CONTINUOUS BEAM OR SIMPLY SUPPORTED?
CONTINUOUS BEAM OR SIMPLY SUPPORTED?
(OP)
I need to design a steel beam that is in total 80ft long.
It will be supported at each end, and at 20ft spacings by
steel columns underneath the bottom flange. I plan to put
bearing plate caps on the tops of the columns, and weld the
beam, and plate caps to the columns. My question is this:
Should this beam be treated as a simply supported beam at a
20ft span, or should it be treated as a continuous beam with
supports at every 20 ft? Also, would these supports be
considered statically as rollers, pins, or fixed connections?
Any help here would be much appreciated.
Milldude
It will be supported at each end, and at 20ft spacings by
steel columns underneath the bottom flange. I plan to put
bearing plate caps on the tops of the columns, and weld the
beam, and plate caps to the columns. My question is this:
Should this beam be treated as a simply supported beam at a
20ft span, or should it be treated as a continuous beam with
supports at every 20 ft? Also, would these supports be
considered statically as rollers, pins, or fixed connections?
Any help here would be much appreciated.
Milldude






RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
If you treat the beam as 4 separate beams, you'll be conservative, but your beam will be heavier. If it is a single piece of steel (or full penetration welded sections or moment connected sections) you can treat it as a continuous beam.
For the columns the way of reasoning is similar: if you treat the joint as pinned, you are on the safe side, otherwise you need to make a frame calculation, accounting also for column flexibility and checking columns with the end moment, and also checking the strength of the beam to column connection under moment.
prex
http://www.xcalcs.com
Online tools for structural design
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
I'm interested to know why are you spannning over the columns rather than framing into them? What type of structure is this?
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
It is not always conservative for the column to assume a pinned joint at the top. Introducing moment at the top is significant. Also, the negative moment section of the beam across the columns should be checked, even if you choose a shape based on simply supported span moments.
Model what you build, and build what you model!!!!
Curvbridger
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?
reason I am spanning over the columns rather than in to the
columns is that the axial load on the columns was at a max
of 26 289 lbs. I checked into an HSS 102x102x6.4 and it
has more than enough capacity to hold up this load. Because
of the wider dimension of the flanges of my beam (W310x45)
which is 166mm, I decided to have the beam bear above the
columns, rather than frame into it. (The reason for the beam
and columns is to provide a ledge for roof trusses that will
be supported by the beam; the other side of the trusses will
be supported by the existing structure behind my new construction.
In response to JAE, I like the idea of putting stiffener
plates in the beam above the columns. I will check it out.
I'm getting a little concerned about the introduction of
end moments at the top of my columns which has been mentioned by Ginger, Prex, and CurvBridger above. Am I to
then check the column as a beam-column with end moment and
axial load? Incidentally, the total factored load on this
beam is 1150 lb/ft.
RE: CONTINUOUS BEAM OR SIMPLY SUPPORTED?