Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions, which may cause the amplification and de-amplification of input seismic waves. The topographic effect with the assumption of plane seismic waves on the seismic responses of bridges has been investigated in the existing literature; however, the influence of near-source topographic effects has not been thoroughly understood. The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon. The influence of the source of incident waves is estimated. Numerical results demonstrate that the topographic effects can noticeably amplify the seismic responses of the bridge. Compared to the bridge without crossing a canyon, the peak displacements of the girder, pier, and bearing in the case of the canyon-crossing bridge increase by 15.2%, 2.9%–14.5%, and 24.2%–229.6%, respectively. The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support. As the source-to-canyon distance increases, the seismic responses of the piers show an increasing trend.

Bridges crossing active faults are more likely to suffer serious damage or even collapse due to the wreck capabilities of near-fault pulses and surface ruptures under earthquakes. Taking a high-speed railway simply-supported girder bridge with eight spans crossing an active strike-slip fault as the research object, a refined coupling dynamic model of the high-speed train-CRTS III slab ballastless track-bridge system was established based on ABAQUS. The rationality of the established model was thoroughly discussed. The horizontal ground motions in a fault rupture zone were simulated and transient dynamic analyses of the high-speed train-track-bridge coupling system under 3-dimensional seismic excitations were subsequently performed. The safe running speed limits of a high-speed train under different earthquake levels (frequent occurrence, design and rare occurrence) were assessed based on wheel-rail dynamic (lateral wheel-rail force, derailment coefficient and wheel-load reduction rate) and rail deformation (rail dislocation, parallel turning angle and turning angle) indicators. Parameter optimization was then investigated in terms of the rail fastener stiffness and isolation layer friction coefficient. Results of the wheel-rail dynamic indicators demonstrate the safe running speed limits for the high-speed train to be approximately 200 km/h and 80 km/h under frequent and design earthquakes, while the train is unable to run safely under rare earthquakes. In addition, the rail deformations under frequent, design and rare earthquakes meet the safe running requirements of the high-speed train for the speeds of 250, 100 and 50 km/h, respectively. The speed limits determined for the wheel-rail dynamic indicators are lower due to the complex coupling effect of the train-track-bridge system under track irregularity. The running safety of the train was improved by increasing the fastener stiffness and isolation layer friction coefficient. At the rail fastener lateral stiffness of 60 kN/mm and isolation layer friction coefficients of 0.9 and 0.8, respectively, the safe running speed limits of the high-speed train increased to 250 km/h and 100 km/h under frequent and design earthquakes, respectively.

Earthquake is a kind of sudden and destructive random excitation in nature. It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation, the intensity of which is larger than 7, acts in train-bridge system. Firstly, the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established, where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom, while the single-span simple supported bridge subsystem is composed of 10 2D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support. Secondly, Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system. The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method, respectively solved by precise integral method and Newmark-β method through the inter-system iterative procedure. Finally, the results are compared with the case under the weak seismic excitation, and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution. In a high probability, the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.

China’s high-speed railways are always facing the potential damage risk induced by strong earthquakes. And the route design concept of “using bridge instead of embankment” has also greatly increased the probability of highspeed trains moving on bridges when a strong earthquake happens. In the past decades, a bunch of theoretical and numerical studies have been conducted in the seismic dynamic field of high-speed railway. However, the effective dynamic test system for verifying the given method and theoretical results is still lacking. Therefore, a novel dynamic test system (DTS) consisting of a shaking table array and a train-pass-bridge reduced-scale model is proposed in this paper. Through some crucial technical problems discussion, the effectiveness of similar design scheme and the feasibility of reduced-scale DTS are elaborated, and then the detailed DTS structures are given and displayed as part-by-part. On this basis, the demonstration tests are conducted and compared with the numerical simulation. The results show that the proposed DTS is accurate and effective. Therefore, the DTS can provide a new physical simulation approach to study the high-speed train’s running safety on bridges under earthquakes and can also provide a reference for the construction of related systems.

