Area 4Simulation and Information Technologies
Gregory Fenves (UCB), Thrust Leader
A central aspect of performance-based earthquake engineering (PBEE) is simulating the performance of building and bridge systems (broadly defined to include the foundations, soil, and non-structural components) during and after an earthquake to assess impacts in terms of direct loss, functional loss, and casualty loss. The goal of the research in this thrust area is to advance significantly the fidelity and resolution of simulations of structural and geotechnical systems. To achieve this goal, the thrust area research has three major aspects:
- development the modeling and simulation technology for impact assessment;
- creation of databases needed to verify and calibrate models; and
- implement data, models, and simulation technology in a software framework for use by researchers, PEER partners, and the general earthquake engineering community (eventually through NEES).
In the first four years of PEER, the research in simulation and information technologies focused on performance assessment of existing structures. The research was motivated by the inability to represent the complex, highly nonlinear behavior of cyclic loads on structural components and soil with enough fidelity to assess performance. Simulations are even more difficult when considering interactions of components in a building and bridges, such as load redistribution caused by cyclic degradation and the consequences of local failure mores. The PEER research program has addressed this need through a coordinated development of improved models of structural components (in this thrust area and the Structural Performance thrust area) and soils (Hazard Assessment and Geo-performance thrust area). The models must be based on the mechanics that represent the observed behavior of materials and components, and verified using databases of experimental data. As the PEER research program begins to develop performance-based design methodology, simulation will have an important role developing the relationship between seismic hazard and performance in terms of design parameters using the improved models. The incorporation of uncertainty in the simulation is necessary to use the results of simulation in a reliability-based approach for PBEE. In addition to the uncertainty of the earthquake hazard, the uncertainty of the data, models, and simulation method itself, must be accounted for in the performance impacts estimated by a simulation.
PEER is developing enabling technology for simulation and integration of simulation models with databases for experimental data, ground motion data, and performance impact loss data. OpenSees (Open System for Earthquake Engineering Simulation) is an advanced simulation software framework for structural and geotechnical facilities. Currently available software for simulating nonlinear behavior of soils and structures is inadequate with inadequate models and solution procedures. Commercial codes and most research codes have an inflexible software architecture that inhibits innovative use of modern information technology and high-performance computing. OpenSees (formerly known as G3) is designed to integrate the implementations of models for structural behavior, soil and foundation behavior, and damage measures. OpenSees is implemented in a modular, object-oriented manner with a clearly defined application program interface (API) for models, solution methods, equation solving, databases, and visualization. Each of these components are as independent as possible, which allows great flexibility in combining modules to solve classes of simulation problems for buildings and bridges, including soil and soil-structure-foundation interaction. The software is open source, meaning that all parts of the code are available for students, researchers, engineering professionals, and other users to see, check, track changes, and make contributions. The OpenSees website at http://opensees.berkeley.edu has a download center with executables, source code, examples, and documentation. Through the website users have access to a source-code revision control system, methods for submitting contributions, and a bulletin board for communication. OpenSees is the first instance of web-accessible, open-source software that can serve as a community code for earthquake engineering.
As a community code, OpenSees will provide a natural complement the National Science Foundation-sponsored George E. Brown, Jr. Network for Earthquake Engineering Simulation. The modular design of OpenSees means that it can be customized for the integrating physical and computation simulation through data repositories, visualization, and hybrid control for advanced experimental methods, all of which meet important NEES objectives.
PEER Analysis Platform for Demand Simulation—4102002
Gregory Fenves (UCB/F), Filip Filippou (UCB/F), Frank McKenna (UCB/PD), Silvia Mazzoni (UCB/PD), Michael Scott (UCB/GS), Asfin Saritas (UCB/GS)
The goal of this project is to advance the research for simulation capability of structural and geotechnical systems for performance-based earthquake engineering. The simulation software developed in the project utilizes advances in information technology and computing methods, and the development is collaborative, with an open-source methodology, that engages a large number of researchers in PEER and many outside PEER. The primary products of the project are:
- new models and methods for simulation of earthquake performance;
- and open-source software framework, OpenSees, that incorporates the latest research and computing technology; and
- a committed group of developers and users in the research community.
Simulation of structural and geotechnical systems is a key step in PEER PBEE methodologies. The PEER assessment methodology relies on simulation to compute engineering demand parameters and in some cases damage measures. PEER has embarked on software development because existing simulation software is inadequate for a number of reasons: models of behavior are too simplified, particularly for reinforced concrete; little support for soil-foundation-structure interaction; closed or antiquated software architecture makes it difficult to research new simulation methods; generally slow adoption of information technology; does not expose students to modern software engineering and computer science.
