Search Results (55)

An innovative method is proposed to analyze the coupled vibration between random traffic and large-span bridges under the combined action of wind loads. The dynamic behavior of bridges subjected to these multifactorial influences is investigated through a comprehensive bridge dynamics model. Specifically, a refined full-bridge finite element model is developed to simulate the traffic–bridge coupled vibration, with wind forces applied as external dynamic loads. The effects of wind speed and vehicle speed on the coupled system are systematically evaluated using the finite element software ABAQUS 2023. To ensure computational accuracy and efficiency, the large-span nonlinear dynamic solution method is employed, integrating the Newmark-β time integration method with the Newton–Raphson iterative technique. The proposed method is validated through experimental measurements, demonstrating its effectiveness in capturing the synergistic impacts of wind and traffic on bridge dynamics. By incorporating the stochastic nature of traffic flow and combined wind forces, this approach provides a detailed analysis of bridge responses under complex loading conditions. The study establishes a theoretical foundation and practical reference for the safety assessment of large-span bridges. Full article

Under cyclic moving load action, tensile-dominant structures are prone to crack initiation due to cumulative damage effects. The presence of cracks leads to structural stiffness degradation and nonlinear redistribution of dynamic characteristics, thereby compromising str18uctural integrity and service performance. The current research on the dynamic behavior of cracked structures predominantly focuses on transient analysis through high-fidelity finite element models. However, the existing methodologies encounter two critical limitations: computational inefficiency and a trade-off between model fidelity and practicality. Thus, this study presents an innovative analytical framework to investigate the dynamic response of cracked simply supported beams subjected to moving loads. The proposed methodology conceptualizes the cracked beam as a system composed of multiple interconnected sub-beams, each governed by the Euler–Bernoulli beam theory. At crack locations, massless rotational springs are employed to accurately capture the local flexibility induced by these defects. The transfer matrix method is utilized to derive explicit eigenfunctions for the cracked beam system, thereby facilitating the formulation of coupled vehicle–bridge vibration equations through modal superposition. Subsequently, dynamic response analysis is conducted using the Runge–Kutta numerical integration scheme. Extensive numerical simulations reveal the influence of critical parameters—particularly crack depth and location—on the coupled dynamic behavior of the structure subjected to moving loads. The results indicate that at a constant speed, neither crack depth nor position alters the shape of the beam’s vibration curve. The maximum deflection of beams with a 30% crack in the middle span increases by 14.96% compared to those without cracks. Furthermore, crack migration toward the mid-span results in increased mid-span displacement without changing vibration curve topology. For a constant crack depth ratio (γ_i = 0.3), the progressive migration of the crack position from 0.05 L to 0.5 L leads to a 26.4% increase in the mid-span displacement (from 5.3 mm to 6.7 mm). These findings highlight the efficacy of the proposed method in capturing the complex interactions between moving loads and cracked concrete structures, offering valuable insights for structural health monitoring and assessment. Full article

With the continuous development of maglev transportation technology, medium–low-speed maglev trains have been widely implemented in many countries. However, due to the limitations of existing specifications, the stiffness limit values of the large-span main girders used in medium–low-speed maglev trains have not been unified. To address this issue, this study takes a specific bridge on a dedicated maglev line as an example and uses self-developed software to model the vehicle–bridge dynamic system. The natural vibration characteristics and vehicle–bridge coupling vibration response of the bridge are calculated and analyzed. Based on this, the influence of pier top stiffness on the dynamic characteristics of a typical medium–low-speed maglev train–bridge system under different working conditions is investigated, with a focus on the lateral line stiffness at the pier top. The results show that vehicle speed has no significant effect on the lateral displacement of the main girder, the lateral displacement of the pier top, the lateral acceleration of the pier top, and the transverse and longitudinal angles of the beam end, and no obvious regularity is observed. However, in the double-track operating condition, the vertical deflection of the main girder is significantly higher than that in the single-track operating condition. As the lateral linear stiffness at the pier top increases, the fundamental frequency of the bridge’s lateral bending vibration gradually increases, while the fundamental frequency of longitudinal floating gradually decreases. The lateral displacements, including those of the main girder, pier top, and beam ends, all decrease, whereas the lateral and vertical vibration accelerations of the main girder and the train are less affected by the lateral stiffness at the pier top. Full article

