Moment Resistant Frame
Table of Contents
- Introduction
1.2 Moment Resistant Frame
- Experimental Specimen Specifications
2.1 Geometric Properties
2.2 Material Properties
2.3 Experiment Loading Systems
2.4 Result of Experiment Test
- Finite Element Modeling (ANSYS APDL)
- Overview of ANSYS APDL
- Modeling (Step-by-Step)
- Results Comparison
4.1 Quantitative Data
- Conclusion
1. Introduction
This report presents the validation process of a Finite Element (FE) model developed to simulate the structural behavior of a Moment Resistant Frame (MRF). The objective is to verify the accuracy of the numerical model by comparing its response with experimental data obtained from laboratory testing. The validation focuses on key structural response parameters, including load capacity and lateral displacement behavior.
1.2 Moment Resistant Frame
Moment Resistant Frames are primary lateral force-resisting systems characterized by rigid connections between beams and columns. This system relies on the flexural stiffness and strength of the members to resist lateral loads. Unlike shear wall systems, MRFs provide greater architectural flexibility, though they may require deeper sections or heavier steel profiles to control lateral drift. The behavior of these frames under pushover or cyclic loading is critical for assessing structural ductility and energy dissipation capacity.
2. Experimental Specimen Specifications
To perform model validation, the study titled “Pushover Analysis of Steel Frame” by Dr. P. Eswaramoorthi et al. was selected as the reference laboratory investigation. This study provides reliable experimental data for a frame subjected to lateral pushover loading.
The specimen represents a frame structure with the following characteristics:
- Overall Dimensions: 920 mm (width) × 1050 mm (height).
- Section Profile: The beams and columns are constructed using a box section of 100 mm × 50 mm × 4 mm.
2.2 Material Properties
Based on the reference article, the structural steel properties are defined by standard industrial steel specifications consistent with the box section profiles utilized in the laboratory frame. (Note: These values should be input into the APDL material model as defined in the source paper).
2.3 Experiment Loading Systems
The frame is supported by a Fixed Bottom condition. Lateral load is applied at the top corner of the frame using a hydraulic actuator, performing a Pushover Analysis to capture the full force-displacement capacity curve of the structure.
2.4 Result of Experiment Test
The key performance characteristic of the Moment Resistant Frame, as determined by the control procedures in the source study, is the Capacity Curve (Lateral Force versus Top Displacement). This curve highlights the transition from elastic behavior to the yield point and ultimate load-carrying capacity of the frame.
Figure 2: Experiment Loading Systems
3. Finite Element Modeling (ANSYS APDL)
3.1 Overview of ANSYS APDL
ANSYS Parametric Design Language (APDL) is a powerful scripting language used to automate the finite element analysis process. Unlike the standard GUI, APDL allows for high-precision parametric modeling, which is essential for structural validation. It offers advanced capabilities for defining complex geometries, material behaviors, and loading conditions, ensuring that the numerical model accurately represents the experimental setup.
Advantages of using APDL Scripting:
• Automation: Enables seamless iteration of geometry, mesh density, and boundary conditions, supporting complex parametric studies and optimization through scripting.
• Flexibility: Offers precise control over material nonlinearities, advanced contact elements, and custom loading protocols.
Repeatability: Ensures that modeling steps are documented and•
reproducible, reducing human error and crucial for validation studies.
Figure 2: Modeling Experimental Specimen in ANSYS
- Modeling (Step-by-Step)
Step by Step modeling Moment Resistant Frame in ANSYS
| Step | Description’s | |
| 1: Element For Column, Beam | Beam 189 | |
| 2:Material For Column, Beam | Material 1 Define Multilinear Material[1] | |
| 3:Modeling | Line Method | |
| 4:Meshing | Quad Mapped | |
| 5:Load, Constraint and Analysis Type | Nonlinear static Analysis by Displacement Control | |
| 6:Result | Plot and Capacity Curve |
Figure 2: Plot Result after Analysis
4. Results Comparison
4.1 Quantitative Data
Figure 3: Load-Displacement Curve Comparison Graph
The comparison between the experimental and numerical results indicates that the FE model captures the overall structural response with satisfactory accuracy.
| Comparison Parameter | Experimental | FEA Result | Error[2] |
| Result | (ANSYS) | (%) | |
| Peak Load (N) | 43500 | 41366 | 4.1 % |
Figure 2: Comparison Between FEM and TEST
The load-displacement trend, peak resistance, and deformation characteristics should be evaluated together to determine the validity of the model.
If required, the percentage error may be computed using:
A low error percentage suggests that the selected element formulation, material models, and boundary conditions are appropriate for representing the tested specimen.
5. Conclusion
The numerical results obtained from the ANSYS APDL model show good agreement with the experimental data. The minor discrepancy in the results validates the reliability of the modeling methodology, confirming that the FE model can be effectively used for further parametric studies.
[1] For More Information See “Define MATERIAL in ANSYS” Tutorial Video
| Error (%) = | ∣Experimental Result −FEA Result∣ | × | 100 |
| Experimental Result |
