tall wood structures: fire-resistance design primer for ......6/12/2018 copyright © 2018 american...

6/12/2018

Copyright © 2018 American Wood Council1

Tall Wood Structures: Fire-Resistance Design Primer for Mass TimberDES602-1

James Smith, PEMidwest Region ManagerAmerican Wood Council

Fire-Resistance Design Primer for Mass Timber Construction2

Participants may download the presentation here: http://www.awc.org/education/resources

The American Wood Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider # 50111237.

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.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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COURSE DESCRIPTION

This presentation examines how fire resistance ratings in the 2015 International Building Code (IBC) apply to mass timber and heavy timber construction. Topics include how the IBC incorporates fire testing and calculation methods to quantify fire resistance as well as how various materials, including wood, behave when exposed to high temperatures in fires. Discussion will include code compliant calculation methods for fire resistance ratings of wood frame assemblies and for wood members exposed to fire per the 2015 National Design Specification® (NDS®) for Wood ConstructionChapter 16. Mass timber fire resistance ratings when fully exposed or provided with some degree of noncombustible protection is addressed based on current and proposed future code provisions. Also included is information on fire testing, practical considerations for navigating 2015 IBC Chapter 7 on fire and smoke protection features, and an introduction to cross laminated timber (CLT).


LEARNING OBJECTIVESUpon completion, participants will be better able to:

Visualize how mass timber and heavy timber building elements behave when subjected to fire.

Understand basic methods to achieve fire resistance ratings in the 2015 IBC.

Learn how fire resistance ratings of wood assemblies and mass timber are calculated.

Utilize an introduction to CLT as incorporated in the 2015 IBC along with future code change concepts to form a basis of understanding about taller and larger timber structures.

1 3

2 4

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POLLING QUESTION

1. What is your profession?

a) Architect

b) Engineer

c) Building Official

d) Fire Official

e) Other


IBC PRINCIPLES FOR HEAVY TIMBER AND MASS TIMBER

Cross-laminated timber

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CANADIAN PROJECTS

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Image courtesy of Fast + Epp

Fire-Resistance Design Primer for Mass Timber Construction1 0

MASS TIMBER FIRE TESTING

CLT Test Report WP-1950

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Outline• IBC principles – heavy timber and mass timber• ICC Tall Wood Building Ad Hoc Committee proposals• Mass timber fire testing



Noncombustible(703.5)

≠Fire resistant

(703.2 and 703.3)

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Heavy timber fire resistance=

minimum prescriptive dimensions


TYPE IV HEAVY TIMBER

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FIRE RESISTANCE RATING METHODS

Methods for establishing fire resistance (703):1. Tested fire assembly (ASTM E119 or UL 263)2. Fire-resistance designs documented in approved sources3. Prescriptive assemblies using fire-resistance rated designs

in Section 7214. Calculation of fire-resistance per Section 7225. Engineering analysis based on a comparison of building

element, component or assembly designs that have been tested

6. Alternative protection methods per Section 104.117. Fire-resistance designs certified by an approved agency


Wood at high temperature- low thermal conductivity- dimensionally stable- predictable- inner portion remains cool

- does not lose strength

CALCULATED FIRE RESISTANCE

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Chapter 16IBC 722.1 TR-10



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CLT: modified char depth model



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Determination of effective CLT residual cross-section• Assume 5-plies @ 1.5” each ply = 7.5”• Determine thickness for 1-hour rating• achar = 1.8” (NDS Table 16.2.1B)• d = 7.5” – 1.8” = 5.7” • Could conservatively assume 3-ply panel for design

7.5”4.5”



Mass timber fire resistance = minimum dimensions for a

calculated fire resistance; or

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calculated fire resistance; ornoncombustible protection for

the wood; or





the wood; orBOTH

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Waugh Thistleton Architects(Stradthaus – Murry Grove)


