The Partin report is at the core of the additional explosives conspiracy theories but his assumptions have a fatal flaw easily exposed by some very basic math. I’ll refer to one of the many copies of Parin’s report available on the internet;
“The maximum possible yield from 4800 pounds of ammonium nitrate would be obtained if it were in a compressed sphere and detonated from the center. That would produce a 4.4 foot diameter sphere of detonation products at about 500,000 pounds per square inch. By the time the blast wave hits the closest column, the pressure would have fallen off to about 375 pounds per square inch. That would be far below the 3500 pound compressive yield strength of the concrete. Any column or beam failure from the truck bomb would therefore have been from blast wave structural loading and not from any wave of deformation in the concrete.”
The crux of Partin’s argument is that an overpressure of 375 PSI on the closest column (G20) could not have failed it because 375 PSI is less than the concrete’s compressive strength of 3500 PSI. The column would not fail in compression though - it would fail from tremendous side loads. Failure in compression would be like putting a one inch square of concrete in a hydraulic press, 3500PSI concrete would require 3500 PSI of pressure to fail in compression. But construct a column of concrete one inch square and say ten feet long. Support the ends and load the middle, will it take 3500 PSI to fail it in bending? Of course not. This illustrates the difference of failure in compression and failure because of side load. Column G20 was 36” x 20” and over 20 feet tall. Lets talk about the 20” side being exposed to 375 PSI overpressure. At 375 PSI overpressure each foot of column G20 would have a side loading of 90,000 pounds. This means a ten foot section of column G20 would have a side load of 900,000 pounds. That is an instant side loading of 450 tons on a ten foot section of column G20, now consider the column is over 20 feet long. Do you think it would collapse from this kind of side loading? What totally destroys Partin’s analysis is using a 1457 PSI overpressure on column G20, something one of his own illustrations shows. This means the side loading on the same ten foot section of column G20 would be 3,540,000 pounds or 1770 tons of instant side loading.
There are other oversights in Partin’s analysis like the fact the Murrah bomb was ANNM (ammonium nitrate / nitromathane) not ANFO (ammonium nitrate / fuel oil) plus it was shaped. Shaping the charge can radically change the blast effect because of converging shockwaves (Munroe effect).
For more reasonable and logical analysis of the Murrah building failure mode see this link;
Blast Loading and Response of the Murrah Building http://www.terrorisminfo.mipt.org/pdf/forensicengineering2.pdf