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Re: Seismic Upgrade prob. W/97 UBC

[Subject Prev][Subject Next][Thread Prev][Thread Next] Lynn:
While a change in occupancy from retail (M Occupancy) to church (A-2.1 or 3) definitely results in a significant occupant load, there is no UBC requirement for a seismic upgrade based on occupant load increase alone.  If, however, the building become an A-2.1 Occupancy (having an assembly room with a OL > 300), the seismic I factor (Table 16-K) jumps to 1.15 and, since this is occupancy related, Section 3405 requires full compliance with Chapter 16.

If the use is an only an A-3 occupancy, this would not apply but since you are also removing structural walls and old walls are receiving new load then the analysis, design and construction of these walls must meet current code.  See UBC 3403.2.  You might try to convince the Building Official that only the new walls and walls with added load need to be strengthened.

Remember also that the 1997 UBC is applicable in California only to permit applications filed after June 30, 1999.  Permits filed before that date can use the 1994 UBC which could result in lower design forces.

Make sure you also check floor framing for the increase of live load to 100 psf.

Bob Bossi

Lynn H wrote:

The issue is Occupant Load, not so much a change in
occupancy.  There is a section in the Code where you
can figure the occupant load of the building.  You
add up the square footage of all the different uses
(office, storage, etc.) and you come up with an
occupant load for the building.
In this case, there is a change of Occupancy, but
more important, a significant increase in occupant
load also.

The current occupancy is retail, and the new use is
for a church.  The new sanctuary will hold several
hundred people.

In order to create the new larger room requirements
on the ground floor, we are in fact removing some
structural walls on the ground floor.

I do not know if this is a UBC thing, or a local
Code thing.  I have heard of a similar requirement
here in the City of Santa Barbara, so maybe it is a
UBC Code thing (the project I am talking about is
not in the City or County of Santa Barbara, the
jurisdictions local to our office).