The comparative research on the seismic performance of grouted sleeve connected pier (GS) and prestressed precast segmental concrete pier (PC) is mostly carried out by numerical simulation. In this study, the GS pier and the PC pier of the new railway project from Hetian to Ruoqiang are taken into consideration. Two kinds of 1/5-scale assembled double-column specimens are made, and the quasi-static tests are carried out. The overall seismic performance of the two spliced piers is studied, and compared in terms of failure mechanism, bearing capacity, ductility, stiffness and energy dissipation capacity. The results show that the failure modes of both GS pier and PC pier are characterized by bending. However, the specific failure location and form are different. The GS pier presents a complete hysteretic curve, large equivalent stiffness and strong energy dissipation capacity. The hysteretic area of the PC pier is small. However, it has good self-reset ability and quasi-static residual displacement. Finite element models are set up using DispBeamColumn fiber elements and ZeroLength elements. The models that are calibrated with the test data can effectively simulate the damage development under monotonic loading. The load—displacement curves are in good agreement with the backbone curves of the test results.

In recent years, the safety and comfort of road vehicles driving on bridges under crosswinds have attracted more attention due to frequent occurrences of wind-induced disasters. This study focuses on a container truck and CRH2 high-speed train as research targets. Wind tunnel experiments are performed to investigate shielding effects of trains on aerodynamic characteristics of trucks. The results show that aerodynamic interference between trains and trucks varies with positions of trains (upstream, downstream) and trucks (upwind, downwind) and numbers of trains. To summarize, whether the train is upstream or downstream of tracks has basically no effect on aerodynamic forces, other than moments, of a truck driving on windward sides of bridges (upwind). In contrast, the presence of trains on the bridge deck has a significant impact on aerodynamic characteristics of a truck driving on leeward sides (downwind) at the same time. The best shielding effect on lateral forces of trucks occurs when the train is located downstream of tracks. Finally, the pressure measuring system shows that only lift forces on trains are affected by trucks, while other forces and moments are primarily affected by adjacent trains.

Wind tunnel tests were carried out to investigate the aerodynamic interference between a triple-box girder and trains, involving static aerodynamic forces and vortex-induced vibrations (VIVs). Static and dynamic sectional models of the girder and trains were employed for aerodynamic force measurement and VIV test, respectively. Results indicate that the aerodynamic interference effect on static aerodynamic forces of both the girder and trains is remarkable. When a single train exists, the horizontal position of the train has a small effect on aerodynamic coefficients of the girder. When two trains meet on the girder, the drag coefficient of the girder is significantly reduced compared with that of without train or with a single train; besides, during the whole meeting process, aerodynamic forces of the leeward train first drop and then increase suddenly. The fluctuation of aerodynamic force could cause redundant vibration of the train, which is unfavorable for safety and comfort. A train on the girder could worsen the girder VIV performance: a new vertical VIV appears in the triple-box girder when a train is on the girder, and the torsional VIV amplitude increases significantly when the train is on the windward side.

An isolated slit was placed in a single box girder to obtain passive leading-edge suction and trailing-edge jet flow to control the unsteady aerodynamic force and modify the flow structure. The Great Belt East Bridge was used as a physical model at a geometric scale of 1:125. Wind tunnel experiments were conducted at an incoming airflow speed of 10 m/s, and the Reynolds number was calculated as 2.3×10⁴ using the test model height and wind speed. The surface pressure distribution was measured, and the aerodynamic force acting on the test model with and without the isolated slit was calculated by integrating the pressure result. It was found that the control using an isolated slit can dramatically decrease the fluctuating surface pressure distribution and aerodynamic force. An analysis on the power spectral density of the lift force revealed that the isolated slit accelerated vortex shedding. Moreover, high-speed particle image velocimetry was used to investigate the wake flow structure behind the test model. A vortex separated from the upper surface was pushed to a lower location and the wake flow structure was modified by the isolated slit. A proper orthogonal decomposition (POD) of the flow field showed that the first two POD modes in the controlled case contributed less energy than those in the uncontrolled case, indicating that more energy was transferred to higher modes, and small-scale vortices had more energy. A secondary instability structure was found in the wake flow for a nondimensional jet momentum coefficient J of 0.0667.

Two trains passing each other is controlling factor for the wind-vehicle-bridge systems. To test the aerodynamic characteristics of moving vehicles under crosswinds when two trains are passing each other, a wind tunnel test device, which has two moving tracks, was developed. The rationality of the test result was discussed, the effects of intersection mode, yaw angle and lane spacing on the aerodynamic coefficients of the leeward train were analyzed, and the difference of aerodynamic coefficients between the head vehicle and the tail vehicle was discussed. The results show that the proposed test device has good repeatability. The intersection modes have a certain effect on the aerodynamic force of the leeward train when two trains are passing each other, and the results should be more reasonable during the two trains dynamic passing each other. With the decrease of yaw angle, the sudden change of train aerodynamic coefficients is more obvious. The decrease of lane spacing will increase the sudden change of leeward vehicles. In the process of two trains passing each other, the aerodynamic coefficients of the head vehicle and tail vehicle are significantly different, so the coupling vibration analysis of wind-vehicle-bridge system should be considered separately.

