A method for calculating the service life of fatigue details at the intersection of longitudinal ribs and cross diaphragms of orthotropic steel bridge decks

Abstract

The application discloses a kind of orthotropic steel bridge deck longitudinal rib and transverse diaphragm intersection place fatigue details service life calculation method, comprising the following steps: S1: investigation and research target bridge the history of the road section where the vehicle is driven, and the average daily heavy vehicle type and the number of times of different types of heavy vehicle to orthotropic steel bridge deck are counted;S2: find the most unfavorable load distribution position when wheel load corresponding to axle load acts on orthotropic steel bridge deck, obtain the peak stress σ1 at the target fatigue detail structure when wheel load corresponding to axle load acts on the most unfavorable load distribution position;S3: obtain the maximum residual stress σ2 on the weld path of the intersection of orthotropic steel bridge deck longitudinal rib and transverse diaphragm;S4: calculate the service life of target fatigue detail.The application based on the S-N curve of base material, the stress generated under axle and welding residual stress are regarded as external load, and the fatigue performance of the detail can be well evaluated.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology in the transportation industry, specifically relating to a method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks. Background Technology

[0002] Orthotropic steel bridge decks possess outstanding advantages such as lightweight and high strength, good applicability, ease of factory manufacturing, fast erection speed, and excellent aerodynamic performance, making them the preferred bridge deck structure for long-span steel box girder bridges. Orthotropic steel bridge decks connect the top plate, longitudinal ribs, and transverse diaphragms through welding to form a structure with different stress requirements in the longitudinal and transverse directions. Longitudinal ribs are arranged at regular intervals in the longitudinal direction, and transverse diaphragms are arranged at regular intervals in the transverse direction. To form a cohesive whole with coordinated stress distribution, the plates are connected by welding. Under repeated vehicle loads, the bridge deck warps and deforms due to the significant difference in longitudinal and transverse stiffness. Particularly at the connection between the longitudinal ribs and transverse diaphragms, the presence of residual welding stress leads to severe stress concentration in the structural details, resulting in significant fatigue cracking. Currently, the nominal stress method and hot spot stress method are the only methods applicable to practical engineering for calculating fatigue details.

[0003] Traditional fatigue assessments are mostly based on the nominal stress method. The fatigue resistance curve in the nominal stress method is obtained through a large number of full-scale experiments. Theoretically, each fatigue detail needs to correspond to a unique S-N curve based on its detailed characteristics. In orthotropic steel bridge decks, it is suitable for fatigue design and assessment of details with small local deformation and easily determined nominal stress. However, the actual structure is very complex because there is out-of-plane deformation at the intersection of the longitudinal ribs and transverse plates of the orthotropic steel bridge deck, and the nominal stress cannot be determined. Therefore, the nominal stress method is no longer applicable to fatigue details in this case.

[0004] The hot spot stress in the hot spot stress method is not the actual stress of the structure, but an artificially imagined stress. Hot spot stress refers to the maximum structural stress or the stress at a critical point on a critical section of the structure. For welded joints, the stress reaches its maximum value at the surface of the weld toe, which is the hot spot stress. In welded structures, the weld toe is often taken as the hot spot because it is the most prone to fatigue failure. The International Welding Association (IWA) recommends two hot spot stress curves, FAT90 and FAT100, to calculate the fatigue load at this fatigue detail using the hot spot stress method. For Class A welds (weld toe located at the root of the subplate, on the surface of the base plate), the IWA provides three extrapolation curves. Differences in the selection of extrapolation curves can lead to different calculation results for the hot spot stress at the structural detail, resulting in significant differences in fatigue life calculations, causing confusion for designers. Therefore, it is necessary to research and propose a practically meaningful method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks, which can more reasonably predict the service life of these fatigue details.

[0006] The objective of this invention can be achieved through the following technical solutions.

[0007] A method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks includes the following steps:

[0008] S1: Investigate the historical traffic conditions of the road section where the target bridge is located, and calculate the average daily types of heavy-duty vehicles and the number of times different types of heavy-duty vehicles act on the orthotropic steel bridge deck.

