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.

CC1CC2CC3
γE,kin1.01.051.15

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 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.

CC1CC2CC3
γT,R1.01.051.15

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?
    Click Here

  • Design Block

    How is the design block selected?
    Click Here

  • Energy

    What system capacity is sufficient?
    Click Here

  • Height

    What system height is required?
    Click Here

  • Anchorage

    How is an anchor verified?
    Click Here

  • Performance

    What other performance criteria are there?
    Click Here

  • Constructive Rules

    How can the system be safely adapted to a site?
    Click Here

  • Maintenance

    What recommended maintenance protocols exist?
    Click Here