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Impact Loading with Timber 'Buffer'
- Thread starter dik
- Start date
Dik:
It seems to me that there has been a thread or two on this subject in the past; maybe in the mining or civil forums. The gist of the discussion was... bust a few inexpensive timbers to progressively absorb a bunch of the energy, thus lessening the energy finally delivered to the structure below. The falling material has kinetic energy, and this must be reacted, stored or absorbed, so as to reduce the final (lowest level) reactions. And, that turns out to be easier to say than it is to do. The various masses, velocities, time intervals for various interactions to occur, are not easy to pin down, but are needed to do the math. I think it pretty much becomes a good educated engineering guess for our kinds of problems. Just how much energy does a 8x8 absorb as it breaks, what about the 6x6's in the lower layers? How do you arrange these to make this a progressive failure mechanism, progressively absorbing more energy? It seems to me, that you would like to arrange your timber pyramid so the impacting load is transmitted, through bending and compression (storing energy), to lower layers which are the first to break, actually absorbing energy, which then leads to the second layer to break, etc. Think of the crumple zone in the front of cars, or the sand/water filled barrels which absorb energy when impacted.
It seems to me that there has been a thread or two on this subject in the past; maybe in the mining or civil forums. The gist of the discussion was... bust a few inexpensive timbers to progressively absorb a bunch of the energy, thus lessening the energy finally delivered to the structure below. The falling material has kinetic energy, and this must be reacted, stored or absorbed, so as to reduce the final (lowest level) reactions. And, that turns out to be easier to say than it is to do. The various masses, velocities, time intervals for various interactions to occur, are not easy to pin down, but are needed to do the math. I think it pretty much becomes a good educated engineering guess for our kinds of problems. Just how much energy does a 8x8 absorb as it breaks, what about the 6x6's in the lower layers? How do you arrange these to make this a progressive failure mechanism, progressively absorbing more energy? It seems to me, that you would like to arrange your timber pyramid so the impacting load is transmitted, through bending and compression (storing energy), to lower layers which are the first to break, actually absorbing energy, which then leads to the second layer to break, etc. Think of the crumple zone in the front of cars, or the sand/water filled barrels which absorb energy when impacted.
- Thread starter
- #3
Thanks dhengr... I've searched through the various threads and not found anything. I don't know what the crushing-time dependant hysteresis is for this type of loading of timber. Ignoring the effect of the timber results in 'huge' forces...
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