is it a bug????

salman · Post by **salman** » Sat Nov 28, 2009 7:46 am

Dear Dr. Mazzoni:

i`m trying to assign a section(fiber section or section Aggregator or ......)to shellMITC4 Element but i can`t.
just ElasticMembranePlateSection can be assign to the shell element.
i built a section in section aggregator with elastic material for string T and ElasticMembranePlateSection ,,but analysis failed.just when i use ElasticMembranePlateSection analyze will be done
do you know why?

salman · Post by **salman** » Sat Nov 28, 2009 9:59 am

this is my file:

wipe;
model BasicBuilder -ndm 3 -ndf 6

node 1 0 0 0
node 2 0 5 0
node 3 0 0 3
node 4 0 5 3

fix 1 1 1 1 1 1 1
fix 2 1 1 1 1 1 1

set fy 450000.0 ;
set E 200000000.0 ;
#uniaxialMaterial Steel01 2 $fy $E 0.02
;
uniaxialMaterial Elastic 3 1.0e12;
uniaxialMaterial Elastic 99 1.0e12;

section Aggregator 5 3 P 3 Mz 99 T;

element ShellMITC4 20 2 1 3 4 5

pattern Plain 1 Linear {
load 4 0 0 -100 0 0 0

}
system BandGeneral
constraints Plain
numberer Plain
test NormDispIncr 1.0e-3 2000 0
Algorithm Newton
integrator LoadControl 0.1
analysis Static
analyze 10

silvia · Post by **silvia** » Sat Nov 28, 2009 10:06 pm

i don't know enough about that element.

silvia · Post by **silvia** » Sat Nov 28, 2009 10:08 pm

do you have the proper number of dofs?

salman · Post by **salman** » Sun Nov 29, 2009 1:38 am

from opensees examples manual(original examples primer-exaple 7)
i saw dom-3 & dof-6.and i used it.i performed an analysis on 2d model with shellmitc4 element and an error occured.but with this element and elesticmembraneplatesection section in 3d space and 6 dofs performing the analyze was succesful.but in the same condition when i used another sections,analysis was failed.i think its related to shell element and it is a bug but i`m not sure.it,s so vital for me because i must model frames with 3 to 20 storys with shear wall to complete my thesis.
1-do you have any idea for accurate modeling of shear walls?
2- would you please tell me who the author of shell element is?

best regards
salman

silvia · Post by **silvia** » Sun Nov 29, 2009 10:38 am

2D elements should have 2dofs in 2D problem and 3dofs in 3D problem, i believe.

salman · Post by **salman** » Mon Nov 30, 2009 2:28 am

many thanks for your advice
but i think if i use 2or3 dof`s in 2D or 3D analysis,we have just translational dof`s and i havt to ommit the fexural deformation in frames.am i right?

silvia · Post by **silvia** » Mon Nov 30, 2009 7:19 am

try it