CLT Adhesive Tests in Support of Mass Timber Buildings€¦ · CLT Adhesive Tests in Support of Mass Timber Buildings DES604 Jason Smart, P.E. Manager, Engineering Technology American

CLT Adhesive Tests in Support of Mass Timber Buildings

DES604

Jason Smart, P.E.Manager, Engineering TechnologyAmerican Wood Council

Sam Francis, C.B.O.Senior Director, National ProgramsAmerican Wood Council

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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

Adhesive bonding of wood laminations allows for the manufacture of large wood members. Adhesives used for this purpose must meet specified levels of resistance to heat at elevated temperatures. This performance is determined through testing. Code-referenced standards currently require such adhesives to pass a bond line shear test at elevated temperatures as a demonstration of this performance. The presentation will include an overview of the manufacturing of glued engineered wood products and the applicable code-referenced standards. During the work of the ICC Tall Wood Building Ad Hoc Committee (TWB), special test programs were developed and performed with the input of the fire service. New test protocols were developed to ensure the adhesive used in cross-laminated timber (CLT) will not result in the re-kindling of uncharred wood at the bond line. Background and the resulting test protocol for CLT will be presented.

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LEARNING OBJECTIVES

Upon completion, participants will be:

Recognize how cross-laminated timber and other glued engineered wood products are manufactured.

What is CLT?

Describe the compartment fire test results and circumstances that led to the development of a full-scale room fire protocol for qualifying adhesives used to manufacture cross-laminated timber.

Compartment Tests

Summarize the test protocols and associated pass/fail criteria established in PRG 320 for qualifying adhesives and evaluate their impact on mass timber construction.

Adhesive Qualification Tests

Understand the proposed code change that addresses the performance requirements for cross laminated timber, and state its impact on mass timber construction.

Applicable Code Requirements

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POLLING QUESTION

1. What is your profession?

a) Architect

b) Engineer

c) Building Code Official

d) Fire Code Official

e) Other

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Outline

• What is CLT?

• Compartment Tests

• Adhesive Qualification Tests

• Applicable Code Requirements

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CONCEPT OF CROSS-LAMINATED TIMBER

Photos provided by FPInnovations

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CROSS LAMINATED TIMBER PANELS

CONCEPT OF CROSS-LAMINATED TIMBER

Photo provided by FPInnovations

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MASS TIMBER CONCEPT - HISTORY OF CLT

1985 1st CLT patent - France

1993 1st CLT projects - Switzerland and Germany

1995-1996 Improved press technology

1998 1st multi-story res building - Austria

Early 2000’s

CLT use (Europe) increased significantly

Green building movement driven

Better efficiencies, product approvals, improved marketing and distribution channels

Over 500 CLT buildings in England

Recent - US and Canadian use of CLT

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CLT VS GLT

Beam-like memberThick Orthotropic Plate

Graphics provided by WoodWorks Graphics provided by APA

Cross Laminated Timber Glued Laminated Timber

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CROSS-LAMINATED TIMBER

Graphics provided by WoodWorks

Components of CLT

• A lamination consists of a piece of sawn lumber or SCL

• Layer: An arrangement of laminations of the same thickness, grade, and species combination laid out essentially parallel to each other in one plane

• CLT consists of at least 3 orthogonal layers, laminated with structural adhesives

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POLLING QUESTION

2. Which of the following is true regarding CLT?a.All laminations within a single layer are parallel

b.Alternating layers are perpendicular

c. There is a major and minor axis

d. All of the above

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Outline

• What is CLT?

• Compartment Tests

• Adhesive Qualification Tests

• Applicable Code Requirements

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COMPARTMENT TESTS

What is a Compartment Fire Test?

