ForceBeamColumn2d::update()--could not invert flexibility

[enginer]

Hi,I am a new user. I am using the following code
wipe;
puts "system"
model basic -ndm 3 -ndf 6
puts "restraint"
if {[file exists output]==0} {
file mkdir output;
}
#Cap beam node
node 77 30 -4 -2.3
node 78 30 -3.5 -2.3
node 79 30 -3 -2.3
node 80 30 -2.4 -2.3
node 81 30 -2 -2.3
node 82 30 -1.5 -2.3
node 83 30 -1 -2.3
node 84 30 -0.5 -2.3
node 85 30 0 -2.3
node 86 30 0.5 -2.3
node 87 30 1 -2.3
node 88 30 1.5 -2.3
node 89 30 2 -2.3
node 90 30 2.4 -2.3
node 91 30 3 -2.3
node 92 30 3.5 -2.3
node 93 30 4 -2.3
puts "node finish"
geomTransf Linear 1 0 0 1
geomTransf Linear 2 0 0 1
geomTransf Linear 3 1 0 0
#Cap beam simulation
set hntc3 30
set hntt3 2.1
set hnt3 6.0
set fcuk3 [expr 1e6*$hntc3]
set ftk3 [expr 1e6*$hntt3]
set fck3 [expr 1e6*$hnt3]
set fpc3 -$fcuk3
set epsc3 -0.002
set fpcu3 [expr 0.2*$fpc3]
set epscu3 -0.005
set ft3 -$ftk3
set Ets3 [expr -0.07*$fcuk3/0.002]
set lambda1 0.1
uniaxialMaterial Concrete02 4 $fpc3 $epsc3 $fpcu3 $epscu3 $lambda1 $ft3 $Ets3
puts "material finish"
#Cap beam section division
set GJ 2.11e9
section fiberSec 2 -GJ $GJ {
patch rect 4 10 10 -0.75 -0.75 0.75 0.75
};
#Cap beam element
element forceBeamColumn 252 77 78 5 2 2
element forceBeamColumn 253 78 79 5 2 2
element forceBeamColumn 254 79 80 5 2 2
element forceBeamColumn 255 80 81 5 2 2
element forceBeamColumn 256 81 82 5 2 2
element forceBeamColumn 257 82 83 5 2 2
element forceBeamColumn 258 83 84 5 2 2
element forceBeamColumn 259 84 85 5 2 2
element forceBeamColumn 260 85 86 5 2 2
element forceBeamColumn 261 86 87 5 2 2
element forceBeamColumn 262 87 88 5 2 2
element forceBeamColumn 263 88 89 5 2 2
element forceBeamColumn 264 89 90 5 2 2
element forceBeamColumn 265 90 91 5 2 2
element forceBeamColumn 266 91 92 5 2 2
element forceBeamColumn 267 92 93 5 2 2
puts "ele finish"
#fix
fix 77 1 1 1 1 1 1
puts "fix finish"
# 3）recorder
recorder Node -file D:/output/node93.txt -time -node 93 -dof 1 2 3 disp;
#Cap beam gravity
pattern Plain 1 Linear {
load 77 0 0 -13781.25 0 0 0
load 78 0 0 -27562.5 0 0 0
load 79 0 0 -27562.5 0 0 0
load 80 0 0 -27562.5 0 0 0
load 81 0 0 -27562.5 0 0 0
load 82 0 0 -27562.5 0 0 0
load 83 0 0 -27562.5 0 0 0
load 84 0 0 -27562.5 0 0 0
load 85 0 0 -27562.5 0 0 0
load 86 0 0 -27562.5 0 0 0
load 87 0 0 -27562.5 0 0 0
load 88 0 0 -27562.5 0 0 0
load 89 0 0 -27562.5 0 0 0
load 90 0 0 -27562.5 0 0 0
load 91 0 0 -27562.5 0 0 0
load 92 0 0 -27562.5 0 0 0
load 93 0 0 -13781.25 0 0 0
}
#Gravity analysis
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 100 0
algorithm Newton
integrator LoadControl 0.001
analysis Static
analyze 1000
loadConst -time 0.0


This is my code.However, it results in error as "ForceBeamColumn2d::update()--could not invert flexibility".
Please help with this.
Thanks

[mhscott]

You likely have a singular section stiffness matrix. Check your modeling approach with a simple model.

[enginer]

I know a singular section stiffness matrix.However how to deal with exactly?