The government, in trying to prove that a single Ryder truck filled with explosives could have caused the damage seen in the Murrah building commissioned an experimental study by the Armament Directorate, Wright Laboratory at Eglin Air Force Base in Florida. Intended to be used to bolseter the "lone bomber" case against Timothy McVeigh, the results of the study proved to be an embarressment to the government.
[1][ISMAP]-[2][USEMAP]
[INLINE]
[INLINE]
OKC Bombing: Forensic Evidence
_________________________________________________________________
Multiple Blasts: More Evidence
by William F. Jasper
A new study analyzing explosive tests conducted by the U.S. Air Force
against a reinforced concrete structure may provide an important key
to understanding the April 1995 bombing of the Alfred P. Murrah
Building in Oklahoma City, which took 168 lives. The report, based on
testing data and photographs supplied by the Armament Directorate,
Wright Laboratory at Eglin Air Force Base in Florida, lends powerful
support to the arguments of those experts who have challenged the
official government position that a single, large ammonium
nitrate/fuel oil (ANFO) truck bomb parked outside the Murrah Building
was solely responsible for the massive death and destruction.
Led by Brigadier General Benton K. Partin (USAF, ret.), former
director of the Air Force Armament Technology Laboratory and one of
the world’s premier explosives and ordnance authorities, critics
have argued compellingly that the blast wave from the ANFO truck bomb
was totally inadequate to cause the collapse of the massive,
steel-reinforced concrete columns of the federal building in Oklahoma
City. This fact, together with much other forensic evidence from the
crime scene, they contend, points inescapably to the conclusion that
additional demolition charges had to have been placed on columns
inside the building. Which means that this terror bombing was a much
more sophisticated operation than the federal authorities admit,
requiring more hands, brains, and brawn than any lone bomber could
supply. If that is true, the other bombers are being let off the hook
by the government’s insistence that Timothy McVeigh was the sole
efficient cause and the truck bomb was the instrumental cause of
“the deadliest terrorist attack on American soil.”
The new Eglin blast study convincingly proves the fundamental points
set forth by General Partin: That air blast is an inefficient
mechanism against hardened, reinforced concrete structures, and that
“the pattern of damage [to the Murrah Building] would have been
technically impossible without supplementing demolition charges.”
Entitled Case Study Relating Blast Effects to the Events of April 19,
1995 Alfred P. Murrah Federal Building, Oklahoma City, Oklahoma,
(hereafter referred to as the Eglin Blast Effects Study, or EBES), the
56-page report includes photographs and data from the Eglin blast
tests, as well as extensive technical analysis of those tests,
conducted by construction and demolition expert John Culbertson. The
study relates the Eglin parametric data to the Murrah Building and
presents a serious challenge to the federal prosecutors’ official
bombing scenario. The report also contains letters from engineers and
technical experts who have reviewed the study for The New American.
The blast effects tests conducted by the Wright Laboratory at Eglin
Air Force Base involved a three-story reinforced concrete structure 80
feet in length, 40 feet in width, and a total height of 30 feet. The
Eglin Test Structure (ETS), according to the EBES, “while not as
large as the Alfred P. Murrah Building in Oklahoma City, has many
similarities and therefore provides an excellent source for
data.” The study continues:
The ETS is similar to Murrah in its basic layout with three rows of
columns in the long axis and a series of narrow bays in the short
axis. The ETS was constructed of six-inch-thick concrete panels
similar to the six-inch-thick floor panels of Murrah. In addition,
a series of 14-inch square columns supported the panels in the
corners of each room and at the edge of the floor panels. This
configuration bears a similarity to the Murrah building’s
system of columns, T-beams and floor panels.
While noting the similarities in structural layout of the ETS and
Murrah, the EBES also makes note of the major differences in
construction methods and overall structural integrity between the two
buildings, stating that the ETS “must be considered an inferior
structure in terms of strength and blast resistance,” and that
the ETS “is actually more indicative of some structures to be
found in third world countries and is not representative of concrete
structures to be found in the United States.” The Murrah
Building’s floor panels were reinforced “with approximately
five times the amount of steel” used in the Eglin
structure’s panels. An even greater contrast is found in the
columns and beams, where “the steel fill in the Murrah Building
was much higher than the ETS, in most cases by a factor of 10 or
more.” The study also observes that “while the ETS did not
use stirrups in its columns and beams, the Murrah Federal Building
did, thereby increasing strength to a level far above the ETS.”
