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2/21/2017
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THE EVALUATION OF RECOMMENDED ALLOWABLE DESIGN PROPERTIES
FOR EXISTING STRUCTURES (DES160)
Al De Bonis, Ph. D.
Wood Advisory Services, Inc.
PHONE: 845-677-3091
WEB PAGE: www.woodadvisory.com
EMAIL: [email protected]
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This presentation is protected by US and International Copyright laws. Reproduction,
distribution, display and use of the presentation without written permission of
AWC is prohibited.
© American Wood Council 2016
COPYRIGHT
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“The Wood Products Council”is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516.
Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.
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Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
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DESCRIPTION
Throughout the world there are great examples of historic wood structuresthat have withstood the test of time and exposure to various climates. Oneof the challenges that code officials and designers face for modifying existingwood structures is determining what design properties to use. This webinarwill address methods used to establish recommended allowable designproperties for structural wood members in existing buildings. Examplesfrom several interesting projects will be presented including buildings underrenovation and waterfront structures such as piers.
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LEARNING OBJECTIVES
1. Understand methods used to identify wood species used as structural members in existing buildings.
2. Understand methods used to visually grade structural wood members in existing buildings.
3. Understand methods used to establish allowable design properties for visually graded lumber in existing buildings.
4. Understand methods used for condition assessment of in-service wood including quasi-nondestructive evaluation methods and equipment. 5
Outline
• Species Identification
• Visual Grading of In-situ Members
• Methods to Determine Allowable Design Properties for Wood Members
• Condition Assessment
• Examples (Existing Buildings & Waterfront Structures)
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Polling Question
What is your profession?
a) Architect
b) Engineer
c) Code Official
d) Builder/Building Designer
e) Other
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ASSIGNMENT: Re-design this 1905 Building using Current Codes
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After My “As-built“ Where Do I Begin ?
Basement 1st & 2nd
Levels Attic
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First – Identify The Species
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Macroscopic Identification UsingGross Features
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Microscopic Identification UsingMicroscopic Features
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Purchase Microscopic Equipment
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Recommendation
Hire an Expert
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Polling Question
Knowing the wood species is not required to determine design values?
True
False
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Second – Determine the Grade(Grade Stamps Would Be Nice)
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TYPICAL BUILDING IN THE NORTHEAST
7-10 POTENTIAL SPECIES4-6 POTENTIAL RAFTER OR JOIST SIZES
10-16 POTENTIAL COLUMN, BEAM OR GIRT SIZES
Technically to grade a wood member you must:
Look at each member full length – close up
Look at all 4 sides and at least 1 end (typically not possible in a building)
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GRADE RULE BOOKS
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Measuring Slope of Grain
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A Reasonable ProcessGrade Each Column, Beam and Girt
(Heavy timbers are easier to grade than joists & raftersand there are generally fewer of them than joists & rafters)
(Generally more structurally significant than joists & rafters)(Provide a map showing the grade of each member)
Grade a representative sample of rafters and floor joists(A percentage on each level and a general overview
of the remainder looking for major problems)30
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Place HolderAs built with Grades
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Recommendation
Hire an Expert
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Polling Question
Which of the following is not required to determine the lumber grade?
a. Viewing all 4 sides of a member
b. Location and size of knots
c. Slope of grain
d. Moisture content
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Third – With Known Species & GradeGet Recommended Allowable Properties
from the NDS
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Allowable Design Stresses for Visual Grades
Lumber – ASTM D-245 (Small Clear Specimen Testing)
(Prior to 1991 all Design Stresses)
ASTM D-1990 (In Grade testing of Full Size Lumber)
(Initiated in 1977 at WWPA – Adopted 1n 1991)
Round Timber Piles – ASTM D-2899 (Small Specimen Testing)
(Some Adjustments Based on Large Tests)
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Recommended Allowable Properties Based on Small Clears
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Recommended Allowable Properties Based onTesting Full Size, In-Grade Lumber
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Recommended Allowable Bending Strength from Ultimate Bending Strength Test Data
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Fourth – Don’t Forgetthe Condition Assessment
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Condition Assessment ToolsEvaluation of Decay
Incipient, Intermediate & Advanced Decay
1. Visual assessment – Intermediate and advanced decay 2. Moisture Meter – Potential for decay
3. Hammering – advanced internal decay 4. Pick test – Surface - incipient, intermediate and advanced decay
5. Resistograph - Internal intermediate and advanced decay 6. Core boring – All levels of decay
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Visual Identification of Decay
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Moisture Meter
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Pick Test – Pass & Fail
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Resistograph
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What the Resistograph Chart Tells Us
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Interpreting Resistograph ChartsThey Can Be Really Weird
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Resistograph Testing Through a Copper Covering into a Wood Column
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Resistograph Testing Through Floor Boards
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Increment Borer
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Increment Core Boring (0.2” diameter)& Resistograph Chart
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Brown Rot Decay
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Post & Beam Style Buildings
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Solid Timber Trusses
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Lattice Web Bowstring Trusses
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These Bowstring Trusses Can Be Up to 100’ Span
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Polling Question
Recommended strength design values are derived from the 5th percentile of tested values?
True
False
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Similar Approach Applied toWaterfront Structures & Foundation Piles
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Waterfront Structures & Foundation Piles
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“Submerged wood will not rot or decay because of lack of air”
Wrong ,Wrong, Wrong, Wrong !!!!!
Over the last 30 years Wood Advisory Services, Inc developed a procedure to test pier & foundation piles to:
Determine Current Structural Capacity & Future Utility
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QUESTIONS?
This concludes The American Institute of Architects Continuing Education Systems Course
American Wood [email protected]
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THE EVALUATION OF RECOMMENDED ALLOWABLE DESIGN PROPERTIES
FOR EXISTING STRUCTURES
Al De Bonis, Ph. D.
Wood Advisory Services, Inc.
PHONE: 845-677-3091
WEBPAGE: www.woodadvisory.com
EMAIL: [email protected]
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