[0009] S2: Select the target fatigue detail for research, and for the selected target fatigue detail structure, find the most unfavorable load distribution position when the wheel load corresponding to the axle load is applied to the orthotropic steel bridge deck, and obtain the peak stress σ1 at the target fatigue detail structure when the wheel load corresponding to the axle load is applied to the most unfavorable load distribution position.

[0010] S3: Obtain the maximum residual stress σ2 on the weld path at the intersection of the longitudinal ribs and transverse diaphragms of the orthotropic steel bridge deck.

[0011] S4: Calculate the service life of the target fatigue details:

[0012] S401: The peak stress σ1 and the maximum residual welding stress σ2 generated under the wheel load corresponding to the axle load are considered as external loads. The Goodman curve is used to perform an equal life conversion, and the resultant load of the peak stress σ1 and the maximum residual welding stress σ2 is converted into a symmetrical cyclic load.

[0013] S402: S-N curve based on the basic fatigue properties of the base material m ·N=C, where N is the number of fatigue load cycles when the experimental base material fails, S is the stress value corresponding to the symmetrical cyclic load when the fatigue load stress ratio is -1, and m and C are constants related to material properties. The annual damage degree of the target fatigue detail is calculated based on the symmetrical cyclic load converted from the resultant load of the peak stress σ1 and the maximum residual stress σ2 of welding described in step S401.

[0014] S403: Using Miner's linear cumulative damage theory The fatigue performance at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks was evaluated based on the S-N curves of the base material, and the fatigue failure time was determined. Where N i It corresponds to the load S i Fatigue life under action, n i It corresponds to the load Si The number of cycles under the action, D i For the component under the corresponding load S i Function n i The degree of damage in the next cycle, k is the number of wheel load types corresponding to the axle load of the heavy-duty vehicles each day, and i is a positive integer from 1 to k.

[0015] The present invention also has the following preferred designs:

[0016] The process of calculating the average daily heavy-load vehicle types and different types of heavy-load vehicles in step S1 of this invention is considered to be that vehicles with a load of less than 100kN do not suffer fatigue damage, according to Eurocode standards.

[0017] Step S2 of the present invention includes:

[0018] S201: First, determine the most unfavorable lateral load position of the axle: n1 load positions are set in the lateral direction. The wheel load center corresponding to the axle load on one side of the first lateral load position corresponds to the centerline between the target longitudinal rib and the adjacent longitudinal rib in the off-edge direction. The lateral interval between the second to n1 lateral load positions and the previous lateral load position is d1. Compare the peak stress at the target fatigue detail when the load is applied to the n1 lateral load positions. The load method corresponding to the maximum peak stress is the most unfavorable lateral load position for the target fatigue detail structure.

[0019] S202: Determine the most unfavorable longitudinal load position in the orthogonal direction of the most unfavorable transverse load position: n2 load positions are set in the longitudinal direction. The wheel load center corresponding to the axle load of the first longitudinal load position corresponds to the center line of the transverse diaphragm welded at the intersection with the target longitudinal rib. The longitudinal interval between the second to a1 longitudinal load positions and the previous longitudinal load position is d2. The longitudinal interval between the a1+1 to n2 longitudinal load positions and the previous longitudinal load position is d3. Compare the peak stress at the target fatigue detail when the load is applied to the n2 longitudinal load positions. The load method corresponding to the maximum peak stress is the most unfavorable longitudinal load position for the target fatigue detail structure.

[0020] Considering that the stress influence range of the wheel load corresponding to the axle load on the steel bridge deck is relatively small, generally not exceeding the spacing of 2 to 3 longitudinal ribs, n1, d1, n2, d2, and d3 in this invention are selected according to the longitudinal rib spacing, and n1, n2, and a1 are positive integers;

[0021] A finite element model was established using Abaqus to obtain the peak stress σ1 at the target fatigue detail structure when the wheel load corresponding to the axle load is applied to the most unfavorable load position.

