Moment-curvature number of increments and convergence!

[ismailqeshta]

Hi,

I have a very basic question in the moment-curvature analysis example in opensees.

I wonder how the number of increments affect the convergence. For example, when I use number of increments of 100 I achieve the bi-linear curve, while I get only a straight line at much lower values when I increase the number of increments.

I thought the increase in the increment number would improve the results.

I am copying the code part below for your kind reference. The full example is in this link:
http://opensees.berkeley.edu/wiki/index ... re_Example

Can anyone please clarify this for me?

Thank you.

# Estimate yield curvature
# (Assuming no axial load and only top and bottom steel)
set d [expr $colDepth-$cover] ;# d -- from cover to rebar
set epsy [expr $fy/$E] ;# steel yield strain
set Ky [expr $epsy/(0.7*$d)]

# Print estimate to standard output
puts "Estimated yield curvature: $Ky"

# Set axial load
set P -180

set mu 15; # Target ductility for analysis
set numIncr 100; # Number of analysis increments

# Call the section analysis procedure
MomentCurvature 1 $P [expr $Ky*$mu] $numIncr

[selimgunay]

I tried with 100 and 1000 and they are both inelastic with a clear yield and both are quite similar. You might be doing something wrong.

[ismailqeshta]

Thanks Selim. Yes, the problem was with the tolerance.