A method for analyzing cracking of a mid-span continuous rigid frame bridge based on a CDP model

Abstract

The application discloses a kind of based on CDP model's open-web continuous rigid frame bridge cracking analysis method, utilize open-web continuous rigid frame bridge integral finite element model, the influence of temperature action, prestress loss, shrinkage and creep and initial defect possibly existing in construction process to bridge structure internal force is comprehensively considered, find the adverse beam section of the bridge type existing cracking trend.Simultaneously, based on damage mechanics theory, through MATLAB platform, computer program is written, and the damage factor in CDP model is calculated by energy loss method, and the remaining damage parameters are obtained according to the selected stress-strain curve.Finally, the local model of the adverse beam section is established, and the internal force boundary under the adverse working condition in the overall model is used to simulate the generation and expansion of cracks in the beam section, and the law is obtained.It is of great significance to its design, construction and later maintenance, and can better ensure the normal and safe operation of open-web continuous rigid frame bridge.

Description

Technical Field

[0001] This invention belongs to the field of bridge structural safety, specifically relating to a crack analysis method for large-span prestressed concrete cantilevered open web continuous rigid frame bridges based on the CDP model. Background Technology

[0002] The hollow-web continuous rigid frame bridge is a new bridge type innovatively designed based on the continuous rigid frame bridge and incorporating the stress characteristics of arch bridges. This bridge type meets my country's demand for bridges with economical spans of 200m to 400m. The hollow-web continuous rigid frame bridge removes the web at the root of the end box girder, creating a hollow area. The box girder near the main pier is divided into upper chord and lower chord segments. The lower chord segment mainly bears the compressive stress, fully utilizing the high compressive strength of concrete. This structural form reduces the structure's self-weight, optimizes stress distribution, and increases the span.

[0003] This bridge type is relatively new, and there are not many open-web continuous rigid frame bridges that have been built. Some scholars have studied the structural parameter optimization design, stress characteristics during construction, seismic resistance, and stress state of the upper and lower chord joints of this bridge type, but there is little research on the influencing factors of cracking in open-web continuous rigid frame bridges and the laws governing crack generation and propagation.

[0004] The structural form and stress characteristics of hollow continuous rigid frame bridges are different from those of conventional continuous rigid frame bridges. The crack-related laws of continuous rigid frame bridges cannot be simply applied to hollow continuous rigid frame bridges. Therefore, it is of great practical significance to study the influencing factors that may cause cracking in this type of bridge. Considering the possible initial defects, and based on the theory of damage mechanics, the concrete plastic damage model is used to study the generation and propagation of cracks in unfavorable beam segments. Summary of the Invention

[0005] The purpose of this invention is to study the generation and propagation of cracks in beam segments that may crack under the combined effects of various factors that may lead to cracking in open-web continuous rigid frame bridges and their possible initial defects. Based on damage mechanics theory, the concrete plastic damage model (CDP) is used to study these cracks.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for analyzing cracks in long-span prestressed concrete cantilevered continuous rigid frame bridges based on the CDP model, comprising the following steps:

[0007] 1. For a hollow continuous rigid frame bridge, a full-bridge model was established using finite element method (FEM) software. Taking into account factors such as temperature effects, prestress loss, shrinkage and creep effects, and potential initial defects, the model was modified to reflect the influence of each factor on the overall bridge structure stress. Based on the specifications, load cases were determined, and the most unfavorable case (the one with the highest first principal stress) was identified. The beam segments with a tendency to crack were determined based on the calculation results.

[0008] 2. Based on damage mechanics theory, four undetermined damage parameters need to be obtained from the CDP model of the C55 grade concrete used in the main beam: stress value, inelastic strain, cracking strain, and damage factor. The stress value, inelastic strain, and cracking strain are calculated by inputting the formulas into an Excel spreadsheet based on the selected stress-strain curve. The damage factor is the most important damage parameter. Using the MATLAB platform and based on the energy loss method, a computer program is developed to obtain the damage factor of C55 grade concrete under tension and compression, and the relationship between the damage factor and strain under tension and compression of C55 grade concrete.

[0009] 3. For beam segments in open-web continuous rigid frame bridges that may exhibit cracking tendencies, according to Saint-Venant's principle, in order to utilize the stress boundary in the overall model, the established local model needs to extend its scope to within several meters of the beam segment exhibiting cracking tendencies. A geometric model is created using Revit software, then imported into Hypermesh software to create element meshes. The geometric model is then converted into a solid model, and finally imported as components into the finite element analysis software ABAQUS to complete the establishment of the local model.

