Project Title/ID Number PEER Analysis Platform for Demand Simulation—4102003
Start/End Dates 10/1/03—9/30/04
Project Leader Gregory Fenves (UCB/F)
Team Members Filip Filippou (UCB/F), Frank McKenna (UCB/O), Silvia Mazzoni (UCB/O), Michael Scott (UCB/GS), Jaesung Park (UCB/GS), Yoshi Takahashi (Kyoto Univ/O)

F=faculty; GS=graduate student; US=undergraduate student; PD=post-doc; I=industrial collaborator; O=other

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1. Project Goals/Objectives:

The objectives of this project are to design, develop, implement, and utilize OpenSees, a software framework for simulation of structural and geotechnical systems. The open-source software is an important enabling technology within PEER because it allows integration of the results of research in structural performance modeling, geotechnical modeling of soils and foundations, computational methods, and advanced information technologies, such as databases and visualization. The software is critical to the conduct of the testbed projects and benchmark studies, and the lessons-learned in the testbed projects have been used to improve and extend the models.

2. Role of this project in supporting PEER’s mission (vision):

PEER’s research mission to develop performance-based earthquake engineering methods is highly dependent on improved capability for simulation the response and performance of structural and geotechnical systems. OpenSees is intended to provide the modeling and computational simulation capability necessary for PBEE applications. The focus of the research program has been to improve the models of structural concrete, foundation components, and soils to be able to estimate engineering damage parameters (EDP) and damage variables (DM) through realistic simulations.

3. Methodology Employed:

The approach for this project is three-phased. The first-phase is continuing development of the OpenSees software architecture for PBEE applications. The second-phase is the development of specific models and solution methods that have broad applicability to PEER research, their validation, and usage. Finally, the third phase is release, support and training for OpenSees users and developers.

The project is under the direction of the principal investigator, with coordination of the related research of the co-principal investigator. Three other staff members are supported to accomplish the objectives of the project. Dr. Francis McKenna is the lead developer of OpenSees. He is responsible for the integration of all work related to the software for consistency with the project’s development standards and for the technical improvements in the models and computational procedures. The graduate student is completing research on software architectures for modeling, including a family of material and elements formed by aggregation software patterns, efficient nonlinear solution strategies based on Krylov updates, and for incorporating response sensitivity calculations throughout the simulation procedures (for reliability, system ID, and optimization applications). Dr. Silvia Mazzoni is responsible for the user support activities, conducting workshops, and maintaining the documentation.

4. Brief Description of past year’s accomplishments (Year 6) & more detail on expected Year 7 accomplishments:

The major deliverable at the end of Year 6 was to have version 1.5 of OpenSees available for use in the PEER testbed projects. This included the beam-column models for reinforced concrete with material and geometric nonlinearities. A new capability for degrading shear modeling was included.

Accomplishments in Year 7 are:

  1. Developing exact sensitivity computation for force-based beam-column elements to use in reliability applications,
  2. New quasi-newton solution method using Krylov vectors to stabilize solution of highly nonlinear problems with good convergence rate,
  3. Support and interaction with testbed projects in use of OpenSees modeling and simulations, and iv) improved user documentation and release packages. A user workshop was held in August 2003 and another one was given in January 2004, coordinated with a NEES research project.

In Year 7, substantial progress has been made in making OpenSees available for NEES. The NEESgrid system integration project has selected OpenSees for the simulation component. The SPUR project (Seismic Performance of Urban Regions) is another coordinated project developing OpenSees simulation applications.

5. Other Similar Work Being Conducted Within and Outside PEER and How This Project Differs:

Although there has been much good research on modeling and simulation of structural and geotechnical systems, OpenSees continues to be a unique project that integrates the results of the research into a common software framework. The flexible, object-oriented design is the unique aspect of the approach that makes this possible.

The force-based beam-column elements with material and geometric nonlinearities are a unique contribution of this research project.

6. Plans for Year 8 if project is expected to be continued:

Plans are underway for version 2.0 of OpenSees, which will include new data structures and application program interfaces for multi-physics problems and for parameterization of models. The former is needed for advanced models of soil liquefaction. The latter is needed for extending the sensitivity calculations and reliability and optimization applications. In addition, new capabilities will be provided for computing and recording damage variables (DV) of systems.

7. Describe any actual instances where you are aware your results have been used in industry:

We have had three inquiries from industry about using parts of OpenSees for computational aspects of analysis software they are developing. We are in the process of developing specific policies for commercial use of OpenSees, consistent with the copyright held by the University of California Regents. OpenSees is open source and may be used for unrestricted, non-commercial applications.

8. Expected Milestones & Deliverables:

By the end of this year, we will have completed version 1.6 based on testbed project experiences. It will include the capability listed in box 4. The user documentation will be updated and posted on the website using modern web-based documenting authoring software.

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