dispBeamColumn element CAN NOT include shear behaviour

[tusharkantimandal]

Hi all,
I was trying to check which element type is suitable for my work: forceBeamColumn or dispbeamcolumn. In my work I need to aggregate a fiber section with a uniaxial material to incorporate the shear behaviour. what I can found that:
(1) Modal period values and nodal response values are coming different when I am using force and disp based formulation.
(2) Force based formulation CAN incorporate the shear behaviour (which is incorporated using section aggregator) properly and giving different response when I am incorporating and NOT incorporating shear behaviour.[and which should be and its almost matching with the exact solution].
(3) Displacement based formulation CAN NOT incorporate the shear behaviour (which is incorporated using section aggregator) because its giving same response when I am incorporating and NOT incorporating shear behaviour.[and which should NOT be].

From these what can I conclude?
dispBeamColumn element can not deal with the section Aggregator properly??

Note: Opensees didn't show any kind of ERROR/Warning msg. during analysis of the four different cases::
(i) forceBeamColumn excluding shear behaviour
(ii) forceBeamColumn including shear behaviour
(iii) dispBeamColumn excluding shear behaviour
(iv) dispBeamColumn including shear behaviour

Waiting for your suggestion....

##here is my small test program###

wipe;
set secTag 2;#put "2" to incorporate// put "1" NOT to incorporate the shear behaviour using section aggregator
#set eleType forceBeamColumn;
set eleType dispBeamColumn;#in each case only one will be commented out
puts "$eleType $secTag";
set P 10000;
model basic -ndm 2 -ndf 3
node 1 0.0 0.0 -mass 200 200 10;;
node 2 1.0 0.0 -mass 200 200 10;
node 3 2.0 0.0 -mass 200 200 10;
fix 1 1 1 1;
set r 0.05;
set E 210e09;
set mu 0.2;
set pi 3.141;
set G [expr $E/(2*(1+$mu))];
set A [expr $pi*$r*$r];
set GAs [expr $G*$A];
uniaxialMaterial Elastic 1 $E;
uniaxialMaterial Elastic 2 $GAs;
section Fiber 1 {
#patch circ matTag numSubdivCirc numSubdivRad yCenter zCenter intRad extRad startAng endAng
patch circ 1 20 4 0 0 0.0 $r 0 360
}
#section Aggregator $secTag $matTag1 $string1 -section $sectionTag
section Aggregator 2 2 Vy -section 1
# Create the coulumns using Beam-column elements
set transfTag 1 ;
geomTransf PDelta $transfTag;
set np 5;# Number of integration points along length of element
#element dispBeamColumn $eleTag $iNode $jNode $numIntgrPts $secTag $transfTag
element $eleType 1 1 2 $np $secTag $transfTag
element $eleType 2 2 3 $np $secTag $transfTag
set numModes 3;
#puts "numModes=" $numModes
set lambda [eigen -fullGenLapack $numModes];
# calculate frequencies and periods of the structure
#---------------------------------------------------
set omega {}
set f {}
set T {}
set pi 3.141593

foreach lam $lambda {
lappend omega [expr sqrt($lam)]
lappend f [expr sqrt($lam)/(2*$pi)]
lappend T [expr (2*$pi)/sqrt($lam)]
}
puts "periods are $T"
pattern Plain 1 Linear {
# nd FX FY MZ
load 3 0.0 $P 0.000
}
system BandGeneral
constraints Transformation
numberer RCM;
algorithm Linear;
integrator LoadControl 0.1
analysis Static
# Perform the analysis
analyze 10;
set a [nodeDisp 3 2];
puts "disp= $a";
#### END #####

[vesna]

To achieve the accurate response in nonlinear range of behavior you need to use several displacement based beam-column elements in place of one force-based beam-column element. Check this out: http://opensees.berkeley.edu/wiki/index ... ed_Element

[tusharkantimandal]

vesna wrote:
> To achieve the accurate response in nonlinear range of behavior you need to
> use several displacement based beam-column elements in place of one
> force-based beam-column element. Check this out:
> http://opensees.berkeley.edu/wiki/index ... ed_Element
Thanks vesna... This link is very interesting.. thank U so much for ur valuable suggestion...