Question

[juanoviedo]

Hello everybody.

I am working on a 2-D reinforced concrete frame model and it seems I am having problems with understanding the local axis of the beams and columns.
The global horizontal axis is X and the vertical is Y. Columns are oriented withing the Y axis and beams within X axis.
As the analysis is non-linear, I am using the "Section Uniaxial" for beams and "Section Aggregator" for columns. At the beginning, from the manual, I understood that for both columns and beams the moment-curvature relationship to be input in the "section" command would be "Mz".
I ran my model but the deformations are so high, then I tried modifying the beams for "My" and it seems like working properly.However, this later modification is still not so clear for me.
Then, my question is... in 2-D problems, when the vectors are not needed to be defined, how is the local axis rule? This matter is a little bit confussing from the manual.
As summary... for beams, in the section uniaxial===> "My" or "Mz" ?
for column==================> "Mz" ?

Thanks for any comment.
Regards,

[sjerez]

Hello Juan and everybody :

I’m a beginner in Opensees and I have also the same question about local axes, however, from the local forces of some 2D examples that I’ve performed before I’ve seen that local axes in beams and columns seem follow this rule:
x-local axis lies in the axial direction, from the node I to node J
z-local axis is normal to the plane frame, so is the same as z-global axis and
y-local axis is defined by the right hand rule, so for beams local and global coordinate systems are the same and for columns y –local axis is horizontal and goes in the negative direction of global x-axis.

This means that in both cases (beams and columns), z –local axis is the bending axis as is stated in the manual for the fiber command. So if we need to define a moment-curvature relationship, we should use Mz for beams and columns. It would mean that your first analysis was good (concerning the direction of M-curvature relationship) despite the large deformations and maybe you need to check the other parameters to find the error.

Well, I hope this is useful for you and I would like to know if I am right concerning the local axis? May anyone confirm?

Regards,

Sandra Jerez
Paris-Est University
Paris-France

[juanoviedo]

Hello Sandra!!
Thanks for your comments.
I understand perfectly what you say. In fact, that is what I understood from the manual and some examples. However, the deformations I am getting are wrong and when I change the beams for "My", the output,deformation, etc are ok... so I am confussed!!!.

I hope Dr. Silvia could give us some light on this matter.

Thanks again for your comment.
Regards,
Ps\ Silva, would you mind helping me revise my input data?

[silvia]

how many dimensions have youspecified?
how many dof's per node do you have specified?

[juanoviedo]

Hello Dr.Silvia
Thanks for you reply.

I specified 2 dimensions and 3 DOFs per node as illustrated in the manual and some examples.

What is happening then?

Best Regards,

[silvia]

please post only the important parts of your script.

[juanoviedo]

Hello Dr. Silvia!

Herewith I am posting some parts of my script. I believe this part is the most relevant for the identification of the problem.
If is not clear enough, please let me know.

The model runs but with large deformations, and when I change in "section" for "My" in the beams, the model runs much more better, but is kind of strange, isn't it?

Thanks for your time.
Best Regards,





# *************************************************************
# ****************** SET UP ***********************************
puts "Definition of Set Up variables"
wipe; #clear opensees model
model basic -ndm 2 -ndf 3; #2 dimensions, 3 DOFs per node
set Tol 1.0e-5; #tolerance for convergence
set Iter 100; #maximum number of interations
# setting up external script sources
source DisplayPlane.tcl; #procedure for displaying a plane in model
source DisplayModel2D.tcl; #procedure for displaying 2D perspective of model
source Getperiod.tcl; #procedure for getting the natural periods
source Getrayleigh.tcl; #procedure to calculate Rayleigh damp
puts "****Set up variables defined"
puts ""
#