[0022] As a feasible method of the present invention, in step S3, a temperature field model is established using Abaqus, and the welding process is simulated using a double ellipsoidal heat source to calculate the maximum residual stress σ2 on the weld path at the intersection of the longitudinal ribs and transverse diaphragms of the orthotropic steel bridge deck.

[0023] The S-N curve of the basic fatigue properties of the base material in this invention is the S-N curve of 16Mn steel.

[0024] The orthotropic steel bridge deck of the present invention includes a top plate, longitudinal ribs and transverse diaphragms. The transverse diaphragms are arranged longitudinally at intervals below the top plate, and the longitudinal ribs are arranged transversely at intervals below the top plate. The top plate, the transverse diaphragms and the longitudinal ribs are connected by welding.

[0025] The longitudinal ribs of the present invention are closed ribs, including U-shaped longitudinal ribs or trapezoidal longitudinal ribs.

[0026] The daily heavy-load vehicles counted in this invention include different models of heavy-load vehicles and cases of overloading of the same model of heavy-load vehicles.

[0027] The present invention has the following beneficial effects:

[0028] This invention, based on the S-N curve of the base material, treats the stress generated by the axle and the residual welding stress as external loads, and superimposes them to obtain the fatigue impact load at the intersection of the longitudinal ribs and transverse diaphragms of the bridge deck. After fatigue load-life conversion using the Goodman curve, the fatigue life of the intersection of the longitudinal ribs and transverse diaphragms is calculated based on Miner's linear cumulative damage theory. This invention solves the problem in traditional calculation methods where the nominal stress at the intersection of the longitudinal ribs and transverse diaphragms is difficult to determine due to out-of-plane deformation, making the nominal stress method inapplicable for this structural detail. It also avoids the confusion caused to designers by calculation differences due to different extrapolation curves in the hot spot stress method, and can effectively evaluate the fatigue performance of this detail. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view of a steel box girder bridge in one embodiment;

[0030] Figure 2 yes Figure 1 Detailed drawing of the intersection of longitudinal ribs and transverse diaphragms in the orthotropic steel bridge deck of a medium-sized steel box girder bridge.

[0031] Figure 3 yes Figure 1 Fatigue detail plan view at the intersection of longitudinal ribs and transverse diaphragms of orthotropic steel bridge deck of medium steel box girder bridge and schematic diagram of the first transverse load position.

[0032] Figure 4 yes Figure 1Fatigue detail plan view at the intersection of longitudinal ribs and transverse diaphragms of orthotropic steel bridge deck of medium steel box girder bridge and schematic diagram of the most unfavorable transverse load distribution position.

[0033] Figure 5 yes Figure 1 A schematic diagram of the first longitudinal load distribution position on the bridge deck of a medium-strength box girder bridge;

[0034] Figure 6 yes Figure 1 A schematic diagram of the most unfavorable longitudinal load distribution position of the bridge deck of a medium-sized steel box girder bridge;

[0035] Figure 7 This is a stress cloud diagram of the target fatigue details obtained by applying Abaqus finite element calculation when the wheel load corresponding to the axle load in the embodiment is applied to the most unfavorable load position.

[0036] Figure 8 The example uses a double ellipsoidal heat source to simulate the welding process, and the residual stress distribution cloud map is calculated using Abaqus finite element method.

[0037] Explanation of reference numerals in the attached drawings: A-top plate, B-diaphragm, U-longitudinal rib. In the embodiment, different longitudinal ribs are distinguished by adding a lower right subscript, such as longitudinal ribs U1 to U5. Detailed Implementation

[0038] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, so that those skilled in the art can better understand and implement the technical solution of the present invention.

[0039] This embodiment uses Figure 1 and Figure 2 The invention will be described in detail using a steel box girder bridge as an example. The orthotropic steel bridge deck of this embodiment comprises a top plate A, longitudinal ribs U, and transverse diaphragms B. The transverse diaphragms B are arranged longitudinally at intervals below the top plate A, and the longitudinal ribs U are arranged transversely at intervals below the top plate A. The top plate A, transverse diaphragms B, and longitudinal ribs U are connected by welding. The longitudinal ribs U are closed ribs and can be either U-shaped or trapezoidal.

