1 General Performance-Based (Engineering) Approach to Life Safety-Fire Protection Dee H. Wong, PhD, PE Advanced Safety & Fire Engineering (ASFE, USA)

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General Performance-Based (Engineering) Approach toLife Safety-Fire Protection

Dee H. Wong, PhD, PE Advanced Safety & Fire Engineering (ASFE, USA)

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Overview

Part A – Fundamental Concepts

• Chapter I Introduction

• Chapter II Prescriptive-Code Approach

• Chapter IIIPerformance-Based Approach

• Chapter IVPBA Goals & Objectives

• Chapter V PBA Designs

• Chapter VIPerformance Criteria

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Overview (cont’d)

Part B – Practicing Approaches & Tools

• Chapter VII QRA and Design Fire-Smoke Scenarios

• Chapter VIII QHA and Fire-Smoke Deterministic Tools

• Chapter IXLocal and US PB Designs

• Chapter X Current ASFE Advances

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Overview (cont’d)

Part C – Review and Conclusions

• Chapter XI Review

• Chapter XII Conclusions

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I. Introduction• This presentation provides some better

understandings/indoctrination on Prescriptive-Based Approach (PCA) and Performance-Based Approach (PBA) than merely “buzzwords”.

• Considered an accompanying presentation to Dr. Leong Poon’s (of Hyder’s Australian Office) AIA CPD Seminar on “Performance Based Fire Safety

Engineering Solutions for High-rise Buildings” in last November, which is design-application oriented.

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I. Introduction (cont’d)

• We will spend some time on elaborating on Part A, which hones in the fundamental, yet extremely important, concepts of the past and current practices (designs, construction, management) in Life Safety and Fire Protection (LS-FP).

• Then, in Part B, we will very quickly showcase some of the prevalent scientific-engineering practices, approaches and tools in LS-FP.

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I. Introduction (cont’d)

• In Part A, we will delve into some of the subtleties, distinctions, as well as the pros, cons and relationships, of PCA and PBA.

• In Part B, quantitative hazard and risk assessments, tools, and their local and international designs and methodologies, are highlighted.

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I. Introduction (cont’d) • Prescriptive-Based Code is a code or standard that

prescribes fire safety for a generically used application. Firesafety is achieved by specifying certain construction characteristics, limiting dimensions, or protection systems without referring how these requirements achieve a desired fire safety goal.

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I. Introduction (cont’d)• A Performance-Based Design is an engineering

approach emphatically predicated upon:

– Established fire safety goals and objectives– Deterministic-stochastic analysis of fire-smoke

scenarios– Applications of deterministic-stochastic tools to

evaluate performance criteria dictated by PB designs hence their goals and objectives

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II. Prescriptive-Code Approach

What is a Prescriptive-Code Approach (PCA)?

• The designs, construction, measures, provisions and programs of both Life Safety and Fire Protection (LS-FP) must conform to sets of so-called legally prescriptive codes, which are commonly known as Codes of Practice such as Building and Fire Codes, Rules, Regulations and Ordinances.

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II. Prescriptive-Code Approach (cont’d)

Applicable Building Codes of Practice (COP) are:• Oil Storage Installations (1992)• Guide to Fire Safety Design for Caverns (1994)• The Provision of Means of Escape (MOE) in case

of Fire (1996)• Fire Resisting Construction (1996)• COP for the Provision of Means of Access for

Firefighting and Rescue Purposes (2004)

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Applicable prescriptive Fire Ordinances/COP are:• Fire Safety (Buildings) Ordinance Chapter 573• Fire Safety (Commercial Premises) Ordinance

Chapter 502• FS Ordinance Chapter 95B on Fire Services

(Installations & Equipment) Regulations• FS Ordinance Chapter 295 Dangerous Goods • FS COP for Minimum Fire Services Installations

(FSI) & Equipment (Note: The “Red” Book.)

