Session 2 of "Lifting the fog: the scientific method applied to the world trade center disaster" - a one day conference held on November 11, 2006 at the University of California Berkeley Campus. Information about the conference is at LiftingTheFog.org.
What can be learned from analysis of the physical features of the total destruction of the World Trade Center Twin Towers and Building 7? Are there natural processes that could explain these features? Presenter is Steven Jones, Ph.D., former (recently retired) Professor of Physics at Brigham Young University in Provo, Utah, and author of numerous peer-reviewed research papers, including Why Indeed Did the World Trade Center Buildings Completely Collapse?
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Reports of Controlled Demolition, Molten Steel, Thermite, Etc.
Many people interpreted the loud sounds and debris being projected out sideways during the Tower collapses as an indication that explosives were used to demolish the buildings. Most of these 'explosive' sounds, heard during the collapses were heard after the collapses began. In order for an explosion to cause a collapse it would have to occur before the collapse. The exterior walls can be seen bending and buckling inward in the videos of both Towers long before any sounds or ground vibrations occurred. In Tower 2, the exterior columns in the east wall were photographed bowing inward up to 10 inches, 18 minutes after the plane's impact. That's 38 minutes before the global collapse began. To be technical, you could say that Tower 2's collapse began slowly, with possibly some noise or impact sounds from falling floors, about 38 minutes earlier than the official collapse time. The explosive sounds and expanding dust clouds occurred just after the east wall buckled inward and started the collapse, and not before the buckling, as would have happened with controlled demolition.
When the south wall of Tower 1 was photographed it was bowing inward up to 55 inches on floors 95 to 101, about six minutes before these columns were seen buckling inward. In the North Tower "thunder" sounds were heard when some floors apparently collapsed on the south side 12 to 14 seconds before the top of the building was seen to tilt southward and begin falling as a unit starting the global collapse. Since each section of floor on the long-span side weighed about 500 tons, I would explore these 'explosive' sounds in Tower 1 as evidence of a floor or floors detaching and impacting the floors below on the south side which most probably accelerated south wall failure. I believe all the supposed 'explosive' sounds can be explained by the impacts made by the collapsing buildings after the columns were pulled in and buckled by the bowing and sagging floors and when the floors themselves began impacting the floors below. The boom, boom, boom, boom, boom repetitive 'explosive' sounds reported by firefighters running as Tower 2 was coming down were most likely caused by the sequential collision of impacting floors after the top of the building began falling. The great quantity of air on each floor being compressed in a fraction of a second by great weight and momentum would propel air, smoke, and any concrete dust and debris outward at great velocity.
Initial Collapse Cause
It is clear from the computer studies that the heat from the fires caused differential expansion of the steel parts in the long span, floor trusses with the resulting thermal bowing in some floors directly exerting pull-in forces on the exterior columns or this thermal bowing could have detached a floor which would have impacted the floor below destroying composite action by separating the concrete slab from the trusses and inducing strong tensile (suspension) forces in the double weighted floor. In other floors thermal expansion of the floor against the columns compressed the trusses which along with shear forces within the trusses that buckled the diagonal struts collapsing the trusses which went into suspension (catenary action) and this also helped pull-in and eventually buckle the exterior column walls. Differential thermal expansion of the concrete and steel has also been shown by NIST to disconnect the knuckles from the concrete slab causing loss of composite behavior in the floors. All these adverse floor truss effects were caused by steel expansion which begins immediately as the steel is heated. Bowing and buckling can happen at low temperatures (400 C to 500 C) even before the steel would have weakened excessively from higher temperatures. Thermal contraction caused by cooling of the sagging trusses after the fire burns out can cause strong pull-in forces on the exterior columns due to the contraction of the steel trusses. Once the exterior columns buckling spread, along an entire wall removing support on one face, the towers began to tilt and the buckling spread around the towers exterior and into the core and with all the columns buckled the leaning top sections of the tower began to fall straight down. Although the North tower antenna appeared from some northern angles to have fallen straight down it actually tilted to the south because the south wall buckled first and the cantilevered top building section pulled the core over to the south. The South Tower's top tilted to the east because its east wall buckled first. With the tower top tilting all the columns were out of alignment. Once the core columns got out of plumb, there would have been little resistance to their buckling at the weak splices. With the incredible weight of the top of the buildings gaining momentum, like a heavy wedge or sledge all it had to do was break the welded, and single bolt connections holding the floors to the columns. This coupled with the fact that the falling top section’s momentum increases as the square of the number of floors impacted as the floors were detached and added to the weight of the descending top. There would have been little resistance to slow the top section's acceleration to the ground. Because this acceleration due to gravity increased the speed and momentum of the collapsing floors and building top, the impacts would have been increasingly violent as shown on the seismic graphs; increasing amplitude until maximum when the mass of accumulated floors hit bedrock seven stories into the cellar.
