Recently news on high energies rockfall protection barrier has opened a discussion on the energy lmitis of the rockfall protection steel barrier.
Many people have asked me this: is a 8000kJ barrier equal to two allignment of 4000kJ barriers when impacted from the same block?? (see the image belowe).
The answer is very difficult and dipending to differnet factors.
To try answer I make before some considerations (we refer for example to ETAG027 guideline procedure testing):
- for the 4000kJ barrier (tested follow ETAG027) we don't know the behavior when impacted with an energy (ex. 8000kJ) greater than test energy (just 4000kJ);
- for the 4000kJ barrier (tested follow ETAG027) we don't know the behavior when impacted with a mass and velocity different from the test
For this reasons, if the impact energy is greater than the MEL Energy of the barrier, we can't say that (see drawing belowe):
For this reason my firs answer is that 4000kJ+4000kJ is different than 8000kJ in terms of behavior of structure..... but I don't know if 4000kJ+4000kJ is greater or lesser than 8000kJ.
In a next post I try to find a model to calculate the energy exit of the rockfall barriers (E-out) and try to answer to the question.
Discussion open !!!