*************************************************************
# ************** DEFINE GEOMETRY *****************************
puts "Definition of Model Geometry"
# ****NODAL COORDINATES:
# NodeId X Y
node 1 0. 0.; #first floor
node 2 700. 0.
node 3 1400. 0.
node 4 2100. 0.
node 5 0. 350.; #second floor
node 6 700. 350.
node 7 1400. 350.
node 8 2100. 350.
node 9 0. 700.; #third floor
node 10 700. 700.
node 11 1400. 700.
node 12 2100. 700.
node 13 0. 1050.; #forth floor
node 14 700. 1050.
node 15 1400. 1050.
node 16 2100. 1050.
node 17 0. 1400.; #fifth floor
node 18 700. 1400.
node 19 1400. 1400.
node 20 2100. 1400.
node 21 0. 1750.; #sixth floor
node 22 700. 1750.
node 23 1400. 1750.
node 24 2100. 1750.
node 25 0. 2100.; #seventh floor
node 26 700. 2100.
node 27 1400. 2100.
node 28 2100. 2100.
node 29 0. 2450.; #eighth floor
node 30 700. 2450.
node 31 1400. 2450.
node 32 2100. 2450.
node 33 0. 2800.; #ninth floor
node 34 700. 2800.
node 35 1400. 2800.
node 36 2100. 2800.
node 37 0. 3150.; #tenth floor
node 38 700. 3150.
node 39 1400. 3150.
node 40 2100. 3150.
node 41 0. 3500.; #roof
node 42 700. 3500.
node 43 1400. 3500.
node 44 2100. 3500.
node 45 1050. 350.; #second floor for BRB
node 46 1050. 700.; #third floor for BRB
node 47 1050. 1050.; #forth floor for BRB
node 48 1050. 1400.; #fifth floor for BRB
node 49 1050. 1750.; #sixth floor for BRB
node 50 1050. 2100.; #seventh floor for BRB
node 51 1050. 2450.; #eighth floor for BRB
node 52 1050. 2800.; #ninth floor for BRB
node 53 1050. 3150.; #tenth floor for BRB
node 54 1050. 3500.; #roof floor for BRB
puts "****Nodes Defined"

# ****SINGLE POINT CONSTRAINTS - BOUNDARY CONDITIONS:
# NodeId DZ DY RZ
fix 1 1 1 1; #supports are fixed (fixed=1, free=0)
fix 2 1 1 1
fix 3 1 1 1
fix 4 1 1 1
#
# ****MULTI-POINT CONSTRAINTS - EQUAL DOFs:
# Master Slave Dofs
equalDOF 5 6 1; #node 6 has same horizontal displacement(DOF) as node 5;#(Dx=1,Dy=2,Rz=3)
equalDOF 5 7 1
equalDOF 5 8 1
equalDOF 5 45 1
equalDOF 9 10 1; #third floor
equalDOF 9 11 1
equalDOF 9 12 1
equalDOF 9 46 1
equalDOF 13 14 1; #forth floor
equalDOF 13 15 1
equalDOF 13 16 1
equalDOF 13 47 1
equalDOF 17 18 1; #fifth floor
equalDOF 17 19 1
equalDOF 17 20 1
equalDOF 17 48 1
equalDOF 21 22 1; #sixth floor
equalDOF 21 23 1
equalDOF 21 24 1
equalDOF 21 49 1
equalDOF 25 26 1; #seventh floor
equalDOF 25 27 1
equalDOF 25 28 1
equalDOF 25 50 1
equalDOF 29 30 1; #eighth floor
equalDOF 29 31 1
equalDOF 29 32 1
equalDOF 29 51 1
equalDOF 33 34 1; #ninth floor
equalDOF 33 35 1
equalDOF 33 36 1
equalDOF 33 52 1
equalDOF 37 38 1; #tenth floor
equalDOF 37 39 1
equalDOF 37 40 1
equalDOF 37 53 1
equalDOF 41 42 1; #roof
equalDOF 41 43 1
equalDOF 41 44 1
equalDOF 41 54 1
puts "****Restrains Defined"
puts ""


