86 Fuses Breakers and Overcurrent Protection

It is a common, but mistaken, notion that fuses or circuit breakers will wholly protect a building against fire caused by electrical shorting. Fuses and common circuit breakers do not specifically protect against fires or shorting. They protect against overcurrent. They are not specifically short circuit detecting devices. In other words, a fuse or circuit breaker simply opens an electrical circuit when that circuit uses more amperage than the current-carrying capacity or trip point of the fuse...

142 Engine Limitations

Each motor vehicle has an engine with a set maximum amount of power it can deliver. Usually this is its horsepower rating. In the English units system, a horsepower is defined as 550 ft-lbf sec. In the metric or International System of Units, power is usually measured in kilowatts, where 1 kw 1.341 hp. Power is defined as the amount of energy delivered per unit time. where P power, E energy, and t time. In an engine, the amount of power that can be delivered is normally a function of the...

213 Hail Frequency

Since hail fall occurs nearly exclusively in association with thunderstorm activity, it follows then that most hail damage to structures and property occurs in the months with the greatest numberof thunderstorms. As noted in , the month with the greatest numberof thunderstormsinthe metropolitan Kansas City area is June. In fact, thesumof thunderstormsthat occur in May, June, and July typically comprises nearly half of the total annual thunderstorms that occur in the region around Kansas City....

201 General

Fires in automobiles, trucks, and vans fall into one of the following six categories of causes, which are listed roughly in order of importance or frequency. 1. Fuel-related fires. The fire is caused by fuel leakage onto hot components, usually in the engine compartment, or along the exhaust system. 2. Electrical-related fires. This includes short circuits, overheated wiring, and electrical malfunction of components such as fans, blowers, heaters, etc. 4. Garage fires, or similar. This is where...

1415 Estimating Transmission Efficiency

A previous section briefly discussed the efficiency factors associated with getting power from the engine to the wheels, and some representative values for various gears in an automatic transmission were given. As was shown, the mechanical losses at slow speeds could be very high, while at high speeds the losses were much reduced. Obtaining exact test information concerning mechanical efficiency of the drive train is often difficult, and doing the tests can be expensive. However, the values can...

194Brittleness in Tungsten

At ambient temperatures, tungsten is very brittle. It exhibits no practical ductility. The yield point and the rupture point are practically the same. The material does not significantly stretch prior to breaking. This characteristic can be put to good use in determining if the lights were off, or at least relatively cold, at the time of the accident. In accidents where the impact deceleration is high, the filaments may break apart. If they break apart with no discernible stretching of the...

18 A Priori Biases

One of the thornier problems in the reconstruction of a failure or catastrophic event is the insidious application of a priori methodology. This occurs when legal counsel hires a forensic engineer to find only information beneficial to his client's position. The counselor will not specifically state what findings are to be made, but may suggest that since the other side will be giving information detrimental to his client, there is no pressing need to repeat that work. While the argument may...

1419 Bootleggers Turn

A bootlegger's turn is when a car is turned around 180 degrees, generally on a two-lane road, while still being driven forward. Generally, to get a car turned around, it is necessary to stop the car, back up, cut the wheels sharply, and then proceed forward. A bootlegger's turn simply spins the car around to face the opposite direction while it is still moving. As the name implies, a bootlegger's turn is so named because it was a maneuver used by moonshine runners to escape pursing revenuers....

179 Motorcycle Turns

The height of the center of gravity of a motorcycle and rider is often about 24 inches off the ground. When a motorcycle makes a turn, the lean of the rider and motorcycle must equalize the centripetal force in the following way (mv2 R)a(cos 6) Wa(sin 6) (xxix) where 6 angle of lean (as measured from the vertical), W weight of the motorcycle and rider, and a height of the center of gravity when fully upright. Equation (xxix) reduces to the following While professional riders may lean as much as...

66 Guarding

The basic premise of guarding is to prevent exposure to hazardous things in the workplace. The regulations and requirements for machinery guarding are primarily contained in OSHA regulations 1910.211 through 1910.222, and 1910.263(c), revised as of July 1, 1990. Additionally, OSHA has published a booklet, Concepts and Techniques of Machine Safeguarding (OSHA 3067, 1980), which more simply explains and illustrates the various ways of guarding machinery. Often related to guarding matters, OSHA...

