RTU on 'isolation curb'
RTU on 'isolation curb'
(OP)
The attached is from ASCE 7-10.
For determining connections for an RTU to an isolation curb and the isolation curb to the roof, would one use R=2.0 (or 2.5) and then multiply by factor of 2 per footnote (b)?
...attachment is from CHAPTER 13 SEISMIC DESIGN REQUIREMENTS FOR NONSTRUCTURAL COMPONENTS, ASCE 7-10
Table 13.6-1 Seismic Coefficients for Mechanical and Electrical Components
For determining connections for an RTU to an isolation curb and the isolation curb to the roof, would one use R=2.0 (or 2.5) and then multiply by factor of 2 per footnote (b)?
...attachment is from CHAPTER 13 SEISMIC DESIGN REQUIREMENTS FOR NONSTRUCTURAL COMPONENTS, ASCE 7-10
Table 13.6-1 Seismic Coefficients for Mechanical and Electrical Components






RE: RTU on 'isolation curb'
RE: RTU on 'isolation curb'
Do you have a different link to that table?
RE: RTU on 'isolation curb'
Yes, much better...
RE: RTU on 'isolation curb'
Dik
RE: RTU on 'isolation curb'
EQN 13.3-1
Fp =
0.4 * ap * SDS * Wp * ((1+2*(z/h)
( Rp / Ip )
I normally use Rp = 6.0 for standard RTUs.
If correct so far, and then utilizing Rp from middle section of Table 13.6-1, say 2.0, I've effectively tripled Fp. And then does the footnote criteria double that again?
RE: RTU on 'isolation curb'
RE: RTU on 'isolation curb'
For RTUs on a standard manufacturer's curb, do you use Rp 6.0?
RE: RTU on 'isolation curb'
Dik
RE: RTU on 'isolation curb'
Large air handling units often times have internal isolators on the fans. When this is the case, I use the ap=2.5 and Rp=2.0. But a good argument could be made for scaling the forces based on the weight of the fans with ap=2.5 and Rp=2.0 and weight of the rest of the unit with ap = 2.5 and Rp = 6.0.
About 75% of my work is in hospitals where special seismic certification (shake table testing) is required. In that case, I use the ap and Rp used for certification.
RE: RTU on 'isolation curb'
Thank you very much for your insights and recommendations. I feel like I have a better handle on the loads now.