Introduction to
OpenSees and Tcl
Frank McKenna
UC Berkeley
OpenSees Parallel Workshop
Berkeley, CA
What is OpenSees?
The Open System for Earthquake Engineering Simulation is:
• A software framework for developing sequential, parallel
and grid-enabled finite element applications in earthquake
engineering.
• It is written primarily in the object-oriented programming
language C++.
• C++ wrappers are provided so that legacy and new
procedures (elements, materials, numerical routines)
written in other languages C, Fortran can be used.
• Funding for OpenSees has been provided by:
– PEER (Pacific Earthquake Enginering Research Center)
– NEES (George E. Brown, Jr. Network for Earthquake Engineering
Simulation) through NEESit.
– NSF (National Science Foundation)
What is a Software Framework?
• A framework is NOT an executable.
• A framework IS a set of cooperating software components for
building applications in a specific domain.
• In object-oriented terms, a framework is a collection of
abstract and concrete classes. The abstract classes define how
the classes interact, the concrete classes are classes users can
use to build applications.
• A framework dictates the architecture of the application. A
good design will cover the majority of applications within the
domain.
• Loose-coupling of components within the framework is
essential for extensibility and re-usability of the applications.
Object-Oriented Programming
• In object-oriented programming, the
program is seen as a collection of
objects. Each object is capable of 1
2
receiving messages, processing data, and 4 3
sending messages to other objects.
• Each object is of a particular type or Element
Class. The class defines the data and getTangent()
methods of an object. getResidual()
• 3 basic relationships between classes
1. IS-A (Truss is an Element)
Truss Node
2. KNOWS-A (Truss knows a Node)
getTangent()
3. HAS-A (Truss has a Material) Material
getResidual()
A
Conceptual Approach for Simulation
Material &
Element Models
Models
Information
Technology Computation
Software framework,
Algorithms & Solvers
Databases, Visualization,
(Sequential, Parallel, Distribued)
Internet/grid computation
Simulation Framework
Main Abstractions in OpenSees
Holds the state of the model
i
at time t and (t + dt)
ModelBuilder Domain Analysis
Constructs the objects Moves the model
in the model and adds from state at time t to
them to the domain. state at time t + dt
Recorder
Monitors user defined
parameters in the
model during the
analysis
Recorder Types in OpenSees
Recorder
}
ElementRecorder
NodeRecorder DataOutputHandler
EnvelopeNodeRecorder
EnvelopElementRecordr
DatebaseRecorder
FilePlotter
Display } Renderer StreamHandler
FileHandler
DatabaseHandler Database
X11
OpenGL
VRML File
MySQL
Oracle
NEES
What is in a Domain?
Domain
Element Node MP_Constraint SP_Constraint LoadPattern TimeSeries
Truss
ZeroLength ElementalLoad NodalLoad SP_Constraint
ElasticBeamColumn
NonlinearBeamColumn(force, displacement)
BeamWithHinges Constant
Quad(std, bbar, enhanced, u-p) Linear
Shell Rectangular
Brick(std, bbar, 20node, u-p, u-p-U) Sine
Joint Path
GenericClient
ExperimentalElement
Some Other Classes associated with Elements:
Element in Global System
U P
GeomTransformation
Geometric Transformation
Linear
Pdelta v q
Corotational
Element in Basic System
Other Classes associated with Elements:
Material
Uniaxial nD Section
Elastic Elastic Elastic
ElasticPP J2 Fiber
Hardening TemplateElasto-Plasto
Concrete FluidSolidPorous
Steel PressureMultiYield(dependent, independent)
Hysteretic
PY-TZ-QZ
Parallel
Series
Gap
Fatigue
What is an Analysis?
