Aren't virtually all columns eccentrically loaded?
Aren't virtually all columns eccentrically loaded?
(OP)
Pretty basic and general inquiry here. But don't most columns support horizontal beams that have some sort of loading, and unless the load that the beam supports is directly above the column, then the column is eccentrically loaded?
I'm visualizing the basic framework for a standard metal building. Footing-->Column-->Beam-->Purlin-->Sheet Metal Panel-->Load.
If this is correct, then if the beam on top of the columns had a symmetrical distributed load, would you simplify it to a point load in the middle of the beam and split the difference between the 2 columns?
I'm visualizing the basic framework for a standard metal building. Footing-->Column-->Beam-->Purlin-->Sheet Metal Panel-->Load.
If this is correct, then if the beam on top of the columns had a symmetrical distributed load, would you simplify it to a point load in the middle of the beam and split the difference between the 2 columns?






RE: Aren't virtually all columns eccentrically loaded?
RE: Aren't virtually all columns eccentrically loaded?
RE: Aren't virtually all columns eccentrically loaded?
As to your larger question, eccentricity comes into play when moment can be induced into the column. Consider a simply supported beam, with a pinned connection at each end. Because it's simply supported, the moment at each end of the beam will be zero. Therefore, at the point where the beam connects to the column, the only moment comes from the distance between the bearing point of the beam and the c.g. of the column - the eccentricity of the load.
On the other hand, if you have, say, a column supporting a cantilever beam, the moment at the end of the beam isn't zero, and by the laws of statics this moment will be induced in the column.
Brian C Potter, PE
http://simplesupports.wordpress.com
RE: Aren't virtually all columns eccentrically loaded?
It makes sense that a simply supported beam with pinned connections and a distributed load doesn't introduce any moment into the columns. If you look at the shear and moment diagrams, then there is no moment at the endpoints, and maximum moment in the middle.
Is this still true if the beam supports are welded instead of hinged? Does the moment diagram have the same parabolic shape as the pinned connection? It seems like it would introduce a moment into the columns. Not sure though.
RE: Aren't virtually all columns eccentrically loaded?
There is a truism that any connection can be either as long as they are designed for it. Clip angles are, or were, considered flexible up to 5/8" thick but had to be designed for the transfer of moment if thicker.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Aren't virtually all columns eccentrically loaded?
Yes. If the beam is welded to the column, you'd still get a parabolic shape for the moment, with the ends of the diagram shifted down below the "x" axis".
But,as mentioned above, the beam does, to a small extent, introduce a moment into the column even if it is simply supported. The value of the moment at the top of the column is obtained by multiplying the reaction in the beam by the distance from the centerline of the column to the to the centerline of the reaction (for example, the centerline of the row of bolts if the connection is a shear tab welded to the face of the column). In most applications the moment is trivial, but it is not something you can simply disregard in all cases.
RE: Aren't virtually all columns eccentrically loaded?
Mike McCann
MMC Engineering
RE: Aren't virtually all columns eccentrically loaded?
There is nothing standard about a standard metal building frame. They come in various configurations. So, it's pretty difficult to give a general answer or draw a conclusion that that fits all configurations. But to answer your specific question...if you have a welded connection between a column and a beam, it will introduce moment into the column. We may guide you better if you can provide a sketch for the frame you are trying to analyze.
RE: Aren't virtually all columns eccentrically loaded?
RE: Aren't virtually all columns eccentrically loaded?
Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis
http://www.engissol.com/cross-section-analysis-des...
RE: Aren't virtually all columns eccentrically loaded?