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International counterparts of conventionally prescriptive codes, say, in USA:

• International Building Code (ICC*)• International Fire Code (ICC*)• International Electrical Code (ICC*)• International Mechanical Code (ICC*)• International Fuel Gas Code (ICC*)• International Energy Conservation Code (ICC*)(* International Code Council, Inc., Falls Church, Virginia, USA)

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An additional American counterpart of prescriptive-code authoring/ publishing authority NFPA*:

• NFPA 5000 Building Construction & Safety Code• NFPA 101 Life Safety Code• NFPA 70 National Electrical Code• NFPA 13 Installation of Sprinkler Systems• NFPA 72 Fire Alarm Code• NFPA 251 (Series)/ASTM E119 Standard Methods of Tests of Fire

Endurance of Building Construction and Materials• NFPA 255/ASTM E84 Standard Method of Test of Surface Burning

Characteristics of Building Materials• NFPA 20 Standard for the Installation of Stationary Fire Pumps for

Fire Protection(* National Fire Protection Association, Quincy, Massachusetts, USA)

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Summary of PCA’s framework or universally salient attributes predominantly dictating PCA’s measures and provisions:

Construction Type/Classification• Occupancy-Facility Type/Classification• Facility/Site area (i.e., footprint)• Occupying ground and aggregate building floor areas• Number of levels or stories (under & above grade)• Internal extents and magnitudes of hazards• External or exposure hazards• Occupant loads and densities

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Summary of PCA’s generic plan of attack:

A. Qualified/Adequate Passive Components• Maximizing fire endurance (thermal-structural integrity)

of building construction/materials upon thermal shock • Maximizing fire resistive compartmentation • Minimizing number and cross-sectional areas of both

vertical and horizontal (yet non-egress) openings• Minimizing flame spread and toxicological productions

from structural assemblies/building materials including interior finishing, accommodations and contents

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B. Qualified/Adequate Means of Egress (MOE)• Functions of construction-occupancy types, and partial-

aggregate occupant loads and densities• Maximizing number of MOE/exiting/evacuation routes

and exits• Maximizing MOE widths• Maximizing MOE fire-smoke protective measures• Adequate evacuation or available egress times• Large-safe internal, external, or both, refuges

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C. Qualified/Adequate active components• Providing full-coverage automatic fire suppression

• Providing full-coverage automatic fire detection-alarm

• Providing automatic smoke control

• Providing a legitimate fire command post and 24-hour fire-security monitoring surveillance

• Providing onsite emergency response team

• Facilitating Fire Services (FS) deployment

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III. Performance-Based Approach

Fundamentally, what exactly is a so-called “Performance-Based Approach (PBA) in a nutshell?

• PBA is a scientifically rigorous-anchored approach comprising the following two major camps.

• The first camp is stochastic, probabilistic or Quantitative Risk Analysis/Assessment (QRA).

• The second camp is deterministic or Quantitative Hazard Analysis/Assessment (QHA).

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III. Performance-Based Approach (cont’d)

Fundamentally, what exactly is a so-called “Performance-Based Approach (PBA)?

• By combining QRA and QHA camps (hence their scientific-engineering tools), PBA quantifies the extents and magnitudes of fire hazards and their concomitant risks.

• Then, the qualified analyst (modeler, consultant, engineer) recommends the necessary, yet optimal and alternate, sets of “technical” mitigating resolutions to the charged micro- or macro-stakeholder, who makes all the ultimate technical-legalistic-financial-political decisions.

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Locally, what is the governing document for PBA?

• 1998 PNAP (Practice Note for Authorized Persons and Registered Structural Engineers) 204: Guide to Fire Engineering Approach

published by the Building Department.

(Note: Recently BD has been reviewing Arup Fire 6-year HKD0.6B consultancy study on PBA; and pushing a legitimate Performance-Based Engineering Fire Code though scheduled to materialize in 2004.)

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Internationally, what are the governing documents for PBA?

• ICC Performance Building and Fire Codes• The SFPE (Society of Fire Protection Engineers,

USA) Engineering Guide to Performance-Based Fire Protection Analysis and Design of Buildings

• BS/ISO/PD 7974 Series: Application of Fire Safety Engineering Principles to the Design of Buildings

• The National Building and Fire Codes of Canada

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Internationally, what are the governing documents for PBA?

