A method for analyzing dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under train action

Abstract

The present invention discloses a method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train. By establishing a train-longitudinal bridge system coupled nonlinear dynamic model that takes into account the dynamic contact of the bridge-rail interface, the wheel-rail normal force and the wheel-rail tangential force are calculated according to the established model and the relevant wheel-rail contact theory. According to the actual connection characteristics and contact relationship between the layers of the train-longitudinal bridge system, the train-longitudinal bridge system coupled nonlinear dynamic model is assembled, and the correctness of the established train-longitudinal bridge system coupled nonlinear dynamic model is verified by using an existing dynamic model; then the side pier settlement value is set, and the dynamic change characteristics of the bridge-rail structure and the dynamic change characteristics of the connection between the bridge-rail interface layers are analyzed before, when and after the train passes through the settlement area. The analysis method of the present invention explores the dynamic contact behavior of the bridge-rail system interface at the pier settlement under the action of the train and its influence on the dynamic performance of the train, providing theoretical support for ensuring the service safety of the line.

Description

Technical Field

[0001] The invention relates to a method for analyzing dynamic contact characteristics of a longitudinal bridge rail system interface at a side pier settlement location under the action of a train. Background Art

[0002] The longitudinally connected slab ballastless track-bridge system is widely used in my country's high-speed railway lines. The system consists of rails, fasteners, track plates, CA mortar layers, base plates, sliding layers, main beams, supports, bridge piers, pile foundations, etc. Its biggest feature is that the track plates (base plates) are connected as a whole along the longitudinal direction, which reduces the unevenness of the track caused by the joints between the plates. At the same time, the reduction of free ends also improves the mechanical properties of the track. However, its longitudinal connection characteristics lead to its poor resistance to the settlement of bridge piers. Once the bridge piers settle, the beam will undergo vertical displacement, and the longitudinally connected ballastless track laid on the beam will also bend and deform, and the bridge-rail interface contact will be discontinuous. Figure 1 As shown in (a), before the train passes through the settlement area, the settlement of the bridge pier causes the beam to deform, and the track also undergoes "follow-up" deformation under its own weight. At this time, after the longitudinal ballastless track-bridge system stabilizes to a new static equilibrium state, the track produces static additional geometric irregularities and the bridge-track interface "disconnects"; when the train passes through the settlement area, the bridge-track interface at the settlement pier will appear in a "fitting" dynamic contact state, causing the track to produce dynamic irregularities ( Figure 1 (b)); When the train passes through the settlement area, the bridge-rail interface will be in a "disconnected" contact state ( Figure 1 (c) The bridge-rail interface gradually deteriorates, aggravating the wheel-rail vibration, which in turn creates a vicious cycle and has a negative impact on driving stability and safety.

[0003] In recent years, many studies have been conducted on the static contact characteristics of the train-bridge coupling system. For example, Gou et al., based on the proposed bridge-rail deformation mapping analytical model, conducted an in-depth study on the influence mechanism and change law of the additional deformation of the bridge on the dynamic response of the train-bridge system. Gou Hongye et al. established a general model of bridge-rail deformation mapping with the influence of interlayer component contact stiffness mutation, studied the quantitative relationship between the additional deformation of the bridge and driving safety, and further took the stiffness mutation of the track interlayer component into consideration, revealing the influence of the interlayer component contact stiffness mutation on the contact characteristics of the bridge-rail interface. Xiao et al. analyzed the influence of the failure of the track support under the track on the dynamic response and ride comfort of the vehicle, and concluded that the influence of the fastener failure on the dynamic derailment of the train is an exponential change law. Feng derived a characterization model between the settlement of the bridge pier and the failure of the interlayer interface connection between the line-bridge system based on Castigliano's second theorem and the principle of linear superposition. Based on this characterization model, the development law of the interlayer interface connection failure of the line-bridge system caused by the settlement of the bridge pier was analyzed. However, most existing studies focus on the static contact characteristics between the subgrade or simply supported beam-bridge rail interface. There are few studies on the location, formation mechanism and development law of the "open-close" dynamic contact discontinuity at the bridge-rail interface caused by train load at the settlement of the side pier of the over-static continuous beam.

[0004] Therefore, it is an urgent problem to ensure the service safety of the line to explore the dynamic contact behavior of the bridge-rail system interface at the pier settlement under the action of the train and its impact on the dynamic performance of the train. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train. By establishing a coupled dynamic model of the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement taking into account the action of the train, the dynamic displacement change characteristics of the bridge-rail structure under different states before, during and after the train passes through the settlement area, the dynamic change law of the additional stress and the dynamic change characteristics of the interlayer connection are analyzed, providing a certain theoretical basis for judging the stable and safe operation of the train on the bridge and the service performance of the bridge and rail. The specific technical scheme is as follows:

[0006] A method for analyzing dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under train action comprises the following steps:

[0007] Step 1: Establish a coupled nonlinear dynamic model of the train-longitudinal bridge system considering the dynamic contact between the bridge and track interface;

[0008] Step 2: Calculate the wheel-rail normal force and wheel-rail tangential force based on the established model and relevant wheel-rail contact theory;

[0009] Step 3: According to the actual connection characteristics and contact relationship between the layers of the train-longitudinal bridge system, assemble the coupled nonlinear dynamic model of the train-longitudinal bridge system;

[0010] Step 4: Use the existing dynamic model to verify the correctness of the established train-longitudinal bridge system coupled nonlinear dynamic model;

[0011] Step 5: Set the side pier settlement value, and analyze the dynamic change characteristics of the bridge-rail structure and the dynamic change characteristics of the connection between the bridge-rail interface layers before, when and after the train passes through the settlement area.

