Bridge wind load effect analysis method based on finite element simulation

Abstract

The invention discloses a bridge wind load effect analysis method based on finite element simulation, and relates to the technical field of bridge wind engineering.The method comprises the following steps that firstly, wind speed parameters are calculated; step 2, wind load simulation; 3, establishing a large-span bridge finite element model; step 4, wind load effect analysis: static analysis and dynamic analysis; according to the method, by calculating the wind speed parameter, the actual wind condition of the bridge site area can be reflected more accurately, and reliable basic data are provided for wind load calculation; the wind load model is reasonably selected and the three-component coefficient is accurately calculated, so that the accuracy of wind load simulation is improved, and the interaction between the wind load and the bridge structure is more truly reflected; through detailed bridge finite element modeling and comprehensive wind load effect analysis, the mechanical behavior of the bridge structure under the wind load effect can be deeply known, and powerful support is provided for structural safety evaluation in the bridge design, construction and operation stages.

Description

Technical Field

[0001] The invention relates to the technical field of bridge wind engineering, and in particular to a bridge wind load effect analysis method based on finite element simulation. Background Art

[0002] As bridge spans continue to increase and structural forms become increasingly complex, wind loads have an increasingly significant impact on the safety and stability of bridge structures.

[0003] In the process of bridge design and construction, it is crucial to accurately analyze the wind load effect. Although the traditional wind tunnel test method can provide a certain reference, it has problems such as high cost, long cycle, and difficulty in fully ensuring model similarity. The finite element analysis method has broad application prospects in the field of bridge wind load effect analysis due to its advantages such as high efficiency, flexibility, and strong repeatability. However, the existing finite element-based analysis method still has some shortcomings in wind speed parameter determination, wind load simulation, structural modeling, and result analysis, which need to be further improved and perfected.

[0004] In view of this, a bridge wind load effect analysis method based on finite element simulation is provided to overcome the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a bridge wind load effect analysis method based on finite element simulation to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides a bridge wind load effect analysis method based on finite element simulation, comprising the following steps:

[0007] Step 1: Calculate wind speed parameters: determine basic wind speed, classify and determine surface roughness coefficient, and calculate design benchmark wind speed;

[0008] Step 2: Wind load simulation: wind load model selection, three-force coefficient calculation, wind load time history simulation;

[0009] Step 3: Establish a finite element model of a long-span bridge: determine material parameters, select structural units and simplify the model, and set boundary conditions;

[0010] Step 4: Analysis of wind load effects: static analysis and dynamic analysis.

[0011] Furthermore, in the basic wind speed determination step, bridges in coastal strong wind areas or canyon areas prefer to select a 100-year return period wind speed as the basic wind speed, while bridges in general inland areas generally select a 50-year return period wind speed.

[0012] Furthermore, when the surface roughness classification and coefficient are determined, complex terrain areas are analyzed by computational fluid dynamics (CFD).

[0013] Methods Numerical simulation was carried out and the surface roughness coefficient was corrected by combining the field measured wind profile data.

[0014] Furthermore, in the wind load model selection step, the dynamic wind load model includes a buffeting force model and a self-excited force model.

[0015] Furthermore, in the three-force coefficient calculation step, the three-force coefficient under different wind speeds, wind directions and angles of attack are calculated through numerical simulation, and the three-force coefficient curve within the full working range is obtained by using data fitting and interpolation methods. The calculated three-force coefficient is compared and verified with the wind tunnel test results or existing empirical data.

[0016] Furthermore, in the wind load time history simulation step, the wind speed spectrum includes but is not limited to the Davenport wind speed spectrum and the Simiu wind speed spectrum.

[0017] Furthermore, in the material parameter determination step, for concrete materials, the influence of its creep and shrinkage characteristics on the elastic modulus and Poisson's ratio is considered; for steel materials, the influence of corrosion on its yield strength and ultimate strength is considered.

[0018] Furthermore, in the steps of structural unit selection and model simplification, spring units are used to simulate the vertical and horizontal stiffness characteristics of plate rubber bearings, and the mass of the bridge deck pavement is equivalently distributed to the main beam units.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention can more accurately reflect the actual wind conditions in the bridge site area by calculating wind speed parameters, and provide reliable basic data for wind load calculation.

[0021] Reasonable selection of wind load model and accurate calculation of three-force coefficient improve the accuracy of wind load simulation and more realistically reflect the interaction between wind load and bridge structure.

