Method for calculating composite gradient of longitudinal section of bridge based on train axle load

Abstract

The invention relates to a calculation method for a composite gradient of a longitudinal section of a bridge based on axle load of a train. The calculation method comprises the following steps: S1, acquiring the total time step number of bridge crossing of the train and the wheel set position of the train under each time step; s2, fitting a bridge linear function within the length range of the train getting on the bridge at a certain time step; s3, determining the gradient corresponding to the axle weight borne by a wheel set at the wheel set position of the upper bridge according to the wheel set position of the upper bridge and the bridge linear function of the upper bridge at the time step; s4, according to the axle weight borne by the locomotive wheelset, the axle weight borne by the truck wheelset and the gradient corresponding to the axle weight borne by the position of the upper axle wheelset under the time step, calculating the composite gradient of the train during bridge crossing under the time step; and the steps S2 to S4 are repeated, and the dynamic composite gradient in the train bridge crossing time history is obtained. According to the calculation method provided by the invention, the influence of axle loads borne by different slope sections and train wheel pairs on the gradient is considered, the calculation result better conforms to the actual situation, and the precision is correspondingly improved.

Description

Technical Field

[0001] The invention relates to the technical field of bridge longitudinal section design, and in particular to a method for calculating a composite slope of a bridge longitudinal section based on train axle weight. Background Art

[0002] During the operation and maintenance of railway bridge lines, it is inevitable that they will deform under conditions such as temperature, train load, and wind load. Taking suspension bridges as an example, suspension bridges have a large overall flexibility and are greatly affected by overall deformation under the action of temperature loads. When the temperature drops significantly, the overall line shape of the bridge will have a certain upward arch, which will pose certain challenges to heavy-loaded trains climbing the slope. Therefore, under the action of natural conditions and subject to the limitations of project investment and terrain, how to accurately identify the slope of railway bridge lines while ensuring economy so that heavy-loaded trains can pass through larger slopes has become an urgent problem to be solved.

[0003] In the related technology, for example, the locomotive algorithm is based on a heavy-load train with a traction locomotive, and only calculates the corresponding slope of the locomotive at the front position during the continuous uphill stage. The slope result calculated by the locomotive algorithm is too conservative, and the slope limit is too large, and cannot be used as a representative value for bridge slope calculation. Alternatively, the slope of the line connecting the coordinate points at both ends of the bridge is used as the slope, but when the train passes the bridge, the longitudinal section of the bridge does not have a long longitudinal section like the railway line, and generally considers the arrangement of a herringbone slope. Therefore, when the train passes the bridge, within the total length of the train, the train may be in a stage of crossing multiple slopes, and it is impossible to be completely in the train climbing stage. In addition, the longitudinal section of the bridge line section contains a shorter restricted ramp, even shorter than the length of the train. If other slope sections in the middle section are not considered, the calculation result will not be consistent with the actual situation and the accuracy will be low. Summary of the invention

[0004] The present application provides a method for calculating the composite slope of the longitudinal section of a bridge based on the train axle weight, which solves the technical problems in the related art that the calculation result of the slope calculated by the locomotive algorithm is too conservative, inconsistent with the actual situation when the intermediate slope section is not considered, and has low accuracy.

[0005] The embodiment of the present application provides a method for calculating the composite slope of a bridge longitudinal section based on train axle load, which comprises the following steps: Step S1, obtaining the total time steps of the train crossing the bridge and the wheel position of the train at each time step; Step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step; Step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge according to the wheelset position of the train on the bridge at the time step and the bridge linear function; Step S4, calculating the composite slope of the train when crossing the bridge at this time step according to the axle weight borne by the locomotive wheelset and the axle weight borne by the truck wheelset in the train and the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge at this time step; Repeat steps S2 to S4 to obtain the dynamic composite slope during the time history of the train crossing the bridge.

[0006] In one embodiment, in step S4, the composite slope of the train when crossing the bridge at the time step is calculated according to the axle weight borne by the locomotive wheelset and the axle weight borne by the truck wheelset in the train and the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge at the time step, The calculation formula is: ; in, is the composite slope; The axle load borne by the locomotive wheelset; The axle load borne by the truck wheelset; The slope corresponding to the axle load borne by the wheelset at the wheelset position; The total number of wheelsets in the train set.