[0012] In the above-mentioned method for analyzing the dynamic contact characteristics of the interface of the longitudinal bridge-rail system at the side pier settlement under the action of the train, in step one, the established nonlinear dynamic model of the train-longitudinal bridge system coupling is a CRH380A EMU train; its single-section train consists of a car body, two bogies, and four wheel pairs, and the train car body, bogies, and wheel pairs are all rigid bodies; the train and bogie consider five degrees of freedom, namely, sinking and floating, lateral movement, side rolling, nodding, and shaking, and the wheelset considers two degrees of freedom, namely, lateral movement and shaking; the car body unit attribute is set to a discrete solid unit and converted into a shell unit, the bogie is a discrete rigid body tensile unit, and the wheelset is an analytical rigid body rotation shell unit; the wheel and the bogie are connected by a primary suspension, and the bogie and the car body are connected by a secondary suspension. In the ABAQUS simulation software, a spring and a damping Cartesian connector are uniformly adopted, and the wheel tread adopts an LMA wear-type tread.

[0013] In the above-mentioned method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under the action of the train, in step 2, the wheel-rail normal force and the wheel-rail tangential force are calculated, wherein:

[0014] The wheel-rail normal contact adopts HERTZ nonlinear elastic contact, and its normal force is calculated as follows:

[0015]

[0016] Where:

[0017] p(t)—wheel-rail normal force (N),

[0018] G—wheel-rail contact constant (m / N 3 / 2 ),

[0019] △Z(t)—elastic compression between wheel and track (m),

[0020] t—time (s);

[0021] The wheel-rail tangential force is determined by the wheel-rail normal force and the friction coefficient, and its expression is:

[0022] F=p(t)×μ

[0023] Where:

[0024] μ—friction coefficient,

[0025] F—wheel-rail tangential force (N),

[0026] p(t)—wheel-rail normal force (N);

[0027] The above-mentioned dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of trains,

[0028] The elastic compression between the wheel and the rail △Z(t) represents the relative displacement between the wheel and the rail at the wheel-rail contact point, and its specific calculation formula is:

[0029] △Z(t)=Z wj (t)-Z r (x rj ,t)

[0030] Where:

[0031] w—wheel,

[0032] j—wheel position,

[0033] r—rail,

[0034] Z wj (t)—displacement of the j-th wheel at time t (m),

[0035] Z r (x rj ,t)—the order is the displacement of the rail under the j-th wheel at time t (m), t=1, 2, 3, 4;

[0036] When △Z(t)<0, that is, when the wheel is out of contact with the rail, the wheel-rail normal force p(t)=0;

[0037] Assume that the wheel displacement at the contact surface is Z 0 (t), then the wheel-rail normal force expression is:

[0038]

[0039] Where: G = 3.86R -0.115 ×10 -8 , R is the wheel radius.

[0040] In the aforementioned method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under the action of the train, in step 3, the assembly train-longitudinal bridge system coupled nonlinear dynamic model is specifically as follows:

[0041] The sleeper and track slab are constrained by surface-to-surface TIE contact;

[0042] The CA mortar layer and rail fasteners are simulated using linear springs;

[0043] The contact between the base plate and the sliding layer is simulated by a nonlinear spring that is only compressed but not tensile;

[0044] The sliding layer and the bridge deck adopt surface-to-surface TIE contact;

[0045] Consolidation constraints are imposed on the bridge and track end positions in non-settlement areas, and the supports between the bridge piers and the beams are simulated by springs;

[0046] The translational freedom constraint is imposed on the bottom nodes of the non-settling pier, and the vertical displacement change of the settlement pier is achieved by changing the vertical freedom constraint of the node;

[0047] Prestressed steel tendons are embedded in the beam body, and both the prestressed steel tendons and shear nails are simulated using beam elements;

[0048] The track system and bridge are simulated using eight-node hexahedral elements.

[0049] In the aforementioned method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under the action of the train, in step 4, the correctness of the established train-longitudinal bridge system coupling nonlinear dynamic model is verified, specifically: using the existing bridge-rail interface contact characterization model to verify from the perspective of statics; using the existing joint simulation dynamics model to verify from the perspective of dynamics.

[0050] In the above-mentioned method for analyzing the dynamic contact characteristics of the interface of the longitudinal bridge-rail system at the side pier settlement under the action of the train, in step five, the set side pier settlement value is to set the deformation of the end of the continuous beam on the side pier to be maintained at 10mm, and the side pier settlement values ​​are 10, 20, and 30mm, and the simply supported beam on it undergoes vertical deformation with the settlement pier.

[0051] The aforementioned method for analyzing the dynamic contact characteristics of the interface of the longitudinal bridge-rail system at the settlement of the side pier under the action of the train, in step five, analyzes the dynamic change characteristics of the bridge-rail structure before, when and after the train passes through the settlement area, including analyzing the dynamic displacement changes of the bridge-rail structure along the mileage, the dynamic changes of the additional stress of the track structure and the dynamic displacement changes of the bridge-rail structure along the time before, when and after the train passes through the settlement area; analyzes the dynamic change characteristics of the connection between the bridge-rail interface layers before, when and after the train passes through the settlement area, including analyzing the dynamic connection force of the sliding layer, the dynamic connection force of the mortar and the dynamic connection force of the fasteners before, when and after the train passes through the settlement area.

