Performance-Based Structural-Fire Engineering...Thermal vs. Structural – Thermal criteria is...

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Advanced Technology for Large Structural Systems

© 2017 Spencer E. Quiel, PhD, PE

Performance-Based Structural-Fire Engineering

Spencer Quiel, PhD, PE P.C. Rossin Assistant Professor Lehigh University Bethlehem, PA

OSEA 2017 Fall ConferenceStillwater, OKSeptember 27, 2017


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OSEA 2017 Fall Conference


EDUCATION:– PhD, Structural Engineering, Princeton University (2009)

DHS Graduate Fellow, 2004-2007– BS, Civil Engineering, University of Notre Dame (2004)

EXPERIENCE:– August 2013 to Present:

Assistant Professor, Lehigh University– July 2009 to August 2013:

Project Engineer, Hinman Consulting Engineers, Inc.– Summer 2005: Guest Researcher

Building and Fire Research Laboratory (BFRL), National Institute of Standards and Technology (NIST)

PROFESSIONAL AFFILIATIONS:– ASCE Fire Protection Committee– Professionally Licensed Engineer (PA, VA)

Spencer Quiel, PhD, PE


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Structural Response to Extreme Loads: • How can we design buildings and bridges to be

resistant to the effects of fire and blast?• How do we design structures to resist

disproportionate, catastrophic collapse if they experience local damage?

• How do we design for cascading hazards (i.e. for a fire following a blast or earthquake)?

Research Approaches: • Experimental Testing at the ATLSS and Fritz

Laboratories• High-Fidelity Computational Analysis (Finite

Element Modeling)• Develop Improved Design Standards

Research Interests


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Fire poses a unique threat to the built environment:

Initial extreme event = Fire as primary hazard

Undamaged structure resists fire effects

Following an initial extreme event = Fire as a cascading hazard

Deformed or damaged structure resists the effects of subsequent fire

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Fire as the Primary Hazard1

One Meridian PlazaPhiladelphia, PA (1991)

Delft University School of Architecture Delft, Netherlands (2008)


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Fire as the Cascading Hazard2

Oil Refinery Ichinara City, Japan

Fire Following Tohoku Earthquake(2011)

IRS BuildingAustin, TX

Fire Following Aircraft Impact(2010)


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Current State-of-Practice for Buildings: Resisting Fire as the Primary Hazard• Elements and subassemblies are prescribed levels of passive fire

protection based on the results of standard fire tests

– For generic fire protection:• International Building Code,

UL Fire Resistance Directory, ASCE 29-05

– For proprietary fire protection:• Products are tested according to

appropriate standards, and a report is produced to certify the product

• Test Standards:

– Building Fires: ASTM E119, UL 263, ISO 834– Hydrocarbon Fires: ASTM E1529, UL 1709 Image by Exova Warrington Fire


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ASTM E1529UL 1709EC1 HydrocarbonASTM E119ISO 834

What “Fire” is used for the Standard Fire Test?

Used for relative benchmarking via the standard fire tests

NOT necessarily representative of an actual fire


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Standard Fire Test Procedure

1. Subject elements to a standard temperature-time curve

2. Measure performance based on temperature increase

3. If loaded, evaluate performance based on load resistance and structural integrity

4. Establish relative quantities of fire protection to achieve an hourly rating


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Classifications of Standard Tests for Structural Elements

• Loading Conditions: Loaded vs. Unloaded

– Loaded is more realistic, but alternatives are available to perform an unloaded test which is focused on thermal performance

– According to ASTM E119:

“This load shall be the maximum load condition allowed under nationally recognized structural design criteria unless limited design criteria are specified and a corresponding reduced load is applied.”

