OpenSees Examples Manual -- Structural Models & Anlyses: Difference between revisions
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The following types of models are represented in these examples: | The following types of models are represented in these examples: | ||
;*Elastic | ;*<h2>Elastic</h2> | ||
: OpenSees [[Elastic Beam Column Element]] | : OpenSees [[Elastic Beam Column Element]] | ||
: The elastic, uncoupled, axial and flexural stiffnesses are defined at the element level | : The elastic, uncoupled, axial and flexural stiffnesses are defined at the element level | ||
: user specifies: E,I,A | : user specifies: E,I,A | ||
;*Inelastic Elements | ;*<h2>Inelastic Elements/<h2> | ||
: OpenSees [[Force-Based Beam-Column Element]] | : OpenSees [[Force-Based Beam-Column Element]] | ||
: Two types of sections | : Two types of sections | ||
::*Uniaxial Section | ::*<h3>Uniaxial Section</h3> | ||
::: The inelastic, uncoupled, axial and flexural stiffnesses are defined at the section level | ::: The inelastic, uncoupled, axial and flexural stiffnesses are defined at the section level | ||
::: The OpenSees [[Uniaxial Section]] Command is used | ::: The OpenSees [[Uniaxial Section]] Command is used | ||
Line 22: | Line 22: | ||
:::: Axial stiffness A | :::: Axial stiffness A | ||
:::: Section Moment-Curvature characteristics via the OpenSees [[UniaxialMaterial Command]] | :::: Section Moment-Curvature characteristics via the OpenSees [[UniaxialMaterial Command]] | ||
::*Fiber Section | ::*<h3>Fiber Section</h3> | ||
::: The section is broken down into fibers where uniaxial materials are defined independently. | ::: The section is broken down into fibers where uniaxial materials are defined independently. | ||
::: The program calculates the coupled flexural and axial stiffnesses/strength by integrating strains across the section | ::: The program calculates the coupled flexural and axial stiffnesses/strength by integrating strains across the section |
Revision as of 21:07, 11 November 2009
Introduction
The following examples are listed in order of simplicity.
NOTE: gravity analysis is always included as part of the model building
Models
The following types of models are represented in these examples:
Elastic
- OpenSees Elastic Beam Column Element
- The elastic, uncoupled, axial and flexural stiffnesses are defined at the element level
- user specifies: E,I,A
Inelastic Elements/
- OpenSees Force-Based Beam-Column Element
- Two types of sections
Uniaxial Section
- The inelastic, uncoupled, axial and flexural stiffnesses are defined at the section level
- The OpenSees Uniaxial Section Command is used
- User specifies:
- Axial stiffness A
- Section Moment-Curvature characteristics via the OpenSees UniaxialMaterial Command
Fiber Section
- The section is broken down into fibers where uniaxial materials are defined independently.
- The program calculates the coupled flexural and axial stiffnesses/strength by integrating strains across the section
- The OpenSees Fiber Section Command is used
- User specifies
- Stress-Strain characteristics via the OpenSees UniaxialMaterial Command for all number of materials
- Section geometry via series of Patches and Layers in the fiber section
- Two Section Geometries are presented
- *RC Rectangular Section
- *Standard AISC W section
Lateral Loads
The following types of lateral loads are represented in these examples:
Static Pushover
- Control node is located at the highest floor
- Lateral-load distribution is proportional the the mass distribution along the height of the building
- Static analysis
- Two types
Monotonic Pushover
- One-directional displacement-controlled static lateral loading
Reversed Cyclic Pushover
- One-directional displacement-controlled static lateral loading
- Displacement cycles are imposed in positive and negative direction
Time-Dependent Dynamic Loads
- Transient analysis
- Four types
Uniform Sine-Wave
- Sine-wave acceleration input
- Same acceleration input at all nodes restrained in specified direction
Multiple-Support Sine-Wave
- Sine-wave displacement input
- Different displacements are specified at particular nodes in specified directions
Uniform Earthquake
- Earthquake (from file) acceleration input
- Same acceleration input at all nodes restrained in specified direction
Multiple-Support Earthquake
- Earthquake (from file) displacement input
- Different displacements are specified at particular nodes in specified direction
Bidirectional Earthquake
- Different inputs are specified for two directions
- Same acceleration input at all nodes restrained in specified direction
Simulation 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
- Static Lateral-Load Analysis
- 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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Simple Nonlinear Analysis Examples
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2D Structural Modeling & Analysis Examples
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).
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3D Structural Modeling & Analysis Examples
A few items are new in 3D:
- Additional coordinates need to be considered in defining nodes
- Additional degrees of freedom need to be considered in defining the following:
- nodal constraints (boundary conditions)
- nodal masses
- nodal loads
- The transformation from local element/section coordinates to global system coordinates needs to be specified
- Element loads are specified in local coordinates
- Additional arguments are required for many elements (bending about local-y axis) properties
- Element/Section torsional stiffness needs to be considered
- Rigid floor diaphragms need be included for building models
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Section Modeling And Analysis Examples
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