Forensic engineering is the application of engineering principles, knowledge,skills, and methodologies to answer questions of fact that may have legalramifications.. The solution of “rea
Trang 2FORENSIC ENGINEERING INVESTIGATION
Trang 3ENGINEERING INVESTIGATION
Randall K Noon
Boca Raton London New York Washington, D.C.
CRC Press
Trang 4This book contains information obtained from authentic and highly regarded sources Reprinted material
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Library of Congress Cataloging-in-Publication Data
Noon, Randall
Forensic engineering investigation / Randall Noon.
p cm.
Includes bibliographical references and index.
ISBN 0-8493-0911-5 (alk paper)
1 Forensic engineering I Title.
TA219 N64 2000
Trang 5Forensic engineering is the application of engineering principles, knowledge,skills, and methodologies to answer questions of fact that may have legalramifications Forensic engineers typically are called upon to analyze caraccidents, building collapses, fires, explosions, industrial accidents, and var-ious calamities involving injuries or significant property losses Fundamen-tally, the job of a forensic engineer is to answer the question, what causedthis to happen?
A forensic engineer is not a specialist in any one science or engineeringdiscipline The solution of “real-world” forensic engineering problems oftenrequires the simultaneous or sequential application of several scientific dis-ciplines Information gleaned from the application of one discipline mayprovide the basis for another to be applied, which in turn may provide thebasis for still another to be applied The logical relationships developedamong these various lines of investigation usually form the basis for thesolution of what caused the event to occur Because of this, skilled forensicengineers are usually excellent engineering generalists
A forensic engineering assignment is perhaps akin to solving a picturepuzzle Initially, there are dozens, or perhaps even hundreds, of seeminglydisjointed pieces piled in a heap When examined individually, each piecemay not provide much information Methodically, the various pieces aresorted and patiently fitted together in a logical context Slowly, an overallpicture emerges When a significant portion of the puzzle has been solved,
it then becomes easier to see where the remaining pieces fit
As the title indicates, the following text is about the analyses and methodsused in the practice of forensic engineering It is intended for practicingforensic engineers, loss prevention professionals, and interested students whoare familiar with basic undergraduate science, mathematics, and engineering.The emphasis is how to apply subject matter with which the reader alreadyhas some familiarity As noted by Samuel Johnson, “We need more to bereminded than instructed!”
As would be expected in a compendium, the intention is to provide asuccinct, instructional text rather than a strictly academic one For this rea-son, there are only a handful of footnotes While a number of useful references
Trang 6are provided at the end of each chapter, they are not intended to represent
an exhaustive, scholarly bibliography They are, however, a good startingpoint for the interested reader Usually, I have listed references commonlyused in “the business” that are available in most libraries or through inter-library loans In a few cases I have listed some hard-to-get items that arenoteworthy because they contain some informational gems relevant to thebusiness or represent fundamental references for the subject
The subjects selected for inclusion in this text were chosen on the basis
of frequency They are some of the more common types of failures, strophic events, and losses a general practicing forensic engineer may becalled upon to assess However, they are not necessarily, the most commontypes of failures or property losses that occur Forensic engineers are notusually called upon to figure out the “easy ones.” If it was an easy problem
cata-to figure out, the services of a forensic engineer would not be needed
In general, the topics include fires, explosions, vehicular accidents,industrial accidents, wind and hail damage to structures, lightning damage,and construction blasting effects on structures While the analysis in eachchapter is directed toward the usual questions posed in such cases, theprinciples and methodologies employed usually have broader applicationsthan the topic at hand
It is the intention that each chapter can be read individually as the needfor that type of information arises Because of that, some topics or principlesmay be repeated in slightly different versions here and there in the text, andthe same references are sometimes repeated in several chapters Of course,some of the subjects in the various chapters naturally go together or leadinto one another In that regard, I have tried to arrange related chapters sothat they may be read as a group, if so desired
I have many people to thank for directly or indirectly helping me withthis project I am in debted to my wife Leslie, who encouraged me to under-take the writing of this book despite my initial reluctance I also thank thepeople at CRC Press, both present and past, who have been especially sup-portive in developing the professional literature associated with forensic sci-ence and engineering And of course, here’s to the engineers, techs,investigators, and support staff who have worked with me over the years andhave been so helpful I’ll see you all on St Paddy’s at the usual place
R N
Trang 7About the Author
Mr Noon has written three previous texts in the area of forensic engineering:
Introduction to Forensic Engineering, Engineering Analysis of Fires and sions, and Engineering Analysis of Vehicular Accidents All three are available
Explo-through CRC Press, Boca Raton, FL
Trang 8For Nub and Donna, Pete and Dickie, Fanny, Ethel, Althea, and Marcus, Jeanette, Leo Audel, Emery, and Paul,
Bob and Ruby, Violet, Sheila, and Vera Mae, Helen, Ernest, Darwin, Billy, and Thomas E., Leo, Leroy, Everet, and Gerald Marcus,
and Tommy Ray.