The monorail tourism transit system (MTTS) is a large-scale amusement facility. Currently, there is limited theoretical research on the vehicle–bridge coupling vibration and dynamic amplification factor (DAFs) of this system. The values specified in relevant standards are not entirely reasonable; for instance, the calculated value of the DAFs in the “Large-scale amusement device safety code (GB 8408-2018)” only takes speed into account and is set at 0.44 when the speed is between 20 and 40 km/h. This is overly simplistic and obviously too large. This paper aims to establish a reasonable expression of the DAFs for the MTTS and improve the design code of the industry. Firstly, using on-site trials of the project and the dynamics numerical simulation method, the dynamic response characteristics of the MTTS and the influencing factors of the DAFs were systematically analyzed. The rationality and accuracy of the model were verified. Secondly, combined with the joint simulation model, the dynamic influence mechanism of multifactor coupling on the DAFs was revealed. On this basis, the key regression parameters were selected by using the Pearson correlation coefficient method and the random forest algorithm, and the DAFs prediction model was constructed based on the least absolute shrinkage and selection operator (LASSO) regression theory. Finally, through cross-comparison of simulation data and specification verification, a recommended calculation expression of the DAFs for the MTTS was proposed. The research results show that the established prediction model can predict 94.50% of the variation information of the DAFs of the MTTS and pass the 95% confidence level and 0.05 significance test. The accuracy is high and relatively reasonable and can provide a reference for the design of the MTTS. Full article

To investigate the dynamic characteristics of a PC beam–steel box arch composite bridge when the number of loading lanes for autonomous vehicles changes, the vehicle–bridge coupling motion equation was derived and solved iteratively via the Newmark-β method. Joint simulation software based on ANSYS 17.0 and Easy Language was developed to analyze vehicle–bridge coupling and driving comfort. The results showed that the dynamic response is the largest under single-lane conditions, with suspected vehicle–bridge resonance. For multilane conditions, eccentricity is the main factor when the vehicle weight is low, whereas the vehicle weight dominates when it is large. The dynamic response is positively correlated with eccentricity and vehicle weight. With respect to the dynamic amplification factor (DAF), single-lane conditions yield high DAF values for the main beam, main arch, and boom, whereas the main pier has a greater DAF under multilane conditions. Driving comfort is best under single-lane conditions, followed by dual-lane conditions, and worst under three-lane conditions. Speed is the primary influencer of comfort under single-lane conditions, with comfort reduced at higher speeds. Under multilane conditions, both speed and eccentricity affect comfort, with speed being the dominant factor. The calculated impact coefficient significantly exceeds the standard values, suggesting that separate impact coefficients should be set for each load-bearing component. These findings, combined with driving comfort analysis, provide valuable references for the setting of speed limits and the design and maintenance of such bridges under autonomous vehicle loads. Full article

The dynamic performance of a ballastless track on bridges affects the vibration performance of the vehicle–bridge coupling system, which, in turn, will affect safety, the smoothness of operating trains, and passenger comfort. However, in the existing literature, few studies focus on the coupled vibration response analysis of large-span continuous beam bridges for high-speed railways, especially high-pier bridges. Dynamic response tests with multiple measurement points installed on the rail, concrete slab, and bridge deck are conducted. This study investigates the dynamic characteristics of bridges with high piers under train loads. A dynamic system is built by the co-simulation platform of SIMPACK v9 and ANSYS v2022, consisting of several models, a coupling mechanism, etc. The vibration response of a train passing through the bridge at 300 km/h is analyzed, and the influence of operating speed on the motivation performance of the coupled system is further studied. The results indicate that the simulation results are validated against experimental data, showing good agreement; the train–track–continuous beam bridge coupling system meets the specification limits and has some margins for further optimization with an operating speed of 300 km/h. The refined model of train–rail–bridge coupling vibration established in this paper provides theoretical guidance for the design and application of high-speed railways. Full article

