Dear all,
i am trying to model 3D plate model with the application of compression springs both at base and side walls and have some doubts regarding that:
1) Initially i was trying to apply "load combination" command to add the respective loads but after going through staad literature i found that "repeat loads" were to be used in this case.
Upon the application of repeat loads i noticed close to 50% decrease in the bending moment . Isn't this decrease too large or am i making some mistake?
2) In order to reduce bending moments, i applied joints using the release option in plate specifications for the whole structure. But to my dismay, i see no perceptible decrease in the maximum bending moment (rather an increase in bending moments?? why is this happening?
3) Also regarding application of release, i am confused about direction in which they are to be applied. Figures below show 2 directions in which releases can be applied, which one of them is correct?
OR 
4) Also, i would need some advice on the support conditions to be employed. Should i use fix boundary conditions at corners of base (with intermediate nodes being attached to spring) or should i go for Pinned/fixed boundary condition on top of side wall as shown below