The buffeting performance of kilometer-level high-speed railway suspension bridges has a great impact on the smooth operation of high-speed trains. To investigate the buffeting performance of the structure significantly different from traditional suspension bridges, the first long-span high-speed railway suspension bridge, Wufengshan Yangtze River Bridge (WYRB), is taken as a numerical example to demonstrate the effects of structural parameters and wind field parameters on the buffeting responses. Based on the design information, the spatial finite element model (FEM) of WYRB is established before testing its accuracy. The fluctuating wind fields are simulated via both classical and stochastic wave based spectral representation method (SRM). Finite element method is further taken to analyze the parametric sensitivity on wind induced buffeting responses in time domain. The results show that the vertical displacement is more sensitive to the changing dead load than the lateral and torsional ones. The larger stiffness of the main girder and the lower sag-to-span ratio are both helpful to reduce the buffeting responses. Wind spectrum and coherence function are key influencing factors to the responses so setting proper wind field parameters are essential in the wind-resistant design stage. The analytical results can provide references for wind resistance analysis and selection of structural and fluctuating wind field parameters for similar long-span high-speed railway suspension bridges.

The present study numerically explored the aerodynamic performance of a novel railway tunnel with a partially reduced cross-section. The impact of the reduction rate of the tunnel cross-section on wave transmissions was analyzed based on the three-dimensional, unsteady, compressible, and RNG k−ε turbulence model. The results highlight that the reduction rate (S) most affects pressure configurations at the middle tunnel segment, followed by the enlarged segments near access, and finally the exit. The strength of the newly generated compression wave at the tunnel junction where the cross-section abruptly changes increases exponentially with the decrease of the cross-sectional area. The maximum peak-to-peak pressure ΔP on the tunnel and train surface for non-uniform tunnels is reduced by 10.7% and 13.8%, respectively, compared with those of equivalent uniform tunnels. Overall, the economic analysis suggests that the aerodynamic performance of the developed tunnel prototype surpasses those conventional tunnels based on the same excavated volume.

In order to study the safety and the comfort of high-speed trains running on a single-tower cable-stayed bridge under spatial gust, a dynamic model of wind-train-bridge analysis model is built based on the autoregressive method, the multi-body dynamics method and the finite element method. On this basis, the influence of spatial gust model loading, the suspension parameters change, wind attack angle and speed on the train-bridge system are analyzed by combining the time/frequency domain analysis and statistical methods. The results show that the spatial gust environment is one of the most important factors affecting safety and comfort and can make the calculation result tend to be conservative and more conducive. The response changes caused by K_py, K_px and K_sx changes are nearly linear, while K_sy shows nonlinear characteristics and the most sensitivity. Wind attack angle at 75° and 90°has the greatest influence on the vehicle-bridge system. For ride comfort index, when pre-set wind speed (α=75°) reaches 20 m/s, the vertical acceleration firstly exceeds the limit value;when wind speed (α=90°) reaches 21.5 m/s, the lateral acceleration firstly exceeds the limit value, and the ride comfort of the vehicle cannot be guaranteed. For running safety index, when pre-set wind speed (α=75°) reaches 24.6 m/s, the wheel unloading coefficient firstly exceeds the limit;when pre-set wind speed (α=90°) reaches 24.5 m/s, the derailment coefficient firstly exceeds the limit, and the running safety cannot be guaranteed. The results can provide a suitable reference for the safe and stable operation of trains on the bridge.

To investigate the effects of sudden change in wind loads on the running performance of trains on the bridge in crosswinds, a highway-railway one-story bridge was taken as the research object. Aerodynamic coefficients of the train and the bridge were measured in a series of train-bridge system segment models through wind tunnel tests when two trains passed each other on the bridge and when a train entered and left the wind barrier section of the bridge. Based on the improved SIMPACK and ANSYS rigid-flexible coupling simulation method, a wind-double train-track-bridge system coupled vibration model was established. The dynamic responses of the train were analyzed under the effects of sudden change in wind loads caused by two trains passing each other and a train entering and leaving the wind barrier section of the bridge. The results show that the effects of sudden wind load change caused by the trains passing each other had less effects on the running safety of the leeward-side train than the wind shielding effect caused by the windward-side train in the wind speed range of 10–25 m/s. With the decrease in the porosity of wind barriers, the effects of the sudden wind load change played an increasingly important role in the running safety and comfort of the train. With the increase in wind speed, the lateral response of the train increased obviously because of the effects of sudden wind load change, which affects both the lateral running stability and the comfort of the train.