This study investigates the vehicle–bridge coupling vibration performance of corrugated steel web box girder bridges under three-dimensional pavement roughness conditions. To effectively account for these roughness characteristics, a three-dimensional contact constraint method is proposed. The accuracy of the proposed method is first verified, followed by an analysis of a 30 m span corrugated steel web box girder bridge to evaluate the influence of vehicle speed, pavement grade, roughness dimensions, and box girder configurations on the impact factor. The results show that the impact factor does not consistently increase with vehicle speed. As pavement conditions worsen, the impact factor shows an upward trend, with each grade of road surface deterioration resulting in an average 19.1% increase in the impact factor. In most scenarios, three-dimensional pavement roughness results in smaller impact factors compared to two-dimensional pavement roughness, with average reductions of 2.4%, 7.3%, and 13.5% for grade A, B, and C roads, respectively. Replacing the corrugated steel web with a flat steel web leads to an average reduction of 4.2% in the mid-span dynamic deflection of the bridge, despite the impact factors of both configurations being relatively similar. Substituting the concrete bottom slab with an equivalent steel bottom slab increases the mid-span dynamic deflection by an average of 28.4% and nearly doubles the impact factor. The impact factors determined by most national standards generally fall within the range for grade A pavement, suggesting that the calculation methods in these standards are mainly suited for newly constructed bridges or those in good maintenance. Full article

This study investigated the impact coefficient of a large-span steel truss arch railroad bridge under moving train loads, with the Nanning Three Banks Yongjiang Special Bridge serving as the case study. Field tests were conducted to measure the bridge’s self-vibration characteristics, dynamic deflection, and strain. A coupled vehicle–bridge vibration model was developed using the finite element software ABAQUS 2022 for the bridge and multi-body dynamics software SIMPACK 2022 for the CRH2 train. The two models were integrated to simulate the dynamic interaction between the train and bridge under different speeds and single-/double-track operations. The results demonstrate that the joint simulation of SIMPACK and ABAQUS was an effective method for the vehicle–bridge coupled vibration analysis. The key findings include the following: the deflection and stress impact coefficients increased with the train speed, where the main span exhibited larger deflection coefficients than the side span. The stress impact coefficients varied significantly across different bridge components, where the lower chord of the side span and the ties of the main span showed the highest values. While there was no substantial difference in the deflection impact coefficients between the single- and double-track operations, the stress impact coefficients showed deviations, particularly in the side span’s lower chord and ties, highlighting their sensitivity to vehicle-induced deflection. This study concluded that the bridge’s deflection impact coefficient met design specifications, but the stress impact coefficient exceeded the specified values, suggesting that stress amplification should be carefully considered in the design of similar bridges to ensure operational safety. Full article

To address the vehicle-bridge coupling vibration issue of the Qingyuan Maglev Tourist Line, it is necessary to establish a maglev vehicle–bridge coupling dynamics simulation model that reflects the actual line conditions. Based on the vehicle and bridge structural parameters of the Qingyuan Maglev Tourist Line, this paper utilizes multi-body dynamics simulation software to create a medium–low-speed maglev vehicle dynamics model, and employs finite element software to construct a bridge model. Using the modal reduction method, the bridge finite element model is imported into the vehicle dynamics model through a rigid–flex coupling interface, establishing a medium–low-speed maglev vehicle suspension system–bridge coupling dynamics model. The accuracy of the established coupling simulation model was verified by comparing the simulation data from the coupling model with the dynamic response measured data from the Qingyuan Maglev Tourist Line. Finally, the impact of different control parameters on the vehicle–bridge coupling system was calculated, and the results indicate that selecting appropriate suspension control parameters can reduce the coupling vibration response between the maglev vehicle and the bridge. The main work of this paper is closely related to engineering, modeling based on the actual maglev line’s vehicle and bridge parameters, and validating the model through the dynamic test results of the line, laying the foundation for the suppression of maglev vehicle–bridge coupling vibration and system optimization. Full article

