Thanks for the warm welcome guys.
eeek, looks like I'll have to elaborate a little to clear things up...
I'm trying to model an object (assume for now that it has infinite compressive and tensile strength if that helps) colliding with a 1m thick reinforced concrete wall. i know the tensile strength of concrete without reinforcements is tiny (~3 MPa which is ~3E6 N/m2, I think) but with the steel it goes up significantly. This is obviously tricky to calculate because tensile strength is measured according to surface area and reinforced concrete has not only rods of steel but also a steel-mesh buried within it.
Once that has been solved I'd like to start getting more specific about the projectile (eg. lead anvil --> human body).
I just don't know where to start to include all these parameters in a mathematical model so any direction helps.
Hope that helps a little...