Distributed loads

[user]

How can one model distributed loads on beams?

[seismosoft]

- Define distributed mass (through the inclusion of 'material volumetric weight' and/or 'section added mass' and/or 'mass elements') and then select the option 'Transform Mass to Weight' in the Mass Settings menu.
- Remember also that you may use the 'Stress Recovery' option (found in the General Settings menu) to obtain exact values of end moments for these cases (i.e. with distributed loading present). However, this will also slow down the analysis in a significant manner, hence use this option only when strictly required.
- All of the above is described in detail in the Help System of SeismoStruct, which we thus invite you to read carefully.

Seismosoft Support

[user]

Hi,

I did things as you suggest, but noticed that when using 'mass elements' I get wrong values of beam moments (they are constant), whilst with the use of 'material volumetric weight' and/or 'section added mass', the values are correct.

Am I doing something wrong?

Thanks.

[seismosoft]

Dear user,

Your observation is correct.

Indeed, as stated in the Help System, 'dmass' elements are not considered in Stress Recovery operations (because they are separate elements from the beams/columns), hence moment values throughout an element's length are bound to be wrong.

Therefore, if you are interested in obtaining correct moments throughout an element's length, you should define distributed mass/load using the 'material volumetric weight' and/or 'section added mass'.

Seismosoft Support

[nicknack]

Hi,

I'm trying to create a model to run eigenvalue, static pushover and dinamic time-history analysis on a concrete column and beams structure.

I don't understand how masses are computed while using "include rotational masses in distributed mass elements" (I'm comparing periods with the ones from SAP2000).

Also, I would like to know witch is the better way to model the structure for the time history analysis:
I'm using the "section additional mass" to have right static moments from dead additional loads on beams while running the static pushover analysis, but I cannot do it in the dinamic analysis because that way rotational inertia around z axis is too high (being mass concentrated on every beam).

So I had to use lumped mass elements to consider mx my and mzz right masses for each storey, but that way I have to put nodal forces on each beam to get right moments from additional dead masses and still get right periods for dinamic analysis.

Is that the right modeling to have the same model for static pushover and dinamic time history analysis?
Is there a way to have "section additional mass" non being considered in eigenvalues

[seismosoft]

Dear nicknack,

Apologies for the delay in responding:

- will the non inclusion of rotational mass in distributed mass elements not resolve your problems? Do you really need to include it?

- in any case, we can anticipate that the forthcoming release of SeismoStruct should feature a better handling of rotational inertia, which will hopefully address at least some of the difficulties you seem to have encountered

- there is currently no way in which a given mass can be precluded from eigenvalue calculations (though the user can simply remove such mass, if of no interest)

Seismosoft Support