monotonic loading analysis of RCC beam

[Prafullamalla]

i have assembled the different files available in the internet and created a RCC beam model for non linear analysis of monotonic loading. The model gives good result in linear phase but does not undergo in plastic phase.I am not being able to solve the problem. I have pasted the input file. The LibUnits.tcl file can be easily downloaded from internet.



# OpenSees Primer

#

# Units: kips, in, sec

# ------------------------------
source LibUnits.tcl
# Start of model generation

# ------------------------------

# Create ModelBuilder (with two-dimensions and 3 DOF/node)

wipe


model basic -ndm 2 -ndf 3

# Create nodes

# ------------

# Set parameters for overall model geometry

set width 43


# Create nodes

# tag X Y

node 1 0.0 0.0

node 2 $width 0.0
node 3 [expr 2*$width] 0.0
# Pin support at left end
# tag DX DY RZ

fix 1 0 1 0
# symmetrical supports at right end
fix 3 1 1 0

# MATERIAL parameters -------------------------------------------------------------------
set IDconcCore 1; # material ID tag -- confined core concrete
set IDconcCover 2; # material ID tag -- unconfined cover concrete
set IDreinf 3; # material ID tag -- reinforcement
# nominal concrete compressive strength
set fc [expr -9.0*$ksi]; # CONCRETE Compressive Strength, ksi (+Tension, -Compression)
set Ec [expr 57*$ksi*sqrt(-$fc/$psi)]; # Concrete Elastic Modulus
# confined concrete
set Kfc 1.3; # ratio of confined to unconfined concrete strength
set fc1C [expr $Kfc*$fc]; # CONFINED concrete (mander model), maximum stress
set eps1C [expr 2.*$fc1C/$Ec]; # strain at maximum stress
set fc2C [expr 0.2*$fc1C]; # ultimate stress
set eps2C [expr 5*$eps1C]; # strain at ultimate stress
# unconfined concrete
set fc1U $fc; # UNCONFINED concrete (todeschini parabolic model), maximum stress
set eps1U -0.003; # strain at maximum strength of unconfined concrete
set fc2U [expr 0.2*$fc1U]; # ultimate stress
set eps2U -0.01; # strain at ultimate stress
set lambda 0.1; # ratio between unloading slope at $eps2 and initial slope $Ec
# tensile-strength properties
set ftC [expr -0.14*$fc1C]; # tensile strength +tension
set ftU [expr -0.14*$fc1U]; # tensile strength +tension
set Ets [expr $ftU/0.002]; # tension softening stiffness
# -----------
set Fy [expr 66.8*$ksi]; # STEEL yield stress
set Es [expr 29000.*$ksi]; # modulus of steel
set Bs 0.01; # strain-hardening ratio
set R0 18; # control the transition from elastic to plastic branches
set cR1 0.925; # control the transition from elastic to plastic branches
set cR2 0.15; # control the transition from elastic to plastic branches
uniaxialMaterial Concrete02 $IDconcCore $fc1C $eps1C $fc2C $eps2C $lambda $ftC $Ets; # build core concrete (confined)
uniaxialMaterial Concrete02 $IDconcCover $fc1U $eps1U $fc2U $eps2U $lambda $ftU $Ets; # build cover concrete (unconfined)
uniaxialMaterial Steel02 $IDreinf $Fy $Es $Bs $R0 $cR1 $cR2; # build reinforcement material

# section GEOMETRY -------------------------------------------------------------
set HSec [expr 0.82*$ft]; # Column Depth
set BSec [expr 0.32*$ft]; # Column Width
set coverSec [expr 1*$in]; # Column cover to reinforcing steel NA.
set numBarsSec 6; # number of longitudinal-reinforcement bars in steel layer. (symmetric top & bot)
set barAreaSec [expr .175*$in2]; # area of longitudinal-reinforcement bars
set SecTag 1; # set tag for symmetric section

