The following sample shows that you need to divide the thickness by 2 !!!
# OpenSees Example 7.1 modified
# OpenSees Primer
#
# Units: N, m, sec
# ----------------------------
# Start of model generation
# ----------------------------
model basic -ndm 3 -ndf 6
# create the material
#
# ---------------
# WARNING !!!
# ---------------
#
# to obtain the true theoretical value the thickness is h/2 !!!
# theoretical value : w=0.00406*p*a*a*a*a/D
# with D=E*h*h*h/12/(1-nu*nu)
# with p=0.2*2500*9.81=4905 N/m2
# w=0.00406*4905*5*5*5*5/9.028e6=1.378e-3
# here we put thick=0.1 and we obtain w=1.408e-3 !!!
#
#
section ElasticMembranePlateSection 1 1.3e10 0.20 0.1 2500.
# set some parameters for node and element generation
set Plate ShellMITC4
set eleArgs "1"
#these should both be even
set nx 10
set ny 10
#loaded nodes
set mid [expr ( ($nx+1)*($ny+1)+1 ) / 2 ]
set side1 [expr ($nx + 2)/2 ]
set side2 [expr ($nx+1)*($ny+1) - $side1 + 1 ]
# generate the nodes and elements
block2D $nx $ny 1 1 $Plate $eleArgs {
1 0. 0. 0
2 5. 0. 0
3 5. 5. 0
4 0. 5. 0
}
# add some loads
pattern UniformExcitation 1 3 -accel { Constant -factor 9.810E+00 }
# define the boundary conditions
# rotation free about x-axis (remember right-hand-rule)
fixX 0.0 1 0 1 0 0 0
fixX 5.0 0 0 1 0 0 0
fixY 0.0 0 1 1 0 0 0
fixY 5.0 0 0 1 0 0 0
# Load control with variable load steps
# init Jd min max
integrator LoadControl 1.0 1 1.0 10.0
# Convergence test
# tolerance maxIter displayCode
test EnergyIncr 1.0e-10 20 2
# Solution algorithm
algorithm Newton
# DOF numberer
numberer RCM
# Cosntraint handler
constraints Plain
# System of equations solver
system SparseGeneral -piv
#system ProfileSPD
# Analysis for gravity load
#analysis Transient
analysis Static
# Perform the gravity load analysis
analyze 1
# --------------------------
# End of static analysis
# --------------------------
# Print the results
print plaqapp.ops
Wrong results with a simply supported plate with uniform loa
Moderators: silvia, selimgunay, Moderators
try using nodal loads instead of uniform exciatation and elemental mass.
set a 5.0;
set h 0.2;
set E 1.3e10;
set w0 2500.0
set g 9.81
set x1 [expr $a/$nx]
set y1 [expr $a/$ny]
set p [expr $h * $w0 * $g *$x1 *$y1]
puts $p
pattern Plain 1 Linear {
for {set i 1} {$i <= [expr ($nx+1)*($ny+1)]} {incr i 1} {
load $i 0.0 0.0 $p 0.0 0.0 0.0
}
}
set a 5.0;
set h 0.2;
set E 1.3e10;
set w0 2500.0
set g 9.81
set x1 [expr $a/$nx]
set y1 [expr $a/$ny]
set p [expr $h * $w0 * $g *$x1 *$y1]
puts $p
pattern Plain 1 Linear {
for {set i 1} {$i <= [expr ($nx+1)*($ny+1)]} {incr i 1} {
load $i 0.0 0.0 $p 0.0 0.0 0.0
}
}