Hi Habib,
Agreed with the point what Habib whats to say in his privious reply.

Dear Aslam,
Yes we (stress Engineer) needs to know the mannual calcualtion before we are actually performing the stress analysis. it will always helpful. At the same time we must know what happens at site after we perform the analysis.
In spring hanger case I had seen on site that lot of maintainance engineer are facing problmes dealing with the springs.