peer seismic simulation: advances with opensees gregory l. fenves university of california, berkeley...
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PPEEEERR
Seismic Simulation:Advances with OpenSees
Gregory L. FenvesUniversity of California, Berkeley
PEER Annual MeetingJanuary 18, 2002
Simulation in PBEE
• Performance Based Engineering depends on evaluation seismic demands (EDP) and damage (DM).
• Rational, validated models of behavior of structural and geotechnical materials, components and systems are needed for simulating performance.
• Simulation applications:– Assessment– Design using parameterized models– Reliability-based design
• Improved software needed for PBEE methodologies.• OpenSees is PEER’s software framework for seismic
simulation to support these applications.
Status of OpenSees
• All information available on website at opensees.berkeley.edu– Documentation– Source code browser– Downloads (source code, Win32 exe)
• Version 1.2 is the current release• Development versions ahead of release, but most
developments available in CVS (source code versioning system) for checkout.
OpenSees in 2001
• Nonlinear static and dynamic analysis of 3D structural and soil-foundation systems.
• Increase robustness and performance.• Begin to support simulation needs for testbeds.• Continue as research platform for modeling of
non-ductile components, particularly degrading shear behavior.
• Work on documentation and user/developer workshops.
Open-Source CommunitySimulation Framework
Conceptual Approach for Simulation
InformationTechnology Software framework,
Databases, Visualization,Internet/grid computation
ComputationAlgorithms,Solvers,Parallel/distributedcomputing
ModelsMaterial, component, system models
Simulation models,Performance models,Limit state models
Summary of Models
• Elements– Beam-column elements for 2D and 3D based on force
formulation– Zero-length elements– Plate elements (new)– 2D and 3D continuum elements (including mixed
formulation for incompressibility)• Materials
– Library of 1D uniaxial models• Fairly general hysteretic models• New p-y models
– Constitutive models (e.g. J2 plasticity, soil models)
Elementup
Basic System
v q
q1,v1q3,v3
q2,v2
GeometricTran
u
p=afT q
p
u=afu
LinearLinearPDCorotational (Filippou)
Beam-Column Geometry
Section
e s
e, s
s = asTσ
A∫ dA
)(εσ=σ
ε =ase
Material
ε σ
No assumptions are made on section or material behavior; each level in the hierarchy can be defined independently of other levels
σ
ε
Beam-Column Models
s =bq
v = bTedx0
L
∫e=av
q= aTsdx0
L
∫Basic System
v qq1,v1q3,v3
q2,v2
Displacement Force
Aggregation of Section Model
e=
ε0
κ
γ
⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥
s =
P
M
V
⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥
ks =ks−sec 0
0∂V∂γ
⎡
⎣
⎢ ⎢
⎤
⎦
⎥ ⎥
yieldultimate
residual
M
residual
ultimate
cracking
V
0,1
ForceDeformation
SectionAggregator
UniaxialMaterial
Decorator Pattern Options for coupling: New ForceDeformation Class Inter-object communication
Models under Development
• Generalized hinge models for beam-columns (Deierlein)
• Beam-column joint models (Lowes)• Coupled shear-axial-flexure models (Filippou)• Continuing work on soil models
Computational Procedures
• Nonlinear solution algorithms:– Newton-Raphson– BFGS and Broyden’s– Other quasi-newton methods (e.g. using Krylov subspace
updates)– Line search options– Converge options and “remediation”
• Load stepping procedures:– Variety of nonlinear static, arc-length, displacement control…– Dynamic including Newmark, HHT
• Equation solvers– Several equation solvers available depending on problem
topology and computer hardware.
Simulation Services Architecture
Law, Peng, Stanford
Application: Performance of Cable-Stayed Bridge
Charles ChadwellUC Berkeley
OpenSees Model
Response to Pulse Motion
Response to Recorded Motion
TCU079 TCU129
Issues for 2002
• Models– Degradation, shear-flexure, bond slip, joints– Soil-pore fluid models– Pile-foundation models– Validation protocols– Input motions and coupled simulations
• PBEE Design and Simulation– Parameterization of models, sensitivity– Reliability
• Computing and Information Technology– Parallel and distributed computing– Visualization– Internet and “Grid Aware” applications (NEES)
PE
ER
Tes
tbed
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