• The Australian Performance-Based Fire Code • The Nordic (Swedish) Performance-Based Fire Code• The Singaporean Performance-Based Fire Code• The Japanese Performance-Based Fire Code• 2003 CIBSE Guide E: Fire Engineering

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Other than the Singaporean counterpart, what are the salient differences, to date, between the 1998 PNAP (BD) version and the rest of the world?

• The analyst is compelled to foremost demonstrate the equivalency between PCA and PBA, or the betterment by solely adopting PBA.

• Risk assessments (QRA) are, currently and only, allowed in relatively minor or restrictive roles due to lacks of credible loss/failure frequencies. (Note: When BD formally publishes the PBA Fire Code, this may be a whole different ball game.) Regardless, determinism still does, and will, predominate.

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IV. PBA Goals and Objectives

Foremost, we need to know some of the typical PBA goals and objectives:

• Minimizing casualties (i.e., injuries, fatalities and illnesses)• Minimizing financial losses (e.g., property damages, costs)• Minimizing operation/business interruptions (i.e., smooth continuity)• Confining negative environmental impacts (e.g., green, LEED, less wastes)• The famous principle of “ALARA” (as low as reasonably achieved)• Maximizing design flexibility and alternatives (e.g., spaces, aesthetics)

Note: These are “philosophical” targets, which are arbitrarily or analyst-/stakeholder-defined; thereby, indeed subjective, controversial, and deemed an Achilles’ heel of PBA. In other words, how do we cogently define or determine: “Minimizations” including ALARA, and “Maximizations” in the above context? There have been neither consensuses nor unanimities on them.

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IV. PBA Goals and Objectives (cont’d)

Before we proceed any further, let’s clarify some fundamental yet often vague and confusing terminology in QRA and QHA in terms of the PBA goals and objectives:

• Hazards – the numeric temporal-spatial extents and magnitudes of physicochemical phenomena (including thermal, structural, mechanical, electrical, radioactive, biological, and psychological) and the resultant or consequential numeric losses; e.g., casualties, money.

• Risks – strictly the numeric probabilities of the likelihood (occurrences) of the concomitant hazardous sources or impacts.

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What are the Achilles’ heels of PBA? Due to the asymptotic

nature of both hazardous impacts and

associated risks, we may have to expend “infinite” time, effort and

resource in order to achieve a“zero” impact/risk. Therefore,

zero tolerance is only an idealistic goal that can never

be achieved in real life.

H (N)

R (F)

R=riskH=hazard (Resource, Effort)

Fig. Hazard vs. risk magnitudes (European ln-ln F-N Curve)

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On the international scene (stemming from user communities worldwide), the functional guidelines are predicated upon QRAs and its projections or guidance:

• Cost-and-Benefit Ratio (CBR, highly controversial by equating monetary value with number of casualties); e.g., GBP1M per fatality as suggested by the UK HSE in 1998 Reducing Risk

• Statistical approaches; e.g., failure and loss frequencies• The so-called qualitative or quantitative (numeric) Risk

Matrix (Register, Ranking) correlating certain fire hazardous characteristics with some plausible fire risks (statistics)

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IV. PBA Goals and Objectives (cont’d)Say, upon a conglomerate

reflection of technical, financial, legalistic and political factors and considerations, a micro (private, organizational) or a macro (public, societal) stakeholder may establish the following PBA goals and objectives. A fictitious PBA goal-objective profile is tabulated.

Safety Attributes

Per Accident Per Annum

Injuries 5 15

Fatalities 1 3

Short-term

Illness

20 60

Long-term

Illness

10 30

Property Damages

USD50K USD150K

Liabilities USD5M US15M

Downtimes 2 days 6 days

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V. PBA Design Objectives

What are the PBA design objectives?

• The design objectives must be directly translated from the PBA goals and objectives set forth by the charged micro or macro stakeholder (or both) as a marching order.

• In other words, the charged analyst (modeler, consultant, engineer) must wisely cogitate, yet definitely formulate, a set of cogent hazardous-risky (deterministic-stochastic) fire-smoke scenarios that “tangibly” meet all the PBA goals and objectives set forth by the joint micro-macro stakeholder.

