Performance-Based Structural-Fire Engineering

Transcription

1 Advanced Technology for Large Structural Systems Performance-Based Structural-Fire Engineering Spencer Quiel, PhD, PE P.C. Rossin Assistant Professor Lehigh University Bethlehem, PA Stillwater, OK September 27,

2 Spencer Quiel, PhD, PE EDUCATION: PhD, Structural Engineering, Princeton University (2009) DHS Graduate Fellow, 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) 2

3 Research Interests 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 3

4 Fire poses a unique threat to the built environment: 1 2 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 4

5 1 Fire as the Primary Hazard One Meridian Plaza Philadelphia, PA (1991) Delft University School of Architecture Delft, Netherlands (2008) 5

6 2 Fire as the Cascading Hazard Oil Refinery Ichinara City, Japan Fire Following Tohoku Earthquake (2011) IRS Building Austin, TX Fire Following Aircraft Impact (2010) 6

7 Current State-of-Practice for Buildings: Resisting Fire as the Primary Hazard Performance-Based Structural-Fire Engineering 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 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 7

8 What Fire is used for the Standard Fire Test? Temperature ( C) ASTM E UL EC1 Hydrocarbon 600 ASTM E ISO Time (min) Temperature ( F) Used for relative benchmarking via the standard fire tests NOT necessarily representative of an actual fire 8

9 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 9

10 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 10

11 ASTM E119: What it provides For walls, partitions, and floor or roof test specimens: Measurement of the transmission of heat Measurement of the transmission of hot gases through the test specimen For loadbearing elements, measurement of the load carrying ability of the test specimen during the test exposure For individual loadbearing members such as beams and columns: Measurement of the load carrying ability under the test exposure with consideration for the end support conditions (that is, restrained or not restrained). 11

12 ASTM E119: What it does NOT provide Performance-Based Structural-Fire Engineering Information as to performance of test specimens constructed with components or lengths other than those tested 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 Measurement of the degree of control or limitation of the passage of smoke or products of combustion through the test specimen Simulation of the fire behavior of joints between building elements such as floor-wall or wall-wall, etc., connections Measurement of flame spread over the surface of test specimens 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. 12

13 ASTM E119 Test Criteria: Steel Elements Performance-Based Structural-Fire Engineering 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: Simulate the maximum-load condition per design code Acceptance Criteria: Assembly must resist the load without losing integrity 13

14 Passive Fire Protection for Steel Framed Buildings Gypsum Boards Spray-On Fire Resistive Material (SFRM) COLUMN BEAM 14

15 Selecting the Amount of Fire Protection FF VV = Section Factor: HHHHHHHHHHHH PPPPPPPPPPPPPPPPPP CCCCCCCCCC SSSSSSSSSSSSSSSSSS AAAAAAAA 15

16 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 16

17 Passive Fire Protection: Prescriptive Tables IBC 2015 What hourly rating is required? How much protection is needed to achieve that rating? UBC

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21 ASTM E119 Test Criteria: Concrete Elements Performance-Based Structural-Fire Engineering 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: Prestressing Steel < 427 C (800 F), Tensile Reinf. < 593 C (1100 F), OR Max. Deflection Limits and Rate Restrained Tests: Simulate the maximum-load condition per design code Acceptance Criteria: Assembly must resist the load without losing integrity 21

22 ACI

23 ASTM E119 Test Criteria: Wood Elements Performance-Based Structural-Fire Engineering Columns Thermal Criteria: None 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: Typically, only loaded condition Simulate the maximum-load condition per design code Acceptance Criteria: Assembly must resist this load over the fire resistance time without collapsing Restrained Tests: Not allowed 23

24 American Wood Council s Design for Code Acceptance 3 (AWC DCA-3) *Combustible elements and assemblies are not permitted in some construction types 24

25 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 25

26 Performance-Based Structural-Fire Engineering Now in Appendix E of ASCE 7-16!! FIRE MODEL Fire Geometry Fuel Load Empirical Data HEAT TRANSFER MODEL Section Geometry Thermal Properties Boundary Layer STRUCTURAL MODEL Member Geometry Applied Loading Mechanical Properties 26

27 NOW AVAILABLE COMING SOON 27

28 Structural-Fire Engineering 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? 28

29 International Building Code 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 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 Alternative protection methods as allowed by Section [requires additional tests as proof of compliance] 29

30 Temperature ( C) FIRE MODELS ASTM E1529 UL 1709 EC1 Hydrocarbon ASTM E119 ISO Time (min) Standard Fire Curves Compartment Fire Model Temperature ( F) HEAT TRANSFER MODELS Q in T=800 Q out T s Lumped Mass T=620 T=920 Finite Element >Tmax STRUCTURAL MODELS Single Element Frame Subassembly 30

