When you say, "but I was getting deflection values 3 orders of magnitude higher than I was supposed to" I am confused by what you mean by the value you were "supposed" to get.  Do you mean the model was giving deflections thousands of times larger than an experimental measurement?  That sounds like a mistake in the model, either in the materials, the beam cross-sections, the loads or supports.

It looks like your structure is a welded frame and so I would not expect it to need any beam releases. 

If you were designing a suspension, where there were joints between the links, and you were modeling that with beams, you might use a beam release to represent a joint.

Please show a sketch of the loads and boundary condition on this model. Show the materials and the beam cross-section properties.

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