[0052] Among them, the dynamic displacement changes of the bridge-track structure along the mileage before, when and after the train passes through the settlement area are analyzed, specifically, the deformation of the main beam, rails, track plates and base plates are analyzed when the side piers settle by 10mm, 20mm and 30mm; the dynamic changes of the additional stress of the track structure before, when and after the train passes through the settlement area are analyzed, specifically, the longitudinal tensile and compressive stress values ​​of the rails, track plates and base plates are analyzed before, when and after the train passes through the settlement area; the dynamic displacement changes of the bridge-track structure along the mileage are analyzed before, when and after the train passes through the settlement area, specifically, the position with the maximum deformation is selected as the reference point on the deformation curve of the bridge-track structure along the mileage, and the dynamic displacement of the rails, track plates, base plates and main beams at the reference point with the train running time is analyzed.

[0053] Analyze the dynamic connection force of the sliding layer before, during and after the train passes through the settlement area, specifically analyze the dynamic contact force changes between the bridge and rail interfaces and the dynamic gap changes of the bridge and rails when the train passes through the settlement area when the side piers settle by 10, 20, and 30 mm. Analyze the dynamic connection force of the mortar before, during and after the train passes through the settlement area, specifically analyze the dynamic force changes of the mortar along the mileage direction when the side piers settle by 10, 20, and 30 mm; analyze the dynamic connection force of the fasteners before, during and after the train passes through the settlement area, specifically analyze the dynamic force changes of the fasteners when the side piers settle by 10, 20, and 30 mm.

[0054] The beneficial effects of the present invention are as follows:

[0055] 1) The present invention, by establishing a coupled dynamic model of the dynamic contact characteristics of the interface of the longitudinal bridge-rail system at the side pier settlement taking into account the effect of the train, analyzes the dynamic displacement change characteristics of the bridge-rail structure under different states before, during and after the train passes through the settlement area, the dynamic change law of the additional stress and the dynamic change characteristics of the interlayer connection. It has been verified that the model established by the present invention and the existing bridge-rail interface contact characterization model calculate that the rail deformation and fastener force curves caused by the pier settlement are in good agreement, the local mutation of the fastener force is consistent with the rail displacement, and the error does not exceed 5%, which has good accuracy; it provides a certain theoretical basis for judging the stable and safe operation of trains on bridges and the service performance of bridges and rails.

[0056] 2) The present invention analyzes the dynamic change characteristics of the bridge track structure when the train passes through the settlement area. Among them, the dynamic deformation of the track structure is the largest, and the deformation of the track structure is basically the same before and after the train passes through the settlement area. The result of directly using the static deformation of the rails caused by the settlement of the bridge piers (when there is no train passing through the settlement area) to carry out the train running safety evaluation is relatively safe, because there is an interlayer gap area, and the dynamic deformation curve of the rails is more dangerous when the train passes. The gap height and gap length are positively correlated with the settlement value of the side pier. When the settlement value of the side pier is 18.5mm, the tensile stress of the base plate exceeds the standard limit of 2.58MPa.

[0057] 3) The dynamic change characteristics of the connection between the bridge and rail interface layers when the train passes through the settlement area are analyzed by the method of the present invention. Among them, the static effect of the side pier settlement on the dynamic connection force of the sliding layer is much greater than the dynamic effect of the train load, and the dynamic effect of the train load is much greater than the effect of the side pier settlement on the dynamic connection force of the mortar and fasteners; the side pier settlement has a dynamic amplification effect on the dynamic connection force of the sliding layer, mortar and fasteners.

[0058] 4) According to the analysis of the method of the present invention, when the side piers settle by 10, 20 and 30 mm, there are three debonding areas and contact zones at the bridge-rail interface along the mileage direction for the dynamic coupling force of the sliding layer, which are located at the settled side pier, the adjacent brake pier and the symmetrical side pier respectively; for the dynamic coupling force of the mortar, there are scattered debonding areas and contact zones, which are located at the settled pier, the adjacent brake pier and the middle position between the two brake piers respectively; for the dynamic coupling force of the fasteners, there is no debonding area.

[0059] In general, the analysis method of the present invention helps to explore the dynamic contact behavior of the bridge-rail system interface at the pier settlement under the action of the train and its impact on the dynamic performance of the train, providing strong theoretical support for ensuring the service safety of the line. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is the dynamic contact state of the interface between the longitudinal slab track and the bridge system at the settlement pier under the action of the train;

[0061] Figure 2 The train model in the train-longitudinal bridge system coupled nonlinear dynamic model established by the present invention taking into account the dynamic contact between the bridge and rail interface;

[0062] Figure 3 The wheel-rail contact model in the train-longitudinal bridge system coupled nonlinear dynamic model established by the present invention taking into account the dynamic contact between the bridge and rail interface;

[0063] Figure 4 A coupled nonlinear dynamic model of a train-longitudinal bridge system considering the dynamic contact between the bridge and rail interface established for the present invention;