Development and Validation of Performance Models—4122002
Gregory Deierlein (Stanford/F), Rohit Kaul (Stanford/GS), Arash Altoontash (Stanford/GS)
High fidelity simulations are essential to the PEER PBEE methodology to accurately model seismic response, damage and collapse of buildings and bridges. Central to the effort of thrust area 4 is the development of OpenSees (Open System for Earthquake Engineering Simulation) - a versatile computing framework that integrates analysis models for seismic hazard, ground motions, soil response, soil-foundation structure interaction, and structural response. The focus of this project (4122002) is to develop and validate generalized hinge models for simulating strength and stiffness degradation in reinforced-concrete structures. Emphasis is on spring assemblies, generalized hinge elements, and cyclic hysteretic models for beam-columns and their connections that are sufficiently robust to capture highly nonlinear response at collapse, yet practical for application to large systems.
Computational Reliability for Design—4132002
Joel Conte (UCSD/F), Yuyi Zhang (UCSD/GS), Gabriel Acero (UCSD/GS), Quan Gu (UCSD/GS)
- Develop, implement, and document sensitivity and reliability analysis modules in OpenSees to facilitate solution of the PEER PBEE framework equation.
- Identify and model uncertainties (characterizing the seismic loading, system parameters, modeling assumptions, etc.) and track their propagation through nonlinear earthquake response analysis (using OpenSees) for the Humboldt Bay Bridge testbed structure.
- Demonstrate the various ingredients required in the solution of the PEER probabilistic framework equation as well as their integration for the Humboldt Bay Bridge testbed structure.
- Investigate seismic reliability assessment of non-ductile structures with degrading components.
Computational Reliability Tools for Design—4142002
Armen Der Kiureghian (UCB/F), Terje Haukaas (UCB/GS)
Develop, implement, and document reliability and response sensitivity methods in the OpenSees computational simulation framework. Apply to test-bed examples to assess reliability.
Data Management for OpenSees Simulations—4152002
Kincho Law (Stanford/F), Jun Peng (Stanford/PD)
This research project, in collaboration with researchers at PEER center, aims to develop a software platform that assists the application of performance-based earthquake engineering (PBEE) assessment and design methodologies. The project focuses on supporting testbed applications, data and project management, and archival capabilities. The objective is to provide a persistent storage for the analysis results for OpenSees, to support project management, and to archive testbed projects data. The data management system is to be designed to manage information related to seismic inputs, simulation models, and simulation results so that performance metric, demand parameters, and damage measures can be derived from the simulation results. Finally, an easy-to-use user interface is to be developed so that data can be queried via a web interface or an application program such as MATLAB.
Advanced Visualization for Seismic Performance—4182002
Mike Bailey (SDSC/I)
The objective of this project is to develop an advanced visualization toolkit for structural and geotechnical simulations. Visualization is necessary to investigate the response and performance of systems through simulation. The large models and varied ways of examining performance require new visual metaphors and methods of user interaction.
Integration of OpenSees and NEES—4192002
Steve Mahin (UCB/F), Andreas Schellenberg (UCB/GS)
OpenSees provides a rich set of highly capable modules that support the nonlinear static and dynamic analysis of complex structural systems. Its advanced, object-oriented, open-source format makes it ideally suited for hybrid simulation, where some portions of a structure are modeled numerically, while others are physically tested. Many of the advanced hybrid simulation applications being considered as part of NSF’s George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) and elsewhere require high performance analysis capabilities. Next-generation hybrid simulation techniques require an analysis framework able not only to carry out complex structural computations quickly, but also one that is able to operate transparently within a complex, real time computing and control environment. As such, OpenSees provides an ideal computing framework, and its capabilities will substantially advance the development of hybrid simulation as an effective tool for use by the earthquake engineering community.
Full-Scale Frame Test Validation of Simulation and Performance Demands—4202002
Greg Deierlein (Stanford/F), Paul Cordova (Stanford/GS)
This is a collaborative project between researchers at PEER and the National Center for Earthquake Engineering Research (NCREE) in Taiwan to utilize data from a full-scale frame test to validate structural simulation and performance models. Specific goals of the project are to:
- assess the accuracy of OpenSees simulation models through detailed comparisons with data from a full-scale moment frame test and complementary subassembly tests,
- collect and evaluate test data to develop relationships between engineering demand parameters and structural damage measures, and
- benchmark the seismic performance of a modern (IBC 2000 compliant) three-story building frame system.
Archiving and Web Dissemination of Geotechnical Data —Lifelines 2L02
Carl Stepp (COSMOS/I), Jennifer Swift (USC/PD), Jean Benoit (UNH/F), Loren Turner (Caltrans/I)
Develop a Pilot System for web-based dissemination of linked geotechnical database archives, develop and implementation plan, and plan and conduct a workshop to review and obtain input and consensus of the geotechnical community.