OpenSees Examples Manual -- Structural Models & Anlyses

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

1. model dimensions and degrees-of-freedom
2. nodal coordinates
3. nodal constraints -- boundary conditions
4. nodal masses
5. elements and element connectivity
6. recorders for output

B. Define & apply gravity load

1. nodal or element load
2. static-analysis parameters (tolerances & load increments)
3. analyze
4. hold gravity loads constant
5. reset time to zero

C. Define and apply lateral load

1. load pattern (nodal loads for static analysis, support ground motion for earthquake)
2. 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
3. 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.

• OpenSees Example 1a. 2D Elastic Cantilever Column

OpenSees Example 1a. 2D Elastic Cantilever Column

Objectives overview of basic OpenSees input structure coordinates, boundary conditions, element connectivity, nodal masses, nodal loads, etc. two-node, one element

Models elastic elements

Analyses static pushover dynamic earthquake-input

• OpenSees Example 1b. Elastic Portal Frame

OpenSees Example 1b. Elastic Portal Frame

Objectives two element types distributed element loads

Models elastic elements

Analyses static pushover dynamic earthquake-input

Simple Nonlinear Analysis Examples

• OpenSees Example 2a. Elastic Cantilever Column with variables

OpenSees Example 2a. Elastic Cantilever Column with variables

Objectives introduce variable: define & use

Models elastic element

Analyses static pushover dynamic earthquake-input

• OpenSees Example 2b. Nonlinear Cantilever Column: Uniaxial Inelastic Section

OpenSees Example 2b. Nonlinear Cantilever Column: Uniaxial Inelastic Section

Objectives first example of nonlinear model, set nonlinearity at section level

Models nonlinearBeamColumn element uniaxial section

Analyses static pushover dynamic earthquake-input

• OpenSees Example 2c. Nonlinear Cantilever Column: Inelastic Uniaxial Materials in Fiber Section

OpenSees Example 2c. Nonlinear Cantilever Column: Inelastic Uniaxial Materials in Fiber Section

Objectives set nonlinearity at material level material stress-strain response is assembled into fiber section reinforced-concrete fiber section

Models nonlinearBeamColumn element uniaxial material fiber section (Reinforced-concrete fiber section)

Analyses static pushover dynamic earthquake-input

2D Structural Modeling & Analysis Examples

• OpenSees Example 3. Cantilever Column with units

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

Objectives units, defined and used (they will be used in all subsequent examples) separate model-building and analysis files introduce PDelta effects (or not)

Models elastic elements inelastic uniaxial section fiber section (Reinforced-concrete fiber section) Linear, PDelta or Corotational Transformation

Analyses static pushover dynamic earthquake-input

• OpenSees Example 4. Portal Frame

OpenSees Example 4. Portal Frame

Objectives 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)

Models elastic elements inelastic uniaxial section inelastic fiber section (Reinforced-concrete fiber section)

Analyses 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)

• OpenSees Example 5. 2D Frame, 3-story 3-bay, Reinforced-Concrete Section & Steel W-Section

OpenSees Example 5. 2D Frame, 3-story 3-bay, Reinforced-Concrete Section & Steel W-Section

Objectives 2D frame of fixed geometry: 3-story, 3-bay nodes and elements are defined manually, one by one

Models Reinforced-Concrete Section Steel W-Section elastic uniaxial section inelastic uniaxial section inelastic fiber section

Analyses 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)

• OpenSees Example 6. generic 2D Frame, N-story N-bay, Reinforced-Concrete Section & Steel W-Section

OpenSees Example 6. generic 2D Frame, N-story N-bay, Reinforced-Concrete Section & Steel W-Section

Objectives 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

Models Reinforced-Concrete Section Steel W-Section elastic uniaxial section inelastic uniaxial section inelastic fiber section

Analyses 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)

3D Structural Modeling & Analysis Examples

• OpenSees Example 7. 3D Frame, 3-story 3-bayX 3-bayZ, Reinforced-Concrete Section & Steel W-Section

OpenSees Example 7. 3D Frame, 3-story 3-bayX 3-bayZ, Reinforced-Concrete Section & Steel W-Section

Objectives 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

Models Reinforced-Concrete Section Steel W-Section Elastic or Fiber Section option is a variable within one input file rigid diaphragm

Analyses 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)

• OpenSees Example 8. generic 3D Frame, NStory NBayX NBayZ, Reinforced-Concrete Section & Steel W-Section

OpenSees Example 8. generic 3D Frame, NStory NBayX NBayZ, Reinforced-Concrete Section & Steel W-Section

Objectives 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

Models Reinforced-Concrete Section Steel W-Section Elastic or Fiber Section option is a variable within one input file optional rigid diaphragm

Analyses 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)

Section Modeling And Analysis Examples

• OpenSees Example 9. Build & Analyze a Section Example

OpenSees Example 9. Build & Analyze a Section Example

Objectives defined section using uniaxial behavior (define moment-curvature curve) or define section using uniaxial materials (define stress curve) in fiber section

Models 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

Analyses 2D static unidirectional moment-curvature analysis 3D static unidirectional moment-curvature analysis

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