply the temperature difference distribution field, radial water pressure, and concrete time-varying shrinkage and creep effect as a composite load to the model, and extract the benchmark principal tensile stress and prestress reserve of key nodes in the aqueduct under the most unfavorable working condition combination.

[0058] In the specific implementation process, the first step is to establish a three-dimensional finite element model of the thin-walled stacked box aqueduct.

[0059] Then, a quasi-step smoothing operator is introduced to construct a discontinuous temperature difference distribution field that considers the abrupt change in heat capacity at the water-air interface. The specific mathematical expression is as follows:

[0060]

[0061] in, For discontinuous temperature kernel functions; These are the height coordinates along the web of the aqueduct; The water in the flooded area is at an equivalent constant temperature; The equivalent air temperature in the air cavity region affected by alternating sunlight and convection; To design the water level height; Let be the smooth step function for the transition segment that has a maximum first derivative at the design water level.

[0062] Using a smooth step function in the transition section It can calculate the local self-constrained shear stress at the water-air interface, overcoming the technical deficiency of traditional continuous temperature models that underestimate the stress at this interface. (Smooth step function for transition section) It can be achieved using various smoothing methods such as trigonometric functions, error functions, and sigmoid functions. Its core is to ensure that the peak value of the first derivative is presented at the water level line, so as to truly reproduce the physical characteristics of temperature faults at the water-air interface.

[0063] Next, the aforementioned temperature difference field is nonlinearly superimposed with radial water pressure and the time-varying shrinkage and creep effect of concrete to form a complete combination of environmental loads, which is then applied to the three-dimensional finite element model.

[0064] Finally, using a three-dimensional solid model (such as ANSYS), the three-dimensional finite element model under the applied composite load was solved to extract the baseline principal tensile stress and preload stress reserves of key nodes within the aqueduct under the most unfavorable working conditions. Among these, the key nodes are critical weak points such as the saddle-shaped transverse diaphragm and the web on the water-facing side.

[0065] S2. Parameterize the various types of prestress within the aqueduct, extract the stress response gradient of each prestress to each key node, and establish a sensitivity matrix.

[0066] In practical implementation, the prestressed tendons in thin-walled stacked box girder aqueducts are classified according to their tensioning direction and application area, defining multiple types of prestressed tendons:

[0067] (1) Vertical prestressing Arranged in the web, tensioned along the height direction;

[0068] (2) U-shaped prestressed Arranged along the saddle-shaped transverse diaphragm, forming a U-shaped curve;

[0069] (3) Transverse prestress: including bottom transverse prestress and transverse prestressing of the top slab Bottom transverse prestressing Prestressed in the base slab, tensioned along the cross-sectional direction; transverse prestressed in the top slab. It is placed on the top slab and tensioned along the cross section.

[0070] The above four types of prestressing constitute the prestressing tensioning vector set. .

[0071] Apply small disturbances to each type of prestressing By using the finite element unit perturbation sampling method, the stress response gradient of each key node under prestress in all directions is calculated, and a system is constructed. First-order sensitivity matrix Sensitivity matrix The expression used to characterize the spatial crack-prevention coupling interference effect of multi-directional prestressed tendons is as follows:

[0072]

[0073] in, Sensitivity matrix The matrix element in the i-th row and j-th column, This represents the stress value at the j-th critical node; It is represented as the tension amplitude of the prestress in the i-th direction.

[0074] Sensitivity matrix The matrix elements must contain at least the following characteristic partial differential terms:

[0075] Poisson interference term ( ): Used to quantify the weakening effect of transverse material expansion caused by vertical prestress on transverse prestress reserve; transverse prestress reserve is the transverse component of prestress reserve.

[0076] Curvature mapping term ( ): The curvature mapping term is used to quantify the superposition effect of centripetal and radial compressive forces generated by U-shaped prestress in the saddle-shaped curvature section.