Analysis
CTest
StaticAnalysis
TransientAnalysis
CHandler Numberer AnalysisModel SolnAlgorithm Integrator SystemOfEqn
StaticIntegrator
Penalty RCM EquiSolnAlgo LoadControl BandGeneral
DispControl
Lagrange MinDegree Linear BandSPD
ArcLength
Transformation NewtonRaphson … ProfileSPD
ModifiedNewton TransientIntegrator SparseGeneral
Broyden Newmark SparseSymmetric
BFGS HHT
KrylovNewton CentralDifference
NewtonLineSearch NewmarkExplicit
HHT_Explicit
AlphaOS
How Do People Use Framework?
• Provide their own main() function in C++ and
link to framework.
• Use OpenSees interpreterS. These are
extensions of the Tcl interpreter for finite
element analysis which use the framework.
OpenSees.exe
• OpenSees.exe is an extension of the Tcl
interpreter for finite element analysis which
uses this framework. It is an example of an
application that can be developed using the
framework.
What is Tcl
• Tcl is a programming language.
• It is a string based command language.
• Variables and variable substitution
• Expression evaluation
• Basic control structures (if , while, for, foreach)
• Procedures
• File manipulation
• Sourcing other files.
• Comand syntax:
command arg1 arg2 …
• Help
1. http://dev.scriptics.com/scripting/primer.html
2. Practical Programming in Tcl and Tk, Brent B. Welch.
Tcl Interpreters
• wish and tclsh are tcl interpreters.
• Interpreters (Perl, Matlab, Ruby) are programs that execute
programs written in a programming language immediately.
• There is no separate compilation & linking.
• An interpreted program runs slower than a compiled one.
puts “sum of 2 and 3 is [expr $2 + $3]”
sum of 2 and 3 is 5
Example Tcl •procedures & control structures
for {set i 1} {$i < 10} {incr i 1} {
•variables & variable substitution puts “i equals $i”
}
>set a 1 set sum 0
>1 foreach value {1 2 3 4} {
>set b a •expression evaluation set sum [expr $sum + $value]
>a
>set b $a
>expr 2 + 3 }
>5 set $sum
>1
>set b [expr 2 + $b] >10
>3 >proc guess {value} {
global sum
•file manipulation if {$value < $sum} {
puts “too low”
>set fileId [open tmp w] } else {
>?? •sourcing other files if {$value > $sum} {
>puts $fileId “hello”
>close $fileID >source Example1.tcl puts “too high”
>type tmp } else { puts “you got it!”}
hello }
}
> guess 9
too low
Commands to Tcl for OpenSees
• For OpenSees we have added commands to Tcl for
finite element analysis:
1. Modeling – create nodes, elements, loads and constraints
2. Analysis – specify the analysis procedure.
3. Output specification – specify what it is you want to monitor
during the analysis.
Model Generation:
*Adds the modelling commands to the interpreter.
•BasicBuilder
model Basic –ndm ndm? <-ndf ndf?>
This command now adds the following commands to the interpreter:
node mass block2D
element fix block3D
pattern fixX patch
fix fixY layer
equalDOF fixZ fiber
pattern uniaxialMaterial
load nDMaterial
eleLoad section
sp geomTransf
Analysis Analysis
Ctest
StaticAnalysis
TransientAnalysis
CHandler Numberer AnalysisModel SolnAlgorithm Integrator SystemOfEqn
Penalty RCM EquiSolnAlgo StaticIntegrator BandGeneral
Lagrange MinDegree Linear LoadControl BandSPD
Transformation NewtonRaphson DispControl ProfileSPD
handler type? args… ModifiedNewton ArcLength SparseGeneral
numberer type? args… Broyden
BFGS
MinUnbalDispNorm SparseSymmetric
algorithm type? args… KrylovNewton TransientIntegrator
test type? args… Newmark