FRR of Element = FRR of Wood + FRR of Added Gypsum


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(Traditional heavy timber fire resistance = minimum prescriptive dimensions)



the wood; orBOTH



POLLING QUESTION

2. Calculated mass timber fire resistance can include which of the following?

a) Calculated fire resistance of the woodb) Added fire resistance of noncombustible protectionc) Minimum prescriptive dimensionsd) a) and b)e) a), b), and c)

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ICC TWB PROJECT & COMMITTEE

PROJECT SCOPE

In December 2015, the ICC Board established the ICC Ad Hoc Committee on Tall Wood Buildings noting the purpose of the ad hoc committee is to explore the building science of tall wood buildings and investigate the feasibility of and take action on developing code changes for tall wood buildings.

AD HOC COMMITTEE

The Board has determined that the effort is to be undertaken by the newly formed Ad Hoc Committee on Tall Wood Buildings (AH-TWB). In making the committee appointments, the Board recognized the need to have a consensus committee comprised of the necessary balance of stakeholders including:

• Representatives from building construction material industries

• Building and Fire Officials

• Architects and engineers

• Fire protection experts

• Other construction related stakeholders

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TWB COMMITTEE

• 4 Work Groups appointed• Definitions and Standards• Fire• Structural • Codes

• 82 major issues identified, assigned to specific work groups, and investigated

• Hundreds of reports reviewed and collected via ICC TWB webpage

• Performance Objectives discussed and listed• Develop proposals for 2021 building codes


TWB AD HOC OBJECTIVES

TWB identified performance objectives to be met• No collapse under reasonable scenarios of complete burn-out

of fuel without automatic sprinkler protection being considered• No unusually high radiation exposure from the subject building

to adjoining properties to present a risk of ignition under reasonably severe fire scenarios

• No unusual response from typical radiation exposure from adjacent properties to present a risk of ignition of the subject building under reasonably severe fire scenarios

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TWB AD HOC OBJECTIVES (CONT’D)

TWB identified performance objectives to be met• No unusual fire department access issues• Egress systems designed to protect building occupants during

design escape time, plus a factor of safety• Highly reliable fire suppression systems to reduce risk of failure

during reasonably expected fire scenarios. Degree of reliability proportional to evacuation time (height) and risk of collapse.


TWB AD HOC PROPOSED CHANGES

http://media.iccsafe.org/codes/2018-2019/GroupA/CAH/2018CAH-Complete.pdf

G108-18

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TWB AD HOC PROPOSED CHANGES

awc.org/tallmasstimber

• List of 14 TWB code changes• Proposals Review Guide• Type of Construction comparison• Link to full webinar on changes (DES605)


TWB COMMITTEE PROPOSALS

TYPE OF CONSTRUCTIONTYPE IV-A Mass Timber with noncombustible protection• Noncombustible protection must provide 2/3 of the required Fire Resistance Rating

for Building Elements (Table 601, 602)

• Taller buildings therefore not permitted to have exposed mass timber

TYPE IV-B Mass Timber with portions of noncombustible protection omitted• limits on how much mass timber can be exposed

• limits on how close exposed areas can be to one another

TYPE IV-C Mass Timber with no requirement for noncombustible protection, except certain features

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BUILDING ELEMENT FIRE RESISTANCE RATINGS



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CONCEALED SPACES

No exposed combustibles permitted in concealed spaces . . . other than those allowed by plenum exceptions


TYPE IV-A, IV-B & IV-C EXTERIOR WALL COVERING

Type IV-A, IV-B & IV-CLoad bearing exterior wallAll material outboard of the

Mass TimberMUST BE NONCOMBUSTIBLE

Except: water resistive barrier

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602.4.2.2.4 Separation Distance Between Unprotected Mass Timber Elements. In each dwelling unit or fire area, unprotected portions of mass timber walls and ceilings shall be not less than 15 feet from unprotected portions of other walls and ceilings, measured horizontally along the ceiling and from other unprotected portions of walls measured horizontally along the floor.