712 Fire Spread Indicators Sequential Analysis

The point of origin of a fire can also be found by simply following in reverse order the trail of fire damage from where it ends to where it began. Where several such trails converge, that is the point of origin of the fire. In essence, the method involves determining what burned last, what burned next to last, etc. until the first thing that burned is found. In the same way that a hunting guide interprets signs and markers to follow a trail of game, a fire investigator looks for signs and...

132 Basic Equations

Unless the vehicle meets another object on the way down to change its trajectory, its motion during a simple fall consists of two independent motions in a plane one in the vertical or y direction, and the other in the horizontal or x direction. When an object falls, some of its potential energy due to its elevation in a constant gravitational field converts to kinetic energy. The change in potential energy, that is, the change in elevation from the start of the fall to the point where the fall...

Further Information and References

Automobile Side Impact Collisions - Series II by Severy, Mathewson and Siegel, University of California at Los Angeles, SAE SP-232. For more detailed information please see Further Information and References in the back of the book. Mechanical Design and Systems Handbook, Harold Rothbart, Ed., Chapter 16, McGraw-Hill, New York, 1964. For more detailed information please see Further Information and References in the back of the book. Motor Vehicle Accident Reconstruction and Cause Analysis, by...

Visual Perception and Motorcycle Accidents

Lift up your eyes, and behold them that come from the north where is the flock that was given thee, thy beautiful flock He came out of nowhere I checked before I made the turn and everything was clear. Routine statement made after a motorcycle car accident. The following chapter about motorcycle accidents is somewhat different than the other chapters. In part, it demonstrates that some accidents have a built-in tendency to occur once a certain threshold is crossed even when everyone involved is...

19 The Engineer as Expert Witness

To the lay public and even to many engineers, engineering is often considered an objective science. This is perhaps fostered by the quantitative problemsolving methods used by engineers in design work. People hire engineers to tell them exact answers to their questions. For example, how many cubic meters of earth must be dug out, how much steel is required, or what size bearing is needed The undergraduate training of engineers also emphasizes exact problemsolving techniques. Students spend many...

222 Brick Grades

Table 22.1 compares the physical properties of the three grades of facing brick as required by ASTM C-62. Grade NW is the most inferior grade of facing brick with respect to compressive strength and moisture absorption. It is also generally the cheapest to purchase. This type of brick is intended for use as backup masonry or for interior masonry. When used in exposed locations, grade NW is supposed to be used only where there is no frost and there is less than 20 inches of rain per year, or...

174 Side vs Longitudinal Friction

The total amount of frictional resistance of a tire has been previously given as where Ff the friction force resisting motion, f coefficient of friction, and W the load applied on the tire. The above is generally true when only one resistive force is at work, like a longitudinal or transverse resistive force. However, when both side (transverse) and longitudinal resistive forces are at work, the total frictional force is the vector sum of the two component frictional forces. For example, let...

Simple Skids

In 1895, the gas engine automobile was invented by Daimler, Mayback, and Benz. One century later, there is nearly one car, bus, truck or motocycle for every human in the U.S., and there are about 43,000 deaths per year resulting from their use. The author When a vehicle moves, it possesses a quantity of kinetic energy in proportion to the magnitude of its velocity and mass. In order for the vehicle to come to a stop, its kinetic energy must be dissipated. Skidding is one common way to dissipate...

89Grandfathering of GFCIs

In residences where the houses were built prior to the GFCI requirement of the NEC, usually it is not required that GFCIs be installed, although it is recommended. The original electrical installation is generally allowed to stay in place if it meets three conditions 1. It continues to meet the standards current at the time it was installed. 2. There have been no undue changes made to the original installation. 3. Its continued operation creates no undue risk. If significant modifications are...

11Arson and Incendiary Fires

11.3 Basic Problems of Committing an Arson for Profit 11.5 Typical Characteristics of an Arson or Incendiary Fire 11.6 Daisy Chains and Other Arson Precursors 11.7 Arson Reporting Immunity Laws 11.8 Liquid Accelerant Pour Patterns 11.10 Detecting Accelerants after a Fire Further Information and References

1416 Estimating Engine Thermal Efficiency

As a point of interest, an estimate of the thermal efficiency of the vehicle's engine can be made by comparing the energy input, vis- -vis the engine fuel consumption rate, to the power output, as shown in Equation (iii). A pound of gasoline has about 20,750 BTU (higher heating value) and a pound of diesel fuel has about 19,300 BTU. On a per gallon basis, this is 128,000 BTU and 144,000 BTU, respectively. One horsepower is equivalent to 2545 BTU hr. Since highway fuel consumption is usually...

