Twin Towers Fall II

While checking the spelling on the title i remembered something. The strange connection between the title and logo of the series, Twin Peaks, and Oregon License plate. They say one picture equals one thousands words so i will make this post mostly of pictures.

There are many pictures of debris of WTC. The following are from forums, could not find the original sites, so i will just put them here. (I thing things are too important for everybody and too public for any fuss about copyright).

This one taken during construction says eveyrthing on how the towers were built. These are the structural outer beams made of HSS (Hollow Structural Steel) which basically is a square cross section empty in the middle made of rolled and welded carbon steel. There are some holes though kinda big to my opinion allowing workers to insert bolts and nuts and tools to tighten them.

This is from another site showing the type of joint between vertical beams. This type of joint can take a lot of pure vertical compression load, in fact as much as the beam itself. However, if the two beams are pulled from each other or pried, like in the case of wind bending the building and elongating it at one side, the maximum load is the one the 4 bolts can take.

There are numerous pictures on the web showing bolt failure at WTC. The bolts used at WTC where high strength hardened steel that could have been severely affected by heat. Also the ones that are not affected by the heat being hardened through quenching are more brittle than normal bolts. "ASTM A325 [note the symbolism] is an ASTM International standard for heavy hex structural bolts, titled Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength. It defines mechanical properties for bolts that range from  1⁄2 to 1- 1⁄2in diameter." https://en.wikipedia.org/wiki/ASTM_A325

Heat treated. That basically means quenching followed by tempering. Quenching steel makes it harder but more brittle. In place if heated, looses some of the strength and becomes more ductile or easy to bend. The fracture of the bolt shown in this picture here is not brittle but ductile, showing some flow of the material before breaking).

If an image can say a thousand words, how about a video? Only trouble with videos is they have commentators who speak and sometimes get emotional and there is a background sound that is also highly emotional. However i will put here the link to a couple of starting point within the same video. My suggestion is not to watch more than a few seconds cause cause most if is not real information but real emotional garbage.

https://youtu.be/3S5ohCX9JI8?t=12m55s

https://youtu.be/3S5ohCX9JI8?t=14m19s

There are few pictures of the immediate post impact area of the towers. Some of them are on false conspiracy theory sites. However i need to put the pictures which are real here to explain something.

I never knew until now the outer beams were wrapped in aluminum cladding which is a health problem in itself.

This picture shows some of the beams (not cladding) broken or dislocated from their joints (bolts broken) right at the time of impact. Most of the plane made of thin aluminum sheet was actually shredded by the heavy steel beams and most of it and a part of the fuel went inside. This part of weakened structure was the starting point of collapse of the tower.

If the beams were fewer and bigger with the same total load capability the plane would have still gotten inside but the beams would have resisted. But that was not possible with this type of design where all the weight of the building was supported by continuous outer vertical beams. The beams were in the same number at the top and bottom of the building but at lower level they had put thicker beams because of accumulated weight. Fewer beams were not possible at the bottom because they probably could not find any bigger.

These two pictures show many structural beams broken right after impact at one side of the tower. Those alone would have been almost enough to make the tower tilt above this level and fall. As for the comment embedded in the picture. It was possible. It is in the picture. The plane didn't cut through the beams. The beams were bent and dislocated out of the joints more like from the pressure of the shredding of the plane. The cut circled in the image is in the soft aluminum cladding. You can see in the left side of the pictures some beams that seem dislocated by tree like the bolts were broken and the cladding on top broken on a line along the joints (of the cladding).

I think the tower structure broke at impact in the same points where it was assembled that is at the bolted joints of prefabricated components made of three beams each and three cross-plates or brackets that were again assembled by bolts.

At this point the claim "the towers were designed to withstand the impact of a jetliner" does not stand anymore. Important damage seen here right after impact may seem only superficial but these were some of the beams holding the weight of the building. Once a percentage of the beams where damaged at a location the tube design which is strong only as a whole would not behave anymore like a tube but more like pieces of metal held together by bolts.

Finally the picture of a truss that holds the floor. They were trusses connecting each beam of the outer core with a horizontal one of the inner. Once the outer beams are missing or bent, the truss that was held by only by two bolts with the beam will fall together with the concrete. If one floor falls, they will make all the others fall.