• Acceptance Criteria: Thermal vs. Structural

– Thermal criteria is generally considered to be more conservative

• For floor systems: Restrained vs. Unrestrained

– Unrestrained criteria is generally considered to be more conservative


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ASTM E119: What it provides

4.3.1 For walls, partitions, and floor or roof test specimens:

4.3.1.1 Measurement of the transmission of heat

4.3.1.2 Measurement of the transmission of hot gases through the test specimen

4.3.1.3 For loadbearing elements, measurement of the load carrying ability of the test specimen during the test exposure.

4.3.2 For individual loadbearing members such as beams and columns:

4.3.2.1 Measurement of the load carrying ability under the test exposure with consideration for the end support conditions (that is, restrained or not restrained).


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ASTM E119: What it does NOT provide

4.4.1 Information as to performance of test specimens constructed with components or lengths other than those tested

4.4.2 Evaluation of the degree by which the test specimen contributes to the fire hazard by generation of smoke, toxic gases, or other products of combustion.

4.4.3 Measurement of the degree of control or limitation of the passage of smoke or products of combustion through the test specimen.

4.4.4 Simulation of the fire behavior of joints between building elements such as floor-wall or wall-wall, etc., connections.

4.4.5 Measurement of flame spread over the surface of test specimens.

4.4.6 The effect on fire-resistance of conventional openings in the test specimen, that is, electrical receptacle outlets, plumbing pipe, etc., unless specifically provided for in the construction tested. Also see Test Method E814 for testing of fire stops.


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ASTM E119 Test Criteria: Steel Elements• Columns

– Thermal Criteria:

• For loaded or unloaded tests

• Acceptance Criteria: Avg. Temp. < 538°C (1000°F) Max. Temp. < 649°C (1200°F)

– Loaded Tests:

• Simulate the maximum-load condition per design code

• Acceptance Criteria: Column must resist this load over the fire resistance time without collapsing

• Floors and Roofs

– Unrestrained Tests:

• Can be loaded OR unloaded

• Acceptance Criteria: Avg. Temp. < 593°C (1100°F), Max. Temp. < 704°C (1300°F), OR Max. Deflection Limits and Rate

– Restrained Tests:


• Acceptance Criteria: Assembly must resist the load without losing integrity


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Passive Fire Protection for Steel Framed Buildings

BEAM

COLUMN

Spray-On Fire Resistive Material (SFRM)

Gypsum Boards


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Selecting the Amount of Fire Protection

𝑭𝑭𝑽𝑽

=𝑯𝑯𝑯𝑯𝑯𝑯𝑯𝑯𝑯𝑯𝑯𝑯 𝑷𝑷𝑯𝑯𝑷𝑷𝑷𝑷𝑷𝑷𝑯𝑯𝑯𝑯𝑯𝑯𝑷𝑷

𝑪𝑪𝑷𝑷𝑪𝑪𝑪𝑪𝑪𝑪 𝑺𝑺𝑯𝑯𝑺𝑺𝑯𝑯𝑷𝑷𝑪𝑪𝑺𝑺𝑯𝑯𝑺𝑺 𝑨𝑨𝑷𝑷𝑯𝑯𝑯𝑯

Section Factor:


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Intumescent Paint

• Typical Uses:

– Exposed Steel– Thin-Element Steelwork– Harsh Environments– Petrochemical Facilities– Offshore Facilities

• Several coating applications are needed to ensure proper adhesion and heat activation


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Passive Fire Protection: Prescriptive Tables

IBC 2015

UBC 1997

What hourly rating is required?

How much protection is needed to achieve that rating?