# ****NODAL MASSES:
puts "Definition of Masses"
# NodeId Mx My Mz
for {set y 1} {$y <=10 } {incr y 1} {;#add mass at each floor of Massx/6
mass [expr $y*4+1] [expr $Massx/6] 1e-10 1e-10
}
for {set y 1} {$y <=10 } {incr y 1} {;#add mass at each floor of Massx(2/6)
mass [expr $y*4+2] [expr $Massx/3] 1e-10 1e-10
}
for {set y 1} {$y <=10 } {incr y 1} {;#add mass at each floor of Massx(2/6)
mass [expr $y*4+3] [expr $Massx/3] 1e-10 1e-10
}
for {set y 1} {$y <=10 } {incr y 1} {;#add mass at each floor of Massx/6
mass [expr $y*4+4] [expr $Massx/6] 1e-10 1e-10
}
#for {set y 1} {$y <=10 } {incr y 1} {print -node [expr $y*4+1]}; #check the input mass
puts "****Masses Defined"
puts ""

puts "Definition of Material Behavior"
#UniaxialMaterial Elastic-Perfectly Plastic for beams (50% reduction)
# HingeId EI esyP esyN
uniaxialMaterial ElasticPP 1 [expr 1.12E7/5.06E-5] 5.06E-5 -7.06E-5
uniaxialMaterial ElasticPP 2 [expr 1.05E7/4.77E-5] 4.77E-5 -6.71E-5
uniaxialMaterial ElasticPP 3 [expr 1.26E7/5.73E-5] 5.73E-5 -7.83E-5
uniaxialMaterial ElasticPP 4 [expr 1.26E7/5.73E-5] 5.73E-5 -7.83E-5
uniaxialMaterial ElasticPP 5 [expr 1.26E7/5.73E-5] 5.73E-5 -7.83E-5
uniaxialMaterial ElasticPP 6 [expr 1.26E7/5.71E-5] 5.71E-5 -7.59E-5
uniaxialMaterial ElasticPP 7 [expr 1.12E7/5.07E-5] 5.07E-5 -7.34E-5
uniaxialMaterial ElasticPP 8 [expr 1.16E7/5.25E-5] 5.25E-5 -7.39E-5
uniaxialMaterial ElasticPP 9 [expr 9.98E6/4.52E-5] 4.52E-5 -7.03E-5
uniaxialMaterial ElasticPP 10 [expr 1.05E7/4.77E-5] 4.77E-5 -6.49E-5
uniaxialMaterial ElasticPP 11 [expr 7.82E6/4.36E-5] 4.36E-5 -7.03E-5
uniaxialMaterial ElasticPP 12 [expr 9.08E6/5.06E-5] 5.06E-5 -7.08E-5
uniaxialMaterial ElasticPP 13 [expr 6.00E6/3.35E-5] 3.35E-5 -6.35E-5
uniaxialMaterial ElasticPP 14 [expr 6.98E6/3.89E-5] 3.89E-5 -6.37E-5
uniaxialMaterial ElasticPP 15 [expr 4.44E6/2.48E-5] 2.48E-5 -5.33E-5
uniaxialMaterial ElasticPP 16 [expr 5.48E6/3.05E-5] 3.05E-5 -5.35E-5
uniaxialMaterial ElasticPP 17 [expr 2.98E6/1.66E-5] 1.66E-5 -4.29E-5
uniaxialMaterial ElasticPP 18 [expr 3.72E6/2.07E-5] 2.07E-5 -4.29E-5
uniaxialMaterial ElasticPP 19 [expr 2.98E6/1.66E-5] 1.66E-5 -2.85E-5
uniaxialMaterial ElasticPP 20 [expr 2.98E6/1.66E-5] 1.66E-5 -2.85E-5
uniaxialMaterial ElasticPP 21 [expr 10.E10/1.] 1. -1. ;#dummy for the intermediate node
#UniaxialMaterial Elastic-Perfectly Plastic for columns per floor(70% reduction)
set EI1 [expr $ME350*$Icol]
set EI2 [expr $ME280*$Icol]
set curv1 [expr 218.1E5/$EI1]
set curv2 [expr 134.3E5/$EI1]
set curv3 [expr 102.0E5/$EI2]
set curv4 [expr 90.7E5/$EI2]
#uniaxialMaterial ElasticPP 22 $EI1 $curv1 -$curv1
#uniaxialMaterial ElasticPP 23 $EI1 $curv2 -$curv2
#uniaxialMaterial ElasticPP 24 $EI2 $curv3 -$curv3
#uniaxialMaterial ElasticPP 25 $EI2 $curv4 -$curv4
#uniaxialMaterial ElasticPP 26 $EI2 $curv4 -$curv4
#uniaxialMaterial ElasticPP 27 $EI2 $curv4 -$curv4
#uniaxialMaterial ElasticPP 28 $EI2 $curv4 -$curv4
#uniaxialMaterial ElasticPP 29 $EI2 $curv4 -$curv4
#uniaxialMaterial ElasticPP 30 $EI2 $curv4 -$curv4
#uniaxialMaterial ElasticPP 31 $EI2 $curv4 -$curv4
set AE1 [expr $ME350*$Acol]
set AE2 [expr $ME280*$Acol]
uniaxialMaterial Elastic 22 $EI1
uniaxialMaterial Elastic 23 $EI1
uniaxialMaterial Elastic 24 $EI2
uniaxialMaterial Elastic 25 $EI2
uniaxialMaterial Elastic 26 $EI2
uniaxialMaterial Elastic 27 $EI2
uniaxialMaterial Elastic 28 $EI2
uniaxialMaterial Elastic 29 $EI2
uniaxialMaterial Elastic 30 $EI2
uniaxialMaterial Elastic 31 $EI2

