Optimisation of load carrying capacity of I-beams subject to buckling constraint using MATLAB and ANSYS

• Main Author: Tan, Wei Zhe
• Other Authors: Sellakkutti Rajendran
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; ANSYS; FEA
• Online Access: https://hdl.handle.net/10356/177265
• Institution: Nanyang Technological University

The I-beam, a foundational element in structural engineering, plays a critical role in loadbearing structures. In an I-beam, the horizontal section is often referred to as the "flange", while the vertical section is called the "web". As the I-beams are widely used in structural engineering, an analysis to understand the failure load is essential in the design of I-beams. This Final Year Project (FYP) focuses on a detailed analysis of I-beams using the ANSYS APDL platform, with a primary focus on optimising the cross-section of the I-beam to avoid buckling failure and yield failure. The I-beam dimensions such as flange width, are varied to increase the failure load it can withstand. Finite element method is a powerful numerical tool for determining stress levels. This FYP uses the Finite Element Analysis (FEA) software, ANSYS Mechanical APDL to obtain the critical buckling load and yield load. Firstly, a series of finite element models are created by varying the design parameters, and the yield load and the critical buckling load are computed for each of the models. The results are plotted against the parameter values and the maximum failure load is obtained from the plot. For this purpose, four parameters are varied, viz., flange width, flange thickness, web width and web thickness. The above process of finding the maximum failure load is manual and time-consuming. Next, a code is written in MATLAB to automate the whole optimisation process described above. The code employs the collaborative use of MATLAB and ANSYS APDL for solving the optimisation problem, with the goal of enhancing the I-beam's failure load. In order to avoid the buckling failure happening before the yield failure, an additional constraint of (critical buckling load / yield load) > 1 is introduced in the optimisation process. This ratio (critical buckling load / yield load) is defined to be the safety factor against buckling failure. The result from the analyses shows that for different values of safety factor, critical buckling load stays almost constant and only the yield load changes. The higher the safety factor, the lower the yield load of the optimised beam.