ASCE7 Wind on Ice 1

[RFreund]

When evaluating Wind on an ice covered structures should you use the 3-second gust speed shown in the figure 10-2 (ice section) or should you use the wind speed shown in the wind section?

Thanks

EIT

http://www.HowToEngineer.com

 

[JoshPlumSE]

I believe it is generally over conservative to assume worst case wind and worst case ice at the same time.

The TIA tower code (communication towers) typically uses an ice wind speed that is a bit less than 50% of the wind used for the non-ice case. My guess is that this all comes from that ASCE chapter on ice loading. But, I have not explicitly researched it.

 

[DST148]

Agree with JoshPlum, it comes from ASCE. Ref ASCE 7-05, section 10.7, note 1 - The wind speed Vc shall be determined from Figs. 10-2 to 10-6 or a site specific study. However, for calculating velocity pressures qz for wind speed Vc, the code refers back to Chapter 6 - Wind Loads.

 

[RFreund]

Thanks Josh I would agree. If it were the case that full wind load and ice loads should be applied then you would prolly be increasing the size of your building.
Also they do show a figure for wind speeds which result in about just over half of the full or typical wind load would be. My only problem is that they don't explicitly say (or maybe they do and I'm missing it) to use the figure in the ice section for wind speed.

It reads:

"Wind loads on this projected area shall be used in the design of ice-sensitive structures. Figs 10-2 to 10-6 include 3-s gust wind speeds at 33ft above grade that are concurrent with the the ice loads due to freezing rain. Wind loads shall be calculated in accordance with chapters xxx as modified by sections 10.5.1-10.5.x"

Basically the modifications say that the dimensions shall be based on dimensions including ice.



EIT

http://www.HowToEngineer.com

 

[RFreund]

Thanks DST- I read the whole chapter and commentary and managed to miss that sentence, ok maybe I was skimming, either way...yikes.

EIT

http://www.HowToEngineer.com