question about infill wall model in sap2000

[abouferass88]

Can anyone share his knowledge in modelling of the infill wall for pushover analysis using sap2000?
if you can share any simple model file, it will be appreciated.

[mig21]

hi

check out eurocode 8 and the australian code ,, they give directives how to model infills that you can use in sap2000.

you can find them in the forum
regrads

[abouferass88]

Dear mig21

if you meant the theoretical background in the euro code, i have read all the literature about this topic but i cant model it using sap. i want simple 1 frame model or clear procedure to get the point.

Best regards

[mig21]

i will try to post a simple model as soon as possible for discussion in the forum
regards

[Badis]

Check also this post, you will find some documents directly related to your request

Code:

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[ivanveliki]

A collegue of mine just wrote a PhD thesis on masonry infill modeling (with my help :yes:), where she suggests a very good (quite accurate) model for infill walls using SAP2000 (or other software), but it is not yet thanslated into English. Also the procedures for becoming a PhD will be finished at the end of the year, and I cannot reveal any details yet. As soon as she becomes a PhD, I can translate some of the results and then publish them here.

[Sumatra]

Hi abouferass88,

Infill wall (commonly for masonry or brick) can be practically treated as a bracing element (compression-only element with moment released or pinned)). There are 2 ways in modelling a limit state of infill wall element for pushover analysis using SAP2000:
1) using tension/compression limits
2) using hinge element

tension/compression limits:
a- create a bracing by clicking draw frame/cable element, adjust moment release to be pinned
b- specify the section (see the code for defining the equivalent section's depth of wall)
c - select bracing element> Assign > Frame > Tension/Compression Limit > enable Compression Limit and specify the compression strength of your wall
d- drawback of this way is the plastic hinge progress can not be monitored (visualize) after the analysis. If you want to see the hinge progress, use the hinge element

hinge element:
a- to b- are the same as aforementioned
c- Define > Section Properties > Hinge Properties > Add new properties > User Defined > Force Controlled (Brittle) > Axial Force > Specify the yield force using User specified force > Specify the acceptance criteria (will not affect the result but will help us to see the hinge progress in colorful dots)
d- Specify the hinge position by select the bracing element> Assign > Frame > Hinges > select hinge property > add 0 and 1 for relative distances (hinge at both members end)

P.S. If you can define the force-deformation curve of the infill wall, you can use hinge element with Deformation Controlled (Ductile) so that the hinge progress can be set-up in deformation manner as well.

Hope it helps :mail1:

Regards,
adekajeng :JC_handshake:

[abouferass88]

dear adekajeng

It is very very helpful
Also i have a question:
is it one or two cross compression element for each infill wall

regards

[Sumatra]

Hi abouferass88,

If the intention is only for a common 2D pushover analysis with one direction of lateral loading (or 3D with regular in plan), a single diagonal compression member is sufficient. However, there will be no problem if you provide two diagonal compression members for this case, since the program will activate this member only when the compression force applied. It is meant when one of these members compressed, the other would be tensioned (= axial force equal to zero).

For pushover analysis of 3D structural system with irregularity in plan, providing two diagonal compression members is necessary because we need to analyzed the structure in two main directions. This is also the case if you want to run nonlinear time history analysis either for 2D or 3D structural system as well as for regular or irregular in plan / vertical.

P.S. Make sure you deactivate the selfweight of this compressional member to avoid additional axial force on this member.

Hope it helps.
Adekajeng

[abouferass88]

hi adekajeng

i will start model the infill wall as compression member and will continue the discussion with you and other collegue in the forum.

Regards