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ASTM E119 Test Criteria: Concrete Elements• Columns


• For loaded or unloaded tests

• Acceptance Criteria: Avg. Temp. < 538°C (1000°F) Max. Temp. < 649°C (1200°F)

– Loaded Tests:





• Can be loaded OR unloaded

• Acceptance Criteria: Prestressing Steel < 427°C (800°F), Tensile Reinf. < 593°C (1100°F), OR Max. Deflection Limits and Rate



• Acceptance Criteria: Assembly must resist the load without losing integrity


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AC

I 216

-14


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ASTM E119 Test Criteria: Wood Elements• Columns


• None

– Loaded Tests:





• Typically, only loaded condition


• Acceptance Criteria: Assembly must resist this load over the fire resistance time without collapsing


• Not allowed


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American Wood Council’s

Design for Code Acceptance 3 (AWC DCA-3)

*Combustible elements and assemblies are not

permitted in some construction types


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Prescriptive vs. Performance Based Design

• Prescriptive: states how a building is to be constructed to resist fire

– Uses furnace tests of individual members– Neglects interaction of connected members in a frame

• Performance-Based: states how a structure is to perform in a realistic fire

– Recommended by the NIST investigation of the WTC:

Use realistic loads and boundary conditions

Develop simple methods for analysis


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FIRE MODEL

HEAT TRANSFER

MODELSTRUCTURAL

MODEL

Fire GeometryFuel Load

Section GeometryThermal Properties

Boundary Layer

Member GeometryApplied Loading

Mechanical PropertiesEmpirical Data

Now in Appendix E of ASCE 7-16!!


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NOW AVAILABLE COMING SOON


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• FIRE MODEL– Is the fire inside a compartment or outdoors (i.e. open-air)?– What is the fuel and associated heat release?– What is the rate of fuel consumption?

• HEAT TRANSFER MODEL– What are the thermal boundary conditions?– What are the thermal material properties?– How do neighboring elements transfer heat to each other?

• STRUCTURAL MODEL– How do the material properties deteriorate?– How much do the heated elements expand?– How are the elements connected and/or supported?– How are the elements loaded?

Structural-Fire Engineering


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International Building Code 2015703.3 Alternative methods for determining fire resistance. The application of any of the alternative methods listed in this section shall be based on the fire exposure and acceptance criteria specified in ASTM E119 or UL 263. The required fire resistance of a building element, component or assembly shall be permitted to be established by any of the following methods or procedures:

1. Fire-resistance designs documented in sources. [per the UL catalog]2. Prescriptive designs of fire-resistance-rated building elements, components or

assemblies as prescribed in Section 721. 3. Calculations in accordance with Section 722. [per ASCE 29-05]4. Engineering analysis based on a comparison of building element, component

or assemblies designs having fire-resistance ratings as determined by the test procedures set forth in ASTM E119 or UL 263.

5. Alternative protection methods as allowed by Section 104.11. [requires additional tests as proof of compliance]

http://www.madcad.com.ezproxy.lib.lehigh.edu/library/135051/368074/#section-721http://www.madcad.com.ezproxy.lib.lehigh.edu/library/135051/368075/#section-722http://www.madcad.com.ezproxy.lib.lehigh.edu/library/135051/367984/#section-104.11


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Ts

Qin

Qout

>Tmax1000.00950.00900.00850.00800.00750.00700.00650.00600.00563.00

T=920

T=800

T=620

Compartment Fire Model

FIRE MODELS HEAT TRANSFER MODELS

Lumped Mass

Finite Element

STRUCTURAL MODELS

Single Element

Frame Subassembly

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ASTM E1529UL 1709EC1 HydrocarbonASTM E119ISO 834

Standard Fire Curves


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Open Questions for Performance-Based Design…• What tools should we use for each design scenario?

– Standard Fire vs. Compartment Fire vs. CFD Model– Lumped Mass, Finite Element, etc.

• How should we evaluate the results?

– Does the structure collapse? Is it damaged?– Plastic behavior? Buckling? Connection failure? Compartmentation breach?

• How can we incentivize Performance-Based Design?

– Does it save cost? Does it improve performance? – Does it address designs that are not in the code?– Can we address structural resilience by quantifying damage?


