Differences in Breaching Charges: What does that mean?
 

For an encounter group I am making for my game, I needed to get some stats for a 90mm gun round. The penetration listed for it is "8 inches of double-reinforced concrete". This shouldn't be a problem, just look up the breaching charge for that and done. But here is the problem I have. In 4ed, the listing just says reinforced concrete, just like in the 3rd edition. But when you look at the amount of C4 for breaching, the 4ed amounts are about double the 3rd edition amounts all the way up the scale. The same is true for armor value of reinforced concrete between the editions. This could be because of the increased use of double-reinforced concrete between the publication of the two editions.

Now I am not a civil engineer, but I do know my physics. I now know what the difference between single and double-reinforced concrete is, but I can't find a relatively simple answer to a naive question. That being is double reinforced concrete basically twice as resistant to breaching as single reinforced concrete? I really don't want to look up a bunch of physical properties of concrete and steel to do the calculations myself. The answer doesn't even need to be exact. I just want a ballpark, bar napkin approximation of the relative strength. Does anyone here know the answer for the sake of my sanity?

I’m not an engineer but work with several dozen civil/structural engineers. I asked around and the simplified answer I got was, “not necessarily”. There are too many variables, reinforcement sizes, spacing and pattern, beam or wall thickness, concrete compressive strength, etc. have to be taken into consideration to arrive at an answer before any of them would make a definitive statement. In other words. being engineers, they aren’t saying anything until after they calculate it.

That said, I did come across the attached at some time. I think I saved it intending to go down the path you're on now. The paper gets into the math around page 11. If you do end up doing your own calculations, hope this helps.

Thanks for the PDF. I will have a look and see if I can make some simple approximations as I did with the Gurney equations for grenades.

Yeah, those engineers. Why can't they be like experimental physicists. Close counts to build the experiment, as long as we don't end up blowing up the planet..... usually.