Introduction
Three-face billboards, due to their unique geometry and large surface area, are significantly affected by wind loads, which can govern their structural design. Traditional approaches to estimate wind loads using standards like EN 1991-1-4 or ASCE 7 often fall short in capturing localized flow effects and shielding interactions between faces. This paper presents a detailed overview of the role of Computational Fluid Dynamics (CFD) based wind simulations in the structural analysis and design process of three-face billboards. We examine the aerodynamic behavior under various wind angles, highlight the benefits of using RWIND and demonstrate how simulation results enhance design safety and material efficiency.
Three-face billboards are commonly used for outdoor advertising, featuring a triangular prism shape with each face oriented 120° from the adjacent one. Their geometry makes them particularly vulnerable to multidirectional wind loading, especially in urban or open terrains. Conventional design methods rely on simplified wind pressure coefficients, which may not capture the complex flow separation, reattachment, and turbulence effects around the sharp edges and corners. Therefore, using advanced CFD simulations becomes essential for:
- Capturing realistic wind pressure distributions
- Evaluating face shielding effects
- Assessing torsional and bending loads under oblique winds
Geometric and Structural Characteristics
A typical three-face billboard consists of:
- Three vertical faces (often steel-framed with composite or aluminum panels)
- A central supporting column (concrete or steel)
- Diagonal and horizontal bracings
- Foundation subjected to moment and uplift forces
Wind Loading Challenges
- Oblique Wind Directions: All three faces are affected simultaneously with different intensity
- Vortex Shedding: Induces dynamic loads and possible resonance
- Shielding Effects: One face may partially shield others depending on wind direction
- Non-uniform Pressure: Local suction zones and reattachment areas
Advantages of CFD in the Structural Billboard Design
1. Accurate Wind Pressure Distribution
- CFD provides detailed Cp (pressure coefficient) maps across all three faces, capturing non-uniform loading caused by flow separation, turbulence, and suction zones especially near edges and corners.
- This helps avoid over-simplified uniform loads that may lead to unsafe or overdesigned structures.
2. Analysis of Multiple Wind Directions
- Unlike code-based methods that usually consider perpendicular wind, CFD evaluates wind from 0° to 360°, identifying critical oblique angles (e.g., 30° or 60°) that may cause the highest structural loads.
3. Captures Shielding and Interaction Effects
- CFD realistically models how one face shields another from wind, or how vortices form between the faces interactions that traditional methods cannot address accurately.
4. Assessment of Torsional Loads
- Three-face billboards often experience torsion due to asymmetric wind loading. CFD calculates moment coefficients, which are essential for designing base plates, anchor bolts, and foundations.
5. Optimized Structural Design
- Engineers can use CFD results to optimize member sizes, reduce unnecessary material usage, and design more efficient support frames.
- Enables value engineering without compromising safety.
6. Foundation Design Accuracy
- CFD enables accurate estimation of overturning moments, uplift forces, and shear at base level, improving the foundation design and reducing risk of tilting or failure.
7. Visualization for Client Communication
- CFD results offer visual outputs (streamlines, pressure contours, force vectors) that help communicate wind behavior clearly to stakeholders, clients, and authorities during design review.
8. Integration with Structural Software
- Tools like RWIND integrate with RFEM, allowing a seamless flow of data from wind simulation to structural analysis and code checks all in one ecosystem.
9. Support for Non-Standard Geometries
- CFD handles custom billboard shapes, supports mounted elements like lighting or solar panels, and adapts to real terrain unlike standards, which are based on simplified geometries.
10. Future-Proof and Research-Based
- CFD aligns with modern performance-based design trends and supports research-based validation, making it suitable for advanced engineering workflows and urban planning approvals.