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hi everyone

i used nonlinear beam elements to model a frame, i want to get the moment curvature of a column. i think there are two ways to get the moment and curvature

1 recorder the section(integration point) force and deformation of the column, i can get the moment and curvature, respectively.
2 use the zeroLengthSection (in the moment curvature example on basic examples web page) to get the moment and curvature , respectively.

i want to know is there any difference in the two method?

thank you in advance.

the difference of the periods should be very small, i think it is normal.

hi
i am using the Limit State Material , the command is:
uniaxialMaterial LimitState $matTag $s1p $e1p $s2p $e2p $s3p $e3p $s1n $e1n $s2n $e2n $s3n $e3n $pinchX $pinchY the corresponding website is following: http://opensees.berkeley.edu/wiki/index ... e_Material

i am using the Limit State Material , but i do not know how to indentify the “force & deformation” point value， in another word how to indentify the values： $s1p $e1p $s2p $e2p $s3p $e3p $s1n $e1n $s2n $e2n $s3n $e3n

if i use the Shear Limit State Material to model a column, should i do a pushover analysis to indentify the “force & deformation” point values? if i use the Axial Limit State Material to model a column, should i apply a vertical axial force to indentify the “force & deformation” point values or some other ways?


Thank you.

your materaial uniaxialMaterial Elastic 12 0. which means there is no restrains at the direction. so the matrix is singular. you can try a proper value for the rotation matrerial or you can set a very big value. Have a try and good lucn.

hi everyone

i am using the penalty method
constraints Penalty $alphaS $alphaM

could anyone tell me how to determine the reasonable values for Penalty factors $alphaS $alphaM.

my model used "equalDof command ", i used the values( $alphaS=10e14, $alphaM10e14) , but it seems give wrong answers.

thank you in advance.

hello everyone:
when i do a time history analysis, i used the modal analysis command(eigen <$type> <$solver> $numEigenvalues) to compute the omega^2 in every time step, and update the damping ratio in every step(use this command:rayleigh $alphaM $betaK $betaKinit $betaKcomm), the frequency is needed when compute the $betaK and $alphaM.
but when the PGA is large, the square of the first frequency(omega_1^2 ) will become a negative number， then the first frequency omega is a complex number(a+bi), but the second and third frequency is still a positive real number,convergence can still be reached in the time history analysis, if i want to update the damping ratio in every step. which frequency should i used, should the first frequency(a+bi) be abandoned and the second and third frequency should be used to compute the $betaK and $alphaM?????

annother question is when the first frequency omega is a complex number(a+bi), does it mean the stiffness matrix is a singular matrix or the strucure is dynamic unstable??? but in this case,the convergence can still be reached in the time history analysis.

in this command:eigen <$type> <$solver> $numEigenvalues different $type and $solver are tried ,the problem still exit.


thank you very much.

sabir wrote:
> hi all
> i'm new user of opensees. i want to calculate the plastic hing rotation or
> maximum theta in ends of beams or calumns, to calculation the rotation
> ductility. but i dont now what command i have to use?
> please explain the basicdeformation command?
> and does opensees only calculate the curvarture? can calculate the element
> rotation?

I think you can use the recorder a section's deformation to get the curvarture, and recorder the node's dis to get the element rotation.

linguan118 wrote:
> You mean the force of the zero-length element?

I mean the capacity of the Axial limit curve, the Axial limit curve will change during dynamic analysis, so the axial capacity of the Zero-Length Element will change, I want to get the axial capacity during dynamic analysis.

another question is about the limit curve, I am new to this command, would you please explain the last parameter in the limitCurve command (eleRemove 0 ),just as following.
i can not find the parameter in the opensees command manual "http://opensees.berkeley.edu/wiki/index ... LimitCurve" Thank you

# define limit surface
# tag eleTag Fsw Kdeg Fres defType forType nodeI nodeJ dof perpDir delta eleRemove
limitCurve Axial $axialCurveTag $bcTag $Fsw $axialNegSlope $Pr 2 2 1 4 1 2 0.0 0