Remember me when I am gone away, Gone far away into the silent land; When you can no more hold me by the hand, Nor I half turn to go, yet turning stay Remember me when no more, day by day, You tell me of our future that you planned; Only remember me; you understand
It will be late to counsel then or pray Yet, if you should forget me for a while And afterwards remember, do not grieve; For if the darkness and corruption leave
A vestige of the thought that once I had, Better by far that you should forget and smile Than that you should remember and be sad.
—Christina Rossetti 1830–1894
Trang 91.4 Role in the Legal System
1.5 The Scientific Method
1.6 Applying the Scientific Method to Forensic Engineering1.7 The Scientific Method and the Legal System
1.8 A Priori Biases
1.9 The Engineer as Expert Witness
1.10 Reporting the Results of a Forensic Engineering
InvestigationFurther Information and References
2 Wind Damage to Residential Structures
2.1 Code Requirements for Wind Resistance
2.2 Some Basics about Wind
2.3 Variation of Wind Speed with Height
2.4 Estimating Wind Speed from Localized Damages2.5 Additional Remarks
Further Information and References
3 Lightning Damage to Well Pumps
3.1 Correlation is Not Causation
3.2 Converse of Coincidence Argument
3.3 Underlying Reasons for Presuming Cause and Effect3.4 A Little about Well Pumps
3.5 Lightning Access to a Well Pump
3.6 Well Pump Failures
3.7 Failure Due to Lightning
Further Information and References
Trang 104 Evaluating Blasting Damage
4.1 Pre-Blast and Post-Blast Surveys
4.2 Effective Surveys
4.3 Types of Damages Caused by Blasting
4.4 Flyrock Damage
4.5 Surface Blast Craters
4.6 Air Concussion Damage
4.7 Air Shock Wave Damage
4.8 Ground Vibrations
4.9 Blast Monitoring with Seismographs
4.10 Blasting Study by U.S Bureau of Mines, Bulletin 4424.11 Blasting Study by U.S Bureau of Mines, Bulletin 6564.12 Safe Blasting Formula from Bulletin 656
4.13 OSM Modifications of the Safe Blasting Formula inBulletin 656
4.14 Human Perception of Blasting Noise and Vibrations4.15 Damages Typical of Blasting
4.16 Types of Damage Often Mistakenly Attributed toBlasting
4.17 Continuity
Further Information and References
5 Building Collapse Due to Roof Leakage
5.1 Typical Commercial Buildings 1877–1917
5.2 Lime Mortar
5.3 Roof Leaks
5.4 Deferred Maintenance Business Strategy
5.5 Structural Damage Due to Roof Leaks
5.6 Structural Considerations
5.7 Restoration Efforts
Further Information and References
6 Putting Machines and People Together
Trang 116.8 Manufacturer’s Responsibilities
6.9 New Ergonomic Challenges
Further Information and References
7 Determining the Point of Origin of a Fire
7.1 General
7.2 Burning Velocities and “V” Patterns
7.3 Burning Velocities and Flame Velocities
7.4 Flame Spread Ratings of Materials
7.5 A Little Heat Transfer Theory: Conduction andConvection
7.6 Radiation
7.7 Initial Reconnoiter of the Fire Scene
7.8 Centroid Method
7.9 Ignition Sources
7.10 The Warehouse or Box Method
7.11 Weighted Centroid Method
7.12 Fire Spread Indicators — Sequential Analysis7.13 Combination of Methods
Further Information and References
8.6 Fuses, Breakers, and Overcurrent Protection
8.7 Example Situation Involving Overcurrent Protection8.8 Ground Fault Circuit Interrupters
8.9 “Grandfathering” of GFCIs
8.10 Other Devices
8.11 Lightning Type Surges
8.12 Common Places Where Shorting Occurs
Further Information and References
9 Explosions
9.1 General
9.2 High Pressure Gas Expansion Explosions
Trang 129.4 Some Basic Parameters
9.5 Overpressure Front
Further Information and References
10 Determining the Point of Ignition of an
Explosion
10.1 General
10.2 Diffusion and Fick’s Law
10.3 Flame Fronts and Fire Vectors
10.4 Pressure Vectors
10.5 The Epicenter
10.6 Energy Considerations
Further Information and References
11 Arson and Incendiary Fires
11.7 Arson Reporting Immunity Laws
11.8 Liquid Accelerant Pour Patterns
11.9 Spalling
11.10 Detecting Accelerants after a Fire
Further Information and References
12.6 Calculation of Skid Deceleration
12.7 Speed Reduction by Skidding
12.8 Some Considerations of Data Error
12.9 Curved Skids
12.10 Brake Failures
12.11 Changes in Elevation
12.12 Load Shift
Trang 1312.13 Antilock Brake Systems (ABS)
Further Information and References
13 Simple Vehicular Falls
