About the amount of reference load in load-control pushover

[ismailqeshta]

Hi,
I am running a pushover analysis using load-control integrator. I notice that the yield load does not change with the change in the magnitude of reference loads. I obtain the same results in all load cases, similar to the displacement-control one. What would be the possible reason?
I use the following load control procedure, I usually change the "integrator LoadControl" increment and "analyze" number of steps for the trial and error runs:

# Start Analysis
# System of equations
system BandGeneral
# DOF numberer
numberer Plain
# Constraint handler
constraints Transformation
# Convergence test
test NormDispIncr 1.0e-12 1000
# test EnergyIncr 10e-6 400
# Integrator
integrator LoadControl 50000
# Solution algorithm
algorithm Newton
# algorithm ModifiedNewton
# algorithm KrylovNewton
# Analysis object
analysis Static
# -------------------------
if {[analyze 1000] == 0} {
puts "Model SUCCESSFULLY COMPLETED"
} else {
puts "Model FAILED"
exit
}


Regards.

[giovannimilan]

What do you mean exactly?
Would you expect that the yielding force is changing depending on the external load you apply?

Yielding force is capacity. It depends on the material property and geometry of the elements.

[ismailqeshta]

Hi giovannimilan

Many thanks for your reply.

I mean, for example, if I apply 10 N, the load-deformation curve will stop at a certain value, while when I apply 20 N, the curve will stop at larger load-deformation value. This is what I expected.

However, they all stop at the yielding force, even with small loads that I don't think they are large enough to cause yielding of the structure.

Regards,

[giovannimilan]

if I were u, i would check the forces from the disp control analysis, because it is not easy to say how "small" your loads in the load controlled analysis are.

[ismailqeshta]

Hi giovannimilan,

Many thanks for your reply.

Actually, I am a bit confused about the total amount of load to be applied on the structure, and the reference load to be specified.

For example,

If I want to apply a "total load" of 10 N on a frame of two columns. Assume the lateral load is applied at the top of the first column. How shall I apply the 10 N?

I notice that the load increment is equal to reference load times the step size, i.e. for integrator LoadControl 5, analyze 10 and reference load 10, the load would be applied as increasing loads of 50 N until "total load" of 500 N.

Regards.