[0007] In one embodiment, the step S1, obtaining the total time steps of the train crossing the bridge and the wheel pair position of the train at each time step, comprises: Step S11, obtaining the train speed and the bridge length to obtain the total time steps for the train to cross the bridge; Step S12: determine the train length and the total number of wheel pairs according to the train formation, so as to obtain the bridge position corresponding to each wheel pair of the train at each time step as the wheel pair position.

[0008] In one embodiment, the step S2 of fitting the bridge linear function within the length range of the train on the bridge at a certain time step comprises: Step S21, determining the train length of the train on the bridge and the number of bridge nodes within the train length range based on the positions of different wheel pairs at a certain time step; Step S22, extracting the bridge node coordinates and node displacement values ​​within the length range of the train according to the position of the corresponding wheel pair on the bridge, so as to obtain the longitudinal section line shape of the bridge; Step S24, curve fitting is performed on the longitudinal section line shape of the bridge to obtain the bridge line shape function within the length range of the train on the bridge at this time step.

[0009] In one implementation, the bridge node coordinates and node displacement values ​​are acquired through a bridge finite element model.

[0010] In one embodiment, the step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step, also includes: step S23, encrypting the longitudinal section linear shape of the bridge.

[0011] In one embodiment, the step S23, encrypting the longitudinal section of the bridge, comprises any one of a cubic spline interpolation method, a least squares method, a Lagrange polynomial interpolation method, and a Hermite polynomial interpolation method.

[0012] In one embodiment, dynamic fitting is used when performing curve fitting on the longitudinal section line shape of the bridge.

[0013] In one embodiment, the dynamic fitting includes: Select the fitting objective function as an n-order polynomial; The optimal polynomial degree is evaluated according to the longitudinal section line shape of the bridge and fitting is performed.

[0014] In one embodiment, the step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge according to the wheelset position of the train on the bridge at the time step and the bridge linear function, comprises: Step S31, performing a derivation on the bridge linear function to obtain a slope expression; Step S32, calculate the bridge linear slope value corresponding to each wheelset according to the wheelset position of the train on the bridge at this time step and the slope expression, as the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge.

[0015] The beneficial effects brought by the technical solution provided in the embodiments of the present application include: The present application provides a method for calculating the composite slope of the longitudinal section of a bridge based on the train axle weight, taking into account the influence of different slope sections, fitting the train bridge crossing line shape in segments based on the time steps of the train crossing the bridge, accurately fitting the bridge line shape function, and the calculation result is more in line with the actual situation; at the same time, considering the influence of the axle weight borne by different wheelsets of the train on the slope, the calculated mass and traction mass of the train are shared by the wheelsets of the locomotive and the freight car, and the average slope of the train when crossing the bridge is calculated as the composite slope through the conversion relationship between the axle weight borne by the wheelset and the slope. The calculation result is further in line with the actual situation, will not be conservative, and the accuracy is correspondingly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the geometric structure of a train in one embodiment of the present invention.

[0018] Figure 2 The figure is a schematic diagram of a finite element model of a bridge in one embodiment of the present invention.

[0019] Figure 3 This is a result curve diagram based on the locomotive algorithm in one embodiment of the present invention.

[0020] Figure 4 It is a result curve diagram of a method for calculating the composite slope of the longitudinal section of a bridge based on train axle weight in one embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] The embodiment of the present application provides a method for calculating the composite slope of the longitudinal section of a bridge based on the train axle weight, which can solve the technical problems in the related art that the calculation result of the locomotive algorithm for calculating the slope is too conservative, inconsistent with the actual situation when not considering the intermediate slope section, and low precision.