[0064] Figure 5 The results of mutual verification between the train-longitudinal bridge system coupled nonlinear dynamic model considering the dynamic contact between the bridge and rail interface established by the present invention and the existing bridge and rail interface contact characterization model and the PYTHON-ANSYS-MATLAB joint simulation dynamic model;

[0065] Figure 6 The typical deformation modes of bridge rails under different side pier settlement amplitudes;

[0066] Figure 7 The dynamic displacement change of the bridge rail under the condition of 10mm settlement of the side pier in the present invention;

[0067] Figure 8 The dynamic displacement change of the bridge rail under the condition of 20mm settlement of the side pier in the present invention;

[0068] Fig. 9 The dynamic displacement change of the bridge rail under the condition of 30mm settlement of the side pier in the present invention;

[0069] Fig.10 are the longitudinal tensile and compressive stress values ​​of the track structure before, when and after the train passes through the settlement area in the present invention;

[0070] Fig.11 The vertical dynamic displacement of the track structure with the maximum deformation position as the reference point in the present invention;

[0071] Fig.12 The dynamic contact force of the bridge rail under various settlement amplitudes of the side pier in the present invention;

[0072] Fig.13 The dynamic gap change of the bridge rail under various settlement amplitudes of the side pier in the present invention;

[0073] Fig.14 is the change of mortar dynamic force under various settlement amplitudes of the side pier in the present invention;

[0074] Fig.15 It is the change of dynamic force of fasteners under various settlement amplitudes of the side pier in the present invention. DETAILED DESCRIPTION

[0075] The following will be combined with the embodiments and drawings to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only preferred embodiments of the present invention, not all embodiments, and are not intended to limit the present invention in other forms. Any technician familiar with the profession may use the disclosed technical content to make changes or modifications. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

[0076] The specific embodiments are as follows:

[0077] This embodiment is a method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train. The method establishes a coupled nonlinear dynamic model of the train-longitudinal bridge system that takes into account the dynamic contact of the bridge-rail interface; calculates the wheel-rail normal force and wheel-rail tangential force in the model based on the established model and relevant wheel-rail contact theory; and assembles the coupled nonlinear dynamic model of the train-longitudinal bridge system based on the actual connection characteristics and contact relationship between the layers of the train-longitudinal bridge system; then uses the existing joint simulation dynamic model to verify the correctness of the established coupled nonlinear dynamic model of the train-longitudinal bridge system; finally, sets the side pier settlement value, and analyzes the dynamic change characteristics of the bridge-rail structure and the dynamic change characteristics of the connection between the bridge-rail interface layers before, during, and after the train passes through the settlement area. The details are as follows:

[0078] 1. Establish a coupled nonlinear dynamic model of the train-longitudinal bridge system considering the dynamic contact between the bridge and track interface

[0079] 1) Train model

[0080] In this implementation, the train is simulated by CRH380A EMU train. A single train consists of a car body, two bogies, and four wheel sets. The train body, bogies, and wheel sets are considered as rigid bodies. Figure 2 As shown, the remaining parameters of the train can adopt the existing technology.

[0081] Set the car body unit properties to discrete solid units and convert them into shell units, the bogie to discrete rigid body tensile units, and the wheelset to analytical rigid body rotational shell units.

[0082] The wheels are connected to the bogie by a primary suspension, and the bogie is connected to the car body by a secondary suspension. In the ABAQUS simulation software, "Cartesian" connectors are used to consider linear springs and damping, and the wheel tread adopts LM A Wear-type tread.

[0083] 2) Wheel-Rail Contact Theory

[0084] (1) Wheel-rail normal force

[0085] The wheel-rail normal contact adopts HERTZ nonlinear elastic contact, such as Figure 3 As shown, the theoretical calculation is as follows:

[0086]

[0087] Where:

[0088] p(t)—wheel-rail normal force (N),

[0089] G—wheel-rail contact constant (m / N 3 / 2 ),

[0090] △Z(t)—elastic compression between wheel and track (m),

[0091] t—time(s).

[0092] The elastic compression between the wheel and the rail, △Z(t), represents the relative displacement between the wheel and the rail at the wheel-rail contact point and is expressed as:

[0093] △Z(t)=Z wj (t)-Z r (x rj ,t) (2)

[0094] Where:

[0095] w—wheel,

[0096] j—wheel position,

[0097] r—rail,

[0098] Z wj (t)—displacement of the j-th wheel at time t (m);

[0099] Z r (x rj ,t)—the order is the displacement of the rail under the j-th wheel at time t (m), t=1, 2, 3, 4.

[0100] When △Z(t)<0, the wheel is out of contact with the rail, and the wheel-rail force (wheel-rail normal force) p(t)=0. Assume that the wheel displacement at the contact surface is Z 0 (t), then the wheel-rail force expression is:

[0101]

[0102] Since the wheel tread in this embodiment adopts LMA wear type tread, G = 3.86R -0.115 ×10 -8 , R is the wheel radius. In the ABAQUS finite element simulation software, pressure interference is used to define the rigid wheelset as the primary contact surface and the deformable rail as the secondary contact surface.

