HomeMy WebLinkAboutFile Documents.427 Rio Grande Pl.0016.2019 (14).ACBK
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KL&A, Inc.
215 N. 12th Street, Unit E
Carbondale, Colorado 81623
Telephone: (970) 927-5174
May 30, 2019
Mike Metheney, Chief Building Official
City Hall
130 South Galena Street
Aspen, CO 81611
Re: Aspen City Offices – Building Risk Category
Dear Mike,
KL&A is proposing that the new Aspen City Offices building complies with IBC 2015 requirements
to be designed as a category type II building. The purpose of this letter is to document the logic
that has gone into our interpretation. In review of this letter, please refer to the attached
documents:
1) Excerpt from IBC 2015.
2) Site Plan: this shows the overall view of how the new city offices building relates to the
library, and their separation of roughly 30’. It also shows their common egress path onto
the garage plaza level. This egress path is unaffected by the new addition.
3) SR101: 2015 plaza plan from SA Miro shows the existing garage plaza-level structure and
how the library and city offices relate to the plaza structural framing.
4) New plaza level structural plan: this shows the layout of the new city offices structure at
the plaza level and the proximity of the library structure.
IBC Section 1604.5.1 states “Where buildings or structures have two or more portions that are
structurally separated, each portion shall be separately classified.”
- On our project, the existing library, existing parking garage, and new city offices are all one
building. The nature of occupancy of the library requires the classification of risk
category III, while the occupancy in the new city offices complies with a risk category II.
- IBC does not define “structurally separated”, so interpretation is required to determine
whether the library and the city offices are structurally separated. ASCE7-10
commentary section C1.5.1 states “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.”
We believe that the points below are a “rational” basis for justifying the use of separate
building categories for the library and the city offices.
· The only common structure linking the two buildings together is the parking
structure, which has exponentially greater stiffness than the other two buildings
and therefore, would not transfer loads from the library to the city offices or
vice-versa. 05/30/2019
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· The city offices has been designed to have it’s own lateral system that is not
dependent on the lateral strength of the garage.
· The gravity load paths of the library and the city offices are fully separated from
one another. Referencing the garage plaza structural plan, it can be seen that
there is no overlap of support for gravity load paths of the library and city offices.
To put in another way, structural failure in either building would not affect the
other building.
Please contact me if you have any questions or comments.
Sincerely,
Dan Doherty, P.E.
Principal
05/30/2019
05/30/2019
This alternate method is acceptable as it meets the
intent of the 2015 IBC section 104.11 and is equivalent
in fire and life safety.
05/30/2019