I wish to clarify my initial query. I want to model a point along a beam where the point will not take a sag moment (behaving as a perfect hinge) but can transfer hog moment across. Is there a way to define an object (joint or other) which has an infinite stiffness for negative rotation (say, hog) and zero stiffness under positive rotation (say, sag) by specifying the moment-rotation characteristic (almost infinity moment if positive rotation and zero moment is negative rotation) of the object ?