[0103] (2) Wheel-rail tangential force

[0104] When relative sliding occurs between the wheel and the rail, relative sliding friction is generated on the contact surface. When the wheel-rail contact state is relative sliding, the friction coefficient decays exponentially with the relative sliding rate between the wheel and the rail. Therefore, the wheel-rail tangential force can be determined by the normal force and the friction coefficient, and its expression is:

[0105] F=p(t)×μ

[0106] Where:

[0107] μ—friction coefficient,

[0108] F—wheel-rail tangential force (N),

[0109] p(t)—wheel-rail normal force (N);

[0110] In this embodiment, the vehicle moving speed is always set to a uniform state, so the friction coefficient μ is a constant value, which is set to 0.3 in the ABAQUS simulation software.

[0111] 2. Assembly of the train-longitudinal bridge system coupling model

[0112] like Figure 4 According to the actual connection characteristics and contact relationship between the layers of the line bridge system, since the sleepers and track slabs are cast in one piece and are tightly connected, the sleepers and track slabs are constrained by surface-to-surface TIE contact.

[0113] The CA mortar layer and WJ-8 rail fasteners were simulated using linear springs;

[0114] The contact between the base plate and the sliding layer takes into account the effect of interlayer delamination, so a nonlinear spring that is only compressed but not tensile is used for simulation;

[0115] The sliding layer and the bridge deck adopt surface-to-surface TIE contact;

[0116] In order to limit the degrees of freedom at both ends of the bridge and track, consolidation constraints are imposed at the ends of the bridge and track in the non-settlement area, and the supports between the piers and the beams are simulated by springs;

[0117] The bridge pier is connected to the foundation, and the translational freedom constraint is applied to the bottom node of the non-settling pier. In order to realize the vertical displacement change of the settling pier, the vertical freedom constraint of the node is changed in different analysis steps;

[0118] Prestressed steel tendons are embedded in the beam body. Both the prestressed steel tendons and shear studs are simulated using B31 beam elements. The track system and bridge are simulated using eight-node hexahedral elements C3D8R. The remaining structural material parameters can use existing technologies.

[0119] 3. Model Validation

[0120] In this embodiment, the bridge-rail interface contact characterization model developed in the early stage is used to verify the established train-longitudinal bridge system coupling nonlinear dynamic model from the perspective of statics; at the same time, the PYTHON-ANSYS-MATLAB joint simulation dynamic model developed in the early stage is used to verify the established train-longitudinal bridge system coupling nonlinear dynamic model from the perspective of dynamics. The results are as follows: Figure 5 As shown; Figure 5 (a) is the angle verification result of statics, Figure 5 (b) is the verification result from the perspective of dynamics.

[0121] Depend on Figure 5 It is known that the rail deformation and fastener force curves caused by pier settlement calculated by the train-longitudinal connection bridge system coupled nonlinear dynamic model (finite element model) established in this embodiment and the bridge-rail interface contact characterization model (analytical model) are in good agreement, and the local mutation of the fastener force is consistent with the rail deformation, and the error does not exceed 5%; compared with the existing joint simulation dynamic model (analytical model), the error is within a reasonable range, which verifies the correctness of the model (finite element model) of this embodiment.

[0122] 4. Analyze the dynamic change characteristics of the bridge-track structure and the dynamic change characteristics of the bridge-track interface layer connection

[0123] The high-speed railway design specification (TB 10621-2014) stipulates that the maximum deformation of the self-weight of the continuous beam bridge shall not exceed 10mm. Therefore, the deformation of the end of the continuous beam on the left pier (3# pier) is maintained at 10mm. The settlement values ​​of the left pier are 10, 20, and 30mm, and the simply supported beam on it undergoes vertical deformation with the settlement pier. Based on this, the dynamic displacement change characteristics of the bridge track structure before, during, and after the train passes through the settlement area, the dynamic change law of additional stress, and the dynamic change characteristics of the interlayer connection are analyzed. When the settlement value of the side pier is 10mm, the deformation value of the continuous beam is the same as that of the simply supported beam, forming the following Figure 6 (a) shows the deformation mode, and when the side pier settlement increases, the following Figure 6 (b) The deformation mode shown.

[0124] 1) Dynamic change characteristics of bridge track structure

[0125] (1) Dynamic displacement changes of bridge track structures along the mileage

[0126] In the ABAQUS tool set, set the node set with the same vertical position, then create the U2 vertical displacement of the node set in the analysis step-process output, and finally extract the vertical displacement data of the node set in the ABAQUS post-process output, such as Figures 7 to 9 As shown in and , when the train passes through the settlement area, the dynamic deformation of the rails, track plates and base plates is the largest, and the deformation of the track structure is basically the same before and after the train passes through the settlement area.

[0127] When the settlement of the side pier and the deformation of the continuous beam are both 10mm, the maximum deformation position of the rail, track plate and base plate is at the settlement pier. When the settlement value of the side pier continues to increase, the longitudinal connection characteristics of the track structure cause the maximum deformation value to move to the left, showing a "concave" deformation, a "breaking point" appears at the position of the settlement pier, and an "upward arch" deformation appears on the right side, which is quite different from the settlement value of the side pier, resulting in a large gap. The reason is that when the train passes through the settlement area, the left end of the continuous beam acts as a "fulcrum", which increases the "concave" value and the "upward arch" value accordingly.

[0128] At present, the study on the influence of pier settlement on the vehicle-line-bridge system directly uses the rail deformation caused by pier settlement as the additional static irregularity (when there is no train passing through the settlement area), and then inputs it into the vehicle-bridge coupling dynamics program to evaluate the train running safety. It can be seen that the calculation results of the additional static irregularity selected in the past are biased towards safety, because there is an interlayer gap area, and the rail deformation curve caused by pier settlement is more dangerous when the train passes.