Pressure waves induced by high-speed trains passing through a tunnel have adverse effects on train structures and passenger comfort. These adverse effects can be alleviated when the train passing through the tunnel with a speed mode of deceleration. Thus, to investigate the effect of speed modes on pressure waves, three-dimensional compressible unsteady Reynolds-averaged Navier —Stokes simulations and the sliding mesh are used to simulate pressure waves on train surfaces and tunnel walls when trains passing through a tunnel with three different speed modes (a constant speed at 350 km/h, a uniform deceleration from 350 to 300 km/h, and another uniform deceleration from 350 to 250 km/h). Compared with the constant speed, the peak-to-peak of the train surface pressure under the other two speed modes reaches a maximum difference of 11.0%. The maximum positive pressure difference of the tunnel wall under different speed modes is caused by the different attenuation of the friction effect when the train enters the tunnel, and the maximum difference is 12.8%. The difference of the maximum negative pressure on the tunnel wall is caused by the different speed and pressure wave intensity of the train arriving at the same measuring point in different speed modes, and the maximum difference is 15.8%. Hence, it can be concluded that a speed mode of deceleration for trains passing a tunnel can effectively alleviate the aerodynamic effect in the tunnel, especially for the pressure on the tunnel wall.

The track geometry is a critical factor that affects the running safety and riding comfort of trains moving on a high-speed railway bridge. This study addresses the mapping relationship between the track deformation and lateral deformations of bridges. Equilibrium equations and natural boundary conditions of the track-bridge system are established based on the energy variational principle, and an analytical solution is derived for the track deformation accounting for lateral bridge deformations. A five-span simply-supported bridge with continuous welded rail has been selected as the case study. The mapping rail deformations are compared to the finite element results, and both results agree well with each other, validating the analytical method proposed in this paper. The influence factors on the mapping rail deformation are further evaluated. Results show that the mapping rail deformation is consistent with the girder displacement at the area that is away from the girder ends when the flexural stiffness ratio between the track and the bridge girder is low. The interlayer stiffness has a significant effect on the mapping rail deformation when the track flexural stiffness is of a high value.

The damage of the self-compacting concrete in CRTS III slab ballastless track on bridge will lead to a partial void of the track slab, which will affect the comfort and safety of the train and the durability of the track slab and bridge structure. In order to study the impact of the interface crack on the dynamic response of CRTS I ballastless track system on bridge, based on the principle of multi-body dynamics theory and ANSYS+SIMPACK co-simulation, the spatial model of vehicle-track-bridge integration considering the longitudinal stiffness of supports, the track structure and interlayer contact characteristics were established. The dynamic characteristics of the system under different conditions of the width, length and position of the interface crack were analysed, and the limited values of the length and width of the cracks at the track slab edge were proposed. The results show that when the self-compacting concrete does not completely void along the transverse direction of the track slab, the crack has little effect on the dynamic characteristics of the vehicle -track-bridge system. However, when the self-compacting concrete is completely hollowed out along the transverse direction of the track slab, the dynamic amplitudes of the system increase. When the crack length is 1.6 m, the wheel load reduction rate reaches 0.769, which exceeds the limit value and threatens the safety of train operation. The vertical acceleration of the track slab increases by 250.1%, which affects the service life of the track system under the train speed of 200 km/h

In this paper, the effects of a right-angle windbreak transition (RWT) from the flat ground to cutting on train aerodynamic and dynamic responses were investigated, then a mitigation measure, an oblique structure transition (OST) was proposed to reduce the impact of RWT on the train aerodynamic and dynamic performance. The results showed that in the RWT region, the airflow was divided into two parts. One part of the airflow induced a strong backflow in the flat ground position, and the other part of the airflow induced a strong backflow in the cutting position. Therefore, there were two lateral impacts on the train. For the head car with the OST, the drop ratios of the peak-to-peak values compared with RWT were 47%, 40%, and 52% for the side force coefficient C_Fy, lift force coefficient C_Fz and overturning moment coefficient C_Mx, respectively. For the peak-to-peak value of the dynamic parameters, the drop ratios of OST compared with RWT were all larger than 50%. The maximum dynamic overturning coefficients for RWT and OST were 0.75 and 0.3, respectively.

Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains, but their wind-proofing effects are greatly affected by substructures. To investigate the effects of wind barriers on the aerodynamic characteristic of road-rail same-story truss bridge-train systems, wind tunnel experiments were carried out using a 1: 50 scale model. Taking a wind barrier with a porosity of 30% as an example, the aerodynamic characteristics of the bridge-train system under different wind barrier layouts (single-sided and double-sided), positions (inside and outside) and heights (2.5 m, 3.0 m, 3.5 m and 4.0 m) were tested. The results indicate that the downstream inside wind barrier has almost no effect on the aerodynamic characteristics of the train-bridge system, but the downstream outside wind barrier increases the drag coefficient of the bridge and reduces both the lift coefficient and drag coefficient of the train due to its effect on the train’s wind pressure distribution, especially on the train’s leeward surface. When the wind barriers are arranged on the outside, their effects on the drag coefficient of the bridge and shielding effect on the train are greater than when they are arranged on the inside. As the height of the wind barrier increases, the drag coefficient of the bridge also gradually increases, and the lift coefficient and drag coefficient of the train gradually decrease, but the degree of variation of the aerodynamic coefficient with the height is slightly different due to the different wind barrier layouts. When 3.0 m high double-sided wind barriers are arranged on the outside of the truss bridge, the drag coefficient of the bridge only increases by 12%, while the drag coefficient of the train decreases by 55%.

Wind barriers have attracted significant attention as an effective measure to ensure train safety under crosswinds. However, in past decades, the influence of structural parameters such as the height and ventilation ratio of wind barriers on the difference of the average pressure coefficient between the train windward and leeward surface (ΔCp) has not been fully investigated. To determine the influence of the interaction among the three factors, namely the wind barrier height (H), ventilation ratio (R), and distance to the train (D), twenty five numerical simulation cases with different structural parameters were considered based on an orthogonal design. The shear stress transfer (SST) k-ω turbulent model was employed to calculate the wind pressure coefficients, and the calculation accuracy was validated by using wind tunnel experiments. The results indicated that with an increase in R, ΔCp first decreased and then increased, and ΔCp decreased while D increased. Moreover, with the increase in H, ΔCp first increased and then decreased. Therefore, these three factors must be considered during the installation of wind barriers. Furthermore, according to a range analysis (judging the relative importance of the three factors intuitively), the three factors were ranked in the following order: R>H>D. Based on a variance analysis, R was found to be of high significance to ΔCp, followed by H, which was significant, whereas D had relatively insignificant influence. Finally, the optimal values of R and H were determined to be 20% and 110 mm, respectively. And when R=40%, H=85 mm, the train was relatively unsafe under these such conditions. The findings of this study provide significant guidance for the structural design of wind barriers.

Foundation scour is an important cause for structural failure of sea-crossing bridges. Usually, the sea-crossing bridges operate under the harsh natural environment in which service wind, wave and vehicle loads are stronger and extreme loads such as earthquake, hurricane, and ship collision, are more frequent. As a result of the foundation scour, the dynamic behavior of bridge under different combined action of service and extreme loads may be further escalated. In particular, this work has investigated the scour effect on a sea-crossing bridge under service wind, wave and vehicle loads as well as extreme seismic loads. The dynamic coupled earthquake-wind-wave-vehicle-bridge (EWWVB) system is established by considering the interactions within the system, and the p−y curve method is used to calculate the load—displacement relation of the pile and soil under various levels of foundation scour. After that, a case study has been performed on a cable-stayed bridge with foundation scour. The results indicate that the dynamic characteristics of bridge structure will change after considering bridge scour, and the dynamic responses of bridge and vehicle will be affected to different degrees under service and seismic loads considering bridge scour.

To study the additional aerodynamic effect on a bridge girder under the action of wind-driven rain, the rainfall similarity considering raindrop impact and surface water is first given. Then, the dynamic characteristics and the process of vortex and flutter generation of the segment models under different rain intensities and angles of attack are tested by considering several typical main girder sections as examples. The test results indicate that the start and end wind speeds, interval length and number of vortex vibrations remain unchanged when it is raining, rainfall will reduce the wind-induced vortex response. When test rain intensity is large, the decrease of amplitude is obvious. However, after considering the rain intensity similarity in this study, all of actual maximum rain intensities after conversion approach the domestic extreme rain intensity of approximately 709 mm/h. It can be observed that rainfall has a limited influence on the dynamic characteristics of the structure and vortex vibration response. When the test rain intensity is 120 mm/h, the critical wind speed of the model flutter increases by 20%–30%. However, after considering the rain intensity similarity ratio, the influence of rainfall on the wind-induced flutter instability of the bridge girder may be ignored.