Additionally, the ETS lacked a roof panel, which “reduces the
overall rigidity of the structure, and in particular the third story
wall panels, making the third story more susceptible to damage from an
explosive device.” Finally, since concrete develops strength with
time, the relatively fresh concrete of the ETS must be considered
weaker than the mature strength of the Murrah Building’s
concrete.
All of the foregoing is of particular significance since, as the Air
force tests demonstrated, air blast alone was singularly ineffective
in causing major damage to the ETS. And if air blast could not effect
catastrophic failure to the decidedly inferior Eglin structure, it
becomes all the more difficult to believe that it was responsible for
the destruction of the much stronger Murrah Building.
Three different explosives tests were conducted on the Eglin Test
Structure. The first test used 704 pounds of Tritonal, which is
equivalent to 830 pounds of TNT, or roughly 2,200 pounds of a properly
prepared ammonium nitrate/fuel oil (ANFO) mixture. The Tritonal was
contained in a light aluminum case and was placed outside the
structure at ground level 25 feet from the vertical surface of the
40-foot side wall. This test most closely parallels the truck bomb at
the Murrah Building and provides important parametric data for
assessing blast-wave damage at the Oklahoma City site. Besides being
external to the ETS, the aluminum casing provided a container similar
to the light shell of the Ryder truck. Like the truck bomb, the
Tritonal test attempted to effect damage to the concrete structure
with an air-couple blast wave without the help of heavy shrapnel.
By contrast, the second and third tests used steel-cased warheads
detonated inside the ETS. The second test used a standard Mk-82
warhead (equivalent to 180 pounds of TNT) placed within the first
floor corner room approximately four feet from the exterior wall. The
third test involved a 250-pound penetrating warhead (having an
equivalent explosive weight of 35 pounds TNT) which was placed in the
corner of a second floor room approximately two and a half feet from
the adjoining walls. As the photographs from Wright Laboratory
graphically show, these two explosive devices, although much smaller
than the Tritonal device, effected far greater damage to the ETS. This
disproportionate destruction was largely a function of three critical
factors: distance, mechanical coupling of the blast wave, mechanical
coupling via shrapnel, and contained pressure (due to being confined
within the structure).
As General Partin has taken great pains to emphasize, the inefficiency
of a blast wave through air is dramatic — particularly outdoors,
where the blast energy is dissipated in all directions — with its
pressure and destructive force falling off more rapidly than an
inverse function of the distance cubed (distance expressed in radius
units). This means that the blast wave from an explosive device which
yields a maximum blast pressure of one-and-a-half million pounds per
square inch at the center of the device will have dropped off to under
200 pounds per square inch by the time it has traveled 20 radii. This
makes air blast alone very ineffective against hardened concrete
structures, such as heavy, steel-reinforced columns.
The photograph from Wright Laboratory of the first test involving the
external Tritonal explosion confirms this very important principle of
blast effects. The six-inch-thick concrete wall panels on the first
floor were demolished by the air blast, though the reinforcing steel
bars were for the most part left in place. The 14-inch columns
remained unaffected either by the blast pressure wave or the stresses
produced by the pull of the reinforcing steel in the wall panels as
they broke up. Damage to the second floor wall panels is considerably
less than that to the first floor walls, and very little damage can be
seen to the third floor wall panels, even though there is no ceiling
to provide stability.
A detailed pressure map matrix for the entire vertical face of the ETS
was prepared for the EBES, providing a one-foot grid which gives the
maximum potential blast pressures for any given point on the face.
According to the pressure map, the vertical face in the first test
experienced a range of maximum blast pressure from 34 psi (pounds per
square inch) to 174 psi (page 32). Maximum blast pressure on the
six-inch-thick wall panels for the first floor ranged from 74 psi to
174 psi. Wall panels on the second floor had a maximum blast pressure
ranging from 53 psi to 141 psi. The third-floor panels had blast
pressures of 34 psi to 84 psi, yet experienced no damage even though a
significant portion of the panels was subjected to pressures exceeding
the 70 psi yield factor for the six-inch-thick walls.