[0023] This embodiment provides a method for calculating the composite slope of a bridge longitudinal section based on train axle load, which includes the following steps: Step S1, obtaining the total time steps of the train crossing the bridge and the wheel position of the train in each time step; Step S2, fitting the bridge linear function within the train length range of the train going onto the bridge at a certain time step; Step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge according to the wheelset position of the train on the bridge at the time step and the bridge linear function; Step S4, calculating the composite slope of the train when crossing the bridge at this time step according to the axle weight borne by the locomotive wheelset in the train and the axle weight borne by the truck wheelset and the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge at this time step; Repeat steps S2 to S4 to obtain the dynamic composite slope during the time history of the train crossing the bridge.

[0024] This embodiment provides a method for calculating the composite slope of the longitudinal section of a bridge based on the train axle weight, taking into account the influence of different slope sections, and fitting the train bridge crossing line shape in segments based on the time steps of the train crossing the bridge, accurately fitting the bridge line shape function, and the calculation result is more in line with the actual situation; at the same time, the influence of the axle weight borne by different wheelsets of the train on the slope is considered, and the calculated mass and traction mass of the train are shared by the wheelsets of the locomotive and the freight car. The average slope of the train when crossing the bridge is calculated as the composite slope through the conversion relationship between the axle weight borne by the wheelset and the slope. The calculation result is further in line with the actual situation, will not be conservative, and the accuracy is correspondingly improved.

[0025] Each step is described and explained in detail below.

[0026] In one embodiment, step S1, obtaining the total time steps of the train crossing the bridge and the wheel pair position of the train in each time step, comprises: Step S11, obtaining the train speed and the bridge length to obtain the total time steps for the train to cross the bridge.

[0027] Step S12: determine the train length and the total number of wheel pairs according to the train formation, so as to obtain the bridge position corresponding to each wheel pair of the train at each time step as the wheel pair position.

[0028] Specifically, the train length and the total number of wheel pairs of the train can be determined through the train formation, and then the bridge position corresponding to each wheel pair of the train in each time step within the total time step can be calculated based on the geometric structure of the train, which can be used as the wheel pair position or the wheel pair coordinate; the wheel pair position can be in matrix form.

[0029] Through the above scheme, the wheel set position of the train at each time step is determined, which serves as the basis for the subsequent segmented fitting of the bridge linear function to obtain the slope of each wheel set position.

[0030] like Figure 1 As shown, Figure 1 Schematic diagram of the geometric structure of a train in one embodiment of the present invention.

[0031] in, m c is the mass of the train body; m b is the mass of the train bogie; m t is the mass of the wheelset; the axle load is the weight of the train acting on the rails through each wheelset, so the axle load mass borne by the wheelset = ( m c +2* m b +4* m t ) / 4; l 1 and l2 is the distance between the primary suspension and the secondary suspension, which is used to determine the coordinates of the wheelset within the time step; the primary suspension, also known as the main suspension, is set between the locomotive bogie frame and the axle box, and mainly plays the role of transmitting the force between the axle box and the wheelset and positioning. The secondary suspension, also known as the secondary suspension, is set between the car body frame and the bogie frame, and mainly plays the role of connecting the frame and the car body, and has a certain limiting effect on the lateral rotation of the car body.

[0032] In one embodiment, step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step, comprises: Step S21, based on the positions of different wheel pairs at a certain time step, determine the train length of the train on the bridge and the number of bridge nodes within the train length range.

[0033] Specifically, the length of the train on the bridge is determined according to the position of different wheel sets at a certain time step. If the wheel set is on the bridge, it means that this part of the train body is also on the bridge, and then the bridge line shape of this section on the bridge is selected. It should be noted that only the length of the body part on the bridge is considered, and the body part that is not on the bridge or out of the bridge is not considered in the calculation.

[0034] Step S22, extracting the bridge node coordinates and node displacement values ​​within the length range of the train according to the position of the corresponding wheel pair on the bridge, so as to obtain the longitudinal section line shape of the bridge.

[0035] In one embodiment, the bridge node coordinates and node displacement values ​​are obtained through the bridge finite element model. The bridge node coordinates are used as the horizontal coordinates, and the node displacement values, i.e., the vertical deformation values ​​of the bridge nodes, are used as the vertical coordinates, thereby extracting the longitudinal section line of the bridge.