[0129] Table 1 The length and height of the gap between the bridge and rail before, when and after the train passes through the settlement area

[0130]

[0131] It can be seen from Table 1 that the gap height and gap length are positively correlated with the side pier settlement value. The gap length and height are reduced when the train passes by. After the train passes by, the gap length and height appear again, but they fail to reach the values ​​before the train passes by. This process forms a dynamic contact process of the bridge-rail interface of "gap-close-again gap".

[0132] (2) Dynamic changes of additional stress in track structure

[0133] In the ABAQUS analysis step-field output, the S (stress) output request of the model is set, and the S11 (transverse stress) and S33 (longitudinal stress) of each track structure are extracted in the ABAQUS post-processing. The results are as follows: Fig.10 As shown in the figure, the longitudinal tensile and compressive stresses of the rails, track plates and base plates are quite different before and when the train passes through the settlement area, but not much different before and after passing. This is because after the vehicle passes, the track structure will "rebound" back to the position close to the original side pier settlement under the action of its own bending stiffness; the tensile and compressive stresses of the rails, track plates and base plates increase with the increase of the side pier settlement value. Since the rails are in direct contact with the wheelset and the force-bearing area is smaller than that of the track plates and base plates, the longitudinal tensile and compressive stresses of the rails are the largest; when the side pier settlement value is 18.5mm, the tensile stress of the base plate exceeds the limit of 2.58MPa specified in the specification, and when the side pier settlement amplitude is 28.5mm, the longitudinal tensile stress of the track plate will exceed the limit.

[0134] (3) Changes in dynamic displacement of bridge track structure over time

[0135] The maximum deformation position is selected as the reference point on the bridge track structure along the mileage deformation curve, and the dynamic displacement of the rail, track plate, base plate and main beam at the reference point with the train running time is extracted. In ABAQUS, a node set is created in the tool-set, and each track structure reference point is selected as a set, and then the U2-vertical displacement of the node set is created in the analysis step-process output, and finally the vertical displacement data of the node set is extracted in the ABAQUS post-processing-process output.

[0136] Results, such as Fig.11 As shown in the figure, since the front and rear wheel pairs of the train pass through the reference point in sequence during operation, and rebound occurs after the first two wheel pairs of the train pass through, the vertical displacements of the rails, track plates, and base plates all show "double peak values". When the settlement value of the side pier is equal to the deformation of the continuous beam by self-weight of 10mm, the base plate is relatively small at this time. When the train passes by, the two wheel pairs on the same bogie pass through the reference point on the rail in sequence, and the vertical displacement rebounds. When the settlement value of the side pier is greater than the deformation of the continuous beam, the base plate is relatively large, and the vertical displacement rebound of the reference point on the rail becomes less obvious. As the settlement value of the side pier increases, the dynamic displacement values ​​of the rails, track plates, and base plates also increase accordingly.

[0137] 2) Dynamic characteristics of the connection between bridge and track interfaces

[0138] (1) Dynamic coupling force of sliding layer

[0139] First, in ABAQUS, set the geometric node set at the same lateral position of the sliding layer spring in Tools-Center, then set the process output-connection-CTF2 (resultant force and moment), and finally extract the spring force data in ABAQUS post-processing-process output. Fig.12 and Fig.13 The following are cloud diagrams of dynamic contact force changes between the bridge and rail interfaces and bottom projection cloud diagrams when the train passes through the settlement area when the side piers settle by 10, 20, and 30 mm. The white area indicates that the deformation of the two is not coordinated, resulting in a gap, and the colored part indicates contact, and the darker the color, the greater the contact force.

[0140] Depend on Fig.12It can be seen that the static effect of the side pier settlement on the dynamic coupling force of the sliding layer is much greater than the dynamic effect of the train load. The bridge-rail contact force under the action of the train alone is about 5kN. When the train passes through the settlement, the dynamic amplification effect of the four wheel sets can be clearly seen. The settlement and the train jointly cause the bridge-rail contact force, indicating that the train load will further put it on the local stress concentration caused by the settlement, deteriorating the contact performance of the bridge and the track; when the side pier settlement is equal to the continuous beam deformation, the maximum dynamic coupling force of the sliding layer is at the 2# pier, and when the side pier settlement value is greater than the continuous beam deformation, the maximum dynamic coupling force of the sliding layer is at the 3# pier; the void area is concentrated at the 2#, 3# and 6# piers. Before the vehicle drives, the void value at the 3# pier is the largest, followed by the 2# pier, and the minimum void value is at the 6# pier.

[0141] Depend on Fig.13 It can be seen that when the side pier settlement is 10, 20, and 30 mm, there are three bridge-rail interface void areas and contact zones along the mileage direction, namely, at the settled side pier, the adjacent brake pier, and the symmetrical side pier.

