## Energy Capacity

The design energy capacity of the mitigation structure is determined by comparing the design energy (action energy) with the resistance capacity (energy) of the structure. Various partial factors of safety are applied in order to compensate for uncertainties in the modeling results, as well as simplifications during product testing such as idealized impacts in the middle of a field and height of a fence panel, simplified block form, absence of rotational energy, etc.

## Action Energy

The design value of action energy TE,d is based on the characteristic energy as determined by rockfall analysis results, which are carried out by the state-of-the-art techniques, and the product of a partial factor of safety according to the consequence class. The 99th fractile of the energy distribution for the design block generated from simulations is used for the characteristic value of energy (TE,k). The partial factor of safety (γE,kin).

TE,d = TE,kγE,kin

whereby

TE,d : design value of action energy
TE,k : characteristic value of modeled energy that is equal to T99[design block]
γE,kin : partial factor of safety as per table.

 CC1 CC2 CC3 γE,kin 1.0 1.05 1.15

## Resistance Energy

The design resistance value of energy TR,d is based on the available commercial characteristic energy capacity of a structure (Tk,MEL) according to ETAG 27 or EAD 340059-00-0106 guidelines reduced by a partial factor of safety according to the consequence class. The partial factor of safety (γT,R) is defined as per the table below.

TR,d = Tk,MELγT,R

whereby

TR,d : Design resistance of energy (capacity of fence)
Tk,MEL : Maximum Energy Level (MEL) energy class according to product approval (ETAG 27:2012, Clause 2.4.3.2)
γT,R : Partial factor of safety as per table.

 CC1 CC2 CC3 γT,R 1.0 1.05 1.15

## Verification

For the verification of design absorption capacity, the design action value of energy must be smaller than or equal to the design resistance value of energy as follows:

TE,dTR,d

Next Step

## References

EOTA (2012) ETAG 27: Guideline for European Technical Approval of Falling Rock Kits. Brussels, Belgium.

## Step-by-Step Guide

• #### Consequence Class

What level of risk is there?

• #### Design Block

How is the design block selected?

• #### Energy

What system capacity is sufficient?

• #### Height

What system height is required?

• #### Anchorage

How is an anchor verified?

• #### Performance

What other performance criteria are there?