51 Typical Commercial Buildings 18771917

In the period from post-Civil War Reconstruction to about World War I, many of the small and medium towns that now dot the Midwest were settled and built. In general, the sequence of town building in each case was similar. Homesteads were built first, which congregated around crossroads, river fords or ports, depots, mines, sawmills, or other natural points of commercial activity. This was followed by the construction of temporary tent and woodframe commercial buildings. When business activity...

Randall K Noon

Boca Raton London New York Washington, D.C. Library of Congress Cataloging-in-Publication Data Forensic engineering investigation Randall Noon. p. cm. Includes bibliographical references and index. ISBN 0-8493-0911-5 (alk. paper) 1. Forensic engineering. I. Title. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to...

Evaluating Blasting Damage

4.1 Pre-Blast and Post-Blast Surveys 4.3 Types of Damages Caused by Blasting 4.9 Blast Monitoring with Seismographs 4.10 Blasting Study by U.S. Bureau of Mines, Bulletin 442 4.11 Blasting Study by U.S. Bureau of Mines, Bulletin 656 4.12 Safe Blasting Formula from Bulletin 656 4.13 OSM Modifications of the Safe Blasting Formula in Bulletin 656 4.14 Human Perception of Blasting Noise and Vibrations 4.15 Damages Typical of Blasting 4.16 Types of Damage Often Mistakenly Attributed to Blasting

182 Background Information

According to the 1990 Statistical Abstract of the United States, in 1987, there were about 181 million registered vehicles in the U.S. This includes cars, trucks, and buses. Of this total, 139 million were automobiles. Additionally, there were 5.1 million registered motorcycles. In terms of the total number of registered vehicles, motorcycles constituted about 2.7 , cars constituted 75 , and trucks constituted 22.6 . On the average in 1987, a registered motorcycle was driven only 17.6 as far in...

87 Example Situation Involving Overcurrent Protection

In an older house, the branch wiring to a kitchen wall outlet was rated for 15 amperes. The fuse that protected that circuit was the older, screw-in type household fuse. To dispense with the aggravation of frequent fuse replacement, the homeowner had a 30 ampere fuse inserted in the socket, which was supposed to have only a 15 ampere fuse.* One day the homeowner left an automatic coffeemaker unattended. Initially, the coffeepot was full. However, after a time...

110 Reporting the Results of a Forensic Engineering Investigation

There are several formats used to report the results of a forensic engineering investigation. The easiest is a simple narrative, where the engineer simply describes all his investigative endeavors in chronological order. He starts from when he received the telephone call from the client, and continues until the last item in the investigation is complete. The report can be composed daily or piecewise when something important occurs as the investigation progresses, like a diary or journal....

92 High Pressure Gas Expansion Explosions

The third category of explosion mentioned in the previous section is sometimes classified as a polytropic expansion. This type of explosion does not involve the release of chemical energy via a chemical reaction. It simply involves the rapid expansion of pressurized gases to ambient conditions. In essence, it is the conversion of enthalpy energy to irreversible P-V work, with the final state of the gas at equilibrium with ambient conditions. Polytropic expansions involve a change of state that...

37 Failure Due to Lightning

When lightning has actually damaged a well pump, it is often verified by noting the following items verifiable reports of damaging electrical surges at both ends of the electrical line that services the well pump (note surges flow both ways along a line). evidence of high voltage surges in the line, e.g., flashovers at terminals and relay gaps (the jump distance can be used to estimate the peak voltage of the surge). high voltage damage to the internal lightning arrestor. high voltage damage to...

81 General

A significant proportion of all fires occurring in structures are caused by electrical shorting. The building's wiring system, lighting fixtures, appliances, installed machinery, and extension cords are some of the more common items in which shorting occurs. The shorting components themselves usually do not directly catch fire. Most electrical components contain insulated metal conductors. Except in unusual circumstances, the metal conductors themselves are not flammable. The insulation around...

