>
> Thank you for taking the time to make your comments below. I like to
> offer the following:
>
> 1. Our findings with regard to the structure of the collapsed WTC
> towers not complying with the code is not just about these buildings
> not following a certain code, but also with regard to the fact that
> these buildings did not use , for the most part, the known and well
> tested structural systems that our codes are based upon. Specially,
> searching through the published literature as much as we could, we
> could not find other applications of these steel bearing wall systems
> and floors nor the use of their unique connections and splices. Nor we
> could find considerable amount of research data and testing on
> performance of these systems and their components in the published
> literature. There is almost no indwependent testing of critical yet
> unique systems and components of these structures.
>
> 2. As you know, code provisions have evolved over the years and
> continue to evolve through the efforts of code committees and approval
> agencies utilizing data resulting from analysis and testing,
> observations on actual behavior of these systems and components under
> the realistic service and ultimate load conditions, as well as
> collective understanding of their behavior coming from the structural
> engineering community of the known systems used in the past as well as
> any new system that has emerges. Recent examples are development of
> the new seismic code provisions for welded moment frames (a
> traditional system) and provisions for design of base-isolated
> structures and unbound braced systems (both new and innovative
> systems). In both of these new systems and all other innovative system
> in the past , when there was a major deviation from the traditional
> system, there has been extensive research and trial applications,
> mostly independent of the inventors and developers, as well as
> independent peer reviews and discussions of the structural
> performances of the systems at professional gatherings and in the
> pages of journal and conference papers and other publications which
> are publicly available. As a result of this lengthy, elaborate and
> careful process, the final code provisions are truly representing the
> best information that our profession can offer at the time of their
> adaptation to be used in design of these systems to produce safety
> level that is targeted by the codes , again based on the consensus of
> the profession, yet economical structures. Even then, when there in
> new information either from the researchers or from the actual
> performance of our structures as they go through their service life,
> we incorporate such new data into our codes, again going through the
> same lengthy but reliable process delibrations and consensus-based
> process. A recent example is the case of overhaul of almost entire
> code provisions regarding seismic design of steel welded moment frames
> after the Northridge-94 earthquake. Such was not the case for the
> uncommon structural systems and their components used in the WTC
> towers. One even wonders if applying the code provisions that are
> developed for systems that we have known and used in design of these
> unusuall and almost totally different systems of the WTC towers could
> be justified. In my humble opinion, doing so would be similar to
> someone applying the provisions that are in the code for traditional
> concentrically braced frames to design a braced frame with unbound
> braces and its components.
>
> 3. The issue of code compliance and whether or not all building
> structures, and indeed all structures, need to be designed according
> to the governing code, or certain buildings should be exempt from the
> code , as were the WTC towers, is a very important question and has
> many safety, economic, social and legal aspects and I do not feel
> qualified at all to offer an expert opinion on it. But, regardless of
> how highly I regard the owners, designers and contractors who fund,
> design and construct our structures, as a citizen who lives and works
> in these structures, I rather see that everyone follows the governing
> codes of design and construction and uses systems that are covered by
> these codes. This , in my opinion will guarantees that I am living and
> working in a building that is designed based on the consensus of the
> structural and construction engineers, past and present, instead of
> living and working in a building that the only assurance of safety I
> have is coming from only a single team of owner, designer and
> contractor which was the case for the WTC towers.
>
> 4. Point of Information: Some have called the exterior "steel bearing
> walls" of the WTC towers a 'tube system" . This seems not to be quite
> correct since the exterior steel walls did not have a framing system
> with beams and columns framing into each-other and normally connected
> to each other with moment connection as the traditional tube system
> is. The exterior walls did not have horizontal girders or vertical
> columns forming a frame. The walls consisted of steel plates, with
> penetrations for window opening where, the plates were stiffened with
> vertical 3-plate channels every 3'-3". I have seen the structural
> drawings of the World Trade Center, issued by Skilling, Helle,
> Christiansen, Robertson, Structural & Civil Engineers with Mr. Leslie
> E. Robertson's seal on them refer to the exterior walls as "bearing
> walls". After studying the structural system of the WTC towers, it
> seems to me that the structure of the WTC towers, above the 10th floor
> or so to be a steel version of the masonry bearing wall system that
> were used in buildings prior to the invention (or development?) of the
> steel skeletal framing system in late 1800's by William Le Baron
> Jenny.. some calling him the father of skyscrapers.
>
> 5. as for "flimsiness" the Oxford Dictionary online has the following
> entry:
>
>
> flimsy
>
> • *adjective* (*flimsier*, *flimsiest*) *1* weak and insubstantial.
> *2* (of clothing) light and thin. *3* (of a pretext or account) weak;
> unconvincing.
>
> • *noun* (pl. *flimsies*) Brit. *1* very thin paper. *2* a copy of a
> document, made on very thin paper.
