OpenSees - The Open System for Earthquake Engineering Simulation
Earthquake engineering has long been hampered by limitations of available computational procedures. The most familiar and commonly used computer tools were developed in the 1970s and 1980s, and are limited by simplifications and approximations that were necessary at the time. Furthermore, different computer codes are required for different parts of the earthquake engineering problem, from seismic hazard analysis, through geotechnical site response, through soil-structure interaction, to structural response. New computer simulation tools are necessary to integrate the best knowledge from all the disciplines so that more effective engineering can be practiced.
A centerpiece of PEER’s program is new research on simulation models and computational methods to assess the performance of structural and geotechnical systems. Breaking the barriers of traditional methods and software development protocols, PEER has embarked on a completely new approach in the earthquake engineering community by developing an open-source, object-oriented software framework. OpenSees is a collection of modules to facilitate the implementation of models and simulation procedures for structural and geotechnical earthquake engineering. By shared development using well-designed software interfaces, the open-source approach has effected collaboration among a substantial community of developers and users within and outside of PEER. Unique among software for earthquake engineering, OpenSees allows integration of models of structures and soils to investigate challenging problems in soil-structure-foundation interaction. In addition to improved models for reinforced concrete structures, shallow and deep foundations, and liquefiable soils, OpenSees is designed to take advantage of the latest developments in databases, reliability methods, scientific visualization, and high-end computing.
PEER has provided substantial support to the community by sponsoring three workshops on OpenSees, attended by more than 100 researchers and engineers. Over 300 developers and users share insights and are kept apprised of the latest developments through on-line collaboration tools. The OpenSees website http://opensees.berkeley.edu provides the source code, documentation, examples, user group links, and information about the development roadmap for the software.
The OpenSees model of Humboldt Bay Bridge including foundations and soils is used to study the effects of soil liquefaction and permanent displacements on the performance of the bridge in an earthquake.
OpenSees is used to simulate the nonlinear response of simple structures located at25,000 points on a 10x10 km region subjected to a M=6 strike-slip fault. Thecontourplots show the maximum displacement of structures with a 1 second vibration periodanddifferent ductility levels. The strike-slip produces regions in which fault-normalresponseis dominant and other, smaller regions, in which fault-parallel response is dominant.