I'm trying to model various static load responses for a short, thin walled, cantelevered aluminum tube. The length to diameter ratio is approx. 3 and the wall is 0.030 in thick. I've used shell and beam idealizations on seperate occasions and the results are within an order of magnitdue of each other. However, the Pro/Mech values are of an order-of-magnitude difference when compared to hand calculations. Any thoughts? The hand calculations are determine from beam theory that has been modified through experimentation. The reference is Roarke's Formula's for Stress and Strain by Warren Young, 1989, pg 201-2. Any thoughts?