[0010] 4. Extract the axial force, shear force, and bending moment of each unfavorable beam segment under the most unfavorable working condition, where the principal tensile stress is greatest, from the full bridge model; these are the stress boundaries. Apply the extracted stress boundaries to the local model and add the loads on the local beam segments themselves to simulate the stress conditions of those segments under the most unfavorable working condition. Using the previously calculated damage parameters, simulate the generation and propagation of cracks in the unfavorable beam segments using the CDP model. Analyze the finite element calculation results to obtain the generation and propagation laws of concrete cracks in the open-web continuous rigid frame bridge.

[0011] The specific steps are as follows:

[0012] S1. A complete model of a hollow continuous rigid frame bridge was established using Midas software, and the unfavorable beam segments that may have a cracking tendency under the combined effect of various factors were identified through the overall model:

[0013] S11. The load combination under the normal serviceability limit state of the open-web continuous rigid frame bridge is determined according to the "Design Specification for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" JTG 3362-2018. Subsequently, the above load conditions are used to calculate the entire bridge model, and the unfavorable beam segments are analyzed based on the stress conditions.

[0014] S12. Considering the adverse effects during the construction and operation phases, the impact of prestress loss is first reflected by modifying the pipe wall friction coefficient μ and the influence coefficient k of pipe deviation on friction in the model. Based on extensive measured data of prestress friction loss in China, μ = 0.95 and k = 0.0095 are selected. Secondly, to reflect the effect of temperature, temperature data at the bridge site are consulted, and the overall temperature effect is determined to be a temperature increase of 28℃ and a temperature decrease of 20℃. In addition, to reflect the effect of shrinkage and creep, the stress state of the bridge 20 years after completion is considered. The hydration heat effect of large-volume concrete is significant, leading to temperature cracks. This defect is considered at two locations with large concrete volumes: the top zero block of the pier and the junction of the upper and lower chords. This is addressed by reducing the stiffness at these locations.

[0015] S13. Check the output results of the Midas Civil software and analyze the first principal stress (principal tensile stress) at each position of the main beam. It is found that the first principal stress at the bottom end of the mid-span beam segment reaches about 2.8 MPa when the load combination is load case 3, which exceeds the standard axial tensile strength of C55 grade concrete of 2.74 MPa. The concrete will crack. That is, the mid-span beam segment is an unfavorable beam segment that needs attention in open web continuous rigid frame bridges.

[0016] S2. Based on damage mechanics theory, the tensile and compressive stress-strain curves of concrete in the specifications are selected, and the curves are modified to meet the requirements of the CDP model. A computer program is developed using the MATLAB platform to calculate the damage factor using the energy loss method. Other damage parameters are calculated using Excel spreadsheets. The various damage parameters of the CDP model for C55 grade concrete are obtained as follows:

[0017] S21. The selection of the constitutive relation for concrete is a crucial step in numerical analysis using the CDP model. Typically, the stress-strain curve from the "Code for Design of Concrete Structures" GB 50010-2010 is chosen. However, due to differences in the ascending segment of the stress-strain curve between the current code and the CDP model, the standard stress-strain curve cannot be directly used to determine the CDP model; it needs to be modified. The following adjustments can be made: Under tension, the ascending segment of the stress-strain curve should be the straight line segment from the origin to the peak stress point, and the descending segment should be the curve segment given in the code. Under compression, the yield point in the ascending segment of the stress-strain curve should be selected to modify the standard curve; the compressive yield point should be 0.6 times the ultimate stress σ. cu The ascending and descending segments of the curve after this point are selected from the curve segments given in the specification.

[0018] S22. Among the damage parameters, the damage factor D has the greatest impact on the accuracy of numerical simulation results. The energy loss method can be used to calculate the damage factor. The energy loss method considers the damage factor D to be equal to the ratio of the difference in strain energy density when considering no loss of elastic modulus versus when considering loss of elastic modulus, to the strain energy density when considering no loss of elastic modulus. Since the slope of the stress-strain curve considering loss of elastic modulus changes continuously, a computer program is needed to obtain the strain energy density under this condition. Based on the stress-strain curve in the specification, the curve correction mentioned above, and the mechanical property parameters of C55 grade concrete, the curve is determined. A computer program written on the MATLAB platform integrates the curve to obtain the strain energy density considering loss of elastic modulus. Then, the corresponding difference and ratio are calculated to obtain the damage factor. The remaining damage parameters can be calculated using formulas written in Excel.

