R for non-building structure with SRCMF construction

[Prestressed Guy]

Structure is in SDC - 3.

I am working on the conceptual design of a structure to house some industrial mechanical equipment.

The structure consists single elevated level of a Special Ranforced Concrete Moment Frame podium which will support a large mass of mechanical equipment and its enclosure. The columns would be designed as fixed top and bottom. The podium will have large mechanical units bolted to the floor wich will be structural steel with a composite concrete floor. For the podium, R = 8.
The enclosure for the equipment will be insulated precast concrete wall panels with a roof consisting of steel beams and corrugated metal deck. This enclosure would be detailed as an Intermediate Precast Shear Wall system which would have an r = 4.

If it were a building structure per 12.2.3 the R for the podium would be 4.

I am looking at this more as a Chapter 15 non-building structure per table 15-4-1. My thinking is that this is a chapter 15 structural podium. If that podium had a large, heavy piece of equipment housed in a weatherproof box the size of the podium it would still be designed as a SRCMF type structure with R = 8.

My understanding is that the provisions of 12.2.3.1 are more intended for a multi-story structure which has a soft story at the lowest level and this structure doesn’t really fit into that box. My understanding of 12.2.3 is to account for the dynamic response of the stiffer upper building but at least in the long direction, this upper structure will act like a rigid box. It might be that it would be better to use the lower R = 4 for the precast walls for the transverse direction.

 

[HTURKAK]

Copy and paste of some relevant Clauses;


11.2 DEFINITIONS
NONBUILDING STRUCTURE SIMILAR TO A BUILDING: A nonbuilding structure that is designed and constructed in
a manner similar to buildings, responds to strong ground motion in a fashion similar to buildings, and has a basic lateral and vertical seismic force-resisting system conforming to one of the
types indicated in Tables 12.2-1 or 15.4-1.


C11.1.3 Applicability. Industrial buildings may be classified as nonbuilding structures in certain situations for the purposes of determining seismic design coefficients and factors, system limitations,
Many industrial building structures have geometries and/or framing systems that are different from the broader class of
occupied structures addressed by Chapter 12, and the limited nature of the occupancy associated with these buildings reduces
the hazard associated with their performance in earthquakes.
Therefore, when the occupancy is limited primarily to maintenance and monitoring operations, these structures may
be designed in accordance with the provisions of Section 15.5 for nonbuilding structures similar to buildings. Examples of such structures include, but are not limited to, boiler buildings, aircraft hangars, steel mills,....automated manufacturing facilities, whereby the occupancy restrictions for such facilities should be uniquely reviewed in
each case. These structures may be clad or open structures.



I do not have any idea for the occupancy of the subject str.
I would prefer to follow Ch. 12 , and 12.2.2 Combinations of Framing Systems in Different
Directions..

Just my opinion !!!!!






I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[Prestressed Guy]

The structure in question certainly meets the requirements for a non-building structure. it is only entered for occasional maintenance and / or replacement of equipment. It does not even have a stairway or permanent ladder going to the podium floor.