I´m having some problems with my simply supported beam. Setup is basic see below. I´m monitoring deflections at node 2. When I apply these boundary conditions I
get deflections that are too small (very small) however when I remove the roller and node 3 is free then I start getting "correct-ish" displacements for the applied load at the middle node?
Does anyone know why this is? plz help
The input file is below:
# --------------------------------------------------------------------------------------------------
# fiber section, nonlinearBeamColumn element
#
#
# ^Y
# | set-up
# |
#
# 1------2------3 -->x
# XX 00
# LCol
#
#
# SET UP ----------------------------------------------------------------------------
wipe; # clear memory of all past model definitions
file mkdir Data1; # create data directory
model BasicBuilder -ndm 2 -ndf 3; # Define the model builder, ndm=#dimension, ndf=#dofs
source units_si.tcl
puts "units built"
# define GEOMETRY -------------------------------------------------------------
set LCol [expr 4100*$mm]; # column length
set MCol [expr $LCol/2];
# define section geometry
set HCol [expr 552*$mm]; # Column Depth
set BCol [expr 305*$mm]; # Column Width
# calculated geometry parameters
#set ACol [expr $BCol*$HCol]; # cross-sectional area
#set IzCol [expr 1./12.*$BCol*pow($HCol,3)]; # Column moment of inertia
# nodal coordinates:
node 1 0 0; # node#, X, Y
node 2 $MCol 0;
node 3 $LCol 0;
# Single point constraints -- Boundary Conditions
fix 1 1 1 1; # node DX DY RZ
fix 3 0 1 1;
# Define ELEMENTS & SECTIONS -------------------------------------------------------------
set ColSecTag 1; # assign a tag number to the column section
# define section geometry
set coverCol [expr 64*$mm]; # Column cover to reinforcing steel NA.
set numBarsCol 4; # number of longitudinal-reinforcement bars in each side of column section. (symmetric top & bot)
set barAreaCol [expr 700*$mm]; # area of longitudinal-reinforcement bars
# MATERIAL parameters -------------------------------------------------------------------
set IDconcU 1; # material ID tag -- unconfined cover concrete
set IDreinf 2; # material ID tag -- reinforcement
# nominal concrete compressive strength
set fc [expr -22.6*$MPa]; # CONCRETE Compressive Strength (+Tension, -Compression)
set Ec [expr 36500*$MPa]; # Concrete Elastic Modulus (the term in sqr root needs to be in psi
# 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 $Ec
# tensile-strength properties
set ftU [expr -0.14*$fc1U]; # tensile strength +tension
set Ets [expr $ftU/0.002]; # tension softening stiffness
# -----------
set Fy [expr 436*$MPa]; # STEEL yield stress
set Es [expr 200000*$MPa]; # 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 $IDconcU $fc1U $eps1U $fc2U $eps2U $lambda $ftU $Ets; # build cover concrete (unconfined)
uniaxialMaterial Steel02 $IDreinf $Fy $Es $Bs $R0 $cR1 $cR2; # build reinforcement material
# FIBER SECTION properties -------------------------------------------------------------
# symmetric section
# y
# ^
# |
# --------------------- -- --
# | o o o | | -- cover
# | | |
# | | |
# z <--- | + | H
# | | |
# | | |
# | o o o | | -- cover
# --------------------- -- --
# |-------- B --------|
#
# RC section:
set coverY [expr $HCol/2.0]; # The distance from the section z-axis to the edge of the cover concrete -- outer edge of cover concrete
set coverZ [expr $BCol/2.0]; # The distance from the section y-axis to the edge of the cover concrete -- outer edge of cover concrete
set coreY [expr $coverY-$coverCol]
set coreZ [expr $coverZ-$coverCol]
set nfY 10; # number of fibers for concrete in y-direction
set nfZ 10; # number of fibers for concrete in z-direction
section fiberSec $ColSecTag {; # Define the fiber section
patch quadr $IDconcU $nfZ $nfY -$coverY $coverZ -$coverY -$coverZ $coverY -$coverZ $coverY $coverZ; # Define the concrete patch
layer straight $IDreinf $numBarsCol $barAreaCol -$coreY $coreZ -$coreY -$coreZ; # top layer reinfocement
layer straight $IDreinf $numBarsCol $barAreaCol $coreY $coreZ $coreY -$coreZ; # bottom layer reinforcement
}; # end of fibersection definition
# define geometric transformation: performs a linear geometric transformation of beam stiffness and resisting force from the basic system to the global-coordinate system
set ColTransfTag 1; # associate a tag to column transformation
geomTransf Linear $ColTransfTag ;
# element connectivity:
set numIntgrPts 5; # number of integration points for force-based element
element nonlinearBeamColumn 1 1 2 $numIntgrPts $ColSecTag $ColTransfTag; # self-explanatory when using variables
element nonlinearBeamColumn 2 2 3 $numIntgrPts $ColSecTag $ColTransfTag;
puts "Model Built"
# Define RECORDERS -------------------------------------------------------------
recorder Node -file Data1/Dnode2.out -time -node 2 -dof 2 disp; # displacements of free nodes
recorder Node -file Data1/Dnode3.out -time -node 3 -dof 2 disp;
#recorder Node -file Data1/DBase.out -time -node 1 3 -dof 1 2 3 disp; # displacements of support nodes
#recorder Node -file Data1/RBase.out -time -node 1 3 -dof 1 2 3 reaction; # support reaction
#recorder Drift -file Data1/Drift.out -time -iNode 1 -jNode 2 -dof 1 -perpDirn 2 ; # lateral drift
#recorder Element -file Data1/FCol.out -time -ele 2 globalForce; # element forces -- column
#recorder Element -file Data1/ForceColSec1.out -time -ele 1 section 1 force; # Column section forces, axial and moment, node i
#recorder Element -file Data1/DefoColSec1.out -time -ele 1 section 1 deformation; # section deformations, axial and curvature, node i
#recorder Element -file Data1/ForceColSec$numIntgrPts.out -time -ele 1 section $numIntgrPts force; # section forces, axial and moment, node j
#recorder Element -file Data1/DefoColSec$numIntgrPts.out -time -ele 1 section 1 deformation; # section deformations, axial and curvature, node j
# Pushover analysis ---------------------------------------------------------------------
constraints Plain; # how it handles boundary conditions
numberer Plain; # renumber dof's to minimize band-width (optimization), if you want to
system BandGeneral; # how to store and solve the system of equations in the analysis
test NormDispIncr 1.0e-8 10; # determine if convergence has been achieved at the end of an iteration step
algorithm Newton; # use Newton's solution algorithm: updates tangent stiffness at every iteration
integrator LoadControl 0.1; # determine the next time step for an analysis, # apply gravity in 10 steps
analysis Static # define type of analysis static or transient
# define LATERAL load -------------------------------------------------------------
set Pu [expr -300*$kN];
# Lateral load pattern
pattern Plain 1 Linear {
load 2 0 $Pu 0.0; # node#, FX FY MZ -- representative lateral load at middle node
}
# pushover: load controlled static analysis
#integrator LoadControl 0.1; # switch to displacement control, for node 11, dof 1, 0.1 increment
analyze 10; # apply 10 steps of pushover analysis
puts "Done!"
print node 2
print node 3
wipe