178 Measuring Roadway Curvature

Referring to Figure 17.2, it can be seenthat Combining Equations (xxv) and (xxvi) gives the following From a practical standpoint, it is convenient to use a standard length to measure L, the chord length, and then measure x, the depth of the chord. If, for example, a 50-ft tape is used as the standard, Equation (xxvii) becomes R (2500) (8x) + x 2 312.5 x + x 2 (xxviii)

1414 Maximum Climb

Since a typical mid-sized passenger car has a take-off acceleration of about 0.33g, this places a limit on the maximum grade that the car can climb. When a box is laid on a frictionless inclined plane, the acceleration down the grade is as follows where a the angle that the inclined plane makes with the horizontal. In order for a vehicle to be able to go up an incline, the vehicle must be able to accelerate more than the downward acceleration along the incline, and must be able to grip the...

73 Burning Velocities and Flame Velocities

There is an important exception to the previous discussion of V patterns, and that exception involves the use of liquid accelerants. When a liquid accelerant, especially one whose flash point is below room temperature, is splashed on a wall and ignited, the fire travels quickly throughout the contiguous area wetted by the accelerant downward, upward, and lateral. With respect to burn within the wetted area, the directional fire velocities are nearly the same, for all practical purposes. This is...

1413 Nhtsa Study

Because of the public interest in SAIs, the National Highway Traffic Safety Administration conducted a study of ten vehicle types with above-average SAI complaints. The results of the study, entitled An Examination of Sudden Acceleration (U.S. Dept. of Transportation, D0T-HS-807-367), were made public in 1989. The following is a summary of the study's findings 1. A substantial number of SAIs involved accelerator linkages that hung up due to a mechanical problem. However, the problem caused the...

35Lightning Access to a Well Pump

By being submerged in water many feet below the surface, well pumps are in intimate electrical contact with the mother of all electrical grounds the earth. When lightning strikes the surface of the earth near a well pump, there is no incentive for the lightning to flow from its grounding point at the surface to the well pump situated many feet below the surface. Once a lightning strike has grounded out and dissipated at the surface, it does not regroup itself and flow through grounded earth...

105 The Epicenter

When a gas leak occurs, the gas will initially form an irregularly shaped cloud of fuel that diffuses away from the leak. If the gas is methane and the air is more or less calm, the gas will slowly rise at first to the ceiling and accumulate in high areas. If the gas is propane, it will sink to the floor and accumulate in low areas. As the fuel cloud diffuses and moves away from the point of leakage, its boundary may come into contact with an energy source capable of igniting the fuel, provided...

124 Tire Friction

The figures provided in Table 12.1 are reasonably accurate for relatively short skids. However, it is known that the coefficient of friction is not wholly constant during a skid. As the skid progresses, the coefficient of friction will decrease as a function of the forward velocity. This decrease in the coefficient of friction can be approximated by the following linear equation where f coefficient of friction, f initial coefficient of friction term (static friction), c constant determined by...

167 Post Buckling Behavior of Columns

The analysis of buckled elastic columns, which is sometimes known as the problem of the elastica, was first done by Euler more than 200 years ago. While the derivations are somewhat beyond the scope of this text, the results are important. In a simple column where each end is free to rotate and a load is applied at one end axially, the column will buckle elastically at the Euler buckling load, which is usually given as where Fcr force required for elastic buckling, i.e., critical load, E...

113 Basic Problems of Committing an Arson for Profit

In order to be a successful arsonist, the arsonist must burn enough of his house, property, or inventory for it to be considered a total loss. In that way, he will collect the policy limits for the fire, instead of having the insurance company rebuild or replace the property. When the latter occurs, he usually does not make enough money. After all, it was the policy limit that was the temptation in the first place, and not the allure of a redecorated bathroom. Because of this, when a fire is...

203 Fuel Related Fires

By far the largest category of automotive fires usually involves fuel leaking onto a hot portion of the engine. The engine block, and especially the exhaust manifold and exhaust, is a ready source of ignition energy after the engine has run for a time. Fuel can leak onto the engine from many locations. In modern engines, there is not only the main fuel line from the fuel tank to the engine, but there are also fuel return lines associated with the vapor control system, the emissions system, and...

2110 Foam Roofing Systems

Sprayed polyethylene foam (SPF) roofing systems, commonly called foam roofing systems, are relatively uncommon now in the U.S. except in the South. Historically, they have not fared well with respect to hail. Part of this is due to poor installation techniques, poor quality control of the properties of the foam when it has been mixed in the field, or simply to unexpected problems encountered in the inherent properties of the materials used in either the foam or the coating. Because of these bad...