Exposed ceiling panels

Exposed wall panels

15 ft separation


IBC SECTION 602.4.3 TYPE IV-C

• Interior faces of mass timber may be all unprotected• Exterior sides of exterior walls must be protected, 40 minutes• Floors must meet Section 804• Concealed spaces must be protected and no combustibles other

than those allowed in a plenum• Shafts must be protected inside and room side with

noncombustible protection of 40 minutes

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ADHESIVES

G108 Revise as follows: 602.4 Type IV. Type IV construction……722.7. All cross-laminated timber shall be labeled as conforming to the heat performance requirements of Sections 6.1.3.4 of DOC PS 1 PRG 320 - 18 as referenced in Section 2303.1.4. and have no delamination in any specimen, except when occurring at a localized characteristic when permitted in the product standard.



703.9 Sealing of Adjacent Mass Timber Elements. In buildings of Type IVA, IVB, and IVC construction, sealant or adhesive shall be provided to resist the passage of air in the following locations:

1. At abutting edges and intersections of mass timber building elements required to be fire resistance-rated

2. At abutting intersections of mass timber building elements and building elements of other materials where both are required to be fire resistance-rated.

Sealants shall meet the requirements of ASTM C920. Adhesives shall meet the requirements of ASTM D3498.

Exception: Where sealant or adhesive is not a required component of a fire resistance-rated assembly.

1705.19 Sealing of Mass Timber. Periodic special inspections of sealants or adhesives shall be conducted where sealant or adhesive required by Section 703.8 is applied to mass timber building elements as designated in the approved construction documents.

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722.7.2 Installation of Gypsum Board Noncombustible Protection. Gypsum board complying with Table 722.7.1(b) shall be installed in accordance with this section.

722.7.2.1 Interior surfaces. Layers of Type X gypsum board serving as noncombustible protection for interior surfaces of wall and ceiling assemblies determined in accordance with Table 722.7.1(a) shall be installed in accordance with the following:

1. Each layer shall be attached with Type S drywall screws of sufficient length to penetrate the mass timber at least 1 inch when driven flush with the paper surface of the gypsum board.

Exception: The third layer, where determined necessary by Section 722.7, shall be permitted to be attached with 1 inch #6 Type S drywall screws to furring channels in accordance with ASTM C-645.

2. Screws for attaching the base layer shall be 12 inches on center in both directions.3. Screws for each layer after the base layer shall be 12 inches on center in both directions and offset from the screws of the previous layers by 4 inches in both directions.



403.3.2 Water supply to required fire pumps. In all buildings that are more than 420 feet (128 m) in building height, and buildings of Type IVA and IVB that are more than 120’ in building height, required fire pumps shall be supplied by connections to not fewer than two water mains located in different streets. Separate supply piping shall be provided between each connection to the water main and the pumps. Each connection and the supply piping between the connection and the pumps shall be sized to supply the flow and pressure required for the pumps to operate.

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FIRE SAFETY DURING CONSTRUCTION



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TYPE OF CONSTRUCTION IV-C

Building Element

Maximum Height 85’

Number of Stories 4 - 9

Exposed Mass Timber Fully Exposed

Sprinklers Yes

Primary Frame FRR 2 hours

Floor FRR 2 hours

Stairs Tower Protected Mass Timber

Concealed Spaces Permitted if protected

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TYPE OF CONSTRUCTION IV-B

Building Element



Exposed Mass Timber Partially

Sprinklers Yes


Floor FRR 2 hours

Fire Resistance from Non-com 80 minutes

Stairs Tower Protected Mass Timber



TYPE OF CONSTRUCTION IV-A

Building Element



Exposed Mass Timber Fully Protected

Sprinklers Yes


Floor FRR 3 hours

Fire Resistance from Non-com 120 minutes

Stairs Tower Non-combustible


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POLLING QUESTION

3. Which of the following NEW types of construction are proposed for the 2021 IBC?

a) Type V-A, Type V-B, Type V-Cb) Type IV-A, Type IV-B, Type IV-Cc) Type IV-A, Type IV-B, Type IV-C, Type IV-HTd) Type I-C, II-C, III-C



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Mass Timber Fire Research

• Purpose: Perform tests of realistic fire scenarios applicable to tall wood construction in order to evaluate occupant and firefighter tenability for egress and suppression efforts, and to provide data necessary to guide further development of relevant code and standard provisions.

