OpenSees Example 9. Build & Analyze a Section Example
Introduction
For the case of the uniaxial section, moment-curvature and axial force-deformation curves are defined independently, and numerically.
For the case of the fiber sections (steel and RC), uniaxial materials are defined numerically (stress-strain relationship) and are combined into a fiber section where moment-curvature and axial force-deformation characteristics and their interaction are calculated computationally.
Input
Model Building
- 2D vs. 3D
- While this distinction does not affect the section definition itself, it affects the degree-of-freedom associated with moment and curvature in the subsequent analysis.
- There are two differences between the two models:
- 1. The space defined with the model command (# Define the model builder, ndm=#dimension, ndf=#dofs)
- 2D
- model BasicBuilder -ndm 2 -ndf 3;
- 3D
- model BasicBuilder -ndm 3 -ndf 6;
- 2. In the 3D model, torsional stiffness needs to be aggregated to the section
- 1. The space defined with the model command (# Define the model builder, ndm=#dimension, ndf=#dofs)
Uniaxial Section
Files Notes - Flexure and axial behavior are uncoupled in this type of section
Fiber Section: AISC Standard W Section
Files Notes - Coupled biaxial flexure and axial behavior
Fiber Section: Reinforced Concrete Section -- Rectangular Symmetric Section, Unconfined Concrete
Files Notes - Coupled biaxial flexure and axial behavior
Fiber Section: Reinforced Concrete Section -- Rectangular Symmetric Section, Confined Concrete Core
Files Notes - Coupled biaxial flexure and axial behavior
Fiber Section: Reinforced Concrete Section -- Rectangular Section
Files Notes - Coupled biaxial flexure and axial behavior
- generic rectangular section
Fiber Section: Reinforced Concrete Section -- Circular Section, Confined Core
Files Notes - Coupled biaxial flexure and axial behavior
- generic circular section
Lateral-Load Analysis
The following tasks are performed in the analysis
- define lateral-load parameters
- analyze
Static
Static Pushover
Files
Notes
- One-directional monotonic displacement-controlled static loading
Static Reversed Cyclic
Files
Notes
- One-directional displacement-controlled static loading
- Displacement cycles are imposed in positive and negative direction
Dynamic EQ Ground Motion
Dynamic Uniform Sine-Wave Ground Motion
Files
Notes
- Sine-wave acceleration input
- Same acceleration input at all nodes restrained in specified direction
Dynamic Uniform Earthquake Ground Motion (typical)
Files
- Ex8.genericFrame3D.analyze.Dynamic.EQ.Uniform.tcl
- LibAnalysisDynamicParameters.tcl
- ReadSMDFile.tcl
- H-E12140.AT2
Notes
- Earthquake (from file) acceleration input
- Same acceleration input at all nodes restrained in specified direction
Dynamic Multiple-Support Sine-Wave Ground Motion
Files
- Ex8.genericFrame3D.analyze.Dynamic.sine.multipleSupport.tcl (this file may need to be corrected for displacement input)
- LibAnalysisDynamicParameters.tcl
Notes
- Sine-wave displacement input
- Different displacements are specified at particular nodes in specified directions
Dynamic Multiple-Support Earthquake Ground Motion
Files
- Ex8.genericFrame3D.analyze.Dynamic.EQ.multipleSupport.tcl (this file needs to be corrected for displacement input)
- LibAnalysisDynamicParameters.tcl
- ReadSMDFileDisp.tcl
- H-E12140.DT2 (Displacement recording)
Notes
- Earthquake (from file) displacement input
- Different displacements are specified at particular nodes in specified directions
Dynamic Bidirectional Earthquake Ground Motion (typical)
Files
- Ex8.genericFrame3D.analyze.Dynamic.EQ.bidirect.tcl
- LibAnalysisDynamicParameters.tcl
- ReadSMDFile.tcl (need to modify ReadSMDFile.tcl for displacement data)
- H-E12140.AT2
- H-E01140.AT2 (acceleration recording in perpendicular direction)
Notes
- Earthquake (from file) acceleration input
- Different ground motion in two directions
- Same acceleration input at all nodes restrained in specified direction
Run
The model and analysis combinations for this example are numerous. The following are an small subset, for demonstration purposes:
- To run W-Section Model, Static Pushover Analysis:
puts " -------------Elastic Model -------------" puts " -------------Static Pushover Analysis -------------" source Ex8.genericFrame3D.build.Wsec.tcl source Ex8.genericFrame3D.analyze.Static.Push.tcl
- To run RC Model, Uniform Earthquake Excitation
puts " -------------Uniaxial Inelastic Section, Nonlinear Model -------------" puts " -------------Uniform Earthquake Excitation -------------" source Ex8.genericFrame3D.build.RCsec.tcl source Ex8.genericFrame3D.analyze.Dynamic.EQ.Uniform.tcl
Notes
In this example, the following items are variables:
- Number of stories in Y direction
- Number of bays in X direction
- Number of bays in Z direction
- Elastic/Fiber Section
- Display: none/node numbering/deformed shape/mode shape (can choose which mode) (variable display scaling factor for both the deformed shape and the mode shape, this scaling factor is dependent on the user choice)
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