I was thinking only of a cantilever because the previous writer was
proposing to use K = 2.
As for your example, I often run into that on overhead cranes with
walkways. I often use the guard-rail as an auxiliary truss, if I don't
want to, or can't, cantilever off the bridge girder. The customer says
"what in H" is that HSS 8x4 or whatever top rail on the guard rail.
Fortunately, sometimes I can brace back laterally to the bottom flange
of the bridge girder at the centre or 1/3 points to reduce the
unsupported length.
Gary
Kevin Below wrote:
> Gary, does that mean that a bridge with side trusses which support the
> deck on the bottom member does not have a potential buckling problem
> of the top chords under the compression load ? Your explanation is
> logical, but I hadn't thought about it before.
> I'm thinking of a short steel footbridge I have to do soon. I was
> concerned about buckling of the top chord (which is also the hand-rail).
>
> On 3/29/07, * Gary L. Hodgson and Assoc.* <ghodgson@bellnet.ca
> <mailto:ghodgson@bellnet.ca>> wrote:
>
> Jason,
> You might look at where the load is applied on the cantilever.
> Nethercott in Britain then Galambos in the USA gave descriptions
> of the
> appropriate length factor for cantilevers. If the load is applied
> above
> or below the neutral axis determines whether the beam can buckle
> sideways. For example, I get involved with a lot of crane
> runways, e.g.
> a single monorail beam cantilever, loaded on the bottom flange,
> cannot
> buckle to the side as the vertical load is counteracting the
> tendency to
> buckle sideways. Hope this helps.
> Gary
>
>
******* ****** ******* ******** ******* ******* ******* ***
* 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
******* ****** ****** ****** ******* ****** ****** ********