What is OpenSees
OpenSees is an open source object-oriented software
framework written in C++ programming language for static and dynamic, linear
and nonlinear finite element (FE) analysis of structural and/or geotechnical
systems. This framework has been under development by the Pacific Earthquake
Engineering Research Center (PEER)
since 1997 through the National Science Foundation (NSF) engineering and
education centers program. OpenSees provides capabilities for response,
response sensitivity and reliability analyses of structural, geotechnical and
soil-foundation-structure interaction (SFSI) systems.
DDM-based FE Response
Sensitivity
Direct differentiation method (DDM) is an
algorithm for computing the “exact” or consistent sensitivities of the
computationally simulated structural response to constitutive material
parameters and discrete loading parameters. It consists of differentiating
exactly (consistently) the finite element numerical scheme (including the
material constitutive law integration scheme) with respect to the sensitivity
parameters. The DDM-bases response sensitivity analysis is enhanced by UCSD Team for
structural and/or geotechnical systems.
The DDM-based FE response sensitivity
analysis can be applied to:
o
Simplified probabilistic response analysis
o
Finite element model updating
o
Structural reliability analysis.
o
Study of the relative importance of structural parameters.
o
Structural identification.
o
Structural optimization
|
Download the last version of the DDM-bases
response sensitivity analysis in OpenSees (you may
need to download OpenSees 2.2.0)
1. User’s manual 2. Examples (I II III
IV) 3.
References for the examples (I II ) |
Computational Reliability
The
computational reliability combines FE modeling and seismic response analysis of
structural or soil-foundation-structure interaction (SFSI) systems with the
state-of-the-art most advanced numerical/computational methods in sensitivity
and reliability analysis. References (I II)
The
purpose of computational reliability is:
o Modeling and quantifying the uncertainties
and the propagation of the uncertainties, which characterize the structural or
SFSI systems, their physical and mathematical models, and their loading
environment.
o
Integrating mechanics, probability theory, and structural engineering to
analyze, estimate, and evaluate the performance of structural or SFSI systems.
o Probabilistic description of
structural response: Probabilistic response analysis.
o Computation of the probability
that the structure will exceed each and any of its potential limit-states
(serviceability or ultimate): Reliability analysis.
Numerical Optimization
In civil Engineering, nonlinear FE method is a
powerful tool to model the structural and geotechnical systems and simulate
their responses under different loading conditions. In addition, numerical
optimization is commonly used in many engineering applications, such as
structural reliability analysis, linear and nonlinear FE model updating,
structural identification and structural optimization.
Currently, a new software framework integrating SNOPT
(Sparse Nonlinear Optimization software package) and OpenSees is under
development and being applied to various optimization problems in civil
engineering. The newly developed OpenSees-SNOPT
framework has three distinguishing features:
(1) It is extremely powerful in solving the
optimization problems in civil engineering due to the powerful capacity of
OpenSees in modeling nonlinear structural/geotechnical systems and that of
SNOPT in solving large scale nonlinear optimization problems.
(2) The integration of OpenSees and SNOPT is
efficient. Taking advantage of the object-oriented framework of OpenSees, SNOPT
is wrapped into an optimization class and integrated into OpenSees framework,
which allow the efficient communication between SNOPT and OpenSees.
(3) OpenSees-SNOPT can be used to solve a
wide range of optimization problems in civil engineering field. Users are
allowed to write their own objective and constraint functions, by taking
advantage of the flexible input and output of OpenSees, thus greatly improving
the flexibility and application range of OpenSees-SNOPT.
The usages of this framework are illustrated through
three application
examples, i.e., a structural optimization problem, a reliability analysis
of soil-structure interaction system, and a soil model updating problem.