[0022] Detailed bridge finite element modeling and comprehensive wind load effect analysis can provide in-depth understanding of the mechanical behavior of bridge structures under wind loads, and provide strong support for structural safety assessment during bridge design, construction and operation stages. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A bridge span arrangement diagram in a bridge wind load effect analysis method based on finite element simulation in the present invention;

[0024] Figure 2 It is a CFD method calculation domain and boundary condition diagram in a bridge wind load effect analysis method based on finite element simulation of the present invention;

[0025] Figure 3 It is a distribution curve diagram of three-force coefficients of key sections in a bridge wind load effect analysis method based on finite element simulation of the present invention;

[0026] Figure 4 A cross-sectional wind pressure cloud diagram in a bridge wind load effect analysis method based on finite element simulation according to the present invention;

[0027] Figure 5 A wind speed time history diagram of a simulation point in a bridge wind load effect analysis method based on finite element simulation according to the present invention;

[0028] Figure 6 It is a wind speed power spectrum fitting diagram in a bridge wind load effect analysis method based on finite element simulation of the present invention;

[0029] Figure 7 It is a Midas model diagram of the maximum cantilever stage in a bridge wind load effect analysis method based on finite element simulation of the present invention;

[0030] Figure 8 It is the transverse and vertical displacement diagram of each node of the main beam under three working conditions in the bridge wind load effect analysis method based on finite element simulation of the present invention;

[0031] Fig. 9 This is a schematic diagram of a bridge wind load effect analysis method based on finite element simulation according to the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-Figure 9 , the present invention provides a technical solution:

[0034] See also Figure 1 -

[0035] Fig. 9 As shown, an embodiment of a bridge wind load effect analysis method based on finite element simulation:

[0036] This method is based on the background of a super-high pier continuous rigid frame bridge planned to be built on a highway in Hubei Province. The static three-force coefficients of the key sections of the main beam and the pier are calculated based on the CFD method, and the wind load effect is analyzed at the most unfavorable stage (cantilever stage) of its wind load based on Midas / Civil, which can provide a reference for similar engineering projects.

[0037] Project Overview:

[0038] The supporting project is a continuous rigid frame bridge in a canyon area of ​​a highway in Hubei Province. The bridge site is located in Zigui County. The bridge spans across the canyon, and the bridge site is an asymmetric "V"-shaped canyon slope.

[0039] The bridge is a continuous rigid frame bridge with a span arrangement of 82m+2×148m+82m. The upper structure is a C55 prestressed concrete single-box single-chamber box girder section with vertical webs. Each span is 12.5m wide at the top and 6.5m wide at the bottom, with flanges on both sides 3m wide. The bottom plate is arranged with variable thickness, and the lower edge of the bottom plate changes in a second-order parabola. The lower structure is made of C40 concrete, which is a single-limb connected to a double-limb hollow thin-walled pier. The pier top is a double-limb hollow thin-walled pier, and the pier bottom is a single-limb hollow thin-walled pier. From left to right, they are 1# pier, 2# pier, and 3# pier, with pier heights of 96m, 180m, and 132m, respectively, which are super-high piers. The schematic diagram of the bridge elevation layout is shown below. Figure 1 shown.

[0040] 1. Calculation of wind speed parameters:

[0041] 1.1. Determination of basic wind speed: Collect meteorological observation data for many years in the bridge site area, including wind speed, wind direction, air pressure and other information. Use appropriate methods in extreme value theory (such as Gumbel distribution, Weibull distribution, etc.) to perform statistical analysis on wind speed data and determine wind speed values ​​with different return periods (such as 50 years, 100 years, etc.). Select wind speeds with a longer return period and that meet the actual local climate characteristics as basic wind speeds. For example, for bridges located in coastal strong wind areas or canyon areas, wind speeds with a return period of 100 years can be selected; for bridges in general inland areas, wind speeds with a return period of 50 years can be selected.

[0042] 1.2. Classification and coefficient determination of surface roughness: Conduct a detailed topographic survey of the bridge site, and divide the surface into different roughness categories (such as Class A for offshore sea surface, Class B for field and countryside, etc.) based on factors such as terrain undulation, vegetation coverage, and building distribution.

[0043]

[0044] The above table is a comparison table for surface roughness classification, involving classification standards in three different regions: China, Japan and Europe.