uniaxialMaterial Elastic 32 $AE1
uniaxialMaterial Elastic 33 $AE1
uniaxialMaterial Elastic 34 $AE2
uniaxialMaterial Elastic 35 $AE2
uniaxialMaterial Elastic 36 $AE2
uniaxialMaterial Elastic 37 $AE2
uniaxialMaterial Elastic 38 $AE2
uniaxialMaterial Elastic 39 $AE2
uniaxialMaterial Elastic 40 $AE2
uniaxialMaterial Elastic 41 $AE2

puts "****UniaxialMaterial Elastic-Perfectly Plastic Defined"
puts ""
puts "Definition of Sections"
# for beams. Section for Uniaxial material. Moment-curvature about local axis (PHId MatId Type)
for {set y 1} {$y <=21} {incr y 1} {
section Uniaxial $y $y Mz
}
# for columns.
for {set y 22} {$y <=31} {incr y 1} {
section Aggregator $y [expr $y+10] P $y Mz
}

puts "****Sections Defined"
puts ""

puts "Definition of Elements"
# ****GEOMETRIC TRANSFORMATION:
# for beams
geomTransf Linear 1 -jntOffset $Xi1 $Yi1 -$Xj1 -$Yj1; #from basic system to the global-coordinate system
geomTransf Linear 2 -jntOffset $Xi2 $Yi2 -$Xj2 -$Yj2; #rigid offset No.2
geomTransf Linear 3 -jntOffset $Xi3 $Yi3 -$Xj3 -$Yj3; #rigid offset No.3
# for columns; #P-D effect is considered only for columns
geomTransf PDelta 4 -jntOffset $Xi4 $Yi4 -$Xj4 -$Yj4; #rigid offest No.4
geomTransf PDelta 5 -jntOffset $Xi5 $Yi5 -$Xj5 -$Yj5; #rigid offest No.5
geomTransf PDelta 6 -jntOffset $Xi6 $Yi6 -$Xj6 -$Yj6; #rigid offest No.6
puts "****Transformation Defined"
puts ""
#
set IntPt 2; #2=Linear curvature distribution
# Nonlinear Beam Column Element
# eleId iNode jNode Integr SecTag TransfTag
element nonlinearBeamColumn 1 1 5 $IntPt 22 4
element nonlinearBeamColumn 2 2 6 $IntPt 22 4
element nonlinearBeamColumn 3 3 7 $IntPt 22 4
element nonlinearBeamColumn 4 4 8 $IntPt 22 4
# columns second floor
element nonlinearBeamColumn 5 5 9 $IntPt 23 5
element nonlinearBeamColumn 6 6 10 $IntPt 23 5
element nonlinearBeamColumn 7 7 11 $IntPt 23 5
element nonlinearBeamColumn 8 8 12 $IntPt 23 5
# columns third floor
element nonlinearBeamColumn 9 9 13 $IntPt 24 5
element nonlinearBeamColumn 10 10 14 $IntPt 24 5
element nonlinearBeamColumn 11 11 15 $IntPt 24 5
element nonlinearBeamColumn 12 12 16 $IntPt 24 5
# columns forth floor
element nonlinearBeamColumn 13 13 17 $IntPt 25 5
element nonlinearBeamColumn 14 14 18 $IntPt 25 5