1612 Some Additional Comments

As noted before, the stiffness coefficient is basically the force at which buckling occurs. For example, a car with a frontal stiffness coefficient of 6000 lb-ft in, has a Euler buckling load of 500 lb. However, it should be recognized that this is the force that must be applied evenly across the front of the car. Thus, when the impact across the front is not even, an average depth is determined by making depth measurements at regular intervals and averaging them, as shown in Figure 16.5. With...

202 Vehicle Arson and Incendiary Fires

There are nearly as many fires, arsons, and incendiary fires in personal vehicles as there are involving homes. The most common motives for incendiary fires in personal vehicles include the following. 1. Cash flow problems. The owner cannot afford the payments and is in danger of default. 2. The value of the car is upside down. This is when the remaining payments on the car total more than the present value of the car. For example, a car that has been poorly cared for and abused may be shot...

23 Variation of Wind Speed with Height

Wind blows slower near the surface of the ground than it does higher up. This is because the wind is slowed down by friction with the ground and other features attached to the ground, like trees, bushes, dunes, tall grass, and buildings. Because of this, wind speeds measured at, say 50 feet from the ground, are usually higher than wind speeds measured at only 20 feet from the ground. In fact, the wind speed measured at 50 feet will usually be 14 higher than the speed at 20 feet, assuming clear,...

76 Radiation

The third mode of energy transfer, radiation, is where heat is transferred from one point to another by electromagnetic waves, typically in the wavelength range of 0.1 to 100 microns. No intermediary material is needed. In fact, when there are intermediary materials, such as gases or suspended dust, the amount of heat transferred by radiation is decreased due to absorption of heat by the gas or dust. In this method of heat transfer, the amount of energy radiated away into space is proportional...

219 Damage to the Sheet Metal of Automobiles and Buildings

The sheet metal covering of a car or a metal building is basically a stiff, planar membrane in the localized area where a hailstone impacts. When a hailstone impacts the sheet metal, the sheet metal is slightly depressed by the impact. Directly under the impact area, the material deflects and bends. If the impact is light, the sheet metal will spring back in a fully elastic fashion and no permanent deformation will occur. If the impact is sufficiently severe, there will be plastic deformation...

Angle of Rotation During Rollover

Figure 16.2 Plot of center of gravity vs. rollover angle. energy to accomplish this. Eight inches of energy will be lost in crush, damping, and friction. The other nine inches of energy goes to increasing the overall potential energy of the vehicle. 2. If there is just enough work performed to roll the car onto its roof, another 12 inches of energy will be needed to go from the side position to the roof position. This is a total of 29 inches of energy expended so far. 3. To continue rolling...

43 Types of Damages Caused by Blasting

There are four types of physical damage that can be caused by blasting operations at construction sites. 4. Ground displacement due to blasting vibrations. 4.4 Flyrock Damage Flyrock debris damage is relatively easy to spot and assess. It occurs when the blaster does not adequately bury or cover the blast charges to prevent blowout from the hole. Rocks and soil materials may become airborne missiles and be hurled away from the point of detonation. Flyrock debris damage occurs relatively close...

21 Code Requirements for Wind Resistance

Most nationally recognized U.S. building codes, such as the Unified Building Code (UBC) and the Building Officials and Code Administrators (BOCA) code require that buildings be able to withstand certain minimum wind speeds without damage occurring to the roof or structure. In the Midwest, around Kansas City for example, the minimum wind speed threshold required by most codes is 80 mph. For comparison, hurricane level winds are considered to begin at 75 mph. According to the National Oceanic and...

193 Oxidation of Tungsten

Tungsten will oxidize in air at 752 F to form tungsten trioxide. As the temperature increases, the rate of oxidation rapidly increases. Also, extremely fine tungsten is highly flammable and can ignite spontaneously in air. Since the oxidation temperature of tungsten is well below the temperature at which incandescence occurs, to keep the tungsten from simply burning up, it must be encased in a bulb containing a nonreacting atmosphere, such as nitrogen or carbon dioxide. While tungsten's...

