# How Ancillary EPA is Calculated ## **Ancillary EPA calculation method in Shapemaker** The Eurocode does not specify a precise method for calculating effective projected areas on ancillaries. However, a well-established approach is provided by the TIA-222 standard. This method involves calculating the EPA of the antenna faces — specifically, the normal face (EPA_N) and the transverse face (EPA_T). According to the TIA-222 standard, the total EPA of the ancillary can be determined using the following formula: $$ (\mathrm{EPA})\_A = K\_a \left\[ (\mathrm{EPA})\_N \cdot \cos^2(\theta) + (\mathrm{EPA})\_T \cdot \sin^2(\theta) \right] $$ where * $$(EPA)\_N = (cf \cdot A)\_N$$ * $$(EPA)\_T = (cf \cdot A)\_T$$ * θ is the relative angle between the azimuth associated with the normal face of the ancillary and the wind direction * Ka is the shielding factor associated to the ancillary for which we calculate the EPA - see here how Shapemaker calculates shielding factors automatically

‍ ### **Force coefficients in Shapemaker (c**_**f****)** Several ancillary shapes have been identified for which the force coefficients and the EPA are calculated. * box * cylinder * dish * plane lattice All ancillary types in the Shapemaker database are associated with a specific shape. * GSM/RRU/MHA/FTTA are box shapes * OMNI/GPS are cylinder shapes * All MW dishes are dish shapes * Dipole/Yagi are plane shapes

In Shapemaker there are 3 input methods for the force coefficient: 1. **(default)** calculated according to standards:
1. EN 1991-1-4 2005, Chapter 7.6, Chapter 7.9 and Chapter 7.11 for box, cylinder and plane lattice shapes respectively 2. TIA-222-I, Annex C for dishes 2. user input - specify directly the force coefficients for *Front*, *Side* and *Rear* of the ancillary 3. calculated based on forces from the manufacturer's technical sheets. ### **Example 1** ***EPA calculation of a box shape using EN 1991-1-4 and TIA-222-I*** Ancillary specification: GSM Antenna: H2000 / W400 / D190 / R20 (mm). Antenna azimuth: 0°. Wind direction: 60°. Dimensions below in meters.

In the **Shapemaker report,** the EPA is presented separately as *Area* and *c*_*f,A*. When you multiply them, you get the EPA for 60° wind direction. EPA=Area×cf,A=0.729×0.744 = 0.54 m²

To be able to show the values in the report in one line and make the ancillaries table more compact, Area and c_f are calculated as below. EPA = 0.54 m² Area=Afrontal⋅cos(θ)+Aside⋅sin(θ) cf,A=EPAArea ### **Example 2** ***EPA calculation of a dish shape using TIA-222-I*** Ancillary specification: MW Dish with shroud: Dia600 / Depth200 (mm). MW Dish azimuth: 0°. Wind direction: 50°. Dimensions below in meters.

**EPA in the Shapemaker report** EPA=Area×cf,A=0.283×0.932 = 0.263 m²

To be able to show the values in the report in one line and make the ancillaries table more compact, Area and c_f are calculated as below. EPA = 0.263 m² Area=Afrontal⋅cos(θ)+Aside⋅sin(θ) cf,A=EPAArea *** **EN 1991-1-4:2005,** ‍Eurocode 1: Actions on structures – Part 1-4: General actions – Wind actions. **TIA-222-I**, Structural Standard for Antenna Supporting Structures, Antennas and Small Wind Turbines Support Structures, Telecommunications Industry Association, September 2023. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.shapemaker.io/technical-details/how-ancillary-epa-is-calculated.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.