• Conducted at U.S. government facilities

• Supervised by U.S. Forest Product Laboratory staff


FIRE RESEARCH

TWB Fire Work Group created fire test scenario• 2-story condo configuration

• 30 feet x 30 feet interior dimensions

• Corridor and stair included

• UL “modern furnishings” fuel load imposed 570 mj/m2

• Fuel load approximated 95th

percentile of Group R fuel loads from survey of Group R’s

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ATF Fire Research Laboratory - 2017



Fire-Resistance Design Primer for Mass Timber Construction

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Apartment Furnishings – Kitchen & Living Room

Photos provided by U.S. Forest Products Laboratory, USDA

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FIRE TEST SCENARIOS

Test Description Date

Test 1 All mass timber surfaces protected with 2 layers of 5/8” Type X GWB 5/23/17

Test 2 30% of CLT ceiling area in living room and bedroom exposed 5/31/17

Test 3Two opposing CLT walls exposed – one in bedroom and one in living

room (there is a partition wall)6/20/17

Test 4All mass timber surfaces fully exposed in bedroom and living room

(NOT bathroom). Sprinklered – normal activation6/27/17

Test 5All mass timber surfaces fully exposed in bedroom and living room

(NOT bathroom). Sprinklered – 20 min delayed activation6/29/17


TEST #1 - ALL MASS TIMBER PROTECTED

All mass timber surfaces protected with 2 layers of 5/8” Type X GWB

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TEST #1 - ALL MASS TIMBER PROTECTED

Fire decayed with no re-ignition





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TEST #2 – 30% CLT CEILINGS EXPOSED

30% of CLT ceiling area in living room and bedroom exposed

Live load applied using water barrels





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http://www.awc.org/tallwood


TEST #3 – EXPOSED WALLS

Two opposing CLT walls exposed – one in bedroom and one in living room


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TEST #4 – SPRINKLER PROTECTED, EXPOSED

All mass timber surfaces fully exposed in bedroom and living room.

Sprinkler –normal activation

Fire suppressed


TEST #5 – DELAYED SPRINKLERS

All mass timber surfaces fully exposed in bedroom and living room

Sprinkler – activation delayed for 20 minutes after smoke detector activation… approximately 23‐1/2 minutes from ignition

Fire suppressed

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Cross-Laminated Timber (CLT)


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POLLING QUESTION

4. Which of the following statements about the ICC TWB Ad Hoc Committee fire tests is correct?

a) Five fire tests were performedb) Fire in CLT test #2 eventually self-extinguishedc) CLT remained structurally sound after fire exposured) Sprinklers put out fire on exposed woode) All of the above

T h i s p r e s e n t a t i o n i s p r o t e c t e d b y U S a n d I n t e r n a t i o n a l C o p y r i g h t l a w s . R e p r o d u c t i o n , d i s t r i b u t i o n , d i s p l a y a n d u s e o f t h e p r e s e n t a t i o n w i t h o u t w r i t t e n p e r m i s s i o n o f A m e r i c a n W o o d C o u n c i l ( A W C ) i s

p r o h i b i t e d . © A m e r i c a n W o o d C o u n c i l 2 0 1 7

in [email protected] | www.awc.org

This concludes the American Institute of Architects Continuing Education Systems Course

tall wood structures: fire-resistance design primer for ......6/12/2018 copyright © 2018 american...

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