The way to find the plastic hinge

[burnningcat]

Dear FMK,

I analysis a 2D Frame with the beamwithhinges elements and the Fiber Sections. Because I need to see the development of plastic hinges, so I put some additional Fibers into the sections, with very small area, and in the locations of the steel layers.
My ideas is to record the stress-strain of these special Fibers, when the strain exceed the yielding strain of the steel, I consider the steel layer in the section has yield. Because the “Plain section remain Plian” assumptions, so I think this is a reasonable way to check if the steel in the element is yield. But I find that some location of the hinges are suspicious.

So dear FMK, would you please tell me if my way to check the hinge is correct? And is there some other ways to check the hinges? Thank you very much in advance.

[linguan118]

In my opinion, if you want to see the development of plastic hinges, you should use force-beam or displace-beam with intensive integration points, 'cause beamwithhinge has a fixed hinge length only monitoring the end section.

[fmk]

i have placed a codument describing the options .. the beamWithHinges is the modifiedRadau .. i suggest you read the paper by scott, as there is more than 1 section
when using the regular beamWithHinges command, you might want another option, i.e. midpoint.

http://opensees.berkeley.edu/wiki/index ... mn_Element