I use a Zero-Length Element with LimitState materials in a model .
Shear LimitCurve and Axial LimitCurve are used in the model. I want to get the axial capacity of the Zero-Length Element during analysis.
which command should i used? Thanks and best wishes.

you can recorder a node's damping force
recorder Node -file DampingForce.out -time -node 2 -dof 1 rayleighForces

hi everyone:
I saw a recorder command used to recorder a beam element's rotation, what the roataion of a beam element stands for? thank you
recorder Element -file $dataDir/elerotbasic.out -time -ele 1 rotation

I read this website about LimitStateMaterial , http://opensees.berkeley.edu/wiki/index ... ynamic.tcl
but I can not understand why a soft spring is used here? Thank you.

#soft spring to take axial load after failure
uniaxialMaterial Elastic $softMatTag 99.9
element zeroLength 4 4 5 -mat $softMatTag -dir 2

####################################
# Define the zero-length end springs
####################################
#rigid material
uniaxialMaterial Elastic $rigidMatTag 9.9e9

#bottom of column slip spring
element zeroLength 1 1 2 -mat $rigidMatTag $rigidMatTag $centerSlipTag -dir 1 2 6

#top of column springs incl shear and axial
element zeroLength 3 3 4 -mat $shearTag $axialFailTag $centerSlipTag -dir 1 2 6

#soft spring to take axial load after failure
uniaxialMaterial Elastic $softMatTag 99.9
element zeroLength 4 4 5 -mat $softMatTag -dir 2

vesna wrote:
> It is the unbalanced load.
Thanks for your prompt reply vesna.

hi vesna, the folowing is model you built before could you tell me what is the reaction of node 2 ? if I recorder the reaction of node 1, i know the reaction of node 1is the support reaction,but what the reaction of node 2(a free node ) stand for? Thanks

# Canilever column from Chopra's book (Example 5.1)

wipe

model BasicBuilder -ndm 2 -ndf 3
set A1 1.0
set E [expr 10./3.]
set mass1 0.2533
set H 1.0
#set mass1 0.00001
set I1 1.0
set pi 3.14
set k [expr 3.*$I1*$E/$H**3]
puts "K: $k"
node 1 0.0 0.0
node 2 0.0 $H -mass $mass1 0.0 0.0

fix 1 1 1 1

geomTransf Linear 10
element elasticBeamColumn 1 1 2 $A1 $E $I1 10

set G 386.
timeSeries Path 2 -dt 0.005 -filePath A10000.acc -factor $G; # define acceleration vector from file (dt=0.005 is associated with the input file gm)
pattern UniformExcitation 2 1 -accel 2;


recorder Node -file point_2_ResistingForce.out -time -node 2 -dof 1 reaction


set lambda [eigen -fullGenLapack 1]
set T [expr (2*$pi)/sqrt($lambda)]
puts "T = $T"
set freq [expr sqrt($lambda)]
set dampRatio 0.05
rayleigh [expr 2.*$dampRatio*$freq] 0. 0. 0.


#integrator Newmark 0.5 [expr 1./6.]
integrator Newmark 0.5 0.25
test EnergyIncr 1.0e-6 20 1
algorithm Linear
numberer Plain
constraints Plain
system BandGeneral

analysis Transient
analyze 3995 0.01; # apply 3995 0.01-sec time steps in analysis

print -node 2

what is the reaction of node 2 ?

hi everyone:
how to considering the coupling of flexure and shear in beam element, here is what i use in a model, is it right?
i use limitState materials and ZeroLength elemen to consider coupling of flexure and shear in beam element, the shear failure will occur when the total deformation (shear deformation add the flexure deformation ) reach the shear limit dfift deformation. I think using the total deformation (shear deformation add the flexure deformation ) is just considering the coupling of flexure and shear. is it right?