Ct Temperature Factor Use

[AZPE]

Today I was brushing up on my 2005 NDS and I looked at the Ct value and noticed that for temperatures ranging from 100-125F in a dry condition the factor is 0.8. Is anyone reducing their dowel type fastener values (screws, nails, bolts, etc.) by this factor? I have only worked in Arizona for a couple of years and before that I was in a much cooler place and didn't ever think of it, hence I haven't been applying that specific factor.

Your thoughts?

 

[csd72]

Is it likely to be 100 plus when the wind is blowing or the snow is on the roof?

 

[AZPE]

In Arizona, YES! It only cools off to about 95 degrees at night for a good part of two or three months...

 

[UcfSE]

According to Breyer, it is not necessary to design for a lower C_t under typical building conditions since the elevated temperature is temporary and are not usually subjected to full design load under these conditions.

Perhaps in AZ the case is a little different. Though I suspect most of the building is insulated and therefore won't be at the same temperature as the outside ambient air temperature, perhaps the attic can get to these elevated temperatures and hold there. Exterior framing would be different of course.

Bottom line, if you think it is necessary, use it. I would do a little research and find the relationship between the temperature factor and the time to which the members are exposed to this temperature. We are saying a lot of "temporary" and "unlikely" but maybe you can put a number with that.

 

[csd72]

My point was, check what the critical case is for the connection and then see if it is going to occur at the same time as the high temperatures.

e.g. if the critical case is snow then this case is clearly not an issue and you need to check the next worst case with the 0.8 factor.

csd