[0019] S23, Calculated damage parameters for C55 grade concrete.

[0020] S3. Establish a local model for the unfavorable beam segment of the identified open-web continuous rigid frame bridge, namely the mid-span beam segment, as the basis for subsequent local crack analysis:

[0021] S31. Based on the design drawings of the beam segments, a geometric model was created in Revit software according to the corresponding dimensions. Since stress boundary conditions need to be applied according to Saint-Venant's principle, the geometric model ranged from segment 31 to segment 33. S32. The created geometric model was imported into Hypermesh meshing software. Finite element meshing was performed on the geometric model. To ensure computational efficiency and accuracy, most elements were divided into hexahedral elements. After meshing, the conversion from geometric model to solid model was completed, containing 93,180 elements. The solid model was then imported into ABAQUS finite element analysis software as a component.

[0022] S4. Apply the stress boundary from the overall model to the local model, and use the previously calculated damage parameters to set up the CDP model for the local model. Perform finite element simulation to obtain the calculation results. Analyze the calculation results to obtain the generation and propagation law of concrete cracks in the open-web continuous rigid frame bridge:

[0023] S41. Read the stress calculation results of the overall model under load combination of condition 3 in the Midas software, and the internal force results on the boundary of the local model. According to the beam segment design drawings, obtain the centroids of the two boundary sections through CAD software, establish reference points at the centroids, add the internal forces in the table above to the reference points, and then apply the load on the beam segment itself to the local model to simulate the stress state of the local model in the whole bridge model.

[0024] S42. First, set the concrete material as an elastic material, adding the elastic modulus, Poisson's ratio, and density, i.e., without using the CDP model, and compare the calculation results of the local model with those of the global model. The first principal stress at the bottom end of the mid-span beam segment in the local model is 3.0 MPa, which is not much different from 2.8 MPa in the global model. The error is within an acceptable range, indicating that this modeling method can accurately and effectively simulate the local area.

[0025] S43. Add concrete plastic damage to the solid model material and use the previously obtained C55 grade concrete damage parameters, i.e., use the CDP model to perform finite element simulation on the local model of the mid-span beam segment. By examining the changes in the tensile damage factor in the results, it can be found that tensile damage first appears on the bottom outer surface of the middle position of the mid-span beam segment, indicating that cracking occurs first at this location. The cracks develop laterally, and multiple transverse cracks appear in the bottom slab. At the same time, after the transverse cracks in the bottom slab develop, they show a tendency to extend towards the web. Transverse cracks also appear in the bottom slab inside the box girder, and longer cracks extend towards the inner wall of the web. This crack type is a typical transverse crack caused by longitudinal normal stress in the bottom slab near the mid-span.

[0026] The technical advantages of this invention are as follows: By utilizing a finite element model of a hollow continuous rigid frame bridge, and comprehensively considering the effects of temperature, prestress loss, shrinkage and creep, and potential initial defects during construction on the internal forces of the bridge structure, the unfavorable beam segments with a tendency to crack are identified. Simultaneously, based on damage mechanics theory, a computer program is written using the MATLAB platform to calculate the damage factors in the CDP model using the energy loss method, and other damage parameters are obtained based on the selected stress-strain curve. Finally, a local model of the unfavorable beam segment is established, and the internal force boundary under unfavorable conditions in the overall model is used to simulate the generation and propagation of cracks in this beam segment, revealing its patterns. This is of great significance for the design, construction, and subsequent maintenance of hollow continuous rigid frame bridges, and can better ensure the normal and safe operation of such bridges. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the finite element model of the entire bridge.

[0028] Figure 2 This is a schematic diagram showing the relationship between the damage factor and strain of C55 grade concrete under tension.

[0029] Figure 3 This is a schematic diagram showing the relationship between the damage factor and strain of C55 grade concrete under compression.

[0030] Figure 4 This is a schematic diagram of a local model of an unfavorable beam segment.

[0031] Figure 5 This is a schematic diagram illustrating the formation of cracks in an unfavorable beam segment. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to examples. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0033] This invention includes the following steps:

[0034] S1, such as Figure 1 As shown, a complete bridge model was established using Midas software for a certain open-web continuous rigid frame bridge, and the unfavorable beam segments that may have a cracking tendency under the combined effect of various factors were identified through the overall model:

[0035] S11. According to the "Design Specification for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" JTG 3362-2018, the load combination under the normal service limit state of the open-web continuous rigid frame bridge is determined, and the load conditions are shown in Table 1.