[0142] (2) Dynamic bonding force of mortar

[0143] First, in ABAQUS, set the geometric node set at the same lateral position of the mortar spring in Tools-Center, then set the process output-connection-CTF2 (resultant force and moment), and finally extract the spring force data in ABAQUS post-processing-process output. The results are as follows: Fig.14 As shown in the figure, it can be seen that the dynamic effect of the train load is much greater than the static effect of the side pier settlement on the dynamic coupling force of the mortar, which is different from the dynamic coupling force of the sliding layer. Taking the settlement of 30mm as the research object, it can be seen that the train load transmitted from top to bottom is about 5kN, and the pier settlement effect transmitted from bottom to top is reflected in the mortar connection at a maximum of about 3.5kN. When the train passes through the settlement area, the amplification effect of the pier settlement on the train load reaches 6.5kN. When the side pier settlement is 10, 20, and 30mm, scattered void areas and contact zones appear along the mileage direction, respectively in the settlement pier, the adjacent brake pier, and the middle of the two brake piers.

[0144] (3) Dynamic connection force of fasteners

[0145] First, in ABAQUS, set the geometric node set at the same lateral position of the fastener spring in Tools-Center, then set the process output-Connection-CTF2 (resultant force and moment), and finally extract the spring force data in ABAQUS post-processing-process output (see the results). Fig.15 ),Depend on Fig.15It can be seen that the dynamic effect of the train load is much greater than the static effect of the side pier settlement on the fastener, which is the same as the mortar connection force. When the vehicle is traveling in the non-settlement area, the dynamic connection force of the fastener is about 13kN, while when the vehicle is traveling in the settlement area, the dynamic connection force of the fastener changes suddenly and increases with the increase of the side pier settlement value. When the side pier settles 30mm, the maximum dynamic connection force of the fastener at the 3# pier position is about 23kN, which is nearly 11 times higher than the 2.1kN in the static state. It can be seen that the train wheels have an obvious dynamic amplification effect. When the side pier settles 10-30mm, the amplification effect is 23%, 38%, and 77% respectively, and the growth slope is the largest between the settlement of 20 and 30mm.

[0146] The rail deformation and fastener force curves caused by pier settlement calculated by the model of the present invention and the bridge-rail interface contact characterization model are in good agreement. The local mutation of the fastener force is consistent with the rail displacement, and the error does not exceed 5%. Compared with the existing joint simulation dynamics model, the error is within a reasonable range, which verifies the correctness of the invented model. According to the analysis of the method of the present invention, when the train passes through the settlement area, the dynamic deformation of the track structure is the largest, and the deformation of the track structure is basically the same before and after the train passes through the settlement area. The results of the train running safety evaluation directly using the static deformation of the rail caused by the settlement of the pier (when there is no train passing through the settlement area) are relatively safe, because there is an interlayer gap area, and the dynamic deformation curve of the rail is more dangerous when the train passes. The gap height and gap length are positively correlated with the settlement value of the side pier. When the settlement value of the side pier is 18.5mm, the tensile stress of the base plate exceeds the standard limit of 2.58MPa. The static effect of the side pier settlement on the dynamic connection force of the sliding layer is much greater than the dynamic effect of the train load, and the dynamic effect of the train load is much greater than the effect of the side pier settlement on the dynamic connection force of the mortar and fasteners; the side pier settlement has a dynamic amplification effect on the dynamic connection force of the sliding layer, mortar and fasteners; when the side pier settlement is 10, 20, and 30 mm, there are three positions of bridge-rail interface debonding areas and contact zones along the mileage direction for the dynamic connection force of the sliding layer, which are respectively at the settlement side pier, the adjacent brake pier and the symmetrical side pier; for the dynamic connection force of the mortar, there are scattered debonding areas and contact zones, which are respectively at the settlement pier, the adjacent brake pier and the middle position between the two brake piers; for the dynamic connection force of the fastener, there is no debonding area. In summary, the method of the present invention provides an effective research scheme for exploring the dynamic contact behavior of the bridge-rail system interface at the pier settlement under the action of the train and its influence on the dynamic performance of the train, and provides strong theoretical support for ensuring the service safety of the line.

[0147] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view. In addition, it should be understood that although this specification is described in accordance with the embodiments, it does not contain only one technical solution. This narrative of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for analyzing the dynamic contact characteristics of the longitudinal bridge-rail system interface at the side pier settlement under train action. Features: The steps include: Step 1: Establish a coupled nonlinear dynamic model of the train-longitudinal bridge system considering the dynamic contact between the bridge and track interface; Step 2: Calculate the wheel-rail normal force and wheel-rail tangential force based on the established model and relevant wheel-rail contact theory; Step 3: According to the actual connection characteristics and contact relationship between the layers of the train-longitudinal bridge system, assemble the coupled nonlinear dynamic model of the train-longitudinal bridge system; Step 4: Use the existing dynamic model to verify the correctness of the established train-longitudinal bridge system coupled nonlinear dynamic model; Step 5: Set the side pier settlement value, and analyze the dynamic change characteristics of the bridge-rail structure and the dynamic change characteristics of the bridge-rail interface layer connection before, when and after the train passes through the settlement area; in: In step 3, the assembly train-longitudinal bridge system coupled nonlinear dynamic model is specifically as follows: The sleeper and track slab are constrained by surface-to-surface TIE contact; The CA mortar layer and rail fasteners are simulated using linear springs; The contact between the base plate and the sliding layer is simulated by a nonlinear spring that is only compressed but not tensile; The sliding layer and the bridge deck adopt surface-to-surface TIE contact; Consolidation constraints are imposed on the bridge and track end positions in non-settlement areas, and the supports between the bridge piers and the beams are simulated by springs; The translational freedom constraint is imposed on the bottom nodes of the non-settling pier, and the vertical displacement change of the settlement pier is achieved by changing the vertical freedom constraint of the node; Prestressed steel tendons are embedded in the beam body, and both the prestressed steel tendons and shear nails are simulated using beam elements; The track system and bridge are simulated using eight-node hexahedral elements; In step five, Analyze the dynamic change characteristics of the bridge-track structure before, when and after the train passes through the settlement area, including the analysis of the dynamic displacement changes of the bridge-track structure along the mileage, the dynamic changes of the additional stress of the track structure and the dynamic displacement changes of the bridge-track structure along the time before, when and after the train passes through the settlement area; The dynamic change characteristics of the connection between the bridge and rail interface layers before, when and after the train passes through the settlement area are analyzed, including the dynamic connection force of the sliding layer, the dynamic connection force of the mortar and the dynamic connection force of the fasteners before, when and after the train passes through the settlement area.

2. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train according to claim 1, Features: In step 1, the established train-longitudinal bridge system coupled nonlinear dynamic model is a CRH380A EMU train; Its single train consists of a car body, two bogies, and four wheel sets, and the train body, bogies, and wheel sets are all rigid bodies; The train and bogie consider five degrees of freedom: heave, sway, roll, nod and shake; the wheelset considers two degrees of freedom: sway and shake. Set the car body unit properties to discrete solid units and convert them to shell units, the bogie to discrete rigid body tensile units, and the wheelset to analytical rigid body rotational shell units; The wheels and bogies are connected by a primary suspension, and the bogies and the car body are connected by a secondary suspension. Linear springs and damping Cartesian connectors are used in the ABAQUS simulation software, and the wheel tread adopts the LMA wear-type tread.

3. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train according to claim 1, Features: In step 2, the wheel-rail normal force and wheel-rail tangential force are calculated, where: The wheel-rail normal contact adopts HERTZ nonlinear elastic contact, and its normal force is calculated as follows: Where: p(t)—wheel-rail normal force (N), G—wheel-rail contact constant (m / N3 / 2), ΔZ(t)—elastic compression between wheel and track (m), t—time (s); The wheel-rail tangential force is determined by the wheel-rail normal force and the friction coefficient, and its expression is: F = p(t) × μ; Where: μ—friction coefficient, F—wheel-rail tangential force (N), p(t)—wheel-rail normal force (N).

4. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of the train according to claim 3, Features: The elastic compression ΔZ(t) between the wheel and the rail represents the relative displacement between the wheel and the rail at the wheel-rail contact point, and its specific calculation formula is: ΔZ(t)=Z wj (t)-Z r (x rj ,t); Where: w—wheel, j—wheel position, r - for rails, Z wj (t)—displacement of the j-th wheel at time t (m), Z r (x rj ,t)—the order is the displacement of the rail under the j-th wheel at time t (m), t=1, 2, 3, 4; When ΔZ(t)<0, that is, when the wheel is out of contact with the rail, the wheel-rail normal force p(t)=0; Assume that the wheel displacement at the contact surface is Z 0 (t), then the wheel-rail normal force expression is: Where: G = 3.86R -0.115 ×10 -8 , R is the wheel radius.

5. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train according to claim 1, Features: In step 4, the correctness of the established train-longitudinal line bridge system coupled nonlinear dynamic model is verified, specifically: using the existing bridge-rail interface contact characterization model to verify from the perspective of statics; using the existing joint simulation dynamics model to verify from the perspective of dynamics.

6. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train according to claim 1, Features: In step five, the side pier settlement value is set to maintain the deformation of the end of the continuous beam on the side pier at 10mm. The side pier settlement values ​​are 10, 20, and 30mm, and the simply supported beam on it undergoes vertical deformation along with the settlement pier.

7. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train according to claim 1, Features: Analyze the dynamic displacement changes of the bridge track structure before, during and after the train passes through the settlement area, specifically analyze the deformation of the main beam, rails, track plates and base plates when the side piers settle by 10mm, 20mm and 30mm; Analyze the dynamic changes of additional stress in the track structure before, when and after the train passes through the settlement area, specifically, analyze the longitudinal tensile and compressive stress values ​​of the rails, track plates and base plates before, when and after the train passes through the settlement area; The dynamic displacement changes of the bridge-track structure before, when and after the train passes through the settlement area are analyzed. Specifically, the position with the maximum deformation along the mileage deformation curve of the bridge-track structure is selected as the reference point, and the dynamic displacement of the rails, track plates, base plates and main beams at the reference point with the running time of the train is analyzed.

8. The dynamic contact characteristics analysis method of the longitudinal bridge-rail system interface at the side pier settlement under the action of a train according to claim 1, Features: Analyze the dynamic connection force of the sliding layer before, during and after the train passes through the settlement area. Specifically, analyze the changes in the dynamic contact force between the bridge and rail interfaces and the dynamic gap between the bridge and rails when the train passes through the settlement area when the side piers settle by 10, 20 and 30 mm. Analyze the dynamic connection force of mortar before, during and after the train passes through the settlement area. Specifically, analyze the side pier settlement of 10, 20 and 30 mm. Changes in mortar dynamic forces along the mileage direction; Analyze the dynamic coupling force of fasteners before, during and after the train passes through the settlement area. Specifically, analyze the side pier settlement of 10, 20 and 30 mm. Dynamic force changes of fasteners.

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