[0045] The main purpose of the above table is to help determine the roughness category of different regions under different surface conditions, which is very important for wind load related calculations. Because different surface roughness will affect the flow characteristics of wind near the ground, and then affect the size of wind loads acting on buildings (such as bridges). In projects involving wind load effect analysis such as bridge engineering, by clarifying the surface roughness category of the bridge site, wind loads can be calculated more accurately.

[0046] In the table: Category A:

[0047] China: including sea surface, coast, open water surface, desert and other surface types. These areas are relatively open and there are not many obstacles to hinder the flow of wind. The flow characteristics of wind in these areas are close to the ideal state.

[0048] Japan: Divided into "Ⅰ sea surface, lake" and "Ⅰ lake surface". Japan's classification distinguishes water bodies more finely, probably because there are some differences between sea surface and lake surface in terms of wind flow characteristics, but overall they are both relatively open water types.

[0049] Europe: Mainly "0 sea surface", which is also a classification of open surface types such as sea surface. This classification method may be related to relevant European standards or customs.

[0050] Category B:

[0051] China: covers fields, villages, jungles, flat open areas and areas with few low-rise buildings. These areas are characterized by a certain amount of vegetation cover or a small number of low-rise buildings, which have relatively little resistance to wind. The flow characteristics of wind in these areas are between open areas and areas with dense buildings.

[0052] Japan: "ⅠⅡ fields", which is similar to the field category in China, indicating that in the Japanese classification, fields are also considered to be a type of area with few buildings and relatively open space.

[0053] Europe: Also “ⅠⅡ fields”, which shows that in the European classification concept, the roughness characteristics of the field have a similar classification as those in China and Japan.

[0054] Category C:

[0055] China: including densely populated areas with trees and low-rise buildings, areas with sparsely populated medium and high-rise buildings, and gentle hills. There are relatively more obstacles in these areas, and the wind will be more disturbed when flowing through these areas, and its roughness characteristics are obviously different from those in open areas.

[0056] Japan: "III Suburbs", which reflects that Japan classifies suburbs, which have certain buildings and vegetation but not many medium and high-rise buildings, into this category. This means that from the perspective of wind load calculation, Japan believes that the roughness characteristics of suburbs are similar to those of China's Class C.

[0057] Europe: It is "III suburban". Similar to the suburbs of Japan, Europe also classifies suburban areas with similar distribution of buildings and vegetation as Class C, which means that they have similar characteristics in terms of wind flow characteristics.

[0058] Category D:

[0059] China: Including areas with densely packed medium and high-rise buildings and hilly areas with large undulations. The buildings and terrain in these areas have a very strong obstruction and interference effect on the wind, and the flow of wind in these areas will become very complicated.

[0060] Japan: It is divided into "IV cities" and "V large city centers". Japan has subdivided urban areas according to the density of buildings. The buildings in the centers of large cities are denser and the wind flow characteristics may be more complicated, so they are divided separately.

[0061] Europe: "IV urban area". The classification in Europe is not as detailed as that in Japan. Urban areas are uniformly classified as Class D. However, in actual applications, the characteristics of densely packed buildings and complex wind fields in urban areas can also be reflected.

[0062] In the wind load effect analysis method, surface roughness is a key factor. Through the detailed comparison of the surface roughness classifications in China, Japan and Europe in this table, the surface roughness category of the bridge site can be determined more accurately. It helps to accurately calculate the wind profile. For example, when calculating the change in wind speed at different heights, different surface roughness categories (such as open water surface of Class A and large urban center of Class D) will lead to very different wind profiles. According to the classification standards provided in the table, the appropriate roughness coefficient can be selected, thereby improving the accuracy of wind load calculation and making the wind load effect analysis results in the cantilever construction stage more reliable.

[0063] The above table covers the surface roughness classification of different countries, which is of great benefit for projects in different regions to carry out wind load effect analysis during the cantilever construction stage. If an engineering company carries out bridge cantilever construction projects in multiple countries, this cross-national comparison table can help them quickly adapt to the wind load analysis requirements of different countries. For example, when the project is located in Europe, the surface roughness coefficient can be determined by referring to the European classification standard; when constructing in Japan, the corresponding adjustment is made according to the Japanese classification. This allows the method to be flexibly applied in projects in different regions, enhancing the versatility of the method.

