Element classes for steel space frame with rigid joint

02-Getting started with the modelling
Post Reply
Hanif Nanda
Posts: 8
Joined: 20 May 2022, 15:17

Element classes for steel space frame with rigid joint

Post by Hanif Nanda »

I'm working on my final project on electric transmission tower with L steel material as shown in the photo. What element classes is suitable for my project? and why?
Image
huffte
Posts: 941
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Element classes for steel space frame with rigid joint

Post by huffte »

The answer depends on what you wish to accomplish. Are you analyzing for loadings in the linear elastic range? If yes, then use the "elastic frame element".

Are you doing an inelastic pushover analysis using non-sub-divided elements between nodes? If yes, then the "inelastic force-based frame element" could be the best choice.

Are you doing an inelastic pushover analysis using sub-divided elements resulting in relatively short elements? If yes, then the "inelastic displacement-based frame element" could be the best choice.

Dynamics time history analysis? Then the element type will depend on the level of inelasticity you anticipate.

So, you really need to study the various capabilities, limitations, and advantages of each element class. And you need to consider the type of analysis you will be doing.

One of the great things about SeismoSoft is that you learn so much in the modeling process. I encourage you to do so. You will be glad you did.
Tim Huff
Hanif Nanda
Posts: 8
Joined: 20 May 2022, 15:17

Re: Element classes for steel space frame with rigid joint

Post by Hanif Nanda »

Thank, for your answer.
I did an adaptive pushover analysis. Based on what you said "relatively short element". What is the maximum element length? If doing adaptive pushover analysis, which is more accurate, force-based or displacement-based?
huffte
Posts: 941
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Element classes for steel space frame with rigid joint

Post by huffte »

It would be nice if there were easy answers to such good questions. This is not the case, in general. Rather than re-inventing the wheel, I'll provide some quotes from the excellent SeismoStruct Help System:

Regarding the force-based inelastic element:

"As discussed in Material Inelasticity, element infrmFB is the most accurate among the four frame element types of SeismoStruct, since it is capable of capturing the inelastic behaviour along the entire length of a structural member, even when employing a single element per member. Hence, its use allows for very high accuracy in the analytical results, while giving users the possibility of readily employing element chord-rotations output for seismic code verifications (e.g. Eurocode 8, NTC-08, KANEPE, FEMA-356, ATC-40, etc)."

Regarding the displacement-based inelastic element:

"In order to approximate nonlinear element response, constant axial deformation and linear curvature distribution are enforced along the element length, which is exact only for prismatic linear elastic elements. Consequently, infrmDB should be employed with members of small length, leading to the need for a mesh refinement, in order to achieve good accuracy in the case of higher order distributions of deformations. Typically, 4 to 6 elements per structural member need to be defined, hence users need to post-process nodal displacements/rotation in order to estimate the members chord-rotations [e.g. Mpampatsikos et al. 2008]."
Tim Huff
Hanif Nanda
Posts: 8
Joined: 20 May 2022, 15:17

Re: Element classes for steel space frame with rigid joint

Post by Hanif Nanda »

Thank you
Post Reply

Return to “02-Getting started with the modelling”