.6D + W Question

[PBW2]

When calculating the vertical loads to a column for this load combination do you use the overturning wind moment to determine the vertical loads from wind (Mot/L=T=C)or do you use the tributary area x uplift force?

I have used the T=C from the horizontal Mot + wind area load + .6D but now I'm having second thoughts. Have also noticed in some publications that the compression force from the wind Mot is neglected which does not seem correct. Thoughts/Comments

 

[JAE]

All the wind - lateral and uplift, should be applied at the same time. Wind hitting a building will have lateral forces on the windward and leeward walls and uplift on the roof simultaneously.

You would typically use the MWFRS winds and not the C&C winds for a column in a brace system resisting wind from large tributary areas.

 

[PBW2]

JAE,

Thanks for the reply and we are applying lateral and uplift at the same time. I don't think i was clear in my original question please see below.

I have a total overturning moment calculated by the horizontal wind load x arm (height) + roof uplift load x l (distance from slab edge. From this I calculate the T & C on the columns/pile. This would give me the uplift per column based on the overturning.

I also calculate the uplift per column based on the tributary area. Should I add this to the T calculated above? If I do it seems that I would be doubling up on the wind.

 

[JAE]

You use the term "overturning moment" which you indicate is from the horizontal force x height and from the uplift on the roof over the tributary area.

This would be an analysis of the total structure using all the applied wind so the tension force you get from this overturning moment would include all the wind effects.

So if your term:
[blue]"roof uplift load x l (distance from slab edge"[/blue]

is the same as your term:
[blue]"uplift per column based on the tributary area"[/blue]

Then yes you are doubling the wind.

 

[a2mfk]

You could really cut to the chase and provide a sketch showing a FBD with all of your forces labeled