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Re: R for a steel structure w/ equipments

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The "R" factor does not depends on what type of structure. The "R" factor can be justified by the "value" engineer.  As a value engineer, you can justify it considering the material and connection behavior of the lateral system.
For example, OMF and SMF have same material but different connection detailing. Because SMF have more ductile connection detailing, it has higher "R" factor.
This "R" factor is decided by overstrength factor and ductility factor. Therefore, you need to know both.

For the further information, please refer "Blue book" or FEMA document. Probably you can find a good reference.

Chung-Soo Doo

"Vasu, Ravi" wrote:

> I am sending this question again.  Can somebody look into this & give
> comments?
> Please refer to the " seismic guidelines for design of petrochemical
> faclities" by ASCE committee, section for non building
> structure & section 4.2.4 for subsystem.
> 1. The question is what is the value of R for (a combined system) a steel
> structure with platform &  supporting a small vessel & exchanger in
> a two or three storied structure (30 to 40' height).
> If it is a BUILDING (or building like) STRUCTURE, we use R from table 16-N
> of UBC 1997.   Right?
> 2.  If the equipment wt. (one or more added toghether?)is more than 0.25(wt.
> of the structure), do we need to (always) consider lower
> R of the equipment and the structure ?  (appendix A, case 3 & 4)
> irrespective of the height or area ?
> I have seen big coolers/cooling towers supported on steel structure(cooler
> covers most area of the structure).  I think only equipments like this
> (& tall vertical vessel) fall under this category.)
> 3. It looks like, most of the structures supporting a vessel/exchanger fall
> in 'subsystems' (section 4.2.4). What is R for this?
> Thanks.
> Ravi Vasu, P.E.,
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fn:Chung-Soo Doo, Ph.D.