Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Over or under?

[Subject Prev][Subject Next][Thread Prev][Thread Next]
First, no, it really doesn't matter whether the moment line is drawn over or
under the beam line.  It's just a preference thing, and as long as the
program is either a) specific about which direction it uses or b) allows the
user to set the direction everything is good.

> Ok, I'll ask.  What is a roof drop beam?
> Rick Burch

One example:  Start a beam at an edge column.  Cantilever it over the next
column a few feet (usually ~L/6).  Skip to columns 3 and 4.  The beam over
those columns cant's over in both directions.  Now, come back and "drop" a
beam between the cantilevers between columns 2 and 3.  Continue this to the
other edge of the building.

It probably has other names in other parts of the county/world.  It's really
nice for roof systems because it combines several advantages of simple-span
beams (easy analysis, easy-to-handle beam lengths, beams are optimized for
each bay) with those of continuous beams (lower moments and deflections,
easy beam-to-column connections).

This program is really nice because in about 5 minutes you can input a 6-bay
system (it handles from 2 to 15 bays), adjust the bay spacings and loads to
fit the job, adjust the splice points to optimize the cantilever beams, and
print out the results.  Everything is graphical and intuitive (except the
moment diagram is upside-down).  It's still a work-in-progress, but the
eventual plan is to have it size the beam, design the splices, and size the
columns and baseplates (for a 1-story building).

Jason W. Kilgore, P.E.
Leigh & O'Kane, L.L.C.
(816) 444-3144

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) 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: 
******* ****** ****** ****** ******* ****** ****** ********