Post on 20-Apr-2022
Simplified Seismic Assessment& Seismic Retrofit Guidelinesfor
Detached, Single-Family, Wood-Frame Dwellings
FEMA P-50 & FEMA P-50-1
Simplified Seismic Assessment& Seismic Retrofit Guidelinesfor
Detached, Single-Family, Wood-Frame Dwellings
FEMA P-50
Simplified Seismic Assessment& Seismic Retrofit Guidelinesfor
Detached, Single-Family, Wood-Frame Dwellings
FEMA P-50-1
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Intent:
Provide a tool that communities and other entities can use to encourage the seismic retrofitting of residential structures, thereby reducing future earthquake losses
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Crawl Space House with Cripple Walls
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Crawl Space House with Cripple Walls
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Crawl Space House with Cripple Walls
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Slab-on-Grade House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Slab-on-Grade House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Slab-on-Grade House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Perimeter Post-and-Pier House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Perime
Hillside House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Common Earthquake Vulnerabilities Perimeter Post-and-Pier House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Intended Users
• Home inspectors• Home retrofit and remodel contractors• Design professionals• Homeowners• Insurers• Lenders• Building officials• Emergency planners • Others involved in hazard mitigation
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Training Objective: P-50 Seismic Assessment
Introduce methodology to:
Assign a Seismic Performance Grade
Identify seismic retrofit opportunities & priorities
Identify an improved Seismic Performance Grade with seismic retrofit
C+ B+15
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
Seismic Performance Grade A through D-
Conveys generally anticipated seismic performance
Given structural characteristics & geographic location
Relative to overall group of detached wood-framed single-family dwellings
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Training Objective: P-50-1 Seismic Retrofit
Provide a brief introduction to FEMA P-50-1 resources for:
Selection of seismic retrofit measures to implement
Design of seismic retrofit measures
Reassessment of a dwelling
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Webinar Outline
• Part 1: Wood-Frame House Construction
• Part 2: Assessment Using FEMA P-50
• Part 3: Next Steps after the Assessment Using FEMA P-50-1
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Part 1:
Wood-Frame House Construction
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Wood-Frame House Construction
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Common house configurations:
1. Crawlspace w/ cripple wall
2. Basement & foundation wall
3. Slab on grade
4. Perimeter post & pier
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Wood-Frame House Construction Crawl Space House with Cripple Walls
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Crawl Space House with Cripple Walls
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Basement or Foundation Wall House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Basement or Foundation Stem Wall House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Slab-on-Grade House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Perimeter Post-and-Pier House
Footing
Diagonal Brace
Post
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Perimeter Post-and-Pier House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
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Wood-Frame House Construction Perimeter Post-and-Pier House
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
PART 2: Dwelling Assessment
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Dwelling Assessment
The assessor needs:
One hour, approximately
Knowledge of the basics of wood-frame construction, materials, construction techniques
Helpful to have some knowledge of load path (how earthquake loads move through a structure)
Equipment for inspecting attic, crawlspace
FEMA P-50 assessment form
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
Intended Use:
Single-family dwelling
Primarily wood-frame construction
Seismic Design Category C through E
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
Structural Score:
A. Foundation
B. Superstructure Framing and Configuration
C. General Condition Assessment
D. Nonstructural Elements, Age and Size
E. Local Site Conditions
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Regional Seismic Hazard Score:
F. Regional Seismic Hazard Score
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
Structural Evaluation Areas:
A. Foundation
B. Superstructure Framing and Configuration
C. General Condition Assessment
D. Nonstructural Elements, Age and Size
E. Local Site Conditions
Structural Score: 100
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score Terminology
Assessment Items A-1 through E-6 are evaluated
Penalty Points are assigned for each Assessment Item based on the applicable Condition (condition a, condition b, etc.) with the highest number of
Penalty Points
Summed Penalty Points are subtracted from 100 to
give the Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score Terminology
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Assessment Item A-1
Conditions a, b
Penalty Points
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
a. Continuous concrete and reinforced masonry exterior footings Continuous perimeter grade beams or tie-beams.
