Seismosoft | Earthquake Engineering Solutions

I have model two column so that they are conected with two link element on the top and two ones at the bottom and the one link at the middle so they are conected to other with the middle link I define the elastic frame for column and I define the maas/length in the elastic frame section the analysis type is egin value and non linear dynamic time history.as my model is a planar model therefore I want to define the maas/length just in x direction so the question is how can I define the distributed mass in the x direction only and if i must mark the automatically transform mass into gravity loads or not? in the case of concentrated mass if i must mark the automatically transform mass into gravity loads or not?
tanks alot

I saw the verification examples but in some examples the automatically transform masses into gravity loads are marked and in the others are not marked so Iam wandering when I must activate this option in the egin value and time history analysis

Hi khajehdehia.

If you will go to the "Tools" -> "Project Settings" -> "Gravity and Mass" tab, you will find the capability of defining the global mass directions, whether or not to automatically transform gravity loads to masses, and whether or not to include rotational masses in distributed mass elements.

To limit your eigenvalue problem to the x-direction you could un-check all boxes except "X" (and perhaps "Z" and "RY") depending upon the details of your model and the behavior you wish to capture. You should be able to look at the ensuing mode shapes and get an idea of its appropriateness.

You will likely also have to un-check the "include rotational masses in distributed mass elements" box to get strict x-direction modes. Try it both ways and see how it affects your particular model.

Whether or not you automatically transform gravity loads to masses is entirely up to you and depends on the source of true mass in the structure, whether or not you prefer to use distributed mass elements,etc.

I hope this helps khajehdehia. And best of luck.

actually I analyzed the model one time with the concentrated mass another time with the corresponding distributed mass but unfortunately
for instance the relative top displacement for two models have a bit differences while my teacher said to me the differences must be few
on the other hand would I check the automatically transform masses to gravity loads ? in my model the dmass is caused by the weight of columns
so should I check the option or not if yes ,should I check the gravity load direction in x or in -z direction, in the case of concentrated mass how is it? other question is I know I must restrain all the nod in y,and rx,rz except for support but I have also link nodes should I restrain them in the abovementioned direction or not
tanks