[0036] Step S24, curve fitting is performed on the longitudinal section line of the bridge to obtain the bridge line shape function within the length range of the train on the bridge at this time step.

[0037] Since the bridge alignment within the train range in different time steps is different, through the above scheme, the bridge alignment function within the train length range of the bridge under the segmented fitting time step is closer to the actual situation, ensuring the smoothness and stability of the alignment.

[0038] In one embodiment, step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step, also includes: step S23, encrypting the longitudinal section linear shape of the bridge.

[0039] Through the above scheme, encryption processing can improve the integrity and continuity of the data and supplement the values ​​between known bridge data points, making the data smoother and the trend more obvious.

[0040] In one embodiment, step S23, encrypting the longitudinal section of the bridge includes any one of the cubic spline interpolation method, the least squares method, the Lagrange polynomial interpolation method, and the Hermite polynomial interpolation method.

[0041] Specifically, it is further preferred to encrypt the data points on the bridge longitudinal section line shape by cubic spline interpolation method, and the interpolation curve generated by cubic spline interpolation method will gradually approach the actual curve as the interval between interpolation points decreases. In addition, the interpolation curve has the characteristics of good shape preservation and smoothness.

[0042] In one embodiment, in step S24, dynamic fitting is used when performing curve fitting on the longitudinal section line of the bridge.

[0043] In one embodiment, dynamic fitting includes: Select the fitting objective function as n Polynomial of degree; The optimal polynomial degree is evaluated according to the longitudinal section line shape of the bridge and fitted.

[0044] Specifically, the fitting objective function of the bridge line shape is generally n Polynomial of degree: If the order of the objective function is n If the value is set too small, underfitting may occur, that is, the fitted function cannot capture the complexity and characteristics of the bridge line shape, which is manifested as the fitting curve cannot accurately track the trend of the data points, resulting in a large prediction error. n Setting it too large may lead to overfitting.

[0045] Through the above scheme, the optimal polynomial degree is evaluated according to the longitudinal section line shape of the bridge, and dynamic fitting is performed to obtain the appropriate order of the objective function.

[0046] In one embodiment, step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge according to the wheelset position of the train on the bridge at the time step and the bridge linear function, comprises: Step S31, taking a derivative of the bridge linear function to obtain a slope expression; Step S32, calculate the bridge linear slope value corresponding to each wheelset according to the wheelset position of the train going up the bridge at this time step and the slope expression, as the slope corresponding to the axle weight borne by the wheelset at the wheelset position going up the bridge.

[0047] In one embodiment, step S4, according to the axle weight borne by the locomotive wheelset in the train and the axle weight borne by the truck wheelset, and the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge at the time step, the composite slope of the train when crossing the bridge at the time step is calculated. The calculation formula is: ; in, is the composite slope; The axle load borne by the locomotive wheelset; The axle load borne by the truck wheelset; It is the slope corresponding to the axle load borne by the wheelset at the wheelset position; The total number of wheelsets in the train set.

[0048] In the related technology, the locomotive algorithm is used to calculate the slope. The specific content is: According to the "Railway Line Design Specifications" (GB50090-2006), the maximum slope of a single-locomotive traction heavy-load railway line is the slope at which a locomotive traction heavy-load train finally runs at a constant speed at the calculated speed of the locomotive on a continuous uphill slope. The calculation formula is: ; Where: Calculate the mass for the locomotive; The quality standards of traction proposed for the design; is the locomotive traction coefficient, which is taken as 0.9; is the maximum traction mass of the train; , is the unit basic resistance of the locomotive and freight car; this formula is adapted to the environment where a single locomotive is pulling a heavy-load train on a continuous uphill slope.

[0049] The present application found that the slope is a dimensionless constant of the train traction mass, that is, the slope value is obtained by converting the mass of the train wheelsets. Therefore, considering the influence of the axle weights borne by different wheelsets of the train on the slope, the train calculation mass and traction mass are shared on the wheelsets of the locomotive and the freight car, and the average slope of the train when crossing the bridge is calculated by the axle weights borne by the wheelsets as the composite slope. The calculation result is more in line with the actual situation, will not be conservative, and the accuracy is correspondingly improved.

