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- To: seaint(--nospam--at)seaint.org
- From: Abolhassan Astaneh <astaneh(--nospam--at)ce.berkeley.edu>
- Date: Sat, 24 Feb 2007 19:27:28 -0800
Dear Mr. Itsekson:Since I am one of the authors of the Deep Column Steel TIPS report that you have referred to in your e-mail, I felt to provide you with following comment hoping them to be of some help: 1. Based on available research results moment frames with deep columns (W24, 27, ..) appear to be as good a frame as typical frames with W14. After publication of our Steel TIPS, a program of cyclic testing was undertaken at Lehigh Universiy (Prof. Ricles et al) and the tests confirmed similar results as we had found in the analysis. Lehigh researchers have an excellent report on this a AISC web site: http://www.aisc.org/Template.cfm?Section=Technical_Answers&template=/ContentManagement/ContentDisplay.cfm&ContentID=26333
The report has a chapter on design as well.2. As for using any deep column moment frame in your retrodi, you need to make sure there is good connection of top flange of girders to the floor as ell as bracing the bottom flange at the end pont of plastic hinge zone to prevent lateral out-of-plane movement of buckled bottom flange which can result in generating torque on the deep columns. 3. As for using column tree moment frame system, I don't see any reason for no using it. For you case of retrofit, column trees shop-welded and field -bolted migh b quite fit. In fact if you design the splice of the column tree to be the place where plastic hinge forms and use hunches at the bottom flange girder to column connections, you can ensure that the column tree girder brances that are shop-welded to the column will remain elastic under seismic loads and the inelasticity will all come from yielding of column tree splices under rotation. The location of column-tree splices ned to be brace (top and bottom flanges) to prevent out-of-plane movements of splices specially if deep columns are sued. If you have further questions that I can help, please let me know and I will be happy to send a sketch of how column tree can be used here to your e-mail address directly as attachmnt.
Best wishes. Hassan Astaneh, Ph.D., P.E., Professor , UC-Berkeley ================== From: "Alexander \(Sasha\) Itsekson" <sasha(--nospam--at)enginious-structures.com> To: <seaint(--nospam--at)seaint.org> This is a multi-part message in MIME format. ------_=_NextPart_001_01C7577C.E7D127A1 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Dear fellow engineers, I am working on the seismic upgrade o the soft story wood building. It is fairly large 130x130 three story, 100 year wood framed building. There are two elevations of open fronts on the West and North sides of the buildings that we are bracing with 2 bays of moment frames. The owner did not want to use braced frames and even with grade beam fixing the bottom of the columns we are ending up with pretty hefty W27 sections for beams and columns. Affecting more stores by adding more bays is not feasible. In the past when we had to use anything bigger than W14 (I think that biggest we used was a W18 column) we specified Ordinary moment frame per FEMA or intermediate moment frames per CBC with all the special detailing around backup bars and access holes. Here are my questions: 1. Would that still applicable when using much bigger sections such as W27? 2. I am not up on all the recent research on steel moment frames, but can we still use the rigid Column Tree design as described for example in Structural Steel Educational Council Steel Tips http://www.steeltips.org/steeltips/index.php - as of 04.1997? Thank you very much, Alexander (Sasha) Itsekson, SE Enginious Structures, Inc. Oakland, CA 510.601.1646 www.Enginious-Structures.com <http://www.enginious-structures.com/>=20 ******* ****** ******* ******** ******* ******* ******* *** * 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 ******* ****** ****** ****** ******* ****** ****** ********
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