The Oklahoma City Bombing

The Eglin Blast Effects Study.


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.






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                       OKC Bombing: Forensic Evidence
                                      
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                       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.
   





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