post-buckling analysis of steel struts

[pejman_opensees]

this is a standardized code which peforms cyclic loading test on a steel
tubular strut. model definition is according to tests done by popov et al in EERC 81/04.
pinned-pinned tubular steel struts with a snap through( inital deformation) is modeled and several hysteritic loading loop is applied and the result completely matches with the experimental hysteritic loops depicted by popov et al (in page 58 EERC 81/04).
(units are kips-in)

Code: Select all

wipe
model basic -ndm 2 -ndf 3
node 1 0 0
node 2 152.81 0.61123
node 3 305.6184 0
fix 1 1 1 0
fix 3 0 1 0
fix 2 0 0 0
geomTransf Corotational 1   
uniaxialMaterial Steel02 1 40 29800 0.003 20 0.925 0.15 0.0005 0.01 0.0005 0.01
section Fiber 1 {
patch circ 1 20 2 0 0 7.75 8.25 0 360
}

element nonlinearBeamColumn 1 1 2 4 1 1
element nonlinearBeamColumn 2 2 3 4 1 1

recorder Node -file Node2.out -time -node 3 -dof 1  disp
recorder plot node2.out test 0 0 400 400 -columns 2 1

and loading is as follows:

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pattern Plain 1 Linear { load 3 1.0 0.0 0.0}
test EnergyIncr 1.0e-8 30 0
algorithm Newton
system UmfPack
numberer RCM
constraints Plain
analysis Static
set peak [ list 0.25 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5 5.5 6]
for {set i 1} {$i<=13} {incr i} {
	set dU [expr -1.0*pow((-1.0),$i)*[lindex $peak [expr $i-1]]/100.0]
	integrator DisplacementControl 3 1 $dU 1 $dU $dU
	analyze 100
}

hope it will help!

[/code]

[luoyunbiao]

thank you!It is very useful.