Using "Force Controlled" Frame Hinges

[Sostratus]

I am trying to get a handle on using plastic hinges in preparation for a more complex model in SAP2000 V12. I started off with a simple 10' column which is fixed at the base. A horizontal load is at the top and a hinge is at the center. Under "Define Frame Hinge Properties", I selected "Force Controlled" and "Moment M3". I then modified the Hinge Property further in "Frame Hinge Property Data for FH1 - Moment M3" by entering a user specified moment and by selecting that the hinge loses all capacity.

After analysis, when the deformed shape is displayed the hinge is shown in red since it failed. As expected, the deflection is higher than it would be without a hinge present. What I do not understand is why the M3 moment and V2 shear graphs are the same with or without the hinge. My understanding is that since the maximum moment for the hinge was specified, the behavior of the column would be normal until that moment is reached. Then a hinge would form, and the column would be able to withstand nothing or the specified max moment (depending on whether you defined the hinge as losing all capacity or not). Either way, the moment and shear diagrams would change from a column with no hinge.

My test model seems to indicate that the formation of a user defined hinge affects the deflection but does not alter the moment or shear graphs. Why is this? Thanks!

 

[agostage]

I haven't used the hinge function in SAP much but it seems to me that if your hinge has failed your column would then be unstable and no moment or shear would be valid. SAP is probably spitting out the last diagrams that were solvable. What I would do is make a frame with a single hinge that has enough redundancy to be stable after a hinge forms. Then investigate your diagrams.