>
> If you study the structural drawings of the WTC towers in depth, which
> I have done, you may also find the definition "1" above to be
> applicable to the exterior bearing walls of the towers in the context
> of the events of 9/11 (i.e. impact of the airplanes, entry of the
> plane almost intact inside the building delivering thousands of
> gallons of jet fuel and ensuing fire) , as you have already concluded
> for the one case that you have mentioned in your e-mail that you are
> aware of which I assume is the connection of floor joists to the
> exterior bearing walls as I discussed with you in my earlier personal
> e-mail.
>
> 6. In the aftermath of this horrible tragedy caused by 19 murderers
> and their organizers and supporters, the public and specially victims
> families were asking our profession why these buildings collapsed so
> fast and so completely and is there a lesson that we could learn to
> apply to future designs or modifications of current designs to prevent
> these murderers from using our structures to murder us?. Instead of
> having at least an open discussion on what exactly these structures
> were and why never before a steel structure that has caught fire
> collapsed so fast and so completely while trapping more than 1500
> people on floors above the fire region, a few in our profession, some
> of them or their firms directly or indirectly involved in design of
> these unusual systems, have embarked on a campaign of defending the
> design of these structures and without any analysis, declaring, in
> public as well as in the pages of publicly funded reports, to the
> effect that there was nothing wrong with these systems , again in the
> context of 9/11 events, and any building hit by an airplane, as
> happened in 9/11/01, will end up with the same fate. More unfortunate
> is that others in the profession, quite knowledgeable and honorable
> individuals, relying on the trust that naturally we all have in each
> other in our profession, blindly and again without any facts in their
> hands, have continued and still continue defending these structures
> and repeating the same line that " there was nothing wrong... " as
> evidenced by some comments in these pages and other places.
>
> 7. I like to use this opportunity and call on the Port Authority of
> New York and New Jersey as well as Mr. Leslie E. Robertson, the
> structural engineerof the record and Mr. Jon Magnusson, the CEO and
> Cahirman of the Board of the Magnusson Klemencic Associates ( the firm
> that was Skilling , Helle, Christiansen, Robertson at the time of the
> design of the WTC and designed the structures) to post the structural
> drawings of the WTC towers publicly on the Internet and allow
> structural engineers and researchers to study these structures and
> learn lessons from their performance to see if anything that is
> learned from this tragedy and performance of these towers can be used
> in their practice to protect public against future murderer or even
> against accidental airplane impact and fires. If such studies , such
> as ours, help save even a single life in the future we have done our
> moral obligation to ourselves, our profession and our fellow human beings.
>
>
> Best wishes as always and thank you again for your time.
> Hassan Astaneh, Ph.D., P.E., Professor (www.ce.berkeley.edu/~astaneh)
> Member of Professional Advisory Panel of the Skyscraper Safety
> Campaign (Sally Regenhard, Chairperson)
> (www.skyscrapersafety.org)
> ==================================
>
> From: "ASC" <ggg@bigpond.net.au>
> To: "Struct EngAssoc" <seaint@seaint.org>
> Subject: PROF ASTANEH AND STRUCTURAL DISASTERS
>
> This is a multi-part message in MIME format.
>
> ------=_NextPart_000_0077_01C7FBB5.F359CEF0
> Content-Type: multipart/alternative;
> boundary="----=_NextPart_001_0078_01C7FBB5.F359CEF0"
>
>
> ------=_NextPart_001_0078_01C7FBB5.F359CEF0
> Content-Type: text/plain;
> charset="Windows-1252"
> Content-Transfer-Encoding: quoted-printable
>
> BlankWith respect to WTC he had a point:
> If the building were constructed according to the Code, it would have
> a reserve of strength, or, in other words, would=20
> not be so flimsy.
>
> Of course, his criticism of the official investigators of the collapse
> was too strongly worded. But, if he is right, then someone who knows
> it too,
> but doesn't mention it in the report, is wrong, isn't he?
>
> I am more of an analyst than a designer and my familiarity with codes
> is minimal. But I am aware of at least one 'flimsiness' aspect, that
> was the most =
> likely contributing cause to WTC collapse.
>
> Sometimes circumstances work in unexpected manner. That's why we need
> a reserve of strength.
>
> As for a public vs private criticism I agree, it would be more
> professional to stick to the latter. But who would listen then?
>
>
> Sincerely, Gregory from Oz
> ====================================
>
>
>
>
>
******* ****** ******* ******** ******* ******* ******* ***
* Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
* This email was sent to you via Structural Engineers
* Association of Southern California (SEAOSC) server. To
* subscribe (no fee) or UnSubscribe, please go to:
*
*
http://www.seaint.org/sealist1.asp
*
* Questions to seaint-ad@seaint.org. Remember, any email you
* send to the list is public domain and may be re-posted
* without your permission. Make sure you visit our web
* site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********