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AISC Milek Fellowship Projectat Lehigh University

Performance-Based Design of Passive Fire Protection for Floor Systems in Steel-Framed Buildings

• Project Objectives:

– Develop of a framework for performance-based design and analysis of floor systems in steel-framed buildings to resist fire

– Adapt, rather than attempt to replace, the prescriptive design provisions that comprise the current state-of-practice

– Enable structural engineers become an active participant in the fire resistant design of steel floor systems

– Provide guidance for quantifying realistic restraint of floor systems in steel buildings


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Mechanical Properties of Steel at Elevated Temperature

AISC 360-10 Appendix 4


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Mechanical Properties of Steel at Elevated Temperature


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Project TasksTask 1: Review Existing Literature and DataTask 2: Computational Model DevelopmentTask 3: Experimental Testing and Validation Task 4: Parametric Computational Investigation Task 5: Develop Framework for Performance-Based Design


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Modular Structural Testing Furnace, ATLSS Laboratory

2 MaxonKinemax

3” Series G Burners


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Composite Floor Tests (Performed 12/12/16 and 2/23/17)

Shear Tab Connection Composite beams designed in

accordance with UL D902

SPECIMEN #1: protected with 7/8” CAFCO 300 SFRM2-hr restrained rating

SPECIMEN #2: unprotected


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Loading Rig for 4-Point Bending 60-kip Enerpac Jack


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Finite Element Models (SAFIR)

Column Section: W10x26Wrapped in ceramic blanketsTemperatures measured during the test are assigned to elements in the furnace

Beam Section: W12x26 with slab (3.25” on 2” deck)

Heated over entire length


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Finite Element Models (SAFIR)ELEMENT SIZES:

• Beam: 1’-0”

• Slab Shell: 1’-0” x 1’-0”

• Beam Shell: 1.5” x 1.5”

BEAM beam elementsSLAB shell elementsCOLN beam elementsCNXNS pinned or fixed

BEAM shell elementsSLAB shell elementsCOLN beam elementsCNXNS semi-rigid (discrete “bolt” elements)


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Protected Composite Floor Test

Test lasted 2 hours, 18 minutes, 45 seconds


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Protected Composite Floor Test

Top bolts sheared during the test due to large connection rotation

Minimal hole warping


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Thermal Results – Protected Test

Ambient Temperature throughout the furnace


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Thermal Results – Protected Test

Beam Temperature Comparison

32232432632832103212321432163218322032

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Web - TestBF - TestTF - TestWeb-SAFIRBF-SAFIRTF-SAFIRWeb - MatlabBF - MatlabTF - Matlab


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Structural Results – Protected Test

Beam deflection – using SAFIR beam temperatures

Column deflection – using SAFIR beam temperatures

Time, sec

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Concrete Structures Under Fire• Large thermal gradients due to low

thermal conductivity

– Lumped mass methods may not be representative of the actual temperature distribution

– Finite element analysis or semi-empirical methods may be needed in some cases


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Coping with Gradients in Concrete Sections


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Siliceous Concrete Reinforcement

Concrete Properties at Elevated Temperature (ACI 216-14)


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Concrete Spalling: How do we account for it?

1996 Channel Tunnel Firehttps://www.sandberg.co.uk/investigat

ion-inspection/inspection/fire-damaged-concrete.html


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Explosive Spalling of a Bridge Beam (test by Propex)https://www.youtube.com/watch?v=gwQfpMnSh90)


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Timber or Wood Structures Under Fire

• LIGHT TIMBER CONSTRUCTION

– Walls, joists, and floors are smaller, conventional elements like studs, plywood, and strand board

– Typically residential or low-rise construction with little structural fire protection requirements

• HEAVY TIMBER CONSTRUCTION

– Beams, columns, decks, and/or truss members are made from glue-laminated timber or large dimension sawn timber

– “Glulam” members perform similarly as solid sawn-timber elements with the same section

– Low- to mid-rise rise construction with a broader range of fire protection requirements


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Wood Charring: How do we account for cross-section reduction?


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1 mm/min = 2.36 in/hr

Wood Charring: How do we account for cross-section reduction?


