Penthouse Design per ASCE 7- Chapter 13

[Adams34]

For a Penthouse designed per ASCE 7-16 Chapter 13, what structural limitations and height limits applies? Looks like Chapter 13 is silent on structural system limitations. Chapter 12 and 15 have structural system limits. Ultimately, I am trying to figure out if Ordinary Steel moment frame is permitted for a penthouse in SDC D

 

[HTURKAK]

Pls look again Table 12.2-1 Design Coefficients and Factors for Seismic Force-Resisting Systems. And the footnote J;
Steel ordinary concentrically braced frames are permitted in single-story buildings up to a structural height, hn, of 60 ft (18.3 m) where the dead load of the roof does not exceed 20 lb∕ft2 (0.96 kN∕m2) and in penthouse
structures.
If the penthouse covers substantial area, it is reasonable to consider this as a separate level of the building.If you use
different lateral load resisting systems along the height of the building, you should follow 12.2.3.1.




He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[Adams34]

I think you are referring to design per chapter 12. My question is about design per chapter 13 of ASCE 7-16. Both chapters are different in my opinion or are they not? Chapter 12 is for main building Lateral load resisting system while chapter 13 is for non structural components like Architectural components which penthouse falls under

 

[HTURKAK]

My understanding is , penthouse is a small str. built over the roof slab . In general constructed
from steel,and braced laterally and is sufficiently rigid to transfer its seismic, roof and snow loads to the roof level.
If the pent house small , you may follow chapter 13 and pls look Table 13.5-1 Line item ( Coefficients for Architectural Components Penthouses (except where framed by an extension of the building frame).

If it covers large area , ( which may effect the total seismic ht. ) and its frame is continuity of the main frame ,you are expected to look chapter 12.

Sometimes , designing for both alternatives and taking the more stringent one could be the way to go.







He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[sticksandtriangles]

To HTURKAK's point, choosing to go chapter 12/chapter 13 can have some large impacts on your capped period in ASCE 7, which in turn could have some large impacts on your seismic base shear.

https://www.eng-tips.com/viewthread.cfm?qid=484622

Depending on if you fall squarely in the "this is a penthouse, chp 13" / "this is an extra level, chp 12" camp, it might make sense to design for both as HTURKAK mentioned.



S&T -

http://www.re-tug.com

 

[Adams34]

I don't think I get what you are saying because chapter 13 does not depend on the period of the structure. It gives you an Fp equation that is independent of period.

 

[sticksandtriangles]

I don't think I get what you are saying because chapter 13 does not depend on the period of the structure. It gives you an Fp equation that is independent of period.

You are right, if you pick chapter 13, the design forces for the penthouse are Fp forces.

The change I am mentioning is in the calculation of your overall base shear from ELF in chapter 12. Using a smaller "h" (omitting the penthouse height) will limit your capped period, which in turn could increase your base shear from ELF.