[0064] When perfecting the wind load effect analysis method, the table provides a window to understand the different international standards. Different countries may have more advanced or more suitable methods for certain special landforms in the classification of surface roughness. Through comparison, engineers can learn from the experience of other countries to improve their methods. For example, Japan's more detailed classification of urban areas (such as "IV city" and "V large city center") can inspire the consideration of more subtle wind environment differences when analyzing the wind load effect of urban bridge cantilever construction, further refine the analysis process, and make the method more scientific and reasonable.

[0065] The roughness coefficient of various types of surfaces is determined through field measurements or reference to relevant specifications. For complex terrain areas, such as mountainous canyon areas, the surface roughness coefficient is corrected by combining numerical simulation (such as computational fluid dynamics CFD method) or field measured wind profile data to more accurately reflect the actual wind field characteristics.

[0066] 1.3. Calculation of design benchmark wind speed: Based on the determined basic wind speed and surface roughness coefficient, the design benchmark wind speed at different heights of the bridge is calculated using the corresponding calculation formula (such as the formula in the highway bridge wind resistance design specification). Taking into account the different risk levels of the bridge during the construction and operation stages, the design benchmark wind speed during the construction period and the operation period are calculated separately, and appropriate safety factors are introduced for adjustment.

[0067] The design basic wind speed can be calculated according to formulas (1), (2) and (3):

[0068] U s10 =k c U 10 (1)

[0069] Where: k c

[0070] is the conversion coefficient of basic wind speed surface category, which is determined according to the surface type, and 0.785 is used for Class C surface. s10 =20.65m / s. 10

[0071] is the basic wind speed. The design reference wind speed at the bridge reference height Z can be calculated by formula (2):

[0072]

[0073] Where: Z is the reference height, the height of the bridge deck from the water surface or valley bottom, which can be determined according to the construction drawings. According to the construction drawings, Z = 155.33m; k f

[0074] is the wind risk coefficient. The bridge is located in the R2 wind risk area, and kf is taken as 1.02. The design reference wind speed of the main beam is calculated to be 38.5m / s, and the design reference wind speed of the pier is 38.97m / s. The design reference wind speed during the bridge construction stage can be calculated by formula (3):

[0075] U sd =k sf U d (3)

[0076] In the formula, k sf

[0077] is the wind risk coefficient during the construction period, which is determined by the construction period. The planned construction period of this bridge is 3 years, and the R2 risk zone. According to the specifications, the design benchmark wind speed during the main beam construction period is 32.35m / s, and the design benchmark wind speed during the pier construction period is 32.73m / s.

[0078] Wind risk factor k f

[0079] Risk Areas R1 R2 R3 <![CDATA[Basic wind speed U 10 > <![CDATA[U 10 >32.6]]> <![CDATA[24.5<U 10 <32.6]]> <![CDATA[U 10 ≦24.5]]> <![CDATA[Wind resistance risk coefficient k f > 1.05 1.02 1.00

[0080] The above table mainly focuses on the wind risk factor k f The risk area is divided into three categories: R1, R2, and R3. The basis for the division is the basic wind speed U 10 different ranges.

[0081] Risk area division and corresponding wind speed range:

[0082] R1 area: corresponding basic wind speed U 10 >32.6, which means that the area is usually in a strong wind environment and faces greater wind load challenges.

[0083] R2 area: basic wind speed range is 24.5 10 <32.6, the wind intensity is at a medium level, and the wind load impact is slightly smaller than that in R1 area.

[0084] R3 area: basic wind speed U 10 ≦24.5, the basic wind speed in this area is relatively low, and the impact of wind load on the structure is relatively minimal.

[0085] In different risk areas, the wind risk factor k f has different values. In the R1 region, k f The value is 1.05; in the R2 area, the value is 1.02; in the R3 area, the value is 1.00. The value of the coefficient reflects the difference in the requirements for the wind resistance performance of the structure under different wind environments. The greater the wind speed, the more it is required to consider the impact of wind load more fully by increasing the wind resistance risk coefficient to ensure the safety of the structure.​

[0086] The above table accurately considers the differences in wind environment: In the analysis of wind load effects during the cantilever construction phase, this table can be used to accurately determine the corresponding wind risk factor k based on the basic wind speed range in the area where the bridge is located. f For example, if the bridge is located in the R1 region where winds are stronger, a k value of 1.05 would be used. f The value can accurately reflect the impact of the local strong wind environment on the structure during the cantilever construction stage, making the wind load effect analysis more in line with the actual wind conditions.