[0077] S3. Based on the sensitivity matrix and the preset construction deviation vector, calculate the stress disturbance envelope value of each key node, calculate the robustness index based on the benchmark principal tensile stress, prestress reserve and stress disturbance envelope value, and divide the aqueduct into safe zone, transition zone and vulnerable zone based on the robustness index.

[0078] In one possible embodiment, the root sum of squares (RSS) method is used for multi-source deviation coupling superposition, and the formula for calculating the stress perturbation envelope value is as follows:

[0079]

[0080] in, This represents the stress disturbance envelope value; This is the sensitivity matrix; This is the construction deviation vector, used to characterize on-site uncertainties; , Geometric deviation for spatial positioning of the duct; This refers to the tension control error.

[0081] In this embodiment of the application, the quantitative decoupling and superposition of multi-source construction deviations are realized through the coupled calculation of the sensitivity matrix and the construction deviation vector, which can accurately assess the contribution ratio of each deviation source to stress disturbance.

[0082] In one possible embodiment, the robustness index is calculated using the following formula:

[0083]

[0084] in, Robustness index is a dimensionless proprietary parameter used to determine the sensitivity of a structure to construction deviations. The reference principal tensile stress; This is to reserve pre-stress.

[0085] Compared to traditional methods that only focus on deterministic stress states (such as...) (i.e., deemed safe). In this embodiment of the application, by introducing the stress disturbance envelope value Γ as the denominator, the physical essence of "even if the static reserve is positive, if the disturbance caused by construction deviation is too large, the structure may still crack" is revealed, filling the gap in the existing design specifications in terms of quantifying construction uncertainty.

[0086] In one possible embodiment, the step of dividing the aqueduct into a safe zone, a transition zone, and a vulnerable zone based on robustness indicators includes:

[0087] If the robustness index of any critical node Then the area where the critical node is located is designated as a safe zone;

[0088] If the robustness index of any critical node satisfies Then the area where the key node is located is designated as a transition zone;

[0089] If the robustness index of any critical node Then the area where the critical node is located is classified as a vulnerable area.

[0090] In this embodiment, the safe zone refers to an area with sufficient compressive stress reserve and insensitive to construction deviations, where conventional design and construction standards can be adopted; the transition zone refers to an area with moderate compressive stress reserve and relatively sensitive to construction deviations, where construction quality control needs to be strengthened (such as increasing the detection frequency and reducing the deviation limit); the vulnerable zone refers to an area with insufficient compressive stress reserve and highly sensitive to construction deviations, where automatic optimization commands must be triggered for targeted reinforcement.

[0091] S4. For each critical node in the vulnerable area, calculate the failure diagnosis operator based on the sensitivity matrix, and execute the corresponding optimization instructions according to the failure diagnosis operator until the robustness index of each critical node reaches the preset safety threshold, and output the optimized construction parameters.

[0092] In one possible embodiment, the calculation formula for the failure diagnosis operator is as follows:

[0093]

[0094] in, For failure diagnosis operators; For nodal stress; For spatial curvature; This represents the tension amplitude of the prestress; This indicates the sensitivity of nodal stress to spatial curvature. This indicates the sensitivity of nodal stress to the tension amplitude of prestress.

[0095] In one possible embodiment, the step of executing the corresponding optimization instructions based on the failure diagnosis operator includes:

[0096] When the failure diagnosis operator is greater than the preset diagnosis threshold, the geometric trajectory reconstruction optimization command is executed; the geometric trajectory reconstruction optimization command is used to increase the tangential extrusion force by adjusting the curve of the U-shaped prestress;

[0097] When the failure diagnosis operator is less than or equal to the preset diagnosis threshold, the multi-directional stress decoupling compensation optimization instruction is executed; the multi-directional stress decoupling compensation optimization instruction is used to offset the Poisson effect by coordinating the adjustment of multiple types of prestress.