• A fire test within a compartment having at least one opening

• Simulates a flashover fire in an actual room or apartment

• Fuel type: Either real furnishings, gas or other combustible fuels

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FIRE TESTING: COMPARTMENT TEST VS. ASTM E119

Compartment Fires:

• Temperatures typically peak more quickly and remain higher than E119 standard fire test during fully-developed phase

• Temps start to decrease once fuel is mostly consumed (decay phase)

E119 Standard Fire:

• Temperatures gradually increase throughout exposure

• It takes >4 hours for the temperature to reach the same level as the typical peak temp in a compartment fire

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NFPA FPRF COMPARTMENT TESTS

NFPA Fire Protection Research Foundation (FPRF)

• Tests done for NFPA’s Property Insurance Research Group (PIRG)

• Purpose: Evaluate the contribution of CLT elements to compartment fires to collect data for insurance modeling

• Tests performed by NRC Canada

• Tests performed at NIST facilities

• 6 Compartment tests:

• 2 with all CLT protected

• 4 with various surfaces exposed

• Report available at FPRF website:

https://www.nfpa.org/News-and-Research

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NFPA FPRF COMPARTMENT TESTS

• No significant contribution of CLT when all surfaces were protected with Type X gypsum wallboard

• Where surfaces were exposed, CLT contribution increased with increasing exposed CLT surface area

• Modeling performed by Research Institute of Sweden (RISE) was close to measured results

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NFPA FPRF COMPARTMENT TESTS

• Fire re-growth observed in multiple FPRF tests

• Fire re-growth caused by failure of bond lines before being reached by char front (i.e., heat-delamination)

Images courtesy of Joseph Su, NRC Canada

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NFPA FPRF COMPARTMENT TESTS

Test 1-4: Exposed CLT ceiling

• 1st heat-delamination occurred around 50 minutes, extending fully-developed phase

• 2nd heat-delamination occurred around 150 minutes, resulting in fire re-growth

Graphs courtesy of Joseph Su, NRC Canada

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https://youtu.be/re7_yEILvtg

NFPA FPRF COMPARTMENT TESTS

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NFPA FPRF COMPARTMENT TESTS

• Similar fire re-growth behavior observed in other compartment tests with exposed areas of CLT

• All instances of fire re-growth were caused by adhesive heat delamination

Result of this behavior

• Fire may not necessarily burn out after compartment contents are consumed

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POLLING QUESTION

3. In the FPRF compartment tests, all instances of fire re-

growth were caused by adhesive heat delamination.

True

False

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Outline

• What is CLT?

• Compartment Tests

• Adhesive Qualification Tests

• Applicable Code Requirements

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ADHESIVE QUALIFICATION TESTS

Position of ICC-TWB Ad-Hoc Committee

• Heat delamination leading to fire re-growth deemed unacceptable for Tall Mass Timber buildings

• Members should perform more like solid wood

✓ Steady, predictable char development

✓ Unheated core insulated by char layer

✓ No fire re-growth

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ADHESIVE QUALIFICATION TESTS

Direction provided by ICC-TWB Ad-Hoc Committee

• Need test protocol capable of identifying heat-delaminating adhesives

• Code-referenced standards governing CLT should require adhesive qualification using this protocol

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ADHESIVE QUALIFICATION TESTS

Test protocol developed by Southwest Research Institute (SwRI)

• Large-scale compartment test (9’ x 19’ compartment)

• Exposed CLT ceiling (as was tested in FPRF Test 1-4)

• Same CLT span as in FPRF tests (~15’)

• Same loading as in FPRF tests (20 psf)

• Same ventilation ratio as in FPRF tests (~0.03 m0.5)

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ADHESIVE QUALIFICATION TESTS

Large-scale Compartment Test Protocol

• Calibration of adhesive qualification test protocol

• Exposure replicates conditions of FPRF baseline test (FPRF Test 1-1)

• Exposure based on heat flux to the ceiling to replicate fire curve of FPRF Test 1-1 (no exposed CLT)

FPRF Test 1-1 Adhesive qualification calibration test

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ADHESIVE QUALIFICATION TESTS

Prior to flashover (11 minutes) Flashover (~14 minutes)

Large-scale Compartment Test Protocol

• Validation of adhesive qualification test protocol

• Validation test performed on same CLT used in FPRF tests to verify similar performance

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ADHESIVE QUALIFICATION TESTS

Fully-developed phase (15 minutes) Fully-developed phase (40 minutes)

Large-scale Compartment Test Protocol

• Validation of adhesive qualification test protocol

• Validation test performed on same CLT used in FPRF tests to verify similar performance

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ADHESIVE QUALIFICATION TESTS

