Displacement Control

[Kbra]

Is it possible to include the P-Delta effect when conducting static analysis with a displacement integrator?

And in case; is it nessesary to define the gravity load in a special way?
Unlike:
pattern plain 1 constant {....}

My output values doesn't seem to affected by the P-Delta transformation

Code: Select all

# GEOMETRIC TRANSFORMATION
geomTransf PDelta 1

# DEFINE DISPLACEMENT BEAM-COLUMN ELEMENTS                
# Columns
#                      tag ndI ndJ  nPts secID transf
element dispBeamColumn  1   1   2    $nP   2      1
element dispBeamColumn  2   2   3    $nP   2      1
element dispBeamColumn  3   4   5    $nP   1      1
element dispBeamColumn  4   5   6    $nP   1      1
element dispBeamColumn  5   7   8    $nP   2      1
element dispBeamColumn  6   8   9    $nP   2      1

# Beams
element dispBeamColumn  7   2   5    $nP   3      1
element dispBeamColumn  8   5   8    $nP   3      1
element dispBeamColumn  9   3   6    $nP   3      1
element dispBeamColumn 10   6   9    $nP   3      1

# CONSTANT GRAVITY LOADS
pattern Plain 1 Constant {
   #    node  FX    FY   MZ
   load   2  0.0 -0.96e1  0.0 
   load   5  0.0 -1.92e1   0.0 
   load   8  0.0 -0.96e1  0.0 
   load   3  0.0 -0.48e1  0.0 
   load   6  0.0 -0.96e1  0.0 
   load   9  0.0 -0.48e1  0.0 
}
pattern Plain 2 Linear {
   #    node  FX   FY   MZ
   load   2 $load  0.0  0.0
   load   3 $load  0.0  0.0
}

# FINITE ELEMENT ANALYSIS MODEL
integrator DisplacementControl  3   1   1   
test NormDispIncr  1.0e-06     10         0
algorithm Newton
numberer RCM
constraints Transformation
system ProfileSPD
sensitivityIntegrator -static
sensitivityAlgorithm -computeAtEachStep 
analysis Static

# RECORDERS
recorder Node Node.out disp -time -node 3 -dof 1
recorder Element 1 3 5 -file Element.out section 1 deformations

analyze 500

[fmk]

pdelta works with displacement control .. you need to do a gravity load analysis before you
start the pushover however .. otherwise the reference load (pHat in the theory) will include the gravity loads.