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24.85.020 Seismic Related Definitions.

(Amended by Ordinance Nos. 169427, 170997, 178831, 180917 and 187192, effective July 17, 2015.) The definitions contained in this Section relate to seismic design requirements for existing buildings outlined in this Chapter.

A.  ASCE 41 means the Seismic Evaluation and Retrofit of Existing Buildings ASCE/SEI 41-13 published by the American Society of Civil Engineers and the Structural Engineering Institute.

B.  ASCE 41 Evaluation means the process of evaluating an existing building for the potential earthquake-related risk to human life posed by that building, or building component, and the documentation of that evaluation, performed and written according to the provisions of ASCE 41.  Tier 1 and Tier 2 deficiency based evaluation for both structural and non-structural components using the Basic Performance Objective for Existing Buildings (BPOE) as defined in ASCE 41 shall be the performance objective for the evaluation, unless a Tier 3 evaluation is required by ASCE 41

C.  ASCE 41-BPOE Improvement Standard means the Tier 1 and Tier 2 Deficiency based retrofit for both structural and non-structural components using the Basic Performance Objective for Existing Buildings (BPOE) as defined in ASCE 41, unless a Tier 3 evaluation is required by ASCE 41. 

D.  ASCE 41-BPON Improvement Standard means Tier 3 Retrofit for both structural and non-structural components using the Basic Performance Objective Equivalent to New Buildings (BPON) as defined in ASCE 41.

E.  ATC 20 means the latest Edition of the manual on “Procedures for Post Earthquake Safety Evaluation of Buildings” published by Applied Technology Council.

F.  BDS means the City of Portland’s Bureau of Development Services.

G.  BPOE- Basic Performance Objective for Existing Buildings: A series of defined Performance Objectives based on a building’s Risk Category meant for evaluation and retrofit of existing buildings; See Table 2-1 of ASCE 41.

H.  BPON- Basic Performance Objective Equivalent to New Building Standards: A series of defined Performance Objectives based on a building’s Risk Category meant for evaluation and retrofit of existing buildings to achieve a level of performance commensurate with the intended performance of buildings designed to a standard for new construction; See Table 2-2 of ASCE 41.

I.  BSE-1E: Basic Safety Earthquake-1 for use with the Basic Performance Objective for Existing Buildings, taken as a seismic hazard with a 20 percent probability of exceedance in 50 years, except that the design spectral response acceleration parameters Sxs and Sx1 for BSE-1E seismic hazard level shall not be taken as less than 75 percent of the respective design spectra response acceleration parameters obtained from BSE-1N seismic hazard level and need not be greater than BSE-2N at a site.

J.  BSE-1N: Basic Safety Earthquake-1 for use with the Basic Performance Objective Equivalent to New Buildings Standards, taken as two-thirds of the BSE- 2N.

K.  BSE-2E: Basic Safety Earthquake-2 for use with the Basic Performance Objective for Existing Buildings, taken as a seismic hazard with a 5 percent probability of exceedance in 50 years, except that the design spectral response acceleration parameters of Sxs and Sx1 for BSE-2E seismic hazard level shall not be taken as less than 75 percent of the respective design spectra response acceleration parameters obtained from BSE- 2N Seismic hazard level and may not be greater than BSE-2N at a site.

L.  BSE-2N: Basic Safety Earthquake-2 for use with the Basic Performance Objective Equivalent to New Buildings Standards, taken as the ground shaking based on Risk-Targeted Maximum Considered Earthquake (MCER) per ASCE 7 at a site.

MBuilding Addition means an extension or increase in floor area or height of a building or structure.

N.  Building Alteration means any change, addition or modification in construction.

O.  Catastrophic Damage means damage to a building that causes an unsafe structural condition from fire, vehicle collision, explosion, or other events of similar nature.

P.  Essential Facility has the same meaning as defined in the OSSC.

Q.  Fire and Life-safety for Existing Buildings (FLEx) Guide means a code guide published by the Bureau of Development Services, outlining alternative materials and methods of construction that are allowed for existing buildings in Portland.

R.  FM 41 Agreement means a joint agreement between Portland Fire & Rescue, the Bureau of Development Services and a building owner to schedule improvements to the building following a determination of the fire and life safety hazards posed by the existing condition of the building as provided under Oregon law.

S.  Live/Work Space means a combination working space and dwelling unit.  A live/work space includes a room or suite of rooms on one or more floors designed for and occupied by not more than one family and including adequate working space reserved for the resident’s occupancy. A live/work space is individually equipped with an enclosed bathroom containing a lavatory, water closet, shower/and or bathtub and appropriate venting.

T.  Net Floor Area means the entire area of a structurally independent building, including an occupied basement, measured from the inside of the permanent outer building walls, excluding any major vertical penetrations of the floor, such as elevator and mechanical shafts.

U.  Occupant Load means the number of persons for which the means of egress of a building or portion thereof is designed. The occupant load shall be calculated based on occupant load factors in the table assigned to each space in the Oregon Structural Specialty Code (OSSC).

V.  Oregon Structural Specialty Code (OSSC) means the provisions of the State of Oregon Structural Specialty Code as adopted by Section 24.10.040 A.

W.  Reinforced Masonry means masonry having both vertical and horizontal reinforcement as follows:

1.  Vertical reinforcement of at least 0.20 in2 in cross-section at each corner or end, at each side of each opening, and at a maximum spacing of 4 feet throughout. One or two story buildings may have vertical reinforcing spaced at greater than 4 feet throughout provided that a rational engineering analysis is submitted which shows that existing reinforcing and spacing provides adequate resistance to all required design forces without net tension occurring in the wall.

2.  Horizontal reinforcement of at least 0.20 in2 in cross-section at the top of the wall, at the top and bottom of wall openings, at structurally connected roof and floor openings, and at a maximum spacing of 10 feet throughout.

3.  The sum of the areas of horizontal and vertical reinforcement shall be at least 0.0005 times the gross cross-sectional area of the element.

4.  The minimum area of reinforcement in either direction shall not be less than 0.000175 times the gross cross-sectional area of the element.

X.  Risk Category: A categorization of a building for determination of earthquake performance based on Oregon Structural Specialty Code (OSSC).

Y.  Roof Covering Repair or Replacement means the installation of a new roof covering following the removal of an area of the building’s roof covering exceeding 50 percent or more of the total roof area within the previous five year period.

Z.  Unreinforced Masonry (URM) means adobe, burned clay, concrete or sand-lime brick, hollow clay or concrete block, hollow clay tile, rubble and cut stone and unburned clay masonry that does not satisfy the definition of reinforced masonry as defined herein. Plain unreinforced concrete shall not be considered unreinforced masonry for the purpose of this Chapter.

AA.  Unreinforced Masonry Bearing Wall means a URM wall that provides vertical support for a floor or roof for which the total superimposed vertical load exceeds 100 pounds per lineal foot of wall.

BB.  Unreinforced Masonry Bearing Wall Building means a building that contains at least one URM bearing wall.