[0098] In the specific implementation process, if The nodes in the vulnerable area are determined to be dominated by geometric constraint failure, and the geometric trajectory reconstruction optimization command is automatically triggered: For the U-shaped prestressed spatial spline curve of the saddle-shaped region, a curvature energy penalty term is introduced to construct a comprehensive objective function; by solving the shape-corrected Jacobian matrix J, under the premise of satisfying the physical limit of the sidewall thickness of the stacked box and the minimum bending radius of the material, the curvature radius R of the local control vertex is iteratively reduced, so as to directly offset the environmental tensile stress with the increase of the centripetal radial extrusion force.

[0099] like If the node in the vulnerable area is determined to be dominated by coupled stress imbalance, a multi-directional stress decoupling compensation optimization command is automatically triggered: using the sensitivity matrix. inverse matrix Solving for the multi-directional prestressing co-tensioning increment vector required to increase the compressive stress reserve target threshold. While increasing the tension amplitude of the unidirectional prestress, the tension increment of the prestress in the other orthogonal directions is simultaneously adjusted according to the off-diagonal interference term to counteract the secondary tensile stress caused by the Poisson effect.

[0100] In one possible embodiment, the steps of executing corresponding optimization instructions according to the failure diagnosis operator until the robustness index of each key node reaches the preset safety threshold and outputting the optimized construction parameters include:

[0101] Execute the corresponding optimization instructions according to the failure diagnosis operator until the robustness index of each key node reaches the preset safety threshold; construct the prestress extreme value decay function with time variable, and verify whether the structure still has residual compressive stress under the most unfavorable working condition within the specified lifespan of the structure; the function includes concrete creep, shrinkage and long-term relaxation degradation factors of prestressed steel bars; if yes, output the optimized construction parameters; if not, re-execute the optimization instructions.

[0102] In the specific implementation process, a preset safety threshold of 1.5 is adopted, meaning that the robustness index of all key nodes is required to be greater than 1.5. A prestress extreme value decay function incorporating the time variable t is constructed. The study incorporates concrete creep, shrinkage, and long-term relaxation and degradation factors of prestressed steel bars. It verifies whether the optimized and reconstructed prestressed system still exhibits residual compressive stress under the most unfavorable working conditions throughout its specified lifespan (e.g., 100 years). ).

[0103] If the full lifecycle verification is passed (i.e.) ], If the value is >0, then the optimized construction parameters will be output; if the full life cycle verification fails (i.e., there is a moment when the value is >0), .... If the value is ≤0, the system will automatically return to the optimization instruction step, readjust the optimization strategy according to the reason for failure (such as further increasing the tangential extrusion force or redistributing the collaborative increment), and iterate again until the full life cycle verification is passed.

[0104] In this embodiment of the application, short-term robustness achievement (S>1.5) and long-term lifecycle verification are established. The dual safety criterion of >0 incorporates concrete creep, shrinkage, and long-term relaxation degradation factors of prestressed steel bars into the prestress extreme value attenuation function, forming a deterministic closed-loop iterative mechanism to ensure that the final output construction parameters simultaneously meet the requirements of resistance to construction deviation and resistance to time-varying degradation.

[0105] In one possible embodiment, the construction parameters include the optimized spatial geometric coordinates of the prestressed steel strands, the prestressing control force data of the steel strands, and the allowable limit of construction deviation; the allowable limit of construction deviation is derived in reverse from the optimized robustness margin and sensitivity matrix; the optimized robustness margin is the product of the optimized robustness index and the stress disturbance envelope value.

[0106] In the specific implementation process, firstly, the robustness index and stress perturbation envelope value after optimization and convergence are extracted. Then, the optimized robustness margin is calculated: ;in, To optimize the robustness metrics of key nodes after convergence, This represents the corresponding stress disturbance envelope value. According to the definition of robustness index... It can be known that That is, the robustness margin is equal to the effective compressive stress reserve.

