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 Tornado Loads / ASCE Hazards Tool

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Mark Miller's profile image
Mark Miller posted 06-14-2023 03:41 PM

Just getting into reviewing ASCE 7-22 which goes into effect for my area in December.  I note that within the standard they supply maps for category III building (1700 year MRI) and for category IV buildings (3000 year MRI). However I note when using the ASCE 7 Hazard Tool, the chart produced is for MRI’s of 1700, 10,000, 100,000 and up.

 

  1. Why is the 3000 year MRI which is required for category IV buildings not displayed as that would be one of the data points needed?
  2. How would you compute the 3000 MRI using the 1,700 and 10,000 vlaues….is that straight linear interpolation? Could not find in code commentary.
Ronald Hamburger's profile image
Ronald Hamburger posted 06-14-2023 04:11 PM Best Answer

Mark.  

As part of the input to the Hazard tool, as you are aware, you have to provide the Risk Category.  If you select Risk Category III, the tool will report tornado wind speeds for 1700 year and the 10,000, 100,000 MRIs as you note.  If you select Risk Category IV in the input, you will get a report of 3,000 year MRI, as well as the higher MRI wind speeds.  You cannot directly interpolate the data to obtain the desired values.  I hope this helps.