Is this a Non Building Structure Similar to Building or Not similar to a building? 4

[NewbieInSE]

Dear Engineers,

I have known that Non-building structures which have a framing system as of Buildings like Moment frame, Shear wall, dual system, etc., can be regarded as Non-building structure similar to a building. But still, I have lack of confidence in that. I have attached a two-page pdf file, where an Elevated Water Tank structure supported by Moment Frame has been shown. Please guide me to reach the conclusion of "Is this a Non-Building Structure Similar to Building or Not similar to a building?".

Thank you.

 

[HTURKAK]

Pls look ASCE 7 -16
15.7.10 Elevated Tanks and Vessels for Liquids and Granular Materials

and ,

ACI 350.3-06 Seismic Design of Liquid-Containing Concrete Structures and Commentary...

If you have specific question, you may get specific responds ..

 

[BAretired]

There are similarities and non-similarities, but it isn't clear how that knowledge achieves anything useful.

BA

 

[JStephen]

I'd say it could be considered as either, there is some overlap.
See, for example, in ASCE 7-10, Table 15.4-2, that whole table is "not similar" structures, but one item is "Tanks or vessels supported on structural towers similar to buildings".

 

[r13]

I think HTURKAK get my vote here. Water tower is a very distinct structure that has minimal similarity with building.

 

[r13]

According to this paper, it is a nonbuilding structure similar to building, and design shall follow section 15.5.5. Link

I was thinking more on dis-similarities, function, loading, etc.

 

[JStephen]

I don't think the paper really addresses that. It says "Section 15.5, provides specific requirements for certain nonbuilding structures similar to buildings:...Structural Towers for Tanks and Vessels (15.5.5)" But it doesn't really say which ones fall into which category, either. IE, it says that "certain" structural towers fall under that category, but doesn't say which ones are intended, which is the question in the first place.

 

[r13]

Albeit lacking specifics, it is unfortunately the most clear linking available so far.

Below is a researcher's complain in treating water tank as buildings.

 

[r13]

Base shear calculation using different code.

 

[NewbieInSE]

Thanks all for commenting.

If it (Elevated tanks, vessels, bins or hoppers- On symmetrically braced legs) is not similar to building then I'll have to use "R" value 3.0 irrespective of Seismic Zone, In Seismic Zones D,E,F as per ASCE, where the Zone Coefficients, Z are very large resulting in very high base reaction (pile numbers increasing), also member design becomes "uneconomic". Please shed light on this.

Question 1:If R=3, considered in Seismic Zones D,E,F, is it required to detail Specially? I mean as like SMRF.

Then If It (Tanks or vessels supported on structural towers similar to buildings) is considered similar to buildings, then R value can be used 8.0 for Zones D,E,F with special Detailing requirement, also less base reaction resulting less nos of piles.

Please share your thoughts, Thanks.

 

[NewbieInSE]

Does Elevated Tank mean "a tank at the top of say roof or stair top" and design for that component needs to be for R=3?

There are a lot of tanks: Tanks, Elevated Tanks and Tanks supported on Structural Tower.

What about an underground tank, does it require any of these things? what R value for that structure.

 

[r13]

Newbie,

I would never design this structure using building code alone, without consulting other relevant standards/codes such as AWWA and API, remember that no matter how you classified/categorize it, it is not a building, and behaves/respond in very different ways as building.

 

[HTURKAK]

These are my personnel opinions;
I looked to the pdf drawing again. The supporting structure with six columns, and tie beams at intermediate 3 levels implies non-building structure similar to building however , the behavior of the structure (concentrated mass at the top) is not similar to the behavior of building type structure. That is, the structure is non-building and not similar to building.

The RC structure with intermediate tie beams essentially similar with Cross-braced column-supported elevated tank.

I looked to the codes and standards;

AWWA D100 = Response modification factors Ri and Rc Cross-braced column-supported elevated tank R= 3.0


ACI 350.3 Ri = 3.25 is the maximum Ri value permitted to be used for any liquid-containing
concrete structure

ASCE 7-16 Table 15.4-2 Seismic Coefficients for Nonbuilding Structures Not Similar to Buildings
Elevated tanks, vessels, bins, or hoppers: On symmetrically braced legs (not similar to buildings) R= 3

I understand the reason for to use R = 8.0 , however, after performing the required P-delta analysis , and comply with drift requirements, eventually R will be around 3.0

I will suggest you, follow the SMRF detailing requirements and use R=3.0

I am not a native English speaker , may be some of the wordings will not explain what I want to say...

 

[r13]

An illuminating comment on the selecting of "R" values.

The response modification coefficient, R, is part of a concept where an elastic design may be performed, but with due consideration of the overstrength and ductility inherent in the lateral force resisting system. In order to ensure reliability, many requirements are triggered with each R factor. The “R” Tables, [Table 12.2-1] and [Table 15.4-1, 2], list the corresponding detailing requirements. The “strings attached” can be extremely significant, especially for concrete structures that fall under ACI 318-11 Chapter 21 and steel structures with R greater than 3 (AISC 341 Seismic).

 

[SlideRuleEra]

NewbieINSE - In addition to HTURKAK's comments:

No walls... no floors... which would have provided secondary load paths.
Result, No Redundancy... for a structure that will have to resist the potentially devastating seismic sloshing of liquid in an elevated tank.

Concerning your question on underground tanks:

Design driven more by geotechnical issues like soil properties, ground water elevation, and surcharge loads on the tank from the surface of the ground.

Many times, for industrial-type structures, there are higher priorities than lowest first cost... priorities such as reliability and longevity.
Perhaps this tank is a small piece of a "Big Picture", but loss of the tank could cripple other essential facilities that depend on it.

http://www.SlideRuleEra.net

 

[NewbieInSE]

Well, thanks everybody for your insightful replies.
I'm grateful to you all for putting your time in the matter.

So my conclusion is "The structure is a Non-building structure not similar to building"

 

[r13]

Newbie,

The linked SM article confirms your conclusion, in which it says "Tanks and vessels are nonbuilding structures not similar to buildings. As such, they exhibit a very different dynamic response than building structures." Link

 

[NewbieInSE]

retired13,
Thanks, Thats a good article.

 

[r13]

Newbie,

Glad that something is useful to you. And, thanks for asking a good question.