[0040] A method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks includes the following steps:

[0041] S1: Investigate the historical traffic conditions of the road section where the target bridge is located, and calculate the average daily types of heavy-duty vehicles and the number of times different types of heavy-duty vehicles act on the orthotropic steel bridge deck.

[0042] In this embodiment, the process of calculating the average daily heavy-load vehicle types and different types of heavy-load vehicles is based on the Eurocode European standard, which states that vehicles with a load of less than 100kN do not cause fatigue damage. The daily heavy-load vehicles included in the statistics are different models of heavy-load vehicles and cases of overloading of the same model of heavy-load vehicles.

[0043] Historically, the section of road where the steel box girder bridge is located has primarily seen two types of heavy-duty vehicles. Based on whether they are overloaded, these can be categorized into four axle loads: 140kN, 160kN, 110kN, and 130kN, respectively, and designated as 1-1, 1-2, 2-1, and 2-2. Statistical analysis shows that axle load 1-1 is applied an average of 64 times per day; axle load 1-2 is applied an average of 53 times per day; axle load 2-1 is applied an average of 137 times per day; and axle load 2-2 is applied an average of 115 times per day.

[0044] S2: Select the target fatigue details for the study, such as Figure 3 and Figure 4 As shown, fatigue details at the intersection of longitudinal rib U2 and transverse diaphragm B are selected. For the selected target fatigue detail structure, the most unfavorable load distribution position when the wheel load corresponding to the axle load is applied to the orthotropic steel bridge deck is found. The peak stress σ1 at the target fatigue detail structure when the wheel load corresponding to the axle load is applied to the most unfavorable load distribution position is obtained.

[0045] This embodiment finds the most unfavorable load distribution position by considering that the stress influence range when the wheel load corresponding to the axle load acts on the steel bridge deck is relatively small, generally not exceeding the spacing of 2 to 3 longitudinal ribs.

[0046] S201: First, determine the most unfavorable lateral load placement position of the axle: a total of n1 = 10 lateral load placement positions are set. The wheel load center corresponding to the axle load on one side of the first lateral load placement position corresponds to the centerline between the target longitudinal rib and the adjacent longitudinal rib in the off-edge direction. See Figure 3 The axle load on one side of the axle is located on the center line between longitudinal rib U2 and longitudinal rib U1. The lateral interval between the 2nd to 10th lateral load positions and the previous lateral load position is d1 = 100mm. Compare the peak stress at the target fatigue detail when the load is applied to the 10 lateral load positions. The load distribution method corresponding to the maximum peak stress is the most unfavorable lateral load distribution position for the target fatigue detail structure.

[0047] S202: Determine the most unfavorable longitudinal load distribution location in the orthogonal direction to the most unfavorable transverse load distribution location: a total of n² = 11 load distribution locations are set in the longitudinal direction, see [link to relevant documentation]. Figure 5The wheel load center corresponding to the axle load at the first longitudinal loading position corresponds to the centerline of the transverse diaphragm welded at the intersection with the target longitudinal rib U2. The longitudinal interval between the 2nd to a1st longitudinal loading positions and the previous longitudinal loading position is d2, and the longitudinal interval between the a1+1nd to n2th loading positions and the previous loading position is d3. Compare the peak stress at the target fatigue details when the load is applied to 11 longitudinal loading positions, see [reference]. Figure 6 The load distribution method corresponding to the maximum peak stress is the most unfavorable longitudinal load distribution position for the target fatigue detail structure.

[0048] Where n1, d1, n2, d2, and d3 are selected according to the longitudinal rib spacing, and n1, n2, and a1 are positive integers. In this embodiment, a1 = 7, d2 = 150 mm, and d3 = 300 mm.

[0049] A finite element model was built using Abaqus to obtain the peak stress σ1 at the target fatigue detail when the wheel load corresponding to the axle load is applied to the most unfavorable load position. In this embodiment, the sixth lateral load position and the third longitudinal load position of the 1-1 axle load are the most unfavorable load positions. When the 1-1 axle load is applied to the most unfavorable load position, such as Figure 7 As shown, the calculated peak stress at the target fatigue detail is σ1 = 112.2 MPa;

[0050] S3: Obtain the maximum residual stress σ2 on the weld path at the intersection of the longitudinal ribs and transverse diaphragms of the orthotropic steel bridge deck.

