Methods Of Analysis

METHODS OF ANALYSIS

With the advancement in technology, analysis software used by engineers has become more sophisticated, enabling more realistic results to be achieved within a smaller amount of time. However, the more powerful and advanced the software is, the more costly it becomes. Through the knowledge invested in their engineers, Ettol has the capabilities to efficiently and realistically assess structural responses in different scenarios regardless of the software used. To demonstrate this a simple job was analysed using three different methods with three different tools. Tools employed for this problem were ANSYS for Finite Element Analysis (FEA), Space GASS for beam analysis, and a pen for hand calculations.

TASK:

  • To check a proposed cantilever handrail against actions outlined in AS 1657 – 2018
  • Handrail was to be tek-screwed onto a mounting plate, which is then welded onto girts
  • Handrail to withstand a load of 600N or 350 N/m acting outwards or downwards on the rail
  • Elastic deformation of the handrail is not to exceed 100mm
  • Plastic deformation of the handrail to be approximately 0mm

APPROACH:

  • Ettol was provided with drawings of the handrail configuration
  • To efficiently prepare the handrail for FEA it was first modelled in ANSYS Spaceclaim utilising easy to use 3D geometry features such as the Pull and Extend tools.
  • The model shown above was then exported to ANSYS Mechanical.
  • In ANSYS Mechanical, bonded contact connections were used between holes for the tek-screws and the mounting plate.
  • Welding between the mounting plate and girts were also scoped as bonded connections to accurately represent the handrail in action.
  • The ends of the girts were scoped as pinned supports.
  • The handrail, including the plates, were modelled in SPACE GASS as beam elements, with plates modelled as two parallel beam elements connected by dummy members (highlighted in orange below) to more accurately represent how the plate would behave.
  • For hand calculations the handrail itself was treated as a cantilever beam, with the adjoining plate treated as a continuous span beam with each pair of tek screws acting as a support.

OUTCOME:

  • Results for each of the three methods showed the handrail configuration to be adequate for the applicable loads, as shown in the diagrams below.
  • As this handrail configuration underwent load testing, we have the luxury of comparing real-world measured deflections with calculated ones. ANSYS modelling yielded a deflection 10% over the actual value. SPACE GASS gave a value 50% over, with hand calculations giving a highly unconservative value.
  • FEA through ANSYS Mechanical was most accurate, however it is a costly program that requires proper training and expertise to use. SPACE GASS was a close second and is significantly cheaper and easier to use. Hand calculations were least accurate due to assumptions required. However, it is the quickest method and can be used as sanity checks.
  • Each method has benefits and limitations, and each method can be used for this analysis, as long the engineer has appropriate knowledge and experience. At Ettol all our engineers are equipped with this knowledge which enables us to choose the appropriate method to meet any potential needs of the client.
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