Static Wind Stability Analysis of Large-Span Steel Pipe Concrete Arch Bridges

Literature Overview

This paper by Yu Honggang, Ge Yaojun, Zhang Wei, and Yang Yongxin from the State Key Laboratory of Disaster Prevention in Civil Engineering at Tongji University, published in Bridge Construction in 2007, presents a comprehensive static wind stability analysis of the Sanmenkou Cross-Sea Bridge's North Gate Bridge. The bridge features a 270-meter main span with a steel pipe concrete (SRC) half-through arch configuration. The research, supported by the National Natural Science Foundation (Project No. 50278069), combines wind tunnel testing with numerical analysis to evaluate the bridge's static wind stability during both construction and operational phases.

Bridge Configuration and Structural Characteristics

The North Gate Bridge represents a significant engineering challenge due to its combination of:

• Large span (270 m) requiring substantial aerodynamic consideration
• SRC arch ribs providing high stiffness-to-weight ratio
• Half-through (middle-supported) configuration with unique wind exposure characteristics
• Marine environment with sustained high wind loads

Structural Parameters

Static Wind Stability Methodology

Static wind stability analysis evaluates whether a bridge structure can maintain equilibrium under steady-state wind loading without experiencing progressive deformation or collapse. This is distinct from flutter (dynamic aeroelastic instability) and galloping analysis.

Force Coefficient Determination

The paper emphasizes the determination of static force coefficients through wind tunnel testing, with a critical finding being the need for Reynolds number correction of the arch rib force coefficients. The Reynolds number (Re) for bridge aerodynamics is typically in the range of 10⁵–10⁶ for full-scale structures, while wind tunnel testing at model scale may operate at different Re values, necessitating correction.

The three-dimensional force coefficients on the arch rib include:

• Drag coefficient (C_D): Resistance force parallel to wind direction
• Lift coefficient (C_L): Force perpendicular to wind direction
• Moment coefficient (C_M): Rotational force about the rib centroid

Reynolds Number Correction

The Reynolds number correction is a critical technical point in this paper. At lower Re (typical in wind tunnel testing), the flow separation behavior differs from full-scale conditions, leading to potentially inaccurate force coefficients. The correction methodology involves:

1. Measuring force coefficients at multiple model scales or tunnel conditions to establish Re dependence.
2. Extrapolating to full-scale Re using established aerodynamic scaling laws.
3. Applying the corrected coefficients in structural stability calculations.

Finite Element Analysis and Stability Verification

The numerical analysis employed finite element methods to model the bridge structure and apply the corrected static wind force coefficients. The analysis was conducted for:

• Construction stages (when the structure is partially complete and may have reduced stiffness)
• Operational stage (complete structure under service loads)

Stability Assessment Results

Technical Analysis of Wind Stability in SRC Arch Bridges

The static wind stability of SRC arch bridges involves several unique considerations compared to conventional steel or concrete arch bridges:

Aerodynamic Characteristics of SRC Arch Ribs

The circular cross-section of SRC arch ribs provides inherent aerodynamic advantages:

• Symmetric cross-section eliminates lift asymmetry
• Rounded shape promotes smooth flow attachment
• Reduced vortex shedding amplitude compared to flat or angular sections

However, challenges remain:

• Wind blockage effects on the deck and hangers
• Wind-induced lateral forces on the arch rib
• Combined wind and gravity load interaction
• Temperature-wind coupling effects on arch rib forces

Structural Response Mechanisms

Under static wind loading, the SRC arch bridge responds through:

1. Lateral bending of arch ribs: Wind pressure creates out-of-plane bending moments.
2. Torsional response: Asymmetric wind loading on the deck and arch system.
3. Axial force redistribution: Wind-induced bending modifies the axial force distribution in arch ribs.
4. Foundation loading: Combined vertical and lateral loads on pier and abutment foundations.

The SRC composite section provides advantages for wind stability through:

• High bending stiffness from the steel pipe providing tensile capacity
• Compressive capacity from the concrete core
• Composite action providing high moment capacity with relatively compact cross-sections
• Damping from the concrete-steel interface

Engineering Practice Implications

For engineers designing large-span SRC arch bridges in high-wind environments, this paper provides several actionable guidelines:

1. Wind tunnel testing is essential: Empirical force coefficients from codes are insufficient for large-span bridges. Full-scale aerodynamic characterization through wind tunnel testing is necessary.
2. Reynolds number correction must be applied: Without proper Re correction, wind tunnel results may be inaccurate for full-scale prediction.
3. Construction stage stability must be verified: The partially constructed structure may have reduced lateral stiffness and is more vulnerable to wind-induced instability.
4. Three-dimensional force coefficients are required: Two-dimensional section testing may not capture the full aerodynamic behavior of the complete bridge structure.

Study Insights and Reflections

This research demonstrates the importance of rigorous aerodynamic analysis for large-span bridge design, particularly for SRC arch bridges where the structural form and aerodynamic characteristics are intimately coupled. The 270-meter span places this bridge in a category where wind effects can significantly influence structural design, and the marine location adds environmental severity.

The Reynolds number correction methodology highlighted in this paper is particularly relevant for engineers who may otherwise assume that wind tunnel results directly scale to full-size structures. The finding that Re correction is necessary for accurate force coefficient determination represents a critical technical insight that should be incorporated into all large-span bridge aerodynamic analysis.

The confirmation that both construction and operational stages satisfy static wind stability requirements provides validation for the SRC arch bridge design approach in high-wind environments. This supports the continued development and application of SRC arch bridges for long-span crossings, provided that appropriate aerodynamic analysis is conducted during the design phase.