[0036] Table 1 Load Cases

[0037]

[0038] The above-mentioned load conditions were then used to calculate the entire bridge model, and the unfavorable beam segments were analyzed based on the stress conditions.

[0039] S12. Considering the adverse effects during the construction and operation phases, the impact of prestress loss is first reflected by modifying the pipe wall friction coefficient μ and the influence coefficient k of pipe deviation on friction in the model. Based on extensive measured data of prestress friction loss in China, μ = 0.95 and k = 0.0095 are selected. Secondly, to reflect the effect of temperature, temperature data at the bridge site are consulted, and the overall temperature effect is determined to be a temperature increase of 28℃ and a temperature decrease of 20℃. In addition, to reflect the effect of shrinkage and creep, the stress state of the bridge 20 years after completion is considered. The hydration heat effect of large-volume concrete is significant, leading to temperature cracks. This defect is considered at two locations with large concrete volumes: the top zero block of the pier and the junction of the upper and lower chords. This is addressed by reducing the stiffness at these locations.

[0040] S13. Check the output results of the Midas Civil software and analyze the first principal stress (principal tensile stress) at each position of the main beam. It is found that the first principal stress at the bottom end of the mid-span beam segment reaches about 2.8 MPa when the load combination is load case 3, which exceeds the standard axial tensile strength of C55 grade concrete of 2.74 MPa. The concrete will crack. That is, the mid-span beam segment is an unfavorable beam segment that needs attention in open web continuous rigid frame bridges.

[0041] S2, such as Figure 2 and Figure 3 As shown, based on damage mechanics theory, the tensile and compressive stress-strain curves of concrete in the specifications are selected, and the curves are modified to meet the requirements of the CDP model. A computer program is developed using the MATLAB platform to calculate the damage factor using the energy loss method. Other damage parameters are calculated using Excel spreadsheets. The various damage parameters of the CDP model for C55 grade concrete are obtained as follows:

[0042] S21. The selection of the constitutive relation for concrete is a crucial step in numerical analysis using the CDP model. Typically, the stress-strain curve from the "Code for Design of Concrete Structures" GB 50010-2010 is chosen. However, due to differences in the ascending segment of the stress-strain curve between the current code and the CDP model, the standard stress-strain curve cannot be directly used to determine the CDP model; it needs to be modified. The following adjustments can be made: Under tension, the ascending segment of the stress-strain curve should be the straight line segment from the origin to the peak stress point, and the descending segment should be the curve segment given in the code. Under compression, the yield point in the ascending segment of the stress-strain curve should be selected to modify the standard curve; the compressive yield point should be 0.6 times the ultimate stress σ. cu The ascending and descending segments of the curve after this point are selected from the curve segments given in the specification.

[0043] S22. Among the damage parameters, the damage factor D has the greatest impact on the accuracy of numerical simulation results. The energy loss method can be used to calculate the damage factor. The energy loss method considers the damage factor D to be equal to the ratio of the difference in strain energy density when considering no loss of elastic modulus versus when considering loss of elastic modulus, to the strain energy density when considering no loss of elastic modulus. Since the slope of the stress-strain curve considering loss of elastic modulus changes continuously, a computer program is needed to obtain the strain energy density under this condition. Based on the stress-strain curve in the specification, the curve correction mentioned above, and the mechanical property parameters of C55 grade concrete, the curve is determined. A computer program written on the MATLAB platform integrates the curve to obtain the strain energy density considering loss of elastic modulus. Then, the corresponding difference and ratio are calculated to obtain the damage factor. The remaining damage parameters can be calculated using formulas written in Excel.

[0044] S23. The calculated damage parameters of C55 grade concrete are shown in Table 2 below.

[0045] Table 2 Damage parameters of C55 grade concrete under tension and compression.

[0046]

[0047]

[0048] S3, such as Figure 4 As shown, a local model is established for the unfavorable beam segment of the hollow continuous rigid frame bridge, namely the mid-span beam segment, as the basis for subsequent local crack analysis:

[0049] S31. Based on the design drawings of the beam segments, a geometric model was created in Revit software according to the corresponding dimensions. Since stress boundary conditions need to be applied according to Saint-Venant's principle, the geometric model ranged from segment 31 to segment 33. S32. The created geometric model was imported into Hypermesh meshing software. Finite element meshing was performed on the geometric model. To ensure computational efficiency and accuracy, most elements were divided into hexahedral elements. After meshing, the conversion from geometric model to solid model was completed, containing 93,180 elements. The solid model was then imported into ABAQUS finite element analysis software as a component.

