Vehicle-Bridge Coupled Vibration Analysis of Large-Span Steel Tube Concrete Arch Bridges for High-Speed Railway

Engineering Background

This paper by Han Xing, Cai Zilong, Li Xin, and Zhu Bing from Southwest Jiaotong University presents a vehicle-bridge coupled vibration simulation analysis of a large-span steel tube concrete (CFST) arch bridge for high-speed railway, published in Railway Standard Design in 2016. The study uses the Yachi River Bridge as the engineering background, which is a notable long-span CFST arch bridge carrying high-speed rail traffic.

The dynamic interaction between high-speed trains and bridge structures is a critical design consideration for railway bridges. Unlike road bridges, railway bridges must accommodate vehicles traveling at speeds exceeding 250 km/h, which introduces significant dynamic effects including vertical and lateral vibrations, wheel-rail contact forces, and track irregularity-induced excitations. For long-span arch bridges with CFST arch ribs, the structural stiffness and mass distribution create unique dynamic characteristics that must be carefully evaluated.

Modeling Approach and Methodology

The study employed a coupled simulation approach combining two specialized software platforms:

• ANSYS: Used to establish the finite element dynamic analysis model of the bridge structure, including the CFST arch ribs, deck system, hangers, and supports. The natural vibration characteristics (mode shapes and frequencies) of the bridge were calculated to characterize its dynamic behavior.
• SIMPACK: Used to create a high-fidelity multi-body dynamics model of the CRH3 train set, including the bogie dynamics, wheel-rail contact mechanics, and vehicle suspension systems.

The coupled vehicle-bridge vibration system was established by linking the SIMPACK vehicle model with the ANSYS bridge model through the wheel-rail interface. Track irregularities were input as excitations, and the wheel-rail contact relationships were modeled to capture the dynamic force transmission between vehicle and bridge.

From a structural engineering perspective, the CFST arch ribs are the primary load-bearing elements of the bridge. The steel tubes provide both tensile and compressive strength, while the concrete core contributes to compressive capacity and fire resistance. The welding quality of the steel tubes, particularly at the gusset plate connections and splice joints, is critical for the structural integrity and dynamic performance of the arch ribs.

Dynamic Characteristics and Coupled Vibration Results

The natural vibration analysis of the bridge revealed its fundamental frequencies and mode shapes, which are essential for understanding the dynamic response characteristics. The bridge was found to possess sufficient stiffness to accommodate the dynamic loading from high-speed train passage.

The vehicle-bridge coupled vibration analysis results demonstrated:

The analysis confirmed that the bridge structure has adequate stiffness and dynamic performance for high-speed railway operations. The ride comfort assessment achieved an "excellent" rating, indicating that passengers would experience minimal discomfort during train passage.

Safety and Comfort Assessment

The vehicle-bridge coupled vibration analysis provides comprehensive evaluation of both structural safety and operational comfort. The key safety indicators include:

• Derailment safety: The lateral and vertical accelerations of the train remain well within the safety thresholds defined by railway standards.
• Wheel-rail contact forces: The dynamic wheel-rail forces remain within acceptable limits, ensuring stable wheel-rail contact and preventing wheel lift or excessive lateral forces.
• Bridge structural response: The dynamic stresses in the bridge members remain within the allowable limits, ensuring structural safety under repeated train loading.

The ride comfort assessment, based on the acceleration spectra of the vehicle, confirmed excellent comfort levels. This is particularly important for passenger satisfaction and operational efficiency on high-speed rail lines.

The coupled simulation approach demonstrated feasibility and convenience for evaluating the dynamic performance of large-span railway bridges. The integration of specialized vehicle dynamics and structural dynamics software provides a comprehensive analysis framework that captures the complex interactions between vehicle and bridge systems.

Reflections and Engineering Value

This study demonstrates the practical application of coupled vehicle-bridge simulation for the design and assessment of large-span CFST arch bridges for high-speed railway. Several key insights emerge:

1. CFST arch ribs are well-suited for long-span railway bridges: The combination of high stiffness, lightweight characteristics, and good seismic performance makes CFST arch ribs an excellent choice for large-span railway bridge applications.
2. Dynamic analysis is essential: Static analysis alone is insufficient for evaluating the performance of bridges under high-speed train loading. The dynamic interaction effects can significantly influence both structural response and vehicle running quality.
3. Coupled simulation is practical: The combined ANSYS-SIMPACK approach provides a feasible methodology for evaluating vehicle-bridge dynamic interaction, offering valuable insights that cannot be obtained from separate analyses.
4. Welding quality is critical: For CFST arch bridges, the welding quality of steel tube splices and connection details directly affects the structural stiffness and dynamic performance. Rigorous welding quality control and non-destructive testing are essential.

The results of this study provide valuable reference for the design of similar large-span railway bridges and validate the coupled simulation methodology for dynamic assessment. The engineering practice emphasizes the importance of considering vehicle-bridge interaction effects in the design of high-speed railway bridges.