Wind Loads - Enclosed or Partially Enclosed Building 1

[MRE]

Using ASCE 7-02 I have one wall in a structure that qualifies as Partially Enclosed. Does this mean that the entire structure is analyzed as partially enclosed (GCpi= +/-0.55) or just that wall?

 

[jbanderson]

Re-read the definition of partially enclosed. This applies to the building envelope, not to one wall.

 

[Lutfi]

If you have one wall, I would treat it as a sign. If it is apart of a building, then you must evaluate the entire building, then compute the pressures for zones 4 and 5 for the windward and leeward walls. Remember to design walls for the wind pressure of the end zones (i.e. zone 5) even for the walls within the inside field (i.e. zone 4).

Good luck.

 

[EIT2]

Lutfi,

Why should I design the Interior Zones using the End Zone pressures? Is there something in IBC or ASCE that I am overlooking? These loads tend to be, in certain situations, ... do I dare say "outrageously" high? Only in comparison to my pre-IBC design days just a year-and-a-half ago.

My concern is the over-specification of hurricane ties and cost. I will always appreciate the sincere importance of safety factor, but what about the ever-popular, and often credible general contractor response that "we have been constructing buildings for over twenty years, and we never had to reinforce the way we do today"? The buildings ARE still standing! During pre-IBC, I have always designed for wind, but the loads were typically lower at that time.

Ever since IBC, snow and wind loads (at least for Wisconsin) have, by design, increased dramatically! I will always design by requirement and with utmost safety in mind.
I am just looking for your comments and recommendations.

 

[CTSeng]

EIT2,
Welcome to the world of ever evolving codes, I think it’s mostly a political thing though I don’t understand what motivates it except some code gods wanting to take power out of the hands of the locals because they're smarter. It does bother me that the updates seem to say that everything designed up until now is substandard. I agree that the “we have been constructing buildings for over twenty years ...” argument is a tough one but I always place the blame where it started, “it’s the damn the new code”. Contractors swallow that better than trying to explain that new research shows the new wind/snow loads are more accurate.

That said, I agree with Lutfi that you should design for the end zones as the typical condition. I also generally design an entire structure as enclosed or partially enclosed. I then use more conservative end zone or overhang loads for lanais or porches or similar appendages on enclosed structures.

 

[EIT2]

CTSeng and Lutfi;

At your convenience, please refer to thread507-77652.

Thank you!

 

[jheidt2543]

Another thought. The end zone is the "worst condition" and if you design the interior zones to a smaller load, then the framing can be lighter. However, could it be that the changing from one type of framing to another, in the length of a wall, could lead to more problems, confusion and cost in the field? In the long run, it is just cheaper to keep the design consistant in the length of the wall?

Just a late night thought!