Diaphragm rigid

[civil]

so
1- i could not use equalDof in both steel frame an concrete frame when the element are nonlinearBEamColumn (forceBeamColumn)?
2- and i could use it for both steel frame an concrete frame when the element are nonlinearBEamColumn (dispBeamColumn)?

[Tas]

Civil, if you are refering to me, these that you pointed out are the opposite to what i wrote:

i) If you are using RC fiber section module, either with FBE or DBE, the use of equalDOF or diaphragm results in additional and not realistic axial forces (+additional moments),
ii) There is no such problem if you are dealing with (any kind of) Steel elements.

[civil]

i really confused!!

dear fmk and other friends,
could you please tell me the final result in using equalDOF and the effect of nonlinearBEamColumn (dispBeamColumn & forceBeamColumn) and frame type (steel frame & RC frame) for consideration rigid diaphragm in 2D model?

thanks in advance

[Darcycpoes]

depends on your structure?

[Lost]

If the section you are using is symmetrical in shape, has symmetrical materials with the same stress-strain laws in tension and compression (such as steel sections), then you can use the rigid diaphragm. In any other situation (such as reinforced concrete sections), it will produce wrong results with any kind of inelastic response element (that means either force- or disp-beamcolumn, see here: http://opensees.berkeley.edu/wiki/index ... nsequences at the end of the page). The "correct" response would be that the beams develop little axial forces, so in order to simulate that, together with the diaphragm, you could release the axial force at one end of the beam (using a zerolength element with 2 dofs, no axial)

[civil]

dear vesna
could you please clarify me?

[Tas]

Civil, i would suggest to read carefully Vesna's presentation about this issue (as i also did) and specially page 4.
However, i think that it should be confirmed (or not) from Vesna or fmk, if DBE should not be modeled together with equalDOF as it is for FBE and as concerns RC fiber elements, in order to be clear for anyone that reads this topic.

[civil]

civil wrote:
> dear vesna
> could you please clarify me?

any suggestion?

[fmk]

no problem as long as the aggregator is not usning a fiber section.

[geoStru]

no problem as long as the aggregator is not usning a fiber section.

hello fmk,
I built a 3d RC frame with nonlinearbeamcolumn elements for columns and beams. I use the rigid diaphragm but the values are wrong. How could I resolve the problem for the beams?
I tryed to introduce a equaldof (beams) for put 0 the axial deformation but the anlysis didn't converge