Why does not the period change even though shear is included

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emrekizilarslan
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Joined: Wed Mar 29, 2017 6:21 am
Location: SUNT at Buffalo

Why does not the period change even though shear is included

Post by emrekizilarslan » Fri Apr 27, 2018 2:17 pm

Hi all,

I added "section aggregator" in order to add shear stiffness to the stiffness matrix. however, the period did not change. I did not see any problem with running but i feel like the period should change once the section aggregator is added. Thank you for answer in advance...


here is the part of the section aggregator in my code:

## For wall section

set G_shear [expr 11200.0*$ksi];

set matShearTagWall 3001;
uniaxialMaterial Elastic $matShearTagWall [expr $G_shear*$AgWall];
set matShearTagCB 3002;
uniaxialMaterial Elastic $matShearTagCB [expr $G_shear*$AgCB];

set secWallTag 123;
set secWall2Tag 124;
section Aggregator $secWallTag $matShearTagWall Vy -section $secWallTag_PM;
section Aggregator $secWall2Tag $matShearTagWall Vy -section $secWall2Tag_PM;

## For CB section
set secCBTag 1023;
set secCB2Tag 1024;
section Aggregator $secCBTag $matShearTagCB Vy -section $secCBTag_PM;
section Aggregator $secCB2Tag $matShearTagCB Vy -section $secCB2Tag_PM;

selimgunay
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Re: Why does not the period change even though shear is incl

Post by selimgunay » Sun Apr 29, 2018 7:32 pm

It should change at least slightly. Just to check you can multiply G by 10000 and see if there is any difference

emrekizilarslan
Posts: 7
Joined: Wed Mar 29, 2017 6:21 am
Location: SUNT at Buffalo

Re: Why does not the period change even though shear is incl

Post by emrekizilarslan » Mon Apr 30, 2018 4:41 pm

Hi Selim,

I also tried that but the period did not change. I am sure that after adding the combined shear stiffness to cross section, I am assigning that combined cross-section to elements used (100% sure). i am guessing i cannot add because of either

- type of element (dispBeamColumn), or
- I am adding force-disp. relation for shear to stress-strain for flexural.

Am i right?
Last edited by emrekizilarslan on Thu May 03, 2018 8:58 am, edited 1 time in total.

fmk
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Re: Why does not the period change even though shear is incl

Post by fmk » Wed May 02, 2018 8:17 pm

sorry .. shear aggregator does not work with disp based elemnets, only forced based include shear defo effects if provided in the section.

emrekizilarslan
Posts: 7
Joined: Wed Mar 29, 2017 6:21 am
Location: SUNT at Buffalo

Re: Why does not the period change even though shear is incl

Post by emrekizilarslan » Thu May 03, 2018 9:05 am

Thank you so much for your reply. is there a way to include the shear stiffness externally to fiber model then? i would really appreciate if there is. i cannot use "Flexure-Shear Interaction Displacement-Based Beam-Column Element" as it does not allow to use "P-delta" geometric transfer, which i will need to use.

fmk
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Re: Why does not the period change even though shear is incl

Post by fmk » Thu May 03, 2018 6:02 pm

you cannot use with disp beam element, your only choice is to switch to forcebeam element .. or put element in parallel with a force beam element with negligably small elastic section (can't be too small as has to invert it) and the shear aggregator you are using.

emrekizilarslan
Posts: 7
Joined: Wed Mar 29, 2017 6:21 am
Location: SUNT at Buffalo

Re: Why does not the period change even though shear is incl

Post by emrekizilarslan » Fri May 04, 2018 9:10 am

Thank you again. I will try that.

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