OpenSees Features

WHY OPENSEES?

+ The library of materials, elements and analysis commands makes OpenSees a powerful tool for numerical simulation of nonlinear structural and geotechnical systems

+ The OpenSees library of components is ever-growing and at the leading edge of numerical-simulation models

+ The OpenSees interface is based on a command-driven scripting language which enables the user to create more-versatile input files.

+ OpenSees is not a black box, making it a useful educational tool for numerical modeling

+ You can create your own material, element or analysis tools and incorporate them into OpenSees

+ NEES is supporting integration of OpenSees as the simulation component of laboratory testing

MODELS:

+ linear & nonlinear structural and geotechnical models

SIMULATIONS:

+ static push-over analyses

+ static reversed-cyclic analyses

+ dynamic time-series analyses

+ uniform-support excitation

+ multi-support excitation

MODELING FEATURES:

MODEL-BUILDING CAPABILITIES:

ANALYSIS CAPABILITIES

RECORDER/OUTPUT CAPABILITIES

MODEL-BUILDING FEATURES:

UNIAXIAL MATERIALS:

MULTIDIMENSIONAL/nD MATERIALS:

Elastic Isotropic Material
J2 Plasticity Material
Plane Stress Material
Plate Fiber Material
Template Elasto-Plastic Material
FluidSolidPorousMaterial Material
PressureIndependMultiYield Material
PressureDependMultiYield Material

ELEMENTS:

SECTIONS:

ANALYSIS FEATURES:

Linear Equation Solvers -- provide the solution of the linear system of equations Ku = P. Each solver is tailored to a specific matrix topology.

Profile SPD -- Direct profile solver for symmetric positive definite matrices
Band General -- Direct solver for banded unsymmetric matrices
Band SPD -- Direct solver for banded symmetric positive definite matrices
Sparse General -- Direct solver for unsymmetric sparse matrices
Sparse Symmetric -- Direct solver for symmetric sparse matrices
UmfPack General -- Direct UmfPack solver for unsymmetric matrices
Full General -- Direct solver for unsymmetric dense matrices
Conjugate Gradient -- Iterative solver using the preconditioned conjugate gradient method

Eigenvalue Solvers -- provide the solution of the generalized eigenvalue problem Kv = MvL

Symmetric Arpack -- Arpack solver for symmetric matrices
Band Arpack -- Arpack solver for banded matrices

DOF Numberers -- number the degrees of freedom in the domain

Plain -- Uses the numbering provided by the user
RCM -- Renumbers the DOF to minimize the matrix band-width using the Reverse Cuthill-McKee algorithm

Static Integrators -- determine the next time step for an analysis

Load Control -- Specifies the incremental load factor to be applied to the loads in the domain
Displacement Control -- Specifies the incremental displacement at a specified DOF in the domain
Minimum Unbalanced Displacement Norm -- Specifies the incremental load factor such that the residual displacement norm in minimized
Arc Length -- Specifies the incremental arc-length of the load-displacement path

Transient Integrators -- determine the next time step for an analysis including inertial effects

Newmark -- The two parameter time-stepping method developed by Newmark
Hilbert-Hughes-Taylor -- The three parameter Hilbert-Hughes-Taylor time-stepping method
Central Difference -- Approximates velocity and acceleration by centered finite differences of displacement

Solution Algorithms -- Iterate from the last time step to the current

Linear Algorithm -- Uses the solution at the first iteration and continues
Newton Algorithm -- Uses the tangent at the current iteration to iterate to convergence
Modified Newton Algorithm -- Uses the tangent at the first iteration to iterate to convergence
Newton with Line Search Algorithm
Krylov-Newton Algorithm
BFGS Algorithm
Broyden Algorithm

Convergence Tests -- Accept the current state of the domain as being on the converged solution path

Norm Unbalance -- Specifies a tolerance on the norm of the unbalanced load at the current iteration
Norm Displacement Increment -- Specifies a tolerance on the norm of the displacement increments at the current iteration
Energy Increment -- Specifies a tolerance on the inner product of the unbalanced load and displacement increments at the current iteration
Relative Unbalance
Relative Displacement Increment
Relative Energy Increment

Constraint Handlers -- Handle the constraints defined on the domain

Plain Constraints -- Removes constrained degrees of freedom from the system of equations
Lagrange Multipliers -- Uses the method of Lagrange multipliers to enforce constraints
Penalty Method -- Uses penalty numbers to enforce constraints
Transformation Method -- Performs a condensation of constrained degrees of freedom

analysis Command -- defines what type of analysis is to be performed

Static Analysis -- solves the KU=R problem, without the mass or damping matrices.
Transient Analysis -- solves the time-dependent analysis. The time step in this type of analysis is constant. The time step in the output is also constant.
Variable Transient Analysis -- performs the same analysis type as the Transient Analysis object. The time step, however, is variable. This method is used when there are convergence problems with the Transient Analysis object at a peak or when the time step is too small. The time step in the output is also variable.