Seismosoft | Earthquake Engineering Solutions

hi,

I have basically two problems:

-one is with modelling simple one bay 2D steel frame structures with two or more storey and with infill panel elements between steel frame: dynamic time history analyisis for that kind of structure did not work (but, for example, for just ONE infill panel in structure,independently on which storey, analysis is possible)

- another is damping - I want to compare results of dynamic time history analysis for the simple steel frame structure and the same acceleration data for calculation in ROBOT Millenium software and Seismostruct - I am using elastic frame elements with NO damping (in element definition and also in global definition of damping) but in Seismostruct I anyway see taht some damping exist??? (no "harmonic" configuration of displacement/force figure and damping force exists?)

THANK YOU very much for help in advance!

GFOS, Croatia

Hi,

- for what concerns the difficulties you report regarding the use of infill panels, it is difficult for us to provide assistance without further information. If you send us the models, we may try to have a look at them when the time will be available (which however will not be in the immediate future, we note).

- with regards to damping, what you report does seem peculiar. Again, if you send us the model, we will have a look at this issue. (we did not understand your final comment on "harmonic configuration", but perhaps you may clarify this in the email accompanying the models)

SeismoSoft Support

Thank you very much for your promt answer.

I will send you my models on e-mail - info@seismosoft.com

Best regards,

GFOS Croatia

We have now looked into your files, and note the following:

1) there does seem to be indeed a problem with the infill panel element, which could partly originate in a bug and partly in the properties of the infill. Can you please run a simple cyclic analysis (and then dynamic) on an isolated panel element and check if all seems ok?

2) as discussed in the Help System, the HHT integration algorithm does introduce numerical damping. If you use the Newmark algorithm instead (with the default "non-dissipative" parameters), then damping forces will be wholly eliminated (as you can check yourself in the Post-Processor module).

SeismoSoft Support

Hi,

thank you verry much for promt response!
I am allready checked simple frame with one storey with infill panel elements and everything working fine (one same example I solved on "cllasical" way with equivalent diagonal strut approach in ROBOT, and obtain results are similar in Seismostruct, for push-over analysis). I tested also time - history analyis for this one storey frame with infill elements and no message of erros appear.

I will send you this model on e-mail.

Best regards,
gfos

Hi,

We have checked the model you sent us, and can confirm that there was indeed a bug with the infill panel model. This bug will be corrected in the next release of the program.
We also note the current default properties of the infill panel lead to excessively stiff elements, and thus we will also be changing these defaults in the upcoming release.

Many thanks for having signaled this problem to us,

SeismoSoft Support

Hi,

I also experienced the same problem for the infill panel elements in reinforced concrete frame. Is there any other way to model the infill walls for dynamic analysis?

Thank you in advance for your help.

Best regards,
Marie

Hi Marie,

You may of course employ diagonal struts with a non-infill hysteretic behaviour. It is a more approximate modelling, but it will certainly work.

Kind regards,

Seismosoft Support

Hi,

Sorry if my question is a very basic question: what is the right way to model the diagonal strut (i.e element is only acting for compression)? if I model it with truss element it will take into account the tension also. Thank you in advance for your help.

Best regards,
Marie

Introduce either a non-tension material in the section definition or a compression-only link at the ends of the element.

Seismosoft Support