31 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? 31

32 AISC Milek Fellowship Project at 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 32

33 Mechanical Properties of Steel at Elevated Temperature Performance-Based Structural-Fire Engineering AISC Appendix 4 33

34 Mechanical Properties of Steel at Elevated Temperature Performance-Based Structural-Fire Engineering 34

35 Project Tasks Task 1: Review Existing Literature and Data Task 2: Computational Model Development Task 3: Experimental Testing and Validation Task 4: Parametric Computational Investigation Task 5: Develop Framework for Performance-Based Design 35

36 Modular Structural Testing Furnace, ATLSS Laboratory Performance-Based Structural-Fire Engineering 2 Maxon Kinemax 3 Series G Burners 36

37 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 SFRM 2-hr restrained rating SPECIMEN #2: unprotected 37

38 Composite Floor Tests (Performed 12/12/16 and 2/23/17) Performance-Based Structural-Fire Engineering 38

39 Composite Floor Tests (Performed 12/12/16 and 2/23/17) Performance-Based Structural-Fire Engineering Loading Rig for 4-Point Bending 60-kip Enerpac Jack 39

40 Finite Element Models (SAFIR) Beam Section: W12x26 with slab (3.25 on 2 deck) Heated over entire length Column Section: W10x26 Wrapped in ceramic blankets Temperatures measured during the test are assigned to elements in the furnace 40

41 Finite Element Models (SAFIR) BEAM beam elements SLAB shell elements COLN beam elements CNXNS pinned or fixed ELEMENT SIZES: Beam: 1-0 Slab Shell: 1-0 x 1-0 Beam Shell: 1.5 x 1.5 BEAM shell elements SLAB shell elements COLN beam elements CNXNS semi-rigid (discrete bolt elements) 41

42 Protected Composite Floor Test Test lasted 2 hours, 18 minutes, 45 seconds 42

43 Protected Composite Floor Test Top bolts sheared during the test due to large connection rotation Minimal hole warping 43

44 Thermal Results Protected Test Ambient Temperature throughout the furnace 44

45 Thermal Results Protected Test Temp (cel) Beam Temperature Comparison Time (sec) Temp (F) Web - Test BF - Test TF - Test Web-SAFIR BF-SAFIR TF-SAFIR Web - Matlab BF - Matlab TF - Matlab 45

46 Structural Results Protected Test Performance-Based Structural-Fire Engineering Deflection, mm Pinned 2D Fixed 2D Pinned 3D Fixed 3D Shell Test Data Time, sec Beam deflection using SAFIR beam temperatures Deflection, in Deflection, mm Pinned 2D Fixed 2D Pinned 3D Fixed 3D Shell Test Data Time, sec Column deflection using SAFIR beam temperatures Deflection, in 46

47 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 semiempirical methods may be needed in some cases 47

48 Coping with Gradients in Concrete Sections 48

49 Concrete Properties at Elevated Temperature (ACI ) Siliceous Concrete Reinforcement 49

50 Concrete Spalling: How do we account for it? Performance-Based Structural-Fire Engineering ion-inspection/inspection/firedamaged-concrete.html 1996 Channel Tunnel Fire 50

51 Explosive Spalling of a Bridge Beam (test by Propex) Performance-Based Structural-Fire Engineering 51

52 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 52

53 Wood Charring: How do we account for cross-section reduction? 53

54 Wood Charring: How do we account for cross-section reduction? 1 mm/min = 2.36 in/hr 54

55 Wood Material Properties at Elevated Temperature Performance-Based Structural-Fire Engineering Tensile Strength Modulus of Elasticity Summarized by Buchanan, A.H. (2002). Structural Design for Fire Safety. Wiley. 55

56 Case Study: SOM s Tall Timber Tower Design Concept Performance-Based Structural-Fire Engineering 56

57 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 materials 2) Prevent ignition under all possible fire conditions 3) Design the structure so the members will self-extinguish and remain fully functional after charring 4) Fire burn out time should be considered in developing fire assemblies Tests and studies are needed to: 1) Verify that timber elements will self-extinguish 2) Establish exposure time for timber elements (i.e. charring rates) 57

58 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 58

59 THANK YOU Any Questions? Special thanks to: AISC Milek Fellowship Lehigh University Amy Kordosky (Degenkolb, San Francisco) Matt Hoehler and Matt Bundy (BFRL-NIST) 59