Please add relevant logo here Exposed Wood in Fire Resistive Applications David Barber, Arup Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board.
Please add relevant logo here
Exposed Wood in Fire Resistive Applications
David Barber, Arup
Disclaimer: This presentation was developed by a third party and is not funded by
WoodWorks or the Softwood Lumber Board.
“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.
Course Description
For buildings, the fire resistance of structural elements is a code-stipulated requirement often dictated by the construction type chosen rather than building materials used. Wood structures are unique in that they can be unprotected while still providing a level of fire resistance. However, both designers and jurisdictions tend to be unfamiliar with this approach.
This presentation will cover the use of a variety of exposed structural wood products (solid sawn lumber, nail laminated wood, glue laminated wood and cross laminated wood) in different fire-resistant applications for construction Types III, IV and V. Discussion will include implementation of char calculations, considerations for connections, and information on when calculations or fire tests are required for proving fire resistance in these scenarios. With a better understanding of the challenges and potential solutions, attendees will be able to confidently pursue exposed wood for their projects.
Learning Objectives
1. Review provisions of the International Building Code specific to the
use of unprotected wood products in fire-resistive members and assemblies.
2. Discuss calculation of fire resistance for exposed wood members, including applicability of char calculations.
3. Highlight options and configurations for connections in fire resistance-rated exposed wood systems.
4. Explore design paths for proving fire resistance acceptability of exposed wood systems, including the use of alternative design methods and materials.
Content
� Why wood?
� IBC Requirements
� Fire fundamentals
� Applications to code compliant buildings
� Details
� Summary
USDA: www.tallwoodbuildingcompetition.org
Why wood?
� Sustainability
� Aesthetics, Innovation
� Changing technology
� Efficient construction
� Prefabrication
Current approach
CLT
Glulam
NLT
LVL
Wood Construction and the IBC
Combustible construction – Type III, IV, V
Non-combustible construction – Type I, II
Wood is combustible construction
Code compliant use in Types III, IV, V
Wood Construction and the IBC
Type III:
• Up to 6 stories (B), 5 stories (R)
• 1 hr FRR load bearing structure
• 2hr FRR load bearing external walls
Type IV:
• As for Type III, but using “heavy timber”
Type V:
• Low rise, few restrictions
10
What Does a Type III Building Look Like?
• The
Duratherm Presentation
Podium construction with
concrete to lower floors
Wood floors and
framing (interior)
Exterior walls are non-combustible, or wood
covering (to 40ft) or FRT wood (to 60ft)
Up to 6 floors, with sprinklers
11
What Does a Type IV Building Look Like?
Duratherm Presentation
Exterior walls are non-
combustible, or FRT wood
Up to 6 floors, with sprinklers
Wood beams, columns, floors, roof permitted
12
A Modern Type IV Building
Exposing the wood
Up to 6 floors, with sprinklers
Glulam beams, columns; CLT floors and walls
Use of steel or concrete, where
appropriate (hybrid construction)
Wood Construction and the IBC
Types III, IV, V – wood can be exposed
What is a Fire Resistance Rating?
Structural resistance Integrity Insulation(from “CLT Handbook, US Edition”)
What is Interior Finish Flammability?
Resistance to flame spread and a measure of
smoke development - classes A, B and C
From Nordic ASTM E84 “Standard Test Method for Surface Burning
Characteristics of Building Materials (‘Steiner tunnel’)
What is Interior Finish Flammability?
Type IV - exempt
Wood = Class C
Some wood products will achieve B
AWC Design for Code Acceptance – 1 “Flame spread performance of wood products used for interior finish”
Exposed Wood and Fire
- Questions ?
Exposed wood and fire:What are the issues?
All materials are vulnerable to fire:
Combustibility - Just another engineering problem?
APA
Wood - Fire fundamentals� Charring
� Well understood and researched
Schaffer, 1966, Forest Products Laboratory
Wood - Fire fundamentals
Determination of charring rates
History of fire tests:
� Standard furnace tests
� Tests in real fires
� Carried out internationally
� Correlations based on density, moisture,
grain direction, sawn or engineered wood
Figure 2-2 from TR-10
Wood - Fire fundamentals
Wood performance in fire is predictable
Load carrying under fire is reliable
Design for fire resistance, through
increasing wood cover
Wood has inherent passive fire protection
Wood - Fire fundamentals
Long term (nominal) char rate = 1.5 in/hr
Design char rate increased by 20%:
• Corner rounding
• Fissures
• Zero strength layer behind the char
For 1hr exposure = 1.8in/hr
For 2hrs = 1.58in/hr From APA
Wood - Fire fundamentals
90 minute FRR fire test on 270mm x 415mm glulam beam (from APA)
Wood - Fire fundamentals
Calculating an FRR
What is the area (b x d) needed ?
What additional wood cover is required,
for an FRR (B x D)
The difference (B – b) is the sacrificial
char layer TR-10 Fig 1-2
Wood – Fire guidance
FRR of wood – NDS Chapter 16
Method explained in detail in TR-10
Part 3 provides all required design
information
TR-10 is a compliant methodology for
providing exposed wood FRR
Wood – Fire calculations
� Glulam, LVL, sawn lumber Follow NDS
� CLT Follow NDS
� IBC NDS TR-10Section 722.1 Part 3Chapter 16
Exposed Wood
� Not all authorities are supportive of
exposed wood
� Sometimes an alternative materials
submission is required to support use
� Significant variance in interpretation of
the IBC, with regard to exposed wood
� Type IV construction is the most
straightforward approach
Connections
Can be expressed where no fire rating is required
Where exposed and need a 1 hr FRR:
� Concealed steel plates
� Concealed bolts or dowels
FRR Connections
Design to conceal the whole connection
Provide bearing connections
Some connections will need detailed
analysis
Fire testing for proprietary “off the shelf”
connections is occurring
From Simpson Strongtie
From ETH
CLT Connections
Proven through fire testing
Lap splice
Spline splice
From KLH
CLT
A panelized system for walls and floors
Similar to concrete flat slab construction - no
concealed spaces
Highly accurate construction
All pre-cut and delivered to site
Screw-fixed into place
Very strong and very durable
CLT - Fire fundamentals
Does it char like normal wood?
What is delamination?
Is all CLT constructed the same?
Fire Modelling – Fire Resistance Ratings
1”
1”
β = 1.5”/hr
β = 1.5”/hr
β = 3.0”/hr
β = 1.5”/hr
β = 3.0”/hr
Exposed Wood in Tall Buildings
• What can be engineered?
• Understanding wood performance in fire
• Using existing research and test data
• Engineered calculations
• Encapsulation methods
From dECOi Architects
Questions?
This concludes The American Institute of Architects Continuing Education Systems Course
David Barber
Arup