OpenSees Examples Manual -- Structural Models & Anlyses

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Introduction

The following examples are listed in order of simplicity.

NOTE: gravity analysis is always included as part of the model building

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)
  3. damping for dynamic analysis
  4. 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

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
Objectives
  • two element types
  • distributed element loads
Models
  • elastic elements
Analyses
  • static pushover
  • dynamic earthquake-input



OpenSees Examples -- Simple Nonlinear Analysis Examples
Objectives
  • introduce variable: define & use
Models
  • elastic element
Analyses
  • static pushover
  • dynamic earthquake-input
Objectives
  • first example of nonlinear model, set nonlinearity at section level
Models
  • nonlinearBeamColumn element
  • uniaxial section
Analyses
  • static pushover
  • dynamic earthquake-input
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




OpenSees Examples -- 2D Structural Modelling & Analysis Examples
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
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)
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)
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)




OpenSees Examples -- 3D Structural Modelling & Analysis Examples
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)
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)




OpenSees Examples -- Section Modelling And Analysis Examples
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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