1_workshop2003GLF

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P P E E

E E R R OpenSees User Workshop 2003

Presented by the OpenSees CommunityGregory L. FenvesAugust 21-22, 2003

Sponsored by the National Science Foundationthrough the Pacific Earthquake Engineering Research Center

Context

PEER Research Program in Performance-BasedEarthquake Engineering.

Development of enabling technology is expectedof NSF research centers.

Many researchers and students for PEER ThrustArea Simulation and Information Technologyare contributing to technology development andapplication.

New initiatives such as NEES and MBS areencouraging new simulation methods andtechnology.


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Observations on Current Situation

Tight binding of models in research and commercialcodes is an impediment to new research andimplementation of models for professional practice.

Embedding of computational procedures in codes makesit difficult to experiment and take advantage ofcomputing technology: Parallel and distributed computers

Computational grids Closed-source is the norm, whereas other fields haveadopted open-source software for communitiesusers.

What is OpenSees?

A software framework for simulation applicationsin earthquake engineering using finite elementmethods. OpenSees is not a code.

A communication mechanism within PEER, and beyond, for exchanging and building uponresearch accomplishments.

As open-source software, it has the potential for acommunity code for earthquake engineering.


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Open-Source Community Simulation Framework

Conceptual Approach for Simulation

InformationTechnology Software framework,

Databases, Visualization,Internet/grid computation

Computation Algorithms,Solvers,Parallel/distributedcomputing

ModelsMaterial, component,system models

Simulation models,Performance models,Limit state models

Software Framework

A framework is a set of cooperating software components for building applications in a specific domain.

A framework dictates the architecture of the application. Itmust represent the design decisions common to the applicationdomain.

A frameworks is based on the assumption that an architecturewill work for most applications within the domain.

Loose-coupling of components within the framework isessential for extensibility and re-useability for applications.

Examples: Visualization (GLUT), MS Office, compilers ... A framework is not a code


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Simulation Software Alternatives

Compute Technology

Base Code

Elements

Input Language

User Interface

Traditional Code

Model Domain

Materials

Framework of Components

Solvers

Compute Technology

Elements

Databases

Solution Procedures

Other

V i s u a l i z a t i o n

M o d e l B u i l d e r s

Application ProgramInterface (API)

What Should be Your Expectations?

OpenSees is a research tool at this time, but fairlystable for regular use

As with any nonlinear analysis, it requires carefulconsideration of model and interpretation of results

It is under continual development by students, facultyand other researchers

User interface development lags behindcomputational technology

It is not bullet-proof An investment of time and learning is required


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Objective of Workshop

Describe modeling and analysis capability, includinghierarchy of system, element, section, material

Overview of applications, structural andgeotechnical

Provide specific examples of nonlinear analysis as astarting point

Introduction to user interfaces under development

Pointers to more information and user support

Beam-Column Models I

Elementu p

Basic System

v qq1,v 1q3,v 3

q2,v 2

GeometricTran

u

p = af T q

p

u = a f u

Linear LinearPDCorotational


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Section

e s

e , s

s = asT

A dA )( =

= as e

Material

No assumptions are made on section or material behavior;each level in the hierarchy can be defined independently ofother levels

Beam-Column Models II

s = bq

v = bT e dx 0

L

e = av

q = aT s dx 0

L

Basic Systemv q

q1,v

1q3,v 3

q2,v 2

Displacement Force

UniaxialMaterial Behavior

Material

UniaxialMaterial

Concrete01 Steel01 Hysteretic BiLinear

Also:EPPEPP-GapCloughPinchHardening


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Aggregate UniaxialMaterials

Material

UniaxialMaterial

SeriesMaterialParallelMaterial

Rapidly develop modelsfrom existing implementations,e.g., composite gapping material

aParallelMaterial

aLeafMaterialaSeriesMaterial

aLeafMaterial aLeafMaterial

,

Composite Pattern

Material

ForceDeformationUniaxialMaterial

BeamWithHinges

2

FiberSectionFiber

UniaxialFiber

Concrete01 Steel01

s = a sT

dA a sT ( )i Aii=1

N f

Aa s = [1 y z]

The Fiber abstraction keeps the FiberSection classunaware of the response it integrates, making for aflexible design; however, there is a performancepenalty associated with flexibility.

Form Follows Mechanics


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Beam-Column Modeling

Material

ForceDeformationUniaxialMaterial

NonlinearBeamColumn beamWithHinges

2

API

setTrialSectionDeformation()getStressResultant()getSectionTangent()getSectionFlexibility()com mitState()getType()

Distributed

plasticity

Concentrated

plasticity

f = bT f sL bdx

Organization of Workshop

Tcl command language; what is Tcl? Modeling commands

System, element, section, material hierarchy Analysis commands

Standard and advanced methods Basic examples and use of parameters Advanced structural and geotechnical applications Other user interfaces


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Thanks to:

Silvia Mazzoni Parshaw Vaziri Veronica Padilla Frank McKenna Michael Scott Boris Jeremic

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