Reactions at plates corners vs. bolt group analysis?

[JBlack68]

To all,

If one considers a standard bolt group analysis (say a square pattern in the XY plane) with an applied load (Fx) at the centre of the bolt group
Shear force/bolt = Fx/4

If one however considers a square plate with full constraints at its 4 corners and a load in the x direction then one gets the reaction Rx = (-) Fx/4 but one also gets Fy reactions

Which method should one be inclined to "believe" if one was interested in the reactions (at the bolts)?

With the 2nd method one gets the stiffness effect of the plate and the fy load are the loads to stop the plate "shrieking" but one can get quite some high forces

Thanks
Regards

 

[gravityandinertia]

Always believe the one that is constrained closest to reality. In the second case, unless your corners are actually welded at each corner to something significantly stiffer (I would think >100X stiffer) than itself, reality isn't being represented.

I'm not 100% clear on what you are trying to do, but if you want to draw a picture and add a few more specific questions, I'm sure you'll get some better responses.

 

[rb1957]

if you over-constrain a problem you get "odd" results. Instead of hard constraints I suggest using finite stiffness rods (three rods at each node, X, Y, Z; say 1" long, area 0.1"; this allows the model to deflect tiny amounts that we don't account for in hand calcs). best approach is to constrain the model for rigid body motion (6 rigid constraints), and the rest finite stiffness.

another day in paradise, or is paradise one day closer ?