To investigate the impact of vehicle load on highway pile–slab bridges, the contact constraint method is employed to treat the vehicle and the bridge as two independent subsystems. Through the formulation of point-to-surface contact and constraint equations, a vehicle–bridge coupling vibration analysis is performed, incorporating the effects of bridge deck roughness. The finite element method is utilized to construct the pile–slab bridge model, while the five-axis heavy vehicle model is developed based on the multi-rigid-body dynamics method. The analysis and computational results of the model reveal the effects of pier height, vehicle number, and the friction coefficient on the dynamic response of the pile–slab bridge. The results indicate that pier height significantly influences the dynamic response, and the appropriate pier height should be carefully determined during the design phase. The vertical displacement impact coefficient surpasses the design value derived from the specification, highlighting the need to consider the vehicle’s impact on the bridge. Furthermore, vehicle number and the friction coefficient significantly affect the longitudinal dynamic response and transverse acceleration response of the pile–slab bridge. Full article

To achieve a rapid assessment of reinforced bridges without interrupting traffic, the method and influence parameters for evaluating prestressed CFRP (Carbon Fiber Reinforced Polymer) plate-strengthened bridges were investigated based on distributed sensing while considering the bridge–vehicle coupling. Firstly, based on the principle of distributed monitoring, the strain influence line equation for prestressed CFRP plate-strengthened bridges under moving vehicle loads was derived. An evaluation index and method for assessing strengthening effectiveness based on distributed strain monitoring was proposed. Numerical simulation experiments were conducted for verification, in which a simulation method for solving the bridge–vehicle coupling vibration response based on the displacement contact method was studied. Relevant example verifications were carried out to prove the correctness of this method. On this basis, a dynamic performance analysis of the bridge before and after strengthening under bridge–vehicle coupling was performed. Finally, a study on influencing parameters was conducted to investigate the impact of different prestress levels of CFRP plates, different vehicle speeds, and different vehicle axle loads on the evaluation method. The results demonstrate that the bridge–vehicle coupling calculation model based on the displacement contact method can effectively simulate the dynamic response of the bridge after reinforcement. The evaluation method based on distributed sensing monitoring is unaffected by the speed and axle load of the vehicle, enabling the assessment of the condition and stress state of the strengthened bridge. Full article

Track irregularity is one of the principal excitations that induces coupled vibrations in vehicle–bridge systems. Understanding the sensitive wavelength of track irregularities is critical for the evaluation and management of track conditions. Notably, existing studies generally focus on railway systems, but the characteristics of sensitive wavelengths in monorail systems are insufficiently understood. This study aims to investigate the influence of longitudinal level irregularity (LLI) on the dynamic response of the monorail tour transit system (MTTS), as well as the sensitive wavelength of LLI. First, a joint model was developed by integrating multi-body dynamics with the finite element method. The LLI utilized in the numerical mode was simulated by trigonometric functions with various frequencies (i.e., wavelengths) and amplitudes. The dynamic responses of monorail vehicles, including the wheel load reduction rate and vertical acceleration, were obtained and then used to evaluate track conditions. Results indicate that the dynamic responses of MTTS are mainly affected by the LLI with a wavelength of less than 5 m. In addition, it was found that, in the studied ranges, the sensitivity wavelength grows as the vehicle speed increases. Finally, the recommended value of LLI control under various track conditions was evaluated. Full article

In order to study the influence of the difference between the center of mass and shear center position of the main girder cross-section on the coupled vibration response of a vehicle–bridge, and in accordance with the theory of finite element analysis, we derive the stiffness matrix of the spatial girder unit with the main girder cross-section mass–shear center heterocentricity, use finite element software to establish a bridge model, select a three-axle heavy vehicle, and solve the coupled vibration equation of the vehicle–bridge by the separation method. A large-span self-anchored suspension bridge is taken as the research object, and a self-programming program is used to calculate and analyze the influence of the main girder cross-section mass–shear center heterocentricity, driving lanes, and speed on the coupled vibration response of the vehicle–bridge. The results show the following: the main girder cross-section mass–shear center heterocentricity has a significant effect on the transverse dynamic response of the bridge, and the peak values of transverse displacement and acceleration in the main span are increased by about 87% and 136%; the outward shift of lanes has a greater effect on the transverse dynamic response of the bridge; and the vibration response of the bridge while considering mass–shear center heterocentricity is more affected under different vehicle speeds. Full article