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V. PBA Design Objectives (cont’d)

What are the PBA design objectives?

• Nevertheless and unfortunately, such a vitally prudent exercise of formulating any cogent set of PBA design objectives is an exceedingly non-trivial and partial task, potentially open up to all kinds of controversies, biases, rationales, and imaginations.

• The non-triviality stems from that in theory, there are “infinite” fire-smoke scenarios that can plausibly and possibly occur. Hence, how can anyone contend, with 100% confidence, that certain scenarios, but not all others, must or will materialize? The answer is, “No one can.”

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V. PBA Design Objectives (cont’d)

What are PBA design objectives, “typically”?

• On this note, we can easily summarize the so-called “universally acceptable” fire-smoke scenarios typically as follows:

– (1) Containment of fire and smoke within the fire compartment of origin– (2) Complete and safe evacuation of all occupants, if feasible– (3) Avoidance of any flashover, if feasible– (4) Continuity of structural integrity throughout the entire scenario– (5) Avoidance of any adjacent exposure fire-smoke hazards– (6) Facilitation of emergency or FS deployments– (7) Full protection of selected exposed targets (e.g., humans, and critical

structure equipment, commodities and operations) in terms of threshold fire-smoke scientific-engineering sustainability or damageability

• Designers are free to design anything, with the maximum flexibility and freedom, as long as the above safety design

objectives are all“ demonstrated”!

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VI. Performance Criteria

What are the “typical” scientific-engineering performance criteria?

• Thermal effects (e.g., 2.5 kW/m2 3rd degree burn; 12.5 kW/m2 wood ignition; 700oF steel losing 35% of its yield strength)

• Toxicological effects (e.g., narcotic incapacitation in 30

• minutes – 3000 ppm CO; 135 ppm HCN; 10% CO2 by vol)

• Visibility (say, under smoke obscuration, still reading an emitting exit sign 10 m away through an opaque smoke layer)

• Flame spread rates (0.5 m/s vertically; 0.05 m/s horizontally)

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VI. Performance CriteriaWhat are the “typical” scientific-engineering performance criteria?

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VI. Performance Criteria (cont’d)

What are the “typical” scientific-engineering performance criteria?

• Pro (upside): Once the PBA design objectives have been established, then the PBA performance criteria should “naturally” follow in the above generic categories; i.e., thermal, structural, toxic, visibility, and spread.

• Con (downside): There have no universal consensus as to exactly what these stipulated performance criteria are, analogous to the previous PBA goals and objectives, thereby “negotiable” and often controversial.

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VII. QRA and Design Fire-Smoke Scenarios

Although Hong Kong and some other regional jurisdictions are not conducive to QRA due to their “comfort zones” with a risk-oriented approach, QRA does, and should, play a pivotal role in a cogent PBA, because:

• (1) Qualitatively, QRA serves as a useful “big picture” and roadmap to securing the design objectives

• (2) Utilized wisely and appropriately, QRA does and can optimize the overall (not only LS-FP) design and construction while maximizing design flexibility and alternatives (freedom)

• (3) QRA systematically addresses all credible fire-smoke (hazard-risk) scenarios, thereby rooting out any non-credible or unlikely scenarios.

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VII. QRA and Design Fire-Smoke Scenarios (cont’d)

Typical QRA or risk tools in PBA are:

• FME(C)A (Failure Mode Effect and Criticality Analysis)

• HAZOPs (Hazard and Operability studies)

• Event Tree Analysis (ETA)

• Fault Tree Analysis (FTA)

• Failure, Success, and Reliability Analyses

• Static and Dynamic Markov Chain Analyses

• Markov-Chain Monte Carlo Simulations

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VIII. QHA and Fire-Smoke Deterministic Tools

Typical, and prevalently adopted worldwide, QHA Fire-Smoke deterministic tools in PBA are (http://www.fire.nist.gov):

