asdeasoft.net

Dear STKO Team：

I build the two story frame in ETABS and STKO, because I want to compare the results of modal analysis in different program.

After I check the result, the result of the third mode (torsional mode)in ETABS is different from the one in STKO.

Then, I try to put the rotational mass in STKO, but the result is still weird. (The distance from mass center to node mass is about 1.5m, so the rotational mass =(1.5^2+1.5^2)^0.5 * (node mass).) Do I put the wrong value in STKO?

How could I solve the problem? I think the result in ETABS is correct, and there maybe something wrong in my model in STKO. Because I check cumulative modal participation masses in STKO, the MX MY and MRZ don't reach 100%. The following is my model and the results in ETABS and STKO.

Any advices and helps that you provide are highly appreciated.

Best Regards

After I check the result, the result of the third mode (torsional mode)in ETABS is different from the one in STKO.

You are right. Right now, the script you are using is simplified, and considers (for rotational partiticipation factors) only the direct rotational masses (if applied) and not the effect of the "rotation" of translational masses about the center of gravity.
We are working on it right now, I will let you know when it is ready.

Because I check cumulative modal participation masses in STKO, the MX MY and MRZ don't reach 100%.

This is normal, because STKO computes the total mass of the structure as the sum of all masses (also those in the fixed DOFS). However those fixed masses will bever be excited. That's why it will never reach 100%. We checked other softwares such as ETABS and MIDAS Gen, and in fact they compute the total mass (for modal masses) excluding the fixed ones.
We will include also this in the new script

Dear STKO Team：

Thank you very much.

I look forward to your new script.

Best Regards