[0087] Reasonable optimization of design parameters: according to different k f The value, combined with other relevant parameters (such as basic wind speed, surface roughness coefficient, etc.), can more scientifically and reasonably calculate key indicators such as the design benchmark wind speed during the operation period. This helps to optimize the structural design parameters of the bridge during the cantilever construction stage and the subsequent operation stage, avoid unreasonable designs caused by overestimation or underestimation of wind loads, and ensure the safety and economy of the structure under different wind environments.

[0088] Wind resistance risk factor k during construction period sf

[0089]

[0090] The above table focuses on the wind risk factor k during the construction period sf The value of is divided into two dimensions, namely the number of years of bridge construction (divided into ≤3 years and >3 years) and the risk area (also R1, R2, and R3).

[0091] Cross-classification of construction years and risk areas:

[0092] According to different risk areas and the length of construction years, detailed provisions are made for k sf For example, in the R1 risk area, when the construction years are ≤ 3 years, k sf The value is 0.88; when the construction years>3 years,

[0093] k sf The value becomes 0.84. Other R2 and R3 risk areas also have corresponding clear value settings. This reflects the quantitative consideration of the risk level of wind load during the construction period under the combined influence of construction time and the risk area. The longer the construction time and the stronger the wind in the risk area, the larger the corresponding coefficient, which means that more consideration should be given to the cumulative impact of wind load during the construction period.

[0094] During the cantilever construction stage, the stability of the structure is relatively fragile, and the impact of wind load cannot be ignored. Using the above table, we can accurately obtain the wind resistance risk factor k during the construction period based on the actual construction period of the bridge and the risk area where it is located. sf, and then more reasonably calculate the design reference wind speed during the construction period. For example, for a bridge with a planned construction period of 3 years and located in the R2 risk area, k can be determined. sf =0.84 to accurately assess the wind load risk during the construction period, which helps to take targeted wind protection measures during the construction process and ensure the safety of the cantilever construction stage.

[0095] Different bridge construction projects often have different construction periods and wind environments (risk areas). The above table allows this method to flexibly adapt to these differences. Regardless of the length of the project construction period and the changes in wind strength in the area, this table can accurately determine k sf The value can achieve a more accurate analysis of the wind load effect during the construction period, and improve the applicability and versatility of the analysis method in various construction projects.

[0096] 2. Wind load simulation:

[0097] 2.1. Wind load model selection: Select an appropriate wind load model based on the characteristics of the bridge structure and the wind conditions at the bridge site. For general bridge structures, commonly used static wind load models (such as average wind load models) can be used; for large-span flexible bridges or structures that are more sensitive to wind loads, consider using more accurate dynamic wind load models (such as buffeting force models, self-excitation force models, etc.). When selecting a dynamic wind load model, fully consider factors such as the turbulent characteristics of the wind, the aerodynamic shape of the structure, and the vibration characteristics of the structure to ensure that the model can accurately reflect the interaction between wind loads and structures.

[0098] 2.2. Calculation of three-force coefficients: Use the Midas / CFD module to calculate the three-force coefficients (drag coefficient, lift coefficient and torque coefficient) of the key sections of the bridge main beam and piers. Establish an accurate calculation model, including reasonable calculation domain settings, boundary condition definitions and meshing. Carry out detailed geometric modeling of the bridge structure, considering the roughness of the structural surface and the influence of auxiliary facilities (such as railings, access roads, etc.) on the airflow. Calculate the three-force coefficients under different wind speeds, wind directions and angles of attack through numerical simulation, and use data fitting or interpolation methods to obtain the three-force coefficient curves within the full range of working conditions. Compare and verify the calculated three-force coefficients with the wind tunnel test results or existing empirical data to ensure their accuracy.

[0099] 2.3. Wind load time history simulation: For the case of using a dynamic wind load model, a wind load time history simulation is performed. According to the wind speed spectrum of the bridge site (such as Davenport wind speed spectrum, Simiu wind speed spectrum, Kaimal spectrum, etc.) and the selected wind load model, the wind load time history samples are generated using random vibration theory or harmonic synthesis method. In the simulation process, the spatial correlation of wind speed is considered, and the correlation of wind speed at different locations is described by introducing a coherence function. Generate a sufficient number of wind load time history samples to ensure the statistical reliability of subsequent structural response analysis.