element nonlinearBeamColumn 15 15 19 $IntPt 25 5
element nonlinearBeamColumn 16 16 20 $IntPt 25 5
# columns fifth floor
element nonlinearBeamColumn 17 17 21 $IntPt 26 5
element nonlinearBeamColumn 18 18 22 $IntPt 26 5
element nonlinearBeamColumn 19 19 23 $IntPt 26 5
element nonlinearBeamColumn 20 20 24 $IntPt 26 5
# columns sixth floor
element nonlinearBeamColumn 21 21 25 $IntPt 27 6
element nonlinearBeamColumn 22 22 26 $IntPt 27 6
element nonlinearBeamColumn 23 23 27 $IntPt 27 6
element nonlinearBeamColumn 24 24 28 $IntPt 27 6
# columns seventh floor
element nonlinearBeamColumn 25 25 29 $IntPt 28 6
element nonlinearBeamColumn 26 26 30 $IntPt 28 6
element nonlinearBeamColumn 27 27 31 $IntPt 28 6
element nonlinearBeamColumn 28 28 32 $IntPt 28 6
# columns eighth floor
element nonlinearBeamColumn 29 29 33 $IntPt 29 6
element nonlinearBeamColumn 30 30 34 $IntPt 29 6
element nonlinearBeamColumn 31 31 35 $IntPt 29 6
element nonlinearBeamColumn 32 32 36 $IntPt 29 6
# columns ninth floor
element nonlinearBeamColumn 33 33 37 $IntPt 30 6
element nonlinearBeamColumn 34 34 38 $IntPt 30 6
element nonlinearBeamColumn 35 35 39 $IntPt 30 6
element nonlinearBeamColumn 36 36 40 $IntPt 30 6
# columns tenth floor
element nonlinearBeamColumn 37 37 41 $IntPt 31 6
element nonlinearBeamColumn 38 38 42 $IntPt 31 6
element nonlinearBeamColumn 39 39 43 $IntPt 31 6
element nonlinearBeamColumn 40 40 44 $IntPt 31 6
# Beam with Hinge Elements => for Beams
# eleId iNode jNode LpiId Lpi LpjId Lpj M.Elas Area M.InertiaZ transfTag
# beams second floor
element beamWithHinges 41 5 6 1 $Lp1 2 $Lp3 $ME280 $Abm1 $Ibm1 1
element beamWithHinges 42 6 45 2 $Lp1 21 $Lp4 $ME280 $Abm1 $Ibm1 2
element beamWithHinges 43 45 7 21 $Lp2 2 $Lp3 $ME280 $Abm1 $Ibm1 3
element beamWithHinges 44 7 8 2 $Lp1 1 $Lp3 $ME280 $Abm1 $Ibm1 1
# beams third floor
element beamWithHinges 45 9 10 3 $Lp1 4 $Lp3 $ME280 $Abm1 $Ibm1 1
element beamWithHinges 46 10 46 4 $Lp1 21 $Lp4 $ME280 $Abm1 $Ibm1 2
element beamWithHinges 47 46 11 21 $Lp2 4 $Lp3 $ME280 $Abm1 $Ibm1 3
element beamWithHinges 48 11 12 4 $Lp1 3 $Lp3 $ME280 $Abm1 $Ibm1 1
# beams forth floor
element beamWithHinges 49 13 14 5 $Lp1 6 $Lp3 $ME280 $Abm1 $Ibm1 1
element beamWithHinges 50 14 47 6 $Lp1 21 $Lp4 $ME280 $Abm1 $Ibm1 2