HHT
integrator type? args… CentralDifference
NewmarkExplicit
system type? args… AlphaOS
analysis type? args.. NewmarkHybrid
analyze args … HHT_Hybrid
…
Example Model:
model Basic -ndm -ndf 2 50 100
node 1 0.0 0.0 4
node 2 144.0 0.0
node 3 168.0 0.0 8’
(1) (2) (3)
node 4 72.0 96.0
fix 1 1 1
fix 2 1 1 1 2 3
fix 3 1 1
6’ 6’ 2’
uniaxialMaterial Elastic 1 3000.0
E A
element truss 1 1 4 10.0 1
element truss 2 2 4 5.0 1 1 3000 10
element truss 3 3 4 5.0 1 2 3000 5
pattern Plain 1 “Linear” { 3 3000 5
load 4 100.0 -50.0
}
Example Model:
model Basic -ndm -ndf 2 50 100
node 1 0.0 0.0 4
node 2 144.0 0.0
node 3 168.0 0.0 8’
(1) (2) (3)
node 4 72.0 96.0
fix 1 1 1
fix 2 1 1 1 2 3
fix 3 1 1
6’ 6’ 2’
uniaxialMaterial Elastic 1 3000.0
element truss 1 1 4 10.0 1
element truss 2 2 4 5.0 1
element genericClient 3 -node 2 3 -dof 1 2 -server 8090 127.0.0.1
pattern Plain 1 “Linear” {
load 4 100.0 -50.0
}
Example Analysis:
•Static Nonlinear Analysis with LoadControl
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6 2
algorithm Newton
integrator LoadControl 0.1
analysis Static
analyze 10
•Transient Nonlinear Analysis with Newmark
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6 2
algorithm Newton
integrator Newmark 0.5 0.25
analysis Transient
analyze 2000 0.01
Commands that Return Values
•analyze command
The analyze command returns 0 if successful.
It returns a negative number if not
set ok [analyze numIter <ΔΤ>]
•getTime command
The getTime command returns pseudo time in Domain.
set currentTime [ getTime]
•nodeDisp command
The nodeDisp command returns a nodal displacement.
set disp [ nodeDisp node dof]
Example Usage – Displacement Control
set maxU 15.0; set dU 0.1
constraints transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6 2
algorithm Newton
integrator DispControl 3 1 $dU
analysis Static
set ok 0
set currentDisp 0.0
while {$ok == 0 && $currentDisp < $maxU} {
set ok [analyze 1]
if {$ok != 0} {
test NormDispIncr 1.0e-6 1000 1
algorithm ModifiedNewton –initial
set ok [analyze 1]
test NormDispIncr 1.0e-6 6 2
algorithm Newton
}
set currentDisp [nodeDisp 3 1]
}
Example Usage – Transient Analysis
set tFinal 15.0; set dT 0.01;
constraints Transformation
numberer RCM
system BandGeneral
test NormDispIncr 1.0e-6 6 2
algorithm Newton
integrator Newmark 0.5 0.25
analysis Transient
set ok 0
set currentTime 0.0
while {$ok == 0 && $currenTime < $tFinal} {
set ok [analyze 1 $dT]
if {$ok != 0} {
test NormDispIncr 1.0e-6 1000 1
algorithm ModifiedNewton –initial
set ok [analyze 1 $dT]
test NormDispIncr 1.0e-6 6 2
algorithm Newton
}
set currentTime [getTime]
}
And Why do Finite Element Analysis
NCEER frame tested at the Taiwan facility
OpenSees
Test data
Floor shear - inter story drift : Floor 2 Floor shear - inter story drift : Floor 2
500 600
400
400
300
200
200
100
0 0
-100
-200
-200
-300
-400
-400
-500 -600
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
Centerline model and model with joint comparison
And Finally Why OpenSource
• Linus’s Law: “Given enough eyeballs, all bugs are
shallow”.
• Zero cost software attracts users!
• Prevents community from losing software. (especially
true in a research community)
• Allows Community to examine new ideas. (vital in a
research community were new ideas can be tested and
validated by all instead of being hidden behind some
theory in a paper and limited to researchers own test
data)