Elevated stations are integral components of urban rail transit systems, significantly impacting passengers’ travel experience and the operational efficiency of the transportation system. However, current elevated station designs often do not sufficiently consider the structural dynamic response under various operating conditions. This oversight can limit the operational efficiency of the stations and pose potential safety hazards. Addressing this issue, this study establishes a vehicle-bridge-station spatial coupling vibration simulation model utilizing the self-developed software GSAP V1.0, focusing on integrated station-bridge and combined station-bridge elevated station designs. The simulation results are meticulously compared with field data to ensure the fidelity of the model. Analyzing the dynamic response of the station in relation to train parameters reveals significant insights. Notably, under similar travel conditions, integrated stations exhibit lower vertical acceleration in the rail-bearing layer compared to combined stations, while the vertical acceleration patterns at the platform and hall layers demonstrate contrasting behaviors. At lower speeds, the vertical acceleration at the station concourse level is comparable for both station types, yet integrated stations exhibit notably higher platform-level acceleration. Conversely, under high-speed conditions, integrated stations show increased vertical acceleration at the platform and hall levels compared to combined stations, particularly under unloaded double-line working conditions, indicating a superior dynamic performance of combined stations in complex operational scenarios. However, challenges such as increased station height due to bridge box girder maintenance, track layer waterproofing, and track girder support maintenance exist for combined stations, warranting comprehensive evaluation for station selection. Further analysis of integrated station-bridge structures reveals that adjustments in the floor slab thickness at the rail-bearing and platform levels significantly reduce dynamic responses, whereas increasing the rail beam height notably diminishes displacement responses. Conversely, alterations in the waiting hall floor slab thickness and frame column cross-sections exhibit a minimal impact on the station dynamics. Overall, optimizing structural dimensions can effectively mitigate dynamic responses, offering valuable insights for station design and operation. Full article

A steel–concrete composite beam bridge fully exploits the mechanical advantages of the concrete structure and steel structure, and has the advantages of a fast construction speed and large stiffness. It is of certain research value to explore the application of this bridge type in the field of railway bridges. However, with the rapid development of domestic high-speed railway construction, the problem of vibration and noise radiation of high-speed railway bridges caused by train loads is becoming more and more serious. A steel–concrete composite beam bridge combines the tensile characteristics of steel and the compressive characteristics of concrete perfectly. At the same time, it also has the characteristics of a steel bridge and concrete bridge in terms of vibration and noise radiation. This feature makes the study of the vibration and noise of the bridge type more complicated. Therefore, in this paper, the characteristics of vibration and noise radiation of a high-speed railway steel–concrete composite box girder bridge are studied in detail from two aspects: the theoretical basis and a numerical simulation. The main results obtained are as follows: Relying on the idea of vehicle–rail–bridge coupling dynamics, a structural dynamics analysis model of a steel–concrete combined girder bridge for a high-speed railroad was established, and numerical program simulation of the vibration of the vehicle–rail–bridge coupling system was carried out based on the parametric design language of ANSYS 18.0 and the language of MATLAB R2021a, and the structural vibration results were analyzed in both the time domain and frequency domain. By using different time-step loading for the vehicle–rail–bridge coupling vibration analysis, the computational efficiency can be effectively improved under the condition of guaranteeing the accuracy of the result analysis within 100 Hz. Based on the power flow equilibrium equation, a statistical energy method of calculating the high-frequency noise radiation is theoretically derived. Based on the theoretical basis of the statistical energy method, the high-frequency noise in the structure is numerically simulated in the VAONE 2021 software, and the average contribution of the concrete roof plate to the three acoustic field points constructed in this paper is as high as 50%, which is of great significance in the study of noise reduction in steel–concrete composite girders. Full article