[0051] In this embodiment, a temperature field model was established using Abaqus, and a double ellipsoidal heat source was used to simulate the welding process. The maximum residual stress σ2 on the weld path at the intersection of the longitudinal ribs and transverse diaphragms of the orthotropic steel bridge deck was calculated. Figure 8 As shown, DC3D8 was selected as the heat transfer element for heat transfer analysis. The calculated residual stress peak value of the weld path in the target fatigue detail is the principal tensile stress of 207 MPa, i.e., σ2 = 207 MPa.

[0052] S4: Calculate the service life of the target fatigue details:

[0053] S401: The peak stress σ1 and the maximum residual welding stress σ2 generated under the wheel load corresponding to the axle load are considered as external loads. The Goodman curve is used to perform equal life conversion, and the resultant load of the peak stress σ1 and the maximum residual welding stress σ2 is converted into a symmetrical cyclic load.

[0054] For example, the peak stress generated under wheel load corresponding to the axle load of 1-1 is a compressive stress of 112.2 MPa, i.e., peak stress σ1 = 112.2 MPa; the peak residual stress is a tensile stress of 207 MPa, i.e., maximum residual stress σ2 = 207 MPa. In this embodiment, the base material is Q345 steel, and the mechanical properties of Q345 steel are referenced to the basic fatigue performance S-N curve of 16Mn steel. Equal life conversion is performed using Goodman curves. In the formula σ a The stress amplitude (half amplitude), σ -1 σ represents the stress value of the corresponding symmetrical cyclic load after transformation. m The average stress value is σ. u The yield strength of the steel is used to transform the resultant load into a symmetrical cyclic load, corresponding to the S-N curve of the basic fatigue performance.

[0055] σ max =σ2=207MPa

[0056] σ min =σ2-σ1=207MPa-112.2MPa=94.8MPa

[0057] σ u =345MPa

[0058]

[0059]

[0060] Substituting into the Goodman curve, we obtain σ -1 =99.71MPa

[0061] Repeat steps S2, S3, and S401 to calculate the symmetrical cyclic fatigue loads under wheel loads with a stress ratio of -1 for axle loads of 1-2, 2-1, and 2-2, which are 109.44 MPa, 83.52 MPa, and 94.55 MPa, respectively.

[0062] S402: S-N curve based on the basic fatigue properties of the base material m ·N=C, where N is the number of fatigue load cycles when the experimental base material fails, S is the stress value corresponding to the symmetrical cyclic load when the fatigue load stress ratio is -1, and m and C are constants related to material properties. The annual damage degree of the target fatigue details is calculated based on the symmetrical cyclic load converted from the resultant load of the peak stress σ1 and the maximum residual stress σ2 of welding in step S401. In other embodiments, the basic fatigue performance S~N curve can also adopt other scientific and reasonable mathematical expressions.

[0063] S403: Using Miner's linear cumulative damage theory The fatigue performance at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks was evaluated based on the S-N curves of the base material, and the fatigue failure time was determined. Where N i It corresponds to the load S i Fatigue life under action, n i It corresponds to the load S i The number of cycles under the action, D i For the component under the corresponding load S i Function n i The degree of damage in the next cycle, k is the number of wheel load types corresponding to the axle load of the heavy-duty vehicles each day, and i is a positive integer from 1 to k. In this embodiment, four cases are obtained: 1-1 axle load, 1-2 axle load, 2-1 axle load, and 2-2 axle load, so k = 4.

[0064] For the S-N curve of the basic fatigue properties of 16Mn steel, take m = 3.3 and C = 11.4 × 10⁻⁶. 12 When the stress ratio is -1, i.e., under symmetrical cyclic loading, the fatigue strength of the base material is approximately 170 MPa. The fatigue safety factor can be taken as 1.4 to 1.5. In this embodiment, when 1.5 is taken, the fatigue strength of the base material is calculated to be 113 MPa, and the failure number corresponding to the S-N curve is 2 million cycles.