[0107] Next, the robustness margin is allocated to a single construction deviation variable dimension. Under the constraint that the stress envelope of each key node after optimization does not exceed the lower limit of the tensile design strength of concrete, the maximum allowable drift vector field of the spatial positioning point on the three-dimensional axis is calculated inversely using the sensitivity matrix. That is, the allowable limit of construction deviation without violating the structural safety boundary. .

[0108] Finally, the optimized three-dimensional spatial geometric coordinates, tension control force data, and allowable construction deviation limits are output as a digital instruction set to guide the prestressed construction of the thin-walled stacked box girder aqueduct.

[0109] In this embodiment, by deriving the allowable limit of construction deviation in reverse from the robustness margin, the abstract robustness index is transformed into specific and executable construction instructions such as "the positioning deviation does not exceed a certain number of millimeters and the tensioning error does not exceed a certain percentage". This achieves seamless information integration from design stress analysis to on-site construction control, and completely breaks down the gap between design and construction.

[0110] The following example, using the optimization of the saddle-shaped zone of a 40m span thin-walled stacked box duct in a certain project, illustrates the prestressed zoning design method for thin-walled stacked box ducts provided in this application.

[0111] The project uses a 40m span thin-walled stacked box girder aqueduct, made of C50 concrete with a wall thickness of 350mm. The original design had a theoretical compressive stress reserve of 1.25MPa at the saddle-shaped turning point (node ​​1024#), but horizontal cracks have appeared multiple times during operation.

[0112] First, a baseline field scan is performed: input summer sunshine hours and highest water level, and the results are calculated. (pull), (Compression), Static effective compressive stress reserve .

[0113] Please refer to Figure 2 This is a schematic diagram comparing the discontinuous temperature field provided in the embodiments of this application with the traditional model. Figure 1 Please refer to Figure 3 This is a schematic diagram comparing the discontinuous temperature field provided in the embodiments of this application with the traditional model. Figure 2 The vertical axis represents height y, and the horizontal axis represents temperature / stress. As can be seen, the traditional model is a smooth curve, while the discontinuous temperature field provided by this invention is a curve with step jumps.

[0114] Secondly, robustness quantification is performed: construction deviations are set. The perturbation was calculated using finite element analysis (FEA). Calculated It was identified as a vulnerable area.

[0115] Please refer to Figure 4 This is a spatial distribution cloud map of the robustness index of the saddle-shaped region provided in the embodiments of this application. Figure 4 Area A in the diagram represents the safe zone, area B represents the transition zone, and area C represents the vulnerable zone. Figure 4 The image clearly shows that areas B and C before optimization have been transformed into area A after optimization.

[0116] Then, diagnosis and optimization are performed: Calculate the failure diagnosis operator. The failure was determined to be primarily due to geometric constraint failure. The system drives the FEA to adjust the radius of curvature of the U-shaped reinforcement in that segment. Optimized from 12.0m to 10.5m.

[0117] Please refer to Figure 5 This is a comparative diagram showing the U-shaped rib trajectory before and after optimization, provided in an embodiment of this application. Figure 5 The left side shows the original fixed-radius circular arc, and the right side shows the optimized variable-curvature spline curve. A magnified view of the local curvature radius can be seen. The reduction of tangential compressive force vector and the enhancement of tangential compressive force vector.

[0118] Finally, verify the results: Please refer to... Figure 6 The bar chart shows the comparison of the robustness verification throughout the entire life cycle provided by the embodiments of this application. Under the initial completion condition, the traditional solution can only achieve S=0.82 (vulnerable zone), while the solution of this invention improves S to 1.54 (safe zone) through optimization. After 100 years of creep, the traditional solution decays to S=0.10, close to the risk of cracking, while the solution of this invention still maintains S=0.95 (transition zone). Under the most unfavorable construction deviation triggering condition (δ=15 mm), the traditional solution shows a negative value S=−0.20, indicating that the structure has cracked and failed, while the solution of this invention still maintains S=0.45>0, and the structure is always under full cross-sectional compression.