41 Pre Blast and Post Blast Surveys

The simplest method to assess and document blasting damages in a structure is the before and after approach. The structure in question is thoroughly inspected immediately prior to blasting work being done. Then, the same structure is reinspected in the same way immediately after blasting work is completed. The two surveys are then compared to determine if there are cracks and fissures present after blasting that were not present before blasting. It is then presumed that any new cracks or...

217 Cosmetic Hail Damage Burnish Marks

The most common type of cosmetic damage that is mistaken for structural damage are burnish marks. A burnish mark is where the impact of a hailstone rubs off a small portion of the weathered exterior film of the material without damaging the material itself. The rubbing by the hailstone leaves a small, fresh surface surrounded by a larger, weathered surface area. The overall appearance of the surface is often described as freckled, spotted, or pockmarked. The use of the last descriptor is...

82 Thermodynamics of a Simple Resistive Circuit

Consider a simple circuit that only has resistance and an alternating voltage source, such as shown in Figure 8.1. Like most household circuits, the voltage varies sinusoidally. Figure 8.1 Simple resistive circuit. In this circuit, the instantaneous current flowing through the resistive load follows Ohm's law. Emax(sin rot) I(Rl) Ohm's law (i) where I current, RL resistive load in circuit, Emax maximum voltage amplitude, t time, and ro frequency of alternating current given in radians per...

1110 Detecting Accelerants after a Fire

Contrary to popular myth, accelerants do not completely burn up with the fire. Often, small amounts of the accelerant will be absorbed by the material to which it was applied. This includes wood, concrete, tiles, textiles, and other common construction materials that have some porosity. Sometimes, sufficient amounts will be absorbed in the material, which then outgases after the fire. This sometimes creates a recognizable odor that is noticeable directly after the fire has been extinguished....

212 Hail Size

The average hail fall duration in the Midwest is about 5 minutes and covers an area approximately 20 square miles, which is why it is always prudent to check for collateral damage to nearby similar buildings and structures when a hail damage claim requires verification. Hail falls, however, can last as long as 15 minutes. The relative size range of hail within a particular hail fall area is usually no more than 1 to 3, that is, the largest hailstone will usually be no more than about three...

42 Effective Surveys

Companies that do pre-blast and post-blast survey work are often hired by the blasting contractor, the local unit of government, a home owners' association, or an insurance company, usually the one representing the blasting contractor. The reports and documents generated by blast survey companies are usually open to all parties involved, not just the client. This is usually stipulated in the local ordinance or the contractual agreement. The field people that do pre-blast and post-blast surveys...

77 Initial Reconnoiter of the Fire Scene

In observing a fire scene for the first time, it is often best not to rush directly into the fire-damaged areas in search of the origin. Most fire investigators will first reconnoiter the fire scene to observe which areas did not burn. This is important for two reasons first and obvious is the fact that the areas that did not burn do not contain the point of origin. Often knowing what was not burned by the fire allows the elimination of many theoretical point-of-origin possibilities. The second...

166 Modeling Vehicular Crush

Several types of conceptual models have been used to represent a vehicle that has sustained crush damage. Some computer programs that analyze vehicular collisions have modeled a vehicle like an elastic ball. In such a model, the collision is considered elastic, and the spring stiffness is the same from any direction of impact. This billiard ball model works reasonably well when the collision impulse is in the elastic response range of the vehicle, but quickly becomes inadequate when there is a...

1513 Estimation of a Collision Coefficient of Restitution from Fixed Barrier Data

When a vehicle impacts a fixed barrier, it is presumed that the fixed barrier does not crush or otherwise absorb any significant amount of kinetic energy from the vehicle. The fixed barrier pushes back against the vehicle during impact with a force equal to that being applied by the vehicle. In essence, since no work can be done on the fixed barrier, the vehicle does work on itself. Earlier, Equation (xxv) was derived to show the relationship between energy dissipated by the collision and the...

215 Size Threshold for Hail Damage to Roofs

One of the premier studies in hail damage, Hail Resistance of Roofing Structures Building Science Series 23, was done by the U.S. Department of Plate 21.4 Hail dents in copper decoration on roof that has been in place for more than 20 years. Plate 21.4 Hail dents in copper decoration on roof that has been in place for more than 20 years. Commerce in 1969. Authored by Sidney Greenfeld, a research associate of the Asphalt Roofing Manufacturers' Association, the study was commissioned by the...