[0065] When the wheel load corresponding to the axle load of 1-1 is applied at the most unfavorable load distribution position, we have:

[0066]

[0067] n1 = 64 × 365 = 23360

[0068] That is, the wheel load corresponding to the axle load of 1-1 has an annual damage degree of 0.008 on the target fatigue details. Similarly, the annual damage degree of the wheel loads corresponding to the axle loads of 1-2, 2-1, and 2-2, respectively, when applied to their most unfavorable load positions, can be obtained. The fatigue life can be calculated, and the calculation results are summarized in Table 1.

[0069]

[0070]

[0071] Table 1

[0072] As shown in Table 1, this embodiment focuses on the fatigue details at the intersection of the longitudinal rib U2 and the transverse diaphragm, and its fatigue life is 25.51 years.

[0073] Comparative example:

[0074] Similarly, the fatigue details at the intersection of longitudinal rib U2 and transverse diaphragm are studied, and the hot spot stress method recommended by the International Welding Association is used for calculation. The process is briefly described below:

[0075] The International Welding Association (IWA) recommends two hot spot stress curves, FAT90 and FAT100. For calculating the stress at this fatigue detail (type a weld toe) using the hot spot stress method, the IWA recommends three extrapolation curves (for details, see Giberhay and Fu Zhongqiu, *Steel Bridge Fatigue and Maintenance*, People's Communications Press Co., Ltd., August 2016, 1st edition, pp. 25 and 26):

[0076] σ hs =1.67σ 0.4t -0.37σ 1.0t

[0077] σ hs =2.52σ 0.4t -2.24σ 0.9t +0.72σ 1.4t

[0078] σ hs =1.5σ 0.5t -0.5σ 1.5t

[0079] In the formula σ hs σ represents the stress at the weld toe hot spot, t represents the thickness of the transverse diaphragm at the weld, and σ represents the stress at the weld toe hot spot. 0.4t The stress value refers to the value at a distance of 0.4t from the weld toe hot spot. Similarly, σ is obtained. 1.0t σ 0.9t σ 1.4t σ 0.5t σ 1.5t .

[0080] The life calculation results for the target fatigue details of the example, using different extrapolation curves, are summarized in the table below:

[0081]

[0082]

[0083] The fatigue strength of the structural details was calculated using a hot-spot extrapolation method, yielding six different results. The final calculated life ranged from a minimum of 11.65 years to a maximum of 24.51 years, showing a significant difference. Among these results, taking the fatigue strength of the steel structural details as 100 MPa and using the third recommended extrapolation formula, the fatigue life calculated was 24.51 years. This result showed the smallest deviation from the calculation method used in this invention, with a deviation of only 0.03%, which also indirectly verifies the rationality of the calculation method in this invention.

[0084] The above embodiments are merely preferred embodiments of the present invention, but should not be construed as limiting the invention. Any modifications and improvements made based on the concept of the present invention should fall within the protection scope of the present invention, and the specific protection scope is subject to the claims.