[0119] As can be seen, the present invention successfully transforms the inherently fragile point into a highly robust and safe system by simply finely adjusting the geometry of the U-shaped reinforcement, with the total amount of prestress increasing by only 2.3%, demonstrating the effectiveness and reliability of the present invention.

[0120] In summary, this application provides a prestressed zoning design method for thin-walled stacked box girder aqueducts, which has the following beneficial effects:

[0121] 1. Addressing Industry Pain Points: The stress peaks at the water-air interface are mathematically reproduced, solving the problem of design safety but on-site cracking caused by load model distortion. The calculation accuracy is improved by over 40% compared to traditional methods.

[0122] 2. Achieve precise targeted design: Abandoning the extensive mode of global equidistant reinforcement, by using the robustness index S and the failure diagnosis operator η, only a small amount of reinforcement is needed in the weak area (such as adding 10% U-shaped reinforcement redundancy), which can improve the robustness index of the weak point from S=0.82 to S=1.54.

[0123] 3. Bridging the gap between design and construction: Through a reverse mapping mechanism, complex mechanical optimization results are transformed into allowable limits for construction deviations that workers can implement, so that design results can be truly implemented, greatly improving the reliability and economy of the project.

[0124] 4. Robust throughout the entire life cycle: Through time-varying verification, it ensures that the structure can still withstand extreme working conditions after a hundred years of service, moving from meeting current specifications to preventing future risks.

[0125] Based on the same inventive concept, this application also provides a computer device, which includes a processor, a memory, and a computer program stored in the memory. The computer program is executed by the processor to implement the aforementioned prestressed zoning design method for thin-walled stacked box aqueducts.

[0126] Based on the same inventive concept, this application also provides a computer storage medium storing a computer program, which is executed by a processor to implement the aforementioned prestressed zoning design method for thin-walled stacked box aqueducts.

[0127] In some embodiments, the computer-readable storage medium may be a memory such as FRAM, ROM, PROM, EPROM, EEPROM, flash memory, magnetic surface memory, optical disk, or CD-ROM; or it may be a device including one or any combination of the above-mentioned memories. The computer may be a variety of computing devices, including smart terminals and servers.

[0128] In some embodiments, executable instructions may take the form of a program, software, software module, script, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0129] As an example, executable instructions may, but do not necessarily, correspond to files in the file system. They may be stored as part of a file that holds other programs or data, for example, in one or more scripts in a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple collaborative files (e.g., a file that stores one or more modules, subroutines, or code sections).

[0130] As an example, executable instructions can be deployed to execute on a single computing device, or on multiple computing devices located in one location, or on multiple computing devices distributed across multiple locations and interconnected via a communication network.

[0131] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0132] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0133] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are 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 prestressed zoning design method for thin-walled stacked box girder aqueducts, characterized in that, include: A three-dimensional finite element model of a thin-walled stacked box aqueduct is established. A quasi-step smoothing operator is introduced to construct a discontinuous temperature difference distribution field that considers the sudden change in heat capacity of the water-air interface medium. The temperature difference distribution field, radial water pressure, and concrete time-varying shrinkage and creep effect are applied as composite loads to the model. The reference principal tensile stress and prestress reserve of key nodes in the aqueduct under the most unfavorable working condition combination are extracted. The various types of prestress within the aqueduct are defined parametrically, and the stress response gradient of each prestress to each key node is extracted to establish a sensitivity matrix. Based on the sensitivity matrix and the preset construction deviation vector, the stress disturbance envelope value of each key node is calculated. Based on the reference principal tensile stress, the prestress reserve and the stress disturbance envelope value, the robustness index is calculated. Based on the robustness index, the aqueduct is divided into a safe zone, a transition zone and a vulnerable zone. For each critical node in the vulnerable zone, a failure diagnosis operator is calculated based on the sensitivity matrix, and corresponding optimization instructions are executed according to the failure diagnosis operator until the robustness index of each critical node reaches the preset safety threshold, and the optimized construction parameters are output; the construction parameters are used to guide the prestressed construction of the aqueduct.

2. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The mathematical expression for the discontinuous temperature difference distribution field is as follows: ； in, For discontinuous temperature kernel functions; These are the height coordinates along the web of the aqueduct; The water in the flooded area is at an equivalent constant temperature; The equivalent air temperature in the air cavity region affected by alternating sunlight and convection; To design the water level height; Let be the smooth step function for the transition segment that has a maximum first derivative at the design water level.

3. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The various types of prestressing include vertical prestressing, U-shaped prestressing, and transverse prestressing; The sensitivity matrix contains Poisson interferometry terms and curvature mapping terms; the Poisson interferometry terms are used to quantify the weakening effect of the transverse material expansion caused by the vertical prestress on the transverse prestress reserve; the transverse prestress reserve is the transverse component of the prestress reserve. The curvature mapping term is used to quantify the superposition effect of centripetal radial compressive forces generated by the U-shaped prestress in the saddle-shaped curvature section.

4. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The formula for calculating the stress disturbance envelope value is as follows: ； in, The stress disturbance envelope value; This is the sensitivity matrix; The construction deviation vector includes the geometric deviation of the duct spatial positioning and the tension control error.

5. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The formula for calculating the robustness index is as follows: ； in, The robustness index is mentioned above; The reference principal tensile stress; This is for the storage of pre-stress.

6. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The division of the aqueduct into a safe zone, a transition zone, and a vulnerable zone based on the robustness index includes: If the robustness index of any critical node Then the area where the critical node is located is designated as a safe zone; If the robustness index of any critical node satisfies Then the area where the key node is located is designated as a transition zone; If the robustness index of any critical node Then the area where the critical node is located is classified as a vulnerable area.

7. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The calculation formula for the failure diagnosis operator is as follows: ； in, For the failure diagnosis operator; For nodal stress; For spatial curvature; This represents the tension amplitude of the prestress; This indicates the sensitivity of nodal stress to spatial curvature. This indicates the sensitivity of nodal stress to the tension amplitude of prestress.

8. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 3, characterized in that, The step of executing corresponding optimization instructions based on the failure diagnosis operator includes: When the failure diagnosis operator is greater than the preset diagnosis threshold, a geometric trajectory reconstruction optimization instruction is executed; the geometric trajectory reconstruction optimization instruction is used to increase the tangential extrusion force by adjusting the curve of the U-shaped prestress. When the failure diagnosis operator is less than or equal to the preset diagnosis threshold, a multi-directional stress decoupling compensation optimization instruction is executed; the multi-directional stress decoupling compensation optimization instruction is used to offset the Poisson effect by coordinating the adjustment of the multiple types of prestress.

9. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The process involves executing corresponding optimization instructions based on the failure diagnosis operator until the robustness indicators of each key node reach a preset safety threshold, and then outputting optimized construction parameters, including: Execute corresponding optimization instructions according to the failure diagnosis operator until the robustness index of each key node reaches the preset safety threshold. A prestress extreme value decay function with time variable is constructed, and the residual compressive stress is verified according to the function under the most unfavorable working condition within the specified service life. The function includes concrete creep, shrinkage and long-term relaxation degradation factors of prestressed steel bars. If yes, output the optimized construction parameters; if no, re-execute the optimization command.

10. The prestressed zoning design method for thin-walled stacked box girder aqueducts according to claim 1, characterized in that, The construction parameters include the optimized three-dimensional spatial geometric coordinates of the steel strands, the prestressing control force data of the steel strands, and the allowable limit of construction deviation; the allowable limit of construction deviation is derived by reverse derivation based on the optimized robustness margin and the sensitivity matrix; the optimized robustness margin is the product of the optimized robustness index and the stress disturbance envelope value.

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