I am supposing that you want to alter the stiffness of your current system. As such you would be interested in the active stiffness of this system. And by active I mean the effects your system feels at current state. As such if you want to find out the rotational stiffness of your beam, as part of a frame, at the left hand support then you need to extract the rotation of the node in question and then divide it by the equivalent moment of the beam at hand at the same node. The reciprocal of this ratio is the active stiffness at hand. Multiplication of this number by 0.7 would then yield the partial fixity for 70% stiffness level. A word of warning regarding the units of all the above numbers. Hope this helps.
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