Computing the blast pressure for the Ryder truck’s estimated
4,800-pound ANFO bomb, the EBES determines that the radius from the
center of the device that would manifest a pressure of 70 psi or more
would be 42.37 feet. “It can therefore be expected,”
explains the study, “that within a radius of 42.37 feet from the
center of the explosive, any six-inch reinforced concrete panel
positioned so as to have a major face perpendicular or nearly
perpendicular to the travel path of the blast pressure wave from the
explosion would be damaged.” The study notes that the floor
panels in the Murrah Building were of the same thickness as the ETS
panels and, starting with the third floor, had a similar positional
relationship to the device as the panels in the Eglin test.
Accordingly, the EBES found: “A limited area of the third and
fourth floors of the Murrah Federal Building immediately adjacent to
the position of the Ryder truck would be affected. On the third floor
a roughly circular shape extending into the building and approximately
40 feet down the north face of the building from the center point of
the explosive, which was located some 14.5 feet north of the north
face of the building. This circular area contained approximately 1,250
square feet of six-inch panel.... The fourth floor panel that
experienced 70 psi and above was limited to a roughly circular-shaped
pattern of approximately 400 square feet.”
The conclusions of the Eglin Blast Effects Study are compelling and
carry stunning implications. With the ETS having significantly less
integral strength than the Murrah Building, the EBES conclusions have
a built-in margin of error that, if anything, overstate the extent of
damage to be expected at the Murrah Building. Moreover, the
computations for the Ryder truck bomb also are overly generous.
“Because ANFO is also a low-energy explosive (approximately 30%
that of TNT) and due to the inherent inefficiency of eight barrels
forming the explosive assembly [according to the government’s
estimates], it is doubtful that the device produced blast pressures
close to the calculated maximum potential blast pressure,” the
study asserts. “This being the case, it is doubtful that the
radius of damage even approached the 42.37 foot range as calculated
herein.”
Finally, the EBES concludes:
Due to these conditions, it is impossible to ascribe the damage
that occurred on April 19, 1995 to a single truck bomb containing
4,800 lbs. of ANFO. In fact, the maximum predicted damage to the
floor panels of the Murrah Federal Building is equal to
approximately 1% of the total floor area of the building.
Furthermore, due to the lack of symmetrical damage pattern at the
Murrah Building, it would be inconsistent with the results of the
ETS test [number] one to state that all of the damage to the Murrah
Building is the result of the truck bomb.
The damage to the Murrah Federal Building is consistent with damage
resulting from mechanically coupled devices placed locally within
the structure....
It must be concluded that the damage at the Murrah Federal Building
is not the result of the truck bomb itself, but rather due to other
factors such as locally placed charges within the building
itself.... The procedures used to cause the damage to the Murrah
Building are therefore more involved and complex than simply
parking a truck and leaving....
Mike Smith, a civil engineer in Cartersville, Georgia commissioned to
review the Eglin Blast Effects Study, states:
The results of the Blast Effect Test One on the Eglin Test Structure
present strong evidence that a single Ammonium Nitrate and Fuel Oil
device of approximately 4800 lbs. placed inside a truck could not have
caused the damage to the Murrah federal Building experienced on April
19, 1995. Even assuming that the building had structural deficiencies
and that the ANFO device was constructed with racing fuel, the
air-coupled blast produced from this 4800 lb. device would not have
damaged the columns and beams of the Murrah Building enough to produce
a catastrophic failure.
Robert Frias, president of Frias Engineering of Arlington, Texas,
after examining the EBES, concluded: “The Murrah Building would
still be standing and the upper floors would be intact had the truck
loaded with explosives been the only culprit.” Moreover, Frias, a
practicing engineer for over 40 years and a registered engineer in
Texas, New Mexico, and Louisiana, stated: “Explosives had to have
been placed near, or on, the structural columns inside the building to
cause the collapse that occurred to the Murrah Building.”
Likewise, Alvin Norberg, a licensed professional engineer in Auburn,
California with over 50 years of engineering experience on over 5,000
construction projects, writes that evidence from the ETS data
“verifies that the severe structural damage to the Murrah
Building was not caused by a truck bomb outside the building,”
and that “the collapse of the Murrah Federal Building was the
result of ‘mechanically coupled devices’ (bombs) placed
locally within the structure adjacent to the critical columns.”
Kenneth Gow of Whittier, California, with over one-half century of
engineering experience in the aerospace industry, writes in his
evaluation of the EBES: “The Eglin Test Structure report ...
further reinforces the conclusion that a substantial portion of the
Murrah Building damage was by internal explosions.”
The full EBES report is available for $25.00 postpaid from The New
American, P.O. Box 8040, Appleton, WI 54913.
