01-10-2012, 06:13 AM
Dear Magicstone,
As Ynopum mentioned typically you make a fit of the data using the "square root of the sum of the square method", a.k.a. SRSS, to obtain a coefficient. It is called an empirical formula because you obtain it from matching common parameters from several experimental runs.
The number obtained from the SRSS fit is not derived from mathematical logic, it is derived from changing one variable at a time through several experiments. From only changing a variable at a time a number will emerge using the SRSS method. This is the number you are looking for. It is more of an Statistical Approach, than a physics understanding approach. Hence the name empirical.
Hope this helps your investigation. Personally, I am not a big fan of AASHTO, I rather the simpler approach presented by ACI. Although AASHTO still rules most of Highway designs.
Kind regards,
MDMH
As Ynopum mentioned typically you make a fit of the data using the "square root of the sum of the square method", a.k.a. SRSS, to obtain a coefficient. It is called an empirical formula because you obtain it from matching common parameters from several experimental runs.
The number obtained from the SRSS fit is not derived from mathematical logic, it is derived from changing one variable at a time through several experiments. From only changing a variable at a time a number will emerge using the SRSS method. This is the number you are looking for. It is more of an Statistical Approach, than a physics understanding approach. Hence the name empirical.
Hope this helps your investigation. Personally, I am not a big fan of AASHTO, I rather the simpler approach presented by ACI. Although AASHTO still rules most of Highway designs.
Kind regards,
MDMH