ASCE 7-10 Simplified Envelope Method
ASCE 7-10 Simplified Envelope Method
(OP)
Can someone explain to me why the simplified method does not use the Kz, velocity pressure exposure coefficient? I am getting much higher pressures using the simplified envelope method.
Thanks
Thanks






RE: ASCE 7-10 Simplified Envelope Method
Brian C Potter, PE
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RE: ASCE 7-10 Simplified Envelope Method
RE: ASCE 7-10 Simplified Envelope Method
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: ASCE 7-10 Simplified Envelope Method
RE: ASCE 7-10 Simplified Envelope Method
Should Kz be used with the simplified method?
It looks to me like the same tables were used for the simplified method going from ASCE 7-05 to ASCE 7-10 without making any adjustments to the pressures or the adjustment factor (lambda). The pressures should be lower in theory in the newer version than those in the older version, but I am not getting that unless I use the Kz exposure coefficient.
Detailed input would be appreciated.
Thanks
RE: ASCE 7-10 Simplified Envelope Method
In my experience, when calculating the velocity pressure from 05 to 10 there is an increase... so the qz value is sometimes 50% higher... when i go though the full process and apply a load factor my values become much more related... asce 7-10 LF=0.6 were equivalent in 7-05 is 1.0.
I do not have a ton of experience with ASCE 7-10, but i typically calculate it all out completely in a nifty spreadsheet :)
RE: ASCE 7-10 Simplified Envelope Method
I just checked my spreadsheet for 7-10 against Alex T's 7-05 spreadsheet and have similar results.
RE: ASCE 7-10 Simplified Envelope Method
Parks Payne, PE
RE: ASCE 7-10 Simplified Envelope Method
I am just puzzled as how you can use information from a map that assumes 1 set of criteria to navigate a table that assumes a completely different set of criteria.
RE: ASCE 7-10 Simplified Envelope Method
Not quite true. What was done was to apply the important factor to the wind map. So instead of one map and three important factors, we now have three maps. One for each Important Factor that existed before.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: ASCE 7-10 Simplified Envelope Method
RE: ASCE 7-10 Simplified Envelope Method
ASCE 7-05 Section C6.5.5 clearly shows that what was called the "Importance Factor" is really the MRI factor that is to be multiplied to the wind speed V, for the difference Occupancy Categories. Rather than creating three wind tables, in the ASCE 7-05, they decided to multiply it to the V in the equations. But since the V is squared in the equations, they squared the MRI's and call it an "Importance Factor".
Now in the ASCE 7-10 they took the wind maps and basically multiply the wind speed by the square root of 1.6 ( the 1.6 is the amount they decreased the effect of the wind speed in the basic load combinations). Then multiplied the new map values by the MRI's, for the "Risk Categories" (which are the old Occupancy Categories) to create two "new" maps.
As for the ASCE 7-10 figure 28.6-1 (cont.) with the I=1.0. They copied the table from the ASCE 7-05 and missed removing the I=1.0 factor note.
As for all the cookie cutter designers (even those who show a PE in their post) who are comparing spreadsheets "by others" for the ASCE 7-05 to the ASCE 7-10 loads. If you can not (or don't want to) do your own check of where the loads are coming from and how they are calculated. Then you should only ask for information here and not making statements about something they know very little about.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: ASCE 7-10 Simplified Envelope Method
My question regarding the transition from a map assuming certain criteria to a table that assumes another set of criteria still stands. Pertaining to the statement I made regarding multiplying the wind speed by sq. rt. of 0.6 was taken directly from IBC 2012 and is the multiplier they use to go from an "Ultimate Wind Speed" to a nominal or ASD Wind Speed. I do appreciate the good feedback.
As much as I appreciate your indirect jab, I am just looking for honest feedback.
RE: ASCE 7-10 Simplified Envelope Method
“It will be of little avail to the people, that the laws are made by men of their own choice, if the laws be so voluminous that they cannot be read, or so incoherent that they cannot be understood; if they be repealed or revised before they are promulgated, or undergo such incessant changes that no man, who knows what the law is today, can guess what it will be to-morrow.” (James Madison)