MomentCurvature.tcl

• # A procedure for performing section analysis (only does moment-curvature, but can be easily modified to do any mode of section reponse.

# MHS

# October 2000

#

# Arguments

# secTag -- tag identifying section to be analyzed

# axialLoad -- axial load applied to section (negative is compression)

# maxK -- maximum curvature reached during analysis

# numIncr -- number of increments used to reach maxK (default 100)

#

# Sets up a recorder which writes moment-curvature results to file

# section$secTag.out ... the moment is in column 1, and curvature in column 2

proc MomentCurvature {secTag axialLoad maxK {numIncr 100} } {

# Define two nodes at (0,0)

node 1 0.0 0.0

node 2 0.0 0.0

# Fix all degrees of freedom except axial and bending

fix 1 1 1 1

fix 2 0 1 0

# Define element

# tag ndI ndJ secTag

element zeroLengthSection 1 1 2 $secTag

# Create recorder

recorder Node section$secTag.out disp -time -node 2 -dof 3

# Define constant axial load

pattern Plain 1 "Constant" {

load 2 $axialLoad 0.0 0.0

}

# Define analysis parameters

integrator LoadControl 0 1 0 0

system SparseGeneral -piv; # Overkill, but may need the pivoting!

test NormUnbalance 1.0e-9 10

numberer Plain

constraints Plain

algorithm Newton

analysis Static

# Do one analysis for constant axial load

analyze 1

# Define reference moment

pattern Plain 2 "Linear" {

load 2 0.0 0.0 1.0

}

# Compute curvature increment

set dK [expr $maxK/$numIncr]

# Use displacement control at node 2 for section analysis

integrator DisplacementControl 2 3 $dK 1 $dK $dK

# Do the section analysis

analyze $numIncr

}