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

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

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)

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

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

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

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

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 Chadwell UC Berkeley

OpenSees Model

Response to Pulse Motion

Response to Recorded Motion TCU079 TCU129

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