Zhuojin Pipe Fitting Co., LtdVehicle Parameters and Vehicle-Bridge Coupled Vibration in Large-Span CFST Arch Bridges
Literature Overview
This study investigates how vehicle parameters influence the dynamic response of large-span concrete-filled steel tube (CFST) arch bridges under vehicle-bridge coupled vibration conditions. As CFST arch bridges have become increasingly prevalent in transportation infrastructure due to their elegant structural form, long span capability, and efficient material utilization, understanding the interaction between moving vehicles and the bridge structure is essential for serviceability assessment, fatigue life prediction, and operational safety.
The research employs a coupled vehicle-bridge dynamic analysis framework that simultaneously solves the equations of motion for both the vehicle system and the bridge structure, accounting for the bidirectional interaction through the contact interface at each wheel-bridge node.
Core Technical Framework
Vehicle Model Parameters
The vehicle is modeled as a multi-body dynamic system with the following key parameters:
| Vehicle Parameter | Symbol | Typical Range | Influence on Bridge Response |
|---|---|---|---|
| Vehicle mass | m_v | 10–40 tonnes | Directly proportional to dynamic load magnitude |
| Vehicle speed | v | 30–120 km/h | Determines excitation frequency content |
| Tire stiffness | k_t | 500–2000 kN/m | Governs high-frequency dynamic amplification |
| Tire damping | c_t | 10–50 kN·s/m | Controls vibration isolation effectiveness |
| Suspension stiffness | k_s | 20–80 kN/m | Filters road roughness excitation |
| Suspension damping | c_s | 5–20 kN·s/m | Affects passenger comfort and dynamic load transfer |
| Vehicle body inertia | I_x, I_y, I_z | 500–5000 kg·m² | Influences pitch, roll, and yaw modes |
Bridge Structural Model
The CFST arch bridge is modeled using finite element analysis with the arch ribs represented as space beam elements that account for the composite action between the steel tube and concrete infill. The deck system, hangers, and foundations are also included in the coupled model. The concrete-filled steel tube sections are characterized by their effective composite stiffness, which is notably higher than unfilled steel tubes due to the confinement effect and increased moment of inertia.
Key Findings and Analysis
Speed-Vibration Relationship
The study reveals that bridge dynamic responses exhibit distinct behavior across different speed ranges:
- Low speed regime (30–60 km/h): Quasi-static loading dominates; dynamic amplification factors (DAF) range from 1.05 to 1.15, with minimal sensitivity to vehicle suspension parameters.
- Medium speed regime (60–90 km/h): Resonance effects become significant as the vehicle excitation frequency approaches the fundamental vertical frequency of the bridge; DAF values can reach 1.20–1.40.
- High speed regime (90–120 km/h): The vehicle effectively acts as a distributed moving load; DAF stabilizes at 1.15–1.30, with increased sensitivity to road surface irregularities rather than vehicle mass.
Mass Effect
Vehicle mass has a nonlinear effect on bridge response. For light vehicles (10–15 tonnes), the dynamic load is dominated by the vehicle's dynamic suspension response. For heavy vehicles (30–40 tonnes), the quasi-static component dominates, and the DAF decreases slightly as the vehicle mass increases relative to the bridge modal mass. The critical vehicle mass that maximizes dynamic response typically corresponds to a ratio of vehicle modal mass to bridge modal mass of approximately 0.05–0.10.
Coupled Vibration Characteristics
The coupled vibration analysis reveals that the vehicle-bridge system exhibits coupled natural frequencies that differ from the individual vehicle and bridge frequencies. The coupling is strongest when the vehicle natural frequency (typically 1.5–2.5 Hz for the vertical suspension mode) approaches the bridge fundamental frequency (typically 0.5–2.0 Hz for large-span arch bridges). This frequency coincidence can lead to resonance amplification, particularly during the vehicle's passage over the bridge midspan.
Engineering Practice Implications
For the design and assessment of CFST arch bridges, this research provides several actionable insights:
- Speed restrictions should be calibrated against the bridge's fundamental frequency and the expected vehicle mass spectrum, not applied uniformly based on span length alone
- Fatigue assessment of CFST arch ribs should account for dynamic amplification factors that vary with vehicle parameters, particularly for the high-cycle fatigue details at the steel-concrete interface
- Seismic design considerations should note that the dynamic stiffness of CFST arch ribs, as influenced by vehicle loading, differs from the static stiffness assumptions used in seismic response analysis
Monitoring Recommendations
| Monitoring Parameter | Instrumentation | Sampling Rate | Purpose |
|---|---|---|---|
| Arch rib acceleration | MEMS accelerometer | 200 Hz | Dynamic response capture |
| Arch rib displacement | Fiber Bragg grating sensor | 10 Hz | Long-term deformation |
| Vehicle weight | Weigh-in-motion system | Continuous | Load inventory |
| Bridge temperature | RTD sensor array | 1 Hz | Thermal effect compensation |
Study Insights and Conclusions
The vehicle-bridge coupled vibration analysis presented in this study underscores the importance of considering the dynamic interaction between traffic loads and CFST arch bridge structures. The composite nature of the steel-concrete arch ribs provides inherent stiffness and damping advantages compared to unfilled steel arches, but the dynamic response is still significantly influenced by vehicle parameters, particularly speed and mass. Engineers involved in the design, assessment, or maintenance of such bridges should incorporate coupled vibration analysis results into their serviceability and fatigue evaluations, recognizing that the dynamic environment of a CFST arch bridge is fundamentally different from that of a simple beam bridge or a conventional steel arch.