• Empirical (e.g., FMRC-NIST Ceiling Jet)• Semi-Empirical (e.g., NIST 2-zoned CFAST)• Theoretical/Numerical/Computational (e.g.,

CFD – NIST FDS) Parallel PC/Supercomputer• Physical-Psychological Evacuation Models

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VIII. QHA and Fire-Smoke Deterministic Tools (cont’d)

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NIST Semi-Empirical CFAST Two-Zoned Model

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NIST

Semi-Empirical

CFAST

Two-Zoned

Model(Incompressible

Bernoulli’s Eqn. and

Neutral Pressure Planes)

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NIST

Theoretical

CFD Heat-Mass

Transfer

FDS

(Fire Dynamics

Simulator)

Continuity Eqn.

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NISTTheoreticalCFD Heat-Mass Transfer FDS(Fire Dynamics Simulator)

Energy & StateEqns.

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Large Eddy Simulation Eqns.

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Direct Numerical Simulation Eqns.

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NIST

Theoretical

CFD Heat-Mass

Transfer

FDS

(Fire Dynamics

Simulator)

Low (Mach Number)

Speed Thermally

Driven Flow Eqns.

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Tensorial Momentum Eqn.

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NIST

Theoretical

CFD Heat-Mass

Transfer

FDS

(Fire Dynamics

Simulator)

Scalar Poisson

Pressure Eqn.

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NIST

Theoretical

CFD Heat-Mass

Transfer

FDS

(Fire Dynamics

Simulator)

Combustion-Radiation

Submodels

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Sprinkler-DetectorInteractive Submodels

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Sources from: FLUENT; Adaptive Researchwebsites

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Evacuation Simulations & Modeling Sources: SIMULEX (Crown Dynamics); EXOUS (Univ of Greenwich); EVACNET4 (Univ. of Florida)

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Evacuation Simulations & Modeling Sources: SIMULEX (Crown Dynamics); EXOUS (Univ of Greenwich); EVACNET4 (Univ. of Florida)

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IX. Local and US PB Designs

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IX. Local and US PB Designs (cont’d)

The fundamental HK design methodology:• Means of Escape (MOE)• Design Fires (highly controversial)• Smoke Control• Structural Performance• Suppression/Sprinkler Systems• Detection-Alarm Systems• Onsite Emergency Response Team• Facilitation of FS Deployment• Emergency Lighting and Evacuation Signs

Note: Unlike their US/EU counterparts, they are remarkably parallel with the current “Prescriptive-Code” Approach!

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t-Squared Fire Curves Design Fires

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NFPA Fire Safety (Design, Const, Mgmt) Concepts Tree

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In short, the salient differences between HK and US approaches are:

• HK PB approach is “still and more” prescriptive-code oriented; and

• US PB approach is more risk and less prescriptive-code oriented.

Note: That’s why it’s so important to be dexterous in both prescriptive and performance approaches.

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X. ASFE Current Advances

There are a few internal research programs that ASFE prides, potentially advancing the art and science of Life Safety and Fire Protection Science and Engineering:

• 3-D Serendipity Quadratic-Cubic Finite Element Radiative Heat Fluxes for Exposed Fire Damageability (FLUX3D)

• Hybrid Zonal Network Platform (ZNP®*) and CFD Low Speed Thermally Driven Flows

• HARA®*: Combined Quantitative Hazard and Risk Assessment for Micro and Macro Spaces and Environs

(* Pending US Registered Trademarks)

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X. ASFE Current Advances (cont’d)

3-D Serendipity Quadratic-Cubic Finite Element Radiative Heat Fluxes for Exposed Fire Damageability for indoor/outdoor exposed targets

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X. ASFE Current Advances (cont’d)3-D Serendipity Quadratic-Cubic Finite Element Radiative Heat Fluxes for Exposed

Fire Damageability for indoor/outdoor exposed targets

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Zonal Network Platform (ZNP)for Combined Zoned and CFDLow Speed Thermally DrivenFlows & Fire-Smoke Simulations

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Zonal Network Platform (ZNP) for Combined Zoned and CFD Low Speed Thermally Driven Flows & Fire-Smoke Simulations

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Zonal Network Platform (ZNP)for Combined Zoned and CFDLow Speed Thermally DrivenFlows & Fire-Smoke Simulations

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HARA (QHA-QRA) Platform

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XI. ReviewUpon this presentation, we should reflect upon:

• What is a general notion of Prescriptive-Based Approach (PCA)?

