Simple Supported Beam in FEA

[karthur1]

I have a beam that is simply supported and I am needing to do FEA analysis on it. Simply supported on the ends with a load in the middle.  Hand calculations show deflection is 2.256in.  FEA shows delfection as 1.247in.

I think the problem is the constraints that I have placed on it.  I have one fixed constraints at each end.  One of these needs to be fixed and the other needs to be able to move horizontally.  How do I set this up to get the correct results?

Thanks,

Kirk

[Anonymous]

I think you need to add a frictionless support to allow degrees of freedom to the horizontally moving end.

Someone will correct me if I'm wrong though 😉

[karthur1]

I totally agree with you, but I dont see a way to do that.

[Anonymous]

I just tried a quick example where I fixed the left end and applied a frictionless support to the other with a load pushing down and seems to work fine.

I notice you said about one end moving horizontally,  whichdoesn't sound right to me - do you mean it should move vertically like when you place a ruler on the edge of a table and "twang" it?

[karthur1]

Notice how the right end (where you place the frictionless constraint) is held vertical.  That is not the way it really should be.  The right end needs to be able to move horizontally like its on rollers. 

With it fixed on each end, the tension in the member reduces the amount of deflection from the center load.  If you do a rough hand calc for a simple supported beam and compare that to the results from your simulation, the simulation results will have less deflection.

[Anonymous]

Would an idea be to add a roller part at the end underneath (as per an assembly) and create a frictionless constraint between the two?

[henderh · Accepted solution]

For one of the ends to move freely horizontally, you can open up that DOF.

 Do this by unchecking a vector component in the fixed constraint applied to the edge at one of the beam ends (since we don't support adding a frictionless constraint to an edge using solid elements).

 Leave the other fixed constraint applied to the opposite edge as fixed in all directions so it will remain in static equilibrium.

Thanks, -Hugh