In order for a column to support the loads it has to be plumb and in line with the columns above and below. The fact is that columns have to be axially (in line and centered) aligned to support the weight of the building above. If they get out of alignment by 10 to 20 degrees they buckle and can no longer support the weight. The buildings collapsed because the floors first caved in from restrained thermal expansion and from thermal bowing or delamination of the slab and bar joists affecting floor truss stability. The sagging floor trusses pulled in the 59 columns in one exterior wall and they eventually buckled removing support on one side. Once the buildings started to tip over from loss of column support on that side, the tremendous excess eccentric weight began buckling all the columns across the building. Once the tilted building's tops began descending they hit the floors or columns at eccentric angles which easily detached the floors and buckled the columns. In order for the lower building section to offer any meaningful resistance to the falling building top the columns would have had to hit each other exactly in line and plumb and this was impossible with the top of the building leaning causing eccentric angles of impact. Once the top building section began tilting the columns on the side that originally buckled did not line up at all. These columns would have been hitting the floors and would have easily detached or buckled them. After the east wall buckled in Tower 2 the adjacent perimeter wall columns buckled from overloads and the columns on the opposite west side of the building, which acted as a hinge would still be bearing on each other but at an eccentric angle which means they also would have also eventually buckled as the top tilted. These columns along with some of the core columns as they buckled are probably what kicked the bottom of the top building section to the west as reported by NIST. With all the columns across the building buckled the top section began descending at an angle to the building section below. None of the columns would have been axially lined up. As the columns collided they would have hit each other at eccentric angles and easily dislodged, disconnected or buckled each other. Because of the weight of the accumulating collapsing floors, there was a release of incredible potential energy changing to kinetic energy and building momentum as the accumulating chaotic mass of debris accelerated into the cellars.
There have been some engineering analyses about the impacting floors slowing down the collapse so that the time to collapse should have been much longer than 'free fall' times of an object dropped from the towers tops. Since the Tower's outer wall columns, especially in Tower 1, pealed out like a banana, they may have been able to break the connections to the floors ahead of the floors being impacted? In other words, with the weight of the wall columns pealing outward from the vertical along with the added horizontal forces of impacting floors projecting debris outwards onto these columns; these columns, while leaning out, might have been able to break the wall-to-floor connections ahead of the level of impacting floors? If this is possible than I believe that the connection failures could have traveled down the sides of the buildings at a speed faster than free fall times. This might explain the rapid collapses especially in Tower 1. The wall-to-floor connection failures could have traveled down the building sides faster than 'free fall' times and in effect started the floors falling before they were impacted by the accumulating mass of impacted floors above. The heavy exterior wall columns in the 1500 foot high buildings while pealing off could project the column sections outwards a great distance. This distance (500 feet) was proposed as only being made possible by explosive forces. I disagree. If a wall is strong enough and doesn’t break up as it falls outward it can fall out flat to a distance equal to its height. The Tower walls, however, did break at the weak splices as they fell.
Much has been made of the fact that NIST only analyzed the events up to the point where the Towers were poised to collapse before runaway collapse began and failed to pursue the remaining collapse. This was largely because after collapse began the chaotic impacts of the floors, walls and columns colliding could not possibly be analyzed accurately with even the strongest computers. As it was, it was a severe strain on computer capabilities to analyze the mechanism of collapse up to the point of runaway disintegration.
The compression of air in the elevator and air-conditioning shafts by the collapsing upper building section and floors, would project air, smoke, and dust down these shafts and out of the air intake or discharge openings on the lower mechanical equipment floors in the exterior walls. This accounts for the plumes of smoke seen projecting outwards from the buildings well below the collapsing floors. There were quite extensive vertical HVAC shafts built into the building. These shafts are connected to air conditioning exhaust and intake ducts open to the exterior on the mechanical floors. Collapse of these shafts would force the dust and smoke out these HVAC openings in the side of the building. The lightweight aluminum cladding's breaking free from the buckling columns also would have been propelled outward a great distance by this expanding cloud of air and dust. This would account for huge dust clouds and pieces of aluminum seen projected outwards from the upper sections of the collapsing buildings. The light reflected off these aluminum pieces at the north wall of Tower 2 would be interpreted as flashes from explosive 'squibs'. The flashes below the buckling east wall may have been from the aluminum cladding breaking free from the lower columns as they expanded after being unloaded of axial weight by the buckling of the wall above and their expansion breaking the connections to the cladding. Also explosives leave characteristic tears and fractures in steel, and such indications were not found anywhere in the debris pile.
