problem with eleloads and eigen modes

[ngeorgal]

well after defining my model and getting the ten first eigen modes the first one seems to be rotational but the sap program outputs the same mode to be displsacement controlled.

My building is a four stage stell building with correct geometry as i can see both from the OSP and vees progs

More over i take wrong reaction forces at the basement columns, might sth is wrong with the transformation at beams ?- i have placed eleloads for every member ( wx for columns and negative wz for beams )

thanks in advance

ps
i defined all the elements with mass density in tones ( it is supposed to form a lumped mass matrix )

NG

[silvia]

you may have defined the transformation vector in the wrong direction.
if you look at the display procedures in example 6 (for 2D) and 8 (for 3D), there is an option to display the modal shape, and to display the model.
look at them and try them on your model.

[ngeorgal]

yes i know this option and i have visualizes the eigenmodes . i think that the eleload command has a problem , do you have any examples where a lumped mass matrix is formed by this way ?( eleload)

i still take the first mode rotational

[silvia]

the eleload command applies forces, not masses.
you have to define masses separately from forces.

[ngeorgal]

yes i have already done this silvia , but i think there is problem with nonlinear beam column element and mass density option !

please if you have an example with element definition ( mass density embedded) please send me or write down where can i find it .

NG

[silvia]

nope,
i don't have one.
can you please send me your files and a detailed description of your problem:
opensees-support @berkeley.edu

[ngeorgal]

ok silvia i send a zip file containing two versions of the file . The second one is the case using the mass command , but i failed again.

i am waiting for your valuable answer.

Thanks in advance
NG