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Wood Material Properties at Elevated Temperature

Summarized by Buchanan, A.H. (2002). Structural Design for Fire Safety. Wiley.

Tensile Strength Modulus of Elasticity


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Case Study: SOM’s Tall Timber Tower Design Concept


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Timber Tower: Fire Design Challenges• Tall timber construction cannot comply within the current US prescriptive code

(since the structural system is COMBUSTIBLE)

– Intent of the code must be understood and translated to equivalent requirements via PERFORMANCE-BASED DESIGN

• Fire Design Approaches:

1) Protect structure with non-combustible materials2) Prevent ignition under all possible fire conditions3) Design the structure so the members will self-extinguish and remain fully functional after

charring4) Fire “burn out time” should be considered in developing fire assemblies

• Tests and studies are needed to:

1) Verify that timber elements will self-extinguish2) Establish exposure time for timber elements (i.e. charring rates)


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Moving Forward• Develop new tests with additional modes of realistic restraint and exposure

• Conduct parametric studies

– Section sizes, lengths, loading scenarios– Refine boundary conditions– Introduce realistic or probabilistic fire exposure

• Develop simpler design-basis models

– Compare to test results and FE models– Decrease computational effort to enhance usability

• Develop a performance-based framework which leverages the standard test

– Use the standard test for model benchmarking– Use calibrated models to calculate damage (and resilience) to fire


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THANK YOU

Any Questions?

Special thanks to: AISC Milek Fellowship Lehigh University Amy Kordosky (Degenkolb, San Francisco) Matt Hoehler and Matt Bundy (BFRL-NIST)

Slide Number 1Spencer Quiel, PhD, PEResearch InterestsSlide Number 4 Fire as the Primary Hazard Fire as the Cascading HazardCurrent State-of-Practice for Buildings: �Resisting Fire as the Primary HazardWhat “Fire” is used for the Standard Fire Test?Standard Fire Test ProcedureClassifications of Standard Tests for Structural ElementsASTM E119: What it providesASTM E119: What it does NOT provideASTM E119 Test Criteria: Steel ElementsPassive Fire Protection for Steel Framed BuildingsSelecting the Amount of Fire ProtectionIntumescent PaintPassive Fire Protection: �Prescriptive TablesSlide Number 18Slide Number 19Slide Number 20ASTM E119 Test Criteria: Concrete ElementsACI 216-14ASTM E119 Test Criteria: Wood ElementsAmerican Wood Council’s �Design for Code Acceptance 3 (AWC DCA-3)Prescriptive vs. Performance Based DesignPerformance-Based Structural-Fire EngineeringSlide Number 27Structural-Fire EngineeringInternational Building Code 2015Slide Number 30Open Questions for Performance-Based Design…AISC Milek Fellowship Project�at Lehigh UniversityMechanical Properties of Steel at Elevated TemperatureMechanical Properties of Steel at Elevated TemperatureProject TasksModular Structural Testing Furnace, ATLSS LaboratoryComposite Floor Tests (Performed 12/12/16 and 2/23/17)Composite Floor Tests (Performed 12/12/16 and 2/23/17)Slide Number 39Finite Element Models (SAFIR)Finite Element Models (SAFIR)Protected Composite Floor TestProtected Composite Floor TestThermal Results – Protected TestThermal Results – Protected TestStructural Results – Protected TestConcrete Structures Under FireCoping with Gradients in Concrete SectionsSiliceous ConcreteConcrete Spalling: How do we account for it?Explosive Spalling of a Bridge Beam (test by Propex)�https://www.youtube.com/watch?v=gwQfpMnSh90)Timber or Wood Structures Under FireWood Charring: How do we account for cross-section reduction?Wood Charring: How do we account for cross-section reduction?Wood Material Properties at Elevated TemperatureCase Study: SOM’s Tall Timber Tower Design ConceptTimber Tower: Fire Design ChallengesMoving ForwardTHANK YOU��Any Questions?

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