# FIBER SECTION properties -------------------------------------------------------------
# symmetric section
# y
# ^
# |
# --------------------- -- --
# | o o o | | -- cover
# | | |
# | | |
# z <--- | + | H
# | | |
# | | |
# | o o o | | -- cover
# --------------------- -- --
# |-------- B --------|
#
# y
# ^
# |
# ---------------------
# |\ cover /|
# | \------Top------/ |
# |c| |c|
# |o| |o|
# z <-----|v| core |v| Hsec
# |e| |e|
# |r| |r|
# | /-------Bot------\ |
# |/ cover \|
# ---------------------
# Bsec
#
# RC section:
set coverY [expr $HSec/2.0]; # The distance from the section z-axis to the edge of the cover concrete -- outer edge of cover concrete
set coverZ [expr $BSec/2.0]; # The distance from the section y-axis to the edge of the cover concrete -- outer edge of cover concrete
set coreY [expr $coverY-$coverSec ]; # The distance from the section z-axis to the edge of the core concrete -- edge of the core concrete/inner edge of cover concrete
set coreZ [expr $coverZ-$coverSec ]; # The distance from the section y-axis to the edge of the core concrete -- edge of the core concrete/inner edge of cover concrete
set nfCoreY 16; # number of fibers for concrete in y-direction -- core concrete
set nfCoreZ 4; # number of fibers for concrete in z-direction
set nfCoverY 16; # number of fibers for concrete in y-direction -- cover concrete
set nfCoverZ 4; # number of fibers for concrete in z-direction
section fiberSec 1 {; # Define the fiber section
# Define the core patch
patch quadr $IDconcCore $nfCoreZ $nfCoreY -$coreY $coreZ -$coreY -$coreZ $coreY -$coreZ $coreY $coreZ

# Define the four cover patches
patch quadr $IDconcCover 1 $nfCoverY -$coverY $coverZ -$coreY $coreZ $coreY $coreZ $coverY $coverZ
patch quadr $IDconcCover 1 $nfCoverY -$coreY -$coreZ -$coverY -$coverZ $coverY -$coverZ $coreY -$coreZ
patch quadr $IDconcCover $nfCoverZ 1 -$coverY $coverZ -$coverY -$coverZ -$coreY -$coreZ -$coreY $coreZ
patch quadr $IDconcCover $nfCoverZ 1 $coreY $coreZ $coreY -$coreZ $coverY -$coverZ $coverY $coverZ

# Define reinfocement layers
layer straight $IDreinf $numBarsSec $barAreaSec $coreY $coreZ $coreY -$coreZ; # top layer reinforcement
layer straight $IDreinf $numBarsSec $barAreaSec -$coreY $coreZ -$coreY -$coreZ; # bottom layer reinfocement
}; # end of fibersection definition



# Define column elements

# ----------------------

# Geometry of column elements

# tag

geomTransf Linear 1

# Number of integration points along length of element

set np 5

# Create the coulumns using Beam-column elements

# tag ndI ndJ nsecs secID transfTag

element nonlinearBeamColumn 1 1 2 $np 1 1
element nonlinearBeamColumn 2 2 3 $np 1 1

# Define point load at the mid portion of beam

# --------------------

# Set a parameter for the verticsl load

set P 15; # 15 kips vertical load

# Create a Plain load pattern with a Linear TimeSeries

pattern Plain 1 "Linear" {

# Create nodal load at node 2

# nd FX FY MZ

load 2 0.0 [expr -$P] 0.0


}

# ------------------------------

# End of model generation

# ------------------------------

# ------------------------------

# Start of analysis generation

# ------------------------------

# Create the system of equation, a sparse solver with partial pivoting

system BandGeneral

# Create the constraint handler, the transformation method

constraints Transformation

# Create the DOF numberer, the reverse Cuthill-McKee algorithm

numberer RCM

# Create the convergence test, the norm of the residual with a tolerance of

# 1e-12 and a max number of iterations of 10

test NormDispIncr 1.0e-12 50 3

# Create the solution algorithm, a Newton-Raphson algorithm

algorithm Newton

# Create the integration scheme, the LoadControl scheme using steps of 0.1

integrator LoadControl 0.1

# Create the analysis object

analysis Static

# initialize in case we need to do an initial stiffness iteration

initialize

# ------------------------------

# End of analysis generation

# ------------------------------

# ------------------------------

# Start of recorder generation

# ------------------------------

# Create a recorder to monitor nodal displacements

recorder Node -file nodeGravity.out -time -node 2 -dof 2 disp
recorder Node -file nodereaction.out -time -node 1 3 -dof 2 reaction
# --------------------------------

# End of recorder generation

# ---------------------------------

# ------------------------------

# Finally perform the analysis

# ------------------------------

# perform the point load analysis, requires 10 steps to reach the load level

analyze 10

# Print out the state of nodes 1 2

print node 2

# Print out the state of element 1

print ele 1 2

[Prafullamalla]

if I change the concrete material to Concrete01, it gives plastic phase.but , it cant with concrete02 considering the tension.I could not understand the reason.

[Prafullamalla]

concrete02 material didnt work because of some problem in opensees.exe.i download new opeseestk.exe and then it worked

[bandwidth0zero]

Same issue (2-stories frame) with Concrete02, works fine with 01. Any suggestion?

[fmk]

nonlinear analysis does not always converge .. replace the line
analyze 10
with a number of lines to try different options if the analysis fails