[0050] Through the above scheme, the composite slope at a certain time step is obtained, and the dynamic composite slope of the time history of the train crossing the bridge is obtained by repeating steps S2-S4 according to different loop solutions according to the train's forward position.

[0051] A specific embodiment is provided below for illustration.

[0052] like Figure 2 As shown, Figure 2 The figure is a schematic diagram of a finite element model of a bridge in one embodiment of the present invention.

[0053] The project background is a large-span suspension bridge scheme, which is a double-cable-plane railway bridge with a span arrangement of 168m+1092m+168m and three continuous spans.

[0054] This embodiment provides a method for calculating the composite slope of a bridge longitudinal section based on train axle load, which includes the following steps: Step S1, obtaining the total time steps of the train crossing the bridge and the wheel position of the train at each time step.

[0055] Specifically, the bridge length is 1428 meters, the train speed is set to 30m / s, and the distance the train moves forward per time step is 3 meters. The total number of time steps for the train to cross the bridge is about t_num=476 time steps. The total length of the train is set to 8 marshalings, with a total of 32 wheel pairs. Figure 1 As shown, l 1 = 1.25 meters, l 2 = 8.75 meters. The position xx of each wheel pair on the bridge in 476 time steps is calculated, and the dimension of the xx matrix is ​​(476, 32).

[0056] Step S2, fitting the bridge linear function within the length range of the train that goes onto the bridge at a certain time step.

[0057] Based on the position of different wheel sets at a certain time step, the train length L_nihe of the train on the bridge and the number of bridge nodes n_fenduan within the train length range are determined. The bridge node coordinates and node displacement values ​​are obtained through the bridge finite element model. The bridge node coordinates and node displacement values ​​within the train length range are extracted according to the position of the corresponding wheel set on the bridge. The bridge node coordinates are used as the horizontal coordinates and the node displacement values ​​are used as the vertical coordinates to extract the bridge longitudinal section line shape. The extracted bridge longitudinal section line shape is encrypted by the cubic spline interpolation method. The bridge linear function within the train length range of the bridge on the time step is dynamically fitted.

[0058] Step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position of the train going up the bridge at this time step and the bridge linear function.

[0059] Specifically, the bridge linear function is differentiated once to obtain the slope expression; the slope expression is substituted into the slope expression according to the wheelset position of the train going up the bridge at that time step to calculate the bridge linear slope value corresponding to each wheelset, which is used as the slope corresponding to the axle load borne by the wheelset at the wheelset position going up the bridge.

[0060] Step S4, calculating the composite slope of the train when crossing the bridge at this time step according to the axle load borne by the locomotive wheelset in the train and the axle load borne by the truck wheelset, and the slope corresponding to the axle load borne by the wheelset at the wheelset position on the bridge at this time step.

[0061] The calculation formula is: .

[0062] Repeat steps S2 to S4 to obtain the dynamic composite slope during the time history of the train crossing the bridge.

[0063] Under the same conditions, the locomotive algorithm is used to calculate the slope.

[0064] The calculation formula is: .

[0065] like Figure 3 and Figure 4 As shown, Figure 3 This is a result curve diagram based on the locomotive algorithm in one embodiment of the present invention. Figure 4 It is a result curve diagram of a method for calculating the composite slope of the longitudinal section of a bridge based on train axle weight in one embodiment of the present invention.

[0066] pass Figure 3 , Figure 4 It can be seen that the maximum value of the slope calculated based on the existing locomotive algorithm is 3.052‰. Through the calculation method of the composite slope provided in the embodiment of the present application, the maximum value of the composite slope calculated based on the single-line operation of 1 locomotive and 8 freight cars with an axle weight of 8.4t per linear meter is 2.888‰, which is 5.4% lower than the slope calculated based on the locomotive algorithm. The maximum value of the composite slope calculated based on the single-line operation of 1 locomotive and 16 freight cars is 2.488‰, which is 18.48% lower than the slope calculated based on the locomotive algorithm.