In the following picture you may see how fragile the connection between floors and structural beams are. The structural beams of the faces of the tower where not connected to each other horizontally by structural beams like in more "classic designs" making this type of tower look like a cage! If the structural vertical beams where to bend and brake like they did when they were impacted by a jetliner, they could not possibly be held together by the non-structural horizontal trusses. First consequence would be the floor will fall. Once one floor has fallen, only partially, the shock-wave of the falling massive concrete floor (not seen yet poured in this picture) hitting the concrete floor under will break enough of the bolts holding the structural beams together around that floor for the whole building to start collapsing and this again can happen only at this type of design with missing horizontal structural beams.

In a way the tower stood like a giant cage with nothing connecting the oposite sides. Only heavy concrete floors hanging loose on the opsosite sides (not yet present in the pictures). The fallen concrete floor account for the huge amounts of dust spread all around New York.

Hat trusses. Hat trusses stood on top of the building and judging by their size compared to columns they were structural. It was the only structural connection between the core and outer columns both structural preventing, well, the core not to... lean on a side!. The core was a tower within itself and could sustain a bit less than half the weight of all concrete floors. But was it a stand alone tower? It couldn't have been cause it was too thin for the height and would have swayed. Could sustain vertical but not horizontal loads. These hat trusses account for the rigidity of the whole structure and wind resistance. Also the floor trusses played a role in sway proofing the building especially the independent sway of the sides. We get to the point where non-structural elements play a role in the structural stability and this where the economy plays a part. The tower was built with half of the steel necessary for the same building designed "classically".

Sway is a well known design probelm of tall and thin structures. Allthough the calculated cross-section and material strength can withstand the vertical load they can collapse because of instability of being so thin and bend like a bow before the prying action of a beam bolted to the next one would break the bolts.

Here is described how a tower made of beams can sway and they actually all do only at a small tolerable and manageable scale. In our case without the non-structural floor trusses the very tall and thin core tower or tower within tower would have swayed at the middle pretty much like a bow under the enormous weight of the concrete and collapsed. The floor trusses where also also to controll sway of the central core.

Many people still ask themselves why the towers never fell on a side. Simply because they were too fragile to even lean especially after been severely weakened on one side.

From this picture is clearer. Fire or not tower could not have stood long after almost 1/3 of the structural beams on impact side (Number 100-200) at several floors were damaged or compromised. That is about 10% of total.

http://ws680.nist.gov/publication/get_pdf.cfm?pub_id=30059

"The core was a conventionally framed structure, albeit with massive columns, that primarily carried gravity loads (the majority of the floor system, as well as the elevators and HVAC system)"

It couldn't carry the load for the majority of the floor system cause at one end of the trusses were laying on the central core and the other on the outer "structure". So it was half. Right now it's a mystery to me where the trusses at the four corners where leaning on the other end from the outer beams.

Ok i solved that one. The trusses at corners where hanging on other trusses! (those themselves were hanging half on central core and half on outer columns, so that gives in total more load on outer). But here is one that seems of light design or the same design that seem to hold 4 others at that corner! The one with many purple dots. That beam holds several times more floor weight than others. It's easy to imagine what would happen if that one failed. Also. That truss loads the corresponding outer beam several times more then those around, breaking the whole symmetry of equally loading the outer tube.

And i think it was hanging in a damaged area of the outer beams. I think - no, i bet - that's the point where the tower started to collapse, the connection of the overloaded by design truss with the outer tube.

Yeah i just checked. The plane impacted in the area with the short trusses damaging that critical truss and at several floors at once many others on one side. At that moment the rest of the standing trusses started to bend and it was a matter of time until the floor fell. It took the accumulation of the energy of the falling of several compromised floors to start break the any others under that where structurally intact.

Either the shock wave from the impact made all the bolts of the outer beams pop or the tube was dilating a bit because of the pressure of the concrete actually exploding when hitting each other that was dilating the outer tube at each floor leaving the hanging trusses with no support or maybe a combination of both. Again the floor trusses which could play a structural role in sway proofing could not fully take a structural overload which should always taken into account during design because of earthquakes.

Could the "terrorists" know the weakest point of the floor and also steer the plane with such precision so it would hit exactly there?

One more thing. This is the kanji symbol for star.

And this one's for ninja.

And the symbol for kuji-kiri.