Linear beam-column element, shear deformation?

[Nero]

Just wondering if anyone knows- does the linear beam/column element take into account shear deformation?? If so, what shear area does it use? The element cross sectional area? A percent of this area?

[silvia]

i don't know about that, but you can always use a nonlinear element with an elastic section, and then aggregate shear.
silvia

[Nero]

i don't know about that, but you can always use a nonlinear element with an elastic section, and then aggregate shear.
silvia

Hi silvia-

I may end up doing this, but for now am just trying to verify some results I am getting. My OS simulation results match almost perfectly the hand calculations which include shear deformation, but most linear beam/column elements dont include shear deformations. If the elastic beam/column elements dont include shear deformations, then my current model is much more flexible than my hand calcs would predict...

[silvia]

i think there is a problem with your model or hand calc's.

[els83]

I have the same problem,

I modeled a simple 7DOF system with BeamColumn elements. I restricted all DOFs except the DOF 1. I expected to have the stiffness matrix of a shear building and calculated the eigen frequencies. they are not what I get from opensees as modal frequencies. But when I model the same system with axial elements with the same stiffness the modal frequencies are the same.

What is the problem, is OPENSEES modeling the the system with BeamColumn element more flexible (modal frequencies are less than what is expected).

[jcobando]

I developed a model in OpenSees and I compared the same model with SAP2000 the results did not match until I considers as zero the shear area in the frame sections in SAP2000.

Then, OpenSees do not considers the shear deformations in a linear model of columns and beams.

I would like to know how to consider shear deformations in a linear model in OpenSees?

[Jhno]

els83 wrote:
> I have the same problem,
>
> I modeled a simple 7DOF system with BeamColumn elements. I restricted all
> DOFs except the DOF 1. I expected to have the stiffness matrix of a shear
> building and calculated the eigen frequencies. they are not what I get from
> opensees as modal frequencies. But when I model the same system with axial
> elements with the same stiffness the modal frequencies are the same.
>
> What is the problem, is OPENSEES modeling the the system with BeamColumn
> element more flexible (modal frequencies are less than what is expected).

I did model a simple lolipop (3-DOF, simpler than yours) system in OpenSees and compared the stiffness matrix with my own hand calc. I got the same answer, provided I consider the rotation of the local stiff. I used ElasticBeamColumn element. The eigen frec. matches also. Maybe cross-check your units inputs and the rotation matrix? Hope it helps.