This paper is a bridge analysis using Ansys mechanical Apdl. It's a solid mechanics assignment that's solves different tasks regarding the theme.
Table of Contents
TASK 1
Create and present FE model of the bridge
1.10 Creation of the Finite Element model.
Discuss real constants, material model and element type chosen for the FE analysis
Task 1.12
Justification of the element type selected
Task 1.13
Present meshed FE model and discuss the procedures used for it
Task 1.14
Explain the boundary conditions used for the modal analysis
Task 1.15
Present your post processing results in textual and graphical form
Task 1.16
Discuss the solver used for this analysis
Task 1.17
Refine the FE model with more elements and conduct analysis
Task 1.18
Presenting the post processing results in textual and graphical form for the no of element division of 100 for the refined analysis and compare it with the results of previous model.
Discussion and Conclusion
References
Objectives and Topics
The primary objective of this work is to perform a Finite Element (FE) modal analysis on a clamped-clamped bridge structure using ANSYS APDL. The study aims to determine the natural resonant frequencies and mode shapes, while evaluating how mesh refinement—comparing a division of 10 elements against 100 elements—impacts the accuracy of the structural simulation.
- Construction of a 1D Finite Element bridge model.
- Selection and justification of appropriate element types and material properties.
- Application of specific boundary conditions for modal analysis.
- Comparative performance analysis of meshing densities and eigensolvers.
Excerpt from the Book
Justification of the element type selected
In this clamped-clamped bridge, the element selected for this is the 3 node 189 element. This element has the properties required for the bridge which made it the element to be selected. Therefore, this 3D beam is a uniaxial element which has tension, compression and bending capabilities. In any modal analysis, high frequencies and deflections are basically analysed whereby making such element to be in need of good quality bending capabilities.
This beam 3 only performs when it is symmetric cross section which does not compute shear stresses in the beam. This indication is because of the required gross section properties which the element relies on, those properties are moment of inertia, area and height.
In each node of the element is seen three degree of freedom DOF, these degree of freedom is translation in the x and y direction and rotates about the nodal z axis. The beam element can have any cross sectional shape in which the moment of inertia can be computed on.
In this clamped-clamped bridge, the section of the bridge which comprise of the breadth and the height was given which is been inputted to obtain the full section area of the bridge. The breadth which is 25micro meter and the height which is 0.6micro meter was assigned in the B and H box in the section which automatically gave us the sectional area of the beam as shown in the figure above (Figure 11).
This is the justification ensured by me for selecting the 3 node 189 in the clamped clamped bridge analysis.
Summary of Chapters
TASK 1: Describes the initial creation of the bridge FE model, including the setting of keypoints and geometry.
1.10 Creation of the Finite Element model.: Details the specific steps for plotting keypoints and joining lines within the ANSYS environment.
Discuss real constants, material model and element type chosen for the FE analysis: Explains the selection of the beam element type and the input of material properties such as modulus of elasticity and Poisson’s ratio.
Task 1.12: Provides the technical justification for using the 3-node 189 element based on its bending and tension-compression capabilities.
Task 1.13: Outlines the procedure for meshing the FE model with a division factor of 10.
Task 1.14: Covers the definition of boundary conditions and the application of modal analysis settings to extract natural frequencies.
Task 1.15: Presents the initial post-processing results, showing the first three resonant frequencies and their corresponding mode shapes.
Task 1.16: Discusses the choice of eigensolver (Block Lanczos vs. PCG Lanczos) and its efficiency based on problem size.
Task 1.17: Demonstrates the refinement of the mesh by increasing the element division factor from 10 to 100.
Task 1.18: Compares the refined results with the previous coarse mesh data to assess accuracy improvements.
Discussion and Conclusion: Summarizes the findings, highlighting the importance of modal analysis in avoiding structural failure due to resonance.
References: Lists the academic and technical resources utilized for this analysis.
Keywords
Finite Element Method, ANSYS, Modal Analysis, Bridge, Resonant Frequency, Mode Shapes, Meshing, Element Division, Clamped-Clamped, Structural Analysis, PCG Lanczos, Block Lanczos, Displacement, DOF, Resonance
Frequently Asked Questions
What is the core focus of this publication?
This publication documents the process of performing a modal analysis on a bridge structure using the Finite Element Method within the ANSYS APDL software.
What are the primary themes discussed?
The main themes include FE model creation, mesh generation, parameter selection (elements and material properties), and the comparative study of result accuracy based on mesh refinement.
What is the main goal or research question?
The goal is to determine the natural resonant frequencies of a clamped-clamped bridge and to evaluate how changing the density of the computational mesh affects the precision of those frequency calculations.
Which scientific methods are applied?
The author employs numerical simulation via Finite Element Analysis (FEA), specifically utilizing the ANSYS APDL software suite to discretize the bridge into elements and solve for structural modes.
What is covered in the main section?
The main section covers the sequential procedural steps for modelling, defining boundary conditions, conducting modal analysis with different mesh densities, and interpreting the output data.
Which keywords best characterize this work?
Key terms include Finite Element Method, Modal Analysis, Resonant Frequency, Mesh Refinement, and Clamped-Clamped Bridge structure.
Why is mesh refinement significant in this study?
Mesh refinement is critical because it directly influences result accuracy; the study highlights that while a coarse mesh may yield inaccurate results, an excessively fine mesh consumes unnecessary computational resources.
What is the significance of the PCG Lanczos solver comparison?
The author discusses this to demonstrate that selecting the correct eigensolver is essential for balancing computational speed with the number of modes requested in large structural analyses.
- Quote paper
- Orakwelu Nzube Cliff (Author), 2014, Bridge analysis using Ansys mechanical Apdl. Solid mechanics assignment, Munich, GRIN Verlag, https://www.grin.com/document/976471
