Frontal Project Area (FPA)

What is a Frontal Project Area (FPA)?

A Frontal Project Area (FPA), or projected frontal area, defines the exposure area to wind forces in square feet. FPA can be thought of as the 2D shadow of a specific component or the entire structure that is perpendicular to the direction of the wind.

FPA is used to design and install components that can withstand wind loads anticipated for the region. Calculating projected frontal area is concerned with finding the 2D area, so formulas vary based on the component, for example:

  • Microwave antenna: π * r2 
  • Panel antenna: width * height

FPA calculations are used throughout the effective projected area (EPA) calculations, both of which are critical for understanding how much wind force a structure can withstand. Making design changes to improve resilience and being able to communicate wind force to engineers is critical.

What is an Effective Projected Area (EPA)?

EPA is a coefficient used to determine the total wind force that can be applied to a specific structural component when considering the entire 3D shape. While FPA is 2D, EPA expands on these calculations to better understand resistance. 

FPA and EPA go hand in hand to ensure each component and the total structure are as durable as possible while communicating maximum wind force to engineers. 

How is EPA calculated? The overall formula is:

 

EPA  = FPA * DC (Drag Coefficient)

 

While this formula may look simple, it becomes more complex for specific components as the equipment depth must be understood to calculate the drag coefficient first.

FPA and EPA Application for Telecommunication Towers

FPA and EPA are widely used to understand the wind force a given structure can withstand before problems will occur. 

The telecommunications industry strongly relies on components and structures to remain operational in high wind loads. So, let’s explore a few specific applications of wind load calculations for tower companies. 

Structural Design

Tower companies must be aware of the estimated maximum wind force in the given area before installing any specific towers. Any equipment bought from vendors, the modeling process, and the overall construction process must remain aware of the maximum wind load to prevent future issues.

Engineers use several methods to ensure towers are resilient, especially when constructed in windy areas. A few design choices that involve continually calculating EPA and FPA are:

 

  • Material selection: Selecting materials that do not have excessive bending or vibrations when subjected to high wind loads is a critical choice when designing each component. For components, prioritizing low-drag finishes when possible can improve resilience.
  • Aerodynamic features: Designing aerodynamic features that reduce drag or use vents for wind pass-through can reduce the total EPA. Rounding off corners, for example, goes far in reducing drag.
  • Foundations and dimensions: Engineers use EPA to determine the total dimensions of the tower, which includes the length, width, and depth of the foundation. Towers intended for high wind load areas may require deeper foundations, which makes ongoing EPA calculations critical.

Maintenance and Inspections

Towercos depend on frequent maintenance and inspections to keep services up and running. Identifying damage as soon as possible allows technicians to implement repairs, but staying aware of the FPA or EPA throughout the process is vital.

Adding new components to a tower, whether upgrades or replacements, can change a tower’s EPA. Technicians need to be aware of these calculations to ensure the resilience of specific maintenance tasks.

Additionally, wind patterns change over time. Towercos need to stay aware of the maximum wind force each tower can withstand, and if force is expected to exceed these limits, maintenance or other corrective actions must be taken before any issues occur.

Safety Regulations

Specific jurisdictions have unique building codes and requirements concerning telecommunication. In the United States, TIA-222 sets forth the requirements for structural safety, which includes wind load calculations. Understanding EPA during design and construction is necessary to meet these requirements and reduce the risk of structural failures.

Additionally, construction projects will generally require permits or certifications before proceeding. Providing specific project details is necessary given the go-ahead and involves providing a range of specifications about the future project — including EPA and maximum wind loads. Demonstrating the safety of the future structure is of the utmost importance.

On top of legal requirements, building structurally sound towers is necessary to maintain the local area’s safety, ensure services are available, and build a lasting business.