[0100] 3. Establish the finite element model of the long-span bridge:

[0101] 3.1. Determination of material parameters: Accurately determine the mechanical performance parameters of the materials used in the bridge structure, such as the elastic modulus, Poisson's ratio, and compressive strength of concrete, the elastic modulus, yield strength, and ultimate strength of steel, etc. Consider the performance changes of the material during long-term use (such as creep and shrinkage of concrete, corrosion of steel, etc.), and make appropriate corrections to the material parameters. For new materials or composite materials, determine the reasonable material parameter values ​​through experimental research or reference to relevant literature.

[0102] 3.2. Structural unit selection and model simplification: Select appropriate finite element units for modeling according to the type of bridge structure (such as beam bridge, arch bridge, cable-stayed bridge, suspension bridge, etc.). For the main beam structure, beam units or shell units can be used; for the pier and tower structure, beam units or solid units can be used. Under the premise of ensuring the accuracy of the analysis, the bridge structure is reasonably simplified, and the parts of the secondary structural components that have little effect on the mechanical properties of the overall structure are ignored. For example, for plate rubber bearings, spring units can be used to simulate their vertical and horizontal stiffness characteristics; for the bridge deck pavement layer, its mass can be equivalently distributed to the main beam unit.

[0103] 3.3. Boundary condition setting: According to the actual support conditions and constraints of the bridge, the boundary conditions of the finite element model are accurately set. For the bottom of the pier, its six degrees of freedom (three translational degrees of freedom and three rotational degrees of freedom) are constrained; for the connection between the main beam and the pier, the corresponding constraints are set according to the actual connection method of the structure (such as consolidation, hinge support, etc.). For long-span bridges, the influence of factors such as temperature changes and foundation settlement on the boundary conditions is considered, and appropriate methods (such as setting spring units to simulate foundation flexibility, etc.) are used for simulation.

[0104] 4. Analysis of wind load effect:

[0105] 4.1. Static analysis: The calculated static wind load (or average wind load) is applied to the bridge finite element model in the form of node force or unit load for static analysis. There are three working conditions:

[0106] Working condition 1:

[0107] Loading method: The calculated static wind load (or average wind load) is applied to the left and right ends of the upper structure of the bridge finite element model in the form of node force or unit load at a ratio of 1:1, that is, the loads applied to the left and right ends are equal in magnitude and direction. For example, if the static wind loads acting on the left and right ends of the cantilever structure are set to FJ1 and FJ2 respectively, then FJ1 / FJ2=1.

[0108] Consider load types: Wind loads need to consider the forces generated by resistance, lift, torque, etc. For the piers, only the resistance load type is considered.

[0109] Analysis content: Under this working condition, calculate the displacement of the bridge structure under the static wind load, as well as the internal force (including axial force, shear force, bending moment) and stress distribution. By analyzing the static response of the structure under different wind direction angles, wind speeds and other conditions, determine the most unfavorable stress state of the structure under this proportional loading of the same static wind load, and finally compare it with the allowable value in the structural design code to evaluate the safety of the structure under the static wind load of this working condition.

[0110] Working condition 2:

[0111] Loading method: The static wind load (or average wind load) is also applied to the bridge finite element model in the form of node force or unit load, but an asymmetric load is applied to the left and right ends of the superstructure in a ratio of 1:0.5, that is, the loads on the left and right ends are different. The static wind loads acting on the left and right ends of the cantilever structure are set to FJ3 and FJ4 respectively, then FJ3 / FJ4=2, presenting an asymmetric loading situation.

[0112] Consider the load type: Wind loads also consider drag, lift, and torque, while only the drag load type is considered on bridge piers.

[0113] Analysis content: Calculate the displacement, internal force (axial force, shear force, bending moment) and stress distribution of the bridge structure under this asymmetric static wind load condition. Analyze the static response of the structure under different wind direction angles, wind speeds, etc. to find the most unfavorable stress state of the structure under this asymmetric loading condition, and then compare the relevant results with the allowable values ​​of the structural design code to evaluate the safety of the structure under the static wind load of this condition.

[0114] Condition 3:

[0115] Loading method: The static wind load (or average wind load) is applied to the left and right ends of the superstructure of the bridge finite element model in the form of node force or unit load, and the load is applied in a ratio of 1:-1, that is, the loads applied on the left and right ends are equal but opposite in direction. Assuming that the static wind loads acting on the left and right ends of the cantilever structure are FJ5 and FJ6 respectively, then FJ5 / FJ6=-1, simulating the load effect under similar special circumstances (such as sudden change in wind direction, which may lead to reverse force).

