Anders Björkman is a structural engineer from France who became an early member of AE911Truth. He had previously given speeches in his country to people whose children had seen footage of the Trade Towers’ destruction and were worried that buildings could collapse from the top down. He reassured these parents that this couldn’t happen and posted his presentation on his web site where it gradually developed.
Björkman became a formal critic of the “Progressive Collapse” or “Piledriver” theory promoted by Dr. Zdenek Bazant, a consultant for the National Institute of Science and Technology (NIST) in its work on 9-11. The Piledriver Theory basically says that prolonged heating weakened the support columns of a single floor which caused the upper section to crush what was below it in a chain-reaction all the way to the bottom.
Björkman explains why he vigorously disputes Bazant’s “Piledriver” idea.
“If you have a structure—anything, building blocks, Lego, or a book case, and you take the top part and drop it on the rest—because it’s the same structure—the smaller top part can never supply sufficient energy to destroy the bigger bottom—as long as it’s the same structure. If you have a solid steel ball on a lot of glass or very weak things, of course the strong one can crush the bottom part, but if the structure is the same –like the World Trade Center towers—the top part is weaker than the rest and can never crush anything below,” he said. “Fires cannot cause structural failures that make steel structures collapse from top down! It is quite basic, actually,” he said.
In his closure Bazant writes, “The discusser’s interest is appreciated. However, he presents no meaningful mechanics argument against the gravity driven progressive collapse model of our paper. His claim that “the authors’ theory is wrong” is groundless.” Bazant’s Closure:
Bazant argues that differential equations are necessary in producing a realistic model of the collapses whereas Bjorkman thinks they are unnecessary—a simple model is all that is required. Bazant’s closure also repeats his endorsement of the “Crush Down” or “Progressive Collapse” theory he originally produced in 2001. On his web site Björkman posted a comment regarding Bazant’s “closure” saying, “[Bazant’s] Closure must be regarded as the most shameful Closure in structural damage analysis history!” Björkman’s reponse to Bazant’s closure
Bazant’s theory, which Bjorkman dubbed the “Pouff Pouff Theory,” can be seen in the following graphic:
“I call it the POUFF, POUFF-theory. It was launched by the US National Institute of Standards and Technology, NIST, in its so called 911-report, where it is said that when … the release of potential energy due to downward movement of the building mass above the buckled columns (the upper part C up top) exceeded the strain energy that could be absorbed by the structure (parts A below), global collapse ensued.
The POUFF, POUFF-theory is illustrated below: The upper part C is originally carried by four parts A below. Then upper part C is given downward motion due to gravity (some supports between parts C and A are buckled) and upper part C applies, when impacting A, released potential energy on the top part A that is crushed down into rubble B – POUFF!
Then the rubble B is accelerated by the upper part C and gravity and more released potential energy is applied on the next part A that is crushed into more rubble B – another POUFF!
The crushing down will be repeated as many times as is required to crush all parts A into rubble B. Then the rubble B crushes up upper part C into more rubble B – the final POUFF!
The POUFF, POUFF-theory was in fact developed by professor Zdenek P. Bazant, F.ASCE, 2001, in “Why Did the World Trade Center Collapse? – Simple Analysis.”
My contribution is to name it POUFF, POUFF!”
Björkman is so confident in his criticism of Bazant that in March he created The Heiwa Challenge. He offers ten thousand Euros to anyone who can reproduce, within specified parameters, the progressive collapse theory on their own structures.
He notes that as of July 2010, no one has claimed the prize.