After any fire in which a building collapses, there often remain deep seated, pockets of fire deep within the rubble pile These pockets of fire sometimes cannot be reached by water streams because of their being covered by debris. Air is sometimes drawn up from the bottom of the pile and feeds these inaccessible fires with air. These fires can last for days and the heat can become intense and can heat any steel in proximity of the fire until the steel is glowing red or orange yellow hot. These pockets of fire are common at burning building collapses and in no way evidence that that explosives or thermite were used to demolish the buildings. These fires are similar to blacksmith fires where air is blown into the charcoals by a bellows to raise the temperature of the fire to heat a piece of steel or iron. The blacksmith can tell how hot the steel is by its color and can tell when the steel is soft enough to work it with a hammer. These deep seated fires often have to be dug out by hand tools, back hoes or grapplers in order to expose the burning material for extinguishment. It is common to hold off hitting the fire with water until it is fully exposed in order to prevent the great amount of steam that would be created from obscuring the work area until the fire is fully exposed and can be extinguished. This is what is happening in the picture of a grappler pulling out a piece of glowing hot steel from the debris pile so often described as molten steel. Such fires are incapable of melting steel unless they are supplied with pure oxygen.
Much has been made of the presence of molten metal in the debris pile after the collapse. Presumably this molten metal was somehow thought to be connected to explosions or thermite charges, but there were Uninterrupted Power Supply (UPS) battery rooms on some floors of the Towers and Building 7. These battery rooms supplied continuous battery power to computers if the electricity failed for any reason. These batteries contained tons of lead which melts at low temperatures [327 C (621 F)]. The heat from the fires in the debris pile could easily have melted this lead or the aluminum from the plane which were probably the metals that were seen flowing through the pile. NIST reported UPS in the 13th floor of Building 7 and the 81st floor of Tower 2. There were also quantities of lead, tin, silver and gold used in the computer circuit boards.
Additionally the EPA reported over 400 different chemicals in the dust and debris. These chemicals could easily be assembled conceptually to propose any type of chemical reaction imaginable including thermite reactions. In addition thermite reactions are rapid and wouldn't last the hours or days at which times the molten metal was observed. Thermite is hard to control and can’t be held against the columns because it would burn down through any material used to support it against the columns.
\Pure oxygen is used in oxyacetylene torches to actually ignite burn and melt the steel when cutting. These torches were used to help clear the debris pile during search and recovery operations. A slag of melted and re-solidified steel and Ferrous oxide is formed on the opposite side of the cut. This slag formation was erroneously reported to be evidence of cutter charges having been used to sever the columns. Small molten pieces of glowing steel cool into spheres as they fly out from the cut.
About the concrete destruction into dust; F.R. Greening did a paper called Energy Transfer in the WTC Collapse in which he says "the energy required to crush concrete to 100 μm particles is 1.9 × 1011 J, which is well within the crushing capacity of the available energy. Hence it is theoretically possible for the WTC collapse events to have crushed more than 90 % of the floor concrete to particles well within the observed particle size range." http://nistreview.org/WTC-REPORT-GREENING.pdf I would also investigate the possibility that the concrete was sub par due to freezing during curing or too much air or water having been added during construction.
Do you think the architect or engineers who built the Towers would want to admit the deficiencies in design, fireproofing and other construction weaknesses after their buildings collapsed? Do you think they will get any other jobs after 5 of their buildings collapsed from fire? (Building 5 had a serious interior multiple floor collapse due to fire.) Do you know that the Port Authority of NY, NJ didn't have to follow any building codes? The reason the columns broke at the splices was that they had serious weaknesses due to lack of reinforcing plates or even welds on most of the exterior column, bolted splices. The long span truss floors were never tested for fire resistance at their design length. Why do you think it took so long to get the plans for the buildings after they collapsed while the building engineers had them all along? I would think the architects and engineers for 9/11 truth would be accepting any excuse to divert attention from themselves even the wild idea that explosives or thermite was involved.
About the eye witnesses; there are many reasons that loud sounds can be produced at a fire. Most of the people in tower 2 did not know tower 1 had been struck by a plane but they heard the explosion and felt the impact. There can be smoke explosions particularly in fires that have a flammable liquid involved. There were fuel explosions in the elevator shafts. Most of the people in tower 1 did not know that tower 2 had collapsed but they all heard the noises and even felt the rush of air up the stairs. There could have been floor detachments impacting the floors below and producing loud sounds before any general collapse began. . Explosives produce loud distinctive pressure waves that can leave people deaf of blow out eardrums. This kind of sharp piercing crack was not heard. The windows broken out and marble wall panels detached on the interior of the first floor lobby were probably because of torque forces experienced on the lower floor columns from the plane impacts many floors above. The reports of "explosions" in the cellars were also probably from such column or floor displacements or from jet fuel ignitions in the elevator shafts. If you stick a stick into the ground and hit it with another stick most of the deformation will be in the ground around the bottom of the stick. There were reports of split walls and ceiling collapses on many floors after the planes hit. The one elevator shaft that extended into the cellars had a fuel explosion from the jet fuel spilling down the shaft.
In conclusion I think all the reports of controlled demolition can be explained by sounds or sights produced by the plane impacts and jet fuel and air explosions; the sounds of the Towers collapse, - remember most of the people in Tower 1 did not know Tower 2 had collapsed and attributed the sounds of that collapse to be happening in the building they were in. When the interior of building 7 collapsed it would have produced explosive sounds before the exterior walls began collapsing.
Arthur Scheuerman, Retired Battalion Chief, FDNY
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