element beamWithHinges 51 47 15 21 $Lp2 6 $Lp3 $ME280 $Abm1 $Ibm1 3
element beamWithHinges 52 15 16 6 $Lp1 5 $Lp3 $ME280 $Abm1 $Ibm1 1
# beams fifth floor
element beamWithHinges 53 17 18 7 $Lp1 8 $Lp3 $ME280 $Abm1 $Ibm1 1
element beamWithHinges 54 18 48 8 $Lp1 21 $Lp4 $ME280 $Abm1 $Ibm1 2
element beamWithHinges 55 48 19 21 $Lp2 8 $Lp3 $ME280 $Abm1 $Ibm1 3
element beamWithHinges 56 19 20 8 $Lp1 7 $Lp3 $ME280 $Abm1 $Ibm1 1
# beams sixth floor
element beamWithHinges 57 21 22 9 $Lp1 10 $Lp3 $ME280 $Abm1 $Ibm1 1
element beamWithHinges 58 22 49 10 $Lp1 21 $Lp4 $ME280 $Abm1 $Ibm1 2
element beamWithHinges 59 49 23 21 $Lp2 10 $Lp3 $ME280 $Abm1 $Ibm1 3
element beamWithHinges 60 23 24 10 $Lp1 9 $Lp3 $ME280 $Abm1 $Ibm1 1
# beams seventh floor
element beamWithHinges 61 25 26 11 $Lp1 12 $Lp3 $ME280 $Abm2 $Ibm2 1
element beamWithHinges 62 26 50 12 $Lp1 21 $Lp4 $ME280 $Abm2 $Ibm2 2
element beamWithHinges 63 50 27 21 $Lp2 12 $Lp3 $ME280 $Abm2 $Ibm2 3
element beamWithHinges 64 27 28 12 $Lp1 11 $Lp3 $ME280 $Abm2 $Ibm2 1
# beams eighth floor
element beamWithHinges 65 29 30 13 $Lp1 14 $Lp3 $ME280 $Abm2 $Ibm2 1
element beamWithHinges 66 30 51 14 $Lp1 21 $Lp4 $ME280 $Abm2 $Ibm2 2
element beamWithHinges 67 51 31 21 $Lp2 14 $Lp3 $ME280 $Abm2 $Ibm2 3
element beamWithHinges 68 31 32 14 $Lp1 13 $Lp3 $ME280 $Abm2 $Ibm2 1
# beams ninth floor
element beamWithHinges 69 33 34 15 $Lp1 16 $Lp3 $ME280 $Abm2 $Ibm2 1
element beamWithHinges 70 34 52 16 $Lp1 21 $Lp4 $ME280 $Abm2 $Ibm2 2
element beamWithHinges 71 52 35 21 $Lp2 16 $Lp3 $ME280 $Abm2 $Ibm2 3
element beamWithHinges 72 35 36 16 $Lp1 15 $Lp3 $ME280 $Abm2 $Ibm2 1
# beams tenth floor
element beamWithHinges 73 37 38 17 $Lp1 18 $Lp3 $ME280 $Abm2 $Ibm2 1
element beamWithHinges 74 38 53 18 $Lp1 21 $Lp4 $ME280 $Abm2 $Ibm2 2
element beamWithHinges 75 53 39 21 $Lp2 18 $Lp3 $ME280 $Abm2 $Ibm2 3
element beamWithHinges 76 39 40 18 $Lp1 17 $Lp3 $ME280 $Abm2 $Ibm2 1
# beams roof floor
element beamWithHinges 77 41 42 19 $Lp1 20 $Lp3 $ME280 $Abm2 $Ibm2 1
element beamWithHinges 78 42 54 20 $Lp1 21 $Lp4 $ME280 $Abm2 $Ibm2 2
element beamWithHinges 79 54 43 21 $Lp2 20 $Lp3 $ME280 $Abm2 $Ibm2 3
element beamWithHinges 80 43 44 20 $Lp1 19 $Lp3 $ME280 $Abm2 $Ibm2 1
puts "****Elements Defined"
puts ""

