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Fwd: Article on "Bulb Tees" in March 1997 Civil Engineering Magazine[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: Fwd: Article on "Bulb Tees" in March 1997 Civil Engineering Magazine
- From: rlewis(--nospam--at)techteam.org (Richard Lewis)
- Date: 05 Aug 1997 18:00:39 GMT
The article is entitled"Bulb-Tees Make More Efficient Long-Span Bridges" by Leo Spaans, P.E. or Janssen & Spaans Engineering, Inc., Indianapolis. It has intrigued us here in our firm, because it seems to make claims for the bulb-tee girder that, on the face of it, are hard to understand. For example: 1) Janssen claims that "bulb-tees redistribute girder forces more efficiently" than other concrete I-beam configurations. However, as far as we can determine, the live-load distribution factors for bulb-tees are exactly the same as those for other concrete I-beams. Is THIS the redistribution of girder forces that Janssen refers to, or does he simply mean that the greater section properties allow it to carry more moment? 2) One of the case studies that Janssen mentions refers to a bridge design for Bartholomew Co., Indiana. The bridge as originally designed required 18 spans of 89 ft., with five AASHTO Type IV girders each span. The redesign using bulb-tees yielded 16-106 ft. spans with three bulb-tee girders each. However, in OUR experience, AASHTO Type IVs are regularly used up to about 120 ft. spans. It looked to us as though Janssen were touting the efficacy of the bulb-tee over a very UNeconomical AASHTO girder design. 3) This impression was further exacerbated by the fact that the redesign on the afforementioned project utilized 5,000 psi deck concrete with 60 ksi reinforcement, as opposed to the 3,000 psi/40 ksi of the original design. I have been in this business for only 15 years, and my colleague for 30. In that time, NEITHER of us has EVER used 40 ksi steel. Once again, it looks like Janssen was merely dragging an outmoded design into the latter half of the twentieth century! In summary, much of what Janssen touts regarding the bulb-tee girder is undoubtedly significant. But I would appreciate answers to these questions before I would feel confident in the data, enough to further consider utilizing them in our design. Although Janssen refers to the inherent conservatism of state DOTs, the fact is that considerable standardization of the bulb-tee configuration must occur before the economies of scale can work to make them viable as a routinely-specified structural member. N.B.: If anyone has an email address for Mr. Janssen, I'd love to send this to him, and get his response directly. --- Internet Message Header Follows --- Received: from server1.seaoc.org (bqe.com [220.127.116.11]) by host1.texramp.net (8.8.5/8.8.5) with SMTP id UAA18211 for <rlewis(--nospam--at)techteam.org>; Wed, 26 Mar 1997 20:21:25 -0600 (CST) Received: from centurion.flash.net by server1.seaoc.org (NTList 3.02.10) id ra011119; Wed, 26 Mar 1997 18:10:10 -0800 Received: from poly.flash.net (hsh13-86.flash.net [18.104.22.168]) by flash.net (8.8.5/8.7.5) with SMTP id UAA18413; Wed, 26 Mar 1997 20:08:15 -0600 (CST) From: poly(--nospam--at)flash.net (Bill Polhemus) Newsgroups: SEAOC.Mailing.List To: seaoc(--nospam--at)seaoc.org cc: trans(--nospam--at)insync.net Subject: Article on "Bulb Tees" in March 1997 Civil Engineering Magazine Date: Wed, 26 Mar 1997 19:47:30 -0600 Organization: Chez Polhemus, Katy, Texas, USA Reply-To: seaoc(--nospam--at)seaoc.org Message-ID: <yGdOzQQU/wrW090yn(--nospam--at)flash.net> Lines: 44 Error-To: seaoc-ad(--nospam--at)seaoc.org X-Loop: seaoc(--nospam--at)seaoc.org X-Info: [SEAOC] Owner: seaoc-ad(--nospam--at)seaoc.org X-POP3-Rcpt: seaoc-ad(--nospam--at)seaoc.org X-Sender: seaoc-ad(--nospam--at)seaoc.org Precedence: list X-ListMember: rlewis(--nospam--at)techteam.org [seaoc(--nospam--at)seaoc.org] __________________________________________________ Richard Lewis, P.E. Missionary TECH Team rlewis(--nospam--at)techteam.org The service mission like-minded Christian organizations may turn to for technical assistance and know-how.
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