The influence of the interaction between surrounding rock and lining on the long-term behaviour of a tunnel in service is significant. In this paper, we proposed a mechanical model of the circular lined tunnel with the alterable mechanical property under hydrostatic stress and radially inner surface pressure of the lining. The alterable mechanical properties of the surrounding rock and the lining are embodied by the changing of their elasticity modulus with service time and radial direction of the tunnel, respectively. The proposed mechanical model is successfully validated by comparison with the existing theoretical models and the numerical simulation, respectively. The influences of the main parameters of the proposed mechanical model, such as the radial power-law indexes and the time-varying coefficients of the surrounding rock and the lining, as well as the radially inner surface pressure of the lining, on the interface displacement and pressure between surrounding rock and lining are investigated. The research results can provide some valuable references for timely diagnosis and correct evaluation of the long-term behaviours of a tunnel in service.

The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct. Meanwhile, the failure of the levitation magnets which balances the gravity of the maglev train could cause the train collision with track. To study the dynamic response of the train and the viaduct when the levitation magnet control loop failure occurs, a high-speed maglev train-viaduct coupling model, which includes a maglev controller fitted by measured force-gap data and considers the actual structure of train and viaduct, is established. Then the accuracy and effectiveness of the established approach are validated by comparing the computed dynamic responses and frequencies with the measurement results. After that, the dynamic responses of maglev train and viaduct are discussed under normal operation and control loop failures, and the most disadvantageous combination of control loop failures is obtained. The results show that when a single control loop fails, it only has a great influence on the failed electromagnet, and the maglev response of adjacent electromagnets has no obvious change and no collision occurs. But there is a risk of rail collisions when the dual control loop fails.

Under high-level earthquakes, bridge piers and bearings are prone to be damaged and the elastoplastic state of bridge structural components is easily accessible in the train-track-bridge interaction (TTBI) system. Considering the complexity and structural non-linearity of the TTBI system under earthquakes, a single software is not adequate for the coupling analysis. Therefore, in this paper, an interactive method for the TTBI system is proposed by combining the multi-body dynamics software Simpack and the seismic simulation software OpenSees based on the Client-Server architecture, which takes full advantages of the powerful wheel-track contact analysis capabilities of Simpack and the sophisticated nonlinear analysis capabilities of OpenSees. Based on the proposed Simpack and OpenSees co-simulating train-track-bridge (SOTTB) method, a single-span bridge analysis under the earthquake was conducted and the accuracy of co-simulation method was verified by comparing it with results of the finite element model. Finally, the TTBI model is built utilizing the SOTTB method to further discuss the running safety of HST on multi-span simply supported bridges under earthquakes. The results show that the SOTTB method has the advantages of usability, high versatility and accuracy which can be further used to study the running safety of HST under earthquakes with high intensities.

Based on Hamilton’s principle, the differential equations of free vibration of track-bridge systems with mortar gap are derived. Hence, a method for calculating the natural frequencies of track-bridge systems is proposed. The influence of the flexural stiffness of the track-bridge system, the vertical and longitudinal stiffness of the mortar layer, gap position and gap length on the natural frequencies of a track-bridge system is discussed. The results show that the natural frequencies of the track-bridge system are more sensitive to the change of the flexural stiffness of the bridge layer. The change of the longitudinal stiffness of the mortar layer and gap position has no obvious effect on the trackbridge system’s natural frequencies, while the interlayer vertical stiffness has a larger impact. The gap length has a more significant effect on the 4th–5th order natural frequencies of the track-bridge system. The range of the natural frequencies that are affected by the gap widens as the gap length increases.

The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design. To address this topic, this study firstly analyzes the posture characteristics of the car-body based on the previous full-scale test results. And then the aerodynamic performance under different vibration cases (different car-body roll angles) is studied with an improved delayed detached eddy simulation (IDDES). The results revealed that car-body rolling had a significant impact on the aerodynamic behavior of bogies, which significantly increased the lateral force and yaw moment of a bogie and further may have aggravated the operational instability of the train. The unbalanced distribution of the longitudinal pressure on both sides of the bogie caused by the car-body rolling motion was the primary cause for the bogie yaw moment increase. The tail vortex of the train was also affected by the car-body rolling, resulting in vertical jitter.