[silvia]

so, you replace Mz with My in the beams?
using the same values????

[juanoviedo]

Hello Dr.Silvia!

Yes! that is what I did!

After having high deformations, I just start trying some changes in order to trace the error and when I changed only "Mz" for "My" in the beams, the response was much more better. However, it is not so clear for me the reason.

Waiting for your comment,
Regards,

[silvia]

i am still waiting for confirmation from Frank, but, in 2D, yes, you do use My, it seems.

[juanoviedo]

Hello Dr.Silvia!
Thanks for the reply!
Yes, it seems like working correctly when I use "My" instead of "Mz".
Anyway, I will be waiting for your confirmation once you have talked to Frank.

Best Regards,
Juan

[juanoviedo]

Ok Dr.Silvia, thanks for your help.
I will run the models by usign "My" if something appears then I will contact you again.
Anyway, may I know the reason Frank told you?

Best regards,
Juan

[silvia]

I have spoken to Frank about this.
You actually need to specify Mz. if you specify My, but not Mz, the program assigns zero flexibility to Mz, hence infinite stiffness -- that's why you are getting seemingly-good results. However, you need to specify Mz and check your model flexibility, as it may be too high.

[juanoviedo]

Hello Dr.Silvia!

I rechecked the model and the flexibility of my model as you suggested to me in your last reply; however the results are still strange.

About the flexibility: Before going in the nonlinear analysis, I started running a static analysis in order to get familiar with the OpenSees features and commands. The results I got were ok regarding values of period, and displacements. In fact, I compared the results with the output given by Drain-2DX and they were much close.

Then what I did next was to change the element type into nonlinearBeamColumn for columns and beamWithHinges for beam elements and include the additional commands needed for these types of elements. Then I started to run again and was when I got the strange values.

I, personally, do not think my model has a flexibility problem as the values of period are ok and besides this, I also compared the results given by OpenSees when I used “My” instead of “Mz” for beams with the output given by Drain-2DX and they were also much close (for dynamic nonlinear analysis).

I have been trying to solve the problem but unfortunately I have not succeeded yet.
I will be waiting for your next comment.

Best Regards,

Juan
PS/ did you happen to have time to take a look at my input data I sent to you?

[juanoviedo]

Hello Dr.Silvia!

I rechecked the model and the flexibility of my model as you suggested to me in your last reply; however the results are still strange.

About the flexibility: Before going in the nonlinear analysis, I started running a static analysis in order to get familiar with the OpenSees features and commands. The results I got were ok regarding values of period, and displacements. In fact, I compared the results with the output given by Drain-2DX and they were much close.

Then what I did next was to change the element type into nonlinearBeamColumn for columns and beamWithHinges for beam elements and include the additional commands needed for these types of elements. Then I started to run again and was when I got the strange values.

I, personally, do not think my model has a flexibility problem as the values of period are ok and besides this, I also compared the results given by OpenSees when I used “My” instead of “Mz” for beams with the output given by Drain-2DX and they were also much close (for dynamic nonlinear analysis).

I have been trying to solve the problem but unfortunately I have not succeeded yet.

I will be waiting for your next comment which I am needing so much.
With all due respect,

Best Regards,

Juan
PS/ did you happen to have time to take a look at my input data I sent to you?