Finite Element Analysis or FEA is a numerical method used in engineering to solve complex problems by dividing a system or structure into smaller, simpler, and more manageable parts called finite elements. FEA involves the application of mathematical algorithms and computer software to simulate and analyze the behavior of a system under various conditions.
In FEA, the behavior of a system or structure is modeled using a finite element mesh, which is a set of interconnected nodes and elements that represent the physical geometry and material properties of the system. The mesh is then subjected to various physical forces and constraints, and the resulting stresses and deformations are calculated and analyzed.
For example, the analysis of slabs in buildings was traditionally done using approximate methods such as dividing the slab moments into middle strip and column strip moments leading to conservative designs. With the advent of modern Eurocodes and finite element analysis techniques, slabs started to be modelled using finite shell elements with more accurate representation of the bending stiffness (for both cracked and uncracked) leading to precise calculation of bending moments and deformations to design the slabs.
Figure 1: Floor slabs modeled using shell elements showing deformations
FEA is widely used in many areas of engineering, including mechanical, civil, aerospace, and biomedical engineering, to analyze and optimize the design of structures, components, and systems. It is a powerful tool that allows engineers to explore multiple design options and evaluate the performance of a system under various operating conditions before it is built or deployed.
Here are the top seven reasons why learning and using Finite Element Analysis (FEA) software for structural design can be beneficial:
FEA software uses numerical methods to simulate the behavior of structures, which enables more accurate predictions of how the structure will behave under different loading conditions. With FEA, engineers can take into account complex interactions between different components, such as the effects of stress concentrations and material nonlinearity. This allows for a more realistic representation of the actual performance of the structure. For example, the analysis for lateral torsional buckling for a U-frame type of structure (shown in figure below) is usually done using a simplified empirical approach as specified in EN1993-1-5 which results in earlier buckling failure. It does not accurately define the stiffness of the transverse girders in a U-frame deck. A finite element analysis of a U-framed deck with longitudinal and transverse plate girders modelled as thick shell elements allows to test the structure through a geometric nonlinear analysis to its ultimate buckling failure limit leading to a more accurate prediction of lateral torsional buckling failure.
Figure 2: Steel plate girder showing nonlinear buckling (Lateral torsion buckling) under applied loads
FEA software can help engineers optimize their designs by allowing them to analyze and compare multiple design options. With FEA, engineers can quickly test and evaluate different design configurations and make informed decisions on the best design solution. This leads to optimized structures that are efficient, safe, and meet the project requirements.
For example, for a footbridge of over 40m span running across a major highway, considering various loads such as dead, live and wind loads and considering various project management scenarios like cost and duration of delivery, it becomes important to analyse several design options including form or aesthetics, construction stage analysis, member designs, nonlinear creep and shrinkage effects and long term serviceability checks. Arriving at the most feasible economical option happens easily with the help of a finite element analysis software. In this case, having a through type truss bridge gives a more robust solution than having a plate girder bridge with a composite concrete deck. Even though the stiffness and economics of the composite steel girder bridge looked sounder than the truss bridge at a final stage condition but when performing a construction stage analysis, the temporary installation of plate girders posed stability issues along with the long term deflections of the composite girder bridge, which the truss bridge did not have a problem with. A finite element analysis software can perform these checks at a lightning speed as opposed to traditional spreadsheets.
Figure 3: Example of optimising for best design of footbridge for a use case: Steel through truss bridge vs composite steel plate girder bridge
[Image source: https://steelconstruction.info/images/7/70/Coalville_04.jpg
FEA software can reduce the time required to develop a new structure by simulating the behavior of the structure virtually. This reduces the need for physical prototypes and testing, which can be time-consuming and expensive. With FEA, engineers can quickly make design iterations and refine the structure before moving to the manufacturing stage, leading to shorter development cycles. For example in the above footbridge scenario, one could iterate several parameters in the design within minutes like sizes of the plates used in the plate girder, thickness of the concrete slab used in the composite plate girder, rolled steel section sizes used in the truss bridge, dimensions of the truss bridge and cross girder and plan bracing details.
FEA software can also lead to cost savings by identifying design flaws and weaknesses early in the design process. By testing and analyzing the structure virtually, engineers can identify potential problems and make design changes before manufacturing, which can reduce material waste and other costs associated with correcting errors.
FEA software can help engineers design structures that meet safety requirements by predicting how the structure will perform under different loading conditions. Engineers can identify potential failure modes and take corrective actions to ensure the structure meets safety standards. This leads to structures that are safe, reliable, and meet regulatory requirements.
For example, in order to design a bridge pier to resist seismic effects, its important to analyze the pier for a gradual orchestrated collapse instead of a sudden failure. A finite element analysis software is capable of doing advanced material nonlinear analysis like pushover analysis that simulates the formation of plastic hinges along the height of the pier under transverse loads. Thus, allowing the designer to build a safe structure.
Figure 4: Pushover Analysis during earthquake to analyze plastic hinge formation in a bridge pier
[Image source: https://www.midasbridge.com/en/blog/casestudy/concepts-of-plastic-hinging-and-pushover-analysis-with-midas-civil]
FEA software can help improve collaboration among design teams, project managers, and other stakeholders by providing a shared platform for design and analysis. This allows team members to share information, communicate design changes, and work together to achieve project goals. Modern day FEA software can import structural members from BIM tools like Revit or Tekla and convert them into frame or shell elements. Beams and columns from Revit Architectural model are imported as line elements in the analysis software and slabs/ walls are imported as shell elements. On further analysis and changes in member shapes within the FEA model, the updated version can be exported back into the architectural model such that the structural engineering changes reflect well with the architectural and mechanical, electrical and plumbing design. Similarly, a change in the architecture in the BIM model can automatically reflect a change in the structural analysis model like inserting a slab opening for a utility passage.
Figure 5: Collaboration between structural engineering FEA software with Building Information Modeling software
FEA software can help ensure compliance with industry standards and regulatory requirements by providing code checking and analysis capabilities. Engineers can ensure that the design meets the required design codes, such as AISC, Eurocode, or ASCE, and make necessary design changes to ensure compliance. In the below example at composite steel plate girder bridge is shown to be designed automatically using midas Civil using AASHTO LRFD code.
Figure 6: FEA software performing member design checks using American standards
In conclusion, FEA software is a powerful tool for structural design and analysis, offering benefits such as accurate predictions, design optimization, reduced development time, cost savings, improved safety, enhanced collaboration, and code compliance. With these benefits, engineers can design more efficient, reliable, and safe structures that meet project requirements and exceed client expectations.
#Finite Element Analysis (FEA)
#Structural design optimization
#Accurate structural simulation