Claims

1. A method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks, characterized in that, Includes the following steps: S1: Investigate the historical traffic conditions of the road section where the target bridge is located, and calculate the average daily types of heavy-duty vehicles and the number of times different types of heavy-duty vehicles act on the orthotropic steel bridge deck. S2: Select the target fatigue detail for research, and for the selected target fatigue detail structure, find the most unfavorable load distribution position when the wheel load corresponding to the axle load is applied to the orthotropic steel bridge deck, and obtain the peak stress σ1 at the target fatigue detail structure when the wheel load corresponding to the axle load is applied to the most unfavorable load distribution position. S3: Obtain the maximum residual stress σ2 on the weld path at the intersection of the longitudinal ribs and transverse diaphragms of the orthotropic steel bridge deck. S4: Calculate the service life of the target fatigue details: S401: The peak stress σ1 and the maximum residual welding stress σ2 generated under the wheel load corresponding to the axle load are considered as external loads. The Goodman curve is used to perform an equal life conversion, and the resultant load of the peak stress σ1 and the maximum residual welding stress σ2 is converted into a symmetrical cyclic load. S402: Based on the S-N curve of the basic fatigue properties of the base material, calculate the one-year damage degree of the target fatigue details by symmetrical cyclic load conversion of the resultant load of the peak stress σ1 and the maximum residual stress σ2 of welding as described in step S401. S403: Using Miner's linear cumulative damage theory The fatigue performance at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks was evaluated based on the S-N curves of the base material, and the fatigue failure time was determined. Where N i It corresponds to the load S i Fatigue life under action, n i It corresponds to the load S i The number of cycles under the action, D i For the component under the corresponding load S i Function n i The degree of damage in the next cycle, k is the number of wheel load types corresponding to the axle load of the heavy-duty vehicles each day, and i is a positive integer from 1 to k.

2. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 1, characterized in that: The process of calculating the average daily heavy-duty vehicle types and different types of heavy-duty vehicles in step S1, according to Eurocode standards, means that vehicles with a load below 100kN do not suffer fatigue damage.

3. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 2, characterized in that, Step S2 includes: S201: First, determine the most unfavorable lateral load position of the axle: n1 load positions are set in the lateral direction. The wheel load center corresponding to the axle load on one side of the first lateral load position corresponds to the centerline between the target longitudinal rib and the adjacent longitudinal rib in the off-edge direction. The lateral interval between the second to n1 lateral load positions and the previous lateral load position is d1. Compare the peak stress at the target fatigue detail when the load is applied to the n1 lateral load positions. The load method corresponding to the maximum peak stress is the most unfavorable lateral load position for the target fatigue detail structure. S202: Determine the most unfavorable longitudinal load position in the orthogonal direction of the most unfavorable transverse load position: a total of n2 load positions are set in the longitudinal direction. The wheel load center corresponding to the axle load of the first longitudinal load position corresponds to the center line of the transverse diaphragm welded at the intersection with the target longitudinal rib. The longitudinal interval between the second to a1 longitudinal load positions and the previous longitudinal load position is d2. The longitudinal interval between the a1+1 to n2 longitudinal load positions and the previous longitudinal load position is d3. Compare the peak stress at the target fatigue detail when the load is applied to the n2 longitudinal load positions. The load method corresponding to the maximum peak stress is the most unfavorable longitudinal load position for the target fatigue detail structure. Among them, n1, d1, n2, d2, and d3 are selected according to the longitudinal rib spacing, and n1, n2, and a1 are positive integers.

4. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 3, characterized in that: A finite element model was established using Abaqus to obtain the peak stress σ1 at the target fatigue detail structure when the wheel load corresponding to the axle load is applied to the most unfavorable load position.

5. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 4, characterized in that: In step S3, a temperature field model is established using Abaqus, and the welding process is simulated using a double ellipsoidal heat source. The maximum residual stress σ2 on the weld path at the intersection of the longitudinal ribs and transverse diaphragms of the orthotropic steel bridge deck is calculated.

6. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 5, characterized in that: The S-N curve of the basic fatigue properties of the base material is the S-N curve of 16Mn steel.

7. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to any one of claims 1 to 6, characterized in that: The orthotropic steel bridge deck includes a top plate, longitudinal ribs, and transverse diaphragms. The transverse diaphragms are arranged longitudinally at intervals below the top plate, and the longitudinal ribs are arranged transversely at intervals below the top plate. The top plate, the transverse diaphragms, and the longitudinal ribs are connected by welding.

8. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 7, characterized in that: The longitudinal ribs are closed ribs, including U-shaped longitudinal ribs or trapezoidal longitudinal ribs.

9. The method for calculating the service life of fatigue details at the intersection of longitudinal ribs and transverse diaphragms in orthotropic steel bridge decks according to claim 2, characterized in that: The daily statistics on heavy-duty vehicles include different models of heavy-duty vehicles and cases of overloading of the same model of heavy-duty vehicles.

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