Just prior to fire re-growth (2:59) 2nd Flashover caused by fire re-growth (3:10)

Large-scale Compartment Test Protocol

• Validation of adhesive qualification test protocol

• Validation test performed on same CLT used in FPRF tests to verify similar performance

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https://youtu.be/qIR9Ztc7XHQ

ADHESIVE QUALIFICATION TESTS

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ADHESIVE QUALIFICATION TESTS

FPRF Test 1-4 Adhesive qualification validation test

FPRF Test 1-1 Adhesive qualification calibration test

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ADHESIVE QUALIFICATION TESTS

Validation of adhesive qualification test protocol

• Comparison of temperatures at ceiling

• ~450°C during decay phase, before fire re-growth

• ≥800°C at end of test, due to fire re-growth

FPRF Test 1-4 Adhesive qualification validation test

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ADHESIVE QUALIFICATION TESTS

Improved PUR

Heat-delaminating PUR

Qualification tests performed on other adhesives

• Fire re-growth observed with PUR

• No fire re-growth observed with

• Melamine formaldehyde resin

• Improved PUR

• Test identifies acceptable performance

Melamine formaldehyde resin

✓ ✓

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ADHESIVE QUALIFICATION TESTS

Small-scale Adhesive Qualification Test Protocol (CSA O177 Sect. A.2)

• As modified by PRG-320: Cross-section of CLT exposed to flame

• Flame temperature: 1470-1650˚F (800-900˚C)

• Exposure duration: 10 minutes (5 minutes on each side)

Image courtesy of FPInnovations

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ADHESIVE QUALIFICATION TESTS

Small-scale Adhesive Qualification Test Protocol (CSA O177 Section A.2)

• CLT samples cut and inspected for delamination following test

• Distinguishes between adhesives that undergo heat-delamination vs. those that do not

Images courtesy of FPInnovations

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POLLING QUESTION

4. Large-scale compartment tests performed at SwRI revealed:

a. Fire re-growth was observed with tested heat-delaminating PUR

b. No fire re-growth was observed with tested melamine formaldehyde resin

c. No fire re-growth was observed with tested improved PUR

d. All of the above

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Outline

• What is CLT?

• Compartment Tests

• Adhesive Qualification Tests

• Applicable Code Requirements

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APPLICABLE CODE REQUIREMENTS

International Building Code (IBC)

• IBC Chapter 23 requires CLT to be manufactured and identified in accordance with ANSI/APA PRG 320

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APPLICABLE CODE REQUIREMENTS

PRG 320 – Standard for Performance-Rated CLT

• Contains a wide range of requirements for CLT, including

• Dimensions and tolerances

• Component requirements (laminations, adhesive, etc.)

• Performance criteria

• Qualification and marking

• Quality assurance

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APPLICABLE CODE REQUIREMENTS

PRG 320-2018 – Standard for Performance-Rated CLT

• Adhesives must meet the requirements of ANSI 405 (which references CSA O177 Section A.2)

- AND -

• Adhesives must comply with the requirements for elevated temperature performance per Annex B (large-scale compartment test)

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APPLICABLE CODE REQUIREMENTS

Annex B of PRG 320-2018

• Large-scale Compartment Test

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APPLICABLE CODE REQUIREMENTS

Annex B of PRG 320-2018

• Calibration performed on protected CLT (same as FPRF Test 1-1)

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APPLICABLE CODE REQUIREMENTS

Annex B of PRG 320-2018

• Qualification Test Method

• 8’ x 16’ CLT specimen – exposed CLT ceiling

• Specimen subjected to prescribed exposure

• Test performed for a period of 240 minutes (4 hours)

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APPLICABLE CODE REQUIREMENTS

Annex B of PRG 320-2018

• Acceptance Criteria

• CLT assembly must sustain applied load throughout entire 240-minute test

• Temperatures shall not exceed 950˚F (510˚C) during decay phase

• This identifies and excludes adhesives that allow delamination leading to fire re-growth

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POLLING QUESTION

5. Which of the following standards addresses

appropriate CLT adhesive performance for tall mass

timber buildings?a.APA PRG 320-2012

b.APA PRG 320-2015

c. APA PRG 320-2018

d.Any of the above standards are suitable

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