Conflict in Risk Category Table 1

[lutein]

We are working on a high rise hotel with a meeting room space hosting more than 300 people; in our opinion, the structure should be categorized as II. FBC 2010 Risk Category Table 1604.5 clearly states that Risk Cat III is meant for 'structures whose primary occupancy is public assembly', in which the hotel is not. IBC 2012 clarifies 'primary occupancy' as 'the portion of the building housing the public assembly occupancy is more than 50% of the total building area' [IBC 2012 pg. 16-10]. We don't think it's logical to punish the whole tower just based on 1 single space of meeting room.

What is your thoughts and experience in this?

Thank you for your input.

 

[flight7]

The line in the table reads "Buildings and other structures whose primary occupancy is public assembly with an occupant load greater than 300". The primary occupancy of your building is not public assembly, therefore this line doesn't apply. However, it doesn't matter what I think. Check with the building official who will be reviewing your plans for the building permit.

 

[IDS]

Regardless of what the code says, it makes no sense to me to design a meeting room to a lower standard because it is incorporated in a structure that also houses a large number of people, but in separate rooms.

Codes set minimum standards, and it seems to me that in this case the higher standard should be applied.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[JAE]

It would be technically II.

However, if you read the commentary of ASCE 7-10, it suggests: [blue]"A rational basis should be used to determine the risk category for structural design, which is primarily based on the number of persons whose lives would be endangered or whose welfare would be affected in the event of failure. Figure C1-1 illustrates this concept. "Lives at risk" pertains to the number of people at serious risk of life loss given a structural failure."[/blue]

It then shows Figure C1-1 with a cutoff between II and III buildings at about 300 persons.

This implies that despite the rigid interpretation of "primary occupancy is public assembly" your big hotel would have lots of people in it at any given time and a structural collapse would affect many lives - suggesting a III is more appropriate.

I think I would tend to use II but would think that getting buy in from the city or owner would be needed.



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[structSU10]

The commentary of ASCE 7-10 also states that lives at risk should also include persons outside the structure who may be affected by its collapse. The wording of the code itself is very ambiguous, merely stating for risk category III 'buildings and other structure, the failure of which could pose a substantial risk to human life' - it is only clarified by the commentary.

 

[Archie264]

"A rational basis should be used to determine the risk category for structural design, which is primarily based on the number of persons whose lives would be endangered or whose welfare would be affected in the event of failure. Figure C1-1 illustrates this concept. "Lives at risk" pertains to the number of people at serious risk of life loss given a structural failure."

Wow, there's a lot of room for mischievous interpretation in that statement. Just about any sizable building in an urban environment could be said to meet that criteria. All the more reason to get a ruling on it, in writing, from the building official, as Flight7 advised.

I guess we're all Category III now. Will anyone raise me to Cat. IV?

 

[JAE]

I might throw in the observation that the IBC has its own table for Risk Category which looks more like the older ASCE 7.

And the IBC would or could overrule the ASCE 7 table that in my view is so general to be useless.

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[mpocius]

I am dealin with this exact issue on a 5 story wood framed apartment building wrapping a 6 story precast parking garage in Northern Vriginia. The county is interpreting the risk category as III due to yhe size of the building. I am trying to make a case to use Category II. Being that the location is moderate wind and seismic load criteria, the design implications on the wood lateral system is not that severe.

There would , however, have enormous implications on the precast garage lateral design.