Introduction
The following examples are listed in order of simplicity.
NOTE: gravity analysis is always included as part of the model building
Process
Each example script does the following:
A. Build the model
- model dimensions and degrees-of-freedom
- nodal coordinates
- nodal constraints -- boundary conditions
- nodal masses
- elements and element connectivity
- recorders for output
B. Define & apply gravity load
- nodal or element load
- static-analysis parameters (tolerances & load increments)
- analyze
- hold gravity loads constant
- reset time to zero
C. Define and apply lateral load
- load pattern (nodal loads for static analysis, support ground motion for earthquake)
- lateral-analysis parameters (tolerances & displacement/time increments)
- Static Lateral-Load Analysis
- define the displacement increments and displacement path
- Dynamic Lateral-Load Analysis
- define the input motion and all associated parameters, such as scaling and input type
- define analysis duration and time increment
- define damping
- analyze
Introductory Examples
The objective of Example 1a and Example 1b is to give an overview of input-file format in OpenSees using simple scripts.
These scripts do not take advantage of the Tcl scripting capabilities shown in the later examples. However, they do provide starting a place where the input file is similar to that of more familiar Finite-Element Analysis software. Subsequent examples should be used as the basis for user input files.
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Objectives
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- overview of basic OpenSees input structure
- coordinates, boundary conditions, element connectivity, nodal masses, nodal loads, etc.
- two-node, one element
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Analyses
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- static pushover
- dynamic earthquake-input
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Objectives
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- two element types
- distributed element loads
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Analyses
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- static pushover
- dynamic earthquake-input
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Simple Nonlinear Analysis Examples
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Objectives
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- introduce variable: define & use
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Analyses
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- static pushover
- dynamic earthquake-input
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Objectives
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- first example of nonlinear model, set nonlinearity at section level
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Models
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- nonlinearBeamColumn element
- uniaxial section
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Analyses
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- static pushover
- dynamic earthquake-input
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Objectives
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- set nonlinearity at material level
- material stress-strain response is assembled into fiber section
- reinforced-concrete fiber section
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Models
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- nonlinearBeamColumn element
- uniaxial material
- fiber section (Reinforced-concrete fiber section)
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Analyses
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- static pushover
- dynamic earthquake-input
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2D Structural Modeling & Analysis Examples
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These examples take advantage of the Tcl scripting language starting from simple variable substitutions in the initial examples, to the more advanced techniques of array management and logical expressions (if-then statements).
OpenSees Example 3. Cantilever Column with units
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Objectives
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- units, defined and used (they will be used in all subsequent examples)
- separate model-building and analysis files
- introduce PDelta effects (or not)
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Models
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- elastic elements
- inelastic uniaxial section
- fiber section (Reinforced-concrete fiber section)
- Linear, PDelta or Corotational Transformation
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Analyses
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- static pushover
- dynamic earthquake-input
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Objectives
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- use previously-defined procedures to simplify input
- introduce more analysis types
- introduce procedure to read database input motion files (data with text in first lines)
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Models
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- elastic elements
- inelastic uniaxial section
- inelastic fiber section (Reinforced-concrete fiber section)
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Analyses
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- static reversed cyclic analysis
- dynamic sine-wave input analysis (uniform excitation)
- dynamic earthquake-input analysis (uniform excitation)
- dynamic sine-wave input analysis (multiple-support excitation)
- dynamic earthquake-input analysis (multiple-support excitation)
- dynamic bidirectional earthquake-input analysis (uniform excitation)
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Objectives
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- 2D frame of fixed geometry: 3-story, 3-bay
- nodes and elements are defined manually, one by one
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Models
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- Reinforced-Concrete Section
- Steel W-Section
- elastic uniaxial section
- inelastic uniaxial section
- inelastic fiber section
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Analyses
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- static reversed cyclic analysis
- dynamic sine-wave input analysis (uniform excitation)
- dynamic earthquake-input analysis (uniform excitation)
- dynamic sine-wave input analysis (multiple-support excitation)
- dynamic earthquake-input analysis (multiple-support excitation)
- dynamic bidirectional earthquake-input analysis (uniform excitation)
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Objectives
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- 2D frame geometry of variable geometry ( # stories and # bays are variables)
- node and element definition is automated
- use previously-defined procedures to view model node numbers and elements, deformed shape, and displacement history, in 2D
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Models
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- Reinforced-Concrete Section
- Steel W-Section
- elastic uniaxial section
- inelastic uniaxial section
- inelastic fiber section
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Analyses
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- static reversed cyclic analysis
- dynamic sine-wave input analysis (uniform excitation)
- dynamic earthquake-input analysis (uniform excitation)
- dynamic sine-wave input analysis (multiple-support excitation)
- dynamic earthquake-input analysis (multiple-support excitation)
- dynamic bidirectional earthquake-input analysis (uniform excitation)
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3D Structural Modeling & Analysis Examples
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Objectives
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- 3D frame of fixed geometry
- nodes and elements are manually manually, one by one
- introduce rigid floor diaphragm
- use previously-defined procedures to view model node numbers and elements, deformed shape, and displacement history, in 3D
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Models
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- Reinforced-Concrete Section
- Steel W-Section
- Elastic or Fiber Section option is a variable within one input file
- rigid diaphragm
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Analyses
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- static reversed cyclic analysis
- dynamic sine-wave input analysis (uniform excitation)
- dynamic earthquake-input analysis (uniform excitation)
- dynamic sine-wave input analysis (multiple-support excitation)
- dynamic earthquake-input analysis (multiple-support excitation)
- dynamic bidirectional earthquake-input analysis (uniform excitation)
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Objectives
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- 3D frame geometry of variable geometry ( # stories and # bays in X and Z are variables)
- node and element definition is automated
- introduce user-input interface, the user is given the option as to what to view in model
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Models
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- Reinforced-Concrete Section
- Steel W-Section
- Elastic or Fiber Section option is a variable within one input file
- optional rigid diaphragm
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Analyses
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- static reversed cyclic analysis
- dynamic sine-wave input analysis (uniform excitation)
- dynamic earthquake-input analysis (uniform excitation)
- dynamic sine-wave input analysis (multiple-support excitation)
- dynamic earthquake-input analysis (multiple-support excitation)
- dynamic bidirectional earthquake-input analysis (uniform excitation)
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Section Modeling And Analysis Examples
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Objectives
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- defined section using uniaxial behavior (define moment-curvature curve) or
- define section using uniaxial materials (define stress curve) in fiber section
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Models
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- Uniaxial Nonlinear section
- Fiber Steel W-section
- Fiber RC symmetric rectangular unconfined-concrete section
- Fiber RC symmetric rectangular unconfined & confined-concrete section
- Fiber RC generalized rectangular section
- Fiber RC generalized circular section
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Analyses
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- 2D static unidirectional moment-curvature analysis
- 3D static unidirectional moment-curvature analysis
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