[0050] S4, such as Figure 5 As shown, the stress boundary in the overall model is applied to the local model, and the CDP model is set up for the local model using the previously calculated damage parameters. Finite element simulation is performed to obtain the calculation results. The calculation results are analyzed to obtain the generation and propagation law of concrete cracks in the open-web continuous rigid frame bridge:

[0051] S41. Read the stress calculation results of the overall model load combination in the Midas software under the condition of working case 3. The internal force results on the boundary of the local model are shown in Table 3.

[0052] Table 3 Internal Force Results of Mid-Span Beam Segment

[0053]

[0054]

[0055] Based on the beam segment design drawings, the centroids of the two boundary sections are obtained through CAD software. Reference points are established at the centroids, and the internal forces in the table above are added to the reference points. Then, the loads on the beam segment itself are applied to the local model, which can simulate the stress state of the local model in the full bridge model.

[0056] S42. First, set the concrete material as an elastic material, adding the elastic modulus, Poisson's ratio, and density, i.e., without using the CDP model, and compare the calculation results of the local model with those of the global model. The first principal stress at the bottom end of the mid-span beam segment in the local model is 3.0 MPa, which is not much different from 2.8 MPa in the global model. The error is within an acceptable range, indicating that this modeling method can accurately and effectively simulate the local area.

[0057] S43. Add concrete plastic damage to the solid model material and use the previously obtained C55 grade concrete damage parameters, i.e., use the CDP model to perform finite element simulation on the local model of the mid-span beam segment. By examining the changes in the tensile damage factor in the results, it can be found that tensile damage first appears on the bottom outer surface of the middle position of the mid-span beam segment, indicating that cracking occurs first at this location. The cracks develop laterally, and multiple transverse cracks appear in the bottom slab. At the same time, after the transverse cracks in the bottom slab develop, they show a tendency to extend towards the web. Transverse cracks also appear in the bottom slab inside the box girder, and longer cracks extend towards the inner wall of the web. This crack type is a typical transverse crack caused by longitudinal normal stress in the bottom slab near the mid-span.

[0058] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A crack analysis method for hollow continuous rigid frame bridges based on the CDP model, characterized in that, Includes the following steps:

1. For a certain open-web continuous rigid frame bridge, a full bridge model is established using finite element software. Taking into account the effects of temperature, prestress loss, shrinkage and creep, and possible initial defects on the stress of the entire bridge structure, the values ​​of various influencing factors in the overall model are reasonably modified to reflect the effect of each influencing factor on the stress of the entire bridge structure. The load conditions are determined according to the specifications, and the most unfavorable load condition is found among the load conditions, that is, the load condition with the largest first principal stress. Based on the calculation results, the beam segments of the bridge with the tendency to crack are determined. Second, based on the theory of damage mechanics, it is necessary to obtain four undetermined damage parameters in the CDP model of the C55 grade concrete used in the main beam: stress value, inelastic strain, cracking strain and damage factor. The stress value, inelastic strain, and crack strain are obtained by inputting the calculation formula into an Excel spreadsheet based on the selected stress-strain curve; Damage factor is the most important damage parameter. Using the MATLAB platform and based on the energy loss method, a computer program was developed to obtain the damage factor of C55 grade concrete under tension and compression, and the relationship between the damage factor and strain under tension and compression of C55 grade concrete. Third, for beam segments in open-web continuous rigid frame bridges that may have a tendency to crack, according to Saint-Venant's principle, in order to use the stress boundary in the overall model, the local model needs to be expanded to a few meters around the beam segment with a cracking tendency. The geometric model is created using Revit software, then imported into Hypermesh software to draw the element mesh, the geometric model is converted into a solid model, and the solid model is imported into the finite element analysis software ABAQUS in the form of components to complete the establishment of the local model. Fourth, extract the axial force, shear force, and bending moment of each unfavorable beam segment under the most unfavorable working condition with the largest principal tensile stress from the full bridge model, i.e., the stress boundary; apply the extracted stress boundary to the local model and add the load on the local beam segment itself to simulate the stress situation of the local beam segment under the most unfavorable working condition; use the damage parameters obtained earlier to simulate the generation and propagation of cracks in the unfavorable beam segment using the CDP model; analyze the finite element calculation results to obtain the generation and propagation law of concrete cracks in the open-web continuous rigid frame bridge; The specific steps are as follows: S1. A complete model of a hollow continuous rigid frame bridge was established using Midas software, and the unfavorable beam segments that may have a cracking tendency under the combined effect of various factors were identified through the overall model: S11. The load combination under the normal service limit state of the open-web continuous rigid frame bridge is determined according to the "Design Specification for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" JTG 3362-2018. Subsequently, the above load combination is used to calculate the whole bridge model, and the unfavorable beam segment is analyzed according to the stress situation. S12. Considering the adverse effects during the construction and operation phases, the first step is to modify the pipe wall friction coefficient in the model. The influence coefficient of pipe deviation on friction To reflect the impact of prestress loss, select =0.95、 =0.0095; Secondly, the values ​​for the overall temperature effect were determined to be a temperature increase of 28℃ and a temperature decrease of 20℃; S13. Check the output results of the Midas Civil software, analyze the first principal stress, i.e. the principal tensile stress, at each position of the main beam, and obtain the working condition that the concrete in the mid-span beam segment will crack. S2. Based on damage mechanics theory, the tensile and compressive stress-strain curves of concrete in the specifications are selected, and the curves are modified to meet the requirements of the CDP model. A computer program is developed using the MATLAB platform to calculate the damage factor using the energy loss method. Other damage parameters are calculated using Excel spreadsheets. The various damage parameters of the CDP model for C55 grade concrete are obtained as follows: S21. The constitutive relation of concrete is selected from the stress-strain curve in the "Code for Design of Concrete Structures" GB 50010-2010; The stress-strain curves in the standard are corrected as follows: Under tension, the rising segment of the stress-strain curve is taken as the straight line segment from the origin to the peak stress point, and the falling segment is selected from the curve segment given in the standard; under compression, the yield point should be selected in the rising segment of the stress-strain curve to correct the curve given in the standard, and the compressive yield point is selected as 0.6 times the ultimate stress. The ascending and descending segments of the curve after this point are selected from the curve segments given in the specification. S22. Among the damage parameters, the damage factor D has the greatest impact on the accuracy of the numerical simulation results. The energy loss method is used to calculate the damage factor. The curve is determined based on the stress-strain curve in the specification, the correction of the curve, and the mechanical property parameters of C55 grade concrete. The strain energy density considering the loss of elastic modulus can be obtained by integrating the curve using a computer program written on the MATLAB platform. Then, the corresponding difference and ratio are calculated to obtain the damage factor. The remaining damage parameters are calculated by writing calculation formulas in an Excel spreadsheet. S23. Calculated damage parameters for C55 grade concrete; S3. Establish a local model for the unfavorable beam segment of the hollow continuous rigid frame bridge, namely the mid-span beam segment, as the basis for subsequent local crack analysis. S31. Based on the design drawings of the beam segment, apply stress boundary conditions according to Saint-Venant's principle, and establish a geometric model with corresponding dimensions in Revit software; S32. Import the established geometric model into the Hypermesh meshing software in geometric form. Perform finite element meshing on the geometric model. To ensure the efficiency and accuracy of the calculation, most elements are divided into hexahedral elements. After meshing, the conversion from geometric model to solid model is completed, containing 93,180 elements. Import the solid model into the ABAQUS finite element analysis software in the form of a component. S4. Apply the stress boundary from the overall model to the local model, and use the previously calculated damage parameters to set up the CDP model for the local model. Perform finite element simulation to obtain the calculation results. Analyze the calculation results to obtain the generation and propagation law of concrete cracks in the open-web continuous rigid frame bridge: S41. Read the stress calculation results of the overall model load combination in the Midas software under the working condition described in S13, and the internal force results on the boundary of the local model; according to the beam segment design drawings, obtain the centroid of the two boundary sections through CAD software, establish a reference point at the centroid, add the internal forces in the table above to the reference point, and then apply the load on the beam segment itself to the local model to simulate the stress state of the local model in the whole bridge model; S42. First, set the concrete material as an elastic material and add the elastic modulus, Poisson's ratio, and density. That is, do not use the CDP model. Compare the calculation results of the local model with the calculation results of the overall model. S43. Add concrete plastic damage to the solid model material and use the previously obtained C55 grade concrete damage parameters. That is, use the CDP model to perform finite element simulation on the local model of the mid-span beam segment. Check the changes in the tensile damage factor in the results.

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