[0116] Consider load types: The wind load on the main beam needs to consider resistance, lift, and torque, while the wind load on the pier still only considers resistance.

[0117] Analysis content: Calculate the displacement, internal force (axial force, shear force, bending moment) and stress distribution of the bridge structure when the static wind load is loaded in this special proportion, analyze the static response of the structure under the influence of factors such as different wind directions and wind speeds, determine the most unfavorable stress state of the structure under this special condition, and evaluate the safety of the structure under this special static wind load condition by comparing it with the allowable values ​​in the structural design specifications.

[0118] Calculate the displacement, internal force (axial force, shear force, bending moment) and stress distribution of the bridge structure under static wind load. Analyze the static response of the structure under different wind load conditions (such as different wind direction angles, wind speeds, etc.) to determine the most unfavorable stress state of the structure. Evaluate the safety of the structure under static wind load by comparing with the allowable values ​​in the structural design specifications.

[0119] 4.2. Dynamic analysis: For the case of considering dynamic wind loads, the generated wind load time history samples are applied to the finite element model for dynamic time history analysis. The dynamic response of the bridge structure under wind loads is calculated, including displacement time history, acceleration time history, internal force time history, etc. The natural vibration characteristics of the structure (such as natural frequency and vibration mode) are analyzed, and the main vibration modes of the structure and their corresponding frequencies are determined through modal analysis. The dynamic response indicators of the structure are calculated, such as the root mean square value of displacement, the root mean square value of acceleration, and the stress amplitude. According to the fatigue performance requirements of the structure, an appropriate fatigue analysis method (such as the linear cumulative damage theory) is used to evaluate the fatigue life of the structure under wind loads.

[0120] 5. Summary:

[0121] The present invention can more accurately reflect the actual wind conditions in the bridge site area by calculating wind speed parameters, and provide reliable basic data for wind load calculation.

[0122] Reasonable selection of wind load model and accurate calculation of three-force coefficient improve the accuracy of wind load simulation and more realistically reflect the interaction between wind load and bridge structure.

[0123] Detailed bridge finite element modeling and comprehensive wind load effect analysis can provide in-depth understanding of the mechanical behavior of bridge structures under wind loads, and provide strong support for structural safety assessment during bridge design, construction and operation stages.

Claims

1. A bridge wind load effect analysis method based on finite element simulation, characterized in that: The following steps are involved: Step 1: Calculate wind speed parameters: determine basic wind speed, classify and determine surface roughness coefficient, and calculate design benchmark wind speed; Step 2: Wind load simulation: wind load model selection, three-force coefficient calculation, wind load time history simulation; Step 3: Establish a finite element model of a long-span bridge: determine material parameters, select structural units and simplify the model, and set boundary conditions; Step 4: Analysis of wind load effects: static analysis and dynamic analysis.

2. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the basic wind speed determination step, for bridges located in coastal strong wind areas or canyon areas, wind speeds with a return period of 100 years are preferably selected as the basic wind speed; for bridges in general inland areas, wind speeds with a return period of 50 years are selected as the basic wind speed.

3. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the surface roughness classification and coefficient determination steps, for complex terrain areas, the surface roughness coefficient is corrected by combining numerical simulation with on-site measured wind profile data. The numerical simulation uses the computational fluid dynamics (CFD) method.

4. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the wind load model selection step, the dynamic wind load model includes a buffeting force model and a self-excited force model.

5. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the three-force coefficient calculation step, the three-force coefficient under different wind speeds, wind directions and angles of attack are calculated through numerical simulation, and the three-force coefficient curve within the full working range is obtained by using data fitting and interpolation methods. The calculated three-force coefficient is compared and verified with the wind tunnel test results or existing empirical data.

6. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the wind load time history simulation step, the wind speed spectrum includes but is not limited to the Davenport wind speed spectrum and the Simiu wind speed spectrum.

7. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the material parameter determination step, for concrete materials, the influence of its creep and shrinkage characteristics on the elastic modulus and Poisson's ratio is considered; for steel, the influence of corrosion on its yield strength and ultimate strength is considered.

8. The method for analyzing wind load effects on bridges based on finite element simulation according to claim 1, characterized in that: In the steps of structural unit selection and model simplification, spring units are used to simulate the vertical and horizontal stiffness characteristics of plate rubber bearings, and the mass of the bridge deck pavement is equivalently distributed to the main beam units.

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