Post on 14-Mar-2020
Introduction and Fire Dynamics
Ignition and Prevention Factors
Fire Growth / Flame Spread
Fire Suppression, Detection and Alarm
Fire Confinement / Structural Integrity
Smoke Movement / Management
Egress Systems and Tenability Analysis
1. Introduction
Definitions of failure
Failure is an unacceptable difference between expected and observed performance
ASCE Technical Committee on Forensics
Distortion, breakage, deterioration or other fault in an item, component, system, assembly or structure that results in unsatisfactory performance of the function for which it was designed
NFPA 921, Guide for Fire and Explosion Investigations
※ Definition of fire investigation
The process of determining the origin, cause, and development of a fire or explosion
1. Introduction
Classifications of failure
Design
Installation
Inspection, testing and maintenance
Equipment malfunction
Training / operation / administrative controls
Communication
1. Introduction
Origin and Cause issues
Most of the focus in fire investigation is on the
cause of ignition
What started the fire?
Potential cause of action against responsible parties
Was the fire intentionally set (arson)?
Criminal prosecution
Denial of insurance coverage
1. Introduction
Engineering issues
What physical / chemical / operational factors permit a fire or explosion?
What factors permit a small fire to grow large and cause unacceptable damage or injury?
Flammability of materials
Fire detection and alarm notification
Fire suppression
Smoke management / control
Fire confinement / structural integrity
Means of egress
1. Introduction
Role of Codes and Standards
Fire codes and many fire safety standard : Prevention
Fire test/FP system installation standards : Mitigation
Building codes :
Describe fire safety systems and features that should be in place to mitigate the consequences
Reference Fire test/FP system installation standards to assure compliance with the code’s performance objectives
Building codes, Fire codes and many fire safety standard
Are used to evaluate whether an appropriate standard of care has been applied in design, installation, operation and maintenance of building and fire protection systems
1. Introduction
Reasons for post-fire analyses
Identify criminal activity,
Assess responsibilities
Provide feedback for improvements to manufactures, designers and regulators
Reduce risk (insurance)
Identify trends (data)
Learn from past mistake to prevent reoccurrences in the future
Determine Origin and Cause and provide feedback to
Protect property(reduce damages), Save lives and prevent injuries, conduct research to improve codes, standards, regulation, Reduce impact on environment, protect firefighters
2. Fire Dynamics
Stages and elements of enclosure fires
Fire plume/ceiling jet,
Enclosure smoke filling,
Pre-flashover
Post-flashover
Data needs for fire scenario reconstruction,
Fire patterns and their analysis,
Fire Modeling tools, uses and limitations
2. Fire Dynamics
Case study : MGM Grand Hotel Fire (80.11.21)
https://en.wikipedia.org/wiki/MGM_Grand_fire
세 번째로 큰 호텔 화재 : 85명 사망, 650명 부상
화재원인 : ‘The Deli’ Restaurant(소켓의 접지불량)
문제점 : 상주지역(SP 면제:화재시 비상주지역), 가연성물질, 수직 관통부, 연기 확산(HVAC), 비상구잠금
Fire reconstruction is based heavily on issues addressed by FPEs
Large scale fire testing supported has been used.(화재전파속도 : 4.6~5.8 m/s)
Response of materials to fire, Fire pattern analysis,
Fire dynamics / modeling
3. Ignition and Prevention Factors
Introductory concepts : 점화원과 가연물
Fire Origin and cause considerations + propagation
Ignition sources and their control (Che/Mech/Elec)
NFPA 1, 51B, 54, 58, 70, 86, 211
Materials first ignited : 물질 상태(기액고) 및 형상(고)
Thin solids : 𝒕𝒊𝒈 =𝑻𝒊𝒈−𝑻𝒐
𝒒 𝒏𝒆𝒕" /𝝆𝒄𝜹
Thick solids : 𝑡𝑖𝑔 =𝜋
4𝑘𝜌𝑐
𝑻𝒊𝒈−𝑻𝒐
𝒒 𝒏𝒆𝒕"
2
Ignition factors : 설계, 설치, 행정통제,검사 및 기기
오동작
3. Ignition and Prevention Factors
Case study : The Station nightclub fire (03.2.20)
100명 사망, 250명 부상,
화재원인 : 불꽃이 벽마감재에 점화
PU foam as interior finish : Life Safety Code
Use of pyrotechnics without proper permits/training : 행정통제
Overcrowding / exit capacity / arrangement
Lack of early suppression
Summary
최초 점화된 가연물을 점화시키기 위한 점화원 능력
최초 점화된 가연물의 점화 용이성
최초 점화된 가연물에 노출되는 점화원 인자 : 설계/시공/행정
4. Fire Growth / Flame Spread
Introductory concepts :
화재예방실패 다음 단계는 성장속도 제한
Interior finishing (조기화재성장), floor
(Flashover), Furnishing and decorations (점화 용이/조기 화재성장)
4. Fire Growth / Flame Spread
Material flammability properties / regulation
Ignition properties : Effective Thermal properties(thin, thick), Ignition temperature, Heat release rate properties(연소열, 증발열)
Performance expectations for flammability
Case study : North Central High School
적재된 체육관 매트에서 발화 급속 성장 구조적 손상
Flammability Characteristics of gym mat and Bleachers(관중석)
NFPA 101 : HRR < 100 kW matt 평균 HRR 50 MW
5. Fire Detection and Alarm
Introductory concepts :
Performance expectations for fire detection systems
Performance expectations for fire Alarm and communication systems
Case study : Signature Foods plant (1998년 1월 2일) :
냉동창고, 열감지기(57℃) dry-pipe/preaction SP,
야간 고온수 청소작업으로 회로 차단(고질적인 문제)
설계,시공, ITM, 오동작 등 다양한 형태로 감지 및 경보계통 손상
화재경보 기록은 fire reconstruction에 매우 유용한 자료(R type)
6. Fire Suppression
Performance expectations for fire suppression systems
진압/제어 + 감지/경보
Factors associated to system failures
Case study :
River Cities Business Park (01.2.20)
SP system 손상 : 적재물 배열, 20만 gal 물탱크 전복, 기타 원인?
Commercial Cooking Fire
설계/시공/유지관리 미흡, 소화약제 탱크 미동작(안전플러그)
Refuse Recycling Facility
Over 200 sprinklers opened???
7. Smoke Movement and Management
Introductory concepts
Stack effect, Wind effects, Fire-induced buoyancy and expansion, Mechanical ventilation
Performance expectations for smoke management systems
Case study : Cook County Administration Building(03.10.17)
6명 사망, 21명 부상,
Open door to store room(화재지역) / Locked doors in stairways / Smoke in occupied stair
FDS, CONTAMW Simulations,
NIST 사건조사 참여 : NIST BFRL website “SP-1021” 참조
But for deaths of 6 civilian in stairway, CCAB fire may have been considered a fire protection success despite lack of SP protection
8. Fire Confinement / Structural Integrity
Introductory concepts : Building Type I ~ V
3-hr ratings means no failure 3 hours of real fire exposure
Performance expectations for fire barrier
Performance expectations for structural elements
Test standards : assemblies, doors, windows fire stops……
Case study : First Interstate Bank(88) / One Meridian Plaza(91) / WTC(01)
공통점 : office furnishings, open floor plans, fire spread to multiple floors
차이점 : FIB(재사용), OMP(재사용불가), WTC(붕괴)
Fire resistance of steel-framed structure : Temperature, long-span floor(열팽창 크기), 중력방향으로 견디는 연결부
Pressure Reducing valve 문제점