14.3 Deviations from Theoretical Model
14.4 Example Vehicle Analysis
14.15 Estimating Transmission Efficiency
14.16 Estimating Engine Thermal Efficiency
15.2 Basic Momentum Equations
15.3 Properties of an Elastic Collision
15.4 Coefficient of Restitution
15.5 Properties of a Plastic Collision
15.6 Analysis of Forces during a Fixed Barrier ImpactEnergy Losses and “ε”
Trang 1415.8 Center of Gravity
15.9 Moment of Inertia
15.10 Torque
15.11 Angular Momentum Equations
15.12 Solution of Velocities Using the Coefficient
of Restitution15.13 Estimation of a Collision Coefficient of Restitutionfrom Fixed Barrier Data
15.14 Discussion of Coefficient of Restitution MethodsFurther Information and References
16 Energy Methods
16.1 General
16.2 Some Theoretical Underpinnings
16.3 General Types of Irreversible Work
16.4 Rollovers
16.5 Flips
16.6 Modeling Vehicular Crush
16.7 Post-Buckling Behavior of Columns
16.8 Going from Soda Cans to the Old ‘Can You Drive?’16.9 Evaluation of Actual Crash Data
16.10 Low Velocity Impacts — Accounting for the ElasticComponent
16.11 Representative Stiffness Coefficients
16.12 Some Additional Comments
Further Information and References
17 Curves and Turns
17.1 Transverse Sliding on a Curve
17.2 Turnovers
17.3 Load Shifting
17.4 Side vs Longitudinal Friction
17.5 Cornering and Side Slip
17.6 Turning Resistance
17.7 Turning Radius
17.8 Measuring Roadway Curvature
17.9 Motorcycle Turns
Further Information and References
18 Visual Perception and Motorcycle Accidents
18.1 General
Trang 1518.2 Background Information
18.3 Headlight Perception
18.4 Daylight Perception
18.5 Review of the Factors in Common
18.6 Difficulty Finding a Solution
Further Information and References
19 Interpreting Lamp Filament Damages
20.6 Mechanical and Other Causes
Further Information and References
21 Hail Damage
21.1 General
21.2 Hail Size
21.3 Hail Frequency
21.4 Hail Damage Fundamentals
21.5 Size Threshold for Hail Damage to Roofs21.6 Assessing Hail Damage
21.7 Cosmetic Hail Damage — Burnish Marks21.8 The Haig Report
21.9 Damage to the Sheet Metal of Automobiles andBuildings
21.10 Foam Roofing Systems
Trang 1622 Blaming Brick Freeze-Thaw Deterioration
Further Information and References
23 Management’s Role in Accidents and
Catastrophic Events
23.1 General
23.2 Human Error vs Working Conditions
23.3 Job Abilities vs Job Demands
23.4 Management’s Role in the Causation of Accidentsand Catastrophic Events
23.5 Example to Consider
Further Information and References
Further Information and References
Trang 171.1 Definition of Forensic Engineering
Forensic engineering is the application of engineering principles and odologies to answer questions of fact These questions of fact are usuallyassociated with accidents, crimes, catastrophic events, degradation of prop-erty, and various types of failures
meth-Initially, only the end result is known This might be a burned-out house,damaged machinery, collapsed structure, or wrecked vehicle From this start-ing point, the forensic engineer gathers evidence to “reverse engineer” howthe failure occurred Like a good journalist, a forensic engineer endeavors todetermine who, what, where, when, why, and how When a particular failurehas been explained, it is said that the failure has been “reconstructed.” Because
of this, forensic engineers are also sometimes called reconstruction experts.Forensic engineering is similar to failure analysis and root cause analysiswith respect to the science and engineering methodologies employed Oftenthe terms are used interchangeably However, there are sometimes implieddifferences in emphasis among the three descriptors
“Failure analysis” usually connotes the determination of how a specificpart or component has failed It is usually concerned with material selection,design, product usage, methods of production, and the mechanics of thefailure within the part itself
“Root cause analysis” on the other hand, places more emphasis on themanagerial aspects of failures The term is often associated with the analysis
of system failures rather than the failure of a specific part, and how proceduresand managerial techniques can be improved to prevent the problem fromreoccurring Root cause analysis is often used in association with large sys-
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