The above doubt is clarified, but I wish to have another one regarding the calculation of skirt support itself, where the use of allowable compressive stress whlie calculating the required thickness values in both sides....

It is understood that the allowable compressive stress values are taken according to the unit stress that is calulated per unit length. Then resultant is checked weather the stress is compressive in nature or tensile ...
This method provides the nature of the stress, after that re calculate the stress values in both sides with the given values ...

Can anyone tell me the reason y the unit stress value determine the sign or nature of the resultant stress....
Y it is not same for actual stress values....