Swedish Structural Engineer: WTC Towers Did Not Collapse from Fire

The following is from my book, “Fire in the Skyscraper”

Reports of Controlled Demolition, Bombs, Thermite, Electromagnetic Rays, etc..

Many reports 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. 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 floors 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 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 by the bowing and buckling 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 probably caused by the sequential collision of impacting floors. 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.
It is also 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 or 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 buckled the diagonal struts collapsing the trusses which went into suspension (catenary action) and helped pull-in and eventually buckle the exterior column walls. All these adverse truss effects were caused by steel expansion which begins immediately as the steel is heated. Bowing and buckling happen at low temperatures (400 C to 600 C) even before the steel would have weakened excessively from higher temperatures. Once the exterior column buckling spread along an entire wall 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 top sections of the tower began to fall straight down. Although the North tower antenna appeared from some angles to have fallen straight down it actually tilted to the south because the south wall buckled first and the cantilevered top south building section pulled the core over to the south.

The South Tower’s top tilted to the east because its east wall buckled first. 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 bolted connections holding the floors to the columns. This coupled with the fact that the falling top sections 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 the columns to support the weight they have to be plumb and in line with the columns above and below. If they get out of plumb or buckle they can no longer support the weight. The buildings collapsed because the floors buckled from restrained thermal expansion and thermal bowing affecting floor truss stability. The sagging trusses pulled in the 59 columns in one exterior wall and buckled them. Once the buildings started to tip over from loss of column support on one side the tremendous excess eccentric weight began buckling all the columns across the building. The South Tower tilted to the east and the North Tower tilted to the South. Once the tilted buildings 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 resistance to the falling building top the columns would have to hit each other exactly in line and in plumb and this was impossible with the eccentric angles of impact.

The fact is that columns have to be axially (in line and centered) aligned to support the weight of the building above. 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 south wall buckled in Tower 2 the adjacent exterior 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 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. Adding the accumulating collapsing floors and you have a release of incredible potential energy changing to kinetic energy and building momentum as the accumulating chaotic mass of debris accelerated to bedrock 7 stories 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 longer than ‘free fall’ times of an object dropped from the towers tops. I have an engineering theory that may explain this. 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; would these columns, while leaning out, be 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 could have traveled down the sides of the buildings at a speed faster than free fall times. This might help 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 builddings while pealing off could project the column sections outwards a great distance. This distance was proposed as only being made possible by explosive forces. I disagree.
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.

In addition, 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 any air intake or discharge openings on the exterior walls on the lower mechanical equipment floors. 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 on the mechanical floors. Collapse of these shafts would force the dust and smoke out these HVAC exhaust and intake 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 in the debris pile.

Much has been made of the presence of molten metal in the debris pile after the collapse. Presumably this molten metal was somehow 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 327 C (621 F). The heat form the fires in the debris pile could easily have melted this lead which was probably what was seen flowing through the pile. NIST reported UPS in the 13th floor of Building 7 and the 81st floor of Tower 2. Batteries also contain Sulfuric acid which could have attacked the steel accounting for the half consumed steel beams found in the debris pile. 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.

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.

In conclusion I think most of the reports of controlled demolition are examples of delusions experienced by “experts” who jumped to conclusions and didn’t spend enough time examining the actual evidence.

Arthur Scheuerman

Thanks for linking to my web page about WTC1. Re Arthur Scheuerman’s comments above he seems to mix up deformation due to heat, buckling and collapse of a steel structure.
Evidently heat affects steel. The weakest parts of the WTC1 structure were the horisontal floor trusses and if you heat them they will bend downwards, sag, due to their own weight (460 kgs/m² incl. cement and everything on the floor) but as they are still connected to the perimeter and wall columns this sagging will not affect the latter. The columns are still supported by the floor trusses even if bent a little. And the max sagging between the end supports at the columns cannot be very big.
The suggestion that sagging floor trusses will pull in, e.g. the south wall of WTC1 55 inches is not possible (the ‘enhanced’ photo of the wall is misleading) because the wall is too strong. Regardless, if it happens, the south wall is just deformed a little over a very large large area (with the deepest deformation 55 inch at the centre of this deformation) and it does not affect the total strength of the wall that is under very low stress (<25% yield).
NIST uses buckling of supporting structure (columns) in a very confusing way. We do not know if they mean bending and how much or twisting (no column twisted!) or crumpling up (vertical compression of the columns in folds not seen anywhere).
Just because one part of a structure deforms or buckle (how?) due to heat and its own weight does not mean that the total structure suddenly collapses, please note this Mr Scheuerman! For that, collapse, you need extra energy and this is what my paper is about. And I show that very little energy is available under extreme circumstances! Extreme circumstances = all columns fail simultaously, the WTC1 top above the initiation zone drops down free fall 3.7 m and impacts the structure to be destroyed. How much released potential energy is applied to the structure below? 170 kWh. Equivalent to 20 kgs of diesel oil.

It cannot destroy the whole WTC1.

And I show you a model test to convince yourself in my second part of the paper that it will never happen. Steel under <30% yield compression will only deform a little due to 500°C heat. No buckling (whatever that means) and no collapse.

Mr Scheuerman – you are not serious when you propose that buildings will just selfdestroy if you arrange a fire at the top, are you?

Anders Björkman

Hi

Arthur, or actually may be his buddies from jref, has been copy pasting on many sites, in fact he pasted the same on mine as yours. I’ve had an ongoing post on Suzie-Q’s blog for 6 months or so where he is commenting and now he’s commenting on Geezerpower. From what I see on the jref forums, the guys Arthur did the video with, Ronald Weick and Mark Roberts, were in correspondence with BBC on their recent debunking video.

Here’s Arthur (maybe) on my blog…G:

http://mosnas2.blogspot.com/2008/04/arthur-scheuerman-discusses-wtc7.html