In this presentation you will learn about:
Past Earthquakes that have Affected Oregon
Oregon Structural Specialty Code History (OSSC)
City of Portland Seismic Code Requirements - Title 24.85
Seismic Upgrade Triggers and Evaluations
6. Oregon Structural Specialty Code
History
• 1956 City of Portland Adopts the 1955 UBC
• 1974 State of Oregon Adopts the 1973 UBC
• 1995 Portland City Council Adopts, Interim
Seismic Requirements
• 2004 Interim Seismic Requirements incorporated
in the City of Portland Title 24.85
• 2010 State Adopts the 2009 IBC – Current Code
• July 1, 2014 State Scheduled to adopt the 2012
IBC
Seismic Considerations Series 6
7. 1958 UBC
• Western Oregon
1. Zone 2
• Eastern Oregon
1. Zone 1
• Lateral Bracing -
Appendix
F = C W
Where,
C = 0.15 / N + 4½
For locations in Zone 2,
“C” shall be doubled
Seismic Considerations Series
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8. 1970 UBC
• NW Oregon
1. Zone 2
• SW Oregon
1. Zone 1
• Eastern Oregon
1. Zone 1
• Base Shear
V = Z K C W
Where,
Z = ½
C = 0.05 / ∛T
Seismic Considerations Series
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9. 1976 UBC
• ALL of Oregon
1. Zone 2
• Base Shear
V = Z I K C S W
Where,
Z = ⅜
C S ≤ 0.14
C = 1 / 15 √T
Seismic Considerations Series
9
10. 1988 UBC
• ALL of Oregon
1. Zone 2B
• Base Shear
V = (Z I C / Rw) W
Where,
Z = 0.2 (Zone 2B)
C = 1.25 S / T2/3
Seismic Considerations Series
10
11. 1991 UBC
• Western Oregon
1. Zone 3
• Eastern Oregon
1. Zone 2B
• Base Shear
V = (Z I C / Rw) W
Where,
Z = 0.3 (Zone 3)
C = 1.25 S / T2/3
Seismic Considerations Series
11
12. 1997 UBC
• Western Oregon
1. Zone 3
• SW Coastal
1. Zone 4
• Eastern Oregon
1. Zone 2B
• Base Shear
V = (Cv I / R T) W
Not exceeding
V = (2.5 Ca I / R) W
Where,
Z = 0.3 (Zone 3)
Cv = Ca = 0.3 (SB)
Seismic Considerations Series
12
20. Existing Buildings
• When are seismic evaluations required; and
• What triggers when seismic strengthening needs
to occur.
20Seismic Considerations Series
21. Local Design Requirements
• Oregon Structural Specialty Code.
• Chapter 34 Existing Structures
• ASCE 41-06 “Seismic Rehabilitation of Existing
Buildings”
• Existing buildings within city limits fall under chapter
24.85 of Title 24 “Building Regulations, Seismic Design
Requirements for Existing Buildings”
• ASCE 31-03 “Seismic Evaluation of Existing Buildings”
• (ASCE 41-13 “Seismic Evaluation and Retrofit of
Existing Buildings”)
Seismic Considerations Series 21
22. City of Portland Code Requirements
(Title 24.85)
• Public Safety;
• Owners planning to modify their existing buildings; and
• Purchasers of a building need to understand the possible
costs.
Seismic Considerations Series 22
23. Seismic Triggers
• Permitted Work Threshold
• Seismic Evaluation
• Change of Use or Occupancy
Classification
• 1/3 or more of the floor area
• 150 person occupant load
increase
Seismic Considerations Series 23
24. Required Seismic Evaluation
• Intended for the oldest and highest-risk buildings in Portland;
• For buildings permitted by the City prior to 1974 with
renovations exceeding $243,000;
Seismic Considerations Series 24
25. Required Seismic Evaluation
• All trigger costs are updated annually;
• Certain costs are excluded from building renovation
totals, including: MEP, Equipment, Painting, Fire
Protection, Site improvements, and Eco-roofs.
Seismic Considerations Series 25
27. Seismic Upgrade Triggers
• Change of Use or Occupancy that may require a higher
hazard level.
• Additions or Modifications must be in compliance with
current code.
• Special URM Building Requirements
Seismic Considerations Series 27
29. Required Seismic Upgrades
• URM buildings will require seismic upgrades for:
• Roof repair or replacement of 50% or more over a 5 year
period; or
• When cost of work, requiring a building permit, exceed
$41.63 per ft2 for buildings two or more stories and
$55.50 per ft2 for single story buildings, in a two year
period.
• Certain costs are excluded from URM building renovation
totals, including: Site improvements, Eco-roofs and
mandatory ADA and Elevator improvements.
Seismic Considerations Series 29
30. Seismic Strengthening Costs
• Varies greatly.
• Usually combined with other architectural
improvements.
• Cost Ranges:
o $15 to $50 / sf
o Lower for simple URM roof upgrade
o Higher for complex Code upgrade
Seismic Considerations Series 30
31. Code vs. ASCE 31
• ASCE 31 is 75% of Code
• ASCE 31 allows for some non-Code compliant
materials
Seismic Considerations Series 31
32. Questions?
Edwin T. Dean, PE, SE
Managing Principal
(503) 445-8685 p
ed.dean@nishkian.com
Robert A. Aman, PE, SE, LEED AP
Associate
(503) 445-8687 p
rob.aman@nishkian.com
PK Park, Eugene, Oregon
Home of U of O Baseball
Video & Scoreboard Towers
Seismic Considerations Series 32