– PCA, conventional Codes of Practice or COP, is a set of a priori empirically prescribed constraints and requirements without knowing whether or how the Life Safety-Fire Protection goals and objectives are desirably met or not.

• What is a general notion of Performance-Based Approach (PBA)?

– PBA is Life Safety-Fire Protection goal-objective oriented– Scientific-Engineering; deterministic-stochastic based

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XI. Review (cont’d)Upon this presentation, we should reflect upon:

• What is a general notion of Prescriptive-Code or –Based Approach (PCA)?

– PCA, conventional Codes of Practice or COP, is a set of empirically prescribed constraints and requirements without knowing whether or how the Life Safety-Fire Protection goals and objectives are desirably met or not.

• What is a general notion of Performance-Based Approach?– PBA is Life Safety-Fire Protection goal-objective oriented– Scientific-Engineering; deterministic-stochastic based

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• What is Quantitative (Fire-Smoke) Hazard Assessment (QHA)?

– QHA quantifies the extents and magnitudes of physicochemical (e.g., thermal, electrical, structural, mechanical, radioactive) phenomena or effects of fire-smoke sources and impacts onto their environs.

• What is Quantitative (Fire-Smoke) Risk Assessment (QRA)?

– QRA quantifies the numeric probabilities of the likelihood of the occurrences of (fire-smoke) hazard.

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• Qualitatively, what are the common essences between PCA and PBA?

– Containment of fire and smoke within the fire compartment of origin– Complete and safe evacuation of all occupants, if feasible– Avoidance of any flashover, if feasible– Continuity of structural integrity throughout the entire scenario– Avoidance of any adjacent exposure fire-smoke hazards– Facilitation of emergency or FS deployments– Full protection of selected exposed targets (e.g., humans, and critical

structure equipment, commodities and operations) in terms of threshold fire-smoke scientific-engineering sustainability or damageability

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XI. Review (cont’d)

Upon this presentation, we should reflect upon:

• Qualitatively, PBA emphasizes:– Meeting LS-FP goals and objectives

– Providing maximum degrees of design freedom

– Utilizing QRA to root out unlikely or statistically improbable (say, 10-4 per annum) fire-smoke design scenarios

– Adopting state-of-the-art deterministic design-analyzing tools

– Optimizing finitely scarce mitigating resources

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• Typical deterministic tools are:– Empirical models (e.g., FMRC-NIST Jet Flow)– 2-zoned semi-empirical (e.g., NIST CFAST)– Theoretical (Numerical, Computational, CFD)

(e.g., NIST FDS)• Other tools are:

– FLUX3D (Finite Element Fire Damageability)– ZNP (Zonal Network Platform; combined zoned-CFD)– HARA (Hybrid Hazard-Risk Analysis)

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XI. Review (cont’d)

Upon this presentation, we should reflect upon:

• Finally, what “exactly” are the Performance Criteria?– Thermal Effects– Structural Effects– Toxicological Effects– Visibility– Flame Spread Rates (horizontally & vertically)

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XII. ConclusionsThis presentation briefly introduces the history and

current advances, techniques and applications of Life Safety and Fire Protection Science and Engineering.

We hope the audience, after this presentation, has a little bit better understanding on Prescriptive and Performance codes and approaches, in order to ask more intelligent questions on this vital issue next times.

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XII. Conclusions (cont’d)We gratefully thank Hyder Consulting for recognizing

the importance and emergence of these critical safety advances and issues in our design profession.

Now the floor is open to any questions, comments and discussions.

Last but not the least, thank you all for your time.

Be Design-Safe!

Documents

1 General Performance-Based (Engineering) Approach to Life Safety-Fire Protection Dee H. Wong, PhD, PE Advanced Safety & Fire Engineering (ASFE, USA)