1. Seismic Simulation: Advances with OpenSees
Gregory L. Fenves University of California, Berkeley
PEER Annual Meeting January 18, 2002

2. 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.

3. 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.

4. 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.

5. Conceptual Approach for Simulation
Open-Source Community
Simulation Framework
Computation
Algorithms,
Solvers,
Parallel/distributed
computing
Information Technology
Software framework,
Databases, Visualization,
Internet/grid computation
Models
Material, component, system models
Simulation models,
Performance models,
Limit state models

6. 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)

7. Beam-Column Geometry Element GeometricTran Basic System Linear
LinearPD
Corotational (Filippou)

8. Beam-Column Models Basic System Section Material Displacement Force
e, s s e
Material
No assumptions are made on section or material behavior; each level in the hierarchy can be defined independently of other levels

9. Beam-Column Modeling Distributed Concentrated plasticity plasticity
Material
UniaxialMaterial
ForceDeformation 2
NonlinearBeamColumn
beamWithHinges
Distributed
plasticity
Concentrated
plasticity

10. Aggregation of Section Model
yield
ultimate
residual f M
residual
ultimate
cracking V g
0,1
ForceDeformation
SectionAggregator
UniaxialMaterial
Decorator Pattern
Options for coupling:
New ForceDeformation Class
Inter-object communication

11. 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

12. 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.

13. Simulation Services Architecture
Law, Peng, Stanford

14. Application: Performance of Cable-Stayed Bridge
Charles Chadwell UC Berkeley

15. OpenSees Model

16. Response to Pulse Motion

17. Response to Recorded Motion
TCU079
TCU129

18. Issues for 2002 PEER Testbeds 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)
PEER Testbeds