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
b. Continuous footings of other materials such as unreinforced brick or stone masonry.Discontinuous footings such as isolated post-and-pier systems, isolated drilled pier systems without tie-beams, and partially continuous perimeter footings
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
b. Continuous footings of other materials such as unreinforced brick or stone masonry.Discontinuous footings such as isolated post-and-pier systems, isolated drilled pier systems without tie-beams, and partially continuous perimeter footings
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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1
3
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
7.4
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Structural Score: 92.6
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural Score
21.9
Structural Score: 70.7
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural ScoreStructural Score: 68.9
1.8
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural ScoreStructural Score: 62.9
6.0
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Structural ScoreStructural Score: 58.9
4.0
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
http://earthquake.usgs.gov/designmaps/usapp
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
http://earthquake.usgs.gov/designmaps/usapp
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http://earthquake.usgs.gov/designmaps/usapp
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
1.02102
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
4
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
http://myplan.calema.ca.gov
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
http://myplan.calema.ca.gov
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
4
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
http://myplan.calema.ca.gov
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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http://geohazards.usgs.gov/qfaults/map.php
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Regional Seismic Hazard Score
4
0
4
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
7.4
21.9
1.86.0
4.041.1
58.9
4
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
7.4
21.9
1.86.0
4.041.1
58.9
4
C+
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Seismic Performance Grade
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Basis for Seismic Performance GradesLetter Grades
Expert Opinion
Los Angeles pilot study of 400 dwellings
Damage Ranges
Percent of replacement cost of house
Annual probability of exceedance of 1/500
Reasonable approximation of single event for which owner will have to repair damage
Based on 2012 EQECAT study using modifiers developed for CEA, modeling 7600 combinations of dwelling configuration and seismic design category, and covering a range of seismic events deemed credible by USGS
(Sec. 2.4.5)
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Limits of the Methodology (Sec. 2.5)
Performance for an assigned grade could vary widelydue to limits of assessment
Dwelling construction and resulting earthquake response is inherently variable
Limited portions of the structure are visible without removing finish materials
Variability is inherent in seismic hazard
Owner could choose to perform a more detailed assessment to increase level of knowledge
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Limits of the Methodology
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Improving the Structural Score
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Improving the Seismic Performance Grade
15.073.9
B
21.580.4
B+
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Improving the Seismic Performance Grade
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
PART 3: After the Assessment
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Regulation
Voluntary Retrofit:
Owner is generally free to
• Choose to implement seismic retrofits
• Select which assessment items to retrofit
• Provided the retrofit does not make the house more vulnerable to earthquake damage
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Regulation
Mandatory Retrofit:
• May become mandatory triggered by:
– Alteration or addition to house
– Local retrofit ordinance
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Selection
Voluntary Retrofit:
Important to consider available guidance in:
• Selection of assessment items to retrofit
• Design of retrofit measures
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Selection
Retrofit objective:
• Reduce damage
• Increase occupant safety
• NOT strengthen the entire house
• NOT avoid all damage
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Selection
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Selection
FEMA P-50-1 Retrofit Guidance
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FEMA P-50 Assessment Items
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Design
Guidance available:
• Not a single resource document to provide direction
• FEMA P-50-1 collects information on available methods and resources
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Design
Prescriptive: • Construction requirements are prescribed in detail in
text, tables, and/or figures• Generally does not require involvement of a engineer/
architect – can be implemented directly by contractor• Limits exist on the type and configuration of the
building to be retrofitEngineered:• Construction requirements are calculated for particular
building based on specific earthquake loading• Requires involvement of engineer/ architect in addition
to contractor, with greater time and expense• No limits on type an configuration of building
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Retrofit Methods
• Method 1: Prescriptive International Existing Building Code (IEBC) Chapter A3 – cripple wall bracing and anchorage to foundation
• Method 2: Prescriptive retrofit method for nonstructural building elements
• Method 3: Prescriptive retrofit method in accordance with International Residential Code (IRC) requirements for new construction
• Method 4: Engineered retrofit method
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Reassessment of the Seismic Performance Grade
Fundamental to the FEMA P-50 assessment process is the concept that dwellings can be reassessed. This might be done to:
• Revise the Seismic Performance Grade following retrofit
• Better assess items addressed in the assessment form as a “detailed” rather than “simplified” assessment
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
The qualified design professional would be:
• An engineer or architect experienced in structural engineering can re-evaluate penalty points assigned towards the Structural Score
• A geotechnical engineer can re-evaluate the assigned Regional Seismic Hazard Score
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Reassessment of the Seismic Performance Grade
FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
Implementation of an Assessment Program
The benefits of reduced economic losses following a major to moderate earthquake extend to the homeowner, but also to many others beyond. Following are some of the persons and organizations that serve to benefit and therefore should consider establishment of plans to implement a program of assessment and retrofit:• Homeowner • Lender• Insurer• Local government
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FEMA P-50 & FEMA P-50-1Simplified Seismic Assessment
QUESTIONS OR COMMENTS?
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