ASCE 7-05 Table 15.4-1 "Height Increase"
ASCE 7-05 Table 15.4-1 "Height Increase"
(OP)
What allows you to say that you have a system with "permitted height increase"?
I am analysing a structure used as a cooler along a conveyor system and the owner would like to install heavy item supported above it. ASCE table 15.4-1 does not permit the use of an OMF in seismic design category D unless it is a "permitted height increase" which would mean I can use an OMF up to 100ft as long as I use R=2.5, omega=2, & Cd=2.5. However, what permits me to say that I have an allowable height increase? I can't seem to find anything on this.
Thank you for helping,
I am analysing a structure used as a cooler along a conveyor system and the owner would like to install heavy item supported above it. ASCE table 15.4-1 does not permit the use of an OMF in seismic design category D unless it is a "permitted height increase" which would mean I can use an OMF up to 100ft as long as I use R=2.5, omega=2, & Cd=2.5. However, what permits me to say that I have an allowable height increase? I can't seem to find anything on this.
Thank you for helping,






RE: ASCE 7-05 Table 15.4-1 "Height Increase"
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RE: ASCE 7-05 Table 15.4-1 "Height Increase"
So my question still stands. Also section 12.2.5.6 & 12.2.5.7 for building structures does say I can use ordinary systems as long as the tributary load to the frame from the roof does not exceed 20psf and in light frame construction with floor or roof loads not exceeding 35psf.
RE: ASCE 7-05 Table 15.4-1 "Height Increase"
Contrary to popular belief, the cost is often in the complexity of the details rather than the magnitude of the seismic load. The idea that a smaller earthquake forces (higher R values) lead to smaller members doesn't usually hold true because members get held to tight compactness criteria and slenderness ratios that usually force you into a huge size.
That said, why not use an R of 1 per table 15.4-1 and avoid AISC 341 altogether? R=1 removes height limits altogether and only requires you to detail to AISC 360. R=2.5 still requires you to detail to AISC 341. Why make it harder than it needs to be?
To answer your original question, I believe the permitted height increase is addressed in the footnotes of Table 15.4-1 isn't it?
RE: ASCE 7-05 Table 15.4-1 "Height Increase"
RE: ASCE 7-05 Table 15.4-1 "Height Increase"