Ronald Hamburger, a structural engineer and Senior Principal at Simpson Gumperts and Heger consulting engineers in San Francisco, discussed why the Twin tower buildings collapsed, illustrating his talk with graphics, in Hollywood, Ca. today.

He was a principal author of FEMA's initial report on the collapse of the twin towers and later a key participant in the National Institute of Standards and Technology (NIST) study.

Hamburger claimed that secondary fires eventually caused the core support colums to 'sink'. He did not explain to where these concrete and steel columns, that stretched from the ground to the 110 story top of the towers, 'sank'.

He was unable to remember the number of support columns. One person in the audience stated the were 47.

He showed computer graphics of the structure of the towers, stating that the collapse was caused by buckling of 40 feet horizontal trussels [that stretched from the core colums and adjoing walls to the outside walls on each floor] and the outside walls.

He acknowledge that fuel from the jet planes could not have caused the trussels and outside walls to collapse. [He compared the jet fuel to his bar-b-q coals, which are red hot when first lit, but later have lower heat].

Hamburger claimed that secondary fires of the contents of the building suites caused the intense heat [which he said reached up to 1900 degrees farenheit in some parts of the effected floors].

He claimed the debree from the crashed planes stripped the fireproofing off the core columns, which supported 60% of the weight of the building]. The other 40 % was supported by the horizontal tressels and outside wall structure.



He also claimed that the structures of the twin towers, and that of the adjacent building # 7 [which collapsed late in the afternoon of Sept 11] were so unique that they cannot be compared to other buildings, such as the Transamerica Tower in Los Angeles in 1988, which burned for hours, or even days, but did not collapse.

He also acknowledged that investiagtion was more difficult because of debris being removed from the site, although he claimed that he examined some of the steel from the structure.

Little time was left for questions after his talk, as Hamburger claimed he had to go to another engagement. Many 911 truth critics did get in some barbs, and cited counter studies such as "Scholars for 911 Truth" www.st911.org