24 Estimating Wind Speed from Localized Damages

One of the problems in dealing with wind damages is the estimation of wind speed when the subject building is located far from a weather reporting station, or is in an area that obviously experienced wind conditions different from that of the nearest weather station. In such cases, wind speed can actually be estimated from nearby collateral damage by the application of the Beaufort wind scale. The Beaufort wind scale is a recognized system introduced in 1806 by Admiral Beaufort to estimate wind...

216 Assessing Hail Damage

In general, damage to asphalt shingles, built up roofs (i.e., tar and gravel), asbestos cement shingles, cedar shingles, standing-seam terne metal roofs, slate, and red clay tiles that have been caused by severe hailstone impacts consist of impact craters and cracks and fissures originating at those craters. Impact craters are where the impacts by hailstones have penetrated sufficiently into the material to breach its functional integrity and produce significant, permanent depressions or dents....

711 Weighted Centroid Method

The weighted centroid method is similar to the basic centroid method except that this method assumes that the point subject to the longest duration of fire, and consequently the most severely damaged, is the point of origin. To this end, areas more severely damaged by fire are given more weight in determining the centroid than areas with less severe damage. As before, the method presumes a generally homogeneous structure in terms of material flammability and construction. For example, the...

413 OSM Modifications of the Safe Blasting Formula in Bulletin 656

Since the publication of Bulletin 656, the original safe blasting formula and the safe blasting vibrational levels have both been modified by the Office of Surface Mining (OSM). The modifications are contained in the publication, Structure Response and Damage Produced by Ground Vibration from Surface Mine Blasting, by Siskind, Stagg, Kopp, and Dowding, and published by the United States Department of Interior Bureau of Mines in 1980. The modifications were done to further reduce complaints due...

218 The Haig Report

One of the most quoted, and misquoted sources of information about hail damage to wood roofs is commonly called the Haig report. The formal title is, Haig Engineering Red Cedar Shingle Study, by Haig Engineering Company (2400 West Loop South, Houston, Texas 77027). The report is also summarized with explanatory commentary in the monograph, Hail Damage to Red Cedar Shingles A Guide for Adjusters and Roofers, published in 1975 by the American Insurance Association. Basically, Haig Engineering...

118 Liquid Accelerant Pour Patterns

Gasoline, lighter fluid, barbecue fluid, kerosene, and other light distillate hydrocarbon compounds are usually the accelerants of choice, especially among the do-it-yourself incendiary crowd. They are easy to obtain, easy to conceal, cheap to buy, a person doesn't have to be 21 years old to have them, and a little bit goes a long way. The more common method for applying accelerant is what is shown on television crime shows and in the movies just pour it over what you wish to burn, light it,...

72 Burning Velocities and V Patterns

From casual observation, it is apparent that fire propagates at different rates depending upon the material and its orientation. With respect to orientation, for example, it is common knowledge to anyone who has used matches that a fire burns up a match faster than it burns down a match. It is also common knowledge that when a match is held horizontally, the burn rate is somewhere between. Consider the following simple experiment. A common wooden kitchen match is about 50 mm long, excluding the...

214 Hail Damage Fundamentals

In terms of monetary losses, hail primarily damages crops, building roofs and siding, and cars. The severity of hail damage depends on two main factors Plate 21.2 Hail impacts on A C heat exchanger fins. Fins can be combed out with no significant loss of efficiency. Plate 21.2 Hail impacts on A C heat exchanger fins. Fins can be combed out with no significant loss of efficiency. 1. How much kinetic energy the hailstone possesses at impact, which is a function of its mass and impact velocity. 2....

115 Typical Characteristics of an Arson or Incendiary Fire

An arsonist has several problems to overcome in order to accomplish his goal. The ways in which an arsonist solves these problems are the same ways in which identification of an arson or incendiary fire is provided. The following is a short list of the more common characteristics of an incendiary fire. 1. Multiple origins of fire, especially several points of fire origin that are unconnected to each other. There are no fire pathways between the various points of origin to account for the...

22 Some Basics about Wind

Air has two types of energy, potential and kinetic. The potential energy associated with air comes from its pressure, which at sea level is about 14.7 pounds per square inch or 1013.3 millibars. At sea level, the air is squashed down by all the weight of the air that lies above it, sort of like the guy at the bottom of a football pile-up. Like a compressed spring, compressed air stores energy that can be released later. The kinetic energy associated with air comes from its motion. When air is...