[0067] The above results show that the existing locomotive algorithm is more conservative than the calculation method provided in the embodiment of the present application, which will have an adverse impact on bridge design and railway operation investment. The calculation method provided in the embodiment of the present application has positive significance for saving engineering costs and improving the operating capacity of heavy-load trains.

[0068] It should be noted that the above-mentioned serial numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments. The terms "including" and "having" in the specification and claims of the present application and the above-mentioned drawings and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" and the like are described to distinguish different objects, etc., and do not represent the order of precedence, nor do they limit that "first", "second" and "third" are different types.

[0069] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0070] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or. For example, A / B can mean A or B. The “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0071] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0072] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for calculating the composite slope of a bridge longitudinal section based on train axle load, characterized in that: It includes the following steps: Step S1, obtaining the total time steps of the train crossing the bridge and the wheel position of the train at each time step; Step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step; Step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge according to the wheelset position of the train on the bridge at the time step and the bridge linear function; Step S4, calculating the composite slope of the train when crossing the bridge at this time step according to the axle weight borne by the locomotive wheelset and the axle weight borne by the truck wheelset in the train and the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge at this time step; Repeat steps S2 to S4 to obtain the dynamic composite slope during the time history of the train crossing the bridge.

2. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 1, characterized in that: In step S4, the composite slope of the train when crossing the bridge at this time step is calculated according to the axle weight borne by the locomotive wheelset in the train and the axle weight borne by the truck wheelset, and the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge at this time step. The calculation formula is: ; in, is the composite slope; The axle load borne by the locomotive wheelset; The axle load borne by the truck wheelset; The slope corresponding to the axle load borne by the wheelset at the wheelset position; The total number of wheelsets in the train set.

3. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 1, characterized in that: The step S1, obtaining the total time steps of the train crossing the bridge and the wheel position of the train at each time step, comprises: Step S11, obtaining the train speed and the bridge length to obtain the total time steps for the train to cross the bridge; Step S12: determine the train length and the total number of wheel pairs according to the train formation, so as to obtain the bridge position corresponding to each wheel pair of the train at each time step as the wheel pair position.

4. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 1, characterized in that: The step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step, comprises: Step S21, determining the train length of the train on the bridge and the number of bridge nodes within the train length range based on the positions of different wheel pairs at a certain time step; Step S22, extracting the bridge node coordinates and node displacement values ​​within the length range of the train according to the position of the corresponding wheel pair on the bridge, so as to obtain the longitudinal section line shape of the bridge; Step S24, curve fitting is performed on the longitudinal section line shape of the bridge to obtain the bridge line shape function within the length range of the train on the bridge at this time step.

5. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 4, characterized in that: The bridge node coordinates and node displacement values ​​are obtained through a bridge finite element model.

6. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 4, characterized in that: The step S2, fitting the bridge linear function within the length range of the train on the bridge at a certain time step, also includes: step S23, encrypting the longitudinal section linear shape of the bridge.

7. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 6, characterized in that: The step S23, encrypting the longitudinal section of the bridge, includes any one of the cubic spline interpolation method, the least squares method, the Lagrange polynomial interpolation method, and the Hermite polynomial interpolation method.

8. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 4, characterized in that: Dynamic fitting is adopted when performing curve fitting on the longitudinal section line shape of the bridge.

9. The method for calculating the composite slope of the longitudinal section of a bridge based on train axle load according to claim 8, characterized in that: The dynamic fitting includes: Select the fitting objective function as an n-order polynomial; The optimal polynomial degree is evaluated according to the longitudinal section line shape of the bridge and fitting is performed.

10. The method for calculating the composite slope of a bridge longitudinal section based on train axle load according to claim 1, characterized in that: The step S3, determining the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge according to the wheelset position of the train on the bridge at the time step and the bridge linear function, comprises: Step S31, performing a derivation on the bridge linear function to obtain a slope expression; Step S32, calculate the bridge linear slope value corresponding to each wheelset according to the wheelset position of the train on the bridge at this time step and the slope expression, as the slope corresponding to the axle weight borne by the wheelset at the wheelset position on the bridge.

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