Time History Analysis-Absolute Joint Displacement Problem

[ingdott]

hello,

I am carrying out a non-linear time history analysis. It is a 3D earthquake motion (the real time history acceleration graphs are used in each direction) starting after 1 second of Ramp function where I apply the dead load. And the analysis is based on Ritz vectors.

The problem is that I obtain excessively high "absolute displacements" in my joints. All the periods, accelerations and (relative) displacement results are reasonable. But I couldn't figure out why I have such big absolute displacements.

I tried to run a very simple frame example, the same thing happens. After a lot of tries and comparisons among different cases, I couldn't find anything wrong with the material, analysis cases, load cases, etc..

I guess the problem is with the time history data, even though it seems correct. I think I do the right scaling. I have a time-acceleration data, where the accelerations are in terms of "g", and in my analysis case, I scale the time history data by multiplying with "g" with the appropriate units.


Anyone has any idea about the problem?

I attached some tables if you want to see. (the units are N and mm)


Thanks

 

[ingdott]

table 2

 

[ingdott]

table 3

 

[IJR]

akanyilmaz

what is the natural period of vibration?

respects
ijr

 

[ingdott]

Hi IJR,

I have a solid prism of 2000x500x500 mm, with the full restraints at the joints, preassumabely the natural periods are very small, around 0,06 sec.

 

[